The Nervous SystemJESSICA JOHNSON

What is the Nervous System?

Definition: the network of nerve cells and fibers that transmits nerve impulses between parts of the body

Function: The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts.

Central Nervous System

Definition: The central nervous system (CNS) controls most functions of the body and mind. It consists of two parts: the brain and the spinal cord. 

Function: The brain interprets our external environment, and the spinal cord lets the brain communicate with the rest of the body.

Main components: Brain and spinal cord

Peripheral Nervous System

Definition: The peripheral nervous system consists of the nerves that branch out from the brain and spinal cord.

Function: These nerves form the communication network between the CNS and the body parts. 

Main components: Ganglia outside of brain and the https://mcb.berkeley.edu/courses/mcb135e/central.htmlspinal cord

Cerebellum: receives information from the sensory systems, the spinal cord, and other parts of the brain and regulates motor movements. It coordinates voluntary movements such as posture, balance, coordination, and speech, resulting in smooth and balanced muscular activity.

Diencephalon: Contains hypothalamus and thalamus. The thalamus interprets sensations of sound, touch, taste, pain, pressure, temperature and touch. It also regulates some emotions and memory. The hypothalamus controls heartbeat, digestion, regulates the endocrine system, and normal body temperature. It interprets hunger and thirst, and regulates sleep, anger, and aggression.

Brain Stem: One of the most basic regions of the human brain, yet it is one of the most vital regions for our body’s survival. It forms the connection between the brain and the spinal cord, maintains vital control of the heart and lungs, and coordinates many important reflexes.

Neuron Impulse Outline Explained

Membranes are polarized or, in other words, exhibit a resting membrane potential. This means that there is an unequal distribution of ions (atoms with a positive or negative charge) on the two sides of the nerve cell membrane.

Two ions are responsible: sodium (Na+) and potassium (K+). An unequal distribution of these two ions occurs on the two sides of a nerve cell membrane because carriers actively transport these two ions: sodium from the inside to the outside and potassium from the outside to the inside.

An action potential is a very rapid change in membrane potential that occurs when a nerve cell membrane is stimulated. Specifically, the membrane potential goes from the resting potential (typically -70 mV) to some positive value (typically about +30 mV) in a very short period of time (just a few milliseconds).

Neuron Impulse Ouline Explained II

Action potentials occur only when the membrane in stimulated (depolarized) enough so that sodium channels open completely. The minimum stimulus needed to achieve an action potential is called the threshold stimulus.

The threshold stimulus causes the membrane potential to become less negative (because a stimulus, no matter how small, causes a few sodium channels to open and allows some positively-charged sodium ions to diffuse in).

If the membrane potential reaches the threshold potential (generally 5 - 15 mV less negative than the resting potential), the voltage-regulated sodium channels all open. Sodium ions rapidly diffuse inward, & depolarization occurs.

Neuron Impulse Outline Explained III

Refractory periods:

ABSOLUTE -

During an action potential, a second stimulus will not produce a second action potential (no matter how strong that stimulus is)

corresponds to the period when the sodium channels are open (typically just a millisecond or less)

RELATIVE -

Another action potential can be produced, but only if the stimulus is greater than the threshold stimulus

corresponds to the period when the potassium channels are open (several milliseconds)

the nerve cell membrane becomes progressively more 'sensitive' (easier to stimulate) as the relative refractory period proceeds. So, it takes a very strong stimulus to cause an action potential at the beginning of the relative refractory period, but only a slightly above threshold stimulus to cause an action potential near the end of the relative refractory period

Role of Neurotransmitters

Function: chemicals located and released in the braun to allow an impulse from one nerve cell to pass to another nerve cell.

When a neurotransmitter binds to a receptor on the postsynaptic side of the synapse, it changes the postsynaptic cell's excitability: it makes the postsynaptic cell either more or less likely to fire an action potential. If the number of excitatory postsynaptic events is large enough, they will add to cause an action potential in the postsynaptic cell and a continuation of the "message.“

IPSP: a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential.

EPSP: a postsynaptic potential that makes the neuron more likely to fire an action potential.

Polio

A virus that may cause paralysis and is easily preventable by vaccine

Many who contract polio don’t show symptoms or get sick. However, those who do get sick often develop paralysis, which can be fatal

Polio is very rare, with no cases in the US last year

This nervous system disorder can be treated with physical therapy, bed rest, pain relievers, and portable ventilators

Parkinson’s Disorder

A disorder of the central nervous system that affects movement, often tremors. Nerve cell damage in the brain causes dopamine levels to drop, leading to the symptoms of Parkinson’s.

Symptoms include: stiffness, slow movement, loss of balance, or a tremor in the hand.

This is a common disorder, with between 200,000-3,000,000 reported cases in the US annually.

Parkinson’s can’t be cured, but medication can help control the symptoms.

Bibliography

https://faculty.washington.edu/chudler/synapse.html

http://www.minddisorders.com/Kau-Nu/Neurotransmitters.html

http://people.eku.edu/ritchisong/301notes2.htm

http://innerbody.com

http://christopherreeve.org

http://training.seer.cancer.gov

http://healthtime.com

https://askabiologist.asu.edu/neuron-anatomy

http://wps.prenhall.com/br_morris_intro_psicologia_6/16/4119/1054528.cw/index.html

http://www.mayoclinic.org/diseases-conditions

https://mcb.berkeley.edu/courses/mcb135e/central.html