Transcript Ch. 48 - 49
Ch. 48 Nervous Systems Nervous System Central Nervous System PNS AUTONOMIC Sympathetic Stress (like Parasympathetic Peace a “fight or flight” response) (relaxed, normal functions) Nervous system afferent interneurons efferent PNS, CNS INPUT: Effector cells Sensory Neurons (receptors) INTEGRATION: CNS(brain & spinal cord) Interneurons OUTPUT: Motor Neurons (effectors) The Reflex Arc The Neuron Dendrites receive the signal, axon delivers the signal away to another neuron or to the CNS Myelin sheaths (white matter) insulate the axon and are made by Schwanns cells or oligodendrocytes What is a Node of Ranvier? What is saltatory conduction? What is a synapse? Anatomy of a Neuron Makes myelin - PNS >Speed of Transmission: Larger axons & Myelin sheath (Saltatory conduction) Think! Turn to your partner and discuss… 1. 2. 3. 4. 5. Name the three types of neurons and their functions. Which make up the CNS and the PNS? Describe the main parts of a neuron. Describe what happens in a Reflex Arc. How are Nodes of Ranvier and Saltatory conduction related? What occurs at the synapse? What makes a signal travel down the axon ? Action Potential (“all or none” nerve impulse) K+ out of the cell Threshold Potential reached: -55mV -70 -50 0 Na+ Gates Open …Na+ flood cell -80 Na/K pump restores Hyperpolarization IPSP from too many K+ ions leaving -90 Membrane potential (mV) +35 EPSP Na+ Gates Close and K+ Open 0 1 2 3 4 Time (milliseconds) resting state restored (-70) Hyperpolarization: more negative inside by K+ moving out—does not cause an action potential Depolarization: inside gains more positive charge by Na+ rushing in EXCITATORY (+) -70 What is meant by all–or–none action potential? Think! Turn to your partner and discuss… 1. 2. 3. What causes an action potential? What significance is the -55mV? Describe the differences between depolarozation, repolarization, and hyperpolarization. The steps of an action potential… Resting State + Na gates closed, K+ gate closed Na/K pump is maintaining –70mV thres Depolarizing Phase Na+ gate OPENS, (fast gate) + K channels are still closed (slow gate) Na+ rushes into the neuron (+ + + +) RE-polarizing Phase + Na inactivation gate closes, K+ slow gate OPENS K+ rushes out of the neuron Undershoot + Na channels closed, K+ channels still OPEN K+ still rushes out of the neuron (Hyperpolarizing the inside - - - - - -) Direction of transmission? Slow closing of the K+ channels prevents “backflow” One way flow of Electricity! Chemical synapses TERMS: Vesicles synaptic cleft neurotransmitters (Ca2+) receptor ion channel Pre/post synaptic membrane Enzymes to degrade the neurotransmitters Summation of IPSP & EPSP Inhibitory(-) & Excitatory(+) Post-Synaptic Potential Temporal and Spatial Summation The real thing . . . . . . . . Cerebrum Thalamus Hypothalamus Cerebellum Brain stem: medulla oblongata, pons, midbrain Cerebrum Right versus left Cerebrum BRAIN STRUCTURES AND FUNCTIONS Brain Stem: Medulla Oblongata & Pons = (autonomic, homeostatic, data conduction) Midbrain = (receives and integrates sensory information) Cerebellum: Automatic coordination of movements and balance Thalamus:integration of stimuli coming to the brain Hypothalamus: important homeostatic regulation (temperature, hunger, thirst) & hormones Cerebrum: memory, learning , emotions, motor movements, sensory cortex areas