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USC / OTHER / EXSC 224 / what are the three functions of the nervous system?

what are the three functions of the nervous system?

what are the three functions of the nervous system?

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School: University of South Carolina
Department: OTHER
Course: Anatomy and Physiology II
Term: Spring 2017
Tags: nervous system
Cost: 50
Name: Exam 1 Study Guide
Description: This study guide includes detailed outlines to answer all of the learning objectives for all of the sections of the chapters that exam 1 will be on. The content covers Ch. 11.1-11.10, 12.1-12.8, 12.10-12.11, 13.5, fig. 13.13
Uploaded: 02/03/2017
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EXSC 224 Exam 1: CH 11-13 Study Guide


what are the three functions of the nervous system?



Exam material: 11.1-11.10, 12.1-12.8, 12.10-12.11, 13.5, fig. 13.13

Learning objectives for chapter 11

11.1 Learning objectives

List the basic functions of the nervous system.

• Nervous system has 3 functions

1. Sensory input: sensory receptors detect changes inside and outside the body 2. Integration: processing of the sensory input to decide what to do

3. Motor output: nervous system activates effector organs (muscles and glands) to  cause a response

o Ex: see a red light while driving (sensory input), nervous system recognizes what  this info means and what to do (integration), foot hits the brake (motor output) Explain the structural and functional divisions of the nervous systems.

• Central nervous system (CNS)

o Brain and spinal cord

o Control center of the nervous system


what is the central nervous system (cns) composed of?



We also discuss several other topics like what is germline cell?

o Interprets sensory information and dictates motor output

• Peripheral nervous system (PNS)

o Consists of nerves that extend from the brain and spinal cord

▪ Spinal nerves: carry impulses to and from spinal cord

▪ Cranial nerves: carry impulses to and from the brain

o Contains ganglia: collections of neuron cell bodies

o Two divisions: afferent (sensory) and efferent (motor)

▪ Afferent 

• Nerve fibers that carry impulses to the central nervous system  We also discuss several other topics like What is aneuploids?

from sensory receptors

• Somatic sensory fibers convey impulses from skin, skeletal  

muscles, and joints

• Visceral sensory fibers convey impulses from the visceral organs

• Keeps the CNS aware of what is going on in and out of the body

▪ Efferent 

• Transmits impulses from the CNS to effector organs


what is Autonomic nervous system?



We also discuss several other topics like What is the Civil Adult population?

• Has 2 parts

o Somatic nervous system

▪ Somatic nerve fibers that conduct impulses from  

the CNS to skeletal muscles

▪ Voluntary

o Autonomic nervous system

▪ Visceral motor nerve fibers that regulate activity of  

smooth and cardiac muscles and glands

▪ Involuntary

▪ Has 2 subdivisionsDon't forget about the age old question of What is a political action committees?

• Sympathetic: stimulates

• Parasympathetic: inhibits

11.2 Learning objectives

List the types of neuroglia and cite their functions.

• Neuroglia: supporting cells to neurons

o Glial cells in CNS

▪ Astrocytes 

• Most abundant, versatile, lots of branches

• Cling to neurons, synaptic endings, and capillaries

• Support and brace neurons (hold them in place)

• Help determine capillary permeability

▪ Microglia 

• Small, ovoid cells with thorny processes

• 1st line of defense

• alerts immune system to any problems

• migrate toward injured neurons

• phagocytize

▪ ependymal cells 

• line cavities of brain and spinal column

• separate CNS interstitial fluid from cerebrospinal fluid

• produce cerebrospinal fluid at choroid plexuses

• water tight seal

• may be ciliated to help with circulation of cerebrospinal fluid Don't forget about the age old question of What is the difference between conscious and nonconscious processing?
If you want to learn more check out How is gene expression regulated?

▪ oligodendrocytes 

• make myelin

• processes wrap around axons in CNS to insulate

• myelin speeds up transmission

• multiple sclerosis: demyelination in CNS

o Glial cells in PNS

▪ Satellite cells 

• Surround neuron cell bodies

• Same function as astrocytes: support and brace neurons

▪ Schwann cells 

• Surround nerve fibers to form myelin sheath

• Vital to regeneration of damaged peripheral nerve fibers

11.3 Learning objectives

Define neuron, describe its important structural components, and relate each to a functional  role.

• Characteristics

o Typically large

o Highly specialized cells

o Extreme longevity: with good nutrition, they last a lifetime

o Amitotic: can’t divide

o High metabolic rate: use lots of oxygen and glucose

• Neuron cell body (soma)

o Biosynthetic center of the neuron: produces all the necessary proteins and  chemicals

o Has a really well-developed Rough ER (called Nissl bodies) and Golgi apparatus  for producing and packaging all the necessary neurotransmitters that are  released following an action potential

o Most neuron cell bodies are in the CNS

▪ Protected here by the skull and vertebral column

▪ Clusters of cell bodies in the CNS are called nuclei (called ganglia in the  PNS)

• Neuron processes: arm-like extensions from the cell body

o Include dendrites and axons

o PNS consists mostly of neuron processes

o Dendrites

▪ Diffusely branching extensions

▪ Has the same organelles as the cell body

▪ Main receptive/input region

▪ Large surface area for receiving signals from other neurons

▪ Send signals to the cell body, typically as graded potentials

o Axon

▪ Structure

• Each neuron has only one

• Axon hillock: initial region

• Some are short and some are really long

• Axon collaterals: Occasional branches along its length

• Terminal branches: Lots of branching at the end (10,000 or more)

• Axon terminals: knoblike endings of the terminal branches

▪ Functional characteristics

• Conducting region of the neuron: generates nerve impulses and  

transmits them

• Nerve impulse generated at the axon hillock and travels to the  

axon terminals (secretory region of the neuron)

o Neurotransmitters released from the axon terminals when  

the impulse reaches them

• Has organelles but NO rough ER or Golgi apparatus

▪ Axonal transport

• Cytoskeletal elements help move substances in the neuron along  

the axon

• Anterograde movement: movement away from the cell body

o Things transported this way: mitochondria, membrane  

components to renew the axon plasma membrane,  

enzymes for neurotransmitter synthesis

• Retrograde movement: movement to the cell body

o Things transported this way: organelles that need to be  

degraded or recycled

o Also important means of intracellular communication

Differentiate between (1) a nerve and a tract, and (2) a nucleus and a ganglion. • Nerve vs tract

o Nerve: bundles of axons in the CNS

o Tract: bundles of axons in the PNS

• Nucleus vs ganglion

o Nucleus: collection of neuron cell bodies in the CNS

o Ganglion: collection of neuron cell bodies in the PNS

Explain the importance of the myelin sheath and describe how it is formed in the central and  peripheral nervous systems.

• Myelin sheath

o Whitish, fatty protein-lipoid

o Function: insulates fibers and increases the transmission speed of nerve  impulses

o Associated with axons

• Myelination in the PNS

o Formed by Schwann cells

o Schwann cells wrap themselves around the axons in concentric layers (like  wrapping gauze around an injured finger)

o Channel and carrier proteins are absent, helps them be good electrical  conductors

o Nodes of Ranvier: gaps of exposed axon between adjacent Schwann cells • Myelination in the CNS

o Formed by oligodendrocytes

o Oligodendrocytes have multiple processes that can coil as many as 60 axons at  the same time

o White matter: dense collections of myelinated fibers

o Gray matter: mostly cell bodies and non-myelinated fibers

Classify neurons by structure and by function.

• Classification of neurons

o Structural classification: number of processes extending from the cell body ▪ Multipolar: 3+ processes (one axon and the rest dendrites)

• Most common type in humans

▪ Bipolar: 2 processes (one axon and one dendrite)

• Rare, found in retina of eye and olfactory mucosa

▪ Unipolar: 1 process

• Found in ganglia in PNS and function as sensory neurons

o Functional classification: direction the nerve impulse travels relative to the CNS ▪ Sensory/afferent: transmit sensory input to the CNS

▪ Motor/efferent: carry impulses away from CNS to effector organs

▪ Interneurons: shuttle signals between motor and sensory neurons  

through CNS pathways  

• mostly in the CNS

• over 99% of the neurons of the body

11.4 Learning objectives

Describe the relationship between current, voltage, and resistance.

Principles of electricity

• More positive charges are outside the cell than inside

• Energy is required to separate opposite charges across a membrane • If opposite charges are separate, a system has potential energy

• Energy is liberated when charges move toward one another

• Voltage: measure of potential energy generated by separated charges • Potential difference: voltage measure between two points

• Resistance: hindrance to charge flow by plasma membrane

• Insulators: substances with high electrical resistance (myelin)

• Conductors: substances with low electrical resistance (water with electrolytes) Identify different types of membrane ion channels.

Role of membrane ion channels

• 2 main types

o leakage (non-gated) channels

▪ pores

▪ always open

▪ prevent ions from diffusing down concentration gradients

o gated channels (3 types)

▪ chemically (ligand) gated  

• something binds to channel (neurotransmitter)

• neurotransmitter binds to receptor, it changes shape, and opens

▪ voltage gated

• sensitive to voltage

• opens and closes based on changes in membrane voltage

▪ mechanically gated

Define resting membrane potential and describe its electrochemical basis. Resting membrane potential in neuron: -70mV

• generated by

o differences in ionic makeup of intracellular fluid and extracellular fluid ▪ at rest, there is greater Na+ outside the cell and greater K+ inside

o differential permeability of plasma membrane

• Sodium-Potassium pump

o 3 Na+ move from the cytosol into the cell

o 2 K+ move from in the cell to the cytosol 

• concentrations of Na+ and K+ are different in and out of the cell

• not a static condition

• K+ and Na+ go down gradients in leakage channels (about 2 K+ leakage channels exist  per 1 Na+ leakage channel)

11.5 Learning objectives

Describe graded potentials and name several examples.

Graded potentials

• Short-lived

• Localized, only changes the membrane potential near the channel

• Depolarizes or hyperpolarizes

• Spreads as local currents change the membrane potential of adjacent regions • Occurs when gated ion channels open

• Change in membrane potential is greatest at the spot nearest to the ligand channel o Voltage declines with distance from the stimulus

o Have to have a lot of graded potentials to excite the neuron

• classified by where they occur and function

o receptor/generator potential: when a sensory neuron is excited by a form of energy (heat, light, other)

o postsynaptic potential: when the stimulus is a neurotransmitter released by  another neuron

11.6 Learning objectives

Compare and contrast graded potentials and action potentials.

Membrane potentials that act as signals

• 2 types

o graded potentials

▪ in cell body

▪ short distance

▪ occur in dendrites

▪ incoming information

o action potentials

▪ in axons only

▪ long distance signals

▪ all the same magnitude

▪ outgoing information

Explain how action potentials are generated and propagated along neurons. Action potential

• Found in axon hillock, axon, and axon terminal

• Only present if graded potential is large enough (there is an adequate stimulus) • Dependent on presence of graded potentials

• 1=resting state: before the action potential, the membrane potential is at its resting  value of -70 mV

• 2=depolarization: the neuron becomes more positive as Na+ enters the cell, threshold is  reached at -55 mV (red dashed line) and the membrane potential peaks at +30 mV • 3=repolarization: the neuron’s membrane potential decreases as K+ exits the cell • 4=hyperpolarization: the membrane potential decreases past the resting membrane  potential, it overshoots its mark

• afterwards, the sodium potassium pump helps restore it to its resting state Define saltatory conduction and explain how it is different from continuous conduction. • saltatory conduction

o occurs in myelinated axons

o much faster than continuous conduction

o action potential “jumps” to each node of Ranvier where the only voltage gated  channels that exist are

o this speeds up transmission

• continuous conduction

o occurs in unmyelinated axons

o slower

o action potential is sent short distances to each voltage gated channel down the  length of the whole axon

11.7 Learning objectives

Define synapse.

The Synapse

• Junction that mediates information transfer from one neuron to another neuron or  effector cell

• Allows for communication

• From the bouton of one neuron to the dendrites/soma of another

• Types of synapses

o Axo-dendritic (from axon of 1 to dendrites of another—most common) o Axo-somatic (from axon of 1 to soma of another—most common)

o Axo-axonic (from axon of 1 to axon of another—SUPER RARE)

• Pre-synaptic neuron: conducts impulse towards the synapse

• Post-synaptic neuron: transmits impulses away from the synapse

Distinguish between electrical and chemical synapses by structure and by the way they  transmit information.

Electrical vs chemical synapses

• Electrical: very rapid, unidirectional or bidirectional

o Important in embryo nervous tissue, some brain regions, and the heart • Chemical: specialized for release and reception of neurotransmitter

o Axon terminal releases neurotransmitter, binds to ligand channel, post-synaptic  neuron receives information

o How the chemical signal is stopped

▪ Enzymes breakdown the neurotransmitter left in the synapse

▪ It’s washed away by interstitial fluid

▪ Reuptake by the pre-synaptic neuron through endocytosis

11.8 Learning objectives

Distinguish between excitatory and inhibitory postsynaptic potentials. • EPSP: excitatory postsynaptic potential

o Neurotransmitter binds and depolarizes the postsynaptic membrane o Action potential sent

• IPSP: inhibitory postsynaptic potential

o Neurotransmitter binds and hyperpolarizes the postsynaptic membrane o Action potential not sent

Describe how synaptic events are integrated and modified.

Integration: summation of graded potentials

• No summation

o Graded potentials fired too far apart in time have no effect, they are not added  together

o The membrane potential is not changed to reach threshold, so no action  potential is sent

• Temporal summation

o If the second graded potential occurs before the end of the first graded  potential, they can add together to have on large change in membrane potential  (possibly enough to reach threshold and send an action potential)

• Spatial summation

o 2 pre-synaptic neurons interact with 2 different regions on the neuron (at about  the same time) and they add together  

• Spatial summation of EPSPs and IPSPs

o 1 inhibitory and 1 excitatory neuron sends signal to the same post-synaptic  neuron and they cancel each other out

11.9 Learning objectives

Define neurotransmitter and classify neurotransmitters by chemical structure and function. Neurotransmitters

• “language of the nervous system”

• how neurons communicate with each other

• more than 50 neurotransmitters have been identified

• classified chemically and functionally

• excitatory vs inhibitory

o excitatory: cause depolarization

o inhibitory: cause hyperpolarization

• direct vs indirect

o direct: binds and open ion channels

o indirect: act through second messenger molecules (typically G-proteins) Examples of neurotransmitters

• Acetylcholine (AcH)

o Most abundant and common neurotransmitter

o Activates skeletal muscle 

o Helps with learning

o Binds to 2 kinds of receptors

▪ Nicotinic: always excitatory (located in CNS and hippocampus)

▪ Muscarinic: can be inhibitory or excitatory (located in PNS and in  

synapses with muscles)

• Norepinephrine

o Biogenic amines (derivative of amino acid)

o Associated with ANS

o Fight or flight: increases heart rate

o Excites brain

o “feel good” neurotransmitter

o not enough=depression

o 2 types of receptors

▪ alpha

▪ beta

• dopamine

o made in same pathway as norepinephrine

o “feel good” neurotransmitter

o has same effect as cocaine

o released during orgasm

o lack of it causes depression

• serotonin

o main association with depression: too little or too much causes depression ▪ Prozac (drug to treat depression): prevents presynaptic neuron from  reuptake to help keep serotonin levels up

o mainly inhibitory

o controls mood, sleep, hunger, etc 

• GABA, glutamate, and glycine

o Amino acids used as neurotransmitters

o Mostly in CNS

o GABA and glycine are inhibitory

o Glutamate is excitatory

• Endorphins

o Peptide

o Released during exercise

o “runner’s high”

o same effect as morphine

o numbs pain 

• ATP

o Energy molecule

o Activate class A receptors

o Signals pain

• Adenosine

o Signaling molecule

o Part of ADP

o Signals fatigue 

o Caffeine prevents adenosine from binding (so you do not feel fatigue) Describe the action of neurotransmitters at channel-linked and G protein-linked receptors. Neurotransmitter receptors

• Two types

o Channel linked (ionotropic) receptors

▪ Direct 

▪ Ligand gated ion channels

▪ Action is immediate and brief

▪ Only open as long as ligand is bound to the channel

▪ Properties of the pore itself regulates what ions can go through it

▪ Channels usually regulate what enters based on the size of the ion

▪ Excitatory receptors: receptors are channels that allow an influx of Na+  (depolarization)

▪ Inhibitory: receptors allow Cl- influx or K+ efflux (hyperpolarization)

o G-protein linked receptors

▪ Indirect 

▪ Uses second messenger systems 

▪ Not an ion channel or pore

▪ When activated, it activates a series of steps that can open up a channel  in the membrane

1. Neurotransmitter (1st messenger) binds and activates receptor

2. Receptor activates small G protein

a. Not embedded in the membrane

b. Loses a GDP and picks up GTP (energy source)

3. G protein activates adenylate cyclase

4. Adenylate cyclase converts ATP to cyclic AMP (cAMP) the 2nd 

messenger

5. cAMP changes membrane permeability by opening and closing  

ion channels

6. cAMP activates enzymes

11.10 Learning objectives

Describe common patterns of neuronal organization and processing.

Neurons are organized into neuronal pools, which are functional groups of neurons that: • Integrate incoming information

• Forward the processed information to other destinations

Simple neuronal pool

• Single presynaptic neuron fiber branches and has synapses with several neurons in the  pool

Types of circuits in neuronal pools 

• Diverging circuit

o 1 incoming fiber stimulates an increasing number of fibers

o may affect one or more pathways

o common in sensory and motor pathways

o also known as amplifying circuit

• converging circuit

o opposite of divergent circuit

o results in either strong stimulation or inhibition

o also common in sensory and motor systems

• reverberating circuit

o chain of neurons containing collateral synapses with previous neurons in the  chain

o usually common with basal processes (ex: breathing)

o perpetually activate themselves

• parallel after discharge circuit

o incoming fiber stimulates several neurons in parallel arrays to stimulates several  neurons in parallel arrays to stimulate a common output cell

Patterns of neural processing

• Serial: input travels along one pathway to a specific destination

• Parallel: input travels along several different pathways to be integrated in different CNS  regions

Distinguish between serial and parallel processing.

Patterns of neural processing

• Serial processing

o Ex: reflexes-rapid, auto-response to stimulus that always has the same response • Reflex arcs (pathways) have 5 essential components

o Receptor

o Sensory neuron

o Integration center

o Motor neuron

o Effector

• Parallel processing

o Input travels along several pathways

o One stimulus promotes numerous responses at the same time

o Important for higher level mental functioning

▪ Ex/ smell reminding you of something (pathways involve sensory parts of  the brain as well as memory center)

o Information comes in and moves to different regions of the brain

Learning objectives for chapter 12

12.1 Learning objectives

Describe how space constraints affect brain development.

In development

• starts as a hollow, fluid-filled tube

• all the nervous system will come from this

• as a fetus it starts becoming something

• secondary brain vesicles and what they will turn into

o telencephalon (new brain): cerebrum

o diencephalon (new brain): thalamus, hypothalamus, and epithalamus o mesencephalon (old brain): brainstem-midbrain

o metencephalon (old brain): brainstem-pons, and cerebellum

o myelencephalon (old brain): brainstem-medulla oblongata

• brain grows fastest during fetal development 

• brain grows faster than the skull growing around it so it folds up to save space and fit o folds result: sulci, gyri, and fissures

Name the major regions of the adult brain.

• 4 Brain regions

o cerebral hemisphere

o diencephalon

o brain stem

o cerebellum

Name and locate the ventricles of the brain.

• Ventricles

o fluid contained system of brain and spinal cord 

o 2 large ones in right and left hemispheres

o lateral ventricles produce cerebrospinal fluid

o lined by ependymal cells

o connects to 3rd ventricles which connects to cerebral aqueduct and the 4th ventricle

o apertures allow fluid to leave ventricles and surround brain

o brain is floating in cerebrospinal fluid

o they are all continuous with one another and the central canal of the spinal cord o 4 ventricles 

▪ 2 lateral ventricles-they are separated by the septum pellucidum (a thin  membrane)

▪ 3rd ventricle-in the diencephalon, communicates with the lateral  

ventricles by a channel called the interventricular foramen

▪ 4th ventricle-connected to the 3rd ventricle by the cerebral aqueduct

12.2 Learning objectives

List the major lobes, fissures, and functional areas of the cerebral cortex. • Cerebral hemispheres

o 83% of brain mass

o form superior part of brain

o gyri=elevated ridges

o sulci=shallow grooves

o fissures=deeper grooves

o 5 lobes

▪ temporal

▪ frontal

▪ parietal

▪ occipital

▪ insula

• cerebral cortex: where the conscious mind is found

o composed of gray matter (neuron cell bodies, dendrites)

o has 3 types of functional areas

▪ motor areas

▪ sensory areas

▪ association areas

Motor areas

• Primary motor cortex

o Large pyramidal cells of the precentral gyri

o Long axons-pyramidal corticospinal tracts  

o Allows conscious control of precise, skilled, voluntary movements

o Motor homunculi: upside down caricature representing motor innervation of  body regions (parts of the body with more neurons are represented as larger,  amount of cortex devoted to a body part is proportional to the amount of fine  motor control)

o Lateral inferior: jaw, tongue, lips, face

o Lateral: neck, thumb, fingers, hand

o Superior: hip, trunk, shoulder

o Medial superior: knee

o Medial inferior: toes

• Premotor cortex

o Regulates motor cortex 

o Anterior to precentral gyrus

o Controls learned/patterned motor skills

o Coordinates simultaneous/sequential actions

o Involved in planning of movements based on sensory input

• Broca’s area

o Pre-motor area for speech production 

o Anterior to the inferior region of the premotor area

o Present in one hemisphere (usually the left)

o Located in the dominant hemisphere

o Motor speech area: directs muscles of the tongue

o Is active as one prepares to speak

Sensory areas

• Each lobe associated with a sensory feature

• Parietal lobe

o Primary somatosensory cortex

▪ In postcentral gyri

▪ Receives sensory information

▪ Capable of spatial discrimination

▪ There is a homunculus for this as well

• Degree of fine difference is proportional to the size of the body  

part on the homunculus

o Somatosensory association cortex

▪ Does not include taste

▪ Posterior to the primary somatosensory cortex

▪ Integrates sensory input from the primary somatosensory cortex

▪ Makes sense of the information

• Occipital lobe

o Primary visual cortex 

▪ Receives visual information

o Visual association area

▪ Surrounds the primary visual cortex

▪ Use past visual experiences to interpret visual stimulus

▪ Complex processing involves entire posterior half of the hemisphere

• Temporal lobe

o Primary auditory cortex 

▪ Interprets information from inner ear as pitch, loudness, and location o Auditory association area

▪ Stores memories of sounds and permits perception of sounds

o Olfactory cortex 

▪ Medial aspect of temporal lobes

▪ Region of conscious awareness of odors

• Insula

o Gustatory cortex 

o Active when you are hungry

▪ association areas

• anterior association area

• posterior association area

• limbic association area

Multimodal association areas

• Receives input from multiple sensory areas

• Sends outputs to multiple areas, including premotor cortex

• Allows us to give meaning to information received and store it as memory, compare to  previous experience, and decide on action

• 3 parts

o anterior association area (prefrontal cortex)

▪ responsible for intellect, cognition, recall 

▪ contains working memory needed for judgment, reasoning, persistence,  and conscience

▪ development depends on feedback from social environment

o posterior association area

▪ larger region in temporal, parietal, and occipital lobes

▪ plays role in recognizing patterns and faces and localizing us in space ▪ involved in understanding written and spoken language (Wernicke’s area) o limbic association area

▪ part of limbic system

▪ provides emotional impact that helps establish memory 

• hippocampus, cingulate gyrus, parahippocampal gyrus, amygdala

Explain lateralization of cortical function.

lateralization of cortical function

• lateralization: division of labor between hemispheres 

• not everything is equal between the 2 hemispheres

• cerebral dominance

o designates hemisphere dominance for language

• left hemisphere (in righties): controls language, math, and logic

• right hemisphere: insight, visual-spatial skills, intuition, and artistic skills • left and right hemispheres connect by fiber tracts in cerebral white matter (corpus  callosum)

• corpus callosum can be cut to treat epilepsy

Differentiate between commissures, association fibers, and projection fibers. cerebral white matter

• corpus callosum(commissural fibers)

• association fibers

o connect gyri

o ex/ premotor common with primary motor cortex

• projection fibers

o travel up and down

Describe the general function of the basal nuclei.

basal nuclei (ganglia)

• subcortical nuclei

• functionally associated with subthalamic nuclei (diencephalon) and substantia nigra  (midbrain)  

• a functional group more than an anatomical one

• damage to it is associated with Huntington and Parkinson’s diseases • primary association with motor tasks 

• communicates with premotor cortex

12.3 Learning objectives

Describe the location of the diencephalon and name its subdivisions and functions. diencephalon

• 3 paired structures

o thalamus

o hypothalamus

o epithalamus-pineal gland

• encloses the 3rd ventricle

• thalamus- one on each side

o made of clusters of cell bodies

o relay information from sensory input to the correct sensory cortex o sensory information goes through here before getting to the cortex • hypothalamus 

o made of small nuclei

▪ autonomic control

o regulates things: heart rate, breathing, etc.

o communicates with amygdala

▪ center for emotional responses (pleasure fear, rage, etc)

o regulates sleep cycle

o controls release of hormones by the anterior pituitary gland

o produces posterior pituitary gland hormones

• epithalamus 

o most dorsal portion of diencephalon

o forms roof of 3rd ventricle

o pineal gland-extends from posterior border and secretes melatonin ▪ melatonin regulates sleep/wake cycle

o light during the day inhibits melatonin  

12.4 Learning objectives

Identify the three major regions of the brain stem and note the functions of each area. 3 regions:

• midbrain: corpora quadrigemina and cerebral aqueduct

• pons

• medulla oblongata

midbrain

• superior-most region of the brainstem

• cerebral peduncles

o contain pyramidal motor tracts

o function as a connection

o carry descending motor information 

o 80% of voluntary motor information goes through here

• cerebral aqueduct: channel between 3rd and 4th ventricles

• corpora quadrigemina of tectum

o made of 2 superior colliculi and 2 inferior colliculi

o reflex centers

o superior colliculi: visual reflexes

▪ ex/ turn head when you see something out of the corner of your eye o inferior colliculi: auditory reflexes

▪ ex/ you jolt and look around when you hear a loud bang

• superior cerebellar peduncles

o connect cerebellum to midbrain and transmits this information to higher  processing centers

pons

• forms part of the anterior wall of the 4th ventricle

• some nuclei of the reticular formation here help maintain the normal rhythm of  breathing

• has middle cerebellar peduncle

• has fibers of the pyramidal tract that are associated with the crus cerebri peduncles • pontine nuclei: cardio-respiratory centers exist to regulate breathing and heart rate medulla oblongata

• has 2 pyramids: ventral longitudinal ridges formed by pyramidal tracts • autonomic reflex centers

o cardiovascular center

▪ heart rate/force 

▪ blood vessel diameter

o respiratory centers

▪ generate respiratory rhythm 

▪ control rate and depth of breathing with pontine centers

o additional centers regulate

▪ vomiting

▪ hiccupping

▪ swallowing

▪ coughing

▪ sneezing

12.5 Learning objectives

Describe the structure and function of the cerebellum.

Cerebellum

• 11% of the mass of the brain

• subconsciously provides précising timing and appropriate patterns of skeletal muscle  contraction

• fine tunes motor movements in real time

• refines motor paths 

• smooth coordinated muscle contraction

• proprioception: awareness of body’s position and momentum

• recognizes and predicts sequences of events during complex movements • plays role in non-motor word association and puzzle solving

• anterior lobe=ventral surface

• posterior lobe=dorsal surface

• right side of cerebellum receives information from the right side of the body  (epsilateral)

12.6 Learning objectives

Locate the limbic system and the reticular formation and explain the role of each functional  system.

Functional brain systems

• Networks of neurons that work together and span wide areas of the brain o Limbic system

o Reticular formation

Limbic system

• Emotional or affective brain

o Amygdala: emotional center, recognizes angry or fearful facial expressions,  assesses danger, and elicits the fear response

▪ Helps store emotional memories

▪ Helps pick out appropriate emotion

o Cingulate gyrus: plays a role in expressing emotions via gestures, and resolves  mental conflict

o Hippocampus: memory 

▪ Vital role in learning

▪ If damaged, can’t learn new information. May be able to learn implicit  information like how to do things but not explicit information like  

someone’s name

• Puts emotional responses to odors

o Ex: skunks smell bad

Reticular formation

• Clusters of cell bodies in all 3 sections of the brain stem

• Three broad columns along the length of the brain stem

o Raphe nuclei 

o Medial group of nuclei 

o Lateral group of nuclei 

• Vital role in basic regulation (blood pressure, heart rate, breathing) • RAS (reticular activating system)  

o Sends impulses to the cerebral cortex to keep it conscious and alert o Filters out repetitive and weak stimuli (about 99% of all stimuli)

o Severe injury results in permanent unconsciousness (coma)

o has a role in helping keep you alert and conscious (when inhibited, you lose  consciousness)

• Motor function

o Helps control coarse limb movements

o Reticular autonomic centers regulate visceral motor functions

o Vasomotor

o Cardiac

o Respiratory centers

12.7 Learning objectives

Identify the brain areas involved in language and memory.

memory

• Storage and retrieval of information

• Two stages of storage

• Short-term memory (STM, or working memory)—temporary holding of  information; limited to seven or eight pieces of information

• Long-term memory (LTM) has limitless capacity

• Hippocampus helps in the conversion of information from short term to long term  memory

Identify factors affecting the formation of long-term memories.

• Factors that affect transfer from STM to LTM

o Emotional state: best if alert, motivated, surprised, and aroused

o Rehearsal: repetition and practice  

o Association: tying new information with old memories  

o Automatic memory: subconscious information stored in LTM

12.8 Learning objectives

Describe how meninges, cerebrospinal fluid, and the blood brain barrier protect the CNS. Protection of the brain

• Bone (skull)

• Membranes (meninges)

o Cover and protect the CNS 

o Protect blood vessels and enclose venous sinuses

o Contain cerebrospinal fluid (CSF)

o Form partitions in the skull

o Meningitis=inflammation of the meninges

o 3 layers

▪ dura mater: periosteal and meningeal layer

▪ arachnoid mater: loose covering, has fiber-like projections

• subarachnoid space: space between the arachnoid and pia  

maters, filled with cerebrospinal fluid

▪ pia mater: really tight on the cortex of the brain, delicate, fine

• Watery cushion (cerebrospinal fluid)

• Blood-brain barrier

o Helps maintain a stable environment for the brain  

o Separates neurons from some

o Composition

▪ Continuous endothelium of capillary walls

▪ Basal lamina

▪ Feet of astrocytes

▪ Provide signal to endothelium for the formation of tight junctions

Explain how cerebrospinal fluid is formed and describe its circulatory pathway. • Manufactured at the 2 lateral ventricles and the 4th ventricle

• Produce 150 mL per day

• Naturally generates pressure to push itself through the ventricle system • When it gets to the 4th ventricle it can…

o Keep descending to the central canal of the spinal cord and exit, then come back  up an ascending pathway

o OR it can go through an aperture and enter the subarachnoid space directly • Contains nutrients, sugar, oxygen, etc 

• Delivers nutrients to parts of the nervous system

• Somewhat dense (denser than water) so it allows the brain to float so that pressure is  not put on neurons on the bottom of the brain

• Cushions for protection-slows brain down so it does not ram into the skull and helps  prevent concussions

12.10 Learning objectives

Describe the gross and microscopic structure of the spinal cord.

• Begins at the foramen magnum and ends as conus medullaris at L1 vertebra • Provides two-way communication to and from the brain

• Contains spinal reflex centers

• Protection of the spinal cord

o Denticulate ligaments: extensions of pia mater that secure cord to dura mater o Filum terminale: fibrous extension from conus medullaris; anchors the spinal  cord to the coccyx

o 3 meninges cover the spinal cord

▪ difference from the brain in the dura mater: it has only the meningeal  layer (the brain has the periosteal layer also)

• Has 31 pairs of spinal nerves

• Cervical and lumbar enlargements: where the nerves serving the upper and lower limbs  emerge from

• Cauda equina: The collection of nerve roots at the inferior end of the vertebral canal Distinguish between flaccid and spastic paralysis, and between paralysis and paresthesia. Flaccid vs spastic paralysis

• Flaccid paralysis

o Occurs when the spinal cord or ventral roots are damaged

o Nerve impulses do not reach the muscle fibers

o Injury to the Lower Motor Neuron 

o No voluntary control of muscles

o No reflex activity

o Muscles atrophy

• Spastic paralysis

o Occurs when upper motor neurons of the primary motor cortex are damaged o Spinal motor neurons are intact and spinal reflex activity stimulates muscles o Muscles move but under involuntary control

o paralysis—Injury to Upper Motor Neurons 

o Muscles can be stimulated by reflex activity

o Muscle atrophy delayed

Functional losses

• Paresthesias: Abnormal sensation

• Paralysis: Loss of motor function

12.11 Learning objectives

List the key characteristics of neuronal pathways.

Ascending pathways

• Consist of three neurons 

o First-order neuron

▪ Conducts impulses from cutaneous receptors and proprioceptors

▪ Branches diffusely as it enters the spinal cord or medulla

▪ Synapses with second-order neuron  

o Second-order neuron

▪ Interneuron

▪ Cell body in dorsal horn of spinal cord or medullary nuclei

▪ Axons extend to thalamus or cerebellum

o Third-order neuron

▪ Interneuron

▪ Cell body in thalamus  

▪ Axon extends to somatosensory cortex

Descending pathways

• Involve two neurons:

1. Upper motor neurons

• Pyramidal cells in primary motor cortex

2. Lower motor neurons

• Ventral horn motor neurons

• Innervate skeletal muscles

Identify the major ascending and descending pathways.

Ascending pathways

• Dorsal Column-Medial Lemniscal Pathway: detects touch 

• Anterolateral pathways

o Lateral and ventral spinothalamic tracts  

o Transmit pain, temperature, and coarse touch impulses within the lateral  spinothalamic tract

• Spinocerebellar pathway

o Ventral and dorsal tracts

o Convey information about muscle or tendon stretch 

Descending pathways

• Pyramidal (lateral and ventral corticospinal) pathways

Learning objectives for chapter 13

13.5 Learning objectives

Describe the general structure of a spinal nerve and the general distribution of its rami. Structure

• Spinal nerves connect to the spinal cord by dorsal and ventral roots o Dorsal root

▪ Fans out into dorsal rootlets

▪ Contains sensory (afferent) fibers

▪ Has dorsal root ganglia

o Ventral root

▪ Derived from several rootlets

▪ Contains motor (efferent) fibers

▪ Motor neurons extend from here and innervate muscles

• They are short

• After emerging from its foramen it divides into:

o A small dorsal ramus 

o A large ventral ramus 

o A tiny meningeal branch

• Rami communicantes

o Special type of rami

o Contain autonomic nerve fibers

o Attach to the base of the ventral rami of the thoracic spinal nerves

Define plexus. Name the major plexuses and describe the distribution and function of the  peripheral nerves arising from each plexus.

• Plexus: complicated interlacing nerve network 

• Major plexuses

o Cervical plexus: head, neck and shoulders

o Brachial plexus: chest, shoulders, arms and hands

o Lumbar plexus: back, abdomen, groin, thighs, knees, and calves

o Sacral plexus: pelvis, buttocks, genitals, thighs, calves, and feet

o Coccygeal plexus: small region over the coccyx

Figure 13.13 in the textbook

• It is a map of dermatomes (become familiar with the general regions of it) • Dermatomes

o the area of skin innervated by the cutaneous branches of a single spinal nerve o Most dermatomes overlap, so destruction of a single spinal nerve will not cause  complete numbness

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