nervous system packet Flashcards
3 major functions of the nervous system
sensory input (stimuli detected and message sent to brain and spine. ) integration (process of combining information from many sources) motor output (motor neurons receive output and sends out response)
neuroglia
- supporting cells found in the CNS
- mitotic and responsible for most brain neoplasms
- functions essential to the survival & functionality of neurons
- preserves the physical and biochemical structure of neural tissue
- outnumber neurons
location of Schwann cells
PNS
location of satellite cells
PNS
Schwann cells
a type of “support” cell in the PNS.
satellite cells
glial cells that cover the surface of nerve cell bodies in sensory, sympathetic and parasympathetic ganglia
neurons
respond to stimuli
-perform all communication, information processing, and control functions of the nervous system
astrocytes
- make up almost 50% of the volume of neural tissue in the CNS
- function: axon guidance and synaptic support and, control of the blood brain barrier and blood flow
- bulbous ends cling to capillaries
microglia
- engulf invading microorganisms and dead neural tissue
- in the CNS
ependymal cells
-line the central cavities of the brain
oligodendrocytes
-wrap cytoplasmic extensions around thick neuron fibers in CNS
axon
- conducts impulses away from the cell body
- process called a nerve fiber
- conducting component
axonal terminal
-releases neurotransmitters
cell body
- location of nucleus
- located and protected within the CNS
- site of biosynthetic activities
dendrite
- conducts local currents toward the soma
- short, tapering, diffusely branched extension from the cell body
- receptive region
myelin sheath
- increases the speed of impulse transmission
- -formed by schwann cells
- in PNS
- patchy disappearance in multiple sclerosis
nissl bodies
-clustered ribosomes and rough ER
axon hillock
-trigger zone
axon terminal
-secretory components
three special characteristics of neurons
extreme logetivity
amitotic
high metabolic rate
ganglion
-collection of cell bodies found outside the CNS
synapse
-junction or point of close contact between neurons
neurotransmitters
-chemicals released by neurons that stimulate other neurons, muscles, or glands
nodes of ranvier
-gaps in a myelin sheath
tract
-bundle of axons in the CNS
nucleus
-collection of cell bodies found within the CNS
stimuli
-changes, occurring inside or outside the body, that activate the nervous system
bipolar neuron
function: optic and auditory
- very rare
unipolar neuron
function: sensory
- neuron that transmits impulses from pain receptors in your skin to your spinal cord
multipolar neuron
function: motor and associative neurons
- neuron that excites skeletal muscle cells
resting neurons
- inside is negative relative to its outside
- cytoplasm contains more K+ and less Na+ than does the extracellular fluid
- a charge separation exists at the membrane
- electrochemical gradient for the movement of Na+ across the membrane is greater than that for K+
- membrane is more permeable to K+ than Na+
depolarization
- 50 to +30 mV
- a voltage change that brings a nueron closer to its threshold for firing
- membrane potential becomes less negative and moves toward 0
action potential
+30 mV
- called the nerve impulse
- self- propagated depolarization
- all or none electrical event
- results from the opening of voltage regulated ionic gates
- characterized by a rapid polarity reversal
repolarization
+30 to -60 mV
hyperpolarization
- constant up and down from -70 to -80mV
- a voltage change that reduces the ability of a neuron to conduct a impulse
- causes membrane potential to become more negatived
absolute refractory period
-period when a neuron cannot be restimulaed because its Na+ gates are open
depolarization
-process by which the resting potential is decreased as Na+ ions move into the axon
polarized
-state of an un stimulated neuron’s membrane
relative refractory period
-corresponds to the period of repolarization of the neuron
repolarization
-period (event) during which K+ions move out of the axon
sodium- potassium pump
-mechanism by which ATP is used to move Na+ ion out of the cell and K+ ions into the cell;
Neural tissue
-forms organs (brain, spinal cord)
CNS
Central nervous system
- brain & spinal cord
- made of neural tissue, blood vessels, & various connective tissues
- function: integrating, processing, & coordinating sensory data & motor commands
PNS
Peripheral nervous system
- includes neural tissue outside the CNS
- function: delivers sensory information to the CNS & carries out motor commands to peripheral tissues & systems
Pairs of nerves
Cranial- 12
Spine-31
2 divisions of PNS
Afferent & efferent
Afferent
Brings sensory information to CNS
Receptor
Efferent
Carries motor commands from the CNS to muscles, glands, & adipose tissue
(Effectors)
threshold
- point at which an axon “fires”
- membrane potential at which the outward current carried by K}+ is exactly equal to the inward current carried by Na+
subthreshold
-term for a weak stimulus
frequency of impulses
-codes for intensity of the stimulus
graded potential
- local change in membrane potential in which current flow is quickly dissipated
- results from the opening of chemically regulated gates or energetic stimuli
impulses
-faster when the axon is larger in diameter
gated sodium channels
-concentrated at the nodes of ranvier of myelinated axons
blocking nerve impulses
caused by reducing membrane permeability to sodium ions
