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PHSL mid sem TEST BANK

The first step of haemostasis is:

The formation of a blood clot.

The formation of a fibrin clot.

The formation of a platelet plug.

Vascular spasm.

Secretion of histamine.

Which ONE of the following statements about human lymphocytes is INCORRECT?

Lymphocytes have a single large non-segmented nucleus.

Lymphocytes are derived from committed lymphoid stem cells.

Lymphocytes make up about 30% of leucocytes.

Leukaemia is a condition resulting from the uncontrolled production of white blood cells.

Lymphocytes are the largest of all the white blood cells in humans.

Which ONE of the following is likely to cause a significant transfusion reaction, assuming this is the first transfusion for all recipients?

A person who is blood group O positive donates to a person who is blood group B negative.

A person who is blood group A negative donates to a person who is blood group A positive.

A person who is blood group B positive donates to a person who is blood group AB positive.

A person who is blood group O positive donates to a person who is blood group AB positive.

A person who is blood group AB positive donates to a person who is blood group A positive.

Which ONE of the following statements about haemostasis is CORRECT?

The extrinsic pathway is initiated by the release of factor III from damaged tissue to complex with factor VII and V.

The formation of a platelet plug is inhibited by healthy endothelium through the release of ADP.

The intrinsic pathway is initiated by the activation of factor X.

Prothrombin is the enzyme that catalyses the conversion of fibrinogen into long fibrin fibres.

Thromboxane A2 is released by damaged vessel walls to initiate vasoconstriction.

With regard to the transmitters and receptors employed in the autonomic nervous system:

Nicotinic acetylcholine receptors are G-protein coupled.

Noradrenaline acts on α receptors.

Acetylcholine acts on β receptors.

α receptors are ionotropic.

Adrenaline acts on muscarinic receptors.

The human erythrocyte:

Develops from a committed myeloid stem cell.

Has a diameter of about 15 micrometres.

Uses the enzyme carbonic anhydrase to catalyse the reaction between carbon and oxygen.

Contains 75% haemoglobin.

Lives on average for 280 days.

Which ONE of the following statements about the autonomic nervous system is CORRECT?

Areas related to autonomic function in the brainstem regulate cardiovascular and respiratory function.

The autonomic nervous system operates without afferent input.

There are no synapses in the sympathetic ganglion chain.

The spinal cord integrates emotional and motivational signals with autonomic signals.

The autonomic nervous system lies outside the central nervous system.

Which ONE of the following organs does the autonomic nervous system NOT exert control over?

Bronchial muscle (airways)

Sweat glands

Iris muscle (pupil)

Skeletal muscle

Heart muscle

Which ONE of the following statements about iron metabolism in humans is INCORRECT?

If the supply of iron in the diet falls, stored iron is released from ferritin.

Phosphates form insoluble compounds with ingested iron hindering iron absorption.

Free iron will bind with apotransferrin to form transferrin, which can then be transported in the blood.

Vitamin C can increase iron absorption by oxidising ferrous ions to ferric ions.

Only about 10% of ingested iron is absorbed into the body each day.

Which ONE of the following statements is INCORRECT? Neutrophils:

Make up the majority of white blood cells.

Are derived from committed myeloid cells in the bone marrow.

Are chemotaxic.

Generally have single large non-segmented nuclei.

Are one type of granulocyte.

The autonomic nervous system has a hierarchy of levels of reflex control. Which answer CORRECTLY orders these reflex loops from low level to high level?

Spinal cord, brainstem, ganglion, hypothalamus.

Brainstem, spinal cord, hypothalamus, ganglion.

Spinal cord, ganglion, hypothalamus, brainstem.

Ganglion, spinal cord, hypothalamus, brainstem.

Ganglion, spinal cord, brainstem, hypothalamus.

In healthy endothelial cells, arachidonic acid is converted to --------- which ---------- formation of blood clots.

Thromboxane A2: stimulates

Nitric oxide: inhibits

Thromboxane A2: inhibits

Prostacyclin: stimulates

Prostacyclin: inhibits

Which ONE of the following statements about haemostasis is CORRECT?

Thromboxane A2 is released by damaged vessel walls to initiate vasoconstriction.

Calcium ions are required for several steps of the prothrombin activation cascade.

Immediately after a blood vessel is cut or ruptured the wall of the vessel dilates.

Prothrombin activator catalyses the conversion of fibrinogen into long fibrin fibres.

Vitamin D is important for the production of five important clotting factors, including prothrombin.

The parasympathetic system has neurons that:

Cause decreased gut motility.

Cause an increase in heart rate.

Originate in the middle levels of the spinal cord.

Use adrenaline as a neurotransmitter.

Have short post-ganglionic axons.

Which type of leukocyte defends against parasitic infections?

Erythrocytes

Neutrophils

Eosinophils

Monocytes

Lymphocytes

The primary neurotransmitter used by both sympathetic and parasympathetic axons is:

Noradrenaline at pre-ganglionic synapses.

Adrenaline at pre-ganglionic synapses.

Adrenaline at post-ganglionic synapses.

Acetylcholine at post-ganglionic synapses.

Acetylcholine at pre-ganglionic synapses.

Which ONE of the following statements about erythropoietin is CORRECT?

Testosterone reduces the basal rate of erythropoiesis.

Increased levels of erythropoietin result in increased circulating levels of red blood cells within 24 hours.

Hypoxia causes a marked decrease in erythropoietin levels.

Erythropoietin is a hormone produced only in the liver.

Erythropoietin stimulates the production of proerythroblasts from the bone marrow.

Choose the list of terms from the autonomic nervous system that best matches the following descriptors: (1) has cell bodies located in a chain outside the spinal cord; (2) has cell bodies in the central nervous system; (3) has nicotinic acetylcholine receptors; (4) is dominant during rest

Post-ganglionic, pre-ganglionic, parasympathetic, sympathetic

Post-ganglionic, pre-ganglionic, sympathetic, parasympathetic

Pre-ganglionic, post-ganglionic, sympathetic, parasympathetic

Parasympathetic, sympathetic, post-ganglionic, pre-ganglionic

Sympathetic, pre-ganglionic, post-ganglionic, parasympathetic

Pernicious anaemia is associated with which ONE of the following?

Damage to the bone marrow

Bleeding

Inadequate bilirubin levels

Insufficient Vitamin B12

This is correct. Pernicious anaemia is a result of inadequate absorption of vitamin B12.

Which ONE of the following triggers erythropoietin release?

Increased blood CO2 levels

Damage to a blood vessel wall and subsequent exposure to collagen

Decreased blood oxygen levels

Infection in the tissues

Infection in the blood

Which ONE of the following statements about haemoglobin is INCORRECT?

Haemoglobin is an excellent acid-base buffer because the iron binds bicarbonate.

The human erythrocyte contains haemoglobin, a respiratory pigment based on the iron atom.

Haemoglobin from erythrocytes that have been removed from the circulation is degraded into bilirubin and other compounds.

Males have a haemoglobin concentration of around 16 g per 100 ml of whole blood and females around 14 g per 100 ml of whole blood.

Each of the subunits of the haemoglobin molecule contains a haem group that is necessary for the binding of oxygen.

The main site of haematopoiesis in the fetus from the second to the seventh month is the:

Liver

Yolk sac

Kidney

Bone marrow

Spleen

Which ONE of the following is NOT part of the sequence of skeletal muscle contraction?

An action potential in the surface membrane.

E-C coupling.

An action potential conducted down the t-tubules.

Increase in the sarcoplasmic concentration of Ca2+.

The sarcoplasmic reticulum is responsible for Ca2+ uptake.

An increase in the intracellular concentration of which ion/s is/are responsible for initiating muscle contraction?

Na+

K+

Ca2+

Na+ & Ca2+

Ca2+ & K+

Cardiac and smooth muscle differ from skeletal muscle in that:

They DO NOT require an influx of Ca2+ from the extracellular fluid to initiate contraction.

Each individual muscle cell has its own nerve supply.

They contract more quickly.

The individual muscle cells are electrically coupled.

They are under voluntary control.

Which ONE of the following statements regarding the internal structure of a skeletal muscle fibre is TRUE?

In adult humans a large muscle fibre (one cell) contains around 20 myofibrils.

The main elastic (spring) component within the sarcomere is the endomysium.

Each sarcomere has two t-tubules located at the junctions of the A/I band.

Absence of desmin results in the skeletal muscle disease Duchenne Muscular Dystrophy.

Within each fast twitch muscle fibre each myofibril is enveloped by sarcolemma membrane.

Which ONE of the following is NOT a difference in the cytomembrane of cardiac vs skeletal muscle?

The sarcoplasmic reticulum of cardiac muscle is more extensive than that of skeletal muscle.

T tubules are found at the level of the Z disk in cardiac muscle, and are substantially larger than those of skeletal muscle found at the A-I junction.

The sarcoplasmic reticulum of cardiac muscle is not as extensive as that of skeletal muscle.

Diads are typical in cardiocytes, while triads are typical in skeletal muscle.

Mitochondria are more abundant in cardiac muscle than in skeletal muscle and contain numerous cristae.

Which ONE of the following bands does not change in length when a skeletal muscle fibre contracts isotonically?

In general, human muscles are made up of approximately a 50:50 mixture of fast and slow fibres. Can the exceptional abilities of elite high jumpers (power athletes) and marathon runners be explained by having predominantly fast or slow muscle fibre types in key muscles? Choose the statement which gives the MOST WIDELY accepted explanation.

Yes, in fact these elite athletes were born with muscles which are all fast-fibres, such as high jumpers, or all slow fibres, such as marathon runners.

Yes, at elite levels like the Olympics, it appears that power and endurance athletes are born and not made, with high jumpers having a higher than 50% fast-fibre profile and marathon runners having a higher than 50% slow-fibre profile.

No, there is little individual variation in fibre type proportions.

The question cannot be answered because currently exercise scientists cannot measure the fibre type ratios in living athletes.

No, it is the high density of mitochondria present in both power and endurance athletes which determines their elite performance characteristics.

If you calculate the time it would take for extracellular Ca2+ to diffuse to the middle of a skeletal muscle fibre, the fastest predicted rate for onset of contraction would be in the order of 100 msec after the arrival of the motor neuron action potential. Why then is it possible for a muscle fibre to start contracting only 10 msec after the arrival of the motor nerve action potential?

The rate of onset of muscle contraction is dependent on the diffusion of intracellular ATP and not the diffusion of Ca2+.

The concentration difference between intracellular Ca2+ stored in the sarcoplasmic reticulum and sarcoplasmic [Ca2+] is so small (approx 1 to 1.5) that ATP powered Ca2+ pumps are required to move Ca2+ out to activate the contractile proteins.

Membrane invaginations (t-tubular system) carry the action potential into the middle of the muscle fibre triggering a global release of Ca2+ from the intracellular Ca2+ store.

The concentration difference between intracellular and extracellular Ca2+ is so large (about 1 to 20,000) that the Ca2+ diffuses much more rapidly than expected.

This is possible because Ca2+ is released from mitochondrial stores close to the contractile proteins.

Which ONE of the following is NOT a feature of smooth muscle contraction?

The regulation of the actin-myosin interaction occurs by calcium binding to troponin.

An increase in cytosolic calcium induces calmodulin binding to myosin-light chain kinase.

Smooth muscle myosin is a type II myosin, consisting of two heavy chains and two pairs of light chains. The myosin molecule is folded when dephosphorylated.

When type II myosin phosphorylates, it unfolds and assembles into filaments, the actin binding site on the myosin head is exposed, and myosin can then bind to actin filaments to cause cell contraction.

Phosphorylation of the myosin light chain converts the myosin into its active form which can then bind to f-actin.

The correct nomenclature of the connective tissue sheaths in skeletal muscle is:

Whole muscle is surrounded by the PERIMYSIUM, fascicles by the EPIMYSIUM and individual fibres by the ENDOMYSIUM.

Whole muscle is surrounded by the TENDOPIMYSIUM, fascicles by the PERIMYSIUM and individual fibres by the ENDOMYSIUM.

Whole muscle is surrounded by the ENDOMYSIUM, fascicles by the PERIMYSIUM and individual fibres by the EPIMYSIUM.

Whole muscle is surrounded by the EPIMYSIUM, fascicles by the ENDOMYSIUM and individual fibres by the PERIMYSIUM.

Whole muscle is surrounded by the EPIMYSIUM, fascicles by the PERIMYSIUM and individual fibres by the ENDOMYSIUM.

Which ONE of the following statements is CORRECT of an isometric tetanic contraction?

The muscle shortens under a fixed load.

The muscle shortens but does not generate tension.

The muscle contracts at its maximum velocity of shortening.

The set length of the muscle determines the level of tension developed.

The shortening is isokinetic.

Which ONE of the following statements regarding the sliding filament theory of muscle contraction is CORRECT?

The cross-bridges are activated once during a contraction.

Sliding is caused by the cross-bridges on the myosin molecule interacting with specific sites on the actin molecule.

Every cycle four molecules of ATP are used by each myosin head.

The cross-bridges have an unlimited range of movement.

Every cycle two molecules of ATP are used by each myosin head.

Despite the fact that the same amount of activating [Ca2+]in is released in each case, the size of a single skeletal muscle twitch is about 4 times smaller than a fused tetanus. Why is this?

Because the amplitude of the action potentials coming from the motor neuron are larger during a tetanus.

Because rate of diffusion of Ca2+ molecules from the sarcoplasmic reticulum to the contractile proteins is slower during a single twitch.

Because in a twitch (which occurs when muscle is activated by a single action potential) there is not enough time to take up all the elastic tension before the muscle starts to relax again.

Because the CaATPase pumps on the sarcoplasmic reticulum work faster during a single twitch, lowering the [Ca2+]in more quickly, than in the case of the larger tetanus.

Because the myosin heads, the molecular motor, move more slowly during a twitch.

What determines whether a skeletal muscle fibre is fast or slow?

The elasticity of the endomysium.

The number of mitochondria within the fibre.

The different numbers of t-tubules present per sarcomere.

The speed of the myosin ATPase.

The organization of the nuclei in relation to the myofibrils.

Skeletal muscle can be modeled as contractile proteins connected to the skeleton by in series and in parallel elastic components. Which of the following make up the protein component of the elastic capability of skeletal muscle?

Troponin and Tropomyosin.

Dystrophin, Desmin, αβ-Crystalin.

Sarcolemma, t-tubules, Sarcoplasmic Reticulum.

Actin and Myosin.

Titin, tendons and Alpha-actinin.

Which ONE of the following statements regarding the sliding filament theory of muscle contraction is FALSE?

During the cross bridge cycle the myosin heads are activated cyclically about 4 times per second.

During sliding the A band shortens.

Muscle works by the relative sliding of the thin filament (actin) over the thick filament (myosin).

The myosin heads have a limited range of movement of about 10nm.

Sliding is caused by the myosin heads interacting with specific sites on the actin molecule.

During an isotonic contraction in skeletal muscle the I band shortens while the A band does not change in length. What are the proteins which comprise the I band and A band?

Actin and Myosin

Myosin and Titin

Actin and α-actinin

Nebulin and Myosin

Desmin and Nebulin

Which ONE of the following statements about smooth muscle is CORRECT?

Calcium-dependent phosphorylation of myosin regulatory light chains is responsible for the contraction of smooth muscle.

Smooth muscle cells are multi-nucleated like cardiac and skeletal muscle cells.

Smooth muscle cells are not electrically coupled to each other.

Smooth muscle can only be stimulated to contract by the CNS.

In smooth muscle, actin filaments and associated myosin attach to regular Z lines producing a striation pattern.

When skeletal muscle shortens, the I band contracts while the A band does not change in length. The explanation for this is:

The thick myosin filament moves over the thin actin filament.

The actin and myosin filaments are both moving.

The titin molecule pulls the actin filaments towards the Z-line.

Dystrophin pulls the myosin filament towards the Z-line.

The actin filament moves along the fixed myosin filament.

What are the two major factors which make a muscle fibre “fast-twitch” or “slow-twitch”?

The elastic modulus of the muscle proteins titan and desmin. e.g. Fast or slow titan and desmin.

The type of actin and nebulin expressed.

The density of calcium channels present in the sarcolemma and the arrangement of the t-tubular system with respect to the individual fibrils in a fibre.

The amount of glycogen and ATP.

The rate at which myosin can hydrolyse ATP and the arrangement of the internal calcium store (Sarcoplasmic Reticulum) with respect to individual (myo) fibrils in a fibre.

Choose the MOST CORRECT option. With regard to the ion channels underlying the action potential in a typical nerve axon:

Voltage-dependent K+ channels are open during the repolarization phase.

The voltage-dependent Na+ channels are inactivated when the action potential threshold is reached.

Background or “leak” K+ channels are closed during the depolarization phase.

Voltage-dependent K+ channels are closed during the afterhyperpolarization phase.

Voltage-dependent K+ channels activate before the voltage-dependent Na+ channels.

Which ONE of the following statements about ion channels is INCORRECT?

Ion channels can be opened either directly or indirectly by neurotransmitters.

Ion channels may be opened by stretch of the cell membrane.

Ion channels have gates that may be opened by intracellular ligands.

Ion channels allow transport of an ion against its chemical gradient, if the electrical driving force is sufficient.

Ion channels allow transport of an ion against its electrochemical gradient.

Which ONE of the following statements regarding membrane transport processes is CORRECT?

The Ca2+/Na+ exchanger (counter-transporter) that couples Ca2+ efflux with Na+ influx, directly utilizes ATP as an energy source.

The hormone insulin is released from pancreatic beta-cells into the bloodstream by endocytosis.

The Na+/K+/ATPase is an example of a secondary active transporter.

The SGLT protein that couples Na+ influx with the movement of glucose into cells against its concentration gradient is an example of a facilitated diffusion protein.

A K+ ion can only move through an ion channel in a direction that is down its electrochemical gradient.

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