Chapter 3 - The Central Nervous System II Flashcards
0
Q
Depolarization
A
- a reduction in the magnitude of the negative membrane potential - the cell moves closer to 0 mV - fewer charges are separated than at resting potential
1
Q
Polarization
A
- Charges are separated across the plasma membrane - any time the value of the membrane potential is other than 0mV
2
Q
Repolarization
A
- the membrane returns to resting potential after having been depolarized
3
Q
Hyper polarization
A
- an increase in the magnitude of the negative membrane potential - the membrane becomes more polarized than at resting potential
4
Q
Leak channels
A
- a type of channel - open all the time, permitting unregulated leakage of their chosen ion across the membrane thr/ the channels
5
Q
Gated channels
A
- a type of channel - gates that can alternately be open, permitting ion passage through the channels; or closed, preventing ion passage through the channels
6
Q
Voltage gated channels
A
- a type of gated channel - open or close in response to changes in membrane potential
7
Q
Chemically gated channels
A
- a type of channel - change conformation in response to the binding of a specific chemical messenger to a membrane receptor in close association with the channel
8
Q
Mechanically gated channels
A
- a type of gated channel - respond to stretching or other mechanical deformation
9
Q
Thermally gated channels
A
- a type of gated channel - reposes to local changes across the membrane, causing membrane potential to fluctuate
10
Q
Graded potentials
A
- local changes in membrane potential that occur in varying grades or degrees of magnitude or strength -
11
Q
Current
A
- any flow of electrical charges - refers to passive flow between the active and adjacent resting regions on both the outside and inside of a neuron’s membrane -
12
Q
Resistance
A
- the hindrance to electrical charge movement - the lower the resistance, the greater the flow of ions -
13
Q
Action potentials
A
- brief, rapid, large (100mV) changes in membrane potential during which the potential actually reverses, so that the inside of the excitable cell transiently becomes more positive than the outside
14
Q
Threshold potential
A
- typically between -50 and -55mV - an explosive depolarization occurs
15
Q
After hyper polarization
A
- the inside of the membrane briefly becomes even more negative than usual - -90mV
16
Q
Contiguous conduction
A
- the means by which an action potential is propagated through a non myelinated nerve fiber - local current flow between an active and adjacent inactive area brings the inactive area to threshold, triggering an action potential in a previously inactive area
17
Q
Absolute refractory period
A
- one of the two components of the refractory period - the time period when a recently activated patch of membrane is completely refractory to further stimulation - occurs from threshold to depolarization
18
Q
Relative refractory period
A
- one of two refractory periods - follows the absolute refractory period during which the intimation of a second action potential is inhibited but not impossible - a second action potential can be produced only by a triggering event considerably stronger than usually necessary - occurs during hyper polarization
19
Q
All-or-nothing law
A
- an excitable membrane either responds to a triggering event with maximal action potential that spreads nondecrementally throughout the membrane, or it does not respond with an action potential at all
20
Q
Myelinated fibres
A
- Neuronal axons covered at regular intervals with insulative myelin
21
Q
Myelin
A
-an insulative lipid covering that surrounds myelinated nerve fibres at regular intervals along the axon
22
Q
Obliodendrocytes
A
- myelin forming cells in the brain
23
Q
Schwann cells
A
- myelin forming cells in the PNS
24
Q
Nodes of Ranvier
A
- the portions of a myelinated neuronal axon between the segments of insulative myelin, the atonal regions where the axonal membrane is exposed to the ECF and membrane potential exists
25
Q
Saltatory conduction
A
- the mess by which an action potential is propagated throughout a myelinated fiber, with the impulse jumping over the myelinated regions from one node to the next
26
Q
Innervate
A
- when a neuron terminates on a muscle or a gland
27
Q
Synapse
A
- the specialized junction between two neurons where an action potential in the presynaptic neuron influences the membrane potential of post synaptic neuron by means of the release of a chemical messenger that diffuses across the small cleft that separates the two neurons
28
Q
Presynaptic neuron
A
- the neuron that conducts it’s action potentials twrds a synapse
29
Q
Synaptic knob
A
- the bulbous structures on the end of an axon, each of which contains many synaptic vesicles
30
Q
Synaptic vesicles
A
- store various neurotransmitters that are released at the synapse - release is regulated by a voltage dependent calcium channels
31
Q
Neurotransmitter
A
- the chemical messenger that is released from the axon terminal of a neuron in response to an action potential and influences another neuron or an effector with which the neuron is anatomically linked
32
Q
Post synaptic neuron
A
- the neuron that conducts it’s action potentials away from the synapse
33
Q
Synaptic cleft
A
- the space between toe nerve cells In which neurotransmitters cross over
34
Q
Sub synaptic membrane
A
- the portion of the post synaptic cell membrane that lies immediately beneath a synapse and contains receptor sites for the synapse’s neurotransmitter
35
Q
Excitatory synapse
A
- synapse in which the post synaptic neurons response to neurotransmitter release is a small depolarization of the post synaptic membrane, bringing the membrane closer to threshold
36
Q
Inhibitory synapse
A
- synapse in which the post synaptic neuron’s response to neurotransmitter release is a small hyper polarization of the post synaptic membrane, moving the membrane farther from threshold
37
Q
Grand post synaptic potential
A
- represents spatial or temporal summation of many small potentials - temporal and spatial summation dictated by the rates of firing of many presynaptic neurons jointly control the grand membrane potential in the body of a single post synaptic cell
38
Q
Temporal summation
A
- the summing of several post synaptic potentials occurring very close together in time bc of successive firing of a single presynaptic neuron
39
Q
Spatial summation
A
- the summing of several post synaptic potentials arising from the simultaneous activation of several excitatory (or several inhibitory) synapses
