1: Cardiac Physiology and Neural Control Flashcards
Describe myogenic rhythm
Each myocyte depolarized at a set rate unless altered by the CNS, does not need neural input to fire
With the SA node in control, what is typical HR?
60-100 bpm
With the AV node in control, what is typical HR?
40-60 bpm
With the Purkinje system in charge, what is typical HR?
20-40 bpm
What mediates the strength and rate of heart innervation?
Instrinsic: ANS
Extrinsic: toxin, heart, etc
What is a positive inotropic effect?
Increase strength of contraction
What is a positive chronotropic effect?
Increase HR
What effects does the sympathetic nervous system have on the heart?
Increase strength of contraction and HR
What does the sympathetic nervous system have the most influence over in terms of cardiac function?
On the speed and response to exercise/maximum output
What type of receptors allow there to be a sympathetic effect on the cardiovascular system?
Beta receptors
Where do you find beta 1 receptors?
Cardiac and renal tissue
Where do you find beta 2 receptors?
Smooth muscles of vascular beds
Where do you find beta 3 receptors?
Adipocytes
What is the role of the vagal nerve?
Keep HR lower at rest and to speed recovery after exercise
What three effects does the parasympathetic nervous system have on the cardiac system?
- Decrease strength of atrial contraction
- Decrease HR
- Slow conduction at AV node
What receptors are responsible for parasympathetic control?
Alpha receptors
Where are alpha 1 receptors found?
Smooth muscles
Where are alpha 2 receptors found?
Adrenergic synapses to regulate release of norepinephrine
What catecholamines are circulating and where are they produced?
Epinephrine and norepinephrine - produced in adrenal gland to increase strength of blood
Describe free floating catecholamines
In blood stream waiting to bind to beta receptors to trigger sympathetic response. Will be replenished by sympathetic nervous system
What are baroreceptors?
Stretch receptors in large arteries to induce vagal response and decrease pressure
At what pressure are baroreceptors stimulated?
Arterial pressures of > 60 mmHg
What happens once baroreceptors are stimulated?
Vasodilation or decreased HR, decreased strength of contraction
What is the Starling effect?
Increased venous return causes increase strength of contraction
What is the Anrep effect?
Increased aortic pressure causes increase strength of contraction
What is the Bowdich effect?
Starling or Anrep causes increase in HR
Describe the resting potential for myocardial cells
Slightly negative
What two mechanisms assist with letting Na enter the cell?
- Sodium-potassium pump
- Sodium-calcium pump
Describe the cells permeability to Na with depolarization?
Greater permeability
Describe the cells permeability to Na with repolarization?
Less permeability
What is the effect of high concentrations of Ca2+
Influences actin myosin attraction increasing the strength of the contraction and increase permeability of cell wall to Na
