Nervous System 1

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Chapter 9. nervous system unit in Anatomy, physiology,& disease 2009

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

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