Physiology questions

Physiology questions ...Mainly for medical students , are you up for the challenge

published on December 20, 20170 responses 0

Which part of the heart’s conduction system
sends the impulse that begins the process of

Atrioventricular (AV) node
Sinoatrial (SA) node
Bundle of His
Purkinje fibers

An impulse travel through the heart’s
conduction system in which of the following

Atrioventricular (AV) node, bundle of His,
sinoatrial (SA) node, bundle branches, Purkinje
Bundle of His, sinoatrial (SA) node, bundle
branches, Purkinje fibers, atrioventricular (AV)
Purkinje fibers, bundle branches, bundle of His,
sinoatrial (SA) node, atrioventricular (AV) node
. Sinoatrial (SA) node, atrioventricular (AV) node,
bundle of His, bundle branches, Purkinje fibers

The function of coronary circulation is to:

Regulate the cardiac cycle
Deliver oxygenated blood from the lungs into
systemic circulation
Supply cardiac muscle with oxygenated blood
and drain deoxygenated blood from it
Drain excess blood from the ventricles

The layer of the heart wall primarily responsible
for the heart’s pumping action is the:


Cardiac output is determined from which of the
following factors?

Heart rate and blood pressure
Oxygen consumption and carbon dioxide
Stroke volume and heart rate
Ventricular contraction and venous return

The volume of blood, in liters, that each ventricle
of the heart ejects every minute is known as:

stroke volume
cardiac output
heart rate
blood pressure

Oxygenated blood flows from the heart through
systemic circulation in which order?

Arteries, veins, capillaries, arterioles, venules
Veins, venules, capillaries, arterioles, arteries
Arteries, arterioles, capillaries, venules, veins
Capillaries, veins, venules, arterioles, arteries

Arteries are structurally different from veins in
which way?

They have thicker and stretchier walls to
accommodate higher pressures
They lack valves
They have a tunica media
a and b

The purpose of valves is to:

Filter debris from the bloodstream
Ensure unidirectional blood flow
Move blood through arteries
All of the above

In a resting state, the plasma membrane of a
neuron is:


Signals are passed through the nervous system:

a and b

The wave of depolarization that is propagated
down an axon is known as the:

Graded potential
Resting potential
Action potential
Refractory period

Which of the following statements about
neurotransmitters is false?

Excitatory neurotransmitters may generate an
action potential in the neuron they reach
At a neuromuscular junction, acetylcholine has
inhibitory effects
Dopamine helps regulate muscle tone
Norepinephrine is found in both the central
and peripheral nervous systems

. A signal moves through the parts of a single
neuron in what order?

Dendrites, cell body, axon, axon terminals
Axon terminals, axon, cell body, dendrites
Cell body, dendrites, axon, axon terminals
Axon, dendrites, axon terminals, cell body

A myelinated axon transmits a signal................... a
non-myelinated axon

More slowly than
More quickly than
At the same rate as
More accurately than

When a neuron is not transmitting a signal, which
of the following is true?

The cell membrane is depolarized
The cell contains an action potential
The cell cannot be stimulated by
The net charge inside the cell is negative

Which type of cells phagocytize debris in the
central nervous system?

Ependymal cells

. If the nicotinic channels at the neuromuscular junction pass both Na+ and K+ why does stimulation of these channels cause depolarization of the skeletal muscle?

The driving force for K+ is very large.
The driving force for Na+ is very large.
The K+ channels are not open.
The Na+ ion is smaller and therefore passes more easily.
The resting membrane potential is closer to the Na+ Nernst

What effect will hypocalcemia have on the
neuromuscular junction?

Increased release of acetylcholine
Increased muscle depolarization(Na overstimulation)
C. Decreased activation of nicotinic receptors
D. Inhibition of acetylcholine esterases
E. Increased influx of Ca2+ into motor nerve terminal

Most of the ATP generated in nerve cells is utilized to energize the:

Na-Ca exchanger
H-ATPase in the cell membrane
Na-K ATPase
synthesis of proteins

Fast anterograde transport occurs at a rate of about:

40 mm/day
400 mm/day
1 mm/day
10 mm/day

The largest known axons are found in:


The normal resting cardiac muscle cell is most permeable to:


The membrane potential at which net flux of an ion across the membrane is zero is called

resting membrane potential
spike potential
threshold potential
electrotonic potential
equilibrium potential of that ion

The resting membrane potential of ventricular cardiomyocytes is closest to the equilibrium potential for:


The Nernst potential (also called equilibrium potential) is positive for:

Na and Cl
Na and K
Na and Ca
K and Cl

The equilibrium potential of chloride in mammalian spinal motor neurons is typically about

+ 20 mV
minus 40 mV (inside negative)
minus 70 mV (inside negative
minus 90 mV (inside negative)

The resting membrane potential of some neurons is equal to the equilibrium potential of:


If intracellular and extracellular potassium concentrations are approximately 140 mmol/L and 14 mmol/L respectively, the equilibrium potential for potassium is approximately:

minus 30 mV inside negative
minus 60 mV inside negative
minus 90 mV inside negative
minus 120 mV inside negative

Which one of the following increases excitability of cardiac muscle?

Increase in ECF [K+] from 5 to 10 mM
Increase in ECF [K+] from 5 to 70 mM
Decrease in ECF [K+] from 5 to 1.4 mM

Hypokalemia would be expected to result in:

increased neuronal excitability
a more negative RMP
no change in RMP
a decrease in firing level of neurons

The membrane potential of cardiac muscle cells is most affected by even a small change in plasma concentration of:


Which of the following would justify excluding sodium conductance from the equation for estimating resting membrane potential in skeletal muscle fibers?

Extracellular [Na] is higher than ICF [Na]
Na-K pump extrudes 3 Na for 2 K pumped in
Negligible Na permeability of the resting membrane
Unexcited cells are equally permeable to Na and K

Excitability, in neurophysiology, is defined as:

presence of a resting membrane potential
use of more than 30% of ATP synthesized for powering the Na-K ATPase
response to a threshold stimulus with a propagated action potential
presence of voltage gated ion channels in a tissue

Physiologically, the site of origin in motor neurons of conducted impulses is the:

dendritic zone
axon hillock
terminal buttons
node of Ranvier

In motor neurons, the portion of the cell with the lowest threshold for the production of a fullfledged action potential is:

initial segment
dendritic zone
node of Ranvier

In the CNS, the membranes that wrap around myelinated neurons are those of:

Schwann cells
endothelial cells

The number of Na channels per square micrometer of membrane in myelinated mammalian neurons is maximum in the:

cell body
dendritic zone
initial segment
node of Ranvier

Which one of the following statements about electrotonic potentials is incorrect?

They are graded responses.
They are local (non-propagated) responses.
They may be depolarizing or hyperpolarizing.
They are produced by a threshold stimulus

A stronger than normal stimulus can cause excitation of nerve or muscle during the

absolute refractory period
Relative refractory period
pike potential

An excitable cell has an RMP of -70 mV and a firing level of - 50 mV. This cell would be inexcitable when its membrane potential is

-30 mV
- 55 mV
- 70 mV
- 90 mV

For the same conditions (as in the above question), the cell would be most excitable when its membrane potential is:

- 30 mV
- 55 mV
-70 mV
- 90 mV

Conduction speed is slowest in the:

SA node
atrial pathways
bundle of His
Purkinje system
Ventricular myocardium

. What is the effect of vagal stimulation on the membrane potential of the SA node?

It increases an inward calcium current
It increases the slope of the prepotential.
It activates a hyperpolarizing potassium current.
It increases intracellular cAMP.

Activation of beta-adrenergic receptors in the heart is normally associated with which of the following?

Decrease in the slope of phase 4 depolarization in SA nodal cells.
Decrease in conduction speed through AV node.
Inhibition of Ca induced Ca release following depolarization in ventricular myocytes.
Accelerated sequestration of Ca in the sarcoplasmic reticulum by the Ca-ATPase
Reduction in the rate of rise in ventricular pressure during isovolumic contraction

Cardiac muscle cannot be tetanized because of:

its slow rate of repolarization
calcium influx during phase II
Intrinsic heart rate is determined by:

Intrinsic heart rate is determined by:

administration of atropine
beta-adrenergic receptor blockade
IV administration of atropine and atenolol

The ability of the AV node to generate its own impulses when the sinus node is “sick” is due to:

a constant phase 4 membrane potential
slow calcium entry during phase zero
spontaneous diastolic depolarization
the absence of prepotentials

T wave inversion occurs when ventricular repolarization occurs from:

endocardium to epicardium
epicardium to endocardium
apex to base of the heart
base to apex of the heart

Which of the following is more likely to produce an S3 sound?

Left ventricular hypertrophy
Right ventricular hypertrophy
Left atrial enlargement
Left ventricular cardiomyopathy

The inotropic state of cardiac muscle can be altered because:

it has the ability to recruit or diminish the number of muscle cells activated during a contraction
its intracellular calcium concentration can be altered
force generation in cardiac muscle is modulated by Ca++/calmodulin interaction
it functions on the ascending limb of its isometric length tension curve
its multinucleated anatomical property

When the vagus stimulates the sinoatrial node (SAN) the nodal cells respond quickly showing a higher minimum repolarization potential. Fast activation by acetylcholine of the following ionic channel is primarily responsible for this effect.

A voltage sensitive Na+ channel
The L-type calcium channel
The T-type calcium channel
A receptor activated K+ channel

Our astronaut has returned to normal gravity after orbiting the earth at an altitude of 250 miles for three months. The instantaneous effect on the heart after arriving at a normal gravity environment would be:

An increase in afterload
A decrease in preload
An increase in right atrial pressure
A decreased parasympathetic stimulation of the heart

Complete depolarization of the ventricles eliminates the electrical dipoles that were formed during this process and brings back the ECG to zero potential. When this occurs we enter into a portion of the ECG called:

The PR interval
ST segment
QRS complex
QT interval
P wave

A mother brings her 5 year old child into the pediatric ward complaining about the child being too tired during the day with little activity for a normal 5 year old. Your examination reveals that the child has a normal weight but she looks pale and there is a strange puffiness to her features. Blood tests come up with a very low Albumin level in plasma and confirm your initial thoughts about possible Kwashiorkor disease. The mother indicates that she only gives the child potato fries or chips since this is the only food that she will eat. As soon as a normal albumin level is restored in the child, the significant level of muscle wasting due to the malnutrition is revealed and the puffiness disappears as well as the normal weight. The puffiness was a result of:

Increased capillary oncotic pressure
Decreased capillary filtration pressure
Decreased capillary oncotic pressure
Too much fat from the fries

As a result of one of the following you will observe a lower end systolic volume in the heart?

Effect of norepinephrine
Increased preload
increased mean arterial pressure
decreased end diastolic volume

In the event of strong parasympathetic stimulation to the heart (Vagus Nerve) the rhythmical
excitation can stop and also block transmission through the AV Node, the ventricles stop beating
for 5-20 seconds, but then at some point the Purkinje Fibers develop rhythm of their own at a
rate of 15-40 beats per minute. The term that best describes this is:

Vasovagal Reaction
Wolf Parkinson White Syndrome
Atrial Escape
Ventricular Escape

The dP/dt is an index of cardiac contractility that can be measured by relating the rise in ventricular pressure during systole with:

Stroke volume

Match the definition given to the correct term from the list: Diminished perfusion to tissues


Complete lack of oxygen


Match the definition given to the correct term from the list: Cardiac output decreases below the pressure required to deliver nutrients to the tissues


A skeletal muscle that is depleted of its ATP supply will gradually stiffen and fail to relax. This is because ATP is necessary to:

provide the energy for relaxation
maintain the separation of thick and thin filaments when the muscle is at rest.
allow the thick and thin filaments to detach from each other during the cross-bridge cycle.
promote the binding of calcium ions to the regulatory proteins and cause relaxation

Calcium ions are required for the normal activation of all muscle types. Which statement below most closely describes the role of calcium ions in the control of skeletal muscle contraction?

The binding of calcium ions to regulatory proteins on the thin filaments removes the inhibition of actin-myosin interaction
The binding of calcium ions to the thick filament regulatory proteins activates the enzymatic activity of the myosin molecules
Calcium ions serve as a direct chemical inhibitor of the interaction between actin and myosin.
A high concentration of calcium ions in the myofilament space is required to maintain muscle in a relaxed state

Synapses are communication points between two neurons or a neuron and effector such as a muscle. Not all synapses are equal, based on your current knowledge of synapses select the statement that best describes a chemical synapse:

The chemical synapse mediates faster synaptic transmission compared to _the electrical synapse
Since in the chemical synapse the pre-synaptic membrane is tightly connected to the post-synaptic cell via the connexons, the flow of ions between the neurons occurs bi directionally.
The chemical synapse involves the Ca2+ dependent release of neurotransmitters into the synaptic cleft via exocytosis.
Similar to the electrical synapse, gap junction channels are part of the chemical synapse. E. None of the above statements are correct

In the face of insufficient oxygen to meet its current metabolic requirements, a contracting skeletal muscle:

quickly loses its ability to contract and relaxes until oxygen is again available
can maintain contraction by using metabolic pathways that do not require oxygen consumption
maintains contraction by using a large internal store of ATP that is kept in reserve
contracts more slowly at a given force, resulting in a saving of energy.

A researcher studies membrane potential of isolated neurons. He reports two action potentials for the same neuron: the first one depolarizes the membrane to +50 mV, while the second one reaches +11 mV. Which of the following manipulations by the researcher best explains the lower magnitude of the second action potential?

Decrease sodium concentration outside the cell
Decreased sodium concentration inside the cell
Decreased potassium concentration inside the cell
Decreased potassium concentration outside the cellll
Increased calcium concentration outside the ce

The trigger zone that integrates incoming signals from other cells and initiates an action potential to send down the axon is rich in Na+ channels. This zone is best known as:

Axon trunk
Axon hillock
Dendritic trunk
Dendritic spines

Joe is a 15-year-old who belongs to the school track team. After a recent competition he felt extremely weak, unable to walk and had to be carried out of the tack. Next morning his pediatrician tested Joe's blood K+ levels before and after he ran on a treadmill. Joe's serum K+ was very low (2.2 mEq/L) after the treadmill run. His pediatrician diagnosed him with primary hypokalemic periodic paralysis. Joe was put on K+ supplementation. Why did K+ supplementation improved Joe's condition:

By normalizing serum K+ thus preventing further hyperpolarization of the membrane potential
By normalizing serum K+ thus preventing further depolarization of the membrane potential
By further decreasing K+ serum concentration thus causing depolarization of the membrane potential.
. By further decreasing K+ serum concentration thus causing hyperpolarization of the membrane potential

During an in vitro experiment, the membrane potential of a cell becomes hyperpolarized from - 75 to -120 mV. An inhibitory drug is applied to the bath resulting in depolarization of the membrane. Which of the following likely explains this effect?

Sodium channels become inactivated
The inhibitory drug is activating ligand gated potassium channels
The inhibitory drug is activating voltage gated sodium channels.
Inhibitory drugs normally depolarize the postsynaptic membrane.

your recording that occur spontaneously. Base on your physiology knowledge about neuromuscular junction physiology, you conclude that you are recording:

IPSPs in response to quantal glycine release
EPSPs in response to quantal glutamate release
mEPSPs in response to quantal acetylcholine release
mEPSPs in response to quantal GABA release
mEPSPs in response to neuropeptides release

Wendy is a 23-year-old photographer for a local magazine. Over the last 9 months she has been experiencing severe eye strain, tiredness while brushing her hair and teeth, and extreme fatigue. Her head physician evaluated her and he requested an antibody test, which confirmed myasthenia gravis. Wendy is put on pyridostigmine, an acetylcholinesterase inhibitor and felt much better. Pyridostigmine most likely improved Wendy's symptoms by

Decreasing synaptic concentration of Ach, thus decreasing its action
Decreasing the likelihood of an action potential occurring thus decreasing muscle contraction
Increasing synaptic concentration of Ach, thus prolonging its action
Increasing the interaction of SNARE's thus increasing the release of Ach.

If the nicotinic channels at the neuromuscular junction pass both Na+ and K+ why does stimulation of these channels cause depolarization of the skeletal muscle

The driving force for K+ is very large.
The driving force for Na+ is very large
The K+ channels are not open.
The Na+ ion is smaller and therefore passes more easily.
The resting membrane potential is closer to the Na+ Nernst potential

Botulinum toxin is used to treat certain eye disorders such as crossed eyes (strabismus) and uncontrolled blinking (blepharospasm), to treat muscle stiffness/spasms or movement disorders (such as cervical dystonia, torticollis), and to reduce the cosmetic appearance of wrinkles. The injection of botulinum toxin into skeletal muscle reduces

the amplitude of minature end plate potentials.
the frequency of minature end plate potentials.
the end plate potentials.
presynaptic Ca2+ influx.
Both B and C are correct.