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Nervous System 1

Chapter 9. nervous system unit in Anatomy, physiology,& disease 2009
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Central nervous system (CNS)
Brain & spinal cord
Peripheral nervous system (PNS)
Everything outside The brain & spinal cord that represents the input & output pathways
Sensory system
Input side or devices. Handled by brain & spinal cord
Motor system
Output side . Carries out orders from the brain & spinal cord
Somatic nervous system
Skeletal movements or other voluntary movements
Autonomic nervous system
Controls smooth & cardiac muscle in your organs & glands. Involuntary movement
Parasympathetic branch
Resting & digesting, normal body functioning
Sympathetic branch
Fight or flight, alert system
Nervous tissue
No epithelium, connective, or muscle tissue. Made up of 2 different types of cells
Neuroglia & neurons
The 2 cells nervous tissue is made up of
Neuroglia
Also known as glial cells are specialized cells in nervous tissue that allow it to perform nervous system functions. In CNS there are 4 types of glial cells
Astrocytes
Metabolic & structural support cells that hold neurons & blood vessels close together
Microglia
Attack microbes & remove debris
Ependymal cells
Cover surfaces & lining cavities
Oligodendrocytes
Hold nerve fibers together and make the lipid insulation called myelin
Schwann cells
Make myelin for the PNS
Satellite cells
Support cells for the PNS
Neurons
Alll of the control functions of nervous system
Dendrites
Receive info from enviroment or other cells & carries info to cell body
Body
Info received from dendrites travels here & then travels down to axon
Axon
Generates and sends signals to other cells
Axon terminals
Signals from axon travel down here and connects to a receiving cell
Synapse
Space between axon terminal and receiving cell
Sensory neurons
Input neurons. Carry impules fron skin & sensory organs to spinal cord and brain
Motor neurons
Output neurons. Carry messages from brain & spinal cord to muscles and glands
Interneurons
Also known as association neurons that carry info between neurons
Excitable cell
Carries small electrical charges when stimulated
Resting cell or polarized
Cell not stimulated or excited. Negatively charged
Depolarized
Cell more poaitive at rest. Sodium gates fly open letting positive soduIm ions in
Repolarization
Negatively charged again. Potassium is positively charged and leaves the cell and tAkes its positive cells. Becoming more negatively charged so cell returns back to rest
Hyperpolarized
Cell overshoots its charge and becomes more negatively charged when at rest
Refractory period
Cell is unable to accept another stimulus until it repolarizes
Action potential
Cell moving thru depolarization, repolarization, and hyperpolarization
Threshold
Current generated from stimulus is too weak--making action not possible
Local potentials
Size or amount of stimulus determines the excitement of the cell
Impulse conduction
Once action potential is formed, it travels down the axon from the cell body to the terminal
Myelin
Lipid insulation or sheath formed by oligodendrocytes in CNS &schwann in PNS. myelinated cells look white. Unmyelinated cells look gray. Myelin prevent ions from passing thru channels b/c ions are water soluble myelin is lipid
Nodes of ranvier
Between adjacent glial cells are tiny bare spots
Axon myelinated
When axon is wrapped in myelin
Axon unmyelinates
Action potential can only flow down axon by depolarizing each and every cell(slow process)
Multiple sclerosis (MS)
Disorder where myelin in CNS is destroyed. Areas w/out myelin, impulse conduction is slow or impossible. Areas of damaged myelin can have plaques or scarred areas. Cause is propably auto-immune attack. Symptoms including problems with vision, balance , speech, and movement. Most likely in women and people under 50
Relapsing-remitting symptomatic flare-ups( relapse), then period of time where patient has no symptoms(remission)
...
Chronic progressive
Has no remission periods;patients become steadily disabled