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1) Describe, in general, the components of a feedback loop of the type seen to regulate physiologic functions.

Feedback loops are reflexes: heart [all organs] pumps to adjust to needs.

Environmental variable [sensor] ➝ transmit information via affarent pathway [nervous pathway] ➝ sending to a central regulator [integrator] ➝ send impulses out by way of efferent pathways ➝ to an effector [whatever can change environmental variable] * Continuous cycle

Feedback loop senses and changes all the time to maintain a constant variable

2) Locate the baroreceptors, recognize that they are stretch receptors responding to the degree of stretch of the arteries by blood pressure, and describe their output as the arterial pressure increases or decreases.

Baroreceptors are stretch receptors (monitor stretch in arteries)

Baroreceptors - blood pressure = arterial pressure

Located: Aortic arch and Carotid artery

3) Locate the chemoreceptors and recognize that they are sensitive to concentrations of the blood gases (carbon dioxide, oxygen, and hydrogen ions).

Chemoreceptors are sensitive to blood gases concentrations [PO₂, PO₂, PH].

Located: Aortic arch and Carotid bodies

4) Locate the venous stretch receptors and recognize that they are sensitive to the volume of blood in the great veins.

Located: Great veins (pulmonary veins, superior/inferior vena cava)

Stretch = ↑ Volume in veins which produces stretch

5) Recognize that stretching of the venous stretch receptors will result in an increased heart rate (Brainbridge reflex); further, recognize that this will help to relieve the stretch of the veins.

If stretch in great veins ➝ too little cardiac activity for amount of venous return. We need to increase cardiac activity.

Venous Stretch = ↑ rate/force (called brainbridge reflex)

6) Recognize that stretching the receptors of the venous system will cause diuresis; further, describe, in general, how this relieve the stretch.

When you drink water it stretches veins

Increased blood volume, increases stretch, diuresis [increased urine formation]

3 Stretch receptors: arterial, chemo, venous

7) Identify the afferent pathways of the cardiovascular sensors.

Affarent pathways [connections between sensors and integrator]

When you are sick, a normal internal environment cannot be maintained = usually [not always] effector in the feedback loop

Located: Vagus nerve (CN X)
Glossopharyngeal (tongue and throat)

8) Locate the cardioregulatory center and, in general, describe its function.

Cardioregulatory center ➝ central regulator center in the brain stem
- Vegetative reflexes take place here

Brain stem: parts connection to the spinal cord
1) pons
2) medulla
3) midbrain

9) Recognize that the cardioregulatory center may receive impulses from higher centers

Know

10) Identify the efferent pathways of the cardioregulatory center.

Efferent pathways: autonomic N.S.
-Parasympathetic division [rest and recuperation]

Vagus nerve (CNX): vagalefferents = meaning motor fibers

Vagus nerve is a mixed nerve [afferent & efferent pathways

11) Describe the effect of parasympathetic stimulation on the cardiovascular system (identify a cholinergic response).

Vagal efferents destination ➝ heart [SA node, AV node, arterial muscle]
- Result = cholinergic response

ACH being released (neurotransmitter)

ACH ➝ Receptors (membrane proteins) ➝ Change in fxn of cardiac muscle cells *When we change fxn we change AP conduction in those cells

Results: ↓ HR, ↓ Force, Slower AP conduction time [increase efficiency in heart]

efficiency = pump more w/ less energy

Cholinergic response = more efficient

12) Describe the effect of sympathetic stimulation on the heart and blood vessels (adrenergic response).

Adrenergic Response: Sympathetic ➝ releases epi at terminal, joins (with receptors) and will produce change in fxn.

1) ↑ HR, ↑ Force of cardiac contraction, ↑ AP speed
• Capillaries open to produce more blood flow

2) Vessels (smooth muscle)
•A rate of inherent rhythmicity and a △ in force of contraction ➝ △ in diameter

Receptors = alpha & beta

13) Identify the fact that vascular smooth muscle in one location may respond in one way to sympathetic stimulation, while that in another will respond in the opposite way.

Vascular smooth muscle in one location may respond in one way to sympathetic stimulation, while that in another will respond in the opposite way.

14) Relate pressures in the atria, ventricles, and arteries during one cardiac cycle. (The graph of the cardiac cycle relates these pressures; in order to understand the events of the cardiac cycles adequately, you should be able to draw the graph just from thinking about the pressures. Only the compulsive would memorize the graph, but if you understand the meaning, you should be able to draw it).

Know the pressure graph

15) Describe what is happening in the heart during the period of passive filling.

During passive filling: there is increased pressure in the atria and decreased [lower] pressure in the ventricle. The AV valve is open until pressure gradient changes.

Arterial pressure falls during ventricle contraction due to flow into capillaries, SL valve opens.

16) Describe the result of reversing the pressure gradient between two compartments of the cardiovascular system (for example between the ventricles and the atria or between the ventricles and the arteries).

When pressure gradient reverses there is decreased pressure in the aria, and increased pressure in the ventricle.

When this occurs [reverse gradient] the AV valve closes

In arterial: When the ventricle relaxes, pressure in there falls, blood shifts back closing the semilunar valve.

17) Name the period in the cardiac cycle after the AV valve closes and before the SL valve opens.

Isometric contraction

18) Name the period between the SL valve opening and closure.

Ejection

19) Identify the period between the closure of the SL valves and the opening of the AV valves.

Isometric Relaxation

20) Explain why the arterial pressure waveform has a bulge at the time corresponding to the peak of ventricular contraction.

The bulge corresponds to the opening of the SL valve.

21) Describe the result of ventricular contraction on arterial pressure.

Arterial pressure falls during ventricle contraction due to flow into capillaries.

22) Explain why the arterial pressure slowly falls between ventricular contractions.

Arterial pressure falls during ventricular contraction due to flow into capillaries

23) Relate the P and QRS waves to atrial and ventricular contractions respectively and correctly place these electrical events in relation to the mechanical events producing the pressure waves of the cardiac cycle.

P = atrial depolarization
QRS complex = ventricular depolarization
T = occurs with ventricle repolarization [relaxation]

24) Locate the heart sounds in relation to the events of the cardiac cycle that cause them.

S₁ = 1st part (lub): Low frequency, low pitched, long due to closure of the AV valves ① at AV valve closure

S₂ = 2nd part (dup): high frequency, high pitched, short due to closure of the SL valves, due to high pressure ② SL opening

S₃ = 3rd part (rumbling sound): occurs where AV valve opens

S₄ = 4th part (rumbling sound): occurs at the peak of atrial contraction ④ Av open

25) Differentiate between systole and diastole and systolic and diastolic blood pressure.

Saw tooth wave

High point = systolic [due to systole] = contraction

Low point = diastolic [due to diastole] = relaxation

26) Describe the meaning of cardiac output and identify its average absolute valve.

Cardiac output = volume of blood pumped by the heart per minute, can be measured anywhere [pulmonary or systemic]

max CO (vmax) ~ 25L/min.

27) Define and describe the usefulness of the cardiac index.

Cardiac index = CO/surface

It is a standardized cardiac output (same for everyone)

28) Define cardiac output in terms of stroke volume output and heart rate.

Cardiac output determined by: stroke volume output x heart rate.

Volume pumped per beat

70mL/beat x 70 BPM
= 4900 mL/min. = 54 min.

29) Describe what is meant by stroke volume output.

...

30) Identify what is meant by ejection fraction and end-systolic volume.

Ejection fraction: portion of ventricular contents pumped per beat [ejection fraction @ rest =70%]

End-systolic volume: volume in ventricle at the end of contraction [30 mL]

31) Identify the result of increasing the venous return on stroke volume output (Starling's Law or the law of the heart).

Staling's Law: If you increase venous return, stroke volume output increases.

Increased venous return produces stretch and optimizes alignment of actin & myosin (nerve contact between myosin cross-bridges & actin)

• ↑ venous return, ↑ stretch, ↑ end-diastolic volume, "preload" all increases stroke volume output

32) Recognize preload as the amount of stretch due to venous return.

Know

33) Describe the relationship with left ventricle end-diastolic volume and stroke volume output.

...

34) Identify catecholamines and calcium as facts which will influence the efficiency of cardiac contraction beyond that obtained merely by stretch.

Catecholamines and calcium increase force of contractibility.

• When epi interacts with a cell it allows for more calcium [Ca²⁺] to be let in, which equals more force

35) Describe the effect of enhanced contractility on the relationship of left ventricle end-diastolic volume and stroke volume output.

...

36) Describe the relationship between flow, pressure gradient, and resistance.

Q ∝ Pressure gradient/resistance to flow

37) Identify the units in which flow would be reported.

mmHg

38) Identify the fact that the mean systemic filling pressure determines the maximum gradient possible.

Mean systemic filling pressure = 7mmHg

Determines the maximum gradient possible

Heart redistributes pressure in circulatory system
~ Pressure from arteries ➝ pressure in arteries, creates a pressure gradient

39) Describe how the heart redistributes the mean systemic filling pressure.

Determines the maximum gradient possible

Heart redistributes pressure in circulatory system
~ Pressure from arteries ➝ pressure in arteries, creates a pressure gradient

40) Describe what is meant by mean arterial pressure

...

41) Relate the pressure in the arteries, capillaries, veins and right atrium.

As blood leaves the ventricle it is at the high point of the 100mmHg in the arteries & decreases as it returns back to the heart.

Veins BV = 10 mmHg
Atrium BV = 0 mmHg
Arteries BV = 100 mmHg
Capillaries BV = 17 mmHg

Average blood volume = 7 mmHg

42) Identify the total blood volume and the size of the vasculature as factors which determine the mean systemic filling pressure.

Average blood volume = 7mmHg

Flow is proportional to pressure gradient over resistance to flow

Max pressure gradient is a result of MSFP

MSFP

The average pressure in the systemic circulation which tends to push blood back to the heart. Name this term.

43) Describe how the size of the vasculature can be varied.

If an individual gains or loses weight the vasculature must expand or decrease to accommodate needs.

44) Describe the relationship of vessel diameter, viscosity, and vessel length on peripheral resistance.

Resistance to flow factors:
1) Diameter of vessels: R ∝ 1/d⁴ greater diameter, less resistance
2) Viscosity [thickness]: R ∝ V greater viscosity, greater resistance
3) Length of vessels: R ∝ L greater length, greater resistance

45) Describe the relationship of the factors determining resistance by a formula.

resistance factors

R ∝ V•L/d⁴

Resistance is proportional to volume times length over diameter ⁴

46) Describe Poiseulle's Law by a formula.

Q ∝ P/R, R ∝ V•L/d⁴

Q ∝ P•d⁴/V•L

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