The Nervous System

The nervous system is a complex system of nerves and cells called neurons that transmit signals between the parts of the body.

A Neuron

is an individual nerve cell that processes and transmits information through electrical and chemical signals.

Parts of a Neuron

Dendrites- Receive messages from other cells

Axon- Passes messages away from the cell body to other neurons, muscles, and glands

Cell body- The cell's life support center

Neural impulse- Electrical signals traveling down the axon

Myelin Sheath- Covers Axon and increases impulses

Synapse- structure that permits a neuron to pass a chemical/electrical signal to another cell

But how does a Neuron fire?

Resting Potential 

 -neuron was reached threshold when enough negative neurotransmitters reach dendrites

Action Potential

- Electrochemical process

-The electrical charges inside of a neuron

- Chemical outside of the neuron(in the synapse in the form of a neurotransmitter)

All or Nothing Principle

- The idea that either the neuron fires or does not

-no partway firing

Neurotransmitters

are chemical messengers released by terminal buttons through synaptic gap.

 There are 4 main types.

Acetylcholine (ACH)

- Deals with motor movement and memory

-Lack of ACH is linked to Alzheimers

Dopamine

-Deals with motor movement and alertness

-Lack of Dopamine is linked to Parkinson

-Overabundance is linked to Schizophrenia

Seratonin 

- Linked with mood control 

-Lack of seratonin is linked to depression

Endorphins 

-Involved with pain control

-Addictive drugs deal with endorphins

Antagonists- Stop Neural firing 

Agonists- Synthesize Neural firing

Types of Neurons

(Sensory)

Afferent Neurons

-Take info from senses to the brain

Inter Neurons

-Take messages from sensory neurons to other parts of the brain or motor neurons

(motor)

Efferent Neurons

-Take info from brain to the rest of the body and nervous system

Central Nervous System

-Brain and spinal cord

Peripheral Nervous System

-All nerves not encased in the bone

-All but spinal cord

-Diverges into somatic & autonomic Nervous system

Somatic Nervous System

- Controls voluntary muscle movement

-Uses motor neurons

Autonomic Nervous System

-Controls automatic functions of the body

Divided into 2 categories (sympathetic & parasympathetic)

Sympathetic Nervous System

-Linked to Flight or Fight instincts

-Automatically accelerates heart rate, breathing, dilates pupils, and slows digestion

Parasympathetic Nervous System

-Automatically slows the body down after a stressful event

-Heart rate and breathing slow, digestion increases

Reflexes

-Normally sensory neurons take info up through the spine to the brain

-Some reactions occur when sensory neurons reach spinal cord

Lesions

-Cutting into the brain and looking for changes- i.e Brain tumors