objective 4 Flashcards

1
Q

what are the 2 main neural mechanisms control peripheral resistance?

A

MAP is maintained by altering blood vessel
diameter, which alters resistance
– Example: If blood volume drops, all vessels constrict (except those to
heart and brain)
2. Can alter blood distribution to organs in
response to specific demands
– Example: during exercise blood is shunted temporarily from
digestive organs to skeletal muscles.

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2
Q

what do neural controls operate via reflex arcs that involve what?

A

Cardiovascular center (medulla)
◦ Baroreceptors (changes in pressure)
◦ Chemoreceptors (changes in chemical messengers)
◦ Higher brain centers (hypothalamus)

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3
Q

composed of sympathetic neurons in medulla

A

cardiovascular center

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4
Q

cardioinhibitory and cardioacceleratory
centers

A

cardiac centers

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5
Q

cause continuous moderate constriction called vasomotor tone

A

vasomotor center

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6
Q

what happens if MAP is high?

A

Increased blood pressure stimulates baroreceptors to
increase input to vasomotor center
– Inhibits vasomotor and cardio-acceleratory centers
– Stimulates cardio-inhibitory center
– Results in decreased blood pressure

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7
Q

what are the 2 mechanisms that result in decrease in BP?

A

vasodilation
decreased cardiac output

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8
Q

Decreased output form vasomotor center causes
dilation

A

vasodilation

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9
Q

reduces peripheral
resistance, MAP falls

A

arteriolar vasodilation

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10
Q

shifts blood to venous reservoirs, decreasing
venous return and CO

A

venodilation

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11
Q

impulses to cardiac
centers inhibit sympathetic activity and stimulate
parasympathetic
Reduces heart rate and contractility; CO decrease causes
decrease in MAP

A

decreased cardiac output

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12
Q

what happens if MAP is low?

A

vasoconstriction is initiated that increases CO and
blood pressure
– baroreceptors that monitor BP to ensure enough blood to brain
– maintains BP in systemic circuit
– Baroreceptors are ineffective if altered blood pressure
is sustained (i.e chronic HTN)
– Become adapted to hypertension, so not triggered by
elevated BP levels

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13
Q

Aortic arch and large arteries of neck detect
increase in CO 2 , or drop in pH or O2

A

chemoreceptor reflexes

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14
Q

how does chemoreceptor reflexes increase BP?

A

Signaling cardio-acceleratory center to increase
Cardiac output
– Signaling vasomotor center to increase
vasoconstriction ( so more resistance)
– This causes increase in BP that speeds return of blood
to heart and lungs

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15
Q

Reflexes that regulate BP are found in medulla
oblongata
◦ Hypothalamus and cerebral cortex are not involved
in routine control of BP
◦ Hypothalamus increases blood pressure during
stress
◦ Hypothalamus mediates redistribution of blood flow
during exercise and changes in body temperature
◦ Allows modification of neural controls of BP

A

influence of higher brain centers

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16
Q

how do hormones regulate BP?

A

short-term via changes in peripheral resistance
◦ long-term via changes in blood volume

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17
Q

increase CO and vasoconstriction

A

Epinephrine and norepinephrine

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18
Q

stimulates vasoconstriction

A

Angiotensin II

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19
Q

cause vasoconstriction

20
Q

causes vasodilation
and promotes a decline in blood volume and
therefore BP

A

atrial natriuretic peptide

21
Q

how do kidneys regulate arterial BP?

A

Direct renal mechanism
2. Indirect renal mechanism (renin-angiotensin-
aldosterone)

22
Q

Alters blood volume independently of hormones
– Increased BP or blood volume causes elimination of
more urine, therefore reducing blood volume, thus
reducing BP
– Decreased BP or blood volume causes kidneys to retain
more water, increasing blood volume and BP rises

A

direct renal mechanism

23
Q

The renin-angiotensin-aldosterone mechanism:
– Decreased blood pressure causes release of renin from
kidneys
– Triggers formation of angiotensin II

A

indirect mechanism

24
Q

what do angiotensin II cause?

A

Release of aldosterone stimulating salt and water retention
– Vasoconstriction
– Release of ADH
– Thirst
– * all of these will lead to increased blood volume and BP

25
Determines the distribution of fluids between the bloodstream and the interstitial space } Fluid flows out capillary bed at arteriolar end and re-enters the capillary blood at the venous end – Extremely important in determining relative fluid volumes in blood and interstitial space } Bulk fluid flows across capillary walls causes continuous mixing of fluid between plasma and interstitial fluid; maintains interstitial environment
bulk flow
26
what does direction and amount of fluid flow depend on?
Hydrostatic pressure – Colloid osmotic pressure
27
force exerted by blood pressing against vessel wall/chamber ◦ Primary source driving fluid transport
hydrostatic pressure
28
BP in capillaries that forces fluids through capillary walls; greater at arterial end
capillary hydrostatic pressure
29
pressure pushing fluid back into vessel; usually aim to be 0 as lymphatic vessels drain interstitial fluid
interstitial fluid hydrostatic pressure
30
sucking pressure created by non-diffusible plasma proteins pulling water back into capillary
capillary colloid osmotic pressure
31
opposes hydrostatic pressure
colloid osmotic pressures
32
pressure is inconsequential because interstitial fluid has very low protein content
interstitial fluid colloid osmotic pressure
33
Net filtration pressure (NFP) comprises all forces acting on capillary bed ◦ Net fluid flow out at arterial end ◦ Net fluid flow in at venous end ◦ More fluid leaves at arterial end than is returned at venous end ◦ Excess interstitial fluid is returned to blood via lymphatic system
hydrostatic-osmotic pressure interactions
34
runs from heart to lungs and back to heart
pulmonary circulation
35
to all parts of body and back to heart
systemic circulation
36
share same name with corresponding artery
deep veins
37
do not correspond to names of any arteries
superficial veins
38
Veins can have more than one name, making venous pathways harder to follow
venous pathways are more interconnected
39
contains dural venous sinuses
brain
40
drains into hepatic portal system, which perfuses through liver before returning to heart
venous system of the digestive system
41
runs behind and to right of pulmonary trunk before becoming the aortic arch
ascending aorta
42
branches of ascending aorta that supply the mediastinum
Rt. & Lt coronary arteries
43
deep to sternum. Has 3 branches that provide arterial supply to head, neck, upper limbs, and part of thorax:
aortic arch
44
runs along anterior spine. Called thoracic aorta from T5 – T12. Supplies the thorax and viscera, it enters the abdominal cavity to become the abdominal aorta.
descending aorta
45
supplies abdominal walls and ends at L4 where it splits into Rt. & Lt. common iliac arteries
abdominal aorta
46
supply pelvis and lower limbs
Rt. and Lt common iliac arteries
47