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Nervous System Honors Biology Powerpoint #3 Unit 8 – Chapter 35 pg. 897-904 The Senses Activities Function of Nervous System: Coordinates the body’s response to changes in its internal and external environments. Neurons Messages carried by nervous system are electrical impulses Cells that transmit impulses are called NEURONS 3 types of neurons: 1. Sensory: carry impulse from sense organ to spinal chord and brain 2. Motor: carry impulse from brain and spinal chord to muscles and glands 3. Interneurons: connect sensory and motor and carry impulses in between Neurons Pyramidal neurons forming a network in the brain Neurons: Structure • Cell Body (Soma): Cell’s “life support” center • Dendrites - conducts “signal” toward the cell body -[input zone] • Receives signal from sensory cell or neighboring neuron Axon - usually a single fiber -- [conducting zone] conducts signal away from cell body to another neuron or effector cell Axon Ending- a cluster of branches (100’s to 1000’s) that relays signal to next neuron / effector cell Myelin Sheath Covers the axon of some neurons Allows signal to travel faster because impulse “jumps” from node of Ranvier to node of Ranvier (with myelin sheath (225 mph / without 11 mph) Multiple Sclerosis • Immune System attacks Myelin in brain and spinal chord Multiple Sclerosis (MS) • Loss of motor functions How a nerve impulse is transmitted 1) At Rest - The neuron is POLARIZED (-70mV) There is a slightly negative charge on the inside, and a positive charge on the outside….. Why? balance is maintained by the sodium-potassium pump (active transport) Pumps Na+ (sodium) outside & Pumps K+ (potassium) inside Membrane leaks and some K+ goes back out Resting Potential= -70mV because overall postive charge outside and negative charge inside How a nerve impulse is transmitted 2) Depolarization Stimulus causes opening of Na+ gates, allowing Na+ to rush in (facilitated diffusion) changes the neuron from polarized to de-polarized then to + 30mV Reversal of charges = Nerve impulse aka Action Potential How a nerve impulse is transmitted 2) Depolarization This is all-or-none, meaning a stimulus must exceed a threshold for the action potential to occur Intensity of the stimulus is based on the number of neurons that exhibit an action potential. Speed of impulse based on diameter of axon & amount of myelination. How a nerve impulse is transmitted 3) Repolarization After inside flooded with NA+, K+ gates open and let K+ out (while NA+ gates close) The inside becomes –while outside become + and this repolarizes membrane How a nerve impulse is transmitted 4) Refractory period When the Na+/K+ balance returns to normal (K+ on inside and Na+ outside) During this time the neuron will not respond to new impulses Nerve Impulse Transmission The Synapse • Neurons DON’T touch • The gap between the axon of one neuron, and the dendrites of another is called the SYNAPSE 1. Action potential happens 2. Neurotransmitter is released by axon ending Neurotransmitter is a chemical that sends a signal 3. Neurotransmitter binds to dendrite membrane of next neuron 4. Excitation or inhibition of the membrane occurs 5. Neurotransmitter is ‘recycled’ The Synapse Divisions of the Nervous System: 1. Central Nervous System (CNS) 1. Peripheral Nervous system (PNS) 1. The Central Nervous System (CNS) Relays messages, processes information and analyzes information. Includes: Brain Spinal Cord Parts of the Brain Cerebrum’s Purpose: Controls voluntary activities of the body Cite of intelligence, learning, and judgment Made up of frontal, parietal, occipital, and temporal lobes Phineus Gage Parts of the brain Cerebellum: coordination and balance Brain stem: regulates blood pressure, heart rate, breathing, and swallowing Parts of Brain Thalamus: relays sensory input to proper region of cerebrum Hypothalamus: control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature 2. Peripheral Nervous System: everything outside of CNS 1. Sensory Division: transmits impulses from sense organs to central nervous system What are sense organs? Organs designed to pick up stimuli (name 5 sense organs) 2. Motor Division: Transmits impulses from CNS to the muscles or glands Quick Quiz: Which is sensory which is motor? Seeing Sensory Raising your hand Motor Tasting Sensory Blinking when a ball is thrown past your face Sensory when you see the ball, motor when you blink Motor Division of PNS 2 parts 1. Somatic Nervous system Regulates activities under conscious control (ex. Moving skeletal muscles) Some involved with reflexes and can act without conscious control (see next slide) 2. Autonomic Nervous System Regulates activities that are automatic or involuntary Example: when running, speeds up heart and blood flow, stimulates sweat glands and slows down digestion Divided into sympathetic and parasympathetic Sensory neuron interneuron Without brain processing Reflex Arc motor neuron Reflex Arc Parkinson’s Disease Cause Parkinson's disease is a disorder of the brain that leads to shaking (tremors) and difficulty with walking, movement, and coordination. Caused by loss of dopamine producing cells in brain (substantia niagra) Dopamine helps control muscle movement by releasing inhibitory function of substantia niagra so things are not moving when not specifically told to do so Without dopamine, it takes more effort for each motion and movements are shaky DON’T DO DRUGS!!!!!