human phys midterm 2

What is(are) true after the myosin ATPase hydrolyzes ATP into ADP + P_i?

• The two products (ADP + P_i) stay attached to the myosin head.

• The myosin head rotates and binds to a different G-actin molecule, ready for the power stroke.

What will happen to the velocity of muscle shortening as the load on the muscle increases?

It will decrease.

What directly or indirectly influences the force generated by a skeletal muscle?

• the number of muscle fibers contracting

• the force generated by individual muscle fibers

• the number of active cross-bridges formed

In which type of contraction does a muscle contract but does not change length?

isometric

Which of the following statements is true about smooth muscle?

• The thin and thick filaments have an oblique arrangement.

• It is the only type of muscle that experiences slow wave potentials.

• It has the fastest myosin ATPase activity compared to skeletal and cardiac muscle

• Actin and myosin generate force through the crossbridge cycle.

• It receives neural input from the somatic nervous system

• Contraction is subject to the greatest diversity of hormonal influence of all muscle types.

• The thin and thick filaments have an oblique arrangement.

• It is the only type of muscle that experiences slow wave potentials.

• Actin and myosin generate force through the crossbridge cycle.

• Contraction is subject to the greatest diversity of hormonal influence of all muscle types.

10 events in the correct sequence for skeletal muscle?

1. Acetylcholine binds to receptors on the motor end plate.

2. The ligand-gated ion channels open, causing depolarization

3. The end plate potentials trigger action potentials.

4. Action potentials propagate into the interior of the cell along transverse tubule membrane.

5. Ca²⁺ is released from the sarcoplasmic reticulum.

6. Ca²⁺ binds to troponin, moving tropomyosin.

7. Binding sites on actin are uncovered, allowing myosin to bind and carry out power strokes.

8. Force increases.

9. Ca²⁺ is pumped into the sarcoplasmic reticulum.

10. Force decreases.

What occurs during complete tetanus?

• Cytosolic calcium levels are high enough to saturate all the troponin molecules.

• The muscle fiber is producing maximal tension.

• Muscle twitches fuse into a single smooth plateau.

• Action potential frequency is higher than the fused muscle twitch frequency.

What initiates contraction in smooth muscle?

Calcium binding to calmodulin

Which skeletal muscle types would have: 

• highest capillary density,

• highest myoglobin content, and

• highest resistance to fatigue?

• red fibers

• slow twitch fibers

• oxidative fibers

Which molecules are common to both cardiac and skeletal muscle crossbridge cycling?

• tropomyosin

• myosin

• troponin

• actin

Why does muscle tension decrease at short muscle lengths?

• The Z lines come into contact with the thick filaments

• The thin filaments at opposite ends of the sarcomere overlap

Which is the fastest way that a skeletal muscle cell can generate ATP to power muscle contraction?

The high-energy phosphate on phosphocreatine is transferred to ADP creating more ATP

What happens when an action potential travels along the sarcolemma of a muscle cell?

• Ca²⁺ flows down its concentration gradient through the ryanodine receptors

• DHP receptors in the T-tubule undergo a conformational change

What is the term to describe when thick and thin filaments bind together during a skeletal muscle contraction?

crossbridge

Put the following structures in order of largest to smallest:

• fascicle

• muscle fiber

• myofibril

• actin

• skeletal muscle

• thin filament

1. skeletal muscle

2. fascicle

3. muscle fiber

4. myofibril

5. thin filament

6. actin

Which of the following is(are) true about small motor units?

• They are innervated by motor neurons with a relatively high threshold for firing an action potential

• They contain fatigue-resistant, slow-twitch fibers.

• They require more excitatory input to fire action potentials.

• They tend to be recruited first during a contraction

• They generate less tension than large motor units

• They contain fatigue-resistant, slow-twitch fibers

• They tend to be recruited first during a contraction

• They generate less tension than large motor units

Put the following steps in order for smooth muscle contraction starting with activation of a smooth muscle cell:

• Ca²⁺ binds to calmodulin.

• Crossbridges form.

• Cytosolic Ca²⁺ increases.

• Muscle tension is created.

• Myosin ATPase activity increases.

• Myosin light chain kinase is phosphorylated

1. Cytosolic Ca²⁺ increases.

2. Ca²⁺ binds to calmodulin.

3. Myosin light chain kinase is phosphorylated

4. Myosin ATPase activity increases.

5. Crossbridges form.

6. Muscle tension is created.

Which process contributes to smooth muscle relaxation?

Dephosphorylation of myosin by a phosphatase

In which type(s) of muscle does myosin have ATPase activity?

• smooth

• cardiac

• skeletal

Which fiber types would have the largest diameter and highest force-generating capacity?

• fast twitch fibers

• glycolytic fibers

• white fibers

A skeletal muscle is in the rigor state.

Put the events of the crossbridge cycle in skeletal muscle the correct order, starting with the next step.

• Rigor state

• Release of P_i

• Binding of ATP

• ATP hydrolysis

• Release of ADP

• Power stroke occurs

1. Binding of ATP

2. ATP hydrolysis

3. Release of P_i

4. Power stroke occurs

5. Release of ADP

6. Rigor state

What can influence the amount of force a muscle can generate?

• number of sarcomeres in parallel

• length of individual sarcomeres

• cross-sectional diameter of the muscle fiber

What characteristics are associated with type IIB/IIX skeletal muscle fibers?

• Fast myosin ATPase activity

• large diameter fibers

• low capillary density

What is a motor unit?

A somatic motor neuron and all of the muscle fibers innervated by it

What is true after the myosin ATPase hydrolyzes ATP into ADP + P_i?

• The myosin head rotates and binds to a different G-actin molecule, ready for the power stroke

• The two products (ADP + P_i) stay attached to the myosin head

Which of the following statements about skeletal muscle contractions is true?

• the sarcomeres shorten during both isometric and isotonic contractions

• many body movements involve purely isotonic contractions

• isometric and isotonic contractions are all or nothing events

The sarcomeres shorten during both isometric and isotonic contractions

What is the term that describes when a muscle does not have time to fully relax between stimuli and twitches build on each other?

summation

In what ways is cardiac muscle similar to smooth muscle?

• innervated by autonomic neurons

• has actin and myosin

• possesses pacemaker cells

• contains gap junctions

Which of these statements is(are) true about single- and multi-unit smooth muscle cells? 

• Only single-unit muscle cells have gap junctions

• Single-unit cells function independently.

• Multi-unit cells contract as a single unit

• Multi-unit muscle cells must be stimulated independently.

• Only single-unit muscle cells have gap junctions

• Multi-unit muscle cells must be stimulated independently.

Which molecules are common to both skeletal and smooth muscle crossbridge cycling?

myosin and actin

An increase in the force generated by a muscle is achieved by the __________ of more motor units.

recruitment

Smooth muscle is similar to skeletal muscle in which ways?

• Both possess sarcoplasmic reticulum containing Ca²

• Both possess actin and myosin

Z disk?

attachment site for thin filaments

I band?

region occupied by only thin filaments

A band?

region of overlap between thick and thin filaments

M line?

attachment site for thick filaments

H zone?

region occupied by only thick filaments

What do you find on thick filaments?

actin binding sites and ATPase activity

What is true of cardiac contractile cells in contrast to most other types of excitable cell?

they have a plateau phase in the action potential

An increase in which factors would increase blood vessel resistance?

• increase in vessel length

• increase in viscosity of the blood

How does sympathetic activity lead to increased ventricular contractility?

• Increasing the flow of calcium into the cytosol from the extracellular fluid

• Increasing the rate of removal of calcium from the cytosol

• Increasing calcium stores in the sarcoplasmic reticulum

Which of the following correctly correlates the electrical signals of the ECG with the mechanical events of the cardiac cycle?

• QRS complex: period of ventricular diastole

• QRS complex: period of atrial systole

• P-R segment: period of atrial systole

• T-P segment: period of ventricular systole

P-R segment: period of atrial systole

What is similar about the actions of norepinephrine and acetylcholine on pacemaker cells?

both affect calcium channels and both affect heart rate

Which of the following increase stroke volume? 

• Constriction of veins due to norepinephrine binding to alpha adrenergic receptors

• skeletal muscle activity during exercise

• an increase in contractile fiber length

During the pacemaker potential, membrane permeability increases for which ions?

calcium, potassium, and sodium

What is occurring during isovolumic ventricular relaxation?

• blood volume in the ventricles is at its lowest level

• semilunar valves close

Put the following events of the cardiac cycle in the correct order, starting with the QRS complex:              

• ventricular systole

• T wave

• ventricular pressure decreases below pressure in aorta

• second heart sound

1. ventricular systole

2. T wave

3. ventricular pressure decreases below pressure in aorta

4. second heart sound

Which of the following statements about the pulmonary and systemic circuits are true?

• the pulmonary veins carry deoxygenated blood away from the lungs

• the aorta carries oxygenated blood away from the heart

• the pulmonary arteries carry oxygenated blood toward the lungs

• the vena cavae carry deoxygenated blood toward the heart

• the aorta carries oxygenated blood away from the heart

• the vena cavae carry deoxygenated blood toward the heart

What would increase venous return?

• venoconstriction

• breathing

• muscle contraction

Imagine vasoconstriction causes a blood vessel to decrease its internal diameter by half, but the pressure gradient does not change. Would this have any effect on blood flow

blood flow would decrease 16 fold

What is true regarding ventricular volumes?

• An increase in the force of ventricular contraction decreases the end systolic volume

• The larger the end diastolic volume, the larger the stroke volume becomes

How is calcium removed from the cytosol of cardiac muscle cells?

• Ca²⁺/Na⁺ exchangers in the plasma membrane

• Ca²⁺ ATPases in the sarcoplasmic reticulum

Which of the following will increase the force of contraction of the ventricles?

• increasing arterial pressure

• increasing parasympathetic activity

• increasing end diastolic volume

increasing end diastolic volume

The second heart sound is most directly correlated with which aspect of the ECG?

T wave

Put the following structures involved in cardiac impulse conduction in the correct order:

• AV bundle (bundle of His)

• AV node

• bundle branches

• internodal pathways

• Purkinje fibers at apex of heart

• SA node

1. SA node

2. internodal pathways

3. AV node

4. AV bundle (bundle of His)

5. bundle branches

6. Purkinje fibers at apex of heart

What influences ventricular contractility?

• calcium

• afterload

• increased arterial pressure

• epinephrine/norepinephrine

What is the effect of parasympathetic input to the heart?

it opens additional potassium channels in pacemaker cells

What can increase cardiac output?

increasing venous return and increasing ventricular filling time

There is a high degree of overlap between the action potential and the contractile response in cardiac fibers. Why?

The overlap prevents summation of cardiac muscle contractions; it is critical that the heart has time to relax and fill with blood before the next contraction.

How does sympathetic activity lead to increased ventricular contractility?

• Increasing the flow of calcium into the cytosol from the extracellular fluid

• Increasing the rate of removal of calcium from the cytosol

• Increasing calcium stores in the sarcoplasmic reticulum

What is occuring during isovolumic ventricular contraction?

• no blood is being ejected from the ventricles

• ventricular pressure is less than the pressure in the aorta

• pressure in the ventricles is increasing

How do pacemaker cells differ from contractile cells?

Pacemakers are autorhythmic but do not contract, whereas contractile cells generate a force of contraction

What mechanical event will occur as a result of the electrical events that produce the QRS complex in an electrocardiogram (ECG)?

ventricular systole

What results in opening of the pulmonary semilunar valve?

When the right ventricle pressure is greater than pulmonary artery pressure

QRS complex?

ventricular deploarization

T wave?

ventricular repolarization

P wave?

atrial depolarization

unable to discern in ECG

atrial repolarization

Trace the path of a red blood cell through the heart, starting as it enters from the systemic circulation:

• aorta

• left atrium

• left ventricle

• lungs

• pulmonary artery

• pulmonary vein

• right atrium

• right ventricle

1. right atrium

2. right ventricle

3. pulmonary artery

4. lungs

5. pulmonary vein

6. left atrium

7. left ventricle

8. aorta

What is true of the contractile cells of the heart?

• the repolarizing phase is due to potassium flow

• they have a plateau potential

• the depolarizing phase of the action potential is due to sodium flow

What effect would a decrease in venous return produce?

• decreased cardiac output

• decreased stroke volume

What does the Frank-Starling law state?

Stroke volume increases as end-diastolic volume increases

Put the following events of the cardiac cycle in the correct order, starting with the ventricular filling phase:            

• first heart sound

• isovolumic ventricular relaxation

• P wave of ECG

• ventricular pressure greater than atrial pressure

1. P wave of ECG

2. ventricular pressure greater than atrial pressure

3. first heart sound

4. isovolumic ventricular relaxation

What is true of the autorhythmic cells of the heart?

• the repolarizing phase is due to potassium flow

• they have an unstable membrane potential (pacemaker potential)

• the depolarizing phase of the action potential is due to calcium flow

What factors influence blood vessel resistance?

• vessel length

• vessel radius

• blood viscosity

A patient's blood pressure is determined by sphygmomanometry to be 185/117. At what pressure did the Korotkoff sounds disappear and why?

About 117 mmHg, because cuff pressure is below diastolic pressure and no longer causes turbulent blood flow

What is true of the velocity of blood flow through the capillaries compared to the aorta, and why?

Velocity is slower because the overall cross-sectional area of all capillaries is larger.

What happens in active hyperemia?

Low oxygen levels act directly on the smooth muscle of blood vessels

During which phase of contraction is blood pressure highest?

ventricular systole

Calcium channel blockers bind to Ca²⁺ channel proteins in vascular smooth muscle. What effect would this have on the blood vessels and on blood pressure?

dilation of blood vessels and decreased blood pressure

Which stimuli would result in an increase in blood flow to a tissue?

• Increase in the level of carbon dioxide at the tissue

• increase in histamine at the tissue

Functions of the lymphatic system include?

• Prevention of fluid accumulation in the tissues (edema) and return of fluid accumulated in tissues to the venous system

• immunity

• Prevention of fluid accumulation in the tissues (edema)

• Return of fluid accumulated in tissues to venous system

What would cause a decrease in mean arterial pressure (MAP)?

• decreased heart rate

• decreased stroke volume

• decreased total peripheral resistance

What is the term for the pressure exerted by the presence of plasma proteins within the capillaries?

colloid osmotic pressure

What would cause an increase in blood pressure?

• decrease in arterial diameter

• sympathetic stimulation

• an increase in arterial resistance

When someone stands up too quickly, there can be reduced blood flow to the upper body (and brain) caused by gravity and pooling of blood in the lower limbs. What is likely to happen as a result of someone standing up too quickly and having reduced blood flow to the upper body?

• increased activity at adrenergic receptors

• increased release of norepinephrine

What vessels contain one-way valves?

veins and lymphatic

Lymphatic circulation contains which types of blood vessels?

veins and capillaries

What are lower in capillaries as compared to arteries?

• velocity

• pressure

• vessel radius

What are risk factors in the formation of atherosclerotic plaques, which can cause coronary artery disease?

• Elevated low-density lipoprotein-cholesterol (LDL-C)

• smoking

• hypertension

• obesity

One aspect of the fight-or-flight response is widespread vasoconstriction. Which of the following accounts for this seemingly counterproductive phenomenon?

Constriction occurs only in nonessential tissues, whereas dilation occurs in essential tissues

What is the process by which blood flow is increased to skeletal and cardiac muscle during exercise?

active hyperemia

How do you determine diastolic blood pressure when measuring blood pressure with a sphygmomanometer?

It is the pressure in the blood pressure cuff as it is released when no further turbulent sounds are heard through the stethoscope.

What is the mathematical equation for calculating mean arterial pressure (MAP)?

diastolic pressure + 1/3 (systolic pressure - diastolic pressure)

What will increase as part of the baroreceptor reflex response to hemorrhage (blood loss)?

heart rate and venous return

Which of the following chemical signals would increase mean arterial pressure (MAP)?

norepinephrine and angiotensin II via angiotensin receptor

veins?

expandable volume resevoir

arterioles?

Allow blood flow to be (re)distributed to individual tissues, as needed

heart?

Pump that creates a pressure gradient

capillaries?

Site of exchange of substance between blood and cells