2. I. Intro – 2 parts to Nervous System A. Central Nervous System – CNS Brain and spinal cord B. Peripheral Nervous System – PNS All the nerves that connect to CNS and other body parts
3. II. Nervous Tissue A. Neurons 1. Def: Nerve cell – structural and functional unit of the nervous system B. Neuron Structure 1. cell body Main portion of neuron Contains neurofibrils Conatains NISSIL BODIES Make protein Contains nucleus Mature neurons cannot reproduce DESTROY THEM AND THEY ARE GONE!!
4. 2. dendrites Short, highly branched parts off of cell body Each neuron may have many F: main RECEPTIVE surface of neuron Communicates with other neurons **BRINGS IMPULSES IN
5. 3. axon An extension of the cell body which sends impulses AWAY from the neuron Schwaan cells Cells which surround axon Make up myelin (lipoprotein) sheath MS – makes impulse travel very quickly A). Not all axons are myelinated GRAY MATTER Def: group of cells in NS which are unmyelinated WHITE MATTER Def: group of cells in NS which ARE myelinated Nodes of Ranvier Def: narrow gaps in myelin sheath b/n axon cells
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7. III. Nerve Impulse Conduction A. Nerve impulse Def: the propagation (increase/transmission) of electrical charges along nerve cells B. Process of Conduction 1. nerve fiber develops resting potential Def: state in which a net POSITIVE charge is on the OUTSIDE of the cell membrane = POLARIZED Cause: Na+ and K+ are key ions 3 Na+ ions diffuse outside the nerve fiber – low to high conc. 2 K+ ions diffuse inside the nerve fiber – low to high What is the charge? POSITIVE on OUTSIDE = resting potential
8. 2. Threshold stimulus is received Minimal stimulus needed for a nerve to fire Will be reached if a nerve is stimulated by: Nearby nerve stimulus Changes in light, temperature, pressure Resting potential decreases – net positive charge on outside of membrane decreases How? Sodium/Potassium pump = active transport Na+ channels open and Na+ starts flowing inside (L to H) cell membrane = DEPOLARIZED If stimuli are strong enough, THRESHOLD STIMULUS is reached
9. 3. Shortly after, K+ diffuses outside of cell (L to H) causing the cell to be REPOLARIZED 4. Action potential occurs Def: rapid depolarization and repolarization of a nerve cell Lasts 1/1000 of a second Causes electric current to flow to next area of nerve cell 5. Wave of APs continue through nerve = IMPULSE 6. refractory period Time when nerve is repolarizing and will not respond to another stimulus http://people.eku.edu/ritchisong/301notes2.htm
10. C. Impulse conduction 1. unmyelinated fibers Impulses travel slowly 2. myelinated fibers Impulses travel quickly Jump from N of R to N of R
11. D. all or none response Nerve fiber ALWAYS responds completely when TS is reached Impulse always travels through entire nerve E. Synapse Def: the junction where 2 neurons meet and interact Sending neuron: PRESYNAPTIC NEURON Receiving neuron: POSTSYNAPTIC NEURON Synaptic cleft: space b/n pre and post neurons ** impulses jump this gap when traveling
12. F. Neurotransmitters 1. def: chemical substance released by presynaptic neuron which may cause impulses to be conducted to postsynaptic neuron ** if enough NT is released, TS in postsynaptic is reached and impulse travels 2. Types A. excitatory NT Cause impulse to quickly be transferred to postsynaptic neuron Allows ions to quickly diffuse through membrane B. inhibitory NT Cause impulse to die TS is raised because ions can’t diffuse
13. Examples Excitatory Acetylcholine Dopamine Inhibitory GABA – gamma amino butyric acid Mood, control many other excitatory NT Serotonin Slow the brain down, reduce stress, relax, effect mood
14. V. Types of Neurons/nerves A. Multipolar neurons – many nerve fibers Many dendrites/ 1 axon Located: brain and spinal cord B. bipolar neurons – 2 nerve fibers 1 axon/ 1 dendrite Located: eyes, nose, ears C. unipolar neuron – 1 nerve fiber, splits into A and D 1 dendrite/ 1 axon Axon connected to brain/ spinal cord Dendrite connected to peripheral body part
15. D. Nerve types Nerves: group of neurons held together by connective tissue 1. sensory nerves Send messages to brain/SC 2. motor nerves Send messages to muscles/glands 3. mixed nerves Send messages to both 4. interneurons Connect nerves in brain/SC
16. VI. Nerve pathways A. reflex arc 1. def: the simplest pathway an impulse may take ** never reaches the brain Process: 1. Sensory receptor at end of sensory nerve fiber takes in stimulation 2. SNF takes it to reflex processing center in Spinal Cord 3. interneurons communicate in SC 4. motor neuron carries response to effector 5. effector does action – muscle, gland etc
17. B. reflex behavior 1. def: automatic unconscious responses to changes occurring within or outside the body 2. controls: Heart rate Breathing rate Blood pressure Digestion Sneezing Coughing Vomiting
18. 3. example: knee jerk A. sensory receptor sense touch to petallar ligament B. sensory nerve fiber dendrite takes in info C. impulse sent to SC where sensory axon meets an interneuron which connects to motor neuron dendrite D. motor axon carries impulse to effector in quad E. quad flexes 4. withdrawal reflex Person touches something hot, pulls away body part P. 214
19. VII. Impulse processing A. convergence 1. def: neuron impluses from 2 or more axons converge on 1 neuron Allows NS to bring different information together B. divergence 1. def: impulses leaving 1 axon pass into several other neurons Allows impulse effect to be amplified Ex: send message to all motor neurons in muscle so all contract
20. VIII. Coverings of CNS A. Intro 1. brain lies in: cranial cavity 2. SC lies in: vertebral canal 3. both surrounded by membranes called MENINGES Between bone and nerve tissue
21. B. meninges 3 layers Dura mater Arachnoid mater Pia mater 1. dura mater Outermost Tough, white connective tissue Many vessels & nerves May extend into lobes of brain
22. 2. arachnoid mater Thin, weblike Middle layer No blood vessels ** Cerebrospinal fluid between arachnoid and pia mater – CSF 3. pia mater Thin Innermost Many vessels to nourish brain and SC
23. VIII. Spinal Cord A. Intro Cord begins at foramen magnum and end at intervertebral disk b/n 1st and 2nd lumber vertebrae B. structure 1. 31 segments, each with a pair of nerves that branches off peripherally Spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal CAUDA EQUINA – last group of nerves, taillike
25. 3. Functions of SC 1. to conduct nerve impulses to and from Brain Involves only white matter A. ascending tract Carry impulses TO brain B. descending tract Carry impulses FROM brain to muscles/glands 2. to be the center of the reflex arc Involves grey matter
26. IX. Brain A. Intro 100 billion multipolar neurons 3 major portions: 1. cerebrum Largest Nerve centers for sensory and motor functions Memory and reasoning centers here 2. cerebellum Posterior/dorsal region Coordinates complex skeletal voluntary muscle movements Maintains posture Position of body parts 3. brain stem Connects nerve pathways that connect many nerves between SC and brain Regulate many organ activities
27. B. Cerebrum 1. Structure A. cerebral hemispheres (2) 2 equal halves of cerebrum B. corpus callosum Bridge of nerve fibers that connects cerebral hemisheres Allows R and L sides to communicate C. convolutions Ridges of cerebrum D. sulcus Groves b/w convolutions E. fissures DEEP groves b/n parts of the brain
28. F. frontal lobe G. parietal lobe H. occipital lobe I. Temporal lobe J. cerebral cortex Thin layer of grey matter over cerebrum Covers convolutions, sucli, and fissures Contains nearly 75% of all neuron cell bodies Just beneath is a mass of White Matter that makes up cerebrum
29. 2. functions A. frontal lobe 1. motor speech area – Broca’s Area Moves mouth, tongue, pharynx, larynx 2. frontal eye field Controls voluntary movements of eyes and eyelids 3. Concentration, planning, problem solving area 4. emotions and reasoning 5. motor areas which control voluntary muscles
30. B. parietal lobe Sensory areas involved with sensations of skin Understanding speech, using words C. occipital lobe Visual area Combines visual images from L and R eyes Recognition D. temporal lobe Interpretation of sensory experiences Memory of visual and audio patterns E. general interpretive area Overlaps all lobes Primary in complex thought and processing F. hemisphere dominance L= verbal, analytical, computational, detailed R= musical, visual, creative,
31. C. cerebrospinal fluid – CSF 1. structure A clear liquid that is secreted by CHOROID PLEXUS in pia mater Tiny flowerlike masses Circulates around the brain and down central canal of SC – eventually reaches blood to deliver wastes etc 2. function Surrounds brain and SC for support/protection Provide path to blood for waste ** always stays at same pressure b/c it is continually made and reabsorbed ** it not, pressure on the brain
32. D. cerebellum 1. located below occipital lobe 2. mostly white matter 3. covered by CEREBELLAR CORTEX – grey matter 4. involved in: Planning Personality Intelligence Interprets desired movements and causes body to do them 5. damage = : Tremors Loss of muscle tone Uncoordinated walk Loss of equilibrium
33. E. brain stem Def: bundle of nerve tissue that connects cerebrum to spinal cord Several masses of grey matter 1. Parts: A. diencephalon b/w cerebral hemispheres 1) infundibulum here A piece which hangs down and attaches to pituitary gland 2) thalamus here Receives all sensory impulses and relays them to appropriate region of cortex for interpretation
34. 3) hypothalamus here Regulates heart rate, blood pressure, body temp, hunger, release of hormones, regulates sleep 4)limbic system here Combination of many areas Involved in emotional expression Fear, anger, pleasure, sorrow Recognizes things that threaten life – “fight or flight”
35. B. midbrain Below diencephalon Much grey matter as a reflex center Visual reflex = eyeballs move when head moves Auditory reflex = ears move close to sound C. pons Below midbrain – round bulge Relay impulses all over brain Ex: relays breathing rhythms to medulla oblongata D. medulla oblongata Extends from pons Controls: Cardiac center: speed or lower heart rate Vasomotor center: constrict/dilate blood vessels Respiratory center: rate/rhythm of breathing
36. X. Peripheral Nervous System - PNS A. def: nerves that branch out from the brain and SC SOMATIC NS: consists of cranial and spinal nerves that connect to skin and skeletal muscle AUTONOMIC NS: nerves that connect to organs/glands
37. B. Cranial nerves – 12 pair * go in order from front to back 1. olfactory nerves (I) Sensory nerves Transmit smell impulses 2. optic nerves (II) Sensory nerves Transmit vision impulses 3. oculomotor(III) Mostly motor nerves Transmit impulses to: adjust lens, adjust pupil, move eyelid, move eye
38. 4. trochlear (IV) Mostly motor nerves Transmit eye movement impulses 5. trigeminal (V) Mixed Sensory: Transmit impulses from: tear glands, scalp, forehead, upper eyelids, teeth, lips, skin of face Motor: Transmit impulses of chewing
39. 6. Abducens (VI) Mostly motor Transmit impulses of eye movement 7. facial (VII) Mixed Sensory: Transmit impulses of tongue/taste Motor: Facial expression, tear glands, salivary glands 8. vestibulocochlear (VIII) Sensory nerves Transmit impulses for equilibrium and hearing
41. 11. accessory (XI) Mostly motor Pharynx, larynx, neck, back 12. hypoglossal (XII) Mostly motor Muscles that move tongue
42. D. Spinal Nerves 31 pair Communicate impulses from spinal cord and arms, legs, neck, trunk
43. D. Autonomic Nervous System Regulates heart rate, BP, breathing rate, body temp Respond to emotional stress and strenuous physical activity 1. sympathetic division Prepares body for emergency situations Initiates activation and secretion of adrenaline 2. Parasympathetic division Active during ordinary conditions Restores body back to normal after stress
