Nervous System
Introduction to the Nervous System
Unit 9
Affixes
Ef-
Af-
Oligo-
Astro-
-ia
neuro-
-pathy
esthesi-
-alges
The nervous system is the control and communication center of the body, based on electrical changes (action potentials). It functions through a general overview of:
1. Sensory input: the body will receive stimuli via receptors
2. Integration: process the input to decide what should be done
3. Motor output: activates the effector organ to cause a response.
The nervous system has two main types of cells:
1. Neurons (nerve cells) that are excitable cells that respond to stimuli by conducting impulses to transmit signals
2. Neuroglia (or glial cells) are the support cells that provide nutrition, insulation, and help with signal transmission.
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Parts of the Neuron
1. Soma is the cell body that contains the nucleus and most organelles including tons of mitochondria
2. Dendrites are the main receptors of signals, also called the input region
3. Axons are the tail looking part that generstaes and trasmits nerve impulses. Also known as the conducting region or nerve fiber
4. Axon terminals are the ends of the axon that release neurotransmitters at a synpase when a nerve impulse is received, it is the secretory region
5. Myelin sheath: covers long axons to protect and electrically insulate them to increase the speed of nerve impulse transmission. The node of Ranvier are unmyelinated gaps in the myelin sheath that aid in increasing the velocity of nerve signal conduction.
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Key terminology
Nerve: bundles of axons that extend from the central nervous system to the rest of the body
Ganglion: collection of nerve cell bodies located in the body (not just the CNS)
Neurophysiology -
Action Potentials
Neurotransmitters
1. Epinephrine: fight or flight response; produced in stressful situations. Increases heart rate and blood flow
2. Norepinephrine: concentration, affects attention and responding actions in the brain. Contracts blood vessels, increasing blood flow
3. Dopamine: pleasure; addiction, motivation. People repeat behaviors that lead to dopamine release
4. Serotonin: mood regulation; contributes to well being and happiness. Helps with sleep cycle and digestive system regulation. Is affected by exercise and light exposure
5. Gamma aminobutyric acid (GABA): calming. Calms firing nerves in the CNS. High levels improve focus, low levels cause anxiety.
6. Acetylcholine: learning and muscle contraction. Released at the neuromuscular junction.
7. Glutamate: memory; most common NT. Regulates development and creation of nerve contacts.
8. Endorphins: euphoria. Released during exercise, excitement and sexual intercourse. Reduces pain.
