Ch 12: Biological Processes in the Brain

Question 1

Neurons with one dendrite are termed _______; those with many dendrites are __________.

Answer 1

bipolar

multipolar

Question 2

What is the difference between a neuron and a nerve?

Answer 2

A neuron is a single cell. A nerve is a large bundle of many different axons from different neurons.

Question 3

The resting membrane potential is approximately ___ __, with interior of the cell __________ charged with respect to the exterior of the cell.

Answer 3

-70 mV

negatively

Question 4

What two primary membrane proteins are required to establish the resting membrane potential?

Answer 4

the Na+/K+ ATPase pump and the potassium leak channels

Question 5

The Na+/K+ ATPase pumps _ sodium ions out of the cell for every _ potassium ions into the cell with the __________ of one ATP molecule.

Answer 5

3
2
hydrolysis

Question 6

Leak channels are channels that are open all the time.
There are relatively few sodium leak channels in the cell membrane; the ratio of K+ leak channels to Na+ leak channels is about _____.

Answer 6

100:1

Question 7

The threshold potential is approximately _____.

Answer 7

-50 mV

Question 8

In an action potential, which of these events happens first?

a. ) voltage-gated K+ channels close
b. ) voltage-gated Na+ channels open
c. ) voltage-gated Na+ channels inactivate and voltage-gated K+ channels open

Answer 8

b.) voltage-gated Na+ channels open

Question 9

Repolarization happens for a number of reasons:

1. ) voltage-gated Na+ channels inactivate very quickly after they open, shutting off the flow of sodium into the cell. These channels remain ___________ until the membrane potential nears resting values again.
2. ) voltage-gated potassium channels open ____ ______ than the voltage-gated sodium channels and stay open longer. Voltage-gated K+ channels open in response to membrane DEpolarization. As K+ leaves, it actually overshoots the resting potential by about 20 mV (to -90 mV). At that point, the voltage-gated K+ channels close.

Answer 9

inactivated

more slowly

Question 10

In the PNS, the myelin sheath is created by _______ cells. In the CNS, this job is done by ___________.

Answer 10

Schwann
oligodendrocytes

p. 348

Question 11

The rapid jumping conduction in myelinated axons is called _________ __________.

Answer 11

saltatory conduction

p. 348

Question 12

The equilibrium potential for sodium is approximately _____. What does this mean?

Answer 12

+50 mV (+65mV according to Sketchy)

Na+ ions are driven into the cell by their concentration gradient. But if the interior of the cell is too positive, the positively-charged ions are repelled. In other words, the electrical gradient would drive sodium out. These forces, the chemical gradient driving sodium in, and the electrical gradient driving sodium out balance each other at about +50mV.

Question 13

In contrast, K+ has an equilibrium potential of _____.

Answer 13

-90 mV

Question 14

The equilibrium potential for any ion can be predicted by the ______ equation.

Answer 14

Nernst equation

E ion = (RT/zF) {ln [X outside]/[X inside]}

Question 15

During the ________ __________ ______, a neuron will not fire another action potential no matter how strong a membrane depolarization is induced.

Answer 15

absolute refractory period

p. 350

Question 16

Electrical synapses occur when the cytoplasms of two cells are joined by ___ _________.

Answer 16

gap junctions

p. 351
* Note: Electrical synapses are not common in the nervous system although they are quite important in propagating action potentials in smooth muscle and cardiac muscle.

Question 17

There are many steps involved in the transmission of a signal across a chemical synapse in the nervous system. The first 3 of 8 are here:

1. ) an action potential reaches the end of an axon, the ________ ____.
2. ) depolarization of the presynaptic membrane opens voltage-gated calcium channels.
3. ) calcium influx into the presynaptic cell causes __________ of neurotransmitter stored in secretory vesicles.

Answer 17

synaptic knob

exocytosis

Question 18

There are many steps involved in the transmission of a signal across a chemical synapse in the nervous system. Steps 4 and 5 of 8 are here:

4. ) Neurotransmitter molecules diffuse across the narrow _______ _____ (small space between cells).
5. ) Neurotransmitter binds to receptor proteins in the postsynaptic membrane. These receptors are ______-_____ ion channels.

Answer 18

synaptic cleft
ligand-gated

p. 351

Question 19

There are many steps involved in the transmission of a signal across a chemical synapse in the nervous system. Steps 6-8 of 8 are here:

6. ) the opening of these ion channels in the postsynaptic cell alters the ________ __________.
7. ) If the membrane depolarization of the postsynaptic cell reaches the threshold of voltage-gated sodium channels, an action potential is initiated.
8. ) Neurotransmitter in the synaptic cleft is ________ and/or removed to terminate the signal.

Answer 19

membrane polarization
degraded

p. 351

Question 20

If a neurotransmitter opens a channel that depolarizes the postsynaptic membrane, then that neurotransmitter is termed __________.
Neurotransmitters that induce hyperpolarization of the postsynaptic membrane are called __________.

Note, however, that it is ultimately not the neurotransmitter that determines the effect on the postsynaptic cell, it is the RECEPTOR for that neurotransmitter and its associated ion channel. The same neurotransmitter can be excitatory in some cases and inhibitory in others.

Answer 20

excitatory
inhibitory

p. 352

Question 21

True or false, postsynaptic neurons may have many different receptors, allowing them to respond to many different neurotransmitters.

Answer 21

TRUE

p. 352

Question 22

One form of summation is ________ summation in which a SINGLE presynaptic neuron fires action potentials so rapidly that the EPSPs or IPSPs pile up on top of each other.

Answer 22

temporal

p. 352

Question 23

The other form of summation is ________ summation, in which the EPSPs and IPSPs from ALL of the synapses on the postsynaptic membrane are summed at a given moment in time. If the total sum causes the postsynaptic membrane to reach the threshold voltage, an action potential will be fired.

Answer 23

spatial

p. 352

Question 24

Receiving information is the sensory function of the nervous system carried out by the ______ nervous system. Processing the information is the integrative function carried out by the ______ nervous system, and acting on it is the motor function also carried out by the ______ nervous system.

Answer 24

peripheral
central
peripheral

p. 353

Question 25

A muscle stretch reflex involving only two neurons and one synapse is known as….

Answer 25

….a monosynaptic reflex arc.

p. 353

Question 26

The terms afferent and efferent pertain to function of the _______ and _______ branches of the peripheral nervous system.

Answer 26

somatic and autonomic

p. 355