Ch. 15 Blood Flow and the Control of BP

vasovagal syncope

a benign and common emotional reaction to blood, hypodermic needles, or other upsetting sights

what does homeostatic regulation do

maintains blood flow to heart and brain

another name for blood flow

perfusion

describe what happens during vasovagal syncope

signals from the nervous system cause a sudden decrease in blood pressure, and the person faints from lack of O2 to brain

systemic arteries receive

blood that leaves the left ventricle

what is “leaky epithelium“

allows for the exchange of materials between the plasma, interstitial fluid, and cells

where is leaky epithelium found

capillaries

how do arteries act as a pressure reservoir

arteries are expandable and elastic and store energy and pressure when they swell with blood when the heart contracts. During relaxation the arteries slowly release the stored energy through elastic recoil to maintain the continuous driving pressure for blood to keep flowing

how do arterioles control blood flow to individual tissues

arterioles create an area of high resistance to blood flow due to their tiny diameters. They control blood flow to tissues by selectively constricting and dilating (called variable resistance) which decreases and increases blood flow respectively

what are 3 factors that regulate arteriolar diameter

tissue oxygen concentrations, autonomic nervous system, hormones

where does blood transition from the capillaries to the venous side of circulation

distal ends of capillaries

How do veins act as a volume reservoir

while arteries serve as a pressure reservoir, veins serve as a volume reservoir and can hold a majority of blood at any given moment due to them being highly distensible. If blood pressure falls too low then the veins can constrict to send more blood to the arterial side of circulation and maintain cardiac output and BP

what is the inner layer of blood vessels made up of

endothelium

what are 3 functions of the endothelium of blood vessels

secretes paracrine factors (“local chemicals“), regulates BP, blood vessel growth, and absorption

what are 4 types of tissues blood vessels contain

endothelial, smooth muscle, elastic and fibrous connective tissue

how is vascular smooth muscle arranged in blood vessels

circular or spiral layers

muscle tone is a state of

partial contraction

what’s the function of vascular smooth muscle in blood vessels

vasoconstriction and vasodilation

what does contraction of vascular smooth muscle depend on

the Ca2+ entry from the extracellular fluid through Ca2+ channels

what 4 things is muscle tone important for

regulating blood pressure, blood flow distribution to body, proper oxygen and nutrient deliveries

what 3 signal molecules influence vascular smooth muscle tone

1) neurotransmitters

2) hormones

3) paracrine signals

name 3 neurotransmitters

catecholamines, norepi, ACh

what 2 things secrete paracrine signals

endothelial cells lining blood vessels and tissues surrounding the vessels

name 2 paracrine signals

nitric oxide, von Willebrand factor

name the five blood vessels in order as blood flows FROM the heart

arteries, arterioles, capillaries, venules, veins

what connects arterioles and venules

capillaries

what are the three layers that make up the walls of blood vessels

1) smooth muscle

2) elastic connective tissue

3) fibrous connective tissue

tunica intima is made by

endothelium and its adjacent elastic connective tissue

the thickness of the smooth muscle and connective tissue layers ________ in different vessels

varies

what blood vessels make up the microcirculation

arterioles, capillaries, and venules

metarterioles are branches of

arterioles

explain how metarterioles work

precapillary sphincters open and close to direct blood flow to capillaries or venous circulation

describe the two paths blood can take through metarterioles

1) if muscle rings called precapillary sphincters are relaxed, blood is directed into adjoining capillary beds

2) is the precapillary sphincters are all constricted, metarteriole blood bypasses the capillaries and goes directly to the venous circulation

rue arterioles have a __________ layer

continuous smooth muscle layer

the wall of a metarteriole is partially surrounded by

smooth muscle

capillaries are the primary site of exchange, but where else can exchange take place

postcapillary venules at the distal ends of the capillaries

basal lamina

an acellular matrix that supports he endothelium in capillary walls, also called the basement membrane

pericytes

highly branched contractile cells that surround capillaries forming a mesh-like outer layer between the capillary endothelium and the interstitial fluid

what do pericytes secrete

paracrine factors

3 functions of pericytes

regulate capillary blood flow, stabilize vessel walls, and maintain the integrity of the BBB

the more pericytes the ___________ capillary endothelium

less leaky

what type of capillaries make up the BBB

cerebral and retinal capillaries

how are selectively permeable barriers formed

cerebral and retinal capillaries are surrounded by pericytes an glial cells and connected with tight junctions

loss of pericytes around the capillaries of the retina can cause _________ leading to blindness

diabetic retinopathy