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ZOOL463 > Circulation > Flashcards

Circulation Flashcards

1
Q

What are some things carried by the blood or hemolymph?

A

O2, CO2, nutrients, waste products, immune bodies, proteins, lipids, RBCs, platelets, hormones, heat

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2
Q

What is Q?

A

The volume passing through a cross sectional area over time. It’s equivalent to vol/t or A x d/t or A x v since velocity is d/t. And Q is always conserved in pipes.

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3
Q

What happens to our Q parameters as the pipe radius decreases and branches?

A

Q stays the same as it is conserved no matter what.
If the radius decreases A decreases and v increases.
If the pipe branches, the sum of the areas can be the same, less, or more. If the sum is less, then the velocity is increased. If the sum is more, the velocity is decreased.

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4
Q

What is the Hagen-Poiseuille law and what can we use it for?

A

Q ~ (P1-P2)r^4/muL or Q ~ (P1-P2)/R. In this state, its useful to describe flow from driving pressure and resistance/radius.
Rearranged, P1-P2~QR or QmuL/R^4 which is useful for describing pressure drops due to resistance or radius.

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5
Q

What are the 3 components of a cardiovascular system? Are these three components always there?

A

Fluid being moved, pumps to move the fluid and vessels that fluid moves through. Sometimes one or more components are absent.

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6
Q

Name the different kinds of vessels in order of appearance from the heart.

A

Aorta, arteries, arterioles, capillaries, venules, veins.

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7
Q

What is the function of the aorta and arteries?

A

To rapidly deliver blood through the body because they are large and round vessels and to depulsate the heart because of their stretchiness, allowing flow to be constant.

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8
Q

What is the function of arterioles?

A

They have a smaller radius and are able to tightly control where blood is flowing by dilating or constricting (increased resistance = reduced flow + big pressure drop)

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9
Q

What is the function of capillaries?

A

They are the sites of gas diffusion. They have very thin walls, a massive area with very low velocity, and a large pressure drop in each capillary to facilitate this.

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10
Q

How far does pressure generated by the heart drive blood?

A

To the capillaries.

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11
Q

What is the function of veins?

A

They act as one way valves and have essentially no pressure (come after capillaries and venules) and act as reservoirs for non mobilized blood.

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12
Q

When is more blood mobilized and where from?

A

During exercise from the veins.

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13
Q

Around how much of the blood in the body is in the veins at rest?

A

60%

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14
Q

How does venous return occur?

A
  1. Skeletal muscle pump, pushes blood through one way valves.
  2. Constriction of vascular smooth muscles, which works similarly it’s just the veins themselves and not the muscle surrounding.
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15
Q

Define and contrast a closed versus an open circulatory system.

A

A closed circulatory system has a pump, vessels, fluid, and capillaries. There are no gaps. It contains blood.
An open circulatory system has a pump, vessels, fluid, and an open space between vessels called the sinus. Sometimes there are also capillaries. The fluid is hemolymph.

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16
Q

What is the difference between a vein and a sinus as a vessel, not a gap?

A

A sinus has the same function as a vein it’s just very small.

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17
Q

What are the differences between the atrium and ventricle in the vertebrate heart?

A

The atrium has thinner walls. It directly flows to the next chamber.
The ventricle has thicker walls and acts as the power pump of the heart. The left ventricle is also thicker than the right as it supplies circulation to the whole body and not just to the lungs.

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18
Q

What are the main features of vertebrate hearts?

A

Atrium (1 or 2), ventricle (1 or 2), sinus venosus, bulbus or conus arteriosus, one-way valves

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19
Q

What is the sinus venosus?

A

The first receiving chamber of the heart, it becomes continuous with the right atrium in mammals, birds, and crocodilians. It acts as the main pacemaker of the heart.

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20
Q

What is the main pacemaker of the heart?

A

The sinus venosus.

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21
Q

What is the bulbus or conus arteriosus?

A

The downstream receiving chamber of the heart after the ventricle(s). It is not distinct in mammals.

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22
Q

Define the difference between systemic, pulmonary, and branchial circulation. Hint: where are they and what tissues are they serving?

A

Systemic: serves tissues
Pulmonary: serves lungs
Branchial: serves gills, absent in mammals.

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23
Q

Describe some features of the bird/mammalian heart.

A

It has 4 chambers, it has a completely separated right and left, it is one-way, low oxygen and high oxygen blood are completely separated, it has very high pressures and flow rate and this is important for endothermy.

24
Q

What is the trade off mammalian and bird hearts have as compared to crocodiles and amphibians?

A

They lose the ability to shunt blood away from the lungs in exchange for an elevated flow and pressure and thus metabolic rate.

25
Q

How does shunting occur?

A

Due to changes in pressure, resistance, and flow in the heart when not breathing with the lungs (or digesting in crocodiles).

26
Q

Name the important aspects of the amphibian heart we discussed in class.

A

The left and right atria, the ventricle, the AV and semilunar valves, the conus arteriosus, the spiral fold in the conus arteriosus, the pulmonary and cutaneous artery, the systemic artery, the sinus venosus into the right atria, and the pulmonary vein into the left atria.

27
Q

How does blood move in the amphibian heart normally?

A
  1. Blood enters the right atrium from the sinus venosus and the left atrium from the pulmonary vein.
  2. This blood travels into and pools in the ventricle with very little mixing.
  3. During the first part of contraction, low oxygen blood leaves first into the vonus arteriosus and because of the spiral valve’s presence it selectively travels to the pulmocutaneous arteries.
  4. During late contraction, due to now elevated resistance from the pulmocutaneous arteries, higher oxygen blood will flow to the systemic artery.
28
Q

How does blood move in the amphibian heart while shunting blood away from the lungs?

A

Same as normal for the most part, but the pulmonary artery is constricted and thus during the first part of contraction resistance is too high for blood to flow to the lungs and it only flows to the skin for some oxygen exchange.

29
Q

How do mammalian fetal and newborn hearts differ?

A

Fetal hearts have two pathways to shunt blood away from the lungs because those are collapsed. The first path is the foramen ovale which goes from the right atria to the left atria and the second path is the ductus arteriosus which leads to the aorta from the pulmonary artery.

30
Q

What happens to the fetal heart shunts upon birth in mammals?

A

These pathways close at birth with the foramen ovale closing immediately due to pressure changes with the lungs opening and the ductus arteriosus closes by muscle contraction and degenerates into a ligament to hold vessels around the heart in place.

31
Q

How does circulation work in a lobster?

A
  1. The heart contracts, pressure increases.
  2. This pressure opens the artery valves, hemolymph flows out
  3. Stretched ligaments recoil and expand the heart
  4. The expansion means the pressure outside is greater than the pressure inside (negative pressure)
  5. The ostia valves open and suck in hemolymph
32
Q

What lets flow into a lobster heart and lets it out?

A

Ostia allow flow into the heart when open due to negative pressure and arteries let flow out of the heart when open due to positive pressure.

33
Q

Why can circulation be faster in systems with hemolymph?

A

Because hemolymph has a lower O2 capacity than blood and thus needs to move faster.

34
Q

Give an example of a cardiac system with multiple hearts.

A

Octopus. One main heart and two branchial hearts.
Worm. 5 hearts that act the same.
Insects. One main heart and two wing hearts.

35
Q

What is the structure of cardiac muscles?

A

It’s striated, mononucleated, branched, has troponin and tropomyosin, and has intercalated disks to link cells with gap junctions

36
Q

Define myogenic and neurogenic heart excitation. Where are they found? How do the pacemakers differ?

A

Myogenic: the source of stimulation is in the muscle, it’s in vertebrates, molluscs and some other invertebrates. The pacemaker is specialized muscle fibers without contractile machinery, excitation is pulsatile.
Neurogenic: the source of stimulation is out of the muscle, it’s in the rest of the invertebrates. The pacemaker is cardiac ganglion that fires rhythmically and the neurons innervate the whole heart to contract at once.

37
Q

How does cardiac contraction work?

A
  1. The membrane depolarizes due to neuro or myo stimulation.
  2. DHPRs in T-Tubules open (long calcium channels) (allows calcium to flow into the cytoplasm from the outside, but it’s not enough)
  3. Calcium binds to RyRs in the SR membrane
  4. RyRs open, releasing more calcium
    Unlike in skeletal muscle contraction, DHPRs and RyRs are not connected physically, and contraction cannot occur without external calcium from the L-type calcium channels.

It ends by moving calcium either into the SR by active pumping or by the action of an Na+/Ca2+ exchanger out ouf the cell. The sodium is then removed by an Na/K ATPase. The direction of the exchangers and the speed depend on the concentration gradient.

38
Q

Describe the causes of a cardiac muscle membrane potential over time.

A
  1. Sodium and potassium channels are open. Sodium flows in through a voltage gated channel until we go from -90mv to around +30 mV. These sodium channels close.
  2. Potassium leaks out from the cell which drops the potential a bit leading to a hump. The potassium channels close.
  3. The L-type Ca2+ channels open from the same voltage stimulus as the sodium, just slower. This causes the plateau.
  4. The L-type channels close and the K+ channels open heading to another drop
39
Q

What are some consequences of the cardiac membrane potential’s weird shape?

A

There’s a long refractory period, no tetanus, and no summation. Tetanus would be very bad.

40
Q

Describe the parts of a myogenic pacemaker potential.

A

There is no true rest, it always drifts up to the threshold.
1. K+ channels gradually close from the last excitation
2. F-type sodium channels open from hyperpolarization (f stands for funny)
3. T-type calcium channels open (T=transient, it’s fast and provides a burst of depolarization to reach the threshold)
4. At the threshold, the voltage sensitive L-type calcium channels open
5. This lets us rise to a peak where the K+ channels open again and the L-type calcium channels slowly close, leading to a slow descent back to a hyperpolarized state.

41
Q

Define atrioventricular and semilunar valves.

A

Atrioventricular valves are between the atria and ventricles. Semilunar valves are between the right ventricle and the pulmonary artery and the left ventricle and the aorta. They are one-way valves and open or close based on pressure.

42
Q

Define systole and diastole.

A

Systole: Contraction phase of a heart chamber
Diastole: Relaxation phase of a heart chamber

43
Q

Name the steps of the heart contraction cycle.

A
  1. Ventricular diastole. The pressure in the atria exceeds that of the ventricle, the AV valves open and the ventricle fills.
  2. Atrial systole. Atrial contraction forces a little more blood (~20%) into the ventricles.
  3. Ventricular systole. Isovolumetric contraction. The AV valves close and produce the first heart sound. Pressure increases.
  4. Ventricular systole. Ventricular ejection. The semilunar valves open and blood is ejected to the pulmonary artery and aorta which depulsate.
  5. Ventricular diastole. Isovolumetric relaxation. The semilunar valves close because the pressure in the arteries exceeds ventricular pressure. This is the second heart sound.
    Note: Atrial diastole occurs at the same time as ventricular systole
44
Q

How do contraction signals travel through the heart?

A
  1. The SA node on the right atria acts as the primary pacemaker (sinus venosus in other animals), it has an interatrial pathway to the left atrium and causes the right atria to contract slightly sooner than the left.
  2. The AV node also acts as a pacemaker but not its own, it receives a signal from the SA to fire and cause depolarization. It is slower than the SA node, causing an AV delay. This signal travels down the septa’s Bundle of His which starts contraction of the ventricles at the bottom of the heart.
  3. Purkinje fibres carry this signal through both sides of the ventricle.
    Note: there is also an AV ring of nonconductive fibrous tissue separating the atria and ventricles to ensure the atria fire first.
45
Q

Name and define the components of an ECG wave.

A

P: Atrial depolarization, the first bump.
QRS: ventricular depolarization. A little after P due to AV delay. Also atrial repolarization.
T: Ventricular repolarization

46
Q

Why don’t ECGs look like a normal action potential?

A

Recorded from a body surface, difference b/w two wires.
Amplitude depends on the tissue’s mass and the signal’s rate of change
The sign depends on the direction the signal is traveling and if depolarization or repolarization are being measured.

47
Q

What is MAP? How is it sensed?

A

Mean arterial pressure: the average pressure in arteries over a heartbeat cycle. It is sensed with aortic and carotid baroreceptors. Baroreflexes regulate pressure.

48
Q

What are the elements of cardiovascular regulation and how do they contribute to each other?

A

HR + Stroke volume (how much blood is pumped) = Cardiac output (volume of blood moved by heart m/min)
Arteriole radius + blood viscosity = total peripheral resistance
Cardiac output + total peripheral resistance = MAP

49
Q

How are the heart and arterioles innervated by the ANS? What neurotransmitters are used?

A

Parasympathetic: Ach. Muscarinic receptors on the heart and NO receptors on the arterioles.
Sympathetic: Epinephrine and norepinephrine. Beta-adrenergic receptors on the heart and alpha-adrenergic receptors on the arterioles

50
Q

What is tone?

A

Tone refers to the pacing of action potentials. More tone means more action potentials.

51
Q

How do the sympathetic and parasympathetic nervous systems control heart rate?

A

The parasympathetic nervous system slows down SA node firing (increasing parasympathetic tone).
Sodium conductance decreases, potassium conductance increases making the membrane a little more negative causing longer depolarization.
The rate of depolarization spreading is decreased and the AV delay is increased.

The sympathetic nervous system speeds up SA node firing which increases sodium conductance leading to faster depolarization.
The rate of depolarization spreading is increased and the AV delay is decreased.
At the ventricle only, there’s faster cross-bridge cycling and faster calcium pumping into the SR (faster relaxation so it can go again).

52
Q

What is the Frank-Starling mechanism? How does this influence stroke volume?

A

Stroke volume is determined by end diastolic volume, which is the volume of the ventricle at the end of diastole.

This works because:
1. Elasticity (more stretch = more recoil, why atrial kick vital)
2. It’s on the ascending limb of the force-length curve (the sarcomeres are longer because of this stretch which generates more force)
3. The cardiac muscle stretch increases calcium release from the SR
4. The cardiac muscle stretch increases troponin sensitivity to calcium

53
Q

How does the SNS affect the EDV?

A

Veins have sympathetic tone, an increase in this tone constricts the veins which mobilizes more blood and leads to a larger EDV.

Additionally, it activates beta-1 receptors which activate kinases (cascade with GPCRs), then the kinases phorphorylate stuff:
1. L-type calcium channels: let in more calcium
2. RyR: let out more calcium from SR
3. Troponin: more sensitive to calcium.
All together this increases cross-bridging! It’s why after heart attacks you get prescribed calcium blockers.

54
Q

What is the difference between local, hormonal, and neural controls.

A

Local controls are immediate and direct
Hormonal controls are diffuse
Neural controls are diffuse or targeted.

55
Q

How do the sympathetic and parasympathetic nervous systems control arteriole radius?

A

The parasympathetic nervous system does nothing! It doesn’t innervate arterioles.

The sympathetic nervous system does all of the following:

For dilation:
Local: exercise conditions (decreased oxygen, increased CO2, decreased pH, metabolic byproducts), immune signals from injury, increased temperature.
Hormonal: epinephrine*
Neural: decreased sympathetic tone

For constriction:
Local: colder external temperatures BUT it depends on the location of the arteriole since we do not want our core arterioles to constrict
Hormonal: Epinephrine*, vasopressin (baroreceptors detect a lack of stretch and increase water retention and blood volume and constrict vessels to maintain BP), Angiotensin II (formation targeted by BP meds)
Neural: increased sympathetic tone

*epinephrine’s impact depends on where in the body it is and what receptors are targeted.

ZOOL463 (7 decks)

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