Chapter 3 - The Central Nervous System II

Question 0

Depolarization

Answer 0

• 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

Question 1

Polarization

Answer 1

• Charges are separated across the plasma membrane - any time the value of the membrane potential is other than 0mV

Question 2

Repolarization

Answer 2

• the membrane returns to resting potential after having been depolarized

Question 3

Hyper polarization

Answer 3

• an increase in the magnitude of the negative membrane potential - the membrane becomes more polarized than at resting potential

Question 4

Leak channels

Answer 4

• a type of channel - open all the time, permitting unregulated leakage of their chosen ion across the membrane thr/ the channels

Question 5

Gated channels

Answer 5

• a type of channel - gates that can alternately be open, permitting ion passage through the channels; or closed, preventing ion passage through the channels

Question 6

Voltage gated channels

Answer 6

• a type of gated channel - open or close in response to changes in membrane potential

Question 7

Chemically gated channels

Answer 7

• 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

Question 8

Mechanically gated channels

Answer 8

• a type of gated channel - respond to stretching or other mechanical deformation

Question 9

Thermally gated channels

Answer 9

• a type of gated channel - reposes to local changes across the membrane, causing membrane potential to fluctuate

Question 10

Graded potentials

Answer 10

• local changes in membrane potential that occur in varying grades or degrees of magnitude or strength -

Question 11

Current

Answer 11

• 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 -

Question 12

Resistance

Answer 12

• the hindrance to electrical charge movement - the lower the resistance, the greater the flow of ions -

Question 13

Action potentials

Answer 13

• 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

Question 14

Threshold potential

Answer 14

• typically between -50 and -55mV - an explosive depolarization occurs

Question 15

After hyper polarization

Answer 15

• the inside of the membrane briefly becomes even more negative than usual - -90mV

Question 16

Contiguous conduction

Answer 16

• 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

Question 17

Absolute refractory period

Answer 17

• 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

Question 18

Relative refractory period

Answer 18

• 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

Question 19

All-or-nothing law

Answer 19

• 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

Question 20

Myelinated fibres

Answer 20

• Neuronal axons covered at regular intervals with insulative myelin

Question 21

Myelin

Answer 21

-an insulative lipid covering that surrounds myelinated nerve fibres at regular intervals along the axon

Question 22

Obliodendrocytes

Answer 22

• myelin forming cells in the brain

Question 23

Schwann cells

Answer 23

• myelin forming cells in the PNS

Question 24

Nodes of Ranvier

Answer 24

- 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

Question 25

Saltatory conduction

Answer 25

- 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

Question 26

Innervate

Answer 26

- when a neuron terminates on a muscle or a gland

Question 27

Synapse

Answer 27

- 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

Question 28

Presynaptic neuron

Answer 28

- the neuron that conducts it's action potentials twrds a synapse

Question 29

Synaptic knob

Answer 29

- the bulbous structures on the end of an axon, each of which contains many synaptic vesicles

Question 30

Synaptic vesicles

Answer 30

- store various neurotransmitters that are released at the synapse - release is regulated by a voltage dependent calcium channels

Question 31

Neurotransmitter

Answer 31

- 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

Question 32

Post synaptic neuron

Answer 32

- the neuron that conducts it's action potentials away from the synapse

Question 33

Synaptic cleft

Answer 33

- the space between toe nerve cells In which neurotransmitters cross over

Question 34

Sub synaptic membrane

Answer 34

- the portion of the post synaptic cell membrane that lies immediately beneath a synapse and contains receptor sites for the synapse's neurotransmitter

Question 35

Excitatory synapse

Answer 35

- 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

Question 36

Inhibitory synapse

Answer 36

- 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

Question 37

Grand post synaptic potential

Answer 37

- 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

Question 38

Temporal summation

Answer 38

- the summing of several post synaptic potentials occurring very close together in time bc of successive firing of a single presynaptic neuron

Question 39

Spatial summation

Answer 39

- the summing of several post synaptic potentials arising from the simultaneous activation of several excitatory (or several inhibitory) synapses