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Nervous System
Lecture
75
Anatomy
Undergraduate 1
12/12/2011

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Term
nervous system function
Definition
sensory input, integration, and control of body
Term
CNS
Definition
composed of brain and spinal cord.
control center for body.
Term
autonomic system
Definition
(CNS)
integrate info and controls responses
medulla oblongata and hypothalamus
Term
medulla oblongata
Definition
heart rate, blood pressure, co2 and respiration
Term
hypothalamus
Definition
body temp, heart rate, blood pressure
Term
PNS
Definition
connects everything to CNS
it is all nerve tissue not of the brain or spinal cord
afferent and efferent cells
Term
afferent cell
Definition
PNS
cells that carry info to CNS from organs and skin
Term
efferent cells
Definition
PNS
carry info away from CNS
motor neurons
Term
somatic nervous system
Definition
part of the PNS
connects CNS with skeletal muscles
Term
autonomic nervous system
Definition
connects CNS and smooth muscle, cardiac muscle and glands
involuntary control of body and internal function
works with endocrine system
2 parts: sympathetic and parasympathetic
Term
sympathetic
Definition
fight or flight response
relaxes intestinal wall, increases sweating and heart rate
Term
parasympathetic
Definition
resting and digesting
contracts intestine, decreases sweating and heart rate
Term
neruogenesis
Definition
regeneration of neurons
located int he hippocampus and olfactory bulb
increased in low stress, exercise conditions
Term
Basic type of cells
Definition
supporting cells
neurons
Term
Supporting cells in body
Definition
outnumber neurons 50:1
1/2 weight of brain
smaller than neurons, protect them
Term
supporting cells CNS
Definition
astrocytes, oligodendrocytes, ependymal, microglia
Term
astrocytes
Definition
most numerous
presents antigens
maintains K+, neurotransmitters, blood flow to brain
Term
microglia
Definition
immune cell-macrophage
regulates brain communication
helps with neuron growth and connectivity
Term
oligodendrocytes
Definition
wrap around larger nerves
helps transmissions stay in nerve and travel faster
Term
ependymal cells
Definition
line central cavity of brain and spine
circulates cerebrospinal fluid
Term
Supporting cells in PNS
Definition
satellite and schwann cells
Term
satellite cells
Definition
PNS
surrounds neuron cell body, and controls chemical environment
Term
schwann cells
Definition
PNS
forms myelin sheath in PNS
removes damaged nerves
helps with nerve fiber regeneration
Term
neuron characteristics
Definition
long lived, dont reproduce, high metabolic rate
Term
needs of neurons
Definition
lots of O2 and glucose
20% body energy , 15% cardiac input
Term
neuron parts
Definition
cell body, dendrite, axon
Term
dendrite
Definition
short process that branches like a tree
receives input
Term
axon
Definition
only one per neuron
end branches are called telodendria
base of axon is spike initiation zone
has myelin sheath
Term
myelin sheath
Definition
phospholipid layer that increases speed of nerve impulses
protection and insulation
Term
neurofibral nodes
Definition
bare area on axon where AP is regenerated
Term
multipolar
Definition
at least two dendrites and axon
Term
bipolar
Definition
one axon, one dendrite
Term
unipolar
Definition
only one axon that is directly connected to dendrite
Term
ion channels
Definition
leakage and gated
Term
leakage channel
Definition
always open and passive
Term
gated channel
Definition
active transport and open/close
ligand gated, voltage gated, mechanically gated
Term
ligand gated
Definition
gated channel
opens in response to neurotransmitter, hormone, or ions
binding of chemical to gate opens it
Term
voltage channel
Definition
gated channel
open in response to current
used with AP's
activation gates open, inactivation gates close
Term
mechanical channels
Definition
gated channel
opens in response to sound waves, pressure and stretching
force distorts the channel open.
Term
resting membrane potential
Definition
positive on the outside, negative on the inside
oustide has more Na+. inside has more K+
75X more permeable to K than Na
sodium potassium pump prevents equilibrium
Term
ion pumps (sodium potassium)
Definition
driven by ATP
slower than open channel
moves 3 Na+ in, causes ATP to split, changes shape of gate, 2K+ go into gate, reconfigures and lets 2K+ out
Term
membrane potentials
Definition
graded and action potential
Term
depolarization
Definition
causes inside of membrane to be less negative
increases chance of AP
releases KE in form of current
Term
graded potential
Definition
local depolarization
produced by stimulation of voltage gates for Na+
Term
action potential
Definition
only in neurons and muscle cells
doesnt degrade with distance
four steps:
resting state, depolarizing phase, repolarizing, and undershoot
Term
step one of AP
Definition
resting membrane potential is -70 mV
Term
step two of AP
Definition
depolarizing phase
local current depolarizes spike initiation
Na+ gates open
interior membrane gets more positive until -55mV (threshold)
becomes self generating due to positive feedback
at 30mV, Na+ inactivation gates close
Term
step 3 of AP
Definition
repolarizing phase
K+ moves out of cell and cell repolarizes to resting level
Term
step 4 of AP
Definition
undershoot
slightly more K+ leaves than necessary
sodium potassium pump restores ionic balance
Term
propagation of AP
Definition
movement of Na+ causes other Na+ gates to open
Term
coding for stimulus intensity
Definition
FM and AM
FM is used because all AP are of equal magnitude
Term
refractory period
Definition
when a neuron cannot generate AP
absolute and relative
Term
absolute refractory period
Definition
top of graph, causes AP to go in one direction
Term
relative refractory period
Definition
follows absolute refractory period
Na+ gates are resting and K+ are open
at this point threshold is higher than resting-normal stimulus cannot generate multiple AP
strong stimulus can though
Term
speed of AP
Definition
depends on axon diameter and myelin sheathing
larger diameter, faster the potential
Term
myelin sheath
Definition
prevents degradation of AP
bare spots between sheath is node of ranvier
all Na+ and K+ is located here
AP jumps from node to node-salutatory conduction
Term
myelin sheath
Definition
prevents degradation of AP
bare spots between sheath is node of ranvier
all Na+ and K+ is located here
AP jumps from node to node-salutatory conduction
Term
synapse
Definition
junction between two neurons or neuron and effector cell
electrical, excitatory, chemical, inhibitory
Term
electrical synapse
Definition
connected by bridged junction
permits rapid, synchronization of AP
found in brain
Term
chemical synapse
Definition
most common synapse that uses neurotransmitter
axon terminal, synaptic cleft, receptor region
Term
excitatory synapse
Definition
neurotransmitter depolarizes the postsynaptic membrane
binding of neurotransmitter causes opening of Na+ channels
Term
inhibitory synapse
Definition
neurotransmitter hyperpolarizes the postsynaptic membrane
opens ion channel that increases membrane potential to -80mV
Term
inactivation by enzymatic degradation
Definition
neurotransmitter is broken down by an enzyme
Term
inactivation by uptake
Definition
transporter proteins take neurotransmitter back into axon terminal
Term
types of neurotransmitters
Definition
acetylcholine, biogenic amines, amino acids, neuropeptides, ATP, and NO2
Term
acetlycholine
Definition
used in skeletal muscle stimulation and some autonomic nervous system
Term
biogenic amines
Definition
serotonin, epinephrine
function as emotional behavior and clock
Term
amino acids
Definition
only used in CNS
Term
neuropeptides
Definition
endorphins
mediator of pain signals
Term
ATP
Definition
used in CNS and PNS
Term
NO2
Definition
used as a vascular toning agent
Term
diverging circuit
Definition
one incoming fiber triggers response in increasing # of neurons
amplifies signal
Term
converging circuits
Definition
terminates in one neuron
concentrates stimulation into one place
Term
reverberating circuits
Definition
signal goes through a series of neurons, each of which is connected to a previous one. signal is rejuvenated
continuous signal until one neuron is inhibited
used in rhythmic activities
Term
parallel after discharge circuits
Definition
single neuron stimulates several which then stimulate a single output neuron
burst of impulses after initial input
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