Animal Nervous Systems

Physiology of a Neuron( Brain cell) 

Dendrites: Receives stimuli 

Axon: Sends nerve impulses

Axon Terminals: Sends nerve impulses to other neurons 

Synapses: The gap in-between neurons as shown below a.k.a Synaptic cleft 

First Calcium gates open and calcium starts heading towards axon terminal then Synaptic Vesicle releases neurotransmitters which bind to postsynaptic receptors.

1) Acetylcholine: secreted at neuromuscular junctions allows muscle to stimulate

2) Epinephrine: Can treat severe asthma attacks and allergic reactions

3) Norepinephrine: Can treat low blood pressure and heart failure

4) Dopamine: Plays a major role in reward-motivated behavior. Can treat symptoms of shock by improving blood flow

5) Serotonin: Primarily found in the gastrointestinal tract, blood platelets. Can affect mood and social behavior, appetite and digestion, sleep, memory and sexual desire and function.

6) GABAGamma-aminobutyric acid: Inhibits or reduces the activity of the neurons or nerve cells

Potentials and Polarization 

When a neuron is not being stimulated it is said to be polarized .
Potassium ions are on the inside of the cell (negative) and Sodium ions on the outside of the cell ( Positive) 
*neuron is more negative in the inside 
  • These ions move across the membrane through the ACTIVE TRANSPORT PUMPS 

Resting potential: When the neuron is said to be polarized like explained above 

If there is more sodium rushing into the cell through the voltage-gated ion channels and potassium leaving the cell the neuron will become depolarized. 
*That is the inside of the cell is more positive . 
Action potential: When the stimulus is strong enough that is surpasses a certain threshold , allowing the cell to become depolarized.  When this fails it is called an all-or-nothing event 

Repolarization: The movement of Potassium out of the cell. 
Hyper polarization : When more Potassium ions leave the cell than it is needed for the polarized potential. 

Graded potential: When the neuron is said not to be polarized

Types Of Neurons

Sensory Nuerons: Receive initial stimulus 
Ex. The paws of a cat has sensory neurons on the hand that are stimulated by touch 

Motor Neurons: A nerve cell forming part of a pathway along which impulses pass from the brain or spinal cord to a muscle or gland.
ex. might stimulate muscle after sensory neuron senses touch 

Interneurons: Receive impulses from sensory neurons or send impulses to motor neurons 

Central Nervous System And Peripheral Nervous System 

Central Nervous System: Brain and spinal cord.
  • thought processes 
  • guides movement
  • registers sensations throughout the body
 injuries/ illnesses that can damage the CNS permanently are : 
  • - Parkinson's disease.
  • - Multiple sclerosis (MS).
  • -Amyotrophic lateral sclerosis (ALS).
  • -Alzheimer's disease.
  • -Huntington's disease.
  • -Peripheral neuropathies.

                             Peripheral Nervous System: Outside of the brain and spinal cord  ex. Legs and arms 
Sensory neurons all over body remind CNS of the stimuli . PNS is divided into the Somatic NS and the Autonomic NS

The Somatic Nervous System: Where all the awareness of the external environment comes from
This consists of 12 cranial nerves and Spinal Nerves

Autonomic Nervous system also has sub divisions and is dived into the sympathetic and parasympathetic NS. 

Autonomic NS Regulates the function of internal organs like the lungs and the heart.