Nervous System & Senses

Neuron• A neuron is the basic unit of the

Nervous System.

• Carry messages in the form of electrical impulses.

Neuron Structure

Three Basic Parts:

A. Axon – carry impulse away from cell body

B. Dendrites – carry impulses toward cell body

C. Cell Body – largest part, contains the nucleus

Three Main Types

1. Sensory : body to brain2. Motor : brain to body3. Interneuron : found in brain

& spinal cord; process incoming impulses and pass them to motor neurons

Synapse• Synapse: The space between the

axon terminal of one neuron and the dendrites of the next neuron.

• Drugs & alcohol

Molecules get

In the Synapse and

Prevent messages

From relaying properly

Messages jump across the synapse

like an electrical current

Central Nervous System

Two Parts:

• Brain

• Spinal Cord

Peripheral Nervous System

• All nerves outside of brain and spinal cord

• Sensory – receives internal and external stimuli

• Motor – controls muscles and glands

Peripheral Nervous System1. Somatic NS – controls all voluntary activity

2. Autonomic NS – involuntary activity• Sympathetic – controls body during times of

stress

- Works with endocrine system for fight or flight– Ex - speeds up heart rate

• Parasympathetic – controls body normally, returns body to normal state after stress– Ex – slows heart rate

• Sight, Sound, Taste, Touch, Smell

• There are 5 general categories of sense receptors.– Pain receptors– Thermoreceptors - temperature– Mechanoreceptors – touch, sound– Chemoreceptors - chemicals– Photoreceptors - light