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ICSE Nervous System Notes 2018 : Biology (St. Xaviers School, Belguma, Purulia)

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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 Functional Classification 2 (pp 223-224) only deals with peripheral nervous system (PNS) 1. Sensory (Afferent) Division- nerve fibers that carry impulses to the CNS from sensory receptors 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 situations ex: 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 Nervous Tissue: Structure and function (pp 224-235) 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 not able to conduct impulse glia (glial cells)- f n: support, insulation, & protection (pp 224-226) CNS: 4 types: astrocytes microglia ependymal oligodendrocytes ~90% cells in brain are glial cells PNS: 2 types schwann cells satellite cells 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 blood 2. control chemical environment in brain by picking up excess ions & recapturing released neurotransmitters 3 neurglia 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 nerves speeds 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 axons 2. satellite cells- protective & cushioning cells of PNS neurons 4 B. Neurons (pp 226-235) 1. 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 neuron conduct 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 5 Nerve Anatomy synaptic cleft (synapse)- separation b/w axon terminal and next neuron 6 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 sheath b/ w Schwann cells loc. @ regular intervals action potential jumps from node to node- faster CNS white matter- dense bundles of myelinated fibers (tracts) gray matter- unmyelinated fibers and cell bodies CNS nuclei PNS ganglia groups of cell bodies tracts nerves bundles of nerve fibers brain- inside spinal cord- surface brain- surface spinal cord- inside Classification of Neurons functional 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 7 receptors- dendrite endings that are specialized activated by specific changes nearby (stimuli) taste, hearing, sight, equilibrium, smell cutaneous sense organspacinian & meissner corpuscles proprioceptors- 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 Classification of Neurons structural classification- based on number of processes extending from cell body 8 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 & PNS reflexes- 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 III. Central Nervous system (pp 235-249) 9 Functional Anatomy of the Brain (pp 235-241) Brain- 3 parts 1. forebrain- cerebrum diencephalon- thalamus hypothalamus 2. midbrain- small superior part of brain stem 10 3. hindbrain- cerebellum brain stem (part of it)- medulla oblongata pons Forebrain 2 parts: 1. cerebrum (cerebral hemispheres) 2. diencephalon Cerebrum: largest part of brain divided into left and right hemispheres-cerebral hemispheres separated 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 cortex sulcus (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 Functional Anatomy of the Brain (pp 235-241) 11 Forebrain Cerebrum- 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 12 Forebrain 1. 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 nerves help 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 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 neuronsmay 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 14 Protection of the Central Nervous System (pp 241-244) 1. Bones of skull and vertebral column 2. Meninges dura mater- outermost arachnoid matter- middle pia matter- innermost Protection of the Central Nervous System (pp 241-244) 15 2. Meninges- 3 continuous sheets covering both spinal cord and brain dura mater- outermost, pressed against bony surface on interior of vertebrae & cranium arachnoid mater- middle layer, weblike, threadlike extensions pass thru subarachnoid space & attach to pia mater pia 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 C. Brain Dysfunctions (pp 244-247) 1. Traumatic Brain Injuries concussion- reversible damage contusions- nonreversible damage 2. Cerebrovascular Accidents (CVA)- stroke visual impairment paralysis aphasias 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 16 Peripheral Nervous System (pp 249-263) 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 17 31 Pairs of Spinal Nerves and Nerve Plexuses spinal nerves formed by combo of venrtral & dorsal roots of spinal cord spinal 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) 18 Autonomic Nervous System 19 somatic & autonomic nervous systems compared Somatic NS Nerves Autonomic NS 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 Autonomic Nervous System Parasympathetic division (PaNS) housekeeping activities conserves energy maintains daily necessary body functions D division: digestion, defecation, and diuresis 20 constricts pupils conserve E stimulates 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 stimulus takes over to increase activities E division: exercise, excitement, emergency, & embarrassment pupils dialate stimulate 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 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 years neurons will develop myelination during maturation- increases neuromuscular control the brain reaches maximum weight as a young adult A. Embryonic Brain Development cerebral palsy anencephaly hydrocephalus spina bifida B. Premature Infants temperature regulation via hypothalamus

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