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84 Cards in this Set

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System controls and integrates all body activities within limits that maintain life.
Nervous System
3 basic functions of nerve tissue:
1. Sensing - changes with sensory receptors internally and externally.
2. Integration - (interpreting, remembering) changes in the internal and external environment.
3. Respond - (reacting) to changes with effectors by muscular contractions (smooth, cardiac, and skeletal) and grandular secretions.
The nervous system is made of:
the brain, cranial nerves, spinal cord, spinal nerves, ganglia, enteric plexuses, and sensory receptors.
What are the two major divisions of the nervous system?
Central and peripheral nervous system
Made of the brain and spinal cord.
Central nervous system (CNS)
Made of the cranial and spinal nerves that contain both sensory and motor fibers.
Peripheral nervous system (PNS)
The PNS connects CNS to muscles, glands, and all sensory receptors. The PNS can be subdivieded into what?
Somatic and autonomic nervous system
Voluntary, neurons travel from the skin and special sensory receptors to the CNS and motor neurons travel to skeletal muscle tissue.
Somatic nervous system
Involuntary, sensory neurons travel from visceral organs to the CNS and motor neurons travel to the smooth and cardiac muscles and glands.
Autonomic nervous system
(fight or flight); explain effects on organs
Sympathetic division
(rest and repose); returns the body to normal; rest and digest
Parasympathetic division
Involuntary sensory and motor neurons control the GI tract. The neurons function independently of ANS and CNS.
Enteric nervous system
functional unit of nervous system. Most do not divide, they have the capacity to produce action potential.
made of a single nucleus with a prominent nucleolus, nissl bodies (rough ER), neurofilaments which give the cell shape and support, and microtubules that move material inside the cell.
Cell body
carry messages into the cell body; short, highly branched, and unmyelinated (wires been stripped away).
carry impulses away from the cell body; long, thin, cylindrical process of the cell.
Side branches (collaterals) of the axon end in fine processes called:
axon terminals
They contain vesicles filled with neurotransmitters.The swollen tips of an axon are called:
synaptic end bulbs
(lock jaw) bacteria that enters the body through the axons of neurons. Disrupts motor neurons and causes painful muscle spasms.
Clostridum tetani
Viruses that also enter the axon and go to the cell body and CNS.
Rabies & herpes viruses
Neurons are classified according to the number of processes that extend away from them.
1. Unipolar neuron- 1 process
2. Bipolar neuron- 2 processes
3. Multipolar neuron- have many dendrites and a single axon. Majority of the neurons in the CNS are of multipolar type.
(Afferent neurons) transport sensory information from the skin, muscles, joints, sense organs, and viscera to the the CNS.
(Efferent neurons) send motor nerve impulses to muscles and glands and other neurons.
(Association neurons) connect sensory to motor neurons. These make up 90% of the neurons in the body.
Interneurons (between two neurons)
Do not produce action potentials. They make up half of the volume of the CNS. They are smaller than neurons and are 50X more numerous.
Neuroglial cells
Neuroglial cells divide rapidly to form tumors called:
There are 4 neuroglial cell types in the CNS:
astrocytes, oligodendrocytes, microglia, and ependymal
There are 2 neuroglial cell types in the PNS:
schwann and satellite cells
Star shaped cells, form the blood-brain barrier by covering blood capillaries, metabolize neurotransmitters, regulate potassium + balance, provide structural support.
Most common glial cell type, forms myelin sheath around more than one axon in the CNS. Schwann cells of PNS produce myelin around only individual axons.
small cells found near blood vessels. They're phagocytic- they clear away dead cells. They're derived from cells that also gave rise to macrophages and monocytes.
microglia cells
form epithelial membrane lining cerebral cavities and central canal. They produce cerebrospinal fluid (CSF).
flat cells surrounding neuronal cell bodies in peripheral ganglia. They support neurons in the PNS ganglia (group of cells).
satellite cells
Schwann cells encircle PNS axons. Each cell produces part of the myelin sheath surrounding an axon in the PNS.
Schwann cells
a lipid and protein covering that is produced by Schwann cells.
cytoplasm and nucleus of Schwann cells
neurilemma (nerve cell membrane)
plasma membrane of the Schwann cell
myelin sheath
the gaps of Schwann cell are called the:
nodes of Ranvier
myelin fibers appear what color
acts as an "ion insulator." They speed conduction of nerve impulses. They allow nerve impulse to jump and slide.
Slow, small diameter fibers, gray. They're only surrounded by neurilemma but no myelin sheath wrapping.
unmyelinated fibers
myelinate axons in the CNS
myelinated processes (white in color)
white matter (fat)
nerve cell bodies, dendrites, axon terminals, bundles of unmyelinated axons and neuroglia (gray color).
gray matter (no insulation)
In the spinal cord
gray matter forms an H-shaped inner core surrounded by white matter
In the brain
a thin outer shell of gray matter covers the surface and is found in clusters called nuclei inside the CNS
Neurons are excitable due to
the voltage difference created by a flow of the ions Na and K across the neuron membrane
occurs because of the unequal distributions of ions which causes the membrane to the "charged"
Resting membrane potential
More negative ions (K) are found along the inside of the cell membrane and more positive ions ( Na and Cl= Salt) are along the outsideof the membrane at rest
Resting membrane potential
potential energy difference is
-70mv and the cell is said to be "polarized"
always open, this is what allows the K to leak out of the cell for the action potential to occur.
leakage (nongated) channels
open and close in response to stimulus, this causes excitablitliy.
gated channels
open in response to change in voltage. Ex: electricity
voltage gated
open and close in response to chemical stimuli such as hormone and neurotransmitters.
open with mechanical stimulation
mechanically gated
open and close due to light stimulation
membrane becomes more negative on the inside
membrane becomes more positive on th inside. Na come in
with stimulation, an action potential either happens one specific way or not at all, lasts 1/1000 of a second.
all-or-none principle
period of time during which the neuron cannot generate another action potential
refractory period of action potential
even a very strong stimulus will not begin another action potential
absolute refractory period
a supra-threshold stimulus will be able to start an action potential, extra gates will have to open to start an action potential.
relative refractory period
traveling action potential is called a
nerve impulse
prevent opening of voltage-gated sodium channels. The nerve impulse cannot pass along the anesthetized nerve, and the CNS doesn't perceive the pain.
local anesthetics
blocks the sodium gates
Novacaine and lidocaine
occus in unmyelinated fibers-it is a step-by-step depolarization of each portion of the length of the neuron.
continuous conduction
occurs in myelinated fibers. The depolarization only occurs at the nodes of Ranvier where there is a high density of voltage-gated ion channels. The impulse jumps from node to node and is much faster.
saltatory conduction
action potential reaches the end bulb and the calcium channels open.
chemical synapses
flows inward which triggers the release of neurotransmitters.
crosses the synaptic cleft and binds to the ligand-gated receptors, the more released the greater the change in potential of the postsynaptic cell.
information can only travel from the dendrite to the cell body to the axon and away from the neuron because
the neurotransmitters are located at the end of the axon.
removed by diffusion into the blood stream, enzymatic degradation (ex: acetylcholinesterase degrades acetylcholine), or uptake by neurons.
anything that enhances a neurotransmitter such as a drug that mimics a natural neurotransmitter
anything that blocks the action of a neurotransmitter
24-48 hours after injury Nissl bodies break up into fine granular masses.
occurs by 3-5 days. This is a break down of the axon and myeline sheath distal to the injury, retrograde degeneration occurs back one node.
Wallerian degeneration
autoimmune disorder causing destruction of myeline sheaths in the CNS. Symptoms include muscular weakness, abnormal sensations or double vision.
Multiple Sclerosis (MS)
second most common neurological disorder. Affects 1% of the population. Characterized by short, recurrent attacks initiated by electrical discharges in the brain.
associated with tumors, vaccination, bacterial infections. possible paralysis
Guillain- Barre syndrome
malignant tumor that consists of immature nerve cells
burning unpleasant tiggling feeling, associated with diabetics
carried by rabbits and squirrels, fatal disease caused by a virus that reaches the CNS. Transmitted by the bite of an infected animal/mammal. Symptoms are excitement, aggressiveness & madness followed by paralysis and death.
During depolarization, what moves out.
potassium moves out
Order of action potential
1. Potassium channels open
2. Membrane is depolarized
3. Sodium ions diffuse inward
4. Repolarization of membrane