Exam 3 Human Physiology Pearson Questions

Chapter 12: Autonomic Nervous SystemChapter 13: Skeletal Muscle and Integration

Which of the following is an example of antagonistic control?

Parasympathetic stimulation causes bronchoconstriction, while sympathetic stimulation causes bronchodilation.

Which of the following characteristics is similar between the sympathetic and parasympathetic branches for most neurons?

The same neurotransmitter is secreted from the sympathetic and parasympathetic preganglionic neurons.

Preganglionic Neurotransmitter: Both symp and parasym preganglionic neurons utilize acetylcholine (ACh) as neurotransmitter. ACh binds to nicotinic receptors on dendrites of postganglionic neurons in the ganglia.

Which is the main enzyme responsible for the breakdown of catecholamines?

Monoamine oxidase

Which adrenergic receptor subtype has the greatest sensitivity for epinephrine?

β₂

β2-adrenergic receptors: Exhibit the highest affinity and potency for epinephrine; triggering physiological responses like bronchodilation and vasodilation at low, baseline concentrations.

β1-adrenergic receptors: Equal sensitivity to both epinephrine and norepinephrine, influence cardiac rate & contractility.

β3-adrenergic receptors: In adipose tissue & respond to catecholamines, w/ norepinephrine higher potency than epinephrine depending on context.

α1-adrenergic receptors: Req higher (pharmacological) [epinephrine] to become strongly activated compared to beta receptors.

Which of the following is a modified sympathetic ganglion?

Adrenal medulla

Adrenal medulla: Acts as modified symp ganglion where pregang symp fibers synapse directly onto chromaffin cells, which release epinephrine & norepinephrine into bloodstream as hormones.

Varicosities: Swellings along autonomic axon branches that store & release neurotransmitters over a broad area.

Vagus nerve: Major cranial nerve that carries parasympathetic fibers.

Adrenal cortex: Outer region of adrenal gland that produces steroid hormones (like cortisol and aldosterone).

A patient is prescribed a muscarinic antagonist. This will inhibit signaling from which neurons?

Postganglionic parasympathetic

Muscarinic receptors — type of cholinergic receptor on target organs & tissues of PNS, where respond to neurotransmitter Ach.

Postganglionic parasympathetic — fibers release Ach to bind w/ muscarinic receptors on effector organs.

Blocking these receptors w/ antagonist disrupts parasympathetic signaling = increased heart rate, reduced secretions, & pupil dilation.

Neurons in the parasympathetic pathway use which of the following neurotransmitters?

Acetylcholine

both preganglionic and postganglionic neurons use ACh as neurotransmitter:

1. Preganglionic neurons release Ach, which binds to nicotinic receptors on postganglionic neuron.

2. Postganglionic neurons release Ach, which binds to muscarinic receptors on target organ tissue to stimulate "rest and digest" .

Sympathetic pathways originate in which regions of the spinal cord?

Thoracic and lumbar

A patient was exposed to a nerve gas during a chemical warfare attack. The nerve gas inhibited the enzyme acetylcholinesterase. What will happen to the amount of acetylcholine in the synaptic cleft, and how can this be treated?

The amount of Ach will increase; treat w/ a cholinergic receptor antagonist.

• Acetylcholinesterase break down Ach in synaptic cleft.

• When nerve gas inhibits this enzyme, Ach cannot be broken down & instead accumulates/increases in synaptic cleft.

• Excess Ach leads to continuous, overstim of cholinergic receptors.

• Treatment = cholinergic receptor antagonist to block receptors & stop excessive stimulation.

Which of the following is the smallest structure?

• Myosin

• Myofibril

• Muscle fiber

• Muscle fascicle

Myosin

1. Muscle fascicle: Bundle of multiple individual muscle cells (muscle fibers).

2. Muscle fiber: Single, long muscle cell.

3. Myofibril: Specialized, cylindrical organelle packed inside muscle fiber; contains contractile mechanics.

4. Myosin: Microscopic motor protein molecule that aggregates to form thick "myofilaments" w/in myofibril.

Which of the following would NOT change size during a muscle contraction?

• H zone

• A band

• Sarcomere

• I band

A band

A band: Entire length of thick (myosin) filaments. Cuz physical length of myosin filaments stays exactly same during contraction, total width remains constant

Sarcomere: B asic unit of muscle contraction bounded by Z-lines, the entire sarcomere shortens as the lines are pulled closer together.

H zone: Central region of A band w/ only thick filaments. As actin filaments slide into this central zone, region of thick-filament-only space shrinks or disappears.

I band: Has s only thin filaments. As muscle contracts & filaments overlap more heavily, the I band shortens significantly

Which ion stimulates shape changes at the beginning of skeletal muscle contraction?

Ca²⁺

Calcium Release: Action potential travels down T-tubules and causes calcium ions released from SR into sarcoplasm.

Binding to Troponin: Ca2+ bind to regulatory protein troponin on thin (actin) filaments.

Conformational Change: binding causes troponin to change shape, which shifts tropomyosin away from myosin-binding sites on actin.

Cross-Bridge Formation: With binding sites exposed, myosin heads can attach to actin to begin the contraction cycle

__________ occurs when myosin crossbridges attach to actin filaments and pull them toward the middle of the sarcomere.

A power stroke

What happens when calcium binds to troponin?

Troponin changes conformation and pulls Tropomyosin away from the myosin-binding site on actin.

• Shape Change: Calcium binds to the troponin complex = conformation

• Exposing Site: This shift moves tropomyosin out of way, uncovering myosin-binding sites on actin filament.

• Cross-Bridge Formation: exposed, myosin heads attach to actin & begin muscle contraction cycle.

What is the immediate function of ATP during skeletal muscle contraction?

Resetting myosin heads by detaching them from actin and returning them to their high-energy state.

1. Detachment: ATP binds directly to myosin head = myosin head r detach from the actin filament.

2. Resetting (Cocking): Detached, ATP is hydrolyzed (broken down) into ADP & inorganic phosphate (Pi). Energy released resets/"cocks" myosin head back into high-energy state, ready for next power stroke.

Which of the following best describes the progression of muscle contraction as the frequency of stimulation increases?

Twitch > Summation > Incomplete tetanus > Complete tetanus.

Because of their shape, muscle cells are also known as __________.

muscle fibers

• Muscle fibers: Skeletal & cardiac muscle cells.

• Myofibrils: Rod-like, internal contractile organelles packed inside the muscle cell.

• Tubules: Tiny tube-like of cell membrane to transmit electrical signals.

• Fascicles: Bundles w/ multiple muscle fibers grouped together by connective tissue.

Which happens when a myofibril contracts?

Thin and thick filaments slide past each other, but do not change in length.

Which of the following is proportional to the amount of tension produced by a skeletal muscle?

the number of motor units activated.

Amount of tension a skeletal muscle produces is directly related to motor unit recruitment.

• A motor unit made up of a single motor neuron & all muscle fibers it innervates.

• When your body needs to generate more force/tension, nervous syst activates (recruits) a greater # of motor units.

• More active motor units = more muscle fibers contracting simultaneously, = stronger overall muscle tension.

NO force is generated during which of the following?

latent period

A single muscle twitch has 3 distinct phases:

1. Latent Period: Time lag btwn arrival of the nerve's electrical signal (action potential) & start of actual physical contraction. Muscle is busy resetting internally—releasing Ca2+ from SR into cell. Actin and Myosin cross-bridges havn’t started pulling yet, zero force/tension is recorded.

2. The Contraction Phase: Ca2+ binds to muscle fibers, cross-bridges form, & muscle actively shortens, generating a rapid rise in force to its peak tension.

3. The Relaxation Phase: Ca2+ pumped away, muscle stops pulling, & tension slides down twrd resting lvls. Active force gen drops off, but muscle still recovering frm peak tension built during contraction.

Cuz muscle twitch encompasses all 3 phases combined, force is generated during parts of it, leaving latent period as only duration where force is completely absent

What is the minimum voltage needed to generate active force in the skeletal muscle?

threshold voltage

A motor unit is defined as _______.

the axon terminals of a single motor neuron and all of the muscle fibers that it stimulates

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?

Acetylcholine is degraded by acetylcholinesterase.

Acetylcholinesterase is an enzyme that degrades acetylcholine. This degradation results in a rapid cessation of Ach signal & swift removal from cleft.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?

Acetylcholine is released by axon terminals of the motor neuron.

Acetylcholine is released into the synaptic cleft via exocytosis.

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Cell bodies of motor neurons to muscles in head and neck are in the brain. Cell bodies of motor neurons to rest of muscles are in spinal cord.

Calcium entry into the axon terminal triggers which of the following events?

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

Acetylcholine binds to its receptor in the sarcolemma and triggers __________.

Opening of ligand-gated cation channels

permit sodium ions to diffuse inward and potassium ions to diffuse outward.

Influx of + ions localizes a depolarization (end-plate potential) & triggers voltage-gated channels further down membrane to fire full muscle action potential.

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?

Inside surface of sarcolemma is negatively charged compared to outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

Sodium : Both gradients work together. chemical gradient drives Na inward (high outside to low inside), and electrical gradient also pulls Na inward cuz inside cell is negatively charged relative to outside. Double favorable force causes a massive influx of Na.

Potassium: Gradients oppose each other. Chemical gradient drives K outward (high inside to low outside), but negative charge inside cell pulls the positive K back inward.

Sodium driven by both forces while potassium's exit is resisted by the negative membrane potential, far more sodium ions rush into cell than potassium ions leave = local depolarization

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

A myosin head bound to actin

As soon as the activated myosin head forms a cross bridge with actin, the power stroke begins.

What structure is the functional unit of contraction in a skeletal muscle fiber?

sarcomere

A sarcomere is a regular arrangement of thin and thick myofilaments that extends from one Z disc to the next. A myofibril consists of a series of sarcomeres.

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?

Calcium ions are stored in the sarcoplasmic reticulum.

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

ATP binds to the myosin head.

Binding of ATP to myosin head weakens bond btwn myosin & actin, forcing myosin head to detach. ATP provides energy for next power stroke.

How does the myosin head obtain the energy required for activation?

The energy comes from the hydrolysis of ATP.

Myosin is a protein w/ binding site for actin & has ATPase. Energy released during hydrolysis of ATP activates myosin head.

What specific event triggers the uncovering of the myosin binding site on actin?

Calcium ions bind to troponin and change its shape.

Binding shifts tropomyosin away from the myosin binding sites on actin.

When does cross bridge cycling end?

Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

Sarcoplasmic reticulum has Ca²⁺-ATPases that transport Ca²⁺ into SR. w/o Ca²⁺, troponin returns to its resting shape, & tropomyosin glides over & covers myosin binding sites on actin.

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

arrival of an action potential

Action potential in the T tubule causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum.

The binding of calcium to which molecule causes the myosin binding sites to be exposed?

troponin

calcium binds to troponin, troponin releases tropomyosin, exposing the myosin binding sites.

A myosin head binds to which molecule to form a cross bridge?

Actin

Myosin head binds to actin, the major component of thin filaments.

What causes the myosin head to disconnect from actin?

Binding of ATP

Binding of ATP (Detachment):

Hydrolysis of ATP (Cocking): Into ADP and an inorganic phosphate . Energy released "cocks" the myosin head back into high-energy, ready position.

Binding of Calcium to Troponin (Regulation): Shift tropomyosin to exposes binding sites

What causes the power stroke?

release of ADP and Pi

hydrolysis of ATP provides the energy for the power stroke. Energy is transferred from ATP to the myosin head.

What is the role of calcium in the cross bridge cycle?

Calcium binds to troponin, altering its shape.

Calcium binding to troponin causes tropomyosin to move away from the active sites on actin.

What role does tropomyosin play in the cross bridge cycle?

The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form.

Tropomyosin covers active sites in relaxed muscle. When tropomyosin is displaced, the active sites are exposed for cross bridge formation

How does troponin facilitate cross bridge formation?

Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin

For cross bridges to form, tropomyosin must not block active sites. Position of tropomyosin controlled by te regulatory protein troponin. This protein-protein interaction couples the binding of calcium (to troponin) to the exposure of active sites.

What, specifically, is a cross bridge?

myosin binding to actin

Attachment of myosin head from thick filament to active site on actin on thin filament is a cross bridge. As soon as cross bridge forms, the power stroke occurs, moving thin filament toward center of sarcomere.

Which event causes cross bridge detachment?

ATP binding to the myosin head

Event	Role in the Cycle
ATP binding to the myosin head	Lowers the affinity of myosin for actin, causing the head to release its grip.
Release of ADP and inorganic phosphate	Triggers the power stroke, causing the myosin head to pivot and pull the actin filament.	No
Release of calcium from troponin	Allows tropomyosin to block the binding sites again, preventing new cross-bridges from forming.	No
Nervous input ends	Signals the overall muscle to stop contracting by halting calcium release.	No

Where in the cross bridge cycle does ATP hydrolysis occur?

ATP is broken down, its energy is used to cock the myosin head in preparation for the next power stroke.

How/when does the myosin head cock back to store energy for the next cycle?

After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.

ATP provides energy to cock the heads back after the previous power stroke.

BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?

Myosin heads would remain detached, unable to cock.

hydrolysis of ATP is required for the cocking of the myosin head. ATP would still bind to myosin, causing cross bridge detachment, but myosin would be stuck in this step of the cross bridge cycle.

During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?

There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.

There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.

During contraction, about half of the myosin heads are attached, preventing the actin myofilament from sliding backwards when any single myosin head detaches. The situation is analogous to a game of tug-of-war. In tug-of-war, individual hands release after they pull on the rope, but not all hands release at the same time.

Which of the following is responsible for preventing a muscle from contracting?

Calcium ions are removed from the sarcoplasm by active transport.

Removal of calcium ions lowers the calcium ion concentration below the threshold for muscle contraction.

A weightlifter attempts to lift a barbell that is too heavy for him to move. Despite applying maximum effort, the barbell remains stationary. What physiological process best explains the muscle's response in this scenario?

isometric contraction.

Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?

Friction causes a loss of energy.

• Vascular resistance: As blood flows thru systemic circ, it rubs against inner walls of blood vessels (endothelium).

• Conversion to thermal energy: Friction creates resistance to flow, converting mechanical energy (blood pressure) into heat energy = gradual drop in BP as distance from heart increases.

• Arterioles: Small arterioles offer highest resistance in circ syst, causing steepest drop in pressure.

In which of the following tube would the flow be the highest?

Tube 1: beginning pressure = 25 millimeters of mercury (mm Hg); ending pressure = 1 mm Hg

Tube 2: total hydrostatic pressure = 24 mm Hg

Tube 3: beginning pressure = 100 mm Hg; ending pressure = 78 mm Hg

Tube 1, because the pressure gradient is the highest

If the radius of a tube decreases by half, what will happen to the resistance to fluid flow?

Resistance will increase 16 times.

R = 1/r^4

Which of the following causes a decrease in resistance in a vessel?

Vasodilation

Poiseuille's law: vascular resistance (R) is determined by: blood viscosity (n), vessel length (L), and vessel radius (r)

R = 8nL / (pi) r^4

In which of the following tubes would the flow rate be greatest?

Tube 1: velocity = 10 cm/min, cross-sectional area = 2cm²

Tube 2: velocity = 20 cm/min, cross-sectional area = 1 cm²

Tube 3: velocity = 5 cm/min, cross-sectional area = 5 cm²

Tube 3

Flow rate (Q) = Velocity (v) * Cross Sections area (A)

Which of the following tubes would have the highest flow rate?

Tube 1: water flowing in a 4-centimeter-long tube with a radius of 4 millimeters

Tube 2: water flowing in a 2-centimeter-long tube with a radius of 8 millimeters

Tube 3: blood flowing in a 4-centimeter-long tube with a radius of 4 millimeters

Tube 2

Poiseuille's Law: Flow rate (Q) of fluid thru tube depends: radius (r), ttube length (L), & fluid's viscosity (n)

Q = r^4 / nL

• Viscosity: Water much lower viscosity than blood = water flows more easily than blood.

Blood flows through a vessel at a particular flow rate and velocity. What happens to the velocity of the blood flow through that vessel after it constricts, narrowing its diameter? You may assume that the flow rate is unchanged.

Velocity increases.

Flow rate (Q) = Velocity (v) * Cross Sections area (A)

Reducing vessel's diameter thru constriction reduces its cross-sectional area (A).Compensate smaller area & maintain exact same volume of blood moving thru every second, blood must move faster thru narrow bottleneck

When the radius of the flow tube is decreased, the _______.

fluid flow rate decreases

Flow Rate (Q) = P*pi*r^4 / 8*n*L

During exercise, we might expect blood vessels in the skeletal muscle to be somewhat _______________ and the blood vessels in the digestive organs to be somewhat ____________.

dilated, constricted

• Skeletal muscles (Dilated): active muscles req massive influx of oxygen & nutrients. sympathetic nervous system & local metabolic factors trigger vasodilation to maximize blood flow to tissues.

• Digestive organs (Constricted): Non-essential processes like digestion are temporarily deprioritized. The body initiates vasoconstriction shunt & redirect blood volume toward working muscles.

Laminar flow of the blood is achieved through _______.

vasodilation

Vasodilation: widening of blood vessels decreases vascular resistance & slows flow velocity, creating a smooth, orderly, and streamlined movement of blood in parallel layers

The free-flowing blood located in the middle of a blood vessel is called _______.

laminar flow

The flow rate of a liquid is _______.

directly proportional to the pressure gradient

Q = /\P / R

Which of the following has the greatest effect on peripheral resistance?

blood vessel diameter

Polycythemia results in _______.

increased resistance to flow

What is the effect of increased viscosity?

decreased flow rate

Viscosity is a fluid's internal resistance to flow (its "thickness"). When viscosity increases, the internal friction between fluid layers rises, which naturally slows down the overall flow rate.

Formed elements in the blood _______.

include platelets and whole cells that slide past one another

Increasing blood vessel length _______.

same effect as decreasing blood vessel radius & increases resistance to flow

• Increases Resistance: Poiseuille's law, resistance directly proportional to vessel length. vessel longer increases friction & surface area inside tube, which raises resistance.

• Effect on Radius: A smaller (decreasing) radius also increases resistance to blood flow. Therefore, a longer vessel and a narrower vessel both result in higher resistance and lower flow rate

shorter tubes offer less resistance and yield higher flow rates.

Which of the following has the greatest effect on blood flow?

blood vessel radius

R = 8nL / pi r^4

Which of the following describes why the body might need to increase vessel length?

to accommodate weight gain and height changes

When blood vessel length increases, _______.

surface area increases

Which of the following is true of blood vessel length?

It increases as we approach puberty.

What maintains the driving pressure on blood while the heart is NOT contracting (ventricular diastole)?

Recoil of the elastic arteries

Using a sphygmomanometer, a nurse measures a patient's blood pressure as 134/86. What are the patient's pulse pressure and mean arterial pressure?

PP = 48 mm Hg and MAP = 102 mm Hg

Pulse Pressure (PP): Systolic — diastolic BP:
134-86=48mm\ Hg

Mean Arterial Pressure (MAP): avg pressure in pt's arteries during single cardiac cycle. Heart spends 2x much time in diastole (resting) as it does in systole (contracting)

MAP = diastolic + 1/3 PP

Hours after a surgery, a patient is taken for a walk around the hospital floor. What effect would an increase in venous return have on mean arterial pressure?

It would increase it, by shifting blood from the veins into the arteries.

Blood pressure can be measured with a sphygmomanometer. When the display indicates diastolic pressure, what is heard through the stethoscope? Why?

Nothing is heard, because blood flow is smooth through the fully open artery.

Systolic pressure is recorded when Korotkoff sounds are first heard .

A patient is vomiting and has diarrhea. Which would you expect?

heavy fluid loss = dehydration = depletes total volume of water in blood plasma

BP relies on volume of fluid w/in circulatory syst to press against blood vessel walls, a drop in blood volume reduces preload and cardiac output = decreased BP (hypotension). Body compensate by increasing the heart rate and constricting blood vessels, fluid loss will keep the blood pressure low until the patient is rehydrated.

Define cardiac output

Volume of blood pumped out by one ventricle each minute.

Define Blood viscosity

friction RBCs encounter when moving past each other.

Define total peripheral resistance

amnt of friction blood encounters during flow thru blood vessels.

Define BP

force of the blood against the vessel wall.

Blood pressure would INCREASE as a result of  a DECREASE in __________.

blood vessel diameter

BP = force of the blood against the vessel wall.

Which of the following changes would produce the greatest change in total peripheral resistance?

• 10% change in blood viscosity

• 10% change in vessel diameter

• 10% change in vessel length

• 10% change in cardiac output

10% change in vessel diameter

main determinant of total peripheral resistance is the diameter of the small arterioles.

Blood vessel diameter increases, resistance goes down. any change in vessel diameter will affect resistance by a factor of 1 / r^4

Total Peripheral Resistance affected by what physiological conditions?

• Increased sympathetic activity

• growth

• High-altitude living

• smoking

What decreases BP?

Increase Blood vessel diameter

What increase BP?

• Increase CO

• Increase blood vessel length

• Increase total periph resist

• Increase blood viscosity

If there were a sudden increase in blood volume, what would the baroreceptors do, and what would be the effect of that reflex?

Increase firing rate; decreased myocardial contractility

The Stimulus: sudden increase in blood volume stretches walls of the blood vessels

1. Baroreceptor Response: mechanoreceptors detect stretch = increase firing rate of action potentials to brain.

2. Reflex Effect: medulla oblongata processes these signals & decreases sympathetic nervous sys output while increasing parasympathetic output. This leads to vasodilation, a decreased heart rate, and decreased myocardial contractility (the pumping force of the heart) to lower blood pressure back toward normal.

Where are the sensors for the arterial baroreceptor reflex located?

carotid sinus and aortic arch

sensors are the arterial baroreceptors themselves, located at the carotid sinus and aortic arch. They detect changes in blood pressure by the degree of stretch on the blood vessel.

If blood pressure is increased at the arterial baroreceptors, what would happen with the activity level of the parasympathetic nervous system (PNS) and sympathetic nervous system (SNS)?

increased PNS activity and decreased SNS activity

Which of the following would cause vasodilation of arterioles?

decreased activity of the sympathetic nervous system

Parasymp no interact w/ arterioles

Stimulation of the adrenal medulla would result in which of the following?

an increase in heart rate and contractility

epinephrine and norepinephrine are released from the adrenal medulla and act as part of the sympathetic nervous system, increasing heart rate and contractility. Epinephrine and norepinephrine have other effects that would also increase blood pressure.

A decrease in blood pressure at the arterial baroreceptors would result in which of the following?

sympathetic nervous sys activity increased cuz low BP. Sympathetic fibers go to ventricles of heart & increase their contractility = increase stroke volume = increase in cardiac output + BP

Mr. T's heart rate is low, but his blood pressure remains high. How could someone develop a high blood pressure without a high heart rate?

• Increased blood volume might have increased his stroke volume.

• Increased vasoconstriction might have increased his total peripheral resistance.

What is the mechanism behind myogenic autoregulation in vascular smooth muscle?

When cells stretch, mechanically gated cation channels open, depolarizing the cell, resulting in contraction.

Why is the velocity of blood lowest in the capillaries as compared with all other types of vessels?

The capillaries have the largest cross-sectional area.

What is the mechanism by which bulk flow occurs at the capillaries?

Relatively higher hydrostatic pressure on the arterial end of the capillary.

• Filtration at Arterial End: At arterial end of capillary, capillary hydrostatic pressure (pressure exerted by blood against vessel wall) is higher than blood colloid osmotic pressure (inward pulling force of plasma proteins).

• Driving Bulk Flow: Pressure difference pushes water & dissolved small solutes outward into interstitial fluid (a process called filtration).

In the capillaries, hydrostatic pressure (HP) is exerted by __________.

BP