Coordinated Cardiovascular Responses- Gravity And Exercise Flashcards
What is orthostasis?
Fancy word for standing up
What happens when you first stand up?
Blood pressure falls at first
Postural hypotension, lack of blood flow to the brain- might feel faint
What are the three smaller changes that take place to recover your blood pressure?
Increased heart rate, contractility and total peripheral resistance
What is Bernoulli’s law?
Blood flow = pressure + potential energy + kinetic energy
What does Bernoulli’s law mean?
Increased potential energy at heart vs feet + increased kinetic energy of ejected blood
What is the high pressure in the venous system at the feet due to?
Hydrostatic pressure
What happens to the blood in the veins when lying down?
Blood is evenly distributed in veins -> increased central venous pressure -> increased end diastolic volume -> increased stroke volume -> increased cardiac output
What happens to the pressure in the veins when standing up?
Blood pooling in legs means less blood returning to the heart-> fall in central venous pressure -> decreased end diastolic volume -> decreased stroke volume-> decreased cardiac output-> poor perfusion of the brain
What 5 things make postural hypotension worse?
Alpha adrenergic blockade Varicose veins Lack of skeletal muscle activity Reduced circulating blood volume Increased core temperature
How do varicose veins make postural hypotension worse?
Impairs venous return
What are the short term effects of microgravity on the cardiovascular system?
Increased atrial/ventricular volume, preload and cardiac output
What is reduced short term in microgravity?
Sympathetic activity
ADH
RAAS
How much does blood volume reduce in microgravity?
20%
What are long term effects of space on the cardiovascular system?
Less blood volume
Less stress on heart
Heart reduces in muscle mass
General drop in BP
What happens to space people on return to gravity?
Severe postural hypotension due to too much lower blood volume and a small heart. Baroreceptors reflex cannot compensate
What is dynamic movement?
Constant shortening and relaxing with lots of different muscle groups involved
What is static exercise?
One specific muscle group is being worked without constant movement
What happens once exercise starts (in the CV system)?
- Increased lung oxygen uptake, transport around the body and supply to exercising muscle
- control BP
- coordinate dilator/ constriction of vascular beds to target areas where oxygen is delivered
How much can oxygen uptake by pulmonary circulation increase by during strenuous exercise?
10-15 times
Will stroke volume increase exponentially?
No- it reaches a plateau
What happens in exercise induced tachycardia?
Brain central command is alerted by muscle mechanoreceptors
The vessels in the muscle dilate
Sympathetic activity in the heart increases
Vagal tone decreases
What happens in exercise induced increased end diastolic volume?
Increased venous return/ CVP through venoconstriction
Increased sympathetic activity and calf muscle pump
Activates starlings law and increases preload
How does faster ejection help in exercise?
Increased contractility by sympathetic activation of beta 1 receptors
What is the central control of the CV system during exercise?
RVLM controls specific pre-ganglionic sympathetic nerves in the spinal cord which sends out post-ganglionic nerves to specific tissues
How is hypotension prevented during exercise?
Compensatory vasoconstriction of non-essential circulations prevent hypotension due to exercise, which induces decreased TPR
What happens in static exercise?
Small increase in heart rate and large increase in blood pressure
What are the changes due to in static exercise?
The constant contraction of small number of muscles leads to a high load.
The contracted muscle stops the vessels dilating so the rest of the body’s BP increases to push the blood through
How does the blood pressure stay relatively constant in dynamic exercise?
Due to the shortening/ lengthening of many muscles = low load
What does chemosensitive mean?
Stimulated by potassium, hydrogen and lactate, which increase in exercising muscle
What are the reflex effects of metaboreceptors?
Tachycardia, increased blood pressure, pressor response, raised BP and dilated vessels
When is the pressor response especially important?
During isometric exercise. Static exercise raises BP more than dynamic exercise
