Ch7 notes1

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Name________________________________Block_____Date______________________ Ch 7 The Nervous System Notes Lisa Peck I. Organization of the Nervous System (pp 222-224) Nervous system- the master controlling and communicating system of the body 3 functions: 1. sensory receptors to monitor changes occurring inside & outside body stimuli- changes sensory input- gathered information 2. processes and interprets the sensory input integration- nervous system makes decisions about what should be done 3. effects a response by activating muscles or glands (effectors) via motor output Regulating and Maintaining Homeostasis nervous system - fast-acting control via electrical impulses endocrine system- slow-acting control via hormones release into the blood Structural Classification (p 223) 2 subdivisions: Central Nervous System Peripheral Nervous System 1. Central Nervous System (CNS) consists of: brain spinal cord functions: integrating center ......... interpret incoming sensory information command center..........issue instructions based on past experience & current conditions 2. Peripheral Nervous System (PNS) consists of: nerves 2 types: cranial nerves- carry impulses to and from the brain spinal nerves- carry impulses to and from the spinal cord ganglia- groups of nerve cell bodies function: communication lines, linking all parts of the body

Transcript of Ch7 notes1

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Name________________________________Block_____Date______________________ Ch 7 The Nervous System Notes Lisa Peck

I. Organization of the Nervous System (pp 222-224)

Nervous system- the master controlling and communicating system of the body3 functions: 1. sensory receptors to monitor changes occurring inside & outside body

stimuli- changessensory input- gathered information

2. processes and interprets the sensory input integration- nervous system makes decisions about what should be done

3. effects a response by activating muscles or glands (effectors) via motor output

Regulating and Maintaining Homeostasisnervous system - fast-acting control via electrical impulsesendocrine system- slow-acting control via hormones release into the blood

Structural Classification (p 223)

2 subdivisions: Central Nervous System Peripheral Nervous System

1. Central Nervous System (CNS) consists of: brain

spinal cord

functions: integrating center.........interpret incoming sensory information command center..........issue instructions based on past experience & current conditions

2. Peripheral Nervous System (PNS) consists of: nerves 2 types: cranial nerves- carry impulses to and from the brain

spinal nerves- carry impulses to and from the spinal cord

ganglia- groups of nerve cell bodies

function: communication lines, linking all parts of the body

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Functional Classification (pp 223-224) 2only deals with peripheral nervous system (PNS)

1. Sensory (Afferent) Division- nerve fibers that carry impulses to the CNS from sensoryreceptors located throughout body

sensory fibers types: 1. somatic sensory fibers- delivering impulses from the skin, skeletal muscles, & joints

2. visceral sensory fibers- transmitting impulses from the visceral organs

2. Motor (Efferent) Division- nerve fibers that carry impulses from the CNS to effector organs ossicles and glands, bringing about a motor response

2 types: 1. somatic nervous system: conscious control of skeletal muscles voluntary control

skeletal muscles

2. autonomic nervous system (ANS)- regulates activities that are automatic involuntary

cardiac muscle smooth muscle glands

2 nerve types that target same organ but yield opp. effects exception: targeted only by sympathetic: some glands,

most blood vessels, most structures of the skin

2 types: 1. sympathetic-” fight or flight”f’ns during extreme situationsex: increase heart rate rapid breathing cold, sweaty skin dilated pupils

2. parasympathetic- “resting & digesting” most active when body at rest

causing normal digestion, voiding feces & urine goal: conserving energy

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Nervous Tissue: Structure and function (pp 224-235) 3

2 types of cells: 1. neuroglia- supporting cells not able to conduct impulses can undergo cell division most brain tumors are gliomas- formed by glial cells

2. neurons nerve cells that transmit impulses functional unit of nervous system

neurglia (pp 224-226) not able to conduct impulseglia (glial cells)- f’n: support, insulation, & protection ~90% cells in brain are glial cells

CNS: 4 types: astrocytes PNS: 2 types microglia schwann cells ependymal satellite cells oligodendrocytes

1. Astrocytes- star-shaped cells

account for over half of neural tissue numerous projections have swollen ends that cling to neurons f’n: 1. brace and anchor neurons to capillaries

intermediary cell b/w neuron and capillary (aids in exchange) protects neurons from harmful substances present in blood2. control chemical environment in brain by picking up excess ions & recapturing released neurotransmitters

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neurglia 4

2. Microglia- spiderlike phagocytes dispose of debris (dead brain cells & bacteria)

smallest of glial cells

3. Ependymal- line cavities of the brain & spinal cord f’n- beating of cilia helps circulate cerebrospinal fluid that fills cavities & forms protective cushion around CNS

4. Oligodendrocytes- (CNS) wrap their flat extensions around axons of many nerves forms myelin sheath- fatty insulating covering

protects and cushions nervesspeeds up nerve transmission speed

gives rise to white matter of brain

fewer extensions than astrocytes

PNS: 2 types:

1. Schwann cells- cells of PNS that myelinate axons2. satellite cells- protective & cushioning cells of PNS neurons

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B. Neurons (pp 226-235) 51. Anatomy (of a generalized neuron)

cell body- metabolic center contains typical cell organelles

(exception: no centrioles .....no mitosis -amitotic)

axon- one per cell, process of neuronconduct impulses away from the cell body

dendrites- many per cell, extension of neuron (often branched extensively) conduct impulses toward cell body

axon hillock- axon arises form this conelike region of cell body

axon terminals- 100’s to 1000’s branches at terminal end of axon contain vessicles of neurotransmitters

collateral branch- branch off of an axon

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Nerve Anatomy 6synaptic cleft (synapse)- separation b/w axon terminal and next neuron

myelin- covering of most long neurons (axon) whitish, fatty substance protects, insulates, speeds up neural transmission

CNS:oligodendrocytes- form myelin sheath

lacks neurolemma f’n- protects and cushions nerve increases speed of nerve transmission located in CNS

PNS:schwann cell’s form myelin sheath

covering of most long neurons formed by wrapping of a Schwann cell

schwann cell- specialized supportive cells wrap tightly around axon

neurolemma- outermost part of schwann cell aids in neuron regeneration

nodes of Ranvier- gaps of myelin sheathb/ w Schwann cellsloc. @ regular intervalsaction potential jumps fromnode to node- faster

CNS white matter- dense bundles of myelinated fibers (tracts) brain- inside spinal cord- surfacegray matter- unmyelinated fibers and cell bodies brain- surface spinal cord- inside

CNS PNSnuclei ganglia groups of cell bodies

tracts nerves bundles of nerve fibers

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Classification of Neurons 7functional classification- according to direction of impulse is traveling relative to CNS 1. sensory neuron- nerve impulse travels towards CNS

afferent cell bodies outside CNS in ganglion

receptors- dendrite endings that are specialized activated by specific changes nearby (stimuli)

taste, hearing, sight, equilibrium, smellcutaneous sense organs- pacinian & meissner corpusclesproprioceptors- loc. in muscles & tendons

detects amt. of stretch or tension determines location, posture, and tone

muscle spindle golgi tendon organs

pain receptors- bare dendrite endings least specialized cutaneous receptor most numerous cutaneous receptor

2. motor neuron- nerve impulse travels away from CNS efferent neuron

cell bodies inside CNS in nuclei

3. association neurons (interneurons)- connect motor and sensory neurons cell bodies in CNS

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Classification of Neurons 8structural classification- based on number of processes extending from cell body

multipolar- several processes all motor neurons all association neurons most common neuron type

bipolar- 2 process on cell body axon & dendrite rare in adults (eg; eye & nose)

unipolar- one process on cell body single process is very short process divides into 2 peripheral process- (distal)

contains dendrites on end central process- (proximal)

contains axon terminals axon- both peripheral & central

processes conducts impulses in both

directions (toward & away from cell body)

sensory neurons located in PNS ganglia are all unipolar

3. Physiology nerve impulse generation (action potential)reflex arcs- neural pathways involve both CNS & PNSreflexes- rapid, predictable and involuntary responses to stimuli

once reflex begins...always goes in same direction types: somatic reflexes- stimulate the skeletal muscles

eg: pull hand away from hot stove

autonomic reflexes- regulate the activity of smooth muscles, heart, & glands eg: secretion of saliva, changes in pupil size,

regulates: digestion, elimination, blood pressure, & sweating

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III. Central Nervous system (pp 235-249) 9

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Functional Anatomy of the Brain (pp 235-241) 10Brain- 3 parts1. forebrain- cerebrum

diencephalon- thalamus hypothalamus

2. midbrain- small superior part of brain stem

3. hindbrain- cerebellum brain stem (part of it)- medulla oblongata

pons

Forebrain2 parts: 1. cerebrum (cerebral hemispheres)

2. diencephalon

Cerebrum: largest part of brain divided into left and right hemispheres-cerebral hemispheresseparated by corpus callosum (internally)- large fiber tract connecting hemispheres

longitudinal fissure (surface)

the spinal tracts cross over -------> left hemisphere deals w/ right side of body right hemisphere deals w/ left side of body

surface is highly convoluted- increasing surface area (increases # of neurons)

cortex- (exterior) gray matter thin surface layer (1-4 mm thick)

Interior- white matter, nerve tract relaying impulses to & from cerebral cortex

gyrus (gyri)- elevated ridges on cerebral cortexsulcus (sulci)- shallow grooves in cortex fissure- deep sulcus in cortex sulci divide hemispheres into 4 lobes

separate large areas of brain frontal lobe

parietal lobe

occipital lobe

temporal lobe

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Functional Anatomy of the Brain (pp 235-241) 11

ForebrainCerebrum- cerebral cortex: 4 lobes f’n- speech, memory, logical & emotional response, consciousness, interpretation of sensation,

voluntary movement, problem solving frontal lobe primary motor area- located anterior to central sulcus

initiates voluntary movement of skeletal muscles (motor language too)

premotor area- located anterior to primary motor area process input regarding body movement, modify movements

prefrontal area- anterior frontal lobe higher level thought, decision making, planning, impulsivity control selective attention, personality, problem solving, behavior, emotions Broca’s area- inferior left frontal gyrus

controls facial neurons & speech production- articulation (works in junction with Wernicke’s Area- language comprehension)

parietal lobe somatic sensory area- located posterior to central sulcus

interprets input from sensory receptors (except specialized senses) aids in spacial orientation

sensory pathways are crossed pathways (left sensory area receives input from right side of body)

temporal lobe- auditory processing olfactory area (located deep temporal) memory: right lobe- visual memory (pictures, faces)

left lobe- verbal memory (words, names)

occipital lobe- visual center , processes visual info and visual recognition of shapes & colors

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Forebrain1. Cerebrum- “telencephalon”2. Diencephalon- located superior to brain stem & enclosed by cerebral hemispheres

3 parts- thalamus- relay station for sensory impulses passing upward to somatic sensory cortex all sensory input passes thru thalamus to cortex (except olfaction) signals from cerebellum pass thru thalamus up to motor area of cortex

encloses 3rd ventricle (spaces filled w/ cerebrospinal fluid...aids in circulation)

hypothalamus-”seat” of autonomic nervous system regulates homeostasis

both nervous & endocrine f’ns source of 8 hormones regulation of: body temp, water balance, blood chemistry, metabolism

heart rate, death results if damaged

plays imp. part in limbic system- “emotional-visceral brain” emotion, motivation

epithalamus- forms roof of 3rd ventricle choroid plexus- knots of capillaries w/ in ea. ventricle forms CSF pineal body- endocrine gland

releases melatonin- regulates daily body rhythms eg: day/ night cycle melatonin released @ night

Brain Stem- pathway for ascending & descending tracts, has gray areas- cranial nerveshelp control breathing, heart rate etc.

1. midbrain 2. pons 3. medulla oblongata reticular formation- extends length of brain stem (middle of hindbrain to midbrain)

role in consciousness & awake/ sleep cycles damaged- coma

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Midbrain 13 located upper part of brain stem very small portion of brain stem evolutionarily: the oldest part of brain only used for eye reflexes reticular formation- collects input from higher brain centers & passes it on to motor neurons substantia nigra- helps “smooth” out body movements damaged-Parkinson’s Disease ventral tegmental area (VTA)- loaded w/ dopamine-releasing neurons that are activated

by nicotinic acetylcholine receptors & synapse deep w/ in forebrain VTA involved in pleasure: nicotine, amphetamines & cocaine bind to and activate its dopamine-releasing neurons- may account for their addictive qualities

Hindbrain-consists of part of brain stem: 1. pons 2. medulla oblongata

3. cerebellum

pons- rounded structure protruding below midbrain unconscious control of breathing (reflexive breathing)

reticular formation- area receives sensory input from forebrain & passes to thalamus involved in sleep, arousal & vomiting

relay center b/w cerebral cortex (impulses from eyes, ears, & touch receptors) & cerebellum

medulla oblongata- closest to spinal cord most inferior part of brain stem f’n- regulation of heart beat, breathing, vasoconstriction (blood pressure),

reflex centers for vomiting, coughing, sneezing, swallowing, & hiccups

important fiber tract area damaged- death 4th ventricle lies posterior to medulla oblongata

cerebellum- second largest part of brain 2 convoluted hemispheres surface layer is gray matter and internal area is white matter f’n- muscle coordination maintain normal muscle tone & posture balance & equilibrium

Limbic System- receives input from association areas in cortex & passes signals cerebrum 2 parts: hippocampus- essential for formation of long term memories

amygdala- center of emotions (eg fear) send signals to hypothalamus& medulla wh/ can activate “fight or flight” receives signals form olfactory system....may account for powerful effect that odor has on memory

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Protection of the Central Nervous System (pp 241-244)

1. Bones of skull and vertebral column2. Meninges

dura mater- outermostarachnoid matter- middlepia matter- innermost

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Protection of the Central Nervous System (pp 241-244) 152. Meninges- 3 continuous sheets covering both spinal cord and brain

dura mater- outermost, pressed against bony surface on interior of vertebrae & craniumarachnoid mater- middle layer, weblike, threadlike extensions pass thru subarachnoid

space & attach to pia materpia mater- innermost layer, thin, attached to surface of spinal cord & brain

3. Cerebrospinal Fluid (CSF) fluid similar to blood plasma containing protein, vit. C, and ions bathes cells of CNS protecting them from physical trauma returns to blood thru veins drainging the brain choroid plexus- capillaries that secrete CSF

located hanging from roof of each ventricle ( 2 lateral, 3rd & 4th) CSF location

4. Blood-Brain Barrier

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C. Brain Dysfunctions (pp 244-247) 16 1. Traumatic Brain Injuries

concussion- reversible damagecontusions- nonreversible damage

2. Cerebrovascular Accidents (CVA)- strokevisual impairmentparalysisaphasias

3. Alzheimer’s Disease 4. Huntington’s Disease 5. Parkinson’s Disease 6. Diagnosis (pp 262-263) electroencephalogram (EEG) simple reflex tests angiography CT scans PET scans MRI & Functional MRI scans

D. Spinal Cord (247-249) ~17 inches from foramen magnum to L1 or L2 cauda equina- cord ends w/ spinal nerves @ L2 31 pairs of spinal nerves (dorsal & ventral roots)

Gray Matter of Spinal Cords & Spinal Roots gray matter in middle around central canal (H shape) 2 dorsal (post.) horns- contains interneurons connected to sensory neurons from dorsal root 2 ventral (ant.) horns- cell bodies of motor neurons whose axons leave via ventral root

White Matter of the Spinal Cord 3 regions anterior column: ascending tracts only (incoming sensory) lateral column: both ascending & descending posterior column: both ascending & descending

spinal nerve- fused dorsal & ventral roots (a mixed nerve- sensory & motor neurons) dorsal root: entering sensory neurons dorsal root ganglia- sensory nerve cell bodies ventral root: motor nerve axons

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Peripheral Nervous System (pp 249-263) 17 contain only nerves (no glial cells)Structure of a Nerve nerve- bundle of neuron fibers (held tog. w/ connective tissue) endoneurium- surrounds each never fiber perineurium- binds groups of fibers into fasicles epineurium- bind fascicles together

12 Pairs of Cranial Nerves numbered in order from front to back most are mixed nerves (3 sensory only)

I olfactory sensory 4 smell

II optic sensory 4 vision

III oculomotor motor fibers to eye muscles

IV trochlear motor fibers to eye muscles

V trigeminal sensory 4 face motor fibers to chewing muscles

VI abducens motor fibers to eye muscles

VII facial sensory 4 taste motor fibers to face

VIII vestibulocochlear sensory 4 hearing & balance

IX glossopharyngeal sensory 4 taste motor fibers to pharynx

X vagus sensory & motor 4 pharynx, larynx, & viscera

XI accessory motor nerve to neck & upper back

XII hypoglossal motor fibers to tongue

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31 Pairs of Spinal Nerves and Nerve Plexuses 18

spinal nerves formed by combo of venrtral & dorsal roots of spinal cordspinal nerves named for region from which they arise

spinal nerves divide after leave spinal cord dorsal rami- serve skin & posterior trunk muscles ventral rami- form plexus for the anterior

plexuses- ventral rami of spinal nerves form complex networks that serve motor & sensory needs of limbs 4 plexus: cervical, brachial, lumbar, & sacral

classification of nerves by direction of impulse mixed nerve- travels to & from CNS inlcudes both sensory and motor nerve fibers sensory nerve- carry impulse towards CNS (afferent) motor nerve- carry impulse away from CNS (efferent)

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Autonomic Nervous System 19

somatic & autonomic nervous systems compared Somatic NS Autonomic NS

Nerves one motor neuron preganglionic nerves postganglionic nerves

Effector Organs skeletal muscle smooth muscle cardiac muscle glands

Neurotransmitters always use acetylcholine acetylcholine epinephrine norepinephrine

Autonomic Nervous System: involuntary control 2 divisions that serve same effector (smooth or cardiac muscle or a gland)

2 divisions bring about opposite effects, coutner balance ea. other

major difference 1) location of origin in CNS parasympathetic- brain stem or S1-S4

sympathetic- T1-L2

2) location of ganglia parasympathetic- ganglia near spinal cord

sympathetic- ganglia near effector organ

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Autonomic Nervous System 20 Parasympathetic division (PaNS)“housekeeping activities”conserves energymaintains daily necessary body functions“D” division: digestion, defecation, and diuresis

constricts pupilsconserve Estimulates digestive (increase saliva) stimulates urinary organs (increase urine production)inhibit cardiovascular system (slow heart rate)inhibit respiratory systems (constrict airways, slow respirations)

Sympathetic division (SyNS)“fight-or-flight” response to unusual stimulustakes over to increase activities“E” division: exercise, excitement, emergency, & embarrassment

pupils dialatestimulate respiratory organs (increase breathing rate & open airways)stimulate cardiovasculary system (increase heart rate)stimulate adrenal glands (release epinephrine and norepinephrine...stimulate liver)stimulated liver (convert glycogen into glucose....release into blood)inhibit digesitve system (decrease saliva...dry mouth)inhibit urinary system

increase glucose use....generates heat and water...increase sweat, reddened skin

polygraph- measures stress incurred when tell a lie. You know it is wrong to lie, when you do lie your sympathetic NS kicks in and your adrenal glands cause heart rate to increase.

measures changes in heart rate

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Developmental Aspects of the Nervous System (pp 263-266) 21

nervous system if formed during the first month of embryonic development

any maternal infection can have extremely harmful effects

the hypothalamus is one of the last areas of the brain to develop it controls body temperature: premature babies and infants can not maintain body temp

there are no more neurons formed after birth, but growth and maturation continues for several yearsneurons will develop myelination during maturation- increases neuromuscular control

the brain reaches maximum weight as a young adult

A. Embryonic Brain Developmentcerebral palsyanencephalyhydrocephalusspina bifida

B. Premature Infantstemperature regulation via hypothalamus