Flashcards in chapter 21 physiology, muscle blood flow and cardiac output during exercise; coronary circulation and ischemic heart disease Deck (45)
how fast does blood flow through skeletal muscle during rest?
3-4 ml/min/100g of muscle
besides adenosine acting as a vasodilator during exersize, what else causes vasodilation?
potassium ions, adenosine triphosphate, lactic acid, carbon dioxide
what 3 main affects occur during excersize that are essential for circulatory system to supply alot of blood to the muscles?
1.. mass discharge of sympathetic nervous sustem throughout the body
2. increase in arterial pressure
3. increase in cardiac output
what 3 things cause increase in arterial pressure during excersize?
1. vasoconstriction of arterioles and small arteries in most tissue (except active muscles)
2. increased pumping by heart
3. increase in mean systemic filling pressure caused by venous contraction
what happens with the vessels inside the muscles as they contract?
they vasodilate, everywhere else vasoconstricion occurs
why is the arterial pressure increase during exercise so important?
it allows up to 20 times more blood flow to the muscles
what do almost all elderly people have some sort of?...
coronary artery disease
what vessel supplies the heart with nutrients?
left coronary artery suppies what part of the heart?
anterior and leftlateral portions of the left ventricle
right coronary artery supplies what?
most of the right ventricle, as well as the posterior part of the left ventricle in 80-90 percent of people
where is the Coronary sinus
where the coronary arteries empty into the right atrium
thebesian veins do what?
a small amount of venous blood also flows back into the heart throuogh these veins
the resting coronary blood flow is what percent of the total cardiac output?
describe the capillary blood flow through the left ventricle during systole
the blood flow falls during systole while the blood flow in the capillaries through out the body rises
how is the coronary system regulated?
by the nutritional need of the cardiac muscle. So when the heart needs to pump harder, the coronary vessels dialte
describe adenosine's role in vasodilation in regards to ATP
muscles use ATP which turns into Adenosine monophosphate which is degraded into adenosine which causes vasodilation
name some other vasodilators
adenosine phoshpate compounds, potassium ions, hydrogen ions, carbon dioxide, prostaglandins, nitric oxide
what does sympathetic stimulation release?
noreepinephrine and epinephrine
what does the parasympathetic stimulation release?
what does epinephrine and noreepinephrine do in the coronary vessels?
they actually have dilator and constrictor receptors. The constrictor receptors are called alpha receptors and the dilator receptors are called beta receptors
what happens if the alpha receptors are over stimulated?
Angina can occur and ischemia can occur
while at rest, from which molecule does the heart get its nutrients?
what causes anginic pain in anaerobic conditions?
with lack of O2 the heart tissue performs anaerobic respiration which produces lactic acid. This is whats though to cause angina during ischemia.
what is the most frequent cause of diminished coronary flood flow and where does it most oftenly occur?
atherosclerosis, most frequently in the first few cm of major coronary arteries
name one way to have acute coronary occlusion
thrombus development. ( a flowing thrombus is called an embolus)
name another way to have acute coronary occlusion
mucsular spasm of coronary artery which can develope a secondary thrombus
describe the collateral development of vessels and the coronary artery
Collateral vessels develop if the coronary constriction is slow over a period of years. They grow to compensate for atherosclerosis. Even the collateral vessels can develope atherosclerosis and the heart becomes weak and has a low output. ( this is one of the most common causes of cardiac failure)
what is myocardial infarction?
heart muscle has zero flow
requirements for cardiac muscle to stay alive
1.3 ml of oxygen per 100 g