Human Anatomy and Physiology, Week 11-14
Human Anatomy and Physiology, Week 11-14 BIOL 312
Edinboro University of Pennsylvania
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This 19 page Class Notes was uploaded by Caitlyn Wiercioch on Wednesday August 24, 2016. The Class Notes belongs to BIOL 312 at Edinboro University of Pennsylvania taught by Matthew J. Foradori in Fall 2016. Since its upload, it has received 5 views.
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Date Created: 08/24/16
Anatomy and Physiology Exam 3 Notes Chapter 12: The Nervous System 1. Major Functions a. Detect changes in internal and external environment b. Interpret those changes c. Respond to interactions by stimulating muscle contractions or gland secretion d. Nervous System: most rapid means of main homeostasis 2. Nervous System Organization- 2 areas a. Central Nervous System (CNS)- brain and spinal cord= control center b. Peripheral Nervous System (PNS) i. Nerve processes-> connect CNS to receptors, muscles, & glands ii. PNS: 2 parts 1. Afferent System *towards* a. AKA sensory neurons b. Nerve cells that relay information from receptors -> CNS 2. Efferent System *from* a. AKA motor neurons b. Nerve cells that relay information from CNS -> muscles & glands c. Efferent system / into: i. Somatic N.S. 1. Soma=body 2. Efferent neurons & skeletal muscle 3. Voluntary conscious control ii. Autonomic N.S. (ANS) 1. Efferent neurons- glands, cardiac & smooth muscle 2. Involuntary control 3. ANS / into: a. Sympathetic NS- usually stimulates glands & muscles: F or F b. Parasympathetic NS- usually inhibits glands & muscles: rest and repose 3. N.S. Histology a. 2 Cell types i. Neurons 1. “Nerve cells” 2. Primary functions: a. Produce & conduction of electricity b. Controlling muscle & gland activity c. Thinking ii. Neuroglial cells (glial=glue) 1. Support, protects, & nourish neurons 2. 5:1 (neuroglial:neurons) b. Neurons i. Cell Body 1. AKA perikayron 2. Nucleus & organelles 3. Housekeeping area a. NISSL bodies i. Layers of RER ii. Important in protein synthesis that allows for nerve growth & regeneration of nerve fibers 4. Cell bodies in CNS are grouped into “nuclei” 5. Cells bodies in PNS are grouped into “ganglia” ii. Dendrites (Dendron=tree branch) 1. Highly branched, thick extensions of cytoplasm off of cell body 2. Normally 7 per neuron 3. Information receptor area (important in carrying impulses towards the cell body) iii. Axon 1. Single, long, thin, highly specialized cytoplasm extension off of cell body 2. Carries impulses away from cell body 3. General info a. Axon length- 1mm (in brain) – 1m (toes to spinal cord) b. Axon collaterals- side branches off main axon c. Synaptic Vessels i. AKA boutons ii. Bulblike structure of terminal axon with synaptic vesicles iii. Store chemical neurotransmitters d. Nerve fibers- axon & sheath 4. Axons & Sheaths a. Large PNS axons are encased in white phospholipids layers of myelin “myelinated axons” i. Functions: 1. Increases speed of electrical transmission 2. Protects & insulates axon ii. PNS myelin=produced from Schwann cells=neuroglial cells 1. Flat cells that encircle axon and overlap each other 2. Neurilemma= outer layer of Schwann cells b. Large CNS axons i. Coated with myelin: same 2 functions ii. BUT oligiodendrocytes= neuroglial cells, produces it (NOT SCHWANN) c. Nodes of Ranvier i. Unmyelinated axon regions where impulses “jump” from node to node ii. AKA salutatory conduction iii. Speed=225 mph in myelinated vs 75 mph in unmyelinated d. PNS axons can regenerate due to Schwann cells activity (neurilemma) e. CNS axons cannot regenerate after damage (no neurilemma) f. Myelin Sheaths i. Begins in fetus & increase from birth ->20 yrs 1. White matter= myelinated CNS axons 2. Gray matter= unmyelinated CNS axons ii. Gradual increase in coordination of effectors until 20 iii. Multiple Sclerosis (MS) 1. Chronic 2. Destruction of myelin sheaths of CNS 3. Results in disruption of impulse coordination iv. Structural classification of neurons- based on # of processes extending from cell body 1. Multipolar a. Several dendrites & 1 axon b. Primarily CNS 2. Bipolar a. 1 dendrite & 1 axon b. Primarily retina, inner ear, nose 3. Unipolar a. 1 process, divided i. Central branch= axon & peripheral branch= dendrite b. Primarily in spinal & cranial nerves v. Nerve= collection of axons outside the CNS 1. Most are “mixed”; contain sensory & motor fibers vi. Neuroglial cells- 6 types 1. Schwann cells- myelin sheath around PNS 2. Oligodendricytes- myelin sheath around CNS 3. Microglia- phagocytes in CNS 4. Ependyma- covers ventricles of brain & central canal of spinal cord 5. Satellite cells- support PNS cell bodies 6. Astrocytes- regulate external environment of CNS neurons vii. Astrocyte & Blood-Brain Barrier (AKA BBB) 1. Regulates passage of molecules from blood -> brain via brain capillaries + astrocytes forming tight junctions: a continuous basement membrane forms 2. Examples: a. ROH (alcohol), glucose, O2 + certain ions cross BBB rapidly by active transport b. Urea, insulin, sucrose- pass slowly through BBB c. Dopamine, protein, antibiotics- do not pass 4. Nerve Impulse a. Resting membrane potential ~ -65 to -85 mc; primarily due to: i. Large, non-disfusable, (-) charged proteins & ions inside ii. Unequal distribution of Na+ & K+ } via Na/K pumps in membrane 1. Na+= 14x more concentrated outside 2. K+= 30x more concentrated inside b. Irritability i. Ability to produce and conduct changes in membrane potential 1. = impulse 2. Only muscle and nerve cells ii. Stimulus = change in environment of sufficient strength to cause an impulse iii. Resting membrane is “polarized” = charge difference occurs across membrane iv. Strong stimulus applied 1. Membrane permeability to Na+ is increased, Na+ channels open & Na+ rushes in; the polarized membrane (-70 mv) becomes depolarized (0 mv) and will become + (+30 mv) 2. Once depolarization has occurred an action potential (nerve impulse) is initiated = last 1 msec v. Stimulated (-) point on the outside of the membrane sends out an electrical current to the adjacent (+) pt. (still polarized) 1. It depolarizes from -70 mv -> +30 mv 2. The reversal occurs over and over vi. Repolarization 1. Resting membrane potential is restored 2. Membrane = now more permeable to K+ & impermeable to Na+ 3. K+ leaves through K+ gates or channels; outersurface is more (+) and inside is more (-) 4. Eventually thru Na/K pump, the proper ion ration and distribution is achieved vii. Refractory Period 1. Time needed to repolarize membrane 2. If another stimulation occurs during repolarization, no impulse occurs c. Common Terms and General Information i. Sensory neurons- primarily stimulate at distal end by receptors ii. Motor neurons- primarily stimulated at dendrites by other neurons iii. Impulses travel: dendrites -> cell bodies -> axons iv. Threshold stimulus- any stimulus strong enough to generate an impulse v. Subthreshold stimulus- any stimulus weaker than threshold stimulus; no impulse vi. Summation- a series of subthreshold stimulus over a short period of time that generate an impulse vii. All or None Principle- if a stimulus is strong enough to cause an impulse, then it [impulse] is conducted along the entire neuron at a constant and maximal strength, impulse is “self-propagating” or “conducted with determent” d. Synaptic Transmission i. Impulses conducted from one neuron to another or to an effector cell ii. Synapse= junction or gap iii. Learning and many diseases are synaptic phenomena iv. Definitions 1. Presynaptic neuron- occurs before synapse 2. Postsynaptic neuron- occurs after synapse 3. Neuromuscular (myoneural) synapse- b/w neuron and muscle v. Synapse classification 1. Axodendritic a. Presynaptic axon synapses w/ postsynaptic dendrites b. Most common 2. Axosomatic a. Presynaptic axon synapses w/ postsynaptic axon 3. Axoaxonic a. Presynaptic axon synapses with post synaptic axon vi. Synapses 1. Allows for only one-way impulse transmission 2. Presynap-> postsynaptic tissue e. Neurotransmitters i. Chemicals (usually amino acids) released from presynap ii. Synaptic knobs that conduct impulses across the synapse f. Synaptic Vesicles- small membrane sacs that contain 10,000-100,000 neurotrans molecules 5. Mechanism of Synaptic Impulse Transmission a. Presynap. Nerve impulse arrives at synaptic knob & Ca++ enters the knob b. Ca++ stimulates synaptic vesicles to migrate and fuse with synaptic knob membrane by activating enzymes c. Neurotransmitters are released via exocytosis d. Neurotransmitters diffuse across the synaptic cleft (gap) & bind to postsynaptic membrane e. ~0.5 msec for entire mechanism f. One of the 7URAL events can occur based on type of neurotransmitters released Acethycholine (ACH) o AKA Cholinergic Synapses o Used in CNS, somatic motor neurons, neuromuscular junctions, ANS o Modes of actions: 1) Once released, diffuses across synaptic gap and binds to receptors on postsynaptic cell 2) Binding increases cell permeability to Na+ and K+ by opening gates; gates are chemically regulated 3) Depolarization occurs which may stimulate voltage regulated gates to open in the axon; generates an action potential 4) Acethycholinesterase- on postsynaptic membrane, degrades ACH, control mechanism o Nerve gas inhibits acethycholinesterase stimulation of muscle -> convulsions o Curare (poison arrows) competes with ACH for receptors (blocks ACH from postsynaptic receptors); decreases muscle (diaphragm) contractions Motor end plate= somatic motor nerve ending and postsynaptic muscle cell ACH promotes End Plate Potentials- depolarization of muscle cell membrane Unlike action potentials, end plate potentials have no thresholds; graded responses occur= as more ACH is released, more depolarization occurs; different from all or none response Summation- increase muscle contraction due to adding up graded response o ACH-Neuron-Neuron Synapses-CNS 1) Axon synaptic knobs release ACH -> interacts with dendrites and cell body to open chemically regulated Na+, K+, gates -> depolarization= “Excitatory Postsynaptic Potential” (EPSP) 2) Voltage regulated gates begin at axon Hillock -> axon 3) If EPSP’s are at or above threshold stimulus when they reach Hillock area, an action potential occurs If EPSP’s are below threshold, no action potential occurs Summation- a neuron can have up to 1000 synaptic inputs from other neurons; summation of EPSP occurs, allows postsynaptic neuron to “weight”; different combos of inputs Spatial Summation- EPSP’s from different presynaptic neurons add up in postsynaptic dendrites & axons -> depolarization Temporal Summation- 1 presynaptic knobs fire 2 or 3 times faster Catecholamine’s o AKA Adrenergic Synapses o Class of CNS neurotransmitters= include dopamine, epinephrine & norepinephrine o Mode of action: 1) Under proper stimulation, Ca++ diffuses into presynaptic knob 2) Ca++ causes synaptic vesicles to migrate and fuse with synaptic knob membrane by activating enzymes 3) Catecholamines- released via exocytosis 4) Catecholamine enters synaptic cleft and several events occur based on the type of catecholamines released 5) Catecholamines bind to postsynaptic membrane receptors & activates adenylate cyclase which converts ATP-> CAMP 6) CAMP activates protein kinases 7) Kinases phosphorylates chemical regulated gates; they open; Na+ and K+ diffuse and depolarization occurs= “short term effects”; EPSP chemicals 8) “Long term” kinase stimulates regulatory protein to move from cytoplasm to nucleus and bind to DNA (DNA -> pre mRNA -> mRNA -> protein synthesis) o Inactivation of Catecholamines: after exocytosis 1) Catecholamines- reabsorbed from synaptic gap into presynaptic knob – primary means of inactivation 2) Catecholamines- degraded in presynaptic neuron endings by monoamine oxidase (MAO) 3) Catecholamines- degraded in postsynaptic neuron by catecholamine-o-methyltransferase (COMT) o MAO inhibitory drugs- increase the effectiveness of catecholamines; used to control psychotic and emotional depression o Parkinson’s disease- degeneration of neurons that secrete dopamine in substantia nigra region of brain -> muscle tremors, speech impairment, chronic; L-Dopa given to increase dopamine production; fetal nerve implants, cell implants o Cocaine- blocks reuptake of dopamine by presynaptic axon; overstimulation of neural pathways; initial euphoria then depression, withdrawal, addiction o Alzheimer’s- primary form of madness in elderly; chronic degeneration of ACH-secreting neurons in CNS; drugs given to inhibit acetylcholinesterase o Norepinephrine- catecholamines used in PNS & CNS neurotransmitters -> increase in arousal; amphetamines stimulate pathways that use norepinephrine. Amino Acid Neurotransmitters o 1) Excitatory- glutamic acid, aspartic acid= EPSP’s (ACH, catecholamines) in CNS o 2) Inhibitory- glycine, GABA -> hyperpolarizes postsynaptic membrane, decrease from -70 mV to -85 mV a) AKA inhibitory postsynaptic potential (IPSP) b) leads to postsynaptic inhibition c) IPSP’s and EPSP’s inputs can summate at postsynaptic neurons; determine if an impulse is generated o GABA- a derivative of glutamic acid; primary neurotransmitter of brain (1/3 of all neurons); -> IPSP’s; important in muscle control and emotions o Huntington’s Chorea- reduced GABA -> uncontrolled muscle spasms and emotions Chapter 13 & 14: Central Nervous System CNS: brain and spinal cord 1. Functions: a. Receives inputs from sensory neurons b. Direct activity of motor neurons c. Allow for learning, memories and communication 2. Association Neurons= w/in CNS, control motor responses with sensory stimuli; maintain homeostasis 3. Weights ~= 3 lbs. in adult 4. Mushroom-shaped 5. Brain formed by about 4 week after conception 6. Fetal brain formation and divisions th a. Prosencephalon- forebrain; by 5 week; divided into: i. Diencephalon ii. Telencephalon b. Mesencephalon- midbrain c. Rhombencephalon- hindbrain; by 5 week; divided into: i. Myelencephalon ii. Metencephalon 7. Fetal divisions give rise to adult brain structure 8. Protection and coverings a. Cranial bones of the skull- protect brain b. Vertebrae- protect spinal cord c. Cranial and spinal meninges- membranes; protects CNS i. Dura mater -> outer layer ii. Arachnoid -> middle layer iii. Pia mater d. Cerebrospinal fluid i. Bathes CNS ii. ~= 125 mL, clear fluid iii. Contains proteins, glucose, urea, salts, WBC iv. Serves as a “shock absorber” and to circulate nutrients 9. Blood supply a. Enormous amount to -> brain b. Brain = 2% body weight, yet uses 20% of oxygen and glucose of entire body c. Amount varies with degree of mental activity d. Brain cell lacking oxygen for 4 minutes are permanently injured e. Glucose is primary energy source II. Brain structure and function 1. Cerebrum a. Arises from telencephalon i. 80% weight of brain ii. Divided into right and left hemispheres iii. Connected by corpus callosum iv. Outer cerebral cortex region = 2-4 mm thick, made of gray matter (cell bodies and dendrites) b. Surface i. Folded= gyri and grooved= sulci ii. Increases surface area c. Fissures- divide each hemisphere into 5 lobes i. Frontal lobe 1. Anterior 2. Composed of gyri 3. Pre-central gyrus- involved in motor control 4. Body regions with highest density of sensory receptors (hands, face) occupy the largest area of gyrus 5. Primary olfaction center (smell) ii. Parietal lobe 1. Separated from frontal by central sulcus 2. Post-central gyrus- perceives somatesthetic sensations- from cutaneous muscle, tendons and joint receptors 3. Primary gustatory area- taste iii. Temporal Lobe 1. Primary auditory area 2. Interprets pitch and rhythm 3. Auditory association area a. Determines if sound is speech, music, voice b. Interprets meaning of speech by translating words into thought iv. Occipital Lobe 1. Primary visual area 2. Interprets shapes and color 3. Visual association area a. Relates present image with past visual experiences b. Evaluates what is seen v. Insula lobe 1. Deep to parietal lobe 2. Common integrative center for visual, auditory, taste, smell, and somethetic area so that common thought is produced 3. Transmits signals to other areas of brain to produce response d. Brain scans i. CAT scans- “computed assisted topography”- map of brain ii. PET scans- “positron emission topography”- radioactive glucose used to see what areas are active iii. EEGs- electroencephalograms- measure cerebral cortex action potentials 1. Detect tumors, epilepsy, brain death 2. 4 different waves: a. Alpha i. Arises from parietal and occipital lobes ii. 10-12 waves/sec in awake, normal adult iii. Absent during sleep b. Beta i. Frontal lobes ii. 15-60 waves/sec iii. Increases during sensory input or mental activity c. Theta i. Temporal and occipital lobes ii. 5-8 waves/sec iii. Normal in kids iv. Absent in normal adults v. Present in emotionally disturbed adults d. Delta i. Cortex area ii. 1-5 waves/sec iii. Present in awake infants and sleeping adults iv. If in awake adults= brain damage e. Brain lateralization i. AKA split-brain concept ii. By cutting the corpus callosum, the left and right cerebral hemispheres are uncoupled (some epileptics) First accidental lobotomy= Phineas Gage, 1848 iii. Hemisphere patterns 1. Left hemisphere- important in right handedness, spoken and written language, numerical and scientific skills, and reasoning 2. Right hemisphere- important in left handedness, music and art awareness, space and pattern recognition, insight, imagination, images of senses 3. 97% of all people, demonstrate this pattern 4. 3% are lefties that have language and analytical skills in right or both hemispheres (aa Vinci & Michelangelo=lefties) 5. Language areas a. Primary left ,cerebral cortex hemisphere b. Broca’s area= frontal gyrus, translates thoughts into speech c. Wenicke’s area= temporal gyrus i. Important in language comprehension ii. Damage= “word salad” 6. Emotion and motivation a. Limbic system- when stimulus generates emotions of fear, rage, aggression, pleasure, pain and sexual behavior 7. Memory a. Several different regions involved b. Two different types of memory: i. Short-term memory- simple stimulus response learning -> unconscious memory ii. Long-term memory- conscious memory c. Left hippocampus- converts short term memory -> long term= depends upon protein synthesis in neuron d. Right hippocampus- forms non-verbal memory 2. Diencephalon a. Forebrain b. Contains 3 regions i. Thalamus 1. 80% of diencephalon 2. Relay center for all sensory information (except smell) mores -> cerebrum 3. CSF (cerebral spinal fluid) synthesis 4. Pineal gland present ii. Hypothalamus 1. Centers for BMR (Basal metabolic rate), hunger, thirst, and pituitary hormone secretion 2. Coordination of sympathetic and parasympathetic reflexes iii. Pituitary- synthesis, stores, and release hormones 3. Mesencephalon a. Midbrain b. Extends from pons -> lower diencephalon (~2.5 cm) c. 2 major structures: i. Substantia Nigra- involved in motor control- Parkinsons ii. Corpora Quadrigemina 1. 4 rounded elevations 2. Reflex centers for head and eyeball movements 4. Rhombencephalon a. Hindbrain b. Divided into: i. Metencephalon 1. Pons a. “Bridge” b. =2.5 cm c. Connects spinal cord to brain and parts of the brain with each other d. Also, primary control of breathing via pneumotaxic (ability to breathe) & apneustic center (ability to hold breath) 2. Cerebellum a. Butterfly-shaped “wings” are hemispheres b. Primary regulates subconscious skeletal muscle movements for balance, posture, coordination ii. Mylencephalon 1. Medulla oblongata (upper portion of spinal cord, lower part of brain) 2. Contains all ascending and descending tracts b/w spinal cord and brain 5. RAS a. Reticular Activating System b. Composed of pons, midbrain, thalamus, and hypothalamus c. Produces consciousness, alertness and wakefulness d. Brain’s chief watchguard e. Sifts and selects info f. Forwards essential, unusual or dangerous information to cerebral cortex g. Sleep, lowers RAS b/w 3-5 AM III.Spinal Cord tracts a) General Information i) Ascending tracts- conduct sensory information up ii) Descending tracts- conduct motor information down CNS iii)Spinal Cord- from foramen magnum -> 1 lumbar iv)Vert. Column AKA spinal cord (1) Composed of outer white matter and inner gray matter (2) Forms an “H” with 2 dorsal & 2 ventral horns (3) Carries ascending and descending tracts (4) **All ascending start with “spino”. All descending end with “spinal”** 2) Cranial Nerves a) 12 pair i) 10 arise from brain stem ii) 2 arise from cerebellum b) Roman numerals I-XII= order they arise front-back from brain c) Mixed nerves or sensory d) Name= region of innervation (ex. Oculomotor) 3) Spinal Nerves a) 31 pair i) 8 cervical ii) 12 thoracic iii)5 lumbar iv)5 sacral v) 1 coccygeal b) Mixed-sensory & motor fibers separate near the spinal cord -> roots i) Dorsal root= sensory ii) Ventral root= motor 4) Reflex arc a) Unconscious motor response to sensory stimuli=fastest response b) Stimulate receptor -> action potential c) Sensory neuron -> synap with association neuron in spinal cord -> synap motor -> stimulate muscle contraction EX) knee-jerk response
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