The Nervous System

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The Nervous System

• Regulates our internal functions• Involved in how we react to the external

environment• Two main parts

– Central Nervous System– Peripheral Nervous System

Neurons

• Nerve cells that run through our entire body and communicate with each other

• Receive messages from parts of the body (muscles, glands, etc)

• 100 Billion in our bodies, mostly in the brain

• Neurons are composed of:– Cell body (soma): directs actions of the cell– Dendrites: extensions that receive

information– Axon: extends from cell body, carries

electrical potential, sends a chemical message to adjacent neurons via terminal buttons

Neurons are for Communicating

Messages are sent from the axon

terminals of one neuron to the dendrites of

another

Synapse

• In order for the message to send from neuron to neuron they must cross the synapse

• The message only goes in one direction

Dendrites > Cell Body > Axon > Axon Terminals > Dendrites…..

Synapse

Neurotransmitters

• Neurons send messages across the synapse through the release of neurotransmitters

• Chemicals stored in sacs in the axon terminals

• Several types, each with a specific structure and can only fit into a specific receptor site

Types of Neurotransmitters• Serotonin – affects mood, sleep, sensory

perception, and other functions, may play a role in psychological disorders like depression

• Acetylcholine – involved in memory, muscle action, sleep, emotions, those w/ Alzheimer’s have lower levels

• Dopamine – affects movement, attention, memory, learning, plays role in addiction

• Norepinephrine – affects learning, memory, emotions, eating, alertness, etc.

• Epinephrine – emotions, memory storage…

Central Nervous System• Made up of:

– Brain (we will talk about this later)– Spinal Cord

• Extends from the brain down the back• Column of nerves, as thick as your thumb• Spinal Reflexes

– When your knee kicks at the doctors office– Blinking when you get something in our eye

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Peripheral Nervous System

• Responsible for transmitting messages between the CNS and the rest of the body

• Two Main Systems in the PNS:– Somatic Nervous System– Autonomic Nervous System

Somatic Nervous System

• Transmits messages to the CNS• Activated by touch, pain, changes in

temperature or changes in body positions

• Sends messages to muscles and glands

Autonomic Nervous System

• Regulates the body’s vital functions– Heartbeat, breathing, digestion, etc.

• Two divisions:– Parasympathetic – Sympathetic

Autonomic Nervous SystemParasympathetic

• Restores bodies energy after an action has occurred

• Slows down heartbeat, digestion, breathing

Sympathetic• Fight or flight

response• Activated when the

body is put in a stressful situation