03/16/14 Biological School

• The Nervous System- Starts with an individual nerve cell called a neuron.
• Parts of  a Neuron
• Cell body- the cell's life- support center.
• Neurotransmitters- Chemicals held in terminal buttons that travel through synapse gap.
• Terminal branches of axon- Form junctions with other cells.
• Synapse- A structure that permits a neuron to pass a chemical or electrical signal to another cell.
• Dendrites- Receive messages from other cells.
• Axon- Passes messages away from the cell body to other neurons, muscles, or glands.
• Neural impulse electrical signal traveling down the axon. 
• Myelin Sheath- Covers the axon of some neurons and helps speed neural impulses.

• How does a neuron fire?
• Resting potential: slightly negative charge.
• Reach the threshold when enough neurotransmitters reach dendrites.
• It is an electrochemical process
• Electrical inside the neuron. 
• Chemical outside the neuron (in the synapse in the form of a neurotransmitter)
• This action is called the Action Potential
• The All- or None Response
• The idea that either the neuron fires or it does not- no part way firing
• Like a gun
• Neurotransmitters
• Chemical messengers released by terminal buttons through the 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 has been linked to schizophrenia.
3. Seratonin
• Involved in mood control
• Lack of seratonin 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 neuron firing.
• Types of Neurons
• Sensory Neurons (Afferent Neurons)
• Take information from the senses to the brain.
• Inter Neurons
• Takes messages from sensory neurons to other parts of the brain or to motor neurons.
• Motor Neurons (Efferent Neurons)
• Take information from brain to the rest of the body.
• Central Nervous System (CNS)
• The brain and spinal cord.
• Peripheral Nervous System
• All nerves that are not encased in boned.
• 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 at the body.
• Divided into two categories. The sympathetic and the parasympathetic.
• Sympathetic Nervous System
• Fight or flight response
• Automatically accelerates heart rate, breathing, dilates pupils, slows down digestion. 
• Parasympathetic Nervous System
• Automatically slows the body down after a stressful event.
• Heart rate and breathing slow down, pupils constrict and digestion begins.