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Cardio III
Determinants of Cardiac Performance, Preload & Afterload, Pressure changes, Determinants of blood flow and pressure, Baroreceptor Reflexes
55
Anatomy
Undergraduate 3
10/13/2014

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Cards

Term
What happens when the aortic valve opens during ventricular contraction?
Definition
- rapid outflow of blood
- increase in arterial pressure
- Aorta elasticity absorbs some pressure
Term
What happens when the aortic valve closes during diastole?
Definition
- no blood flowing from ventricle
- elastic energy in aorta is released
- blood flow in vessels is then allowed to continue
- gradual decrease in arterial pressure
Term
T or F: The sympathetic nervous system decreases heart rate
Definition
False, it increases it
Term
Give a formula for calculating the Cardiac output
Definition
Heart rate x Stroke volume
Term
Define stroke volume
Definition
The volume of blood ejected per contraction
- End-diastolic Volume (EDV) - End-systolic volume (ESV)
Term
What is the preload?
Definition
a.k.a. The End-diastolic volume (EDV)
- the volume of blood present in the ventricles at the end of diastole
Term
What is the afterload?
Definition
a.k.a. The End-systolic volume (ESV)
- the residual volume of blood contained in the ventricle after systole
Term
If there is an increase in EDV, what happens to the stroke volume?
Definition
It also increases
Term
What are the four components to the Frank-Starling Law?
Definition
1. As preload increases, contractility of the heart increases, and stroke volume increases
2. Increased stretch in cardiac fibers enhances Ca2+ binding to Troponin-C, inducing an increase in contractility
3. Under resting conditions, EDV stretches cardiac muscle to sub-optimal levels
4. The pericardium inhibits cardiac muscle from stretching beyond the optimum
Term
What is the main factor affecting preload/EDV?
Definition
Venous return
Term
What are some factors affecting venous return?
Definition
- Skeletal muscle pump
- respiratory activity
- blood volume
- Autonomic nervous system
Term
What are the factors affecting afterload/ESV?
Definition
- the amount of resistance felt my the ventricles during ejection
- Total Peripheral resistance (TPR) or Arterial Vascular Resistance or Arterial vasomotor tone
- Blood pressure
Term
Give a formula for blood pressure
Definition
BP = Cardiac output x arterial resistance
Term
What are the factors of blood vessels that affect blood pressure?
Definition
diameter, elasticity, contractility
Term
Define Flow
Definition
volume of fluid transported per unit time
Term
On what two factors is flow dependent?
Definition
Difference in pressure between two points; resistance
Term
Give an equation for Flow
Definition
Flow (Q) = Pressure Diff.(delta P) / Resistance (R)
Term
Is pressure higher in arteries or veins?
Definition
Arteries
Term
What level of the arterial/venous system is referred to as the "bottleneck"?
Definition
arterioles
Term
At what phase is starting/initial pressure measured?
Definition
Systole
Term
On what factors does resistance depend?
Definition
- length of vessel
- radius of vessel *** (most important)
- viscosity of blood
Term
If radius is increased by a factor of 2, resistance decreases by a factor of...
Definition
16 (n^4)
Term
What is the mean blood pressure?
Definition
(MBP) The mean of the systolic and diastolic blood pressure
- less than half b/c diastolic takes longer
Term
MBP is closer to diastolic under what condition?
Definition
resting
Term
MBP is closer to systolic under what condition?
Definition
exercise
Term
What are the main variables involved in control of blood pressure?
Definition
heart rate
stroke volume
total peripheral resistance (TPR)
Term
What components are involved in blood pressure reflex?
Definition
baroreceptors
sensory fibers
integration center
motor fibers
effectors
Term
What are baroreceptors and where are they found?
Definition
receptors with free nerve endings; detect stretching of the arterial wall

found in sensitive areas e.g. aortic arch & carotid sinus
Term
Sensory fibers ascend via the _____ _____
Definition
vagus nerve
Term
Sensory fiber stretch increases = _____ in AP frequency
Definition
increase
Term
Where is the integration center for the control of blood pressure?
Definition
cardiovascular center in the medulla oblongata
Term
True or False

Motor fibers controlling blood pressure are a part of the somatic nervous system
Definition
False

Autonomic
Term
What are the effectors involved in controlling blood pressure?
Definition
Heart rate & stroke volume (cardiac output)
Arterioles & veins (TPR)
Term
What does TPR stand for?
Definition
total peripheral resistance
Term
What is postural hypotension?
Definition
decrease in blood pressure as you change from lying down to standing up, causing blood to flow from the thoracic cavity to lower extremities
Term
What is the immediate response to postural hypotension?
Definition
baroreceptor reflex compensates for the change
-stretch receptors slow down in firing
-parasympathetic activity decreases (increases heart rate)
-sympathetic activity increases (increases heart rate, stroke volume, vasoconstriction)
Term
What is the atrial volume receptor reflex?
Definition
stretch receptors in wall of atria regulate blood volume via:

-autonomic nervous system activity
-neural input controlling thirst & hormone secretion (changes handling of sodium & water in the kidneys)
Term
What hormone increases sodium excretion? Where is it synthesized?
Definition
Atrial Natriuretic Peptide (ANP)

synthesized in atrial wall
Term
What is renin?
Definition
-hormone synthesized in the kidney
-increases angiotensin II synthesis
Term
What does angiotensin II do?
Definition
promotes vasoconstriction
Term
Angiotensin II can be converted into _____ which decreases _____
Definition
aldosterone

sodium excretion
Term
What hormone decreases water excretion at the kidney?
Definition
antidiuretic hormone (vasopressin)
Term
What is the diff b/w sys and diasolic pressure?
Definition
Pulse pressure (measure of pressure on artery wall during systole)
Term
What factors affect arterial pressure?
Definition
Elasticity
Cardiac Output
Respiration
Resistance
Blood volume
Term
What is basal level of constriction?
Definition
myogenic tone (basal tone)
- makes it possible to decrease vessels contraction this increase diameter
Term
How is vascular resistance controlled?
Definition
- arterioles' walls are less elastic, and have more smoos muscle fibers
- basal level of constriction
- diameter decreases, resistance increases
- autoregulation (local mechanisms)
- extrinsic control factor (neuro-hormonal)
Term
Define myogenic (pressure) autoregulation
Definition
- vessels respond to changes in tone or stretch
- maintain blood supply virtually unchanged even with change in pressure
Term
Define metabolic regulation
Definition
- response to changes in metabolism
- results in increase in diameter
- relative importance of factors depend on organ
Term
Define autoregulation
Definition
(within organ or tissue) overrides extrinsic regulation
- control of flow in critical organs (therefore a protective mechanism)
Term
Define extrinsic regulation
Definition
- regulate extrinsic pressure as a whole
- vasoconstrictive influences (sympathetic stimulation on a-adrenergic receptors, angiotensis II, arginin vasopressin)
- vasodilatory influences (mainly penish and clitorish)
Term
During inspiration, as P in the thorax ______, pressure in the abdomen ________. (increases or decreases)
Definition
decreases
increases
Term
T or F: veins have little resistance
Definition
true
Term
What draws venous blood back to the heart?
Definition
Its low pressure after contraction
Term
T or F: Veins possess smoos muscle
Definition
True!
Term
When blood pressure in veins is too high, what happens?
Definition
Flow is reduced and fluid leaks out/accumulates in tissue (edema)
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