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TULANE / Psychology / PSYC / brain and behavior study guide

brain and behavior study guide

brain and behavior study guide

Description

School: Tulane University
Department: Psychology
Course: Brain and Behavior
Term: Fall 2018
Tags: Psychology, neuroscience, neurology, neurons, brain, nervous, nervous system, and behavior
Cost: 50
Name: PSYC-3300 Brain & Behavior Exam 1 Study Guide
Description: This study guide covers the material on the first exam, which includes chapters 1-4 of the textbook.
Uploaded: 09/20/2018
37 Pages 14 Views 10 Unlocks
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PSYC 3300 Exam 1 Study Guide


What is the scientific study of nervous system?



Sterkel 1

Brain and Behavior 

Chapter 1

General Info. 

● neuroscience - the scientific study of the nervous system

● biological psychology - also called behavioral neuroscience, brain and behavior, and physiological psychology; the study of the biological bases of psychological processes and behavior

The Science of Brain and Behavior Spans Past, Present, and Future ● What defines the study of brain and behavior?

○ The brain is composed of:

■ 86 billion neurons

■ 100 thousand miles of axons

■ 10 trillion synapses

○ These elements lead to behavior such as movement, vocalization, thinking ○ The brain is part of the nervous system (CNS and PNS)

○ behavior in living organisms may be innate​ or learned

● The behavioral role of the brain was uncertain to early scholars


What defines the study of brain and behavior?



○ dualism - the notion, promoted by René Descartes, that the mind has an immaterial aspect that is distinct from the material body and brain

○ phrenology - the belief that bumps on the skull reflect enlargements of brain regions responsible for certain behavioral faculties

○ localization of function - the concept that different brain regions specialize in specific behaviors

○ Hebb’s Postulate (1949) said that the brain is affected by events that occur ■ “neurons that fire together wire together”

■ before Hebb, people thought the brain was a “black box”

● Advances in experimental methodology propel modern biological psychology ○ Present day biological psychologists may draw on several different theoretical perspectives. Here are some of the major ones:

■ Systematic description of behavior

■ Evolution of brain and behavior


Three kinds of studies probe brain-behavior relationships.



PSYC 3300 Exam 1 Study Guide

Sterkel 2

● conserved - in the context of evolution, referring to a trait passed

on from a common ancestor to two or more descendant species Don't forget about the age old question of msu cse

■ Life-span development of the brain and behavior

● ontogeny - the process by which an individual changes in the

course of its lifetime--that is, grows up and grows old

■ Biological mechanisms of behavior

● neuron - aka nerve cell, the basic unit of the nervous system

● The future of biological psychology is in interdisciplinary discovery and knowledge translation (this is the Biological Approach)

○ strong emphasis on brain function, more at a microscopic level (neurons & glia) ○ neurons and glia somehow produce diversity of behavior and experience ○ neuroplasticity - also called neural plasticity; the ability of the nervous system to change in response to experience or the environment

■ adult neurogenesis - the creation of new neurons in the brain of an adult ○ social neuroscience - a field of study that uses the tools of neuroscience to discover both the biological bases of social behavior and the effects of social circumstances on brain activity

○ evolutionary psychology - a field of study devoted to asking how natural selection has shaped behavior in humans and other animals

○ epigenetics - the study of factors that affect gene expression without making any changes in the nucleotide sequence of the gene themselves

■ gene expression - the turning on or off of specific genes

○ neuroeconomics - the study of brain mechanisms at work during economic decision making

○ consciousness - the state of awareness of one’s own existence, thoughts, emotions, and experiences

Careful Research Design Is Crucial for Brain Research ● Three kinds of studies probe brain-behavior relationships We also discuss several other topics like What are mood disorders?

○ somatic intervention - an approach to finding relations between body variables and behavioral variables that involves manipulating body structure or function and looking for resultant changes in behavior

PSYC 3300 Exam 1 Study Guide

Sterkel 3

■ independent variable - the factor that is manipulated by an

experimenter

● this is the physical alteration in this type of experiment

■ dependent variable - the factor that an experimenter measures to monitor a change in response to changes in an independent variable ● this is the behavioral effect in this type of experiment

■ control group - in research, a group of individuals that are identical to those in an experimental (or test) group in every way except that they do not receive the experimental treatment or manipulation. the

experimental group is then compared with the control group to assess the effect of the treatment

● within-participants experiment - an experiment in which the same set of individuals is compared before and after an

experimental manipulation. the experimental group thus serves as its own control group

● between-participants experiment - an experiment in which an experimental group of individuals is compared with a control

group of individuals that have been treated identically in every

way except that they haven’t received the experimental

manipulation

■ examples of somatic intervention experiments:

● administering a hormone to some animals but not others and comparing later sexual behavior of both groups

● electrically stimulating a specific brain region and measuring alterations in movement

● destroying a specific region in the brain and the subsequent changes in sleep patterns If you want to learn more check out ch 101 bu

○ behavioral intervention - the opposite approach to somatic intervention, an approach to finding relations between body variables and behavioral variables that involves intervening in the behavior of an organism and looking for resultant changes in body structure or function

■ independent variable is behavior

■ dependent variable is what’s going on in the brain/body

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Sterkel 4

■ ex: present a visual stimulus and look at how the brain responds Don't forget about the age old question of aged 260 uiuc

■ examples of behavioral intervention:

● allowing adults of each sex to interact and measuring subsequent changes in sex hormones

○ correlation - the tendency of two measures to vary in concept, such that a change in one measure is matched by a change in the other

■ positive correlation - IV and DV increase or decrease together

■ negative correlation - when IV increases, DV decreases or vice versa ■ remember correlation is not causality

■ causality - the relation of cause and effect such that we can conclude that an experimental manipulation has specifically caused an observed result

■ examples of correlation studies:

● observing the extent to which memory ability is associated with

the size of a certain brain structure

● noting that increases in a certain hormone are accompanied by

increases in aggressive behavior

● Biological psychologists use several levels of analysis

■ reductionism - the strategy of breaking a system down into increasingly smaller parts in order to understand it; try to identify levels of analysis ■ levels of analysis - the scope of experimental approaches; a scientist may try to understand behavior by monitoring molecules, nerve cells, brain regions, or social environments or using some combination of these

levels of analysis

● How does it all come together? Don't forget about the age old question of gcu loud cloud

○ Converging Evidence - multiple people get the same results

○ Scientific Inference - only missing a tad of data and make an inference; not perfect but is still used

● The Toll of Brain Disorders

○ at least 1 person in every 5 suffers from neurological or psychiatric illness ○ one in every 4 affected persons suffer from 2 or more psychiatric disorders during their lifetime

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Sterkel 5

● There are some shared characteristics between humans and other animals, and there are also some individual differences

○ not always exactly the same but definitely useful; we learned about the genetic basis of the brain from studying a worm

○ ethics is very important in animal neurological research (and ofc humans too) ○ there is controversy over whether this research is valid or ethical

Chapter 2 

Cells and Structures: The Anatomy of the Nervous System

The Nervous System Is Composed of Cells 

● neurons - also called nerve cells; the basic unit of the nervous system, each composed of receptive extensions called dendrites, an integrating cell body, a conducting axon, and a transmitting axon terminal

● glial cells - also called glia; non-neuronal brain cells that provide structural, nutritional, and other types of support to the brain

● synapse - the cellular location at which information is transmitted/communicated from a neuron to another cell

● Neuroanatomical methods

○ Golgi stain​ - only labels a small number of neurons in the brain but labels them with very intricate detail

○ Nissl stain​ - outlines cell bodies because the dyes used in it label RNA but won’t tell you difference between neuron and glial cell or won’t give you anatomical detail of the golgi stain but still important for understanding the # of cells We also discuss several other topics like craig mccarthy ohio university

○ Immunocytochemistry​ - largely based on how your immune system works ■ use antibodies to recognize certain protein sites and then secondary antibodies (sometimes fluorescent ones) that tag specific proteins

■ the guy who came up with this won a nobel prize

○ Expressions of c-fos in activated cells - can look at genetic changes after an event that are part of neural plasticity

○ HRP-filled motoneuron

■ anterograde labeling​ (from the neuron cell body out to some target)

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■ opposite of anterograde labeling = retrograde labeling​ - inject

something into a target and these molecules are taken up the axon

terminal of the neuron and are transported back to the cell body

● The neuron has four principal divisions aka functional zones:

1. Input zone - the part of a neuron that receives information from other neurons or from specialized sensory structures

a. dendrite - an extension of the cell body that receives information from other neurons; aka dendritic field

b. each neuron can make connections with approximately 10 thousand other neurons and can receive input from 10s of thousands of other

neurons

2. Integration zone - the part of a neuron right under the cell body that initiates neural electrical activity; aka axon hillock

a. cell body - also called soma; the region of a neuron that is defined by the presence of the cell nucleus

b. all the info that’s coming into the dendritic field is integrated in this area; action potential

3. Conduction zone - the part of a neuron--the axon--over which the action potential is actively propagated

a. axon - also called nerve fiber; a single extension from the nerve cell that carries action potentials from the cell body toward the axon terminals b. materials constantly transported up/down the axon by axonal transport 4. Output zone - the part of a neuron at which the cell sends information to another cell

a. axon terminals - also called synaptic bouton; the end of an axon or axon collateral, which forms a synapse with a neuron or other target cell

b. where neurotransmitter is released; when the action potential reaches a threshold a neurotransmitter is released onto all of the neurons

connected to this neuron

● There are 3 general types of neurons (classified according to general shapes, each specialized for a particular kind of information processing):

○ also, Different shapes of neurons reflect their function (see examples below) ○ multipolar neuron - a nerve cell that has many dendrites and a single axon

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■ the axon can split and form axon collaterals

■ most common type

■ ex: motor neurons - very large neurons that act to stimulate muscles ○ bipolar neuron - a nerve cell that has a single dendrite at one end and a single axon at the other end

■ ex: interneurons - interact locally in specific parts of the brain and act to control and toggle local activity

○ unipolar neuron - also called monopolar neuron; a nerve cell with a single branch that leaves the cell body and then extends in two directions; one end is the input zone, and the other end is the output zone

■ ex: sensory neuron - a nerve cell that is directly affected by changes in the environment, such as light, odor, or touch

● Information is passed across synapses

○ Presynaptic neuron - neuron that is transmitting information to the target neuron

○ Postsynaptic neuron - the neuron that is receiving information from and responds to the information from the presynaptic neuron(s)

● Key features of the synapse

○ presynaptic terminal (button)

○ Mitochondrion

○ Synaptic vesicles - small spheres that contain the neurotransmitter which will be released from the synaptic membrane

○ Presynaptic membrane - on the axon terminal, the part of the cellular membrane that releases neurotransmitters

○ Neurotransmitter molecules - released when electrical activity goes through all the zones and reaches action potential; specialized proteins, often embedded in the cell membrane, that selectively sense and react to molecules of a corresponding neurotransmitter or hormone

○ Synaptic Cleft - space between both membranes, a lot goes on here ○ neurotransmitter receptor - also called simply receptor; a specialized protein, often embedded in the cell membrane, that selectively senses and reacts to molecules of a corresponding neurotransmitter or hormone

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○ Postsynaptic membrane - contains receptors that recognize the released neurotransmitters from the presynaptic cell (is on the dendrite of the target neuron)

○ Dendritic spine - typically receives input from a single axon at the synapse; serve as a storage site for synaptic strength and help transmit electrical signals to the neuron's cell body 

● The axon integrates and then transmits information

○ axon hillock - the cone-shaped area on the cell body from which the axon originates

○ innervate - to provide neural input to

○ axon collaterals - a branch of an axon

○ axonal transport - transportation of materials from neuronal cell body toward the axon terminals, and from the axon terminals back toward the cell body ● Glial Cells protect and assist neurons 

○ Some glial cells produce myelin - the fatty insulation around an axon; this sheath boosts the speed at which nerve impulses are conducted 

○ oligodendrocytes - a type of glial cell that produce myelin which then wraps itself around the axon several times 

○ Schwann cell - type of glial cell that forms myelin in peripheral nervous system ○ Nodes of Ranvier - unmyelinated gaps between successive segments of the myelin sheath where the axon membrane is exposed 

○ without enough myelin on motor neurons we get motor deficits (myelin is very important) 

○ Astrocytes - starshaped glial cell with many extensions running in all directions

■ help form the blood-brain barrier, form connections with capillaries that are carrying blood through the brain and with neurons themselves; provides energy to the neurons 

■ acts to scavenge neurotransmitters, can re-release neurotransmitters during certain events 

○ Microglia - little defenders of the brain; remove cellular debris from hurt cells ■ in cases of inflammation or damage etc, the microglia engulf and destroy foreign entities in the brain

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■ edema - the swelling of tissue in response to injury

Neuroanatomical Terminology 

● Medial - towards the middle

● Lateral - towards the side

● Ipsilateral - same side

● Contralateral - opposite side

● Superior - above

● Inferior - below

● Anterior or rostral - head end

● Posterior or caudal - tail end

● Proximal - near the center

● Distal - toward the periphery

● Dorsal - toward the back

● Ventral - toward the belly, or front

● Planes of brain orientation

○ Horizontal plane- divides the brain into upper and lower regions

○ Sagittal plane - along the vertical midline of brain, divides into left and right pieces, dorsal and ventral pieces

○ Coronal plane - divides brain into anterior and posterior portions (think of cutting through the ears down that way

○ your nose is anterior and medial

○ the top of a dog’s head is dorsal

● Terminology to orient to nervous system

○ To describe the flow of information

■ afferent - carries information into a region of interest

■ efferent - carries information away from a region of interest

Divisions of the Nervous System 

● Review: nerve - a collection of axons bundled together outside of the central nervous system

● motor nerve - a nerve that transmits information from the central nervous system to the muscles and glands

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● sensory nerve - a nerve that conveys information from the body to the central nervous system

● There are 2 major components of the nervous system

○ Central Nervous System (brain and spinal cord)

■ tract - a bundle of axons found within the central nervous system ■ groups of cell bodies are called nuclei

■ myelin made by oligodendrocytes

○ Peripheral Nervous System (somatic and autonomic nervous systems) ■ bundles of axons are called nerves

■ groups of cell bodies are called ganglia

■ myelin made by Schwann cells

■ afferent neurons -> sensory neurons that carry nerve impulses from sensory stimuli towards the brain

■ efferent neurons -> carry neural impulses away from the brain towards muscles to cause movement

■ made up of the:

■ somatic nervous system - a part of the peripheral nervous system that supplies neural connections mostly to the skeletal muscles and sensory systems of the body; made of cranial nerves and spinal nerves

● Cranial Nerves (12 pairs of them) - innervate the head, neck, and

some organs directly to and from the brain see slides man

○ first group of them (purely sensory nerves)

■ Olfactory nerve - carries information from your

nose to your brain

■ Optic nerve - carries visual information from your

eyeballs into the brain

■ Vestibulocochlear nerve - hearing and balance

○ second group of them (purely motor)

■ Oculomotor - muscle that moves the eyes

■ Trochlear - another muscle that moves the eyes

■ Abducens - another muscle that moves the eyes

■ Spinal accessory - neck muscles

■ Hypoglossal - tongue muscles

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○ 3rd group: these have both motor and sensory functions ■ Trigeminal - face, sinuses, teeth, jaw muscles

■ Facial nerve - tongue, soft palate, facial muscles,

salivary glands, tear glands

■ Glossopharyngeal - taste and other mouth

sensations, throat muscles

■ Vagus - information from internal organs, internal

organ motor information

● Spinal Nerves - a set of 31 nerves that carry information to and from the spinal cord

○ each one is a group of motor fibers that come from the spinal cord to the muscle and the sensory fibres that

come from the skin to the spinal cord

○ 5 general zones named for the part of the spinal cord that they innervate:

■ cervical spinal cord - top part of neck, 8 segments

■ thoracic - referring to the 12 spinal segments

below the cervical (neck) portion of the spinal

cord, corresponding to the chest

■ lumbar - referring to the five spinal segments that

make up the upper part of the lower back

■ sacral - referring to the five spinal segments that

make up the lower part of the lower back

■ coccygeal - referring to the lowest spinal vertebra

(the coccyx, also known as the tailbone)

■ autonomic nervous system - a part of the peripheral nervous system that provides the main neural connections to glands and to smooth muscles of internal organs (have afferent and efferent nerves)

● sympathetic nervous system - the part of the autonomic nervous system that acts as the “fight or flight” system, generally

activating the body for action

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● parasympathetic nervous system - the part of the autonomic

nervous system that generally prepares the body to relax and

recuperate

Divisions of the Central Nervous System 

● The spinal cord

○ white matter - a light-colored layer of tissue, consisting mostly of the myelinated axons, that lies underneath the gray matter of the cortex; white matter mostly transmits information;ex: corpus callosum

○ gray matter - areas of the brain that are dominated by cell bodies and are devoid of myelin; gray matter mostly receives and processes information; ex: basal ganglia

● General Anatomy of the Brain

○ cerebral hemisphere - one of the two halves--right or left--of the forebrain ○ cerebral cortex - also called simply cortex; the outer covering of the cerebral hemispheres, which consists largely of nerve cell bodies and their branches ○ gyrus - a ridged or raised portion of a convoluted brain surface

○ frontal lobe - the most anterior portion of the cerebral cortex

■ precentral gyrus - the strip of frontal cortex, just in front of the central sulcus, that is crucial for motor control

■ central sulcus - a fissure that divides the frontal lobe from the parietal lobe

○ parietal lobe - the large region of cortex lying between the frontal and occipital lobes in each cerebral hemisphere

■ postcentral gyrus - the strip of parietal cortex, just behind the central sulcus, that receives somatosensory information from the entire body

○ occipital lobe - a large region of cortex that covers much of the posterior part of each cerebral hemisphere

○ temporal lobe - the large lateral region of cortex in each cerebral hemisphere; it is continuous with the parietal lobe posteriorly and separated from the frontal lobe by the Sylvian fissure

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○ olfactory bulb - an anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, provides receptors for smell

○ Brainstem: controls vital body functions

○ Sylvian fissure - also called lateral sulcus; a deep fissure that demarcates the temporal lobe

● Midline and Basal Structures of the Brain

○ The hindbrain

■ medulla - the posterior part of the hindbrain, continuous with the spinal cord

■ reticular formation - an extensive region of the brainstem, extending from the medulla through the thalamus, that is involved in sleep and arousal

■ cerebellum - a structure located at the back of the brain, dorsal to the pons, that is involved in the central regulation of movement, and in

some forms of learning

■ pons - the portion of the brainstem that connects the midbrain to the medulla

○ The midbrain has sensory and motor systems

■ tectum - the dorsal portion of the midbrain consisting of the inferior and superior colliculi

● superior colliculi - paired gray matter structures of the dorsal

midbrain that process visual information

● inferior colliculi - paired gray matter structures of the dorsal

midbrain that process auditory information

■ tegmentum - the main body of the midbrain, containing the substantia nigra, periaqueductal gray, part of the reticular formation, and multiple fiber tracts

● substantia nigra - a brainstem structure that innervates the basal ganglia and is a major source of dopaminergic projections

● periaqueductal gray - a midbrain region involved in pain

perception

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● reticular formation - an extensive region of the brainstem,

extending from the medulla through the thalamus, that is

involved in sleep and arousal

● red nucleus

○ The diencephalon - the posterior part of the fetal forebrain, which will become the thalamus and hypothalamus in the adult brain

■ thalamus - the brain regions that surround the third ventricle

● sensory relay nuclei

■ hypothalamus - part of the diencephalon, lying ventral to the thalamus ● above pituitary gland

● endocrine function

● motivated behaviors

● many nuclei

● below thalamus

● motivated behaviors (feeding, drinking, temperature regulation,

rhythms, sex behavior, sleep)

● connections with limbic system

● input to pituitary gland

○ Spinal cord and Brainstem

○ fornix - a fiber tract that extends from hippocampus to the mammillary body ○ cingulate gyrus - a strip of cortex, found in the frontal and parietal midline, that is part of the limbic system and is implicated in many cognitive functions ○ corpus callosum - the main band of axons that connects the two cerebral hemispheres

● basal ganglia - a group of forebrain nuclei, including the caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres

○ caudate nucleus - one of the basal ganglia; has a long tail

○ putamen - one of the basal ganglia

○ globus pallidus - one of the basal ganglia

● The limbic system - a loosely defined, widespread group of brain nuclei that innervate each other and form a network

● Laminae (layers) - structural​ organization of the cerebral cortex

● Columns - functional​ organization of the cerebral cortex

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Protection and Nourishment of the Nervous System ● Blood Brain Barrier

○ The brain floats within layers of membranes

■ meninges - the three protective membranes--dura mater, pia mater, and arachnoid--that surround the brain and spinal cord

● dura mater - outer meninge that surrounds brain and spinal cord

● pia mater - inner meninge that surrounds brain and spinal cord

● arachnoid - the thin covering (one of the three meninges) of the

brain that lies between the dura mater and the pia mater

■ cerebrospinal fluid (CSF) - the fluid that fills the cerebral ventricles

■ meningitis - an acute inflammation of the meninges, usually caused by a viral or bacterial infection

■ meningioma - a noninvasive tumor of the meninges

○ The brain relies on two fluids for survival

■ ventricular system - a system of fluid-filled cavities inside the brain ■ lateral ventricle - a complex C-shaped lateral portion of the ventricular system within each hemisphere of the brain

■ choroid plexus - a specialized membrane lining the ventricles that

produces cerebrospinal fluid by filtering blood

■ third ventricle - the midline ventricle that conducts cerebrospinal fluid from the lateral ventricles to the fourth ventricle

■ fourth ventricle - the passageway within the pons that receives

cerebrospinal fluid from the third ventricle and releases it to surround

the brain and spinal cord

■ cerebral arteries - the three pairs of large arteries within the skull that supply blood to the cerebral cortex

■ blood-brain barrier - the mechanisms that make the movement of

substances from blood vessels into brain cells more difficult than

exchanges in other body organs, thus affording the brain greater

protection from exposure to some substances found in the blood

○ Astrocyte feet

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■ capillaries in the brain are not leaky, have tight junctions, and are

covered with astrocyte feet

● these properties prevent materials from moving in and out easily,

and are the basis of the blood-brain barrier

○ Endothelial cells

■ capillaries in the body are leaky and have few tight junctions; materials can move in and out relatively easily

○ Small, uncharged molecules such as CO2 and O2 are able to pass through the endothelial membrane and reach the brain

○ Certain other molecules, such as amino acids, glucose, and fats, are carried across the membrane by active transport

○ Large and electrically charged molecules are unable to pass out of the capillary ● Besides CSF, the brain depends on an ample supply of oxygenated blood from the cerebral arteries

● Stroke ​is caused by the rupture or blockage of blood vessels, leading to insufficient oxygen supply

Brain-Imaging Techniques Reveal the Structure and Function of the Human Brain ● CT uses X-rays to reveal brain structure

○ computerized axial tomography (CAT or CT) - noninvasive technique for examining brain structure through computer analysis of X-ray absorption at several positions around the head

● MRI maps density to deduce brain structure with high detail

○ magnetic resonance imaging (MRI) - noninvasive brain imaging technology that uses magnetism and radio-frequency energy to create images of the gross structure of the living brain

● Functional MRI uses local changes in metabolism to identify active brain regions ○ (functional) MRI - magnetic resonance imaging that detects changes in blood flow and therefore identifies more active brain regions during a given task ● PET tracks radioactive substances to produce images of brain activity ○ positron emission tomography (PET) - a brain imaging technology that tracks the metabolism of injected radioactive substances in the brain, in order to map brain activity

● Magnetism can be used to study the brain

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○ transcranial magnetic stimulation (TMS) - noninvasive technique for examining brain function that applies stimulates cortical neurons with magnetic fields to identify brain areas that are particularly active during specific behaviors

○ magnetoencephalography (MEG) - a noninvasive brain-imaging technology that creates maps of brain activity during cognitive tasks by measuring tiny

magnetic fields produced by active neurons

______________________________________________________________________________ ● Which region of the cortex is crucial for motor control? the precentral gyrus ● A group of axons traveling together within the brain is called a tract ● A group of axons traveling together in the peripheral nervous system is a nerf ● the central sulcus divides the frontal​ and parietal​ lobes

● The two cerebral hemispheres are connected by the corpus callosum Chapter 3 

Neurophysiology 

● neurophysiology - the study of the life generation, transmission, and integration of neurons and neural signals 

Electrical Signals Are the Vocabulary of the Nervous System ● A balance of electrochemical forces produces the resting potential of neurons ○ four factors: concentration gradient, electrical gradient, selective permeability, and the sodium-potassium pump

○ Of all the ions in a neuron, a majority are anions and the rest are cations ■ ion - an atom or molecule that has acquired an electrical charge by

gaining or losing one or more electrons

■ anion - a negatively charged ion, such as a protein or a chloride ion

■ cation - a positively charged ion, such as a potassium or sodium ion ■ inside the neuron there are lots of anions in the form of proteins and there’s also a lot of potassium (K+), very little sodium inside the cell, few chloride ions, few calcium ions

■ outside the neuron, lots of Na+ which is a cation, not much potassium, a lot of Cl-ions and Ca2+ions and few proteins

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○ All of these ions are dissolved in the intracellular fluid inside the cell and the extracellular fluid surrounding the cell membrane

■ intracellular fluid - aka cytoplasm; the watery solution found within cells

■ extracellular fluid - the fluid in the spaces between cells (interstitial fluid)

■ cell membrane - the lipid bilayer that ensheaths a cell

○ microelectrode - an especially small electrode used to record electrical potentials inside living cells

○ resting potential - the difference in electrical potential across the membrane of a nerve cell at rest

■ a neuron at resting potential generally exhibits a resting potential of -50 to -80 millivolts

○ millivolt (mV) - a thousandth of a volt

○ ion channel - a pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open

○ potassium ion (K+) - a potassium atom that carries a positive charge ■ can usually get through ion channels

○ sodium ion (Na+) - a sodium atom that carries a positive charge

■ usually can’t get through ion channels

○ selective permeability - the property of a membrane that allows some substances to pass through, but not others

● The resting potential of the neuron reflects a balancing act between two opposing forces that drive K+ions in and out of the neuron

○ diffusion - the spontaneous spread of molecules from an area of high concentration to an area of low concentration until a uniform concentration is achieved

○ electrostatic pressure - the propensity of charged molecules or ions to move toward areas with the opposite charge

● Much of the energy consumed by a neuron goes into operating specialized membrane proteins called sodium potassium pumps that pump 3 Na+ions out of the cell for every 2 K+ions pumped in

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○ sodium-potassium pump - the energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in

○ equilibrium potential - the point at which the movement of ions across the cell membrane is balanced, as the electrostatic pressure pulling ions in one direction is offset by the diffusion force pushing them in the opposite direction

● A threshold amount of depolarization triggers an action potential ○ axon hillock - the cone-shaped area on the cell body from which the axon originates

○ Two concepts are central to understanding how action potentials are triggered: ○ hyperpolarization - an increase in membrane potential (the interior of the neuron becomes even more negative)

○ depolarization - a decrease in membrane potential (the interior of the neuron becomes less negative)

○ local potential - an electrical potential that is initiated by stimulation at a specific site, which is a graded response that spreads passively across the cell membrane, decreasing in strength with time and distance

○ threshold - the stimulus intensity that is just adequate to trigger an action potential in an axon

○ action potential - also called spike; a rapid reversal of the membrane potential that momentarily makes the inside of the membrane positive with respect to the outside

○ Three phases of an action potential involve the opening and closing of voltage-activated sodium and potassium channels during these three phases: ■ rising phase - when the action potential and membrane is going more positive

■ repolarization - neuron begins to return back to its resting state

■ hyperpolarization - overshoots the resting potential and goes negative for a little bit

■ When sodium channels are opened, positively charged sodium ions rush in and a subsequent nerve impulse occurs

● cations rush through channel and a subsequent action potential

occurs

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● AT THRESHOLD, THE SODIUM CHANNELS OPEN AND

SODIUM FLOODS IN and you get the rising phase of the action

potential

● occurs until there’s an equilibrium of sodium ions on the inside

and outside of the membrane

○ At the peak​ of action potential:

■ inside of the cell is POSITIVE with respect to the outside (reversed polarity)

■ sodium channels close quickly

○ all-or-none property - referring to the fact that the size (amplitude) of the action potential is independent of the size of the stimulus

○ afterpotential - the positive or negative change in membrane potential that may follow an action potential

● Ionic mechanisms underlie the action potential

○ voltage-gated Na+ channel - A Na+ selective channel that opens or closes in response to changes in the voltage of the local membrane potential; it mediates the action potential

○ refractory - temporarily unresponsive or inactivated

■ The axonal membrane is said to be refractory to the second stimulus ■ absolute refractory phase - a brief period of insensitivity to stimuli ■ relative refractory phase - a period of reduced sensitivity during which only strong stimulation produces an action potential

● Action potentials are actively propagated along the axon

○ conduction velocity - the speed at which an action potential is propagated along the length of an axon

○ myelin - the fatty insulation around an axon, formed by glial cells; this sheath boosts the speed at which action potentials are conducted

○ node of Ranvier - a gap between successive segments of the myelin sheath where the axon membrane is exposed

○ saltatory conduction - the form of conduction that is characteristic of myelinated axons, in which the action potential jumps from nodes of Ranvier ■ rapid flow of ions between nodes (jumps from node to node)

● remember the nodes of ranvier between sections of myelin

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○ here there are lots and lots of sodium channels

■ NA+ gates are in high abundance at nodes, but virtually absent along myelinated portions, so not much positive charge can enter the axon at internodes

● How is an Axon like a Toilet?y6g

○ a toilet flush is similar to an action potential

■ All-or-none property

● pushing the toilet lever harder does not produce a bigger flush;

pushing a neuron past threshold does not increase the size of the

action potential

■ Refractory phase

● absolute refractory period: after it fires an action potential,

there’s a period when it cannot fire again (lasts for about 1

millisecond) happens on either side of the peak

● relatively refractory period: sometimes it can fire again but it

would require a very strong stimulus

● until the tank is full, the toilet will not flush again; until the Na+

channels recover, the neuron cannot produce another action

potential

■ Direction

● like water in a properly operating toilet, an action potential

always travels in one direction only

● multiple sclerosis (MS) - literally “many scars”; a disorder characterized by the widespread degeneration of myelin

● Synapses cause local changes in the postsynaptic membrane potential ○ neurotransmitter - also called simply transmitter, synaptic transmitter, or chemical transmitter; the chemical released from the presynaptic axon terminal that serves as the basis of communication between neurons

○ presynaptic - located on the “transmitting” side of a synapse

○ postsynaptic - about the region of a synapse that receives and responds to nt ○ postsynaptic potential - a local potential that is initiated by stimulation at a synapse, which can vary in amplitude, and spreads passively across the cell membrane, decreasing in strength with time and distance

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■ excitatory postsynaptic potential (EPSP) - a depolarizing potential in the postsynaptic neuron that is normally caused by synaptic excitation;

EPSPs increase the probability that the postsynaptic neuron will fire an action potential

■ inhibitory postsynaptic potential (IPSP) - a hyperpolarizing potential in the postsynaptic neuron; IPSPs decrease the probability that the

postsynaptic neuron will fire an action potential

■ chloride ion (Cl-) - a chlorine atom that carries a negative charge

● Spatial summation and temporal summation integrate synaptic inputs ○ spatial summation - the summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body; if this summation reaches threshold, an action potential is triggered

○ temporal summation - the summation of postsynaptic potentials that reach the axon hillock at different times; the closer in time the potentials occur, the more complete the summation is

Synaptic Transmission Requires a Sequence of Events ● Synapse Structure

○ what we’re most concerned with is a directed synapse​ where the presynaptic and postsynaptic membrane are very close together

■ synaptic cleft is the space between the two membranes

● Synaptic Transmission Overview: Sequence of Events

○ The action potential arrives at the presynaptic axon terminal and voltage-gated calcium channels in the membrane of the axon terminal open, and calcium ions (Ca2+) enter the axon terminal.

○ Ca2+ binds to synaptic vesicles filled with neurotransmitter and makes them fuse with the presynaptic membrane and rupture, releasing the transmitter molecules into the synaptic cleft.

○ neurotransmitter released by the process of exocytosis

○ Some transmitter molecules bind to special receptor molecules in the postsynaptic membrane, leading--directly or indirectly--to the opening of ion channels in the postsynaptic membrane. The resulting flow of ions creates a local EPSP or IPSP in the postsynaptic neuron.

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○ The IPSPs and EPSPs in the postsynaptic cell spread toward the axon hillock. (If the sum of all the EPSPs and IPSPs ultimately depolarizes the axon hillock enough to reach threshold, an action potential will arise.)

○ Synaptic transmission is rapidly stopped, so the message is brief and accurately reflects the activity of the presynaptic cell.

○ Synaptic transmitter may also activate presynaptic receptors, resulting in a decrease in transmitter release.

● Phases of an Action Potential

○ Resting

○ Depolarize (absolutely refractory)

○ Repolarize (relatively refractory)

○ Hyperpolarize (relatively refractory)

○ Resting

● Action potentials cause the release of transmitter molecules into the synaptic cleft ○ synaptic cleft - the space between the presynaptic and postsynaptic neurons at a synapse; this gap measures about 20-40 minutes

○ calcium ion (Ca2+) - a calcium atom that carries a double positive charge ○ synaptic delay - the brief delay between the arrival of an action potential at the axon terminal and the creation of a postsynaptic potential

● Receptor molecules recognize transmitters

○ ligand - a substance that binds to receptor molecules, such as a

neurotransmitter or drug that binds postsynaptic receptors

○ acetylcholine (ACh) - a neurotransmitter that is produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain

○ neurotransmitter receptor - also called simply receptor; a specialized protein, often embedded in the cell membrane, that selectively senses and reacts to molecules of a corresponding neurotransmitter or hormone

○ curare - a neurotoxin that causes paralysis by blocking acetylcholine receptors in muscle

○ bungarotoxin - a neurotoxin, isolated from the venom of the many-banded krait, that selectively blocks acetylcholine receptors

○ agonist - a substance that mimics or potentiates the actions of a transmitter

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○ antagonist - a substance that blocks or attenuates the actions of a transmitter ○ cholinergic - when cells use acetylcholine as their synaptic transmitter ● The action of synaptic transmitters is stopped rapidly

○ degradation - the breakdown of a neurotransmitter into inactive metabolites ○ acetylcholinesterase (AChE) - an enzyme that inactivates acetylcholine ○ reuptake - the process by which released synaptic transmitter molecules are

taken up and reused by the presynaptic neuron, thus stopping synaptic activity ○ transporter - a specialized membrane component that returns transmitter molecules to the presynaptic neuron for reuse

● Neural circuits underlie reflexes

○ dendrodendritic synapse - a synapse at which a synaptic connection forms between the dendrites of two neurons

○ axodendritic synapse - a synapse at which a presynaptic axon terminal synapses onto a dendrite​ of the postsynaptic neuron, either via a dendritic spine or directly onto the dendrite itself

○ axosomatic synapse - a synapse at which a presynaptic axon terminal synapses onto the cell body (soma)​ of the postsynaptic neuron

○ axoaxonic synapse - a synapse at which a presynaptic axon terminal synapses onto the axon terminal​ of another neuron

■ neuron A has the presynaptic terminal, neuron B has the postsynaptic terminal that is ALSO the presynaptic terminal for neuron C

■ presynaptic facilitation​: neurotransmitter binding to presynaptic

receptor INCREASES the release of neurotransmitter from that axon

terminal

■ presynaptic inhibition​: neurotransmitter binding to presynaptic

receptor DECREASES the release of neurotransmitter from that axon

terminal

○ directed synapses: close proximity between pre- and postsynaptic terminals ○ knee-jerk reflex - a variant of the stretch reflex in which stretching of the tendon beneath the knee leads to an upward kick of the leg

EEGs Measure Gross Electrical Activity of the Human Brain

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● electroencephalogram (EEG) - a recording of gross electrical activity of the brain via large electrodes placed on the scalp

● event-related potential (ERP) - aka evoked potential; averaged EEG recordings measuring brain responses to repeated presentations of a stimulus; components of this tend to be reliable because the background noise of the cortex has been averaged out ● Electrical storms in the brain can cause seizures

○ epilepsy - a brain disorder marked by major, sudden changes in the electrophysiological state of the brain that are referred to as seizures

○ seizure - a wave of abnormally synchronous electrical activity in the brain ■ grand mal seizure - a type of generalized epileptic seizure in which

nerve cells fire in high-frequency bursts, usually accompanied by

involuntary rhythmic contractions of the body

■ petit mal seizure - also called absence attack; a seizure that is

characterized by a spike-and-wave EEG and often involves a loss of

awareness and inability to recall events surrounding the seizure

■ complex partial seizure - in epilepsy, a type of seizure that doesn’t

involve the entire brain and therefore can cause a variety of symptoms

■ aura - in epilepsy, the unusual sensations or premonition that may

precede the beginning of a seizure

Chapter 4 

The Chemistry of Behavior 

● exogenous - arising from outside the body

● endogenous - produced inside the body

Electrical Signals Are Turned into Chemical Signals at Synapses ● presynaptic - located on the “transmitting” side of a synapse

● synapse - the place in the cell where info is transmitted from a neuron to another cell ● neurotransmitter - aka transmitter; a signaling chemical released by a presynaptic neuron that diffuses across the synaptic cleft and alters the postsynaptic neuron’s functional abilities

● exocytosis - a cellular process that releases a substance into the extracellular space

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● neurotransmitter receptor - a specialized protein embedded in the cell membrane; it can selectively sense and react to molecules of their corresponding neurotransmitter ● postsynaptic - located on the “receiving” end of a synapse

● reuptake - when the neurons that released the neurotransmitter reabsorb it; this stops the signaling activity of the transmitter molecules

● transporter - a specialized part of the membrane that brings transmitter molecules back to the presynaptic neuron for reuse

● Synapses Convert Electrical Signals into Chemical Signals

○ Action potentials arrive at the axon terminal

○ This causes voltage-gated Ca2+ channels to open

■ the resultant calcium influx causes synaptic vesicles to rupture and release transmitter molecules into the synaptic cleft

○ Molecules of neurotransmitter bind to postsynaptic receptors and alter functioning of the postsynaptic cell

○ The action of the released neurotransmitter is rapidly reversed in a process called presynaptic reuptake

■ transporters on the presynaptic terminal reabsorb transmitter

molecules to recycle them

■ enzymes within axon terminals such as MAO and other enzymes in or near the synaptic cleft, rapidly break down neurotransmitters

● Synthesis, Packing, and Transport of Neurotransmitter Molecules ○ there are generally two types of neurotransmitter: large and small ○ large NTs (neuropeptides) are synthesized in the soma and need ribosome ■ must be transported out to the terminals

○ small neurotransmitters are made at the site in which they’ll be released: in the cytoplasm of axon terminal

■ packaged into vesicles by Golgi complex

○ Coexpression of Neurotransmitters

■ the same neuron can release a large and a small neurotransmitter ■ microtubules: railway

● Receptor proteins recognize transmitters and their mimics

○ A given neurotransmitter may interact with many different receptors in different parts of the brain...

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○ A neurotransmitter may activate an ionotropic receptor, and this would open an ion channel and affect the postsynaptic cell’s membrane potential ■ ionotropic receptor - aka ligand-gated ion channel; a receptor protein that contains an ion channel which opens when the receptor is bound by an agonist

● “transmitter-gated” or “ligand-gated” channels are controlled by a neurotransmitter or drug that mimics that neurotransmitter

● most effects occur very quickly (sometimes less than a

millisecond after attaching) and are very short lasting

○ good for visual, auditory response, muscle contraction

● ionotropic responses often involve GABA, glutamate, glycine, ACh ○ The same neurotransmitter from above may, at another synapse, activate a metabotropic receptor, which activates second messengers via G proteins that open other ion channels, and/or cause other changes in the cell ■ metabotropic receptor - a receptor protein without ion channels that may, when activated, use a second messenger system to open ion channels nearby or to produce other cellular effects

■ metabotropic response - involves a two or more step process ● more complicated process than ionotropic response

● metabotropic receptor consists of single protein that spans cell membrane (NOT a channel, a protein)

● receptor is linked to G-protein

● after neurotransmitter binds to a receptor, a subunit of the

G-protein breaks away and does one of the two things:

○ moves along inside of membrane to activate ion channel

directly (results in EPSP or IPSP) or

○ triggers synthesis of a second messenger to affect other

cellular processes

● metabotropic response takes longer to occur (longer latency) but lasts longer (longer duration) than ionotropic response

● metabotropic response may activate a second messenger

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○ second messenger - a chemical that’s activated by the

neurotransmitter (the first messenger) and carries a

message to initiate some biochemical process

● Autoreceptors (special type of metabotropic)

○ is in the presynaptic membrane

○ called this because the neuron is releasing some

neurotransmitter, but this autoreceptor is in the

presynaptic membrane

○ one way that the neuron regulates its own activity

(provides negative feedback​)

○ a built-in brake for the system (so the neuron stops

releasing neurotransmitter for a lil bit)

■ EITHER (3 options) the neurotransmitter can bind to receptors on the postsynaptic terminal, they can be sucked back up by the presynaptic

terminal, or they bind to autoreceptors which put a brake on nt release Neurotransmitters: which result in EPSPs, in IPSPs, and which have other effects ● neurotransmitters can be classified by their function (EPSP or IPSP) or their structure ○ named after structure, function depends on what receptors are there ● Overview of the Transmitter Classes

○ Small-Molecule Neurotransmitters

■ many are derived from amino acids

● fast-acting/point-to-point synapses

● glutamate, aspartate, glycine, GABA

● all of those except GABA are common in edible proteins

■ monoamines

● synthesized from a single amino acid

● slow, lingering and diffuse effects

● arise from brainstem

● Cathecholamines/Indolamines

● dopamine, epinephrine, norepinephrine

■ Acetylcoline

● used at neuromuscular junctions (need it to move on our own)

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● autonomic nervous system

● central nervous system

● uses enzymatic degradation predominantly

○ deactivated by enzymes in synapse - acetylcholinesterase

○ Unusual Small Neurotransmitters

■ Soluble Gases (Nitric oxide/carbon monoxide)

■ produced in the neural cytoplasm

■ unconventional because they can be diffused and are liquid soluble ■ activate second messengers

■ short-lived

■ retrograde transmission

■ Neuropeptides: Large-Molecule Nts (are weird and can be released in diff places)

● short chains of amino acids

● around 100 types in 5 loose categories:

○ pituitary

○ hypothalamic

○ brain-gut

○ opioid

○ miscellaneous

● Endorphins as an example -> Analgesia (pain reduction)/Reward Systems

● *serotonin is made from tryptophan

○ Negative Feedback

■ Accomplished in two ways:

● Autoreceptors: metabotrpoic receptors that detect the amount of transmitter released

● Postsynaptic neurons: respond to stimulation by releasing

chemicals that travel back to the presynaptic terminal where they inhibit further release (ex: nitric oxide)

○ The Roles and Functions of Neurotransmitters

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○ many buttons contain two sizes of vesicles; many also contain neuropeptides ○ when a small nt molecule binds to an ionotropic receptor, the associated ion channel opens or closes

○ One more time, steps in transmission at a chemical synapse: ■ The action potential is propagated over the presynaptic membrane. ■ Depolarization of the presynaptic terminal leads to influx of Ca2+. ■ Ca2+ causes vesicles to fuse with the presynaptic membrane and release transmitter into the synaptic cleft

■ The binding of transmitter to neurotransmitter receptors in the postsynaptic membrane opens channels, permitting ion flow and initiating an excitatory or inhibitory postsynaptic potential.

■ EEPSP or IPSP spreads passively over dendrites and the cell body to the axon hillock.

● do NOT want too much excitation in your brain. leads to things like seizures.

■ Enzyme present in the extracellular space breaks down excess transmitter. OR

■ Reuptake of transmitter slows synaptic action and recycles transmitter for subsequent transmission

■ Transmitter binds to autoreceptors in the presynaptic membrane ○ Ionotropic versus Metabotropic Receptors

■ Metabotropic

● G-protein can activate second messenger cascades

○ Classification of Neurotransmitters

■ functional: excitatory vs inhibitory

■ structural: based on chemistry

■ Amino Acid Derivatives

● fast-acting/point-to-point synapses

● GABA, Glutamate, Aspartate, Glycine

● All but GABA are common in edible proteins

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■ Monoamine Neurotransmitters - very important for neural modulation ● Monoamine systems

○ Dopaminergic

○ Noradrenergic

● Acetylcholine

○ neuromuscular junctions

○ autonomic nervous system

○ central nervous system

○ deactivated by enzymes in synapse - acetylcholinesterase 

Neurotransmitter Systems Form a Complex Array in the Brain ● The most abundant excitatory and inhibitory neurotransmitters are amino acids ○ glutamate - an amino acid nt that is the most common excitatory transmitter ○ gamma-aminobutyric acid (GABA) - a widely distributed amino acid transmitter that is the main inhibitory transmitter in all mammals’ nervous systems ● Four amine neurotransmitters modulate brain activity

○ Acetylcholine

■ cholinergic - contains ACh

■ found in nuclei within the basal forebrain - a region ventral to the basal ganglia that is the brain’s most major source of ACh

○ Dopamine (DA) - a monoamine transmitter found in the midbrain (particularly the substantia nigra) and the basal forebrain

■ dopaminergic - refers to cells that use dopamine as their synaptic

transmitter

■ substantia nigra - a brainstem structure that innervates the basal

ganglia and is a major source of dopaminergic projections

■ ventral tegmental area (VTA) - a part of the midbrain that projects

dopaminergic fibers to the nucleus accumbens

○ Serotonin

■ serotonergic - refs to cells whose synaptic transmitter is serotonin

■ raphe nuclei - a string of nuclei in the midline of the midbrain and

brainstem that contain most of the brain’s serotonergic neurons

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■ serotonin (5-HT) - a synaptic transmitter produced in the raphe nuclei that is active in various structures in the cerebral hemispheres

○ Norepinephrine (NE) - aka noradrenaline; a neurotransmitter that accelerates organ activity; produced and released by sympathetic postganglionic neurons ■ noradrenergic - refers to cells whose transmitter is NE

■ locus coeruleus - a small nucleus in the brainstem whose neurons

produce norepinephrine and modulate large parts of the forebrain

■ lateral tegmental area - a brainstem region that provides some of the norepinephrine-containing projections of the brain

● Many peptides function as neurotransmitters

○ opioid peptide - a type of endogenous peptide that mimics the effects of morphine by binding to opioid receptors and provides reward by relieving pain ● Some neurotransmitters are gases

○ Gases neurotransmitters vs. regular neurotransmitters: 3 main differences 1. gas transmitter is produced outside of the axon terminals (ex. dendrites) and is not held in the vesicles; the substance diffuses out of the neuron

as it’s produced

2. no receptors in the membrane of the target cell are involved; the gas transmitter diffuses into the target cell and triggers second messengers 3. gases can function as retrograde transmitters so they can convey

information that is used to physically change the synapse

a. retrograde transmitter - a neurotransmitter that diffuses from

the postsynaptic neuron back to the presynaptic neuron

Drugs Fit Like Keys into Molecular Locks 

● ligand - a substance that binds to a receptor; ex: neurotransmitter, drug ● agonist - drugs that mimic or potentiate a neurotransmitter’s actions ● antagonist - drugs that reduce the normal functioning of a neurotransmitter system ● The effects of a drug depend on its dose.

○ (binding) affinity - the propensity of molecules of a drug or other ligand to bind to receptors

○ efficacy - aka intrinsic activity; the extent to which a drug activates a response when binding to a receptor

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○ dose-response curve (DRC) - a graph of a drug’s effects versus the dose given ● Drug doses are administered in many different ways.

○ bioavailable - refers to a substance/drug that is present in the body in a form that’s able to interact with physiological mechanisms

○ biotransformation - the process in which enzymes convert a drug into a metabolite that is itself active (possibly in ways that substantially differ from the actions of the original substance)

○ pharmacokinetics - the collective name for all the factors that affect the movement of a drug into, through, and out of the body

○ blood-brain barrier - the protective property of cerebral blood vessels that hinders the movement of some harmful substances into the brain from the bloodstream

● Repeated treatments can reduce the effectiveness of drugs

○ drug tolerance - when with repeated drug exposure, a person becomes less responsive to a constant dose

○ metabolic tolerance - a form of drug tolerance when repeated exposure to the drug causes the body’s metabolism to be more efficient at clearing the drug ○ functional tolerance - a form of drug tolerance when repeated drug exposure causes receptors to be up-regulated or down-regulated

■ down-regulation - a compensatory decrease in receptor availability at the synapses of a neuron

■ up-regulation - a compensatory increase in receptor availability at the synapses of a neuron

○ cross-tolerance - a condition where the development of a tolerance to one drug causes someone to develop tolerance for another drug (of same chemical class) Drugs Affect Each Stage of Neural Conduction and Synaptic Transmission ● Some drugs alter presynaptic processes

○ Effects on Transmitter Production

■ inhibition of transmitter synthesis

■ blockade of axonal support

■ interference with the storage of transmitters

○ Effects on Transmitter Release

■ prevention of synaptic transmission

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■ alteration of synaptic transmitter release

■ modulation of transmitter release by presynaptic receptors

■ autoreceptor - a receptor for a synaptic transmitter that is located in the presynaptic membrane and tells the axon terminal how much

transmitter has been released

○ Effects on Transmitter clearance

■ inactivation of transmitter reuptake

■ blockade of transmitter degradation

● Some drugs alter postsynaptic processes

○ Transmitter Receptor-Selective Drugs

■ effects on transmitter receptors:

● blockade of receptors

○ ex: antipsychotic drugs block some dopamine receptors

● activation of receptors

○ ex: LSD is an agonist at some serotonin receptors

○ Process Inside Postsynaptic Neurons

■ effects on cellular processes:

● change in the number of postsynaptic receptors

○ ex: alcohol increases the number of GABA receptors

● modulation of second messengers

Drugs That Affect the Brain Can Be Divided into Functional Classes ● Psychoactive drugs may relieve severe symptoms

○ Antipsychotics - aka neuroleptics; drugs that alleviate symptoms of

schizophrenia by blocking dopamine receptors

■ atypical antipsychotic - an antipsychotic drug that has actions other than or in addition to the dopamine D2 receptor antagonism that

characterizes typical antipsychotics

○ Antidepressants - drugs that relieve the symptoms of depression

■ monoamine oxidase (MAO) - an enzyme that breaks down and

inactivates monoamine transmitters

■ tricyclic antidepressant - an antidepressant that increases serotonin and norepinephrine accumulation

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■ selective serotonin reuptake inhibitor (SSRI) - an antidepressant that blocks the reuptake of transmitter at serotonergic synapses

○ Anxiolytics - drugs used to combat anxiety

■ depressant - a drug that reduces the excitability of neurons

■ barbiturate - an early anxiolytic drugs and sleep aid that has depressant activity in the nervous system

■ benzodiazepine - drugs that are agonists of GABAA receptors in the central nervous system; ex: Valium

○ Opiates

■ opium - an extract of the opium poppy; drugs based on opium are potent painkillers

■ morphine - an opiate compound derived from the poppy flower

■ analgesic - having pain killing properties

■ heroin - diacetylmorphine, an artificially modified, very potent form of morphine

■ opioid receptor - a receptor that responds to endogenous opioids and/or exogenous opiates

■ periaqueductal gray - a midbrain region involved in pain perception ■ endogenous opioid - any of a class of opium-like peptide transmitter that has been referred to as the body’s own narcotics

■ There are three major families of potent peptides:

● enkephalin, endorphin, dynorphin

● Psychoactive drugs can affect conscious experience.

○ Atropine - a cholinergic receptor blocker

■ deadly nightshade plant; caused ANS antagonistic effects on muscarinic receptors and made pupils really big

○ Curare - cholinergic receptor blocker

■ used by many indigenous peoples for poisonous darts

■ blocks nicotinic (muscular junction) receptors causing paralysis and death

■ actually used very commonly in surgery

○ Botox -> derived from the bacteria Botulinum toxin that is the most potent toxin known

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■ Blocks release of acetylcholine which makes it toxic (voluntary movement etc)

○ Endogenous Opiates

■ Enkaphalins -> opioid neuropeptides

■ Endorphins - think of runner’s high

○ Tobacco

■ nicotine - a compound found in tobacco plants that acts as an agonist on a large class of cholinergic receptors

■ stimulant - a drug that enhances the excitability of neurons ○ Alcohol

■ central nervous system depressant

■ pinpointing a site of action or a single mechanism of alcohol effects is difficult because the drug effects cell membranes, all neurochemical systems, and all endocrine systems

■ fetal alcohol syndrome - a disorder that affects children exposed to too much alcohol through maternal ingestion during fetal development ● includes intellectual disability and characteristic facial

abnormalities

○ Marijuana

■ delta-9-tetrahydrocannabinol (THC) - the major active ingredient in marijuana

■ endocannabinoid - an endogenous ligand of cannabinoid receptors which acts as an analog of marijuana that is produced by the brain ■ anandamide - an endogenous substance that binds the cannabinoid receptor molecule

○ Stimulants

■ cocaine - a drug of abuse, derived from the coca plant, that acts by enhancing catecholamine neurotransmission

● the dopamine transporter normally moves unbound dopamine from the synapse into the sending neuron

○ Ritalin and cocaine both block the dopamine transporter,

causing dopamine to build up in the synapse

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■ amphetamine - a molecule that resembles the structure of the

catecholamine transmitters and enhances their activity

○ Hallucinogens - drugs that alter sensory perception and produce peculiar experiences

■ LSD - lysergic acid diethylamide, a hallucinogenic drug that structurally resembles serotonin and pretty specifically acts on serotonin receptors and has predominantly postsynaptic effect

■ MDMA - aka ecstasy; a drug of abuse

Drug Abuse 

● The moral model

● The disease model

● The physical dependence model

○ withdrawal symptoms - an uncomfortable symptom that arises when a person stops taking a drug that he or she has used frequently, especially at high doses ○ dysphoria - unpleasant feelings; the opposite of euphoria

● The positive reward model

● nucleus accumbens - a region of the forebrain that receives dopaminergic innervation from the ventral tegmental area, often associated with reward and pleasurable feelings ● insula - a region of cortex lying below the surface, within the lateral sulcus, of the frontal, temporal, and parietal lobes

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