Lesson 4- Nerves

Question 1

What is the functional cellular unit of the human nervous system?

Answer 1

Neuron

Question 2

What is a neuron?

Answer 2

A cell that transmits nerve impulses

Question 3

What do neurons or nerve cells contain?

Answer 3

A nucleus and a cell body or soma

Question 4

What does the soma contain?

Answer 4

Nucleus and other cell organelles

Question 5

How does the cell body receive impulses?

Answer 5

Dendrites

Question 6

What are Dendrites?

Answer 6

afferent fibers-The dendrite is typically a short, abundantly branched, slender process (extension) of the cell body that receives stimuli.

Question 7

How does the soma send out impulses?

Answer 7

via its axon (efferent fibers)

Question 8

What is an axon?

Answer 8

The axon is typically a long, slender process of the cell body that sends nerve impulses.

Question 9

What is a synapse?

Answer 9

The synapse or synaptic cleft is a gap that separates the neuron from a muscle cell or another neuron.

Question 10

How do nerve impulses travel?

Answer 10

From axon to dendrite, by way of a synapse.

Question 11

What is the chemical that transmits impulses from one nerve to another?

Answer 11

acetylcholine.

Question 12

What is myelin?

Answer 12

A fatty sheath that covers many neurons

Question 13

What is resting potential?

Answer 13

The resting potential describes the unstimulated, polarized state of a neuron (@ -70 millivolts).

Question 14

What is graded potential?

Answer 14

a change in the resting potential of the plasma membrane in the response to a stimulus.

Question 15

What can cause a graded potential?

Answer 15

Stimuli that could cause a graded potential include heat, light, and neurotransmitters. A graded potential is a local event that does not travel far from its origin.

Question 16

What is an action potential?

Answer 16

Capable of traveling long distances.If the stimulus is strong enough to exceed the threshold then complete depolarization will occur (from -70 to about +30 millivolts). When the stimulus fails to produce depolarization that exceeds the threshold value no action potential will occur.

Question 17

What depolarizes the membrane?

Answer 17

Action potential (electrical impulse) - which makes it permeable to Calcium ions CA++

Question 18

Ions involved in nerve impulse conduction along the length of nerve fibers

Answer 18

Na+ and K+

Question 19

Period after a response during which the cell becomes repolarized

Answer 19

Refractory period

Question 20

What is the synaptic vesicle for?

Answer 20

to release a transmitter substance, which crosses the synaptic cleft, and is collected by the receptor molecules on the postsynaptic cell.

Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell

Question 21

What is inhibitory postsynaptic potential (IPSP)?

Answer 21

The change in membrane potential where If the transmitter substance is inhibitory, it increases the permeability of the postsynaptic cell to potassium ions (K+) and/or chloride ions (CL-), thus stabilizing the membrane potential.

Question 22

What is excitatory postsynaptic potential (EPSP)?

Answer 22

The process of depolarization in which the transmitter substance is excitatory. It increases the permeability of the postsynaptic membrane to Na+ and K+. The influx of sodium into the cell depolarizes (becomes more positive) the cell further.

Question 23

What does depolarization mean?

Answer 23

making it less negative

Question 24

What is a local potential?

Answer 24

EPSP and IPSP

Question 25

What is needed to set up an action potential?

Answer 25

EPSP

Question 26

Transmission of an impulse across a synapse, from presynaptic cell to postsynaptic cell may be in what two forms?

Answer 26

electrical or chemical

Question 27

What happens during an electrical synapse?

Answer 27

the action potential travels along the membranes of gap junctions, small tubes of cytoplasm, that allow the transfer of ions between adjacent cells.

Question 28

What happens during a chemical synapse?

Answer 28

The diffusion of chemicals (neurotransmitters) cause an action potential to be transferred across the synapse

Question 29

What is a neurotransmitter?

Answer 29

chemical substances made by the neuron specifically to transmit a message.

Question 30

Common neurotransmitters?

Answer 30

acetylcholine, epinephrine, norepinephrine, dopamine, serotonin, and gamma aminobutyric acid (GABA).

Question 31

is commonly secreted at neuromuscular junctions, the gaps between motor neurons and muscle cells, where it stimulates muscles to contract by opening positive ion channels. At other kinds of junctions, it typically produces an IPSP.

Answer 31

Acetylcholine

Question 32

are derived from amino acids and are secreted mostly between neurons of the central nervous system (CNS).

Answer 32

Epinephrine, norepinephrine, dopamine, and serotonin

Question 33

usually an inhibitory neurotransmitter (opening gated Cl- channels) among neurons in the brain.

Answer 33

Gamma aminobutyric acid (GABA)