Lecture 34 Flashcards
describe the structure of the vein
Thin walled
Little smooth muscle (not very contractile; small myogenic response)
Less elastic tissue and more fibrous collagen (poor recoil)
Valves prevent backflow
Muscle PUMP propels blood against gravity
do veins operate in high or low pressure
Veins operate at low pressure
do arteries operate in high or low pressure
Arteries operate at high pressure
Why veins are more compliant than arteries?
thin-walled
large diameter
minimal matrix proteins (poor recoil with low [elastin])
Sympathetic stimulation causes
vaso/veno constriction by binding to alpha 1 receptors → increases pressure → decreases volume
Sympathetic inhibition causes
aso/veno dilation → decreases pressure → increases volume
how does venous pressure affects stroke volume
Venous pressure can affect stroke volume, as changes in venous pressure can impact the filling of the heart and the amount of blood that the heart pumps out with each beat.
In general, an increase in venous pressure can result in an increase in stroke volume, as more blood is able to flow into the heart due to the increased pressure gradient. This is because an increase in venous pressure can lead to greater venous return, or the amount of blood that flows back to the heart from the veins.
Conversely, a decrease in venous pressure can result in a decrease in stroke volume, as less blood is able to flow into the heart due to the decreased pressure gradient. This is because a decrease in venous pressure can lead to reduced venous return.
Venous pressure determines venous return through:
Increase in sympathetic activity
Increase in blood volume
Muscle pump
Inspiration; inhale pulls blood up into heart, exhale inhibits blood from coming out of the heart
Factors regulating venous return:
Blood volume: The amount of blood in the body can affect venous return. An increase in blood volume leads to an increase in venous return, and a decrease in blood volume leads to a decrease in venous return.
Skeletal muscle pump: The contraction of skeletal muscles during physical activity can help to squeeze blood from the veins back towards the heart, increasing venous return.
Respiratory pump: During inspiration, the diaphragm moves downward and increases the pressure in the abdominal cavity, which pushes blood from the abdominal veins towards the heart, increasing venous return.
Gravity: The effect of gravity can also impact venous return. When standing upright, blood pools in the veins of the lower extremities, which can decrease venous return. However, the skeletal and respiratory pumps help to counteract this effect.
what is the #1 homeostatically regulated variable in your body
Mean Arterial Pressure
what is the Baroreceptor reflex:
baroreceptors are specialized stretch receptors located in the walls of blood vessels, particularly in the carotid sinus and aortic arch
They detect changes in blood pressure and send signals to the brainstem, which in turn signals the ANS to adjust heart rate, contractility, and blood vessel tone to maintain blood pressure within a narrow range.
explain how the baroreceptor reflex works:
The baroreceptors are specialized sensory receptors located in the walls of blood vessels, particularly in the carotid sinus and aortic arch. These receptors detect changes in blood pressure, specifically changes in stretch of the vessel walls.
When blood pressure increases, the baroreceptors are stretched and send signals to the brainstem, specifically the medulla oblongata.
The medulla oblongata processes these signals and sends inhibitory signals to the sympathetic division of the ANS, which reduces sympathetic nerve activity and promotes parasympathetic nerve activity.
The parasympathetic division of the ANS reduces heart rate, contractility, and vascular tone, leading to a decrease in blood pressure.
When blood pressure decreases, the baroreceptors are less stretched, and send signals to the medulla oblongata to increase sympathetic nerve activity and decrease parasympathetic nerve activity.
The sympathetic division of the ANS increases heart rate, contractility, and vascular tone, leading to an increase in blood pressure.
