Lecture 11 Flashcards
What is the primary functions of the CVS during exercise?
Deliver O2 to muscles
Remove CO2 and heat from muscles
Why is there an increase in muscle blood flow during exercise?
vasodilator metabolites dilate vessels to the muscle.
muscle pump increases cardiac return and stroke volume.
Why is there an increase in cardiac output during exercise?
Increased HR and SV
How is circulation controlled during exercise?
Key receptors interact with autonomic nervous system and feedback from contracting muscles takes place.
What are some adaptations of the CVS to exercise?
Enhances stroke volume
Promotes skeletal muscle angiogenesis
What is Fick’s equation of oxygen consumption?
VO2 = Qx(CaO2-CvO2)
How is Mean Arterial Pressure maintained?
Mean Arterial Pressure is maintained during exercise by manipulating the Cardiac output and the TPR.
How is the sudden drop in TPR during exercise counteracted?
Decrease in splanchnic and renal blood flow increases TPR.
Increased cardiac output is done via increased Heart Rate.
What happens to coronary blood flow during exercise?
Heart increases oxygen extraction
What causes exercise hyperemia?
Metabolic vasodilators from contracting skeletal muscle, endothelium, and RBC.
Muscle pump (important in maintaining venous return)
Conducted Vasodilation
Functional sympatholysis
What is exercise hyperaemia?
Increase in blood flow during exercise
What is Conducted Vasodilation?
The phenomenon where vasodilation action potential is conducted via gap junctions into arterioles which contract and cause vasodilation.
What is functional sympatholysis?
The sympathetic nerve activity is blunted by the muscle.
What are the known vasodilator metabolites?
K+, H+, adenosine, ATP (seen from RBCs)
ROS
NO, prostacyclin, prostaglandin E2
Endothelial derived hyperpolarising factor
What adaptation do athletes’ hearts have to exercise?
Athletes have a higher stroke volume which is a result of lower heart rate during exercise.
What are the 3 types of blood pressure?
Diastolic blood pressure is determined by resistance.
Systolic blood pressure increases during exercise
Mean arterial pressure is the weighted average of systolic and diastolic BP. During exercise it increases.
What is the baroreceptor reflex?
Baroreceptor reflex modifies heart rate in response to changes in blood pressure. The ‘set point’ which blood pressure stays at is different during exercise.
What causes the change in set point during exercise?
baroreceptor is reset by central command.
How does the cardiac output change over time?
Cardiac output doesn’t increase linearly and eventually decreases rate of increase.
What is CV drift?
CV drift is the increase in HR and drop in SV during prolonged exercise.
What are the causes of CV drift?
Hyperthermia (SA node depolarizes more rapidly)
Dehydration (decreased blood volume)
Increase in plasma adrenaline
Cardiac output decreases due to loss of blood volume and blood displacement to the skin.
What other phenomenon does the CV drift contribute to?
The VO2 drift
What can a person do to decrease cardiac drift?
Increase blood volume by drinking water.
What is the function of the peripheral sensors of the exercise response?
They send sensory feedback messages to the brain in response to exercise.
What are the peripheral receptors?
Baroreceptors
Muscle Chemoreceptors
Muscle Mechanoreceptors
What are the components of the central motor systems?
The motor cortex
Subthalamus
Spinal motor systems.
What is the functions of the central motor systems?
They are involved in the feedforward response.
They are the responders to the peripheral sensors.
How does the autonomic nervous system increase the heart rate?
Rising heart rate is initially due to withdrawal of the vagus but then continued by the sympathetic nerve influence.
What are the cardiovascular adaptations to exercise?
Heart size can be increased from exercise. The capillary density at muscles can be increased as well.
During exercise blood volume increases
