Lecture 5 Flashcards
Peripheral Resistance
-_________________ markedly affects blood velocity
-most ____________ influence on blood flow
-only significant way of controlling resistance
- Vessel radius
-powerful
- ____________ flow: blood flows in ________, faster in the __________
- blood flow (F) is proportional to the _______ power of radius (r)= ____________
- small changes in blood vessel radius can cause ________ changes in flow (mL/min)
- Decrease radius by a factor of 2, ___________ resistance and ____________ flow by ___x
- R= _________
- Laminar; layers; center
- fourth; F ∝ R^4
- LARGE
- increase; decrease; 16
- R=1/(r)^4
Vasoreflexes: changes in _______ _______
1. ______________: smooth muscle of tunic media contracts
2. ______________: brought by muscular passivity (no sympathetic input); smooth muscle relaxes; blood pressure expands vessel
vessel radius
1. vasoconstriction
2. vasodilation
______________: collective term for both vasoconstriction and vasodilation
- controlled in part by ______________ center in ______________
Vasomotion
- vasomotor; medulla oblongata
From aorta to capillaries, blood velocity (speed) ________________ for three reasons
1.
2.
3.
decreases
1. As blood traveled encountered friction against vessel walls
2. Smaller radii of arterioles and capillaries
3. Farther from heart–> number of vessels and their total cross-section area becomes greater and greater
From capillaries to vena cava, velocity ___________
- since veins are larger, they create ________ resistance than capillaries
- Large amount of blood forced into smaller channels
- blood in veins _______ regains velocity it had in large arteries
-veins are further from the pumping heart
-veins are more _________ than arteries
increases
- less
- NEVER
- compliant (they stretch more)
Blood vessels where more vasoconstriction/dilation occurs= _______________
Arterioles
Arterioles are most ____________ point of control over peripheral resistance and flow:
- On proximal side of capillary beds and best positioned to regulate _______ into capillaries
- _____________ any other type of artery, providing the most numerous control points
- more __________ in proportion to their diameter
- highly capable of changing radius
- arterioles produce ______ of the total peripheral resistance
significant
- flow
- outnumber
- muscular
- half
Regulation of Blood Pressure and Flow
- ______________ is a quick and powerful way of altering blood pressure and flow
- Three ways of controlling vasomotor activity
1.
2.
3.
- vasomotion
1. Local control
2. Neural control
3. Hormonal control
Local Control
- _______________: ability of tissues to regulate their own blood supply
- ____________ response (arterioles): __________ blood flow–> ______ stretch– >arteriole ______–> ________—> blood flow _________
- Autoregulation
- Myogenic; decrease; decrease; relaxes; dilation; increases
Metabolic theory of auto regulation: if tissue is inadequately ________, wastes _________, stimulating ______________ which increases __________–> _________ in local BP
- Bloodstream delivers oxygen and removes metabolites
- When wastes are removed, vessels __________
- important for heart and skeletal muscle where demand for oxygen and nutrients can ________ _____-fold during physical activity
perfused; accumulate; vasodilation; perfusion; decrease
- constrict
- increase; 10
Local Control:
- ____________ ___________: substances secreted by platelets, endothelial cells, and perivascular tissue to stimulate vasomotor responses
-vasodilators include __________,___________,______________
- vasoactive chemicals
- histamine; bradykinin; prostaglandins
Local Control:
Shear stress
- drag of blood flowing against the endothelial cells (like rubbing your palms together)
-stimulates endothelial cells to secrete ___________= ___________ and ____________
- ________________ chemicals in response to blood vessel trauma
-___________ ____________, ___________________, and ______________
- vasodilators= prostacyclin; nitric oxide
- vasoconstriction
-superoxide radicals; thromboxane A2; serotonin
Local Control:
- __________ _______________: if blood supply is cut off then restored, flow increases above normal
- ___________________: growth of new blood vessels
-occurs in regrowth of ________ lining, around _____________ artery obstructions, in __________ muscle, and ___________ ________
-controlled by several growth factors and inhibitors
- the result of these both= ___________ perfusion
- reactive hyperemia
- angiogenesis
-uterine; coronary; exercised; malignant tumors - increased
Neural Control
- the central and autonomic nervous systems also exert control over blood vessel size
- Vasomotor center of medulla exerts ____________ control over blood vessels throughout the body
-stimulates most vessels to _________, but _________ vessels in __________ muscle to meet demands of ___________
- Vasomotor center is the integrating center for three autonomic reflexes
1.
2.
3.
- sympathetic
-constrict; dilate; cardiac; exercise
- Baroreflexes
- Chemoreflexes
- Medullary ischemic reflex
Neural Control
Baroreflex:
- automatic, _________ feedback response to change in ________ __________
- govern _____-_______ regulation of BP
-adjustments for rapid changes in ________
-not helpful in correcting ______ hypertension
-after 2 days or less, they adjust their set point
- this reflex usually responds to _______ BP to cause vasodilation (________ BP), but can also do the opposite–> respond to drop in BP when ___________ _______
- in the ________ the reflex can be sluggish, causing dizziness when they stand up too quickly
- negative; blood pressure
- short-term
-posture
-chronic - increased; decrease; standing up
- elderly
Neural Control
- Chemoreflex: primary role is to adjust respiration to changes in blood chemistry (O2, CO2, pH)
-_____________, ______________, and _________ stimulate chemoreceptors
- secondary role is vasomotion
-act through vasomotor center to cause widespread _______________
-____________ BP and lung perfusion= ___________ gas exchange–> bring in more O2, increase CO2 exhalation
- chemoreceptors also stimulate ______________ so that increased blood flow matches increased perfusion
- hypoxemia; hypercapnia; acidosis
- vasoconstriction
- increase= increased
- breathing
Neural Control
- Medullary ischemic reflex: automatic response to a __________ in ___________ of the _________
- Medulla oblongata monitors its own blood supply
- cardiac and vasomotor centers sends __________ signals to heat and blood vessels
-____________ heart rate and contraction force
-causes widespread _______________
-_________ BP and restores normal perfusion to the brain
- Other brain centers can affect vasomotor center
-__________,__________,____________ can increase BP
- drop; perfusion; brain
- sympathetic
-increase
-vasoconstriction
-increases - stress; anger; arousal
Hormonal Control
- Hormones can influence blood pressure
-via ____________ effects
-via regulating _______ balance
- ________ pathway: _______-__________-__________
-________ blood pressure
-_______ vasoconstrictor
-vasoactive
-water
- RAA: Renin- Angiotensin II- Aldosterone
-increases
-potent
Renin-Angiotensin-Aldosterone Mechanism
1. _________ blood pressure or volume
2. _________ release _______ in response
3. ________________:
-______________
- stimulates __________
-stimulate adrenal cortex to release ___________
4. ________________:
- ________ absorption
- ________ absorption
- Result: ___________ BP
- decreased
- kidneys; renin
- Angiotensin II
-vasoconstriction
-thirst
-aldosterone - Aldosterone
-Na+
-H2O
- increased
_________ ______________ ____________: vasodilation, lowers BP
- secreted by the cells in the _______ of the heart in response to _________ of the atria
- lower BP by:
-increase _______ excretion by the kidneys
-reduces blood __________
- _______ follows in urine
Atrial Natriuretic Peptide (ANP)
- atria; stretching
- Na+
- volume
- water
_______________: produced by hypothalamus & released by posterior pituitary gland
- promotes water retention and _______ BP (urinary system)
- At pathologically high concentrations, it also acts as a __________________
- aka ________________
- action is inhibited by what college pastime (__________)
Antidiuretic hormone
- raises
- vasoconstrictor
- vasopressin
- drunk–> you pee more
_______________ and ______________ (ANS & endocrine)
- _____________ blood pressure
- adrenal and sympathetic catecholamines
- in most blood vessels:
-bind to ____-__________ receptors on smooth muscle
-cause _______________
Epinephrine; norepinephrine
- increase
- alpha-adrenergic
- vasoconstriction
Two Purposes of Vasomotion
- Method of rerouting blood from one region to another for ____________ of individual organs
-either _________ or ___________ controlled
-during exercise, sympathetic system reduces blood flow to __________ and _________ ______ and increased blood flow to ___________ __________
-_____________ ____________ in a tissue affects local circulation without affecting circulation elsewhere in the body
- if a specific artery contracts, the pressure downstream ___________, pressure upstream _______
- perfusion
-centrally; locally
-kidneys; digestive tract; skeletal muscles
-metabolite accumulation - drops; rises
