ls7c week 2

At the moment that the action potential has reached its maximum height, the potential (or voltage) difference across the nerve membrane is: a. zero or equal on both sides. b. more negative inside than out. c. more positive inside than out.

c

In a typical neuron, what happens during an action potential when a voltage-gated potassium channel opens? a. potassium enters cell, cell repolarizes b. potassium leaves cell, cell depolarizes c. potassium leaves cell, cell repolarizes d. potassium enters cell, cell depolarizes

c

In vertebrates, the speed of transmission along neurons is much faster in myelinated neurons compared to unmyelinated neurons. Which answer choice is not true of transmission along myelinated neurons? a. Action potentials are generated only in the nodes of Ranvier. b. Sodium and potassium channels are concentrated at nodes of Ranvier. c. Saltatory conduction in non-myelinated neurons slows the process of transmission.

c

Inhibition of the flexor muscle during the knee-extension reflex is an example of: a. homeostasis. b. negative feedback. c. reciprocal inhibition.

c

Membrane potential is determined by the: a. concentration of cholesterol in a membrane. b. number and types of ion-channel proteins present in the plasma membrane of a cell. c. difference in concentration of ions and charged molecules on the two sides of a cell's plasma membrane. d. number and type of phospholipids present in a membrane.

c

The magnitude of the action potential is correlated with the strength of the stimulating input. True or False?

False

Referring to the figure, select whether each statement below is true or false. ((Given)) 1) Resting potential is generated mainly by the outward movement of K+ ions from inside the cell. 2) The voltage changes shown in the figure are measured just across the plasma membrane 3) The changes in voltage seen at #2 and #4 in the figure are caused by similar movements, in the same direction, of the same types of ions across the membranes. 4) The trace in the figure is following the voltage change as it moves down the axon. 5) The voltage change shown in the figure is an all-or-nothing response.

1) True 2) True 3) False 4) False 5) True

What class of membrane-transport protein is associated with triggering an action potential? a. a voltage-gated ion channel b. a ligand-gated ion channel c. a sodium-potassium symporter d. a pump protein

a

Beginning at the synapse of a neuron, place the events in neuronal signaling in the correct sequence. 1. Ion channels bind the ligand and open. 2. Na+ is pumped out of the cell, and the membrane potential is restored. 3. Acetylcholinesterase breaks down acetylcholine. 4. Na+ enters the postsynaptic cell, and the membrane potential changes. 5. Acetylcholine is released into the synapse. 6. Na+ ion channels close.

5,1,4,3,6,2

(Pt.2) Referring to the figure, select whether each statement below is true or false. ((Given)) 6) Different ion channels are responsible for generating the voltage change seen at #2 and #4 in the figure. 7) All voltage changes along the plasma membrane of an axon have the characteristic shape shown above. 8) The changes in voltage shown in the figure are due to ligand-gated ion channels opening and closing along the axon. 9) An EPSP of sufficient strength to reach threshold occurred at #1 on the figure. 10) A membrane that has no K+ channels will have a resting membrane potential that is higher than the one shown on the figure.

6) True 7) True 8) False 9) True 10) True

Place the events in the correct order. (1) opening of voltage-gated calcium channels (2) change in membrane potential of the postsynaptic neuron (3) fusion of secretory vesicles with the plasma membrane of axon terminal (4) binding of neurotransmitters to receptors on the postsynaptic neuron (5) increase in cytosolic calcium levels in the presynaptic neuron (6) arrival of action potential at the axon terminal of the presynaptic neuron

6,1,5,3,4,2

Which of the following is an example of the effector's role in maintaining homeostasis?

Increased sweating on a hot summer day

Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual?

Low levels of calcium would result in fewer signals sent between the pre- and postsynaptic cell.

Imagine you created a toxin such that when a neuron fired an action potential, the toxin would bind immediately to the sodium-potassium pump at the top of the action potential, but the sodium and potassium channels would still function. What process(es) would be affected?

Maintaining resting potential and returning to resting potential after the hyperpolarization phase of an action potential

Imagine you genetically engineered a neuron to produce voltage-gated Na+ and K+ channels that opened at the same time in response to a change in voltage. How would that change the recording shown in the figure?

No action potential would be generated

Imagine that you are talking with one of your friends about your biology course. He states that the somatic nervous system is subdivided into sympathetic and parasympathetic components, and is responsible for involuntary responses. Is this statement correct?

No, the somatic nervous system is responsible for voluntary responses, and is not subdivided into sympathetic and parasympathetic components

What effect does the nervous system have on the heart rate?

Stimulation by parasympathetic nerves causes the heart rate to slow down.

An interneuron may receive multiple stimuli from the same sensory neuron over a very short period of time. The firing rate of the receiving neuron is proportional to the number of signals received from the sensory neuron over time. Of which of the following is this an example?

Temporal summation

Dilated pupils, inhibited digestive activity, increased respiratory rate, and release of glucose from the liver are all signs of activity of:

The sympathetic division of the autonomic system

In vertebrates, the speed of transmission along a neuron can be increased by which answer choice? a. myelinating the axon b. the presence of additional voltage-gated sodium channels c. myelinating the dendrites d. the presence of additional voltage-gated potassium channels

a

Memory and learning take place in which area of the brain? a. cerebrum and hippocampus b. pons and medulla c. hypothalamus d. cerebellum

a

What causes the increase in cytosolic calcium that triggers the fusion of secretory vesicles to the membrane and the release of neurotransmitters into the synaptic cleft? a. the change in conformation of voltage-gated calcium channels in the axon terminal membrane b. the opening of ligand-gated calcium channels in the axon terminal membrane c. the hyperpolarization of the membrane at the axon terminal d. the release of calcium from intracellular calcium stores

a

Which answer choice occurs when a neuron is depolarized? a. Sodium ions enter the neuron through voltage-gated sodium channels. b. Calcium ions enter the cell through voltage-gated calcium channels. c. Sodium ions diffuse along the outside of the neuron, bringing nearby regions to threshold. d. Potassium ions enter the neuron through voltage-gated potassium channels.

a

Which function is NOT a role of an interneuron? a. stimulating a muscle to contract b. maintaining homeostasis c. conveying information within the internal environment of an animal d. relaying information from sensory to motor neurons

a

Which of the scenarios will most likely trigger an action potential? Select all that apply. a. multiple excitatory postsynaptic potentials (EPSPs) arriving close in time at a single synapse (temporal summation) on the postsynaptic cell b. single excitatory postsynaptic potentials (EPSPs) arriving simultaneously at several different synapses (spatial summation) on the postsynaptic cell c. an excitatory postsynaptic potential (EPSP) and an inhibitory postsynaptic potential (IPSP) arriving simultaneously on the postsynaptic cell (cancellation)

a, b

Which of the statements is true of chemical synapses? Select all that apply. a. Once released from postsynaptic membrane receptors, neurotransmitter molecules may be actively returned to the presynaptic cell. b. They are more common than electrical synapses. c. Ligands must also bind to ligand-gated ion channels on the presynaptic membrane of the synapse.

a,b

A stroke occurs when blood flow to a region of the brain is interrupted, damaging the cells in that region. What symptoms might you see if a person suffered a stroke in their cerebellum? a. loss of sensory perception b. loss of balance and coordination c. visual impairment d. difficulty speaking

b

Imagine that a student studies all night for an exam the next day. The student remembers (almost) everything for her test, but within a week, she forgets most of what she studied. Why? a. The student has not studied the material she was tested on repeatedly. b. All of these choices are correct. c. New neural circuits were not formed (or strengthened) in the student's brain. d. The student's short-term memories regarding the test material were not successfully transformed into long-term memories.

b

Predict what would happen to a neuron's resting membrane potential if the number of sodium ion channels increased. a. The membrane potential would become slightly more negative. b. The membrane potential would become more positive. c. The more sodium channels are present, the more sodium can exit the cell. This would result in a more positive membrane potential.The membrane potential would remain the same due to the activity of the sodium-potassium pump. d. The membrane potential would become more negative.

b

The interior of a neuron is more negative than the outside due to the presence in the interior of: a. potassium and chloride ions. b. proteins and chloride ions. c. hydroxyl (OH-) groups. d. sodium and chloride ions.

b

The phrase saltatory propagation refers to the: a. tendency of an action potential to move in one direction. b. ability of an action potential to "jump" from one node of Ranvier to the next. c. All of these choices are correct. d. role of ions such as sodium and potassium in producing the action potential.

b

The release of neurotransmitter from the presynaptic cell is an example of: a. endocytosis. b. exocytosis. c. phagocytosis.

b

What part of a cell's cytoplasm is responsible for the diversity of nerve cell shape? a. the nucleus b. the cytoskeleton c. the endomembrane system

b

Which answer choice determines whether or not an action potential is triggered in the postsynaptic neuron? a. the magnitude of the hyperpolarizing inhibitory postsynaptic potential (IPSP) b. the overall net change in membrane potential caused by the combined EPSPs and IPSPs c. the magnitude of the depolarizing excitatory postsynaptic potentials (EPSPs)

b

Which set of terms belong together? a. voluntary, somatic, sympathetic b. involuntary, autonomic, sympathetic c. voluntary, autonomic, parasympathetic d. involuntary, somatic, parasympathetic

b

Certain medications can cause potassium levels in the body to decrease. Which symptom would be consistent with a low concentration of potassium? a. irregular heartbeat b. All of these choices are correct. c. muscle weakness d. fatigue

b, Potassium concentrations need to be at a certain concentration inside the cell in order to achieve appropriate membrane potentials. The resting membrane potential is lower (more negative) and requires increased stimuli to reach threshold. With normal levels of stimuli, the cell does not reach threshold, and action potentials become less frequent. Fewer action potentials result in feelings of fatigue and muscle weakness because of decreased stimulation caused by hyperpolarized cells.

Which of the statements are true about the resting membrane potential? Select all that apply. a. It results from voltage-gated sodium channels remaining open for long periods of time. b. It results from K+ ions diffusing out of the cell. c. It results from the sodium-potassium pump moving more Na+ ions out of the cell than K+ ions into the cell.

b, c

Action potentials typically move in one direction along the neuron away from the cell body. This is due to which answer choice? a. the temporary inactivation of sodium and potassium channels following the action potential spike b. the movement of sodium ions out of the cell through voltage-gated potassium channels c. the temporary hyperpolarization of the axon membrane following the action potential spike d. the myelination of the axon membrane

c

Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual? a. Low levels of calcium would not have any effect on synaptic transmission. b. Low levels of calcium would cause sustained depolarization of the presynaptic cell. c. Low levels of calcium would result in fewer signals sent between the presynaptic and postsynaptic cell.

c

Under normal (resting) cellular conditions, the _________ concentration is greater inside the cell, and the plasma membrane is most permeable to ______________. a. sodium; sodium b. potassium; sodium c. potassium; potassium d. sodium; potassium

c

Which portion of the forebrain regulates the endocrine system and body temperature? a. cerebrum b. limbic system c. hypothalamus d. thalamus

c

Why does an action potential travel in one direction down an axon? a. because it needs to reach the synapse to trigger release of neurotransmitters b. because the diffusion of charge can only occur in one direction c. because voltage-gated sodium ion channels cannot immediately reopen d. Once the membrane has been depolarized, the membrane must return to resting potential before voltage-gated sodium ion channels can experience the next depolarization. d. because voltage-gated potassium ion channels remain open longer

c

_________ concentration is always higher outside the cell. During the peak of the action potential, the plasma membrane is becoming more permeable to _________. a. Potassium; potassium b. Sodium; sodium c. Sodium; potassium d. Potassium; sodium

c

A neuron's ability to generate action potentials depends: a. on the immediate opening of voltage-gated potassium channels once threshold has been reached, allowing potassium to enter the axon. b. on the axon reaching threshold and the opening of voltage-gated sodium channels, allowing sodium to leave the axon. c. on the immediate opening of voltage-gated potassium channels once threshold has been reached, allowing potassium to leave the axon. d. on the axon reaching threshold and the opening of voltage-gated sodium channels, allowing sodium to enter the axon.

d

Body functions such as heart rate, blood flow, and digestion are controlled by the: a. somatic nervous system. b. voluntary nervous system. c. automatic nervous system. d. autonomic nervous system.

d

Temporal summation is a response to the: a. amount of neurotransmitter released from a presynaptic cell. b. density of ligand-gated channels on the postsynaptic cell. c. location of synapses over the surface of a postsynaptic neuron. d. frequency of stimulation of a postsynaptic cell.

d

Transmission of impulses along a neuron in the vertebrate nervous system ordinarily occurs in only one direction because, following passage of an action potential, the neuron is temporarily in a refractory period or hyperpolarized. This is caused by which answer choice? a. the movement of sodium ions out of the axon b. the movement of potassium ions into the axon c. the movement of sodium ions into the axon d. the movement of potassium ions out of the axon

d

When an action potential reaches the axon terminal: a. sodium ions are released from the axon terminal, enter the cell body of the postsynaptic neuron through its sodium channels, and may initiate an action potential in that neuron. b. neurotransmitter molecules are released from the axon terminal, bind to and open the potassium channels on the cell body of the next neuron, and may initiate an action potential in that neuron. c. calcium ions are released from the axon terminal, bind to and open the sodium channels on the cell body of the next neuron, and may initiate an action potential in that neuron. d. neurotransmitter molecules are released from the axon terminal and bind to receptors on the postsynaptic neuron, causing either an inhibitory hyperpolarization or an excitatory depolarization.

d

Which answer choice could be inhibited by greatly decreasing extracellular calcium? a. the arrival of the action potential at the presynaptic axon terminal b. the production of neurotransmitter by the presynaptic neuron c. the opening of voltage-gated calcium channels on the presynaptic axon terminal d. the fusion of secretory vesicles with the presynaptic plasma membrane

d

Which brain region controls drives, instincts, and emotion? a. cerebrum b. cerebellum c. thalamus d. limbic system

d

Which brain region is associated with language in humans? a. parietal lobe b. occipital lobe c. frontal lobe d. temporal lobe

d

Which region of the brain is larger in humans and primates than in other vertebrates? a. forebrain b. cerebellum c. midbrain d. cerebral cortex

d

When an environmental stimulus is received, the signal is usually transmitted through three types of nerve cells. In which order is the signal transmitted through these cells?

sensory, interneurons, motor neurons

All neurons have either a sensory or a motor function. true/false

false

Inhibitory postsynaptic potentials (IPSPs) are associated with membrane depolarization, whereas excitatory postsynaptic potentials (EPSPs) are associated with hyperpolarization. true/false

false

Ganglia were the evolutionary precursor to the centralized concentration of neurons that we now call a brain. true / false

true