Chapter 31Chapter 31The Nervous SystemThe Nervous System

I. The Nervous SystemI. The Nervous SystemA. PurposeA. Purpose

1. controls and coordinates functions 1. controls and coordinates functions throughout the bodythroughout the body2. responds to internal and external 2. responds to internal and external stimulistimuli

B. NeuronB. Neuron1. cells that transmit electrical signals 1. cells that transmit electrical signals or impulsesor impulses

2. Types2. Typesa. Sensorya. Sensory

1) carry impulses from sense 1) carry impulses from sense organs to spinal cord and brainorgans to spinal cord and brain

b. Motorb. Motor1) carry impulses from the brain 1) carry impulses from the brain and spinal cord to muscle and and spinal cord to muscle and glandsglands

c. Interneuronsc. Interneurons1) carry impulses between 1) carry impulses between

sensory sensory and motorand motor

Axon terminals

Myelin sheath

Nodes

Cell body

Axon

Nucleus

Dendrites

A Neuron

C. Nerve ImpulseC. Nerve Impulse1. Resting Neuron1. Resting Neuron

a. Outside of cell – net (+) chargea. Outside of cell – net (+) chargeb. Inside of cell – net (-) chargeb. Inside of cell – net (-) chargec. Cell membrane is electrically c. Cell membrane is electrically

chargedcharged

d. Results from active transport of ions d. Results from active transport of ions through the Sodium-Potassium Pumpthrough the Sodium-Potassium Pump

1) Na1) Na++ pumped out of cell pumped out of cell2) K2) K++ pumped in to cell pumped in to cell

e. cell membrane allows Ke. cell membrane allows K++ to leak out to leak out creating a negative charge on the creating a negative charge on the inside of the cellinside of the cell1) this is called 1) this is called resting potentialresting potential

2. Moving Impulse2. Moving Impulsea. impulse begins when a neuron is a. impulse begins when a neuron is stimulated by another neuron or the stimulated by another neuron or the environmentenvironmentb. impulse travels rapidly away from b. impulse travels rapidly away from body cell and toward axon terminalsbody cell and toward axon terminalsc. at the leading edge, the sodium gates c. at the leading edge, the sodium gates open allowing Naopen allowing Na++ to move into the cell to move into the celld. inside of cell becomes positived. inside of cell becomes positive

e. action potentiale. action potential1) the reversal of charges, from 1) the reversal of charges, from negative to positivenegative to positive

f. as the impulse passes, the K gates f. as the impulse passes, the K gates open and Kopen and K++ ions flow out ions flow out

g. resting potential is restoredg. resting potential is restored

3. threshold3. thresholda. the minimum level of a stimulus that a. the minimum level of a stimulus that is required to activate a neuronis required to activate a neuronb. All or None Principleb. All or None Principle

1) either the stimulus will produce 1) either the stimulus will produce an impulse or an impulse or it will notit will not

VesicleAxon

Axon terminal

Synaptic cleftNeurotransmitter

Receptor

Dendrite of adjacent neuronDirection of Impulse

The Synapse

D. The SynapseD. The Synapse1. the location at which a neuron can 1. the location at which a neuron can transfer an impulse to another celltransfer an impulse to another cell2. the axon terminals contain vesicles 2. the axon terminals contain vesicles of neurotransmittersof neurotransmitters

a. signaling molecules that diffuse a. signaling molecules that diffuse across chemical synapsesacross chemical synapses

3. neurotransmitters are quickly taken 3. neurotransmitters are quickly taken up, diffused, or recycledup, diffused, or recycled

II. Divisions of the Nervous SystemII. Divisions of the Nervous SystemA. Central Nervous SystemA. Central Nervous System

1. brain and spinal cord1. brain and spinal cord2. relays messages, processes 2. relays messages, processes information, and analyzes informationinformation, and analyzes information3. meninges3. meningesa. 3 layers of connective tissue a. 3 layers of connective tissue wrapped around brain and spinal cordwrapped around brain and spinal cord4. cerebrospinal fluid4. cerebrospinal fluida. fluid between layers of meninges a. fluid between layers of meninges that protectthat protect

Pons

Pituitary glandHypothalamus

Cerebrum

Medulla oblongata Spinal cord

Cerebellum

Pineal gland

Thalamus

The Brain

B. Peripheral Nervous SystemB. Peripheral Nervous System1. all nerves and cells that are not part 1. all nerves and cells that are not part of the brain or spinal cordof the brain or spinal cord2. 31 pairs of spinal nerves2. 31 pairs of spinal nerves3. sensory nerves – transmit impulses 3. sensory nerves – transmit impulses from sense organs to CNSfrom sense organs to CNS4. motor nerves – transmits impulses 4. motor nerves – transmits impulses from CNS to muscles or glandsfrom CNS to muscles or glands

5. Two subdivisions of Peripheral 5. Two subdivisions of Peripheral Nervous SystemNervous Systema. a. SomaticSomatic Nervous System Nervous System

1) regulates activities under 1) regulates activities under conscious controlconscious control

2) body can react before the brain 2) body can react before the brain even knows what happenedeven knows what happened

b. b. AutonomicAutonomic Nervous System Nervous System1) regulates involuntary activities 1) regulates involuntary activities (smooth and cardiac muscle, glands)(smooth and cardiac muscle, glands)2) two categories2) two categories

a) a) paraparasympathetic NSsympathetic NS - slows down the body- slows down the body - diverts energy to basic - diverts energy to basic

‘‘housekeeping’ activitieshousekeeping’ activities

b) sympathetic NSb) sympathetic NS - dominates in times of sharpened - dominates in times of sharpened awareness, stress, excitement or awareness, stress, excitement or dangerdanger - puts ‘housekeeping’ on hold- puts ‘housekeeping’ on hold

c) most organs controlled by ANS are c) most organs controlled by ANS are controlled by both sympathetic and controlled by both sympathetic and parasympathic NSparasympathic NS

- they - they competecompete for control for control