The Nervous System

The nervous system: it starts with an individual cell called a neuron

How does a neuron fire?

-resting potential: slightly negative charge

-reach the threshold when enough neurotransmitters reach dendrites

-go into action potential (firing)

The all or none response: the idea that either the neuron fires it or does not

-no part firing 

-like a gun

Neurotransmitters: are chemical messengers that are released by internal buttons through the synapse

Acetylcholine (ACH): 

• deals with motor movement and memory
• too much and you will...
• too little and you will...
• lack of ACH has been linked to Alzheimer's disease

Dopamine:

• deals with motor movement and alertness
• lack of dopamine had been linked to Parkinson's disease
• too much had been linked to schizophrenia

Serotonin: 

• involved in mood control
• lack of serotonin had been linked to clinical depression

Endorphins: 

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

Drugs can be...

• agonists: make neuron fire
• antagonists: stop neural firing
• reuptake inhibitors: block neurotransmitters from entering the neyron

Norepinephrine: helps control alertness and arousal. An undersupply can lead to depression, an oversupply can lead to manic symptoms

GABA (gamma-aminobutytic acid): major inhibitory neurotransmitters. An undersupply can lead to tremors, seizures, and insomnia

Glutamate: major excitatory neurotransmitters; involved in memory. Oversupply can overstimulate the brain leading to migraine (this is ehy some people avoid MSG in food)

Types of neurons

1. Sensory neurons (adherent neurons): take information 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 

Central nervous system: spinal cord and brain 

Peripheral nervous system: 

• all nerves that are not encased in bone 
• everything but the brain and spinal cord
• is divided into two categories...somatic and autonomic

Somatic nervous system: 

• controls voluntary muscle movement
• uses motor (efferent) neurons

Autonomic nervous system: controls the automatic functions of the body 

• divided into two categories...the sympathetic and the parasympathetic

Sympathetic nervous system:

• flight or fight response
• automatically accelerate heart rate, breathing, dilated pupils, slow down digestion

Parasympathetic nervous system:

• automatically slows the body down after a stressful event
• heart rate and breathing slow down, pupils constrict and digestion speeds up

Reflex: normally sensory (afferent) neurons take info up through spine to the brain 

-some reactions occur when sensory neurons reach the spinal cord

The endocrine system: a system of glands that secrete hormones

-similar to nervous system, except hormones work a lot slower than neurotransmitters