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Cell Membrane Phys, Derm-/Mytomes
Day 2
101
Anatomy
Graduate
01/19/2015

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Term
dermatome in greek
Definition
skin cutting
Term
area of the skin supplied by nerve fibers originating from a single dorsal nerve root
Definition
dermatome
Term
how are dermatomes named
Definition
according to the spinal nerve which supplies them
Term
why are the dermatomes of the limbs more complex than those of the trunk
Definition
dermatomes being pulled out as the limb buds form and develop during embryological development
Term
why do adjacent dermatomes overlap
Definition
overlapping innervation by adjacent dorsal roots
Term
in regards to dermatomes, if there is loss of afferent nerve function by one spinal nerve, what happens to sensation form the region?
Definition
not lost, but a reduction in sensitivity
Term
overlap of of dermatomes depends on what
Definition
modality
Term
what type of dermatome overlaps less?
Definition
pain dermatomes
Term
injury to a single dorsal root is more easily identified by examining for what
Definition
pain
Term
a group of muscles innervated by a single spinal nerve
Definition
myotome
Term
what all neurons and their processes bounded by
Definition
continuous plasma membrane
Term
what is the neuronal membrane formed by
Definition
phospholipid bilayer
Term
carbohydrate chains are found on what side of the phospholipid bilayer membrane
Definition
external side
Term
carbohydrate chains that are associated with membrane proteins are called what
Definition
glycoproteins
Term
which region of the bilayer faces outward, hydrophilic or hydrophobic
Definition
hydrophilic
Term
which region of the bilayer membrane faces inward
Definition
hydrophobic
Term
characteristic of the hydrophilic heads of the bilayer membrane
Definition
polar/charged
Term
characteristic of the hydrophobic tails of the bilayer membrane
Definition
lipid
Term
What substances are prevented from diffusing across the bilayer membrane
Definition
water-soluble substances
Term
Many processes carried out by nerve cells are initiated as a result of reactions occurring within the plasma membrane, what are these processes mediated by
Definition
integral/intrinsic proteins embedded in the lipid bilayer
Term
how can integral proteins move within the membrane?
Definition
laterally, rotate
Term
what do peripheral proteins attach to
Definition
integral proteins
Term
peripheral proteins can attach to integral proteins
Definition
within the extra- or intracellular surfaces of the membrane
Term
ionophores aka
Definition
channel proteins
Term
central pores that selectively allow specific ions to diffuse down their concentration gradients
Definition
channel proteins/ionophores
Term
in which directions can ions move in channel proteins
Definition
either direction
Term
if channel proteins are open only temporarily, what are they called
Definition
gated channels
Term
intrincis protein that maintains appropriate concentrations of ions on either side of the membrane by moving against their concentration gradient
Definition
pump proteins
Term
what is necessary for pump proteins to do their job effecively
Definition
expend considerable metabolic energy
Term
proteins that facilitate the movement of lipid-insoluble nutritients such as glucose into neuronal cytoplasm
Definition
carrier proteins
Term
proteins that provide high affinity binding sites for specific molecules present in the extracellular fluid
Definition
receptor proteins
Term
molecules that bind to receptor proteins
Definition
ligands
Term
following the interaction of a receptor protein with a ligand, what may be present to couple the receptor to enzymes within the neuron
Definition
transducer protein
Term
following the interaction of a receptor protein with a ligand, transducer proteins may be present to do what
Definition
couple the receptor to enzymes within the neuron
Term
plasma membrane proteins that perform neurotransmitter reuptake
Definition
neurotransmitter transporter proteins
Term
what type of proteins are neurotransmitter transporter proteins
Definition
glycoproteins
Term
transport of certain neurotransmitters from the synaptic cleft back into the presynaptic axon terminal
Definition
reuptake
Term
Plasma membrane proteins, have only one function. True/False?
Definition
False. Capable of being, for example, both receptor and channel protein
Term
Extracellular fluid is high in what ions
Definition
Na+, Cl-
Term
intracellular fluid is high in what ions
Definition
K+, negatively charged proteins
Term
Transmembrane potential typically
Definition
-70 mV
Term
3 factors involved in the establishment of the resting membrane potential
Definition
chemical(concentration) gradients, electrical gradients, electrochemical gradients
Term
[K+,K+,K+,K+]|[K+,K+]
Which way will the K+ flow? . Why?
Definition
R. Lower concentration on right, higher concentration on left.
Term
movement of ions across the cell membrane is called what
Definition
current
Term
the amount of current is inversely proportional to the ________ that separates the charges
Definition
resistance
Term
If resistance is high, current is
Definition
low
Term
If resistance is low, current is
Definition
high
Term
how can resistance in a cell membrane be changed
Definition
opening/closing ion channels
Term
sum of the chemical and electrical forces acting across the membrane
Definition
electrochemical gradient for a specific ion
Term
at rest Na+ ions are attracted into the cytosol, by the (-) charges on the inside of the cell membrane, resulting in which forces pushing Na+ into the cell
Definition
chemical and electrical
Term
what force tries to drive the K+ ions out of the cell
Definition
chemical gradient
Term
what 2 electrical forces keep the K+ within the cell?
Definition
attraction between the K+ and the (-) charges on the inside of the cell membrane, repulsion between K+ and (+) charges on outside of membrane
Term
what are the 3 states of gated channels
Definition
closed but capable of opening, open (activated), closed and incapable of opening (inactivated)
Term
gated channels aka
Definition
ion channels
Term
what are the 2 classes of gated channels
Definition
chemically regulated, voltage regulated
Term
what class of gated channel is most abundant on dendrites and cell body
Definition
chemically regulated channels
Term
why are chemically regulated channels most abundant at dendrites and cell body
Definition
areas where most synapses occur
Term
voltage regulated channels open/close in response to what
Definition
changes in transmembrane potentional
Term
in regards to voltage regulated channels, what is the key step in the generation of an action potential
Definition
opening of the channels
Term
what are the 2 gates the voltage regulated channel possesses?
Definition
activation gate, inactivation gate
Term
changes in the transmembrane potential that do not spread far from the area surrounding the site of stimulation are called what
Definition
graded (local) potentials
Term
in regards to graded(local) potentials, movement of Na+ across the membrane at one location causes what
Definition
depolarization of the surrounding membrane
Term
in regards to graded (local) potentials, teh change in the transmembrane potential and the area that is depolarized is directly related to what
Definition
number of Na+ channels opened
Term
in regards to graded (local) potentials, the more open channels, the more Na+ that enters resulting in what
Definition
greater depolarization
Term
in regards to graded (local potentials) opening of K+ channels would result in what,
Definition
K+ outflow rate would increase and the interior of the cell would become more negative
Term
in regards to graded (local potentials) opening of K+ channels would result in K+ outflow rate would increase and the interior of the cell would become more negative. Which would result in what?
Definition
hyperpolarization
Term
Both depolarization and hyperpolarizaiton move the transmembrane potential away from....
Definition
resting levels
Term
What must occur for the transmembrane potential to return to resting levels
Definition
removal of stimulus, restoration of normal membrane permeability
Term
graded (local) potentials: transmembrane potential is most affected where
Definition
at site of stimulation
Term
graded (local) potentials: transmembrane potential is most affected at site of stimulation, meaning what
Definition
effect decreases with distance
Term
graded (local potentials): transmembrane poteital is most affected at site of stimulation, how does the effect spread
Definition
passively due to local currents
Term
graded (local) potential change may involved what
Definition
depolarization or hyperpolarization
Term
graded (local) potential: the stronger the stimulus, the greater the change in the transmembrane, therefore
Definition
the larger the area affected
Term
before an action potential can begin, what must occur
Definition
an area of excitable membrane must be depolarized to threshold by local currents
Term
Action Potential generation: what happens as a result of an area of excitable membrane being depolarized to threshold
Definition
activation of Na+ channels followed by rapid depolarization
Term
action potential generation: as the Na+ channels are activated and rapid depolarization occur the cell membrane becomes more permeable to what
Definition
Na+
Term
action potential generation: during activation of Na+ channels, the cell membrane is more permeable to Na+, causing what to happen to the transmembrane potential
Definition
become more positive
Term
as the membrane reaches its target threshold (ex 30 mV) what happens to the Na+ gates
Definition
gates are inactivated and become closed
Term
as the membrane potential reaches its threshold (ex 30 mV) inactivation gates of the Na+ channels are closed due to what?
Definition
inactivation gates of voltage regulated Na+ channels close
Term
as the inactivation gates of voltage regulated Na+ channels close, what occurs at the same tiem
Definition
voltage regulated K+ channels open
Term
When the inactivation gates of voltage regulated Na+ channels close, and voltage regulated K+ channels open, what happens to the membrane potential
Definition
shifts back toward resting, repolarization begins
Term
at a potential of +30 mV, K+ ion movement is to the outside of the cell. Why?
Definition
electrical and chemical gradients favor K+ ion movement
Term
voltage regulated Na+ channels remain inactivated until the membrane potential reaches what
Definition
-60 mV
Term
Describe the state of voltage regulated Na+ channels when the membrane potential reaches -60 mV
Definition
closed, but capable of opening
Term
what happens to the K+ channels as the membrane reaches normal resting potential of -70 mV
Definition
begin closing
Term
Why is the closing of K+ channels delayed briefly
Definition
allows more than normal K+ ion to leave
Term
What happens as a result of K+ ions taking more time to leave, in terms of polarization?
Definition
transmembrane becomes more hyperpolarized, becoming even more negative than normal
Term
from the time an AP begins until the normal resting potential has stabilized is called
Definition
Absolute refractory period
Term
why can the membrane not respond during the absolute refractory period
Definition
all voltage regulated Na+ channels are either already open or are inactivated
Term
period when the transmembrane is between -60 mV and -70 mV
Definition
relative refractory period
Term
the transmembrane will not respond to additional depolarizing stimuli during this period
Definition
absolute refractory period
Term
during the relative refractory period, why must the depolarizing stimulus be larger than normal electrically?
Definition
membrane is hyperpolarized to some degree during the period
Term
during the relative refractory period, why must the depolarizing stimulus be larger than normal chemically
Definition
local current must deliver enough Na+ to counteract the loss of positively charged K+ through voltage regulated K+ channels
Term
difference between action potentials and graded potentials
Definition
APs affect the entire excitable membrane
Term
when the AP reaches the end of the axon it is identical to the one generated at the initial segment, this is known as what
Definition
continuous propagation
Term
Propagation of an AP in myelinated axons is referred to as what
Definition
saltatory propagation
Term
AP propagation: action potential begins at the initial segment, at the peak of the AP, the membrane potential becomes what
Definition
positive
Term
AP propagation: After the peak of the AP, the membrane potential becomes (+), developing a local current that does what
Definition
spreads in all directions
Term
AP propagation: when the local current develops and spreads in all directions, what occurs
Definition
depolarization of adjacent portions of the membrane
Term
AP propagation: When the initial semgent of the axon is depolarized to threshold, what occurs
Definition
AP develops there
Term
AP propagation: When the initial segment of the axon is depolarized to threshold, an AP develops there, what happens next
Definition
process continues in a chain reaction
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