Flashcards in Acute Cardiovascular responses to exercise Deck (16):
What relationship do muscle blood flow and exercise intensity have?
- Linear relationship - Exercise intensity increases so does muscle blood flow
How does the motor cortex influence exercise response?
- Activates sympathetic neurons in hypothalamus
- Vagus nerve fibres slow heart rate and conduction velocity through action of ACh at SA and AV nodes
- Efferent sympathetic fibers increase heart rate and myocardial contractility and dilate cornory arteries
How does sympathetic nervous stimulation of adrenal medulla effect exercise?
- Epinephrine delivered accelerates SA node discharge, dilates coronary vessels, and increases myocardial metabolism
What can to heart rate responses after a transplant?
- No anticipatory rise from sympathetic neurons in hypothalamus
- No vagus nerve parasympathetic stimulation so starts higher also
What is the fick equation and how can this be rearranged?
- VO2 (max)= Cardiac output (max) x Arterial-Mixed venous O2 concentration
- Cardiac output= VO2/Arterial-Venous 02 difference
What factors contribute to the increase seen in stroke volume, cardiac output and heart rate seen with exercise
- More calcium released-stronger contraction
- Phosphorylation to troponin C cardiac muscle relaxes more quickly
- Higher negative pressures from increase VE increases venous return
- Atria contraction increases giving higher preload and higher SV
What factors of local control influence where blood goes?
Vasodilator stimuli stop sympathetic tone from having action
- Increase local adenosine
- Fall in local pH
- Elevated local potassium (increased work of sodium potassium pump)
- Elevated local CO2
- Decreased local O2
- Increased nitric oxide
Outline the different types of receptors and what there effect is upon stimulation
- Alpha A1 - Contraction of smooth muscle
- Alpha A2 - Vasoconstriction
- Beta B1: Chronotropic and Inotropic action at heart/ Stimulates renin release
- Beta B2: Smooth muscle relaxation (bronchioles)/ Dilates vessels in heart, liver and skeletal muscle
- Beta B3: Stimulates lipolysis
Activates smooth muscle
How does exercise training effect blood vessels?
- Increase in number of blood vessels
- Blood vessels become more responsive to sympathetic tone
Outline the process that leads to an increased dilation of blood vessels
1) Acetylcholine activates G protein linked receptor activating IP3 receptors
2) IP3 receptors activate calcium release from endoplasmic rectilium
3) Calcium binds to calmodulin activating nitric oxide synthase
4) Nitrc oxide synthase converts Arginine to Citrulline and Nitric oxide
5) Nitric oxide activates - Guanyl cyclase
6) Guanyl cyclase converts GTP to cyclic AMP
6) Cyclic AMP activates protein kinase G causing muscle relaxation and dilation of blood vessels
What is the effect of L-name on contraction?
- Femoral vascular conductance from exercise changes back to that of sedentary individual
- Reductions in vascular conductance associated with higher sympathetic nerve activity and decreased blood flow
- L-name inhibits NO synthase and therefore blood flow through vasodilation
Why is VO2 max of one legged exercise about 75% of two legged exercise?
- Can't vasodilate all blood vessels fully in both legs otherwise reduction in blood pressure would be too large
How does blood distribution change during exercise?
- Increased cardiac output from 5 to 25 l/min
- Increased blood flow to brain and heart but about the same percentage
- Decreased to gut liver bone through vasoconstriction
How does blood pressure change with exercise?
- Mean arterial pressure increases through increases in systolic pressure to increase SV
- Diastolic pressure stays the same or decrease with pooling of blood
Describe how blood pressure is increased if falling below normal range?
1) Baroreceptors are inhibited
2) Vasomotor centre stimulated
3) Vasoconstriction occurs and BP elevates
1) Cardioinhibitory centre is inhibited
2) Cardioacceletory centre is stimulated
3) Cardiac ouput increases and blood pressure increases