Lecture 14 - Cardiac Output and Blood Flow in Muscle Tissues Flashcards
Define cardiac output.
(slide 4)
- quantity of blood pumped into aorta each minute
- quantity of blood that flows through circulation
- sum of all the blood flows to all body tissues
What is cardiac index?
slide 4
- cardiac output per square meter of body surface
- decreases with age
-normal cardiac index is 3 L/min/M^2
What is the main factor that affects cardiac output?
-venous return
How does Ohm’s law relate to cardiac output?
slide 15
-long-term peripheral resistance changes cause an inverse change in cardiac output
Differentiate between Bainbridge reflex and baroreceptor reflex.
(slide 16)
Bainbridge:
-stretching of the right atrium increases heart rate
Baroreceptor:
-increased pressure in the aorta/carotid increases heart rate
How does the Frank-Starling law relate to cardiac output?
-the heart pumps out the amount of blood that flows into the right atrium
What factors cause a hypereffective heart? (3)
slide 19
- nervous stimulation
- hypertrophy of the heart
- exercise (large vein contraction which increases venous return)
What factors cause a hypoeffective heart? (7)
slide 20
- hypertension
- inhibition of nervous excitation
- pathologic factors
- coronary artery blockage
- valvular disease
- congenital heart disease
- cardiac hypoxia
What are cardiac factors that result in decreased cardiac output? (5)
(slide 22)
- severe blockage of blood vessels (MI)
- severe valvular disease
- myocarditis
- cardiac tamponade
- cardiac metabolic derangements
What are non-cardiac factors that result in decreased cardiac output? (5)
(slide 22)
- decreased blood volume
- acute venous dilation
- obstruction of large veins
- decreased tissue mass
- decreased metabolic rate of tissues
What is the mean systemic filling pressure?
- the pressure of blood flowing into the atrium through the vena cava
- 7 mmHg
What is pressure gradient for venous return and what affect does it have on venous return?
- difference between mean systemic filling pressure and right atrial pressure
- high pressure gradient results in increased venous return
What is the formula for venous return?
-(mean systemic filling pressure - right atrial pressure) / resistance to venous return
What happens to venous return when right atrial pressure is less than -2?
Greater than +7?
- venous return plateaus below -2 because veins in the chest collapse
- venous return is 0 when right atrial pressure is +7 because mean systemic filling pressure is canceled out
What affect does strong sympathetic stimulation and complete sympathetic inhibition have on venous return?
(Slide 33-35)
- strong sympathetic stimulation constricts all blood vessels increasing mean systemic filling pressure
- inhibition causes relaxation of all blood vessels and decreases mean systemic filling pressure
What factor result in an increase in mean systolic filling pressure? What affect does this have on the venous return curve?
Increase in vascular volume:
-activation of renin-angiotension-aldosterone system
Decrease venous compliance:
- sympathetic stimulaion
- muscle pump
- exercise
- lying down
Shifts venous return curve to the right
What factor result in an decrease in mean systolic filling pressure? What affect does this have on the venous return curve?
Decrease vascular volume:
- hemorrhage
- burn trauma
- vomiting
- diarrhea
Increase venous compliance
- inhibition of sympathetic stimulation
- alpha block
- venodilators
- standing upright
Shifts venous return curve to the left
What are factors affecting local control of skeletal muscle?
Slide 51
- oxygen
- adenosine
- potassium ions
- ATP
- lactic acid
- carbon dioxide
What are nervous controls of blood flow regulation to skeletal muscle?
(Slide 51)
Sympathetic vasoconstrictor nerves:
- secrete norepinephrine
- decrease blood flow
Adrenal medullae:
-secretes norepinephrine and epinephrine
What changes to blood flow to skeletal muscle occurs during mass discharge of the sympathetic nervous system during exercise?
(Slide 52)
- heart rate increases
- most peripheral arteries are strongly contracted except: in active muscle, coronary arteries, and cerebral arteries
- muscle walls of vein are contracted
In general, blood flow through vessels to a muscle ___________ during contraction and __________ during relaxation.
Decreased; increases
What factors affect blood flow in the coronary arteries?
- muscle metabolism of the heart
- ANS stimulation on coronary vessels
- ANS stimulation on the heart
