RAT 8 Flashcards
why is blood pressure so tightly regulated?
in order to constantly meet the body’s blood flow needs
which branch of the nervous system is primarily responsible for changes in blood pressure?
autonomic nervous system (sympathetic and parasympathetic NS)
describe how the sympathetic changes leads to changes in blood pressure.
- increase in heart rate and contractility which leads to increased cardiac output
- vasoconstriction of arterioles which increases peripheral resistance
which hormones are released onto the target organs in the sympathetic NS?
- epinephrine
- norepinephrine
describe how the parasympathetic nervous system leads to changes in blood pressure.
- slows heart rate, mild effect on contractility which decreases cardiac output and blood pressure
- vasodilation and decrease in peripheral resistance
what neurotransmitter is released by the vagus nerve?
acetylcholine
what is the major cranial nerve in the parasympathetic nervous system?
vagus nerve
what impact will acetylcholine have on the heart?
slows heart rate and effect contractility mildly
does the parasympathetic nervous system innervate blood vessels?
no
explain how the parasympathetic nervous system impacts blood pressure if it does not innervate blood vessel.
autonomic centers in the brainstem increase the firing of parasympathetic neurons while inhibiting the firing of sympathetic neurons
what are the receptors that detect blood pressure?
baroreceptors
where are baroreceptors found?
- within the vessels
- common carotid artery and aortic artery
what hormone is a potent vasoconstrictor that increases blood pressure?
angiotensin II
what hormone is released by the heart and lowers blood pressure
atrial nutriuretic peptide (ANP)
which system is responsible for long-term maintenance of blood pressure?
urinary system
which hormones affect blood volume and how do they affect it?
- ANP: causes kidneys to excrete more water and sodium to decrease blood volume
- angiotensin-II: induces thirst, sodium retention, increases blood volume
- ADH: triggers thirst and increases water retained by kidneys to increase blood volume
- aldosterone: causes retention of sodium and water from the kidneys, increases blood volume
how do the kidneys influence blood pressure maintenance?
- blood pressure increases, more water flows through the kidneys than the cells can return to blood, water is then loss through urine
- blood pressure decreases, less water through the kidney and cells have more time to reclaim water and return it to the blood, decrease urine production and increase in blood volume and blood pressure
define perfusion
blood flow to a tissue through a capillary bed
how is perfusion different from blood flow?
it goes through a capillary bed
what is the name of the cells that form capillary walls?
pericytes
define capillary exchange
the movement of nutrients, gases, ions, and wastes between the blood in the capillary and the tissue cells
what are the three ways substances are exchanged?
- diffusion and osmosis through gaps and fenestrations
- diffusion through the membranes of endothelial cells
- transcytosis
what substances are exchanged in diffusion and osmosis through gaps and fenestrations?
water, monosaccharides, amino acids
what substances are exchanged in diffusion through the membranes of endothelial cells?
oxygen, carbon dioxide, certain lipids
what substances are exchanged in transcytosis?
larger substances
what are the three types of capillaries?
- continuous capillaries
- fenestrated capillaries
- sinusoidal capillaries
what distinguishes a continuous capillary?
tight junctions
what distinguishes a fenestrated capillary?
fenestrations
what distinguishes a sinusoidal capillary?
irregular basal lamina, large pores, spaces between endothelial cells
what are two examples of local regulation of tissue perfusion?
- myogenic mechanism
- metabolic controls
explain how the myogenic mechanism helps maintain tissue perfusion at a constant level.
myogenic mechanism alters arteriolar resistance so if resistance increases, viscosity decreases. myogenic mechanism slows blood flow by increasing resistance when arteriolar pressure rises and speeds up blood flow by decreasing resistance when arteriolar pressure decreases. both changes maintain local tissue perfusion at a constant level
explain how metabolic controls help maintain tissue perfusion
when the muscle relaxes the arterioles dilate which increase perfusions and ensures adequate oxygen and nutrient delivery to active metabolizing cells. it can also work in the opposite way
in a capillary, what are the two basic pressures that drive water movement?
- hydrostatic pressure
- osmotic pressure
what is hydrostatic pressure (HP)?
the force that a fluid exerts on the wall of its container
what is a hydrostatic pressure gradient?
when the pressure is higher in one compartment than in another compartment
what is filtration?
movement of a fluid by a force such as hydrostatic pressure or gravity
what is the colloid osmotic pressure (COP) or oncotic pressure?
the difference in osmotic pressure between the blood and interstitial fluid
what is the net direction of water movement at the arteriole end of the capillary?
water leaves the capillary by filtration
what is the net direction of water movement at the venous end of the capillary?
water enters the capillary by osmosis
what is the net filtration pressure at the arteriole end of a capillary?
13 mm Hg
what is the net filtration pressure at the venous end of a capillary?
-7 mm Hg
what is the overall net filtration pressure?
6 mm Hg
how much water leaks out of capillaries each day?
2-4 liters
what happen to the water that leaks out?
lost from the blood to the interstitial fluid but eventually returned to the blood by vessels of the lymphatic system
what is edema?
excessive amount of water in the interstitial fluid
an increase in which pressure would favor edema?
capillary hydrostatic pressure
