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Test 3
Cardiac Output
79
Physiology
Undergraduate 2
11/07/2006

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Cards

Term
Define cardiac output
Definition
the volume of blood pumped by the heart per minute

CO = SV * HR

It normally equals the total blood volume of about 5.5 liters

Term
What part of the nervous system influences the heart rate?
Definition
the Autonomic Nervous System
Term
What factors influence the stroke volume?
Definition
A. the mean arterial pressure

B. the end diastolic volume and contraction strength

Term
(T or F) Without neuronal influences the heart beats according to the rhythm set by the SA node
Definition
True
Term
Define chronotropic effect
Definition
regulation of the heart rate (it may be positive or negative)
Term
What is the major means by which the heart rate is regulated?
Definition
sympathetic and parasympathetic neurons to the SA node
Term
Describe the chronotropic effect of the sympathetic and parasympathetic
Definition
sympathetic - postive chronotropic effect

parasympathetic - negative chronotropic effect

Term
What area in the brain contains the cardiac control center that coordinates the activity of the autonomic innervation of the heart?
Definition
medulla
Term
What three variable regulate stroke volume?
Definition
A. END DIASTOLIC VOLUME - the volume of blood in the ventricles at the end of diastole

B. TOTAL PERIPHERAL RESISTANCE - the frictional resistance to the blood flow in the arteries

C. CONTRACTILITY - the strength of ventricular contraction

Term
What does the EDV represent?
Definition
The EDV represents the workload on the heart prior to contraction
Term
What is the result of an increased EDV?
Definition
An increase in EDV results in greater stroke volume
Term
What is directly proportional to the stroke volume?
Definition
stroke volume is directly proportional to the contractility
Term
With what does the strength of contraction vary directly with?
Definition
The strength of contraction varies directly with the EDV
Term
What is ejection fraction?

What is its normal value?

Definition
SV/EDV

60%

Term
What is total peripheral resistance?

What causes the resistance?

Definition
TPR is the resistance to the ejections of blood from the ventricle

TPR is due to the diameter of the arteries

Term
The pressure in the arteries before the ventricle contracts is a function of the __________.
Definition
TPR
Term
The SV is inversely proportional to the ________.

The greater the TPR, the lower the _________.

Definition
TPR

SV

Term
Is the Frank-Starling law of the heart an intrinsic or extrinsic mechanism?
Definition
intrinsic mechanism
Term
Explain the Frank-Starling law of the heart.
Definition
a. there are varying degrees of stretching of the myocardium by the EDV

b. as the EDV increases it contracts more forcefully

c. as the ventricles fill, the myocardium stretches

d. it allows more force to develop and explains how the heart can adjust to a rise in TPR

Term
Define contractility

Is it controlled intrinsicly or extrinsicly?

Definition
the strength of contraction at any given fiber length

Contractility is controlled extrinsicly by the sympathetic and adrenal hormones

Term
What hormones increase contractile strength?

What is this effect called?

Definition
NE and Epi

Positive intropic effect

NOTE: the parasympathetic stimulation has a negative CHRONOTROPIC effect and DOES NOT directly influence contraction strength

Term
What is venous return?
Definition
the return of blood to the heart via the veins
Term
What is the driving force for the return of blood to the heart?
Definition
Venous pressure
Term
Do veins have a higher compliance or stretchability than arteries?
Definition
Yes

They also have thinner walls

Term
At any one time, about how much of the total blood volume is in the veins?
Definition
two-thirds
Term
What three things are controlled by factors that affect the venous return?
Definition
SV, EDV, and CO
Term
About how much of the total body water is within the intracellular compartment?
Definition
Two-thirds
Term
About how much of the total body water is within the extracellular compartment?

How much of that is in the interstitial fluid and the blood plasm?

Definition
One-third

80% in the interstitial fluid and 20% in the blood plasma

NOTE: there is a constant balance between water loss and gian in these compartments

Term
What is the net filtration pressure?
Definition
It is the hydrostatic pressure of the capillaries minus the hydrostatic pressure of the interstial fluid
Term
What is the colloid osmotic pressure?
Definition
It is the pressure exerted by plasma proteins or interstitial proteins
Term
What is the oncotic pressure?
Definition
The difference between the plasma osmotic pressure and interstitial osmotic pressure
Term
What is edema?
Definition
Edema is excessive accumulation of tissue fluid
Term
Edema may result from...
Definition
a. high arterial blood pressure

b. venous obstruction (flebitis, blood clot)

c. leakage of plasma proteins into interstitial fluid (holds fluid in those spaces)

d. myxedema in hypothyroidism

e. decreased plasma protein concentration (caused by liver failure)

f. obstruction of lymphatic drainage in elepantiasis or cancer

Term
Where does filtration begin in the kidneys?
Definition
Filtration begins when plasma runs through the glomerular capillary pores
Term
How can the volume of urine excreted be varied?
Definition
By changes in reabsorption of filtrate

It is adjusted according to the needs of the body by the action of hormones

Term
Describe how ADH works
Definition
ADH is released by the posterior pituitary when osmoreceptors detect an increase in plasma osmolality

It makes the collecting duct more permeable to water by making pores

Term
What is aldosterone?

How does it work?

Definition
Aldosterone is a steroid hormone secreted by the adrenal cortex

It stimulates a mechanism to maintain blood volume and pressure through the reabsorption and retention of sodium and chloride ions

It stimulates the reabsorption of sodium chloride

It indirectly increases the reabsorption of water

It DOES NOT dilute the osmolarity

Term
What types of conditions cause the release of aldosterone?
Definition
salt deprivation

reduced blood volume and pressure

Term
Explain the Renin-angiotensin-aldosterone system
Definition
1. When the blood pressure and flow are reduced in the renal artery, the juxtaglomerular apparatus (responsive to stress) secretes renin

2. Renin converts angiotensinogen to angiotension I

3. Angiotensin I is converted to angiotensin II by ACE (angiotensin converting enzyme) located within the lungs

4. Angiotensin II is a powerful vasoconstrictor, it stimulates the production of aldosterone, and it stimulates thirst. These both result in increased fluid retention and an increase in blood volume and pressure

Term
What is a typical drug that lowers blood pressure?
Definition
an ACE inhibitor
Term
What is ANP?

Where is it produced and how does it work?

Definition
Atrial natriuretic peptide

1. Produced in the atria of the heart when they are stretched

2. It is antagonistic to aldosterone and angiotensin II

3. It promotes sodium and water excretion in the urine by the kidney

4. It promotes vasodilation

Term
The amount of blood that the heart pumps/min is equal to _______.
Definition
The rate of venous return
Term
The flow of blood throught the vascular system is due to _______.
Definition
the pressure difference between the two ends of the system
Term
What is the simplified equation that determines the "flow" of blood
Definition
Flow = P1-P2/TPR
Term
Resistance is directly proportional to the _____ of the vessel and to the ________ of the blood

Resistance is inversely proportional to the _______ _______ of the ______ of the vessel

Definition
length, viscosity

4th power, radius

Term
What are the main regulators of blood flow through an organ?
Definition
a. mean arterial pressure

b. vascular resistance to flow

c. these are controlled by the ANS

Term
Discuss how the ANS regulates blood flow
Definition
1. sympathoadrenal stimulation increases cardiac output and the TPR

2. Alpha-adrenergic stimulation causes vasoconstricition of arteries in the skin and viscera

3. cholinergic sympathetic fibers cause vasodilation of skeletal muscles

4. the parasympathetic innervation is limited. It promotes vasodilation in the digestive tract, external genital, and the salivary glands

Term
Give two examples of paracrine regulation of blood flow

What produces paracrine regulators?

Definition
1. nitric oxide diffuses into the smooth muscle of the t.media and causes vasodilation

2. bradykinin and prostacyclin also cause vasodilation

The endothelium produces several paracrine regulators

Term
Give an example of intrinsic regulation of blood flow
Definition
The intrinsic myogenic control mechanism

It occurs because of the stretch of the vascular smooth muscle

A decrease in systemic arterial pressure causes cerebral vessels to dilate

Term
What are some examples of metabolic control mechanisms that cause vasodilation?

How does it work?

Definition
A. decreased oxygen

B. increased carbon dioxide

C. decreased pH

D. increased potassium ion

Intrinsic receptors sense chemical changes in the environment to cause vasodilation

Term
What physiological adaptations allow for the constant supply of aerobic requirements of the heart?
Definition
1. The coronary arteries supply an enormous number of capillaries

2. The myocardium contains large amounts of myoglobin to store oxygen to be released during systole

3. The heart contains an increased number of mitochondria and aerobic enzymes

Term
Give examples of how coronary blood flow is regulated
Definition
1. The sympathetic nervous system

a. alpha receptors stimulate vasoconstriction at rest

b. beta receptors stimulate vasodilation in flight or flight

2. Intrinsic regulators:

a. increased metabolism of the myocardium causes increased carbon dioxide and potassium ion, and decreased oxygen

b. these cause vascular smooth muscle to relax

Term
Give examples of how blood flow is regulated through the skeletal muscles
Definition
1. During rest, ??sympathetic alpha-adrenergic receptors stimulate vasoconstriction

2. During fight or flight, cholinergic and beta-adrenergic receptors stimulate vasodilation

INTRINSIC mechanisms...

During exercise decreased oxygen, increased carbon dioxide, increased potassium ion and a decreased pH all cause vasodilation of the arterioles

Term
Detail how circulation changes during exercise with respect to vascular resistance
Definition
vascular resistance decreases to skeletal muscles and blood flow increases

The stroke volume and cardiac output increase

Blood flow to the brain remains constant

The heart rate increases to a max of 190 beats per minute

The ejection fraction increases

Vascular resistance to the GI tract and the skin increases and blood flow descreases

Term
What happens to cerebral circulation when exercising?
Definition
1. Cerebral blood flow is not normally influenced by sympathetic nerve activity

2. At a normal range of arterial pressures the cerebral blood flow is regulated by intrinsic mechanisms:

a. myogenic - increased stretch decreases flow

b. metabolic - increased carbon dioxide increases flow and other products

Term
When exercising how is cutaneous blood flow manipulated?
Definition
1. Thermoregulation - blood flow through the skin is adjusted to maintain deep body temperatures at about 37 degress Celsius

2. Bradykinin is secreted by sweat glands that increase blood flow to the skin and sweat glands

3. Changes in cutaneous blood flow occur as a result to changes in sympathetic nerve activity

Term
When exercising how is cutaneous blood flow manipulated?
Definition
1. Thermoregulation - blood flow through the skin is adjusted to maintain deep body temperatures at about 37 degress Celsius

2. Bradykinin is secreted by sweat glands that increase blood flow to the skin and sweat glands

3. Changes in cutaneous blood flow occur as a result to changes in sympathetic nerve activity

Term
What three things determine the pressure of arterial blood
Definition
blood volume

TPR (diameter)

cardiac rate

Term
Why is arteriolar resistance the greatest?
Definition
because they have the smallesst diameter
Term
What body systems can regulate the blood pressure?
Definition
kidneys and sympathoadrenal systems
Term
Describe the Baroreceptor reflex (KNOW THIS!)
Definition
1. Stretch receptors are located in the aortic arch and the carotid sinus

2. An increase in BP stretches the wall and increases the frequency of action potentials

3. The baroreceptors send action potentials to the vasomotor control and cardiac control centers in the medulla

4. The baroreceptor reflex is activated with changes in BP

Term
Describe atrial stretch reflexes
Definition
1. Receptors located in the atria of the heart

2. The receptors are activated by an increase in venous return

3.This stimulates reflex tachycardia

4. Inhibits ADH release

5. Promotes secretion of ANP

Term
How can we measure blood pressure?
Definition
1. Done by ascultation

2. Turbulent blood flow due to use of sphygmomanometer produces vibrations in the vessels that can be heard as Korotkoff sounds

Term
What is the average pulmonary BP?
Definition
22/8 mm Hg
Term
What is pulse pressure?

What is it normally?

Definition
Pulse pressure is the systolic pressure minus the diastolic pressure

It is normally about 40 mm Hg

Term
What is the mean arterial pressure?

How is it measured?

Definition
the average arterial pressure during the cardiac cycle

it's the diastolic pressure plus one-third of teh pulse pressure

It's usually 93mm Hg

Term
What is hypertension?
Definition
blood pressure in excess of normal range for age and gender

Usually greater than 130/90 mm Hg

Term
What is essential hypertension?
Definition
primary or essential hypertension is the result of complex or poorly understood processes
Term
What is secondary hypertension?
Definition
hypertension due to a known disease process, usually the kidneys
Term
What kind of hypertension do most people have?
Definition
essential hypertension
Term
Give some characteristics of hypertension
Definition
A. increase in TPR is a universal characteristic

B. the CO and the HR are elevated in many

C. secretion of renin, angiotensis II, and aldosterone is variable

D. sustained high stress and high sodium ion intake act to develop hypertension

E. the adaptive response to hypertension is a thickening of the arterial wall causing atherosclerosis

F. the kidneys may not be able to properly excrete sodium ion and water

Term
What are some of the dangers of hypertension?
Definition
a. it is a silent killer as patients are asymptomatic until the damage has occurred

b. atherosclerosis

c. increases workload of the heart

d. causes congestive heart failure

e. it damages the cerebral blood vessels

Term
How can one moderate lifestyle in the treatment of hypertension?
Definition
a. cease smoking

b. moderate alcohol intake

c. weight reduction

d. programmed exercise

e. a reduction in salt intake

f. a diet high in potassium ion

Term
What are some medications for hypertension?
Definition
1. diuretics to increase urine volume

2. beta-blockers to decrease the HR

3. Calcium antagonists to block calcium ion channels (decrease response to stress)4. ACE inhibitors to inhibit the conversion to angiotensin II

5. Angiotensin II receptor antagonists

Term
What causes hypovolemic shock?

What are some compensations made?

Definition
Low blood volume causes a decreased CO and blood pressure

Compensations are tachycardia and vasoconstriction of the GI tract, the skin, kidneys, and muscles

Also the kidneys stimulate the production of the renin-angiotensin-aldosterone system resulting in vasoconstriction

an increase in ADH also occurs

Term
What is septic shock?

How does it occur?

How is it treated?

Definition
Dangerously low BP as a result of sepsis

It occurs through the action of baterial endotoxins that activate NO and cause vasodilation

It is treated with drugs that inhibit the production of NO

Term
Describe congestive heart failure
Definition
Cardiac output is insufficient to maintain the blood flow needed by the body

There is increased venous volume and pressure

Term
What causes CHF?
Definition
a. myocardial infarction

b. congenital defects

c. hypertension

d. aortic semilunar valve stenosis

e. disturbed potassium and calcium ion concentrations

Term
What are the compensations to CHF?

What are the treatments?

Definition
Compensations are tachycardia and vasoconstriction of the GI tract, the skin, kidneys, and muscles

Also the kidneys stimulate the production of the renin-angiotensin-aldosterone system resulting in vasoconstriction

an increase in ADH also occurs

CHF is treated with digitalis, vasodilators, and diuretics

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