bio 252 exam 3

3 layers of a vein/artery

tunica intima, tunica media, tunica extrema

tunica intima

the innermost layer of blood vessels (arteries and veins) and consists of a single layer of endothelial cells resting on a basement membrane, loose subendothelial connective tissue, and (in arteries) an internal elastic lamina

endothelium

continuous, single-layer of simple squamous epithelial cells that directly contacts and faces the flowing blood

what is the primary role of smooth muscle cells in the tunica media?

regulate diameter of the lumen

• vasoconstriction (decrease in diameter)

• vasodilation (increase in diameter)

Vasoconstriction occurs when there is stimulation of the smooth muscle in the…

tunica media

what part of the nervous system controls smooth muscle in the tunica media?

sympathetic nervous system

desribe the term high compliance as it applies to arteries…

because they have many elastic fibers, arteries are able to stretch their walls easily in response to a small increase in pressure

function of elastic arteries

they stretch to absorb the surge of blood ejected during ventricular contraction, storing energy that is then released as recoil to keep blood moving during ventricular relaxation—functioning as a pressure reservoir

muscular arteries

control blood flow to organs, major site of vasodilation and vasoconstriction, medium-sized

anastomosis

union of the branches of two or more arteries supplying the same body region

collateral cicrulation

the alternate route taken by blood through an anastomosis

• supports circulation when blood flow is stopped or vessel is blocked

arterioles

regulate the flow of blood into the capillary networks of the body's tissues

Identify the structure that regulates the blood pressure into a capillary.

precapillary sphincter

capillaries

the thin walls of capillaries allow the exchange of substances between the blood and body tissues

• groups of capillaries within a tissue reunite to form small veins called Venules

metarteriole

terminal end of an arteriole, tapers toward the capillary junction, and empties into a venule

post capillary venule

venule that receives blood from a capillary

capillary bed

network of 10-100 capillaries that arise from a single metaeriole

why does the exchange of materials occur only through walls of capillaries and the beginning of venules?

capillary walls are composed of a single layer of endothelial cells and a basement membrane, so substance in the blood only has to pass through one cell layer to reach interstitial fluid and tissue cells

what body tissues have low/high numbers of capillaries?

low: tendons and ligaments

high: muscles, brain, liver, kidneys, and nervous system

The exchange of substances between blood and body tissues occurs in which of the following blood vessels?

capillaries

veins

blood vessels that convey blood from the tissues back to the heart

venules

small vein that collects blood from capillaries and delivers it to a vein

what do thin walls of postcapillary and muscular venules allow for?

to expand and serve as excellent reservoirs for accumulating large volumes of blood

how are veins different from arteries?

• they have little smooth muscle and elastic fibers

• lack internal and external elastic membrane

• not designed to withstand high pressure

• have large lumen

valves

prevent the backflow of blood in veins, needed because of low blood pressure in veins

A vein with a thin endothelial wall that contains no smooth muscle is called a…

vascular sinus

where is the largest portion (64%) of your blood volume at rest?

systemic veins and venules (blood reservoirs)

blood reservoirs

systemic veins and venules that contain large amounts of blood that can be moved quickly to parts of the body requiring the blood

blood flow

the volume of blood that flows through any tissue in a given time period (in mL/min)

what factors determine blood pressure?

cardiac output (heart rate x stroke volume = volume ejected per minute), blood volume, and vascular resistance

Mean arterial pressure (MAP)

the average blood pressure in arteries

MAP=diastolic BP+1/3 (systolic BP−diastolic BP)

As blood passes from systemic arterioles into capillaries, the pressure drops to about…

35 mmHg

how does blood pressure depend on total volume of blood?

volume decreases - blood pressure decreases

volume increases - blood pressure increases

what 3 factors does vascular resistance depend on?

lumen size, blood viscosity (thickness), and total blood vessel length

Which change would produce the greatest increase in vascular resistance and blood pressure, assuming that the other factors remain unchanged?

A marked decrease in arteriole lumen diameter

The skeletal muscle pump most directly impacts which factor determining cardiac output?

venous return

velocity (speed) of blood flow

distance travelled in a given period of time (cm/sec)

circulation time

time required for a drop of blood to pass from the right atrium, through the pulmonary circulation, back to the left atrium, through the systemic circulation down to the foot, and back again to the right atrium

• normally one minute

venous return

the volume of blood flowing back to the heart through the systemic veins, occurs due to the pressure generated by contractions of the heart's left ventricle

how does venous blood get to the heart?

muscular pump, respiratory pump, venoconstriction

which of these patterns would you expect to see with a portal system

artery → capillary → vein → capillary → vein

portal system

where blood flows through two sequential capillary beds connected by a blood vessel (usually a vein) before returning to the heart

Which layer of a blood vessel wall is composed primarily of smooth muscle and elastic fibers, and is responsible for regulating lumen diameter through vasoconstriction and vasodilation?

tunica media

A large elastic artery like the aorta stretches during ventricular ejection and then recoils during ventricular relaxation, helping maintain blood flow even while the heart is between beats. This function is best described as the artery acting as a:

pressure reservoir

sinusoid

wider, more winding capillaries with large intercellular clefts and an incomplete or absent basement membrane, allowing proteins and even blood cells to pass through — a feature found in the liver and spleen

During a marathon, a runner's skeletal muscles need dramatically more blood flow. Which mechanism directly increases blood volume available to the working muscles by reducing the volume held in venous reservoirs?

Venoconstriction driven by increased sympathetic stimulation

An obese patient has significantly more adipose tissue, and therefore more total blood vessel length, than a lean individual of the same height. All else being equal, how would this be expected to affect the patient's blood pressure, and why?

Increase it, because longer total vessel length increases vascular resistance

Blood velocity is slowest in capillaries compared to the aorta or venae cavae. What is the best explanation for this, and why is it functionally important?

Capillaries have the greatest total cross-sectional area, and slow flow allows more time for exchange with tissues

Which two mechanisms, aside from the pumping action of the heart itself, assist in returning venous blood from the lower limbs back toward the heart?

The skeletal muscle pump and the respiratory pump

A patient who has been standing motionless for a long period (such as a soldier standing at attention) begins to feel lightheaded and faints. Which physiological factor related to venous return best explains this?

Without leg muscle contractions to compress the veins, gravity causes blood to pool in the lower limbs, reducing venous return and cardiac output

cardiac cycle

a complete heartbeat consisting of complete systole and diastole of the ventricles and atria

as the chamber of the heart contracts…

blood pressure within it INCREASES

Which interpretation best describes the relationship between pressure and blood ejection in the two sides of the heart during a cardiac cycle?

The left side develops higher pressures, but each ventricle expels the same volume per beat.

How does atrial systole contribute to the end-diastolic volume (EDV) in the heart?

By adding additional blood volume to the ventricles in diastole.

What is the key event that marks the transition from isovolumetric contraction to the ejection phase during ventricular systole?

Opening of the semilunar valves

What occurs during the relaxation period of the cardiac cycle?

Both atria and ventricles are relaxed, with ventricular filling taking place after AV valves open.

stages of cardiac cycle in order

atrial systole, isovolumetric contraction of the ventricles, ejection phase of the ventricles, isovolumetric relaxation of the ventricles

heart sound 1 (S1)

can be described as a lubb sound, is louder and a bit longer than the second sound

• S1 is caused by blood turbulence associated with closure of the AV valves soon after ventricular systole begins

heart sound 2 (S2)

described as a dupp sound

• S2 is caused by blood turbulence associated with closure of the SL valves at the beginning of ventricular diastole

arteries and veins have the lowest ___ but the highest ___

cross-sectional area, velocity

capillaries have the lowest ___ but the highest _______

velocity, cross-sectional area

each class of vessels has the same…

flow (volume/minute)

On a normal ECG tracing, which wave represents the spread of depolarization through the ventricular contractile fibers?

QRS complex

During the plateau phase of a ventricular contractile fiber's action potential, membrane voltage remains close to 0 mV for about 0.2 seconds rather than immediately repolarizing. What ionic mechanism best explains this sustained depolarization?

Ca2+ influx roughly balancing K+ efflux

A drug blocks voltage-gated Ca2+ channels in the sarcolemma of ventricular contractile fibers without affecting Na+ or K+ channels. Which of the following would most directly result?

Reduced strength of cardiac muscle contraction

During which phase of the cardiac cycle are all four heart valves closed simultaneously, with no change in ventricular volume, even though the ventricular muscle fibers are actively generating force?

isovolumetric contraction

A 22-year-old healthy volunteer has a resting heart rate of 75 beats/min, giving a cardiac cycle length of 0.8 sec. If her heart rate increases to 150 beats/min during exercise, which phase of the cardiac cycle would be expected to shorten the most?

relaxation period

Immediately after the QRS complex appears on the ECG, which mechanical event begins?

Ventricular systole

Just after the T wave begins on the ECG, what happens to blood in the aorta and pulmonary trunk as the ventricles start to relax?

It begins to flow backward toward the ventricles, closing the semilunar valves

where does the heart lie?

the mediastinum

The membrane that surrounds and is attached to the heart is…

visceral pericardium

main parts of the pericardium

fibrous and serous pericardium

functions of fibrous pericardium

limits expansion of the heart, anchors heart, composed of dense irregular connective tissue

layers of the heart wall

endocardium - (outermost layer) composed of two layers

myocardium - (middle layer) responsible for the pumping action of the heart and is composed of cardiac muscle tissue, makes up 95% of the heart wall

epicardium - (external layer) provides a smooth lining for the chambers of the heart and covers the valves of the heart

atria

two superior receiving chambers, receive blood from blood vessels returning blood to the heart, called veins

ventricles

2 inferior pumping chambers, eject the blood from the heart into blood vessels called arteries

paths of the 2 circuits of the heart

systemic veins - right atrium - right ventricle - pulmonary artery (pulmonary trunk)

pulmonary veins - left atrium - left ventricle - systemic artery (aorta)

The superior and inferior vena cava are the major systemic veins. They enter into the

right atrium

Although the right and left ventricles act as two separate pumps that simultaneously eject equal volumes of blood…

the right ventricle has a much smaller workload, so the left side has to work harder to maintain the same blood flow

• left side takes blood all throughout the body, right ventricle only pumps to lungs

The valve located between the left atrium and the left ventricle is the…

bicuspid valve (atrioventricular valve)

valve located between right atrium and right ventricle

tricuspid valve (atrioventricular valve)

valve located between right ventricle and right artery

pulmonary valve (semilunar valve)

valve located between left ventricle and left artery

aortic valve (semilunar valve)

when does blood flow through AV valves?

when atrial pressure is higher than ventricular pressure

The contraction of the papillary muscles and the attached chordae tendineae function to…

prevent the valve cusps from entering into the atrial chambers

Which chambers of the heart contain deoxygenated blood?

right atrium and right ventricle

double circuit path of blood

blood passes through the heart twice in a single complete journey around the body

• systemic circulation: oxygenated blood flows from the left ventricle to the aorta to all organs in the body, then returns deoxygenated to the right atrium

• pulmonary circulation: deoxygenated blood from the right ventricle to the lungs and return of oxygenated blood from the lungs to the left atrium

intercalated disks

irregular transverse thickenings of the sarcolemma in cardiac muscle fibers

• contain desmosomes (hold fibers together) and gap junctions (allow muscle action potentials to conduct)

• THINK SURFACE AREA

autoryhthmic fibers

specialized cardiac muscle cells

• commonly called pacemaker cells

• act as natural “pacemaker” - set rhythm that causes contraction

• form cardiac conduction system (makes sure that cardiac chambers become stimulated to contract in a coordinated manner)

sequence of cardiac action potentials

1. normally begin in SA node (propogates through both atria via gap junctions in intercalated discs)

2. action potential reaches AV node, atria empty blood into ventricles

3. AP enters AV bundle, only site where APs can conduct from the atria to the ventricles

4. AP enters right and left bundle branches

5. Purkinje fibers conduct the AP upward to the ventricular myocardium, ventricles contract, blood pushed upward toward semilunar valves

what is the purpose of a cardiac action potential?

to generate the electrical signal and calcium influx required for the heart muscle to contract in a synchronized, rhythmic sequence that pumps blood through the body

SA node establishes…

frequency of action potentials and the sinus rhythm

HCN/funny channels

in pacemaker cells of the heart, does not permit the membrane to truly stabilize in a polarized state

• opened by HYPERPOLARIZATION

During the conduction of the action potentials through the conduction pathway, there is a temporary delay at the…

AV node

3 clearly recognizable waves with each heartbeat in a electrocardiogram

P Wave, QRS complex, T wave

P wave

small upward deflection on the ECG

• represents atrial depolarization (from SA node through contractile fibers in both atria)

QRS complex

begins as a downward deflection, continues as a large, upright, triangular wave, ends as a downward wave

• represents rapid ventricular depolarization (AP spreads through ventricular contractile fibers)

T wave

dome shaped upward deflection

• indicates ventricular repolarization, occurs just as the ventricles are starting to relax

difference between systole and diastole

CONTRACTING - systole

RELAXING - diastole

A 68-year-old man undergoes cardiac surgery. The surgeon notes that the innermost layer lining his heart's chambers is continuous with the endothelium of the great vessels attached to the heart. Which layer is the surgeon describing?

endocardium