Chapter 11 Mastering A&P

In addition to diffusion, what are two other mechanisms that terminate neurotransmitter activity?

reuptake and degradation

Which of the following is NOT a type of circuit?

pre-synaptic circuits

Which of the following statements most accurately describes the effects caused by binding of the neurotransmitter (green dots) to the structure labeled C?

The membrane potential of the postsynaptic membrane changes.

Which of the following is not characteristic of neurons?

They are mitotic.

What type of channel on the postsynaptic membrane binds neurotransmitter?

a chemically gated channel

Which of the following is a factor that determines the rate of impulse propagation, or conduction velocity, along an axon?

degree of myelination of the axon

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in the receptive region of a neuron?

excitatory postsynaptic potential

Neurotransmitter is released from presynaptic neurons through what mechanism?

exocytosis

Strong stimuli cause the amplitude of action potentials generated to increase

false

What does the central nervous system use to determine the strength of a stimulus

frequency of action potentials

Collections of nerve cell bodies in the peripheral nervous system are called ________.

ganglia

Which of the following describes the excitatory postsynaptic potential?

short distance depolarization

The generation of an action potential in a neuron requires the presence what type of membrane channels?

voltage-gated channels

In which area of the neuron is an action potential initially generated

C at the axon hillock

Which of the following membrane regions would have significant numbers of voltage-gated ion channels?

C and D Voltage-gated Na+ and K+ channels allow for the triggering of an action potential at the axon hillock (C) and its propagation down the axon (D).

What is the role of calcium in synaptic activity?

Calcium influx into the synaptic terminal causes vesicle fusion.

Which of the following is not a function of the autonomic nervous system?

D) innervation of skeletal muscle

The all-or-none phenomenon as applied to nerve conduction states that the whole nerve cell must be stimulated for conduction to take place.

False

The concentration of ___ is higher inside than outside the cell

K+

The membrane is more permeable to ___

K+

The resting membrane potential is maintained by Na+-K+ pumps that actively transport ___ into the cell and ___ out of the cell

K+; Na+

The concentration of ___ is higher outside the cell than inside the cell

Na+

What is the direct role of neurotransmitter at a chemical synapse?

Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane.

A resting neuron is an unstimulated neuron that is not presently generating an action potential. The resting membrane potential is the separation of the relative positive and negative charges across the membrane of a cell at rest.

Outside + Inside -

Events that occur during synaptic activity are listed here,

(c) Action potential arrives at the axon terminal (a) Voltage-gated calcium channels open (e) The neurotransmitter released into the synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft

Synaptic response to an action potential

1. An action potential arrives at the synaptic terminal. 2. Calcium channels open, and calcium ions enter the synaptic terminal. 3. Vesicles containing neurotransmitter fuse with the plasma membrane of the sending neuron. 4. Neurotransmitter molecules diffuse across the synaptic cleft. 5. The neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron causing ion channels there to open.

The propagation of an action potential (AP) in an unmyelinated axon is called continuous propagation. This activity will test your understanding of the sequence of events that occur during continuous propagation.

1. Local current flows to axon segment 2. Axon segment depolarized to threshold 3. Voltage-gated Na+ channels open 4. Influx of Na+ 5. AP regenerated in adjacent axon segment

Action potentials (nerve impulses) are changes in the membrane potential that, once started, will affect the entire excitable membrane. The first action potential is usually generated at the initial segment of the neuron's axon. This activity will test your understanding of the sequence of events that occur at the membrane of the initial segment of the axon during generation of an action potential.

1..Threshold stimulus Na+ channels open 2..Na+ influx Depolarization 3.Na+ channels close 4..K+ efflux Repolarization 5.Hyperpolarization K+ channels close

Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated ion channels. Why does injection of a local anesthetic into a finger still cause a loss of the sensation of touch from the finger?

Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels.

What structural classification describes this neuron?

multipolar The neuron shown has a many processes (axon and dendrites) that emerge from the cell body. Such neurons typically function as motor neurons or interneurons.

Saltatory conduction is made possible by ________.

myelin sheath

Saltatory propagation occurs in _________ axons, in which action potentials _________.

myelinated; move from one node of Ranvier to another

Which of the following stimuli caused the reaction in the graph on the left?

opening of gated Na+ channels

Which of the following is expected to occur first if the membrane potential decrease shown in the graph on the left were to reach the threshold value indicated at ~ -55 mV?

opening of voltage-gated Na+ channels

As you start working out, you notice that your heart rate and breathing rate start to increase. Which division of your nervous system is generating this response? Be as specific as possible.

the sympathetic division of the autonomic nervous system

A postsynaptic potential is a graded potential that is the result of a neurotransmitter released into the synapse between two neurons

true

During depolarization, the inside of the neuron's membrane becomes less negative

true