Notes - March 6, 2014

The Nervous System

• Starts with a nerve cell called a neuron

Neuron Anatomy

• Neurotransmitter - chemical held in terminal button that travels through synaptic gap
• Cell Body - the cells support center
• Dendrites - Receive messages from other cells
• Axon - passes messages away from the cell body to other neurons, muscles or glands
• Terminal Branches of Axon - forms junctions with other cells
• Mylin Sheath - covers the axon of some neurons and helps speed up neural impulse
• Neural Impulse - electrical signal traveling down the axon
• Synapse - a structure the permits a neuron to pass a chemical or electrical signal to another cell

How Does a Neuron Fire?

• Resting Potential - Slightly negative charge
• Reach the threshold when enough neurotransmitters reach dendrites

How a Neuron Fires

• an electrochemical process
• electrical inside neuron
• chemical outside neuron in the synapse in the form of a neurotransmitter
• the firing is called action potential

All or None Response

• idea that either the neuron fires or not - no part way firing
• No fire - trouble

Neurotransmitters

• chemical messengers released by terminal buttons through synapse

4 Types of Neurotransmitters

1. Acetylcholine (AcH)
• Deals with motor movement and memory
• Lack of AcH has been linked to Alzheimer's Disease
2. Dopamine
• Deals with motor movement and alertness
• Lack of dopamine has been linked to Parkinson's disease
• Too much dopamine = schizophrenia
• End of relationship = lower dopamine levels
3. Serotonin
• involved in mood control
• lack of serotonin has been linked to clinical depression
4. Endorphins

• involved in pain control
• many of our most addictive drugs deal with endorphins

Drugs can be...

• Agonists - make neuron fire
• Antagonists - stop neural firing

3 Types of Neurons

1. Sensory Neurons - (Afferent Neurons) Take info from the senses to the brain
2. Inter Neurons - Take messages from sensory neurons to other parts of the brain or to motor neurons
3. Motor Neurons - (Efferent Neurons)  - Take information from brain to the rest of the body

The Nervous System 

• The Central Nervous System - Brain and Spinal Cord
• Peripheral Nervous System - (PNS) all nerves that are not encased in bone. everything but the brain and spinal cord. Divided into 2 categories:

1. Somatic Nervous System - controls voluntary muscle movements and uses motor neurons
2. Autonomic Nervous System - controls the automatic functions of the body. Divided into 2 categories: 
1. Parasympathetic Nervous System - Automatically slows the body down after a stressful event. Heart rate and digestion speeds up
2. Sympathetic Nervous System - Flight or fight response. Automatically accelerates heart rate, breathing dilates pupils, slows down digestion.