Ch. 8 Neurons

Somatic motor neurons control _ , and _ neuron control smooth and cardiac muscles, glands, and some adipose tissue.

Skeletal muscles, autonomic

Axon

to carry electrical impulses that are the means of communication within the brain and between the brain and the rest of the body.

Dendrite

to receive information from other neurons, called pre-synaptic neurons, or from the environment.

Afferent

conducting or conducted inward toward something (for nerves, the central nervous system; for blood vessels, the organ supplied).

Efferent

conducted or conducting outward or away from something (for nerves, the central nervous system; for blood vessels, the organ supplied).

Trigger zone

is the area where action potentials are generated, and is located at the junction of the axon hillock and the axon's initial segment.

Name the two primary cell types found in the nervous system.

Neuron and glial cells

1. Axonal transport refers to the

   A. release of neurotransmitters into the synaptic cleft.

   B. Cuse of microtubules to send secretions from the cell body to the axon terminal.

   
   C.movement of organelles and cytoplasm up and down the axon.

   D. movement of the axon terminal to synapse with a new postsyn-aptic cell.

   E. none of these.

C

All or none

A) action potential

B) graded potential

A

Can be summed

A) action potential

B) graded potential

B

Amplitude decreases with distance

A) action potential

B) graded potential

B

Membrane potential changes from -70mV to -50 mV

Depolarize

Membrane potential changes from -70 mV to -90 mV

Hyperpolarize

Membrane potential changes from +20 mV to -60 mV

Repolarize

Membrane potential changes from -80 mV to -70 mV

Depolarize

When you open a ion channel the ion will go

Where it’s more negative

Exhibits a refractory period

A) action potential

B) graded potential

A

Amplitude depends on strength of stimulus

A) action potential

B) graded potential

B

Has no threshold

A) action potential

B) graded potential

B

place in order

1. Efferent neuron reaches threshold and fires an action potential.

2. Afferent neuron reaches threshold and fires an action potential.

3. Effector organ responds by performing output.

4. Integrating center reaches decision about response.

5. Sensory organ detects change in the environment.

5-2-4-1-3

Astrocytes

Form support for central nervous system

Help form blood brain barrier

Secrete neurotrophic factors

May also be a source of neural stem cells

Take up K+ neurotransmitters

Ependymal cells

Create barriers between compartments

Source of neural stem cells

Microglia

Act as scavengers

Oligodendrocytes

Form myelin sheath

Satellite cells

are stem cells that are responsible for the growth, repair, and regeneration of skeletal muscle

Schwann cells

form the myelin sheath on axons outside the brain

T/F An action potential is a reversal of the Nat and K* concentrations inside and outside the neuron.

False, during an action potential, there is a rapid influx of Na^+ ions into the neuron followed by an efflux of K^+ ions out of the neuron, which changes the membrane potential. However, the overall concentrations of Na^+ and K^+ inside and outside the neuron do not reverse.

T/F An action potential is the same size and shape at the beginning and end of the axon.

True

T-F At the equilibrium potential for K* there is a net flow of K+ ions outward across the neuronal membrane.

False, at the Ek+ there is no net movement of K+ ions across the membrane.

The resting cell membrane is more permeable to __ than to __. Although __ contribute little to the resting membrane potential, they play a key role in generating electrical signals in excitable tissues.

K+, Na+, Na+

T/F An action potential is initiated by inhibitory postsynaptic graded potentials.

False, an action potential is typically initiated by excitatory postsynaptic graded potentials, not inhibitory ones. Excitatory postsynaptic potentials (EPSPs) depolarize the neuron, making it more likely to reach the threshold for firing an action potential, whereas inhibitory postsynaptic potentials (IPSPs) hyperpolarize the neuron, making it less likely to fire.

T/F An action potential is transmitted to the distal end of a neuron and causes release of neurotransmitter.

True

In your work for a pharmaceutical company, you have just created a neurotransmitter that opens K+ channels on a neuron's cell membrane. A neuron that expresses receptors for this neurotransmitter will

1. be more likely to fire an action potential

2. be less likely to fire an action potential

3. The drug will have no effect on the likelihood of action potential firing in the neuron.

2. be less likely to fire an action potential

What causes the (repolarization) falling phase of the action potential?

1. Nat being pumped out of the cell by the Na*-K+-ATPase pump.

2. K+ being pumped into the cell by the Na*-K*-A TPase pump.

3. Nat entering the cell through leak channels, trying to reach its equilibrium potential.

4. K+ entering the cell through leak channels, trying to reach its equilibrium potential

5. none of the above

right

5. None of the above

During the (depolarization) rising phase of the action potential,

1. voltage-gated potassium channels are open

2. there is a decrease in the sodium permeability

3. sodium moves down both a concentration and electrical gradient (i.e. an electrochemical gradient).

4. the cell's membrane potential moves toward the equilibrium potential for potassium (Ek+).

3. Sodium moves down both a concentration and electrical gradient

Communication in the nervous system involves

Chemical and Electrical signals

The conduction of an action potential along an axon:

1. is faster for a large amplitude EPSP than a small amplitude EPSP.

2. is faster in unmyelinated axons than in myelinated axons.

3. decreases in amplitude as it is propagated along the axon

4. all of the above are true

5. none of the above is true

5. None of the above

Release of neurotransmitter from an axon terminal requires:

1. Depolarization of the axon terminal

2. Cat

3. Hyperpolarization of the axon terminal

4. A and B

5. Band C

4. A and B