Nervous System Controlling your body’s movements and senses

Nervous System System in charge of sending signals throughout body ◦sent by cells changing what chemicals are in and out of the cell, creating a difference of charge ◦Quick change in chemical content tells the cell to release chemicals called neurotransmitters ◦These chemicals, if in a high enough concentration, make the next nerve send a signal further down.

Overall Structure Nervous system divided in many ways ◦Central vs. peripheral  Brain/spinal cord vs. all others ◦Somatic vs. autonomic  Somatic- voluntary (muscular movement)  Autonomic- involuntary (smooth muscle- lines organs) ◦ Sympathetic vs. parasympathetic  Sympathetic- prepares for stress  Parasympathetic- relaxes after stress  *Many organs have nerves from both

Structure of a Neuron

Dendrite- reaches out into body in search of signal ◦Constantly monitoring how much of the signal is out (pressure, chemical, etc.) Axon- Once sent, carries the signal length of the neuron Myelin- coating on nerve preventing signal from leaking out Terminal button- When signal reaches, releases chemical signal telling next neuron to pass on the message

Different Types of Nerves Sensory (afferent) neuron- receives signal from pressure, chemical, heat, or visual Associated neuron- spinal cord and brain- carries signal to be processed Efferent (motor) neuron- sends signal to respond to initial stimulus

Active Transport Cell pumps as much potassium as possible into cell and removes as much sodium as it can ◦Moving chemicals from LOW to HIGH concentration, against the way they want to move ◦This uses a tremendous amount of ATP!

Action Potential/Depolarization Depolarization- when the nerve loses its difference of K/NA Action potential- the sending of the signal down the nerve All-or-none response!

Impulse Impulse- when a nerve sends a signal ◦All or none- nerves don’t send signals of varying strength- they either send or they don’t. The stronger the feeling, the more nerves are sending the signal Nerves hold high amounts of potassium, and send out lots of sodium When signal sent, “doors” in nerve open to allow chemicals to balance ◦Chemical change moves down nerve, stimulating chemical release at terminal

Synapse As signal reaches end of neuron, the terminal button releases chemicals into a small area between the button and the dendrites of the next nerve If enough nerves send the signal, then there will be enough chemical message to make the next nerve depolarize

Reflex Most signals must travel to brain to be processed before body can react Reflexes save time- only have to be sent to spinal cord for processing

Nervous System Problems Paralysis Parkinson’s Disease Fibromyalgia Huntington’s Disease

Paralysis Paralysis occurs generally as a result of the brain losing communication with the rest of the body ◦Often from cut in spinal cord  Current technologies cannot repair nerve damage ◦Example- Kevin EverettKevin Everett ◦Site of cut in cord determines how far down the messages from the brain can be sent

Parkinson’s Disease Degeneration of dopamine receptors in brain ◦Cause unknown, linked to head trauma Dopamine is brain’s chemical signal for muscle control ◦Results in difficulty with tasks requiring manual dexterity ◦Eventually leads to inability to walk or move if left untreated Can be treated with dopamine reabsorption inhibitors or extra dopamine

Fibromyalgia Characterized by widespread, unpredictable pain Diagnosis through ruling out other neurological disorders ◦Similar symptoms to MS, ALS, etc. Cause unknown, but has been linked to high childhood stresses, and has been shown to cause changes in brain (don’t know if disease causes change or change causes disease)

Huntington’s Disease Dominant genetic disorder Gene for protein huntingtin ◦Mutated gene leads to protein that builds up and damages parts of the brain ◦Results in dementia and severe confusion, and eventually death Prognosis- generally about 20 year survival from onset ◦Severity and age of onset depends on severity of mutation in gene