Skeletal Muscle Anatomy and Physiology

Individual skeletal muscle fibers ______________. More than one answer may be correct. Mark all that are correct.
A. have one nucleus
B. are striated
C. are branched
D. are elongated cells
E. have multiple nuclei

Within a skeletal muscle, the __________________ are dark bands.
A. A bands B. I bands C. E bands D. rubber bands

Skeletal muscle fibers can only ACTIVELY shorten (contract) and relax.
T / F

A somatic motor neuron initiates the contraction of a skeletal muscle fiber through the release of the
neurotransmitter _____________.
A. dopamine B. norepinephrine
C. GABA D. acetylcholine E. botulinum toxin

In terms of ionic flus, what does the binding of neurotransmitter at a NMJ (neuromuscular junction) do?

Define a motor neuron unit.

A skeletal muscle with an average motor unit size of 1 motor neuron/1,500 muscle fibers would most
likely be _________________.
A. powerful B. precise

How does the process of recruitment increase the force of a skeletal muscle’s contraction?

____________ are the primary components of thick myofilaments in skeletal muscle fibers.
A. The protein Actin
B. The protein Titin
C. The protein Myosin
D. The Z discs

During the contraction of a skeletal muscle fiber (cell) _______________, the distance between two Z lines
increases.
T / F

11. During the contraction of a skeletal muscle fiber _______________.
A. a sarcomere shortens
B. The length of actin filaments decreases
C. the length of the A band decreases
D. the length of myosin filaments decreases

12. Skeletal muscle fibers have numerous sarcomeres.
T / F

When a skeletal muscle is at rest, actin filaments and myosin filaments are attached to one another
via cross-bridges.
T / F

As skeletal muscle fibers contract, myosin heads undergo a power stroke when there is the
A. direct binding of calcium to the myosin head
B. phosphorylation of the myosin head
C. dephophorylation of the myosin head
D. direct binding of acetylcholine to the myosin head

How does Botulinum toxin lead to skeletal muscle paralysis?

Before a skeletal muscle fiber contracts, myosin heads are energized (or “cocked”) by _____________.
A. the direct binding of nicotine to the myosin head
B. phosphorylation of the myosin head
C. the direct binding of acetylcholine to the myosin head
D. the direct binding of calcium to the myosin head

Within a skeletal muscle fiber, ___________ are specialized structures that conduct action potentials to
the interior of the cell.
A. Sarcoplasmic reticulum
B. Transverse (T) tubules
C. Motor end plates
D. All of the above

During the contraction of a skeletal muscle fiber, __________ binds to troponin, which reveals myosin binding sites on thin filaments.
A. sodium B. potassium C. magnesium D. calcium

The sarcoplasmic reticulum of a skeletal muscle fiber ___________. More than one answer may be correct. Mark ALL that are correct.
A. stores potassium
B. stores calcium
C. possesses voltage-gated potassium channels
D. possesses calcium channels that open in response to increases in cytoplasmic calcium
E. possesses calcium channels that are physically coupled to voltage-gated calcium channels

20. During exercise (like heavy lifting), the strength of a SKELETAL muscle contraction is mostly due to _________________.
A. increases in acetylcholine release from a motor neuron in response to a single action potential
B. the recruitment of more motor units
C. increases in the production of voltage-gated potassium channels
D. all of the above

During the complete tetanus of a skeletal muscle (for example, a calf muscle from a frog), the muscle eventually begins to fatigue and fail to contract. Why is this the case?

In general, about 50% of the ATP used by a contracting skeletal muscle goes to moving myosin heads.
T / F

If a person has a high maximal oxygen uptake (VO2 Max) of about 80 ml of oxygen per minute per kg of body weight, they are most likely older and sedentary.
True / False

If a person is exercising at 90% of their VO2 max, there is likely large amounts of lactate in their blood from the anaerobic metabolism of glucose.
True / False

Match the following aerobic exercise intensities with the sources of ATP that are used by skeletal muscles.
A. ATP derived mostly from glycogen stored in skeletal muscle
B. ATP derived mostly from fats stored in adipose tissue
C. ATP derived from a variety of sources

26. During exercise, about 30% of the ATP that is used by a skeletal muscle ___________.
A. powers myosin B. powers Ca2+ pumps
C. powers Na+/K+ pumps D. powers K+ channels

During bursts of intense exercise in which ATP is depleted faster than it can be generated by aerobic or anaerobic metabolism, ___________________can be used by the enzyme creatine kinase 3 (CK-3) to
phosphorylate ADP, making ATP.
A. lactic acid B. phosphocreatine
C. glucose D. oxygen

28. Slow-twitch (Type I) skeletal muscle fibers ______________. More than one answer may be correct.
Indicate ALL that are correct.
A. have few capillaries
B. have many capillaries
C. have high amounts of myoglobin
D. have low amounts of myoglobin
E. have few mitochondria
F. have many mitochondria

Most postural skeletal muscles are mostly ________________ muscle fibers.
A. slow-twitch B. fast-twitch

The thigh muscles of an extreme endurance athlete are likely almost all fast-twitch fibers.
True / False

31. Different isoforms of myosin have different rates of ATP hydrolysis, which contributes to differences
in the speed of skeletal muscle contraction.
True / False

Fast-twitch skeletal muscle fibers ________________. More than one answer may be correct. Indicate ALL
that are correct.
A. have large stores of glycogen
B. are found in postural muscles
C. usually have a white tint
D. usually have a red tint
E. are slow to fatigue
F. are specialized for anaerobic metabolism
G. are specialized for aerobic metabolism

List 2 adaptations of skeletal muscle to training.
A.
B.

Resistance training (like weight lifting) increases the size of skeletal muscle fibers by increasing
_________________. Mark ALL that are correct.
A. the amount of actin protein in a cell
B. the number of sarcomeres in a cell
C. the amount of myosin protein in a cell
D. the number of cells

35. List 2 locations where smooth muscle is located.
A.
B.

How many synapses are involved in a stretch reflex of a skeletal muscle?
A. 1 B. 2 C. 3 D. 4

_____________ are specializations that cardiac muscle cells possess that help these cells contract
(relatively) simultaneously.
A. nicotinic acetylcholine receptors B. T Tubules
C. gap junctions D. all of the above

38. _____________________ return blood to the heart.
A. Arteries B. Capillaries C. Veins D. Lymphatic Vessels

All of the exchanges between blood and cells happens at which component of the cardiovascular system?
A. arteries B. veins C. the heart D. capillaries

On average, humans have about 5 liters of blood that is pumped through the body by the heart at a rate of about ______ liters/minute.
A. 100 B. 50 C. 5 D. 10

Which of the following are found in blood plasma? Multiple answers may be correct. Indicate all that are correct.
A. antibodies B. albumin C. sodium ions
D. glucose E. triglycerides F. bicarbonate ions
G. hormones

________________ ions are blood buffers.
A. K+ B. H+ C. Na+ D. HCO3-

Erythrocytes typically contain at least 1,000 mitochondria.
True / False

A single red blood cell contains about _______________.
A. 1 million mitochondria
B. 100 molecules of hemoglobin
C. 280 million molecules of hemoglobin
D. 1 nucleus

Erythropoietin (EPO) _________________. Multiple answers may be correct. Indicate ALL that are correct.
A. may be used to treat anemia
B. is produced by the pituitary gland
C. is produced by the kidneys
D. stimulates erythrocyte production in bone marrow
E. stimulates white blood cell production in lymph nodes

In an adult, red blood cells are constantly made from stem cells in the _______________.
A. skeletal muscle B. liver C. kidneys D. bone marrow

How does a erythrocyte’s shape contribute to the transport of oxygen to cells?

A single molecule of hemoglobin binds _____________ molecules of oxygen.
A. 1 B. 2 C. 3 D. 4

Name two instances that may result in anemia.
1. __________________________________ 2. _____________________________

Which type(s) of leukocyte are immune cells that are capable of phagocytosis? More than one answer may be correct. Indicate ALL that are correct.
A. Basophils B. Monocytes C. Lymphocytes
D. Platelets E. Eosinophils F. Neutrophils

51. Which type of leukocyte produces antibodies?
A. Basophils B. Monocytes C. Lymphocytes
D. Platelets E. Eosinophils F. Neutrophils

At a break in a blood vessel, _______________________ can induce vasoconstriction and also form clots.
A. Basophils B. Lymphocytes C. Platelets D. Erythrocytes

If a person with Type AB- blood receives a transfusion of Type O- blood, an agglutination reaction is likely to occur.
True / False

The heart's _____________ pumps oxygen-poor blood into pulmonary circulation out to the lungs.
A. right atria B. right ventricle
C. left atria D. left ventricle

The __________ of the heart receives oxygen-poor blood from systemic circulation, via the superior and inferior vena cava.
A. right atrium B. right ventricle
C. left atrium D. left ventricle

The muscular wall of the left ventricle is typically the thickest of the 4 chambers.
T/ F

Cordae tendinae normally prevent the prolapse of the human heart’s mitral valve. If they lengthen, blood may flow back into the left atrium as the left ventricle contracts.
True / False

The heart valves at the ventricular exits are the _________________ valves. Circle ALL that are correct.
A. pulmonary semilunar B. mitral C. tricuspid D aortic semilunar

____________is the phase of cardiac contraction.
A. systole B. diastole

During the cardiac cycle at a heart rate of 75 bpm, systole lasts about 0.3 seconds and diastole lasts about ______ seconds.
A. 0.3 seconds B. 0.5 seconds C. 1.5 seconds D. 3 seconds

During the ____________ phase of the cardiac cycle, the pressure in the left ventricle rises above that in the aorta, opening the semilunar valve.
A. isovolumetric relaxation B. ejection
C. rapid filling D. isovolumetric contraction

The ventricular stroke-volume is always 100% of the total volume in that ventricle.
T / F

During the ___________ phase of the cardiac cycle, both the atrioventricular valve and the aortic semilunar valve are closed.
A. ejection B. isovolumetric relaxation
C. rapid filling D. all of the above

The heart's primary pacemaker is located in the _________________.
A. right atrium B. left atrium
C. right ventricle D. left ventricle

The autorhythmic pacemaker potentials in the cells of the SA Node of the heart are due to
_________________.
A. the opening of voltage-gated potassium channels
B. the opening of voltage-gated calcium channels
C. the opening of HCN sodium channels, which open in response to hyperpolarization
D. the opening of acetylcholine receptors

The binding of ___________________ to its receptor on pacemaker cells of the SA Node opens HCN sodium channels, increasing the heart rate.
A. Acetylcholine B. Nicotine
C. Norepinephrine D. Serotonin

The binding of ______________ to its receptor on pacemaker cells of the SA node opens potassium channels, slowing the rate of pacemaker potentials and the heart beat. More than one answer may be
correct. Indicate ALL that are correct.
A. norepinephrine B. nicotine (a toxin found in some plants)
C. epinephrine
D.muscarine (a toxin found in some mushrooms)
E. acetylcholine

“Rest and Digest” functions of the autonomic nervous system are regulated by the __________________
division.
A. sympathetic B. ganglionic C. parasympathetic D. none of the above

The action potentials of a cardiac muscle cell have a slow plateau phase due to the _________________.
A. influx of K+ B. influx of Ca2+
C. influx of Na+ D. efflux of K+

Which structure of the heart transmits action potentials to the outer walls of the 2 ventricles?
A. Bundle of His B. AV node C. Purkinje Fibers D. SA node

All four chambers of the heart contract simultaneously.
T / F

In an ECG (electrocardiogram) the __________ wave represents
ventricular repolarization.
A. P B. QRS C. T

An ECG is a DIRECT representation of the action potentials in cardiac muscle cells.
T / F

__________________ protect(s) arteries from plaque formation and atherosclerosis. More than one answer may be correct.
A. Drinking a lot B. Exercise
C. Smoking D. High-density lipoproteins
E. Diabetes F. avocados G. bacon

The accumulation of ______________________, due to decreased coronary blood/oxygen supply, can cause
Angina pectoris.
A. lactic acid B. glycogen C. ATP D. glucose

______________ are life-saving devices that stimulate action potentials in cardiac muscle cells all at once.
The cells enter a refractory state, allowing the SA Node to ‘reset’ the cells into coordinated
contractions.
A. Centrifuges B. Electrocardiograms
C. MRI machines D. Electric Defibrillators

If a person has a heart rate of 65 beats per minute and their heart has a stroke volume of 90
milliliters per beat, what is their cardiac output?
____________________________ (Be sure to include the correct units.)

Which circulation has higher blood flow, lower resistance, and lower pressure?
A. systemic circulation B. pulmonary circulation

When a well-trained elite endurance athlete wakes up in the morning, their resting heart rate is low
(say 35 bpm). This is due to ______________ that accompanies training.
A. increases in sympathetic nerve activity
B. increases in Vagus nerve (cranial nerve X) activity
C. decreases in sympathetic nerve activity
D. decreases in Vagus nerve (cranial nerve X) activity

The region of the brain that controls the heart rate, via autonomic innervation, is found in the
________________.
A. pre-central gyrus of the cortex B. medulla oblongata
C. occipital lobe of the cortex D. thalamus

Imagine a patient has a cardiac stroke volume of 75 ml per beat. INCREASES in which of the
following variables would INCREASE the patient's stroke volume. More than one answer may be
correct. Indicate ALL that are correct.
A. the total peripheral resistance
B. the strength of ventricular contraction
C. the EDV (end-diastolic volume)
D. Parasympathetic nerve activity

82. In a cardiac muscle cell, increases in __________ increase the strength of muscle cell contraction.
Multiple answers may be correct. Indicate all that are correct.
A. intracellular calcium
B. Vagus nerve stimulation
C. . sympathetic nerve stimulation
D. sarcomere stretch due to increases in End-Diastolic Volume

Liver damage can lead to edema, since it produces most of the blood plasma proteins (like albumin)
that generate colloid osmotic pressure within blood vessels.
True / False

_____________ is a hormone that is a strong vasoconstrictor that increases blood pressure in response
to pressure drops.
A. Angiotensin-converting enzyme (ACE) B. Angiotensin II
C. Aldosterone

Increasing the radius of a small artery by 3-fold (through vasodialation) would decrease the blood flowing through it __________.
A. 9-fold B. 3-fold
C. 81-fold D. 27-fold

At rest, our skeletal muscles are the organs with the highest blood flow.
True / False

At rest, the brain receives about ___________________ of the body’s total blood flow.
A. 0.5% B. 13% C. 21% D. 75%

_____________released by sympathetic nerves causes vasoconstriction of arterioles in the intestines, shunting blood to other organs.
A. Acetylcholine B. Glucose
C. Dopamine D. Norepinephrine

The _________________ layer of a blood vessel contains smooth muscle that can be signaled to contract.
A. inner (tunica intima) B. middle (tunica media) C. outer (tunica externa)

Nitric oxide and histamine are both paracrine signaling molecules that promote vasodilation of blood vessels.
True / False

During heavy exercise, about ______________ of the body’s total blood flow is diverted to skeletal muscles.
A. 20% B. 45% C. 85% D. 100%

During exercise, _______________. More than one answer may be correct.
A. increased sympathetic nerve stimulation increases the heart's stroke volume
B. increased Vagus nerve stimulation increases heart rate
C. increased sympathetic nerve stimulation increases the heart rate
D. decreased Vagus nerve stimulation increases the heart rate

When a nurse manually checks a patient's blood pressure, the systolic pressure is indicated by
______________.
A. the sound of heart valves closing
B. the 1st Korotkoff sounds
C. the last Korotkoff sounds
D. the sound of heart valves opening

Increases in sympathetic stimulation of blood vessels is one cause of high blood pressure.
True / False

Anaphylaxis occurs when widespread vasodilation causes a drop in blood pressure due to the effects of ___________________.
A. norepinephrine B. angiotensin converting enzyme
C. serotonin D. histamine.

All microbes are pathogens.
True / False

In terms of innate immunity, how are the skin and the stomach similar?

98. Diapedesis aids in fighting off infection ___________________.
A. by increasing the production of antibodies
B. by increasing body temperature
C. by allowing phagocytic cells to leave the blood and enter an infected tissue
D. all of the above

All fevers are harmful.
T / F

Transferring the serum from an immunized person to a second person transfers adaptive immunity.
A. True B. False

____________ are responsible for cell-mediated immunity.
A. T lymphocytes B. B lymphocytes
C. Erythrocytes D. Monocytes

Specific antibodies bind to specific antigens present on pathogens.
True / False

Antibodies are made up of ___________________.
A. 1 heavy chain and 2 light chains
B. 2 heavy chains and 2 light chains
C. 2 heavy chains and 1light chain
D. 2 heavy chains and 3 light chains

Humans are born with ~100 trillion antibodies.
T / F

Define opsinization.

____________ are cells of the immune system that secrete enzymes which trigger programmed
cell death (apoptosis).
A. B lymphocytes B. Helper T lymphocytes
C. Killer T lymphocytes D. Neutrophils

During the primary exposure to an antigen, antibodies specific for that antigen are
detectable in the blood after about ______________.
A. 1-10 minutes B. 2 hours
C. 5-10 days D. 20-30 days

Genetically-identical Memory B lymphocytes are found in ______________.
A. the kidneys B. lymph nodes and the spleen
C. the brain D. the heart

During a secondary immune response, a person may not develop symptoms caused by the
exposure to a pathogen.
T / F

Match the following modern vaccines with their descriptions.
Viral Vector __________ A. Original Pfizer and Moderna Covid-19 vaccines
mRNA _________ B. Zika virus vaccine
Toxoid _________ D. Tetanus vaccine
Live attenuated _________ E. Chickenpox vaccine

Match the following autoimmune diseases with their cause.
Myasthenia Gravis ______________
Type I diabetes _____________
Rheumatoid arthritis ___________
A. helper T cells recognize pancreatic beta cells as foreign
B. antibodies develop against acetylcholine receptors
C. IgG antibodies are recognized by IgM antibodies as foreign

Why is a new flu vaccination necessary every season?

Immediate hypersensitivity allergies ________________. Mark ALL that are correct.
A. involve the stimulation of Mast cells to release histamine
B. can cause the constriction of lung bronchioles
C. are due to an 'overactive' immune response to a normally harmless antigen
D. have symptoms that develop over seconds or minutes
E. have symptoms that develop over hours or days

Spike proteins on SARS-CoV-2 aid infection of human cells by binding to _________________.
A. voltage-gated Ca2+ channels
B. angiotensin converting enzyme 2 receptors
C. nicotinic acetylcholine receptors
D. none of the above

Antihistamines are a good treatment for BOTH immediate- and delayed-hypersensitivity
allergies.
T / F