Lecture 3

Question 1

What is a neuron?

Answer 1

A cell found in the nervous system that is specialized for the reception, conduction, and transmission of electrochemical signals

Question 2

What is Dendrite?

Answer 2

A short process (projection) emanating from a neuron cell body, that receives synaptic contacts from other neurons

Question 3

What is an Axon?

Answer 3

a long, narrow process (projection) emanating from a neuron cell body, the end of which releases chemicals into a synapsef

Question 4

What is a synapse?

Answer 4

a gap between adjacent neurons across which chemical signals are transmitted

Question 5

What is a glial cell

Answer 5

A cell found in the nervous system that helps support, protect, and nourish neurons
-type of cell that is most numerous in the nervous system

Question 6

What is myelin?

Answer 6

-a fatty insulating substance that wraps around axons
-increases the speed and efficiency of axonal conduction

Question 7

What two types of glia is myelin produced by?

Answer 7

-oligodendrocytes in the central nervous system
-schwann cells in the peripheral nervous system

Question 8

What is resting potential?

Answer 8

-a steady membrane potential of about -70 mV
-the membrane potential of a neuron at rest

Question 9

When does resting potential occur?

Answer 9

When the neuron is in a state where there are more sodium (Na+) ions outside the cell than inside, and more potassium (K+) ions inside than outside

Question 10

What is Depolarization?

Answer 10

-would be a shift in the membrane potential from -70 mV to -67 mV
-a decrease in the negativity of a neuron at resting membrane potential
-is a type of postsynaptic potential that is also known as an excitatory postsynaptic potential because it increases the likelihood that the neuron will fire

Question 11

What is hyperpolarization?

Answer 11

-would be a shift in the membrane potential from -70 mV to -72 mV
-is an increase in the negativity of a neuron at resting membrane potential
-type of postsynaptic potential that is also known as an inhibitory postsynaptic potential because it decreases the likelihood that the neuron will fire

Question 12

What is the threshold of excitation?

Answer 12

-the cutoff amount of stimulation required in order to make a neuron fire
-the level of depolarization necessary to generate as action potential, usually about -65 mV

Question 13

What is action potential?

Answer 13

-is the firing of a neuron
-a massive but momentary reversal of the membrane potential from about -70 mV about +50 mV
-an all or none response; that is, it either occurs to its full extent or does not occur at all
-actively conducted along an axon in a non decremental fashion; it does not grow weaker as it travels along the axonal membrane due to the opening of adjacent voltage-activated sodium channels

Question 14

How is an action potential unlike a postsynaptic potential?

Answer 14

It is not graded response; its magnitude is not related in any way to the intensity of the stimulus that elicited it

Question 15

When does action potential occur?

Answer 15

When there is a large influx of sodium (Na+) ions into the neuron due to the opening of voltage-activated sodium channels

Question 16

What is spatial summation?

Answer 16

-is the integration of signals that occur at different sites on the neuron’s membrane
-the adding together on the axon of all excitatory and inhibitory potentials produced at different sites on the neuron’s membrane, in order decide whether to fire or not to fire on the basis of their sum

Question 17

What is temporal summation?

Answer 17

-the integration of signals that occur at different times at the same synapse
-allows a brief sub-threshold excitatory stimulus to fire a neuron of it is administered twice in rapid succession

Question 18

When does temporal summation occur?

Answer 18

When a particular synapse is activated and then activated again before the original postsynaptic potential has completely dissipated, thus causing the effect of the second stimulus to be superimposed on the lingering postsynaptic potential produced by the first

Question 19

What is the absolute refractory period?

Answer 19

-is the time immediately after an action potential when the neuron is unable to fire again
-the brief period after an action potential during which it is impossible to elicit another action potential in the same neuron
-the hyper polarized state seen after an action potential during which potassium (K+) ions are driven out of the cell and the voltage-activated sodium channels are actively closed

Question 20

What is the relative refractory period?

Answer 20

-the time immediately after an action potential when it is difficult, but nevertheless possible, for the neuron to fire
-the period of time after the absolute refractory period during which a higher-than-normal amount of stimulation is necessary to make a neuron fire
-the hyper polarized state seen after an action potential during which voltage-activated sodium channels can possibly be opened again