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MCAT > Physiology 2 > Flashcards

Physiology 2 Flashcards

1
Q

Sodium ions in the cell are transported against their concentration gradient across the cell membrane into the intercellular fluid. The concentration difference across the cell membrane created by this transport mechanism also creates an energy gradient that can be tapped by allowing the sodium ion to cross the cell membrane back in

A

Secondary active transport

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2
Q

The ability of the SA node to serve as the heart’s pacemaker by repeatedly depolarizing and repolarizing without the necessity of external innervation is best attributed to which of the following characteristics?

A

Inherent leakiness to sodium and calcium channels

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3
Q

When an action potential reaches the terminus of an axon, which of the following ions is directly involved with the release of neurotransmitters from synaptic vesicles

A

Calcium

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4
Q

which of the following ECG waves represent(s) depolarization?

A

Both A and C
P only
QRS only

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5
Q

The part of the neuron with the lowest threshold (more positive potential than the normal resting potential) is the

A

Axon hillock

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6
Q

The mean electrical axis of the normal ventricles is

A

59 degrees

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7
Q

Voltage - gated channels are more characteristic of which of the following areas of the neuron?

A

Axon

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8
Q

T/F The direction of bipolar lead I is 0 degrees

A

TRUE

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9
Q

Both activation and inactivation gates are associated with which of the following channels?

A

Sodium

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10
Q

Which of the following areas of the heart has the fastest intrinsic rate of discharge (depolarization)?

A

SA Node

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11
Q

During the resting potential, before a stimulus is applied to the neuron, which of the following statements is true

A

The inactivation gate of the sodium channel is open

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12
Q

T/F Of the three bipolar limb leads, recording limb lead III is connected to the left arm (+) and the right arm (-)

A

FALSE

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13
Q

Which term is used to describe a change in the membrane potential from a resting membrane potential of -90mV to a membrane potential of -95mV

A

Hyperpolarization

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14
Q

In a typical ECG, which of the following waves occurs at the beginning of the contraction of the atria?

A

P

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15
Q

Skeletal muscle contraction requires the availability of ATP. Approximately 95% of the energy need for long term contraction is derived from which of the following processes?

A

Oxidative metabolism

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16
Q

84% of the blood volume is in the systemic circulation, of this 64% is in the

A

Veins

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17
Q

All of the following are characteristic of an action potential EXCEPT:

A

It occurs on the membrane of the cell body

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18
Q

Blood flow resistance is indirectly propagated to which of the following?

A

Vessel diameter

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19
Q

At what point in the action potential are both gates of the sodium channel open?

A

During depolarization

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20
Q

Considering the following statements:

  1. Veins are about 8 times more distensible than arteries
  2. Vascular compliance is directly proportional in volume increase and indirectly proportional to pressure
A

Both statements are true

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21
Q

Following the action potential, so many sodium channels are inactivated that no amount of stimulation will cause enough of them to open to elicit another action potential. What is the term given to this period?

A

Absolute refractory period

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22
Q

T/F Velocity of blood flow is inversely proportional to sacular cross-sectional area

A

TRUE

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23
Q

Cells that form myelin sheaths in the peripheral nervous system are

A

Schwann cells

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24
Q

Most of the systemic blood is found in which part of the system?

A

In the veins

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25
Q

Which of the following potential BEST describes the resting potential of a typical neuron is:

A

-90mV

26
Q

Circus movements are the basis of heart fibrillation. Which of the following statements is NOT true

A

Fibrillation may occur when the pathway around the circle is too short

27
Q

After neurotransmitters have been released into the synaptic cleft, neurotransmitter stimulation of postsynaptic membranes decreases over time because of:

A

All the above
Reuptake by presynaptic membrane
Diffusion away from site
Destruction by enzymes

28
Q

Which of the following conditions may result in tachycardia?

A

All of the above
Toxic conditions of the heart
Increased body temperature
Sympathetic nerve stimulation

29
Q

Which of the following statements is MOST ACCURATE regarding the immediate initiation of an action potential on the sarcolemma of a skeletal muscle cell at the neuromuscular junction?

A

Opening of ligand-gated sodium channels on the sarcolemma at the neuromuscular junction

30
Q

T/F The cause of high-voltage QRS complexes is most often due to hypertrophy of cardiac muscle tissue.

A

TRUE

31
Q

Cardiac muscle fibers and skeletal muscle fibers share a number of characteristics but also have a number of differences. Which of the following is a major SIMILARITY between the two types of fibers?

A

Both types of fibers have a sarcomeric arrangement

32
Q

Which of the following is the direction of bipolar lead III?

A

120 degrees

33
Q

Which feature, in particular, distinguishes a presynaptic terminal from other parts of the neuron?

A

Synaptic vesicles

34
Q

Of the three bipolar leads, which one is connected to both left and right arms?

A

Lead I

35
Q

Which of the following kinds of axons would conduct the fastest action potential?

A

Large diameter, myelinated

36
Q

Which of the following events is generally not seen on a typical ECG?

A

Ventricular repolarization

37
Q

T/F Baroreceptors located in the arterial walls of the arterial system sense an increase in arterial pressure and send inhibitory signals to the vasomotor region of the medulla. This results in a dilation of carotid arteries. Such a system is an example of a positive feedback system.

A

FALSE, negative feedback system

38
Q

Acetylcholine released from vagus nerve endings increases permeability of SA fiber membranes to potassium ion. Which of the following effects would occur?

A

Only A and B would occur
SA rhythm would decrease
Hyperpolarization of the fibers

39
Q

The degree of effectiveness with which a control system maintains constant conditions is referred to as

A

Gain

40
Q

Which of the following is more highly concentrated than the others listed in the intracellular environment?

A

Potassium

41
Q

In the sarcomeric arrangement, during relaxation, which of the following bands is composed of only myosin?

A

H band

42
Q

In skeletal muscle, ryanodine receptors are located where?

A

On the sarcoplasmic reticulum membrane

43
Q

Which of the following inactivates aceylcholinesterase and is useful in treating myasthenia gravis

A

Neostigmine

44
Q

If the end-diastolic volume is 110ml and the end-systolic volume is 30ml, the stroke volume is

A

80ml

45
Q

If the end-diastolic volume is 120ml and the end systolic volume is 50 ml, what is the approximate value of the ejection fraction?

A

60%

46
Q

Atrial contraction occurs?

A

During the last third of diastole

47
Q

In the ECG, the QRS wave represents which of the following heart actions?

A

Ventricular depolarization

48
Q

If a cell with a cytoplasmic concentration of 80% water is placed in a container of distilled water, which of the following best describes the response?

A

Water will move into the cell through the process of osmosis

49
Q

T/F Fast twitch (light) fiber have a higher concentration of mitochondria than slow twitch (red) fibers

A

FALSE

50
Q

T/F Cardiac muscle relaxation requires the removal of calcium from the cytoplasm of the cardiac muscle cell through two different transporters

A

TRUE

51
Q

Isovolumic contraction of the ventricles occurs

A

At the beginning of systole

52
Q

A selectivity filter with carbonyl oxygens is associated with which of the following channel types?

A

Potassium

53
Q

The diffusion potential that develops when a membrane is permeable to several different ions can be determined by which of the following?

A

Goldman equation

54
Q

In skeletal muscle, a cell is also known as a

A

Myofiber

55
Q

In the normal, resting heart, the P-R interval in the ECG is typically?

A

0.16 sec

56
Q

Depolarization of the atria begins in the SA node and spreads in all directions over the atria. The direction of the vector is generally in the directions of the axes of all three bipolar leads. This conclusion is true

A

Conclusion I: Normal ECGs for the atrial depolarizations are positive for all three leads
Only conclusion I is valid

57
Q

In the above ECG, which of the following heart activities is represented? (Lead III)

A

Sinus bradycardia

58
Q

T/F Velocity of blood flow is directly proportional to vascular cross-sectional area

A

FALSE

59
Q

If rate of blood flow through the entire circulatory system (=cardiac output) = 100ml/sec AND the pressure difference from the systemic arteries to the systemic veins = 100mmHg. The total peripheral resistance is equal to

A

1 PRU

60
Q

Which of the following properties is a measure of the ease with which a hollow viscous may be distended?

A

Compliance

MCAT (6 decks)

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