Venous Return/BP Regulation Flashcards
Define venous return
the volume of blood flowing back to the heart via the systemic veins
What causes venous return
- The pressure from the L ventricle
- Extravascular pressure (skeletal muscle and respiratory pump)
- Venous valves
True or False the pressure difference between from the venules to the R atria is vey small
True, ~0.1 mm Hg, despite being small it is enough to get blood back to the heart
What happens to venous return when R atria pressure is increased, why does this happen, and give an example
Venous return reduces when R atrial pressure is increased d/t back pressure
ex Tricuspid valve regurgitation
Describe the skeletal pump mechanism
When muscles contract it pushes through the proximal venous valve (milking) and distal valve closes because blood pushes the valve closed
During relaxation the proximal valve closes because of back flow and the distal valve opens because of BP to allow blood to move forward
Describe the respiratory pump mechanism
During inhalation= diaphragm moves downward causing thorax pressure to decrease but abd pressure to increase, resulting in blood being pushed to the thorax cavity/towards the heart
During exhalation= diaphragm moves upward causing thorax pressure to increase and abd pressure to decrease, resulting in thoracic valves closing preventing backflow into the abd
What is BP determined by
- cardiac output
- vascular resistance
- blood volume
True False BP stays the same throughout at parts of the circulatory system
False, BP progressively decreases the further you get away from the L ventricle
What ways can the body adjust BP
By negative feed back systems that change HR, SV, systemic vascular resistance, or blood volume
Where is the cardiovascular center located
The medulla oblongata
What does the cardiovascular center control
neural and hormonal systems that regulate HR, contractility, and blood vessel diameter
What is the function of the cardio-stimulatory center in the CV center
neurons that stimulate the heart, cardiac accelerator nerves arise from here
What is the function of the cardio-inhibitory center in the CV center
neurons that inhibit the heart, cardiac vagus nerves arise from here
What is the function of the vasomotor center in the CV center
controls vaso dilation and vasoconstriction
How does the higher brain centers of the cerebral cortex and limbic system affect HR
Think before starting a race your HR increases
How does the sympathetic nerves of the autonomic system affect cardiovascular system
Increase HR, contractility, and controls diameter of arteries/arterioles
-Continually sends impulses to the arteries/arterioles to create vascular tone. A reduction in these impulses reduces vascular tone
How does the parasympathetic nerves of the autonomic system affect cardiovascular system
Decreases HR and contractility
-remember no parasympathetic control in systemic vasculature
What is the role of baroreceptors in regulating BP
pressure (stretch) sensitive sensory receptors that sense BP for feedback to the CV center
Where are BP baroreceptors located
aorta, internal carotid arteries, and other large vessels of the neck and chest.
What are the 2 most important baroreceptor reflexes
- Carotid sinus reflex
2. Aortic reflex
What is the function of the carotid sinus reflex
Helps regulates BP in the brain
Describe the path a nerve impulse travels from the carotid sinus to the CV center
Nerve impulses propagate from the carotid sinus baroreceptors over the glossopharyngeal nerve (cranial nerve IX) then to the CV center
Where is carotid sinus located
In-between where the R and L internal carotid arties branch from the R and L common carotids
What is the function of the aortic reflex
helps regulates systemic BP
