Unit 2: Physiology Mastering Ch 7, 8, 9, 10

Which membrane potential opens a sufficient number of the voltage-gated Na+Na+ channels to cause a significant change in the membrane potential (making it much less negative).

-60 mV (The membrane potential at which sufficient voltage-gated Na+Na+ channels open is -60 mVmV.)

What is the resting membrane potential of the neuron used in the experiment?

-80 mV (The resting membrane potential for this neuron is the line, or portion of the line, at which there is no observable activity. For this particular neuron, we see this occurs right at -80 mVmV.)

Based on the data in figures 1 and 2, if one synaptic vesicle of acetylcholine was released at the neuromuscular junction, what change in membrane potential would you expect to observe in the muscle cell?

0.4 mV

Examine Figure 1. Based on your observations, what would be the minimum change in membrane potential that occurred spontaneously?

0.4 mV

Based on Figure 1, what was the maximum change in membrane potential that occurred spontaneously?

1.2 mV

If every ligand-gated Na+ channel on a neuronal soma depolarized the cell by 2mV, how many channels would you need to activate to reach a threshold value of exactly -50mV? (Assume a typical resting membrane potential.)

10 (If 10 channels were activated and they each resulted in a 2mV depolarization, this would depolarize the cell by 20 mV ( -70mV + 20 mV = -50mV).)

The treatment for phantom limb pain has a __________ chance of long-term relief.

25%

When naturally stimulated by motor neurons, skeletal muscle cells respond with a depolarization called an end plate potential. Unlike neuron-to-neuron synapses, end plate potentials are always of sufficient magnitude to induce an action potential in the skeletal muscle cell membrane. What is the minimum number of synaptic vesicles that need to be released to reach threshold value?

38 (The studies by Katz and his colleagues showed that neurotransmitter was released in quanta. Other studies demonstrated that these quanta word equivalent to synaptic vesicle content. In the case of the neuromuscular junction, each synaptic vesicle contains approximately 10,000 acetylcholine molecules.)

When one synaptic vesicle of acetylcholine is released at the neuromuscular junction, the muscle cell is depolarized 0.4 mV. What change in membrane potential would you expect to see happen in a muscle cell if 10 synaptic vesicles containing acetylcholine is released from the motor neuron?

40 mV

Na+ permeability

Although it plays a role, it is not a primary determinant of the resting membrane potential

How is an action potential propagated along an axon?

An influx of sodium ions from the current action potential depolarizes the adjacent area. (Yes, the influx of sodium ions depolarizes adjacent areas, causing the membrane to reach threshold and cause an action potential. Thus, the action potential is regenerated at each new area.)

Which part of a neuron would be most impacted by novocaine?

Axon (The axon contains most of the voltage-gated Na+ channels, which are blocked by novocaine.)

Membrane potential - more negative

Double the number of K+K+ leak channels, Decrease the concentration of Na+Na+ outside the cell by half

Membrane potential - largely uncharged

Double the size of the cell, without adding channels, Double the number of closed channels for K+

The stroke in this example occurred in what lobe of the brain?

Frontal (The stroke occurred in the frontal lobe just anterior to the central sulcus and lateral.)

What type of stroke occurred in this individual?

Hemorrhagic

The common test for color blindness uses the __________.

Ishihara chart

If a chord had notes with frequencies of 100, 1,000, and 6,000 Hz, what would happen to the basilar membrane?

It would vibrate at multiple positions, with peaks at A, B, and C.

This image shows a stroke has occurred on what side of the brain?

Left

Which of the following is most likely a symptom that would be associated with this stroke?

Loss of facial muscle control

The concentrations of which two ions are highest outside the cell?

Na+ and Cl−

Three presynaptic neurons (A, B, and C) generate excitatory potentials on a single post-synaptic neuron (X). Neurons A, B, and C each cause a 5mV depolarization at the axon hillock. Based on this information, which of the following is true?

Neurons A, B, and C release neurotransmitters that open ligand-gated Na+ channels on Neuron X. (Activation of ligand-gated Na+ channels would result in depolarizing, excitatory potentials on Neuron X.)

Let's consider a scenario in which the resting membrane potential changes from −−70 mVmV to +70 mVmV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+Na+. The electrical gradient for Na+Na+ would tend to move Na+Na+ __________ while the chemical gradient for Na+Na+ would tend to move Na+Na+ __________.

Out; in (If the inside of the cell is positively charged compared to the outside, the electrical gradient will favor movement of positively charged sodium ions out of the cell.)

__________ is a form of phantom sensations in which the person perceives some form of discomfort (itching, burning, aching, tingling) originating from a missing limb.

Phantom limb pain

__________ refers to a condition in which a person perceives some form of sensation from a missing limb, and thinks it still connected to the body.

Phantom sensations

The three types of cones are termed the __________, because of the length of wavelengths of light they can absorb.

S (short), M (medium) and L (long)

Blue light is absorbed by the __________ cones and green light is absorbed by the __________ cones; red light is absorbed by the __________ cones.

S; M; L

How would this result in a listener hearing a chord?

Sensory neurons at each position in the basilar membrane transmit action potentials to the brain, where the perception of a chord is generated. (The basilar membrane would vibrate at multiple positions, with peaks at A, B, and C. Sensory neurons at each position along the basilar membrane would provide output in the form of action potentials that travel along distinct axons in the auditory nerve. When this information reaches the brain, the perception of the chord is generated.)

In this experiment, which stimulus causes the membrane potential to reach the threshold value?

Stimulus 3 (Threshold is achieved when a neuron is stimulated strongly enough to trigger an action potential.)

Why does the action potential only move away from the cell body?

The areas that have had the action potential are refractory to a new action potential. (Yes, sodium channels are inactivated in the area that just had the action potential.)

Membrane potential of -90 mV

The point at which there is no net movement of K+ into or out of the cell

K+ permeability

The primary determinant of the resting membrane potential

Membrane potential of -70 mV

The resting membrane potential of the cell

Membrane potential - more positive

Triple the number of Na+Na+ leak channels, Double the concentration of K+K+ outside the cell

The genes that produce the red and green photopigments are located on the __________ and are __________.

X chromosome; recessive

The main cause for a sudden vascular occlusion is __________.

a blood clot

Multiple sclerosis, Alzheimer's disease, and Parkinson's disease are __________ disorders.

a few of the neurodegenerative

It appears that the attack on the World Trade Center caused __________ of post-traumatic disorder diagnosis than that of the Vietnam War and Gulf War.

a higher percentage

The velocity of the action potential is fastest in which of the following axons?

a small myelinated axon (Yes, the myelination acts as insulation and the action potential is generated only at the nodes of Ranvier. Propagation along myelinated axons is known as saltatory conduction.)

If a brain aneurysm is found in a patient, generally __________ is the only and best treatment.

a surgery

The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

acetylcholine (Yes, acetylcholine is broken down by acetylcholinesterase before being returned to the presynaptic neuron's axon terminal.)

In order to counteract the loss of cholinergic neurons in the brain, the amount of available acetylcholine is increased by using a(n):

acetylcholinesterase inhibitor

In this condition, it is thought that the homeostatic coordination between the hypothalamus, pituitary, and __________ is __________ functioning.

adrenal gland; not properly

Choose the option that correctly finishes the sentence. Ligand-gated ion channels, such as the nicotinic cholinergic receptor activated by acetycholine, __________.

allow the influx of sodium ions, which facilitates fast responses at synapses

If a stroke is hemorrhagic, then __________ should not be given, since it will worsen the condition.

an anticoagulant

A person at risk for forming blood clots in the brain may be placed on a(n) __________ like aspirin.

anticoagulant

Post-traumatic stress disorder is considered to be a(n) __________.

anxiety disorder

Researchers report that during normal brain development, portions of certain sensory pathways undergo __________, in order to lose their connectivity to the wrong sensory pathway.

apoptosis

A post-traumatic stress disorder patient will attempt to __________ .

avoid stressful situations

Which of the following synapses function as modulatory synapses?

axoaxonic

Researchers report that individuals with __________ may develop synesthesia.

brain injuries or epilepsy

A stroke, or ___________, is the __________ leading cause of death in the United States.

cerebrovascular accident (CVA); third

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

chemically gated; postsynaptic (Yes, the neurotransmitter is a chemical released from the presynaptic membrane, so it would open chemically gated channels on the postsynaptic membrane.)

One form of synesthesia, in which a word is heard, and a color is seen is termed __________ synesthesia.

colored-hearing

The __________ are responsible for seeing colors.

cones

The most common reason for color blindness is improper development of one of the __________, however, there are other reasons.

cones

What is the name of the process through which one neuron receives communication from several other "upstream" neurons?

convergence

Two hormones produced from the adrenal gland increase in secretion during a stressful situation; they are __________ and __________.

cortisol; epinephrine

__________ is known as a __________, because it mobilizes glucose and other biomolecules to help control of stress.

cortisol; glucocorticoid

In multiple sclerosis, the myelin sheath is attacked by autoimmune action, leading to a __________ in conduction velocity along the __________.

decrease; axon

A patient with Parkinson's disease can be treated with an oral medication that can be enzymatically converted to __________.

dopamine

Parkinson's disease is due to loss of __________ neurons.

dopaminergic

Binding of the neurotransmitter to its receptor causes the membrane to __________.

either depolarize or hyperpolarize (Yes, the neurotransmitter can cause the postsynaptic membrane to either depolarize or hyperpolarize, depending on which ion channels are opened.)

Blue color blindness also exits, but the gene is not on the X chromosome. It is located on one of the autosomes; autosomes are all the chromosomes except the X and Y chromosomes. This condition is __________ .

equally seen in both male and female

The major diagnostic criterion that must be found in order to diagnose post-traumatic stress disorder is the individual __________.

experienced a stressful (traumatic) event in the past

Cholinergic neurons are found __________.

in both the CNS and peripheral nervous system

Synesthesia is a condition where one involuntary sensory pathway leads to a(n) __________ sensation from another involuntary sensory pathway; the two pathways seem to act in a cross-sensing manner.

inappropriate

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.

Glial cells are non-excitable cells in the nervous system. Their functions are supportive to the neurons. One type of glial cell is the astrocyte. One of its functions is to __________.

maintain the proper extracellular environment around the central nervous system neuron

The most common type of color blindness is red-green color blindness. This condition is generally caused by a genetic defect in the photopigments of red or green cones. It is a recessive disorder involving the X chromosome. It is most commonly seen in __________, because they have __________ chromosome(s).

males; only one X

When a patient has a stroke and suffers some immediate neurological deficits, these deficits __________ with time.

may increase or decrease

Enkephalin is a neuropeptide that initiates a "slow" response in the postsynaptic cell; to which type of receptor does enkephalin bind?

metabotropic receptorsWhat is the name of the process through which one neuron receives communication from several other "upstream" neurons?

The most successful treatment currently involves the use of __________.

mirrors

The older theory believed to cause phantom limb pain was that ___________.

nerve endings in the stump were reactivated

A molecule that carries information across a synaptic cleft is a

neurotransmitter. (Neurotransmitter molecules carry information across a synaptic cleft.)

Researchers find that it is __________ during development for certain sensory pathways to form improper connections with another sensory pathway.

normal

The neurological mechanism associated with phantom limb is __________

not known and is still being investigated

The most debilatating effect perceived by phantom sensations is __________.

pain

One type of glial cell is the oligodendrocyte; its function is to __________.

place myelin around certain neurons in the central nervous system

In a synapse, neurotransmitters are stored in vesicles located in the __________.

presynaptic neuron (Yes, neurotransmitters are stored in the axon terminals of the presynaptic neuron.)

You are working on a new medication to selectively kill cancer cells. You test the drug on a culture of normal neurons to check for any side effects. Despite the presence of the drug, a normal resting membrane potential of −−70 mVmV is maintained. Look at each of the figures below to analyze how the drug might be affecting the neuron. Figure A shows neuron activity under normal, or control, conditions (without the drug). Figure B shows neuron activity that has been altered due to exposure to the drug. Based on these results, the drug is most likely __________.

preventing Na+-gated channels from opening

One type of glial cell is the microglial cell. One of its functions is to __________.

protect the central nervous system from foreign matter, such as remnants of dead or injured cells

A second diagnostic criterion used to diagnose post-traumatic stress disorder is one that is psychological; it involves the individual having __________.

re-experiencing of the traumatic event

The __________ are responsible for seeing black and white during relatively low-light conditions.

rods

There are two types of photoreceptors in the retina; they are the __________ and __________.

rods; cones

Each sensory modality (light, sound, chemicals, etc.) has its own __________, where the sensation is perceived in the brain.

sensory area

Synesthesia involves incorrect synaptic transmissions at either the __________ or the association areas or both.

sensory area

The reason that SSRIs are used for treatment for post-traumatic stress disorder is that there appears to be a low level of __________ in individuals with this condition.

serotonin

Muscle weakness, blurred vision, and inability to maintain balance can, in part, be explained by failure of adequate action of the __________ neurons leading to skeletal muscle contractions.

somatic motor

Each sensory modality has a(n) __________ area, for that sensation that interprets the sensation.

specific sensation association

Sensory inputs from several __________ areas will be sent to a multimodal association area that combines several sensations, for the purpose of giving a composite meaning to the sensory perceptions from several areas; either this information will be stored or a decision for action will be made.

specific sensation association

If by using some radiological technique, a person is found to have a partial occlusion in one of the larger blood vessels in the brain, that person may receive a surgically implanted __________. It is used to keep the blood vessel open.

stent

The condition of __________ pain has a different cause than that of phantom limb pain.

stump

The condition of __________ pain can be simulated by placing a stimulus to the __________, which is not the case with phantom limb pain.

stump; stump

The finding of hyper-responsiveness in these patients is associated with the __________.

sympathetic nervous system

The small space between the sending neuron and the receiving neuron is the

synaptic cleft. (The synaptic cleft is the small space between the sending neuron and the receiving neuron.)

If a blood clot is blocking off a blood vessel, the physician may give __________, which is a thrombolytic agent (breaks down clots).

tPA (tissue plasminogen activator)

If you added chloride ions to a neuron, __________.

the membrane potential would become more negative (Additional Cl- would increase the number of negative ions inside the cell, which would make the membrane potential more negative.)

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential. (If the receiving neuron is more negative inside, it is less likely to generate an action potential.)

Which of the following does NOT require ATP hydrolysis?

the repolarization phase of the action potential (Repolarization is caused by closure of voltage-gated Na+ channels and opening of voltage-gated K+ channels. Neither of these requires ATP hydrolysis.)

The current theory postulates that ________.

there are problems with second- and third-order pain transmitting neurons associated with the missing limb

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

One possible early warning sign for stroke, particularly the obstructive type, is the occasional occurrence of __________.

transient ischemic attacks (TIAs)

The two classifications for a stroke are __________ or __________.

vascular occlusion; vascular hemorrhage

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

voltage-gated Ca2+ channels (Yes, opening of these channels causes calcium to move into the axon terminal. Calcium inside the neuron causes the vesicles to merge with the membrane and release the neurotransmitter via exocytosis into the synaptic cleft.)

Researchers report that if a person with synesthesia hears the word "dog" and sees green, they __________ see green and then hear the word "dog."

will not