The Structure of the Nervous System

Divisions of the Nervous System

The Nervous System:

Central Nervous System

CNSPeripheral Nervous Systems

PNS

Central Nervous System (CNS): - brain

- spinal cord

Peripheral Nervous System (PNS)

• The nerves that connect the CNS to the rest of the body

• The system is subdivided into the somatic and autonomic nervous systems.

Autonomic Nervous System

• Monitors the autonomic functions (breathing, blood pressure, digestion)

• Divided into the sympathetic and parasympathetic nervous systems

Sympathetic Nervous System:

In charge of arousal responses such as

“fight or flight” (helps us deal with

perceived threats)

Parasympathetic Nervous System:

Calms the body and brings it back to a relaxed state

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

HOW DOES THE

NERVOUS SYSTEM WORK?

I. Neuron - The basic building block of the nervous system (a

nerve cell)

• Receive, Carry, and Pass information on to the next neuron

Parts of the Neuron

Dendrites

• Receive information into the cell body.

Soma - cell body of a neuron

Nucleus: the organelle that is located in the center of the cell body of a neuron.

Axon - takes information away from the cell body.

Myelin Sheath: Fatty material that surrounds

some axons•its purpose is to protect the axon

and speed processing.

Axon Terminal: the end of the neuron, it releases neurotransmitters into the synaptic cleft

Neurons

Neuron

Neural Communication:

The Neural Impulse

1. Action Potential

• A brief electrical charge that travels down the axon of the neuron.

2. Neurotransmitters: Chemical messengers that are released into the synapse.a. Examples: Acetylcholine

(movement), Serotonin (mood)

b. Are also found in psychiatric medications and other substances

• Antagonists: block neurotransmitters if you have too much (ex: People with Schizophrenia have 6x the proper level of dopamine!)

• Agonists: mimic neurotransmitters when you don’t have enough (ex: Depression is caused by low levels of serotonin.)

3. Synapse: A space or “junction” between two neurons

• The gap where neurotransmitters are released by one neuron and absorbed by the next neuron

Neurotransmitters

How Do Neurons Communicate?

• First, neurotransmitters are received by the dendrites.

• Then, the information is processed by the soma.

• Next, an action potential occurs, sending information down the axon.

• Finally, neurotransmitters are released at the axon terminal for the next neuron to absorb.

C. Types of Neurons

• Sensory - carry information to the central nervous system from the sensory organs (eye, ear, skin, etc.)

• Motor - carry information from the central nervous system to the muscles and glands

A Neural Chain

A Neural Chain

A Neural Chain

A Neural Chain

A Neural Chain