Exam II Study Guide Functional Anatomy and Physiology Nervous System Nervous system o Sensory input receptor is stimulated and signals go to the CNS o Integration CNS processes sensory input and evaluates what to respond with o Motor Output outgoing signal from CNS to effector organs o Central and Peripheral Peripheral Nervous System o Sensory nerve dorsal root ganglion In posterior horn afferent Transmits AP from receptor to CNS Use dorsal root of spinal Somatic Fibers impulses from skin skeletal muscles and joints to the brain Visceral Fibers impulses from visceral organs to the brain o Motor Division efferent Transmits AP from CNS to effectors muscles glands Use ventral root of spinal nerve Somatic Nervous System CNS to skeletal muscle Voluntary and a single neuron Have a neuromuscular junction a synapse between a neuron and skeletal muscle cell Autonomic Nervous System then ganglion to effector CNS to smooth muscle Involuntary Two neuron systems CNS to ganglion o Neurons Nerve Cells connect CNS to sensory receptors muscles and glands We have 12 Cranial nerves and 31 pairs of spinal nerves Structure Functions Cell body axon dendrites axon hillock axonal terminals Neurotransmitter produced in the soma and stored in vesicles in the axon terminals Stimulates neuron receptors Function of Neurons receive stimuli and transmit action potentials Myelin Sheath a lipid layer covering the axon It protects and insulates axons from another speeds transmission and functions in repair of axons White Unmyelinated matter is composed of myelinated axons These are faster bodies and dendrites Found in Schwann Cells PNS and Oligodendrocytes CNS Axons also known as Gray matter Composed of cell Axon diameter and myelin are the only things that can speed up an Action Potential propagation Referred pain pain can travel to other places internally that aren t necessarily where pain is related Nociceptors free nerve endings found in body receptive to pain 1 Exam II Study Guide The Action Potential o Resting Membrane Potential Negative Positive ions inside K ions outside Na and Cl RMP exists because The concentration of ions is different inside and outside extracellular fluid is rich in Na and Cl Membrane permeability differs for Na and K There is a greater permeability for K potential difference o Depolarization becomes smaller cell is less polar less negative Open gates for Na to diffuse in Inside is becoming more positive less negative o Repolarization activated 3 Na out 2 K in make inside negativeee after depolarization where cell becomes more negative Na K pump is Na Channels close at top of the curve Na stops moving into cell K Channels open and K moves out of the cell potential difference becomes greater cell is more polar more o Hyperpolarization negative less excitable An inhibitory NT will cause hyperpolarization Hyperpolarization is also known as the refractory period End of stimulatory event Na Channels are closed and K diffuses by facilitated diffusion back and forth o Threshold must be reached for the cell to be stimulated o Electrical Gradient and Concentration Gradient affect Na K mvmt o Ionic Events 1 K is higher inside the cell than outside Na is higher outside the cell than inside Cell is at RMP as outside of cell is positively charged as compared to inside and both voltage gated channels are closed 2 Stimulus causes depolarization to reach threshold 3 Voltage gated Na channels open and Na diffuses into the cell 4 The cell depolarizes 5 Na channels close 6 Voltage gated K channels open and K leaves the cell 7 The cell repolarizes and enters small hyperpolarization phase 2 Exam II Study Guide Extra notes on AP 8 Voltage gated K channels close and RMP returns to 70mV Stimulus strength determines frequency of action potentials Voltage gated Na Channels are sensitive to Calcium concentrations in ECM If Extracellular Ca2 concentration decreases the Na gates will open and the membrane will depolarize Magnitude of AP is constant as they are for a given axon muscle fiber Axons of the Central Nervous System o Tracts Axons in PNS are nerves Synapses o Presynaptic and Postsynaptic Neurons o NTs are synthesized in soma then packaged perfected by Golgi then sent to axon terminal where they are stored in vesicles o Synaptic Cleft junction o Ca2 at axon terminal affects synaptic vesicles Action potentials cause Ca2 to enter the cell This stimulates the vesicle to release the NTs NT diffuses across synapse o Neurotransmitter binding to postsynaptic neuron this stimulates the cell o Removal of neurotransmitter Can occur by enzymatic degradation I e Acetylcholinesterase cutting ACh into acetic acid and choline This enzyme eliminates degrades effect of NT 3 Exam II Study Guide Inhibitory Synapses o Effect K Cl and hyperpolarization is the only electrical event after inhibitory NT binds An NT binding to a receptor at an inhibitory synapse results in hyperpolarization of the cell more negative and cell is less excitable less easily depolarized less likely to reach the all or none threshold This is a different hyperpolarization than in Na K pump b c it is the ONLY electrical event The membrane becomes more permeable to K and Cl ions K will diffuse out so the inside of the cell becomes more negative and Cl will diffuse in also causing the cell to be more negative Central Nervous System Central Nervous System Components o Brain and Spinal Cord Cerebral Cortex o Motor Areas pre central gyrus of frontal lobe o Sensory Areas post central gyrus of parietal lobe Signals received here o Primary Motor Cortex Voluntary Movement 4 Exam II Study Guide Motor Homunculus More precise movements have small motor units more axons while gross movements have large motor units less axons needed not finessed We need more neurons to control fine tuned muscle skills o 1 axon will stimulated three muscle fibers in hand Need larger area in homunculus for larger number of axons o 1 axon will also stimulate 100 myofibrils in leg Motor signal starts in pre central gyrus Spinal cord Stimulates peripheral motor neuron which innervates a skeletal muscle Motor neurons travel via spinal or cranial nerve to reach destination There are always two motor neurons Upper in CNS for processing and a Somatic Motor Pathway o Motor Tracts lower one in spinal cord Pyramids located in medulla Decussation of pyramids crossing over of 80 of fibers Corticospinal Pathway axial and limb motor control o Function motor o Pathway Pre central gyrus 2 neurons
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