2. Chapter 31 The Nervous System

3. I. The Nervous System A. Purpose 1. controls and coordinates functions throughout the body 2. responds to internal and external stimuli

4. B. Neuron 1. cells that transmit electrical signals or impulses

5. 2. Types a. Sensory 1) carry impulses from sense organs to spinal cord and brain b. Motor 1) carry impulses from the brain and spinal cord to muscle and glands c. Interneurons 1) carry impulses between sensory and motor

6. Axon terminals Myelin sheath Nodes Cell body Axon Nucleus Dendrites A Neuron

7. C. Nerve Impulse 1. Resting Neuron a. Outside of cell – net (+) charge b. Inside of cell – net (-) charge c. Cell membrane is electrically charged

8. d. Results from active transport of ions through the Sodium-Potassium Pump 1) Na + pumped out of cell 2) K + pumped in to cell

9. e. cell membrane allows K + to leak out creating a negative charge on the inside of the cell e. cell membrane allows K + to leak out creating a negative charge on the inside of the cell 1) this is called resting potential

10. 2. Moving Impulse 2. Moving Impulse a. impulse begins when a neuron is stimulated by another neuron or the environment b. impulse travels rapidly away from body cell and toward axon terminals c. at the leading edge, the sodium gates open allowing Na + to move into the cell d. inside of cell becomes positive

13. e. action potential 1) the reversal of charges, from negative to positive f. as the impulse passes, the K gates open and K + ions flow out g. resting potential is restored

15. 3. threshold 3. threshold a. the minimum level of a stimulus that is required to activate a neuron b. All or None Principle 1) either the stimulus will produce an impulse or it will not

16. Vesicle Axon Axon terminal Synaptic cleft Neurotransmitter Receptor Dendrite of adjacent neuron Direction of Impulse The Synapse

17. D. The Synapse 1. the location at which a neuron can transfer an impulse to another cell 2. the axon terminals contain vesicles of neurotransmitters a. signaling molecules that diffuse across chemical synapses 3. neurotransmitters are quickly taken up, diffused, or recycled

19. II. Divisions of the Nervous System A. Central Nervous System 1. brain and spinal cord 2. relays messages, processes information, and analyzes information 3. meninges a. 3 layers of connective tissue wrapped around brain and spinal cord 4. cerebrospinal fluid a. fluid between layers of meninges that protect

20. Pons Pituitary gland Hypothalamus Cerebrum Medulla oblongata Spinal cord Cerebellum Pineal gland Thalamus The Brain

21. B. Peripheral Nervous System 1. all nerves and cells that are not part of the brain or spinal cord 2. 31 pairs of spinal nerves 3. sensory nerves – transmit impulses from sense organs to CNS 4. motor nerves – transmits impulses from CNS to muscles or glands

22. 5. Two subdivisions of Peripheral Nervous System a. Somatic Nervous System 1) regulates activities under conscious control 2) body can react before the brain even knows what happened

23. b. Autonomic Nervous System 1) regulates involuntary activities (smooth and cardiac muscle, glands) 2) two categories a) parasympathetic NS - slows down the body - slows down the body - diverts energy to basic - diverts energy to basic ‘housekeeping’ activities

24. b) sympathetic NS - dominates in times of sharpened - dominates in times of sharpened awareness, stress, excitement or danger - puts ‘housekeeping’ on hold - puts ‘housekeeping’ on hold c) most organs controlled by ANS are controlled by both sympathetic and parasympathic NS - they compete for control - they compete for control