Nervous System Study Guide
Nervous System Study Guide BIO 161-22
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This 17 page Study Guide was uploaded by Erin Notetaker on Friday December 11, 2015. The Study Guide belongs to BIO 161-22 at La Salle University taught by David Rothblat in Summer 2015. Since its upload, it has received 59 views.
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Date Created: 12/11/15
Anatomy Final exam Study Guide CNS: Brain and spinal cord PNS: Everything outside of brain and spinal cord Efferent: Things that are running out (exit). Motor signals Afferent: Sensory neurons..They are going in. →Everything going in eyes, skin, etc. go in brain and it processes it to give signals. Nuclei: In CNS, group of neurons Ganglion: collection of neuron cell bodies in the PNS PNS Nucleus: collection of cell bodies in the CNS Glia: cells in the PNS Sensory Receptors: ending of neurons or specialized cells that detect such things as temperature, pain, touch, pressure, light, sound. Nerve: a bundle of axons and their sheaths that connects CNS to sensory receptors, muscles, and glands. Cranial nerves: originate from the brain; 12 pairs Spinal nerves: originate from spinal cord; 31 pairs Plexus: network of axons, and sometimes neuron cell bodies, located outside CNS. **In the PNS, most neurons have both sensory and motor neurons Motor Division of PNS Somatic nervous system: from CNS to skeletal muscles. Is voluntary and a single neuron system. Autonomic nervous system (ANS): From CNS to smooth muscle, cardiac muscle and certain glands. →Is under involuntary control and is a two neuron system. Divisions of ANS: 1. Sympathetic: Prepares body for physical activity. 2. Parasympathetic: Regulates resting or vegetative functions such as digesting food or emptying of the urinary bladder 3. Enteric: plexuses within the wall of the digestive tract. (controls digestive system) Functions of Nervous System -Sensory: Sense changes through sensory receptors -Motor: Respond to stimuli -Integrative: Analyze incoming sensory information and make decisions regarding appropriate behaviors Neurons Electrically excitable cellular structures -signals in myelinated axon are faster than those in unmyelinated axon. -Gaps in myelin are the Nodes of Ranvier -all signals from dendrites are collected in axon hillock. -Purkinje fiber is in cerebellum and functions in coordination. Functional Classification of Neurons -Sensory/afferent neurons -Motor/efferent neurons -Inter/association neurons Example of Sensory Receptor Nociceptor: pain receptor Neurons Dendrite: Receives signals Axon: sends signals down it Nodes of Ranvier: Unmyelinated gaps in myelinated axons (sodium potassium gates are here. When A.P. hits the nodes sodium goes in and potassium goes out) Hillock/trigger zone: Where the action potential starts Neuroglia -Not electrically excitable -Make up most of the volume of the nervous system -Can multiply and divide (neurons can’t) - 6 kinds total (4 in CNS, 2 in PNS) -When you damage neurons from trauma for example, it’s filled with glia. Myelin In the CNS they are oligo’s and wrap multiple axons In the PNS they are Schwann and wrap a single axon Neuroglia of the CNS Astrocyte: Cover the surfaces of neurons, blood vessels and the pia mater. Provide nutrients →Regulate what substances reach the CNS from the blood (blood-brain barrier). →The Blood Brain barrier regulates what goes in and what doesn’t in the CNS and also protects neurons from toxic substances. Ependymal Cells: Line brain ventricles. Some are on surface of choroid plexus. →Choroid Plexuses: within certain regions of ventricles. Secrete cerebrospinal fluid. →Meningitis is a viral infection in the CSF. Microglia: specialized macrophages that phagocytize →Usually become active in an inactive state such as a stroke. Oligodendrocytes: Form myelin sheaths surrounding multiple axons. Neuroglia of PNS Schwann Cells: wrap around portion of only one axon to form myelin sheath. Satellite cells: likes astrocytes but in PNS Myelination of Neurons -Myelin sheath is produced by Schwann cells and oligodendrocytes and it surrounds most axons. -Action Potentials: occur from opening and closing of sodium potassium channels. Myelinated Axons -Myelin protects and insulates axons from one another, speeds transmission, functions in repair of axons -contain Nodes of Ranvier - Degeneration of myelin sheaths occurs in multiple sclerosis and some cases of diabetes mellitus -Complete development of sheaths doesn’t occur until 1 yr which is why babies are uncoordinated. Unmyelinated Axons -Rest in invaginations of Schwann cells or oligodendrocytes. Wrapped around gray matter. Organization of Nervous Tissue Gray matter: unmyelinated axons and neuroglia and involved in integrative functions. White Matter: Myelinated axons in CNS. -In brain: gray is outer cortex as well as inner nuclei; white is deeper. -In spinal cord: white is outer, gray is inner. -PNS gray matter is groups of cell bodies called ganglia Electrical Signals in Neurons Begins with electrically excitable cells which come from resting membrane potential and communicate with each other via graded or action potential. - Action potentials: allow communication over short and long distances -Graded potentials: allow communication over short distances only Resting Membrane: Has positively charges ions of potassium on inside and negatively charged ions of sodium on outside. If sodium goes in it will become more positive, if potassium goes out it will be more negative. Only way to change potential is for things to move. →Determined by unequal distribution of ions across membrane and the permeability of the neuron’s membrane to potassium and sodium. → -70mv Ion Channels in Neurons Leakage channels: Randomly open and close Ligand Gated Channel: Needs a chemical ligand to attach to it too open. (Chemicals flow with concentration gradient) Mechanically Gated: Open in response to mechanical vibration or pressure. (Physical stimulation ex: tapping on fingers) Voltage Gated: Respond to direct changes in membrane potential. (Open if action potential come along) Changing Resting Membrane Potential Hyperpolarization: too much potassium exits. Potential becomes less polar Depolarization: allows sodium to come in. Goes from resting to membrane potential and the increases. Ex: resting membrane potential to threshold. →Polarization becomes more polar Repolarization: Going back and returning it to resting membrane potential. Potassium channels allow potassium to exit. →Returns to resting membrane due to sodium potassium pumps Graded Potentials A graded potential occurs in response to the opening of a mechanically-gated or ligand-gated ion channel. →Occurs in sensory neurons →The amplitude of a graded potential depends on the stimulus strength →Potentials can be added together to become larger in amplitude EPSP: When sodium goes in and moves above resting IPSP: Chloride goes in or potassium moves out. Moves below resting membrane →Calcium channels at the end are voltage-gated Action Potentials A sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarization) and eventually restore it to the resting state (repolarization). →Only occur if the membrane potential reaches threshold (greater frequency equals smaller stimulus and vice versa) Depolarization: goes from resting membrane and increases when sodium goes in Repolarization: when potassium exits, it becomes more negative. All or none Principle: No matter how strong stimulus is, as long as it is greater than threshold, an action potential will occur. If it doesn’t it threshold then an action potential will not occur. KNOW: -Neurotransmitter binds to ligand gated channel -If you drive membrane potential high enough, it will reach threshold -When potential hits synaptic bulbs it opens up voltage gated calcium channels. The calcium binds to vesicles and releases products through exocytosis. Synaptic button: activates calcium channels and binds to vesicles, then releases neurotransmitters Comparison of Action and Graded Potentials -Refractory periods are not present in graded potentials and can summate. In action potentials, they are present and cannot summate. -Graded potentials have ligand or mechanically gated ion channels. Action Potentials have voltage gated channels for potassium and sodium. Refractory Period Saltadory Conduction: When action potential jumps from node to node on the nodes of ranvier. (Occurs in myelinated axon and all of axon is covered n potassium and sodium) Continuous Conduction: Where the nerve travels down the whole unmyelinated axon →Once the signal is in refractory period it cannot go ack. It makes it so it can only go in one direction. TQ: What stops an axon from going backwards? A: Refractory period Absolute Refractory: occurs during depolarization when an action potential occurs Relative Refractory: occurs during hyperpolarization Factors that Affect Propagation Speed 1. Axon Diameter: bigger axons send signals faster 2. Amount of Myelination: Saltadory and continuous conduction Signal Transmission as Synapses Synapse: the junction between neurons or between a neuron and an effector. The space between a synaptic cleft. Chemical Synapse: One-way transfer of information from a presynaptic neuron to a postsynaptic neuron. (Most synapses in brain are these) Electrical Synapse: Gap junctions connect cells and allow the transfer of information to synchronize the activity of a group of cells Postsynaptic Potentials Excitatory postsynaptic potentials: Depolarizing postsynaptic potential. Sodium has to be let in for this to occur. →Reaches threshold producing action potential Inhibitory postsynaptic Potentials: Hyperpolarizing postsynaptic potential. Chloride has to be let in for this to occur. →Decrease action potential by moving membrane farther from threshold. Removal of Neurotransmitter Neurotransmitter can be removed from the synaptic cleft by: 1. Diffusion 2. Enzymatic degradation (MAO and acetylcholinesterase are used) 3. Uptake into cells Summation If several presynaptic end bulbs release their neurotransmitter at about the same time, the combined effect may generate a nerve impulse due to summation. -Can be: Spatial: Multiple neurons synapsing on one Temporal: One neuron sends pulses one after another Neural Circuit A functional group of neurons that process specific types of information. -Diverging and converging are some of the circuits that connect the brain Regeneration and Repair of nervous tissue -Neurons have a limited ability to regenerate themselves Plasticity: the capability to change based on experience →Memories form here and new connections. When you’re younger brain is plastic. Regenerate: The capability to replicate or repair. →Nervous system does not regenerate Neurogenesis in CNS -There is little or no repair in CNS but PNS can repair if the cell body is intact and Schwann cells are functional Chapter 13 Spinal Cord Functions of spinal cord -processes reflexes -integrate IPSP and EPSP -conduct sensory impulses to the brain and motor impulses to effectors Protection of Spinal cord -CSF: brings in nutrients (glucose and oxygen), is a shock absorber, is a cushion -Connective tissues (meninges) -vertebrae Meninges -Dura mater: outer layer -Arachnoid mater: middle layer -Pia mater: inner most layer that follows external contours (gyri and sulci) and is attached to brain. Anatomy of Spinal Cord -is a direct extension of the medulla oblongata -31 pairs of spinal nerves (they connect the CNS to sensory receptors, muscles, and glands and are part of PNS) White Matter: Has myelin and is on outside in the spinal cord. It sends info to and from the brain( info goes up and down) Gray Matter: Is the cell bodies and is on the inside and doesn’t have myelin. It integrates incoming and outgoing info to perform spinal reflexes. Descending: Getting info from brain and sending it out (motor) Ascending: Getting info from outside environment and bringing it to the brain (sensory) Dorsal Root: sensory info (afferent) Ventral Root: motor info (efferent) →The dorsal and ventral roots attach nerves to the spinal cord Commissure: connection between right and left halves →Corpus callosum: Connects right and left side of brain →Gray commissure joins right and left sides of spinal cord Dorsal root ganglion: collection of cell bodies of unipolar sensory neurons in posterior root of spinal nerve. →Motor neuron cell bodies are in anterior and lateral horns of spinal cord gray matter. Spinal Nerves Consists of: 1. Axon bundles 2. Schwann cells 3. Connective cells Endoneurium: surrounds individual neurons and axons Perineurium: Surrounds axon groups to form fascicles Epineurium: surrounds the entire nerve Dermatomes Corresponds nerves to a section or certain percentage of skin area on each side of the body. Reflex and Reflex Arcs Reflex: A fast, automatic response to changes in the environment that does not involve the brain. →Reflexes help maintain homeostasis →The spinal cord serves as the integration center for spinal reflexes. The integration takes place in the gray matter Sensory and Motor Neurons Motor Tract: A highway of organized neurons. Each tract carries its own info but the info is all the same on each own tract. →Lesion on corticospinal tract results in motor issues and results in having trouble walking. Components of Reflex Arc Goes from receptor →sensory→ interneuron (sensory neuron) → integration centec→ motor neuron→ effector muscle Reflex Arc Vocab Ipsilateral: Same side Contralateral: Opposite side Monosynaptic: 1 synapse Polysynaptic: multiple neurons Flexor Reflex: Moves a limb in response to pain Crossed-Extensor Reflex: maintains balance/ reflex →Reflexes are used to diagnose nervous system disorders because if the reflex is abnormal, there is a bigger neurological disorder along a conduction pathway. Babinski’s reflex: Stoke bottom of baby’s foot and toes fan out. Chapter 14 Protection Brain is protected by: 1. Cranial bones 2. Meninges (arachnoid and pia are thin, dura is thickest) 3. CSF Subdural space: space between dura and arachnoid mater Blood Flow to brain -The brain utilizes 20% of body’s oxygen. If there is blockage of oxygen or glucose it results in weakening, death of brain cells, dizziness, and unconsciousness Blood Brain Barrier Astrocytes make the blood brain barrier. -Regulates and prevents toxic substances from entering the blood in the brain CSF A liquid that protects the brain and spinal cord and carries oxygen and glucose to nervous tissue cells. -CSF flows to the ventricles -Contains choroid plexuses which are made up of ependymal cells that are made of neuroglia. →Choroid Plexuses make CSF CSF Flow: Lateral ventricle ↓ Third ventricle ↓ Fourth Ventricle ↓ Subarachnoid space ↓ Arachnoid villi of sinuses ↓ Heart and lungs Brain Stem -Medulla oblongata (inferior) -Pons (middle) -Midbrain (superior) -responsible for basic homeostatic functions (Heart rate, respiratory) Medulla Oblongata -Contains both motor and sensory tracts -contains pyramids: Primary motor cortex axons. (All neurons go through these pathways) Decussation of pyramids: where motor signals cross from right to left side and vice versa. -Medulla controls basic functions such as heart rate, vomiting, respiratory, and swallowing. Pons Relay center for info going from cerebellum to the brain. →Contains pneumotaxic and apneustic areas: control respiration (blood, co2, O2). They’re the fiber pathways going to cerebellum through the pons Midbrain Contains Substantia Nigra: Part of basil ganglia which helps to coordinate movements. (The area that is affected and dies in Parkinson’s disease) -Contains the Corpora Quadrigemina. The inferior and superior colliculi are located in the corpora quadrigemina and regulate auditory and visual reflexes. (When you hear or see something so you look) →Inferior is auditory and superior is visual Reticular foramen Loose plexuses scattered throughout brain stem that are responsible for maintaining consciousness and sleep schedules. Cerebellum -The two hemispheres are connected by the vermis -Responsible for Motor control, coordination, balance, muscle tone, and posture Diencephalon Composed of: thalamus and hypothalamus Thalamus: Relay station for all sensory impulses except smell. All things from body go to it and it will send things out to cerebral cortex. Hypothalamus: Connected to pituitary gland. Regulates many homeostatic balances and sends signals to pituitary gland telling it to release hormones. The Cerebrum -The cortex is located in the cerebrum -Cerebral cortex is composed of gray matter where gyri and sulci can be found at. (gyri and sulci increase surface area) Gray matter: cell/neuron bodies White matter: tracts of neurons that connect parts of the brain together and spinal cord. Corpus Callosum: connects the right and left hemispheres of the brain together by a bundle of white matter tracts. Lobes of the Cerebrum Temporal Lobe: Primary auditory cortex →Lateral Cerebral Sulcus: separates temporal from parietal..and frontal maybe Parietal lobe: Integration of sensation and many areas Frontal Lobe: Responsible for higher reasoning/decision making and social functioning →Central Sulcus: Separates parietal and frontal lobe Occipital Lobe: Primary visual area Pre central gyrus: Primary motor area. This is where all initiation to move occurs. Post central gyrus: primary sensory area. All sensory, prociception, pain, and touch occur here. Cerebral Medulla White matter between the cortex and nuclei Association fibers: connections within the same hemisphere but different parts of cortex Commissural fibers: connect one hemisphere to the other (Found in corpus callosum) Projection fibers: tracts that goes down the spinal cord and out. (Anything motor) →Are all myelinated because they are white matter →Pyramids are an example of projection fibers Basal Nuclei Gray matter that are motor Receptors. They are effected in Huntington’s and Parkinson’s disease -Contains substantia nigra Limbic System Involved in emotion and memory. Hippocampus: affected specifically in memory and Alzheimer’s disease Wernicke’s and Broca’s Area Wernicke’s: located in temporal lobe and is responsible for recognizing written and spoken language. (Speech recognition and helps you know how to read) →Damage: Can speak fluently but the sentences don’t make sense and you can’t read Broca’s: Located in the frontal lobe. It helps you be able to formulate speech and is the motor control of speaking. →Damage: Understand what people say and you know what you want to say but speech isn’t fluent and is gibberish. →Aphasia: A disorder that affects a person’s ability to communicate Hemisphere Lateralization Right hand writing occurs in left hemisphere and vice versa. Right hemisphere receives signals and controls muscles on left side of body. Cranial Nerves l. Olfactory: Smell, Sensory ll. Optic: Vision, Sensory lll. Oculomotor: Eye movement, Motor lV. Trochlear: Eye movement, Motor V. Trigeminal: Muscles of jaw and tongue, facial nerves, Both Vl. Abducens: Eye movement, Motor Vll. Facial: Sensory of face, Motor components of tongue, Autonomic response to salivary glands Vlll. Vestibulocochlear (Auditory): Ear and balance, Sensory lX. Glossopharyngeal: Swallowing, Motor X. Vagus: controls homeostatic functions such as liver, gall bladder, Sensory, Motor, Autonomic Xl. Accessory: Controls muscles of neck, Motor Xll. Hypoglossal: Controls muscles of tongue and palate, Motor TQ: Patient has paralysis in face, which nerves ae involved? A: Facial and trigeminal TQ: Can’t smell anymore, which nerves are affected? A: Olfactory TQ: Where development of nervous system being? In ectoderm called neural plate -Brain can’t be anaerobic respiration Chapter 15 Autonomic Nervous System Somatic Nervous System: Has both sensory and motor neurons. The effector and motor neurons innervate skeletal muscles. (The myelinated motor neuron extends from CNS to skeletal muscle fiber) Autonomic Nervous System: Receives input from sensory receptors. It is involuntary and involved in homeostasis in smooth muscle or the heart. ANS Contains two motor neurons: Preganglionic: cell body is in CNS (brain or spinal cord) and extends to autonomic ganglion. Postganglionic: Unmyelinated axon extends from ganglion to effector (cell body is in autonomic ganglion) Has two divisions: Sympathetic Nervous System: (Fight or Flight Division) leads to increased alertness and metabolism to be ready for emergency. →During this, Digestive system shuts down, pupils dilate, and heat rate increases. →Preganglionic neurons are in 12 thoracic and 2 or 3 lumbar. (Thoracic- lumbar) Parasympathetic Nervous System: (Rest and Digest Division) slows down body’s activity. →During this the digestive system is activated and heart rate decreases →Preganglionic neurons are in 4 cranial nerves and 2 or 4 sacral. (Cranial- sacral) Enteric Nervous System The nervous system of the digestive tract. -Is part of the ANS and has 10 million neurons ANS Neurotransmitters and Receptors -Systems are antagonistic to each other Sympathetic: Has a short preganglionic and long postganglionic. (EXCITATORY) -Preganglionic: uses acetylcholine on a nicotine receptor. -Postganglionic: uses norepinephrine on a beta/alpha receptor. Parasympathetic: Has a long preganglionic and short postganglionic (INHIBITORY) -Preganglionic: Uses acetylcholine on a nicotine receptor -Postganglionic: Uses acetylcholine on a muscarinic receptor Acetylcholine (Ach) -Binds to nicotinic and muscarinic receptors -nicotinic receptors on all ANS postganglionic neurons -excitatory when ACh binding occurs Norepinephrine Norepinephrine binds to 2 classes of receptors: -alpha adrenergic receptors (often excitatory) -beta adrenergic receptors (often inhibitory) Antagonistic effects of the two ANS systems Exerted through dual innervation of same effector -heart rate decreases (parasympathetic) -heart rate increases (sympathetic) Exerted because each division innervates different cells -pupillary dilator muscle (sympathetic) dilates pupil -constrictor pupillae (parasympathetic) constricts pupil Control of autonomic functions -Functions such as heart rate are controlled by autonomic reflex arcs (The arc is composed of same things as other reflex arcs learned) Drugs Sympathomimetics enhance sympathetic activity stimulate receptors or increase norepinephrine release Sympatholytics suppress sympathetic activity block receptors or inhibit norepinephrine release Example: Beta Blocker: Blood pressure medicine that relaxes blood vessels Parasympathomimetics enhance activity while parasympatholytics suppress activity **Nervous system is associated with all functions of the body and homeostasis Diseases of bone Parkinson’s disease: -Degeneration of the dopamine containing neurons in the Substantia Nigra (IN CNS) -Onset occurs between 50-60 but you can have early onset -Cause: idiopathic, although some cases may be due to environmental toxins from MPTP -Symptoms: rigidity, tremors in extremities and head, pill rolling with the fingers, masked face. -Treatment: MAO-inhibitors and L-dopa for ones with symptoms. MAO inhibitors degrade dopamine and norepinephrine -Most people die from complications of the disease Alzheimer’s disease -IN CNS -Aggregation of plaques (On outside of neuron) that contain beta-amyloid protein and neurofibrillary tangles (On inside of neuron) in the hippocampus. (Also in the limbic System?) -It is also seen in the atrophy of the cerebral cortex. -Diagnosis can only be confirmed on autopsy -Onset: Early onset begins at age 50 and first symptoms are memory loss of recent events -Symptoms: Patient becomes moody, confused, and paranoid. They may also lose the ability to read, write, eat, or talk. -Treatment: Aricept (cholinesterase inhibitor) which is only for those with symptoms ALS (Amyotrophic Lateral Sclerosis) -degeneration of spinal motor neurons due to the accumulation of neurotoxic levels of glutamate in the extracellular fluid. (IN CNS) -Loss of motor control leads to atrophy of muscles, sclerosis of lateral regions also occurs -Onset: 40-70 -Early symptoms: muscle weakness, difficulty speaking, swallowing, and moving hands. Rate of progression is variable. -Sensory and intellectual skill are not affected. -Treatment: Riluzole (glutamate antagonist) that slows progression Guillain-Barre Syndrome -Autoimmune disorder where immune system attacks myelin of peripheral nerves that is usually triggered by viral infection. -Begins with numbness and tingling of extremities progressing to muscle weakness. -No known cure. -IN PNS Shingles -Inflammation of nerves caused by activation of dormant varicella (chickenpox) virus. - Results in rash and blisters unilaterally -Maybe triggered by weakened immune system due to infection or aging or from stress -Treatment: Antivirals, vaccine (60 years)
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