CardioPhys- Nordgren Flashcards
What are two ways to calculate mean arterial pressure?
MAP = CO x TPR
MAP = 2/3diastolic + 1/3systolic
A person’s arterial blood pressure abruptly changes from 120/90 to 140/80 while their heart rate changes from 70 to 140. What has happened to their MAP?
What are the three ways you can calculate flow?
Fick equation = (rate of consumption)/(arterial concentration - venous concentration
Q= deltaP/R
CO = HR x SV
(SV = EDV - ESV)
How does smooth muscle differ anatomically and funcitonally from striated muscle? (skeletal and cardiac)
- VSM contracts and relaxes more slowly
- VSM can change contractile activiey as a result of either action potentials or changes in resting membrane potential
- VSM can contractile activity in the absence of any changes in membrane potential
- Can maintain tension for prolonged periods at low energy cost
- Can be activated by stretch
Describe the contractile process of vascular smooth muscle
- Calcium binds calmondulin
- This complex activates MLCK
- MLCK uses ATP to phosphorylate MLC
- MLC phosphorylation enables cross-bridge formation & cycling
What regualtes contractility of smooth muscle?
VSM contractility depends on the NET STATE of MLC phosphorylation
What is the most important factor in monitoring blood flow of the splanchnic blood flow, renal blood flow, and cutaneous blood flow?
Sympathetic neural activity!
What is the most important regulator of blood flow to the heart, skeletal muscle and brain?
Local metabolic control!
Heart = myocardial O2 consumption
Lungs = cardiac output and hypoxic influences
When an organ response to an increase in metabolic activity with a decrease in its arteriolar resistance, this is known as…
Active hyperemia
Seen in organs with highly variable metabolic rate (like skeletal and cardiac muscles) the blood flow closely follows the tissues metabolic rate.
What is reactive hyperemia?
higher-than-normal blood flow occurs transiently after the removal of any restriction that has caused a period of lower-than-normal blood flow
Somtimes referred to as postocclusion hyperemia
What does steady state mean in regards to the cardiac function vs. venous return curve?
In a steady state the caridac output is equal to the venous return
In what to circumstances would the venus return curve shift to the left?
Decreased blood volumne
Decreased venous tone
In what circumstances would the venus return curve shift to the right?
Increased blood volume
Increased venous tone
What would make the cardiac function curve shift left/upward?
Increased cardiac sympathetic nerve activity
What approaches might a physician logically pursue in an attempt to lower a patients cardiac preload?
Because cardiac preload IS central venous pressure, the physician will try to lower central venous pressure. This requires a left shift of the venous return curnve.
- Decrease circulating volume (diuretic drugs)
- Decrease venous tone (vasodilator drugs)
Define iontrope
+ = increases contractility
- = decreases contractility
Dromotrope
+ increases conduction speed in the AV node
- decreases conduction speed in the AV done
Chronotrope
+ increases HR
- decreases HR
Define Lusitrope
+ increased myocardial relaxation
- decreased myocardial relaxation
Describe the phases of the action potential for contractile cells
Fast Respose Curve
Uses Na+ for depolarization
Phases 4, 0, 1, 2, 3, 4
Describe the phases of the action potential for pacemaker cells.
Slow response
Ca for depolarization
4, 0, 3, 4
What happens when an intervention promotes early activation of delayed rectifier K+ channels in cardiac muscle?
The action potential duration is DECREASED (does not affect amplitude)
What are normal pressures for the chambers of the heart?
Right atrium = <5
Right ventrical = 25/5
Pulmonary artery = 25/10
Left atrium = < 12
Left ventricle = 130/10
Aorta = 130/90
Why is baroreceptor firing not useful in long term regulation of arterial blood pressure?
baroreceptor firing rate adapts to prolonged chnages in arterial pressure
Why is the baroreceptor reflex useful? Describe the reflex
It is essential for counteracting rapid changes in arterial pressure
Arterial baroreceptors = mechanoreceptors that sense arterila pressure via “stretch” of arterial walls
Located in walls of aorta and carotid arteries
Active at normal pressures and supply a tonic signal
Baroreceptors –> cardio center in medulla –> efferent sympathetic and parasympathetic fibers that affect (HR, tone, contractility, etc)
What happens during the baroreceptor refelct to a decrease in MAP? (as the primary distrubance)
What are the mechanisms for short term and long term control of arterial pressure?
Short term control = baroreceptors
Long term control = RAAS system
Describe the RAAS system
- Decrease in arterial presure
- Kidneys produce Renin
- Renin converts angiotensinogen to angiontensin I
- ACE (on surface on endothelial cells) converts angiotensin I to angiontensin II
- Angiotensin II goes to adrenal gland and stimulates release of aldosterone
- Aldosterone increases Na+ reabsorption by renal tubules
- Increase in fluid retension and volume (decreases urine output)
NOTE* Angiotensin II also stimulates release of ADH (vasopressin) which increases water permeability –> increases BP
All of the following tend to occur when a person likes down. Which one is the primary distrubacne that causes all the others to happen?
A. the heart rate will decrease
B. Cardiac contractility will increase
C. Sympathetic activity will decrease
D. Parasympathetic activity will increase
E. Central venous pressure will increase
E! All the other choices are part of the reflex compensatory responses to the increase in central venous pressure
