PNB 2275 Exam 2

blood must circulate so that it can…

deliver nutrients and remove waste, provide immune protection and clotting functions, maintain homeostasis

rank hydrostatic pressure in arteries, capillaries, and veins

arteries (80-120 mmHg) %%**>**%% capillaries (15-35 mmHg) %%**>**%% veins (0-20 mmHg)

coronary arteries

deliver oxygenated blood to heart cells

coronary veins

drain into coronary sinus, which opens into right atrium; return deoxygenated blood from the heart cells back to the general circulation

functional classification of vessels

distribution, exchange, collection

characteristics of arteries

hold \~13% blood volume, need to withstand high pressure during ventricular systole

types of arteries

elastic, muscular, arteriole

elastic artery

large diameter, buffer changes in blood pressure because of pressure-storing ability due to lots of elastic tissue, conducting

muscular artery

medium diameter, most common type, distribution

arteriole

small diameter, %%no tunica externa%% (smooth muscle tunica media is on the outside instead), can alter peripheral resistance and effect blood pressure

how is diameter controlled in arterioles?

because there is no tunica externa, diameter can be controlled by local, autonomic, and hormonal factors

capillary characteristics

holds \~9% of blood volume, permit bi-directional flow, have thin walls made up of a single layer of endothelium cells and a connective basement membrane essential for exchange

capillary bed

large surface area, thin-walled vessels, mesh like network, contains thoroughfare channels and metarterioles

thoroughfare channels

within the capillary bed, direct flow between arteries and veins

metarterioles

small vessels with precapillary schincters (individal smooth-muscle cells in place of tunica media to regulate flow within and between beds) 

Arteriovenous anastomosis

proximal to the capillary bed, allow alternate route of bloodflow in event of blockage

types of capillaries

continuous, fenestrated (window), sinusoid (large holes)

continuous capillaries

exchange small molecules without loss of RBCs or plasma protein, found in most tissue, thin continuous walls

fenestrated (window) capillaries

exchange small peptides; fenestrations = windows; found in hypothalamus, pituitary, intestine, kidneys

sinusoid (large holes) capillaries

exchange blood proteins and blood cells; like fenestrated but with larger windows and 5 times larger diameter; found in liver, marrow, spleen

characteristics of veins

accommodate low pressure on return to heart, hold \~64% of blood volume, thin walls allow veins to expand without rupture

how to veins deal with low pressure

skeletal muscle pump and respiratory pump

skeletal muscle pump for veins

Veins pass through skeletal muscles → when skeletal muscles contract, they push on the veins and move the blood; valves in the veins keep this flow unidirectional and prevent backflow during diastole

respiratory pump for veins

The drop in pressure in the chest cavity during inhalation reduces pressure on the veins; allows blood to flow back towards the heart

types of veins

venule, medium-diameter vein, large vein

venule

small diameter, no muscle (no real tunica media)

medium-diameter vein

medium diameter, some have valves (made of in-folding of the tunica intima), expand easily to accommodate volume changes (high compliance)

large veins

large diameter, can hold large blood volume, has three layers, but the layers are relatively thin

vein functions

low-resistance conduit of blood back to right atrium, venous blood reserve (central reflexes can decrease compliance to increase arterial blood volume)

the layers of arteries are ___ than the layers of veins

thicker

3 layers of arteries and veins

tunica externa, tunica media, tunica intima

tunica externa

outer layer, support, connective tissue made of collagen and elastic fibers, some smooth muscle

tunica media

middle layer, contraction, primarily smooth muscle surrounded and contained by internal/external elastic membranes, transverse elastic fibers

tunica intima

inner layer, lining, endothelial cells, longitudinal elastic fibers running the length of the vessel, subendothelial connective tissue

blood pressure =

cardiac output \* total peripheral resistance

total peripheral resistance is also called

systemic vascular resistance

flow =

change in pressure/resistance = (P arterial - P venous)/resistance

flow occurs when system circulatory pressure is ___ total peripheral resistance

greater than

resistance

* friction between blood and vessel wall
* L = length
* n = viscosity
* r = radius

arrangement of vessels affects resistance…parallel arrangement has ___ resistance than series arrangement

lower

example of parallel arrangement of vessels

capillaries

flow =

velocity \* area

with a constant flow, velocity and area are ___ proportional

inversely

how does surface area play a role in capillaries?

* Capillaries have very narrow diameters, so we would think the velocity is high → this would give them no time to exchange which is bad since that’s their main job
* BUT when you combine many capillaries, there is an aggregate cross-sectional area that is VERY HIGH 
* %%High area results in very slow blood velocity → this gives enough time for gas/nutrient exchange%%

Poiseuille’s Law

* predicts blood flow rate in a vessel
* delta P: pressure gradient
* r: radius
* n = viscosity
* L = length of vessel

methods of capillary exchange

diffusion, transcytosis, bulk exchange

what happens at the arterial end of the capillaries

forces water OUT of the capillaries, hydrostatic pressure is the driving force

net hydrostatic pressure (NHP) =

capillary hydrostatic pressure (CHP) - interstitial hydrostatic pressure (IHP)

what values of NHP show flow in/out of capillaries

* NHP > 0 → fluid flows out of capillaries 
* NHP < 0 → fluid flows into capillaries 

what happens at the venous end of the capillaries

reabsorption, draws water INTO the capillaries, oncotic pressure is the driving force

oncotic

colloid osmotic pressure (COP) = osmotic pressure for large solutes

oncotic pressure =

molarity \* RT (high concentration = high oncotic pressure)

net colloid osmotic pressure (NCOP) =

blood COP - interstitial COP

equation for net filtration pressure =

NHP (net hydrostatic pressure) - NCOP (net colloid osmotic pressure)

positive net filtration pressure indicates

net flow out

negative net filtration pressure indicates

net flow in

exchange equation that incorporates filtration coefficient and reflection coefficient

NFR = Kf (Pc - Pi) - σ (πc - πi)

reflection coefficient (σ)

* an adjustment for oncotic pressure
* high σ = low protein permeability (ex. glomerulus, brain)
* low σ = high protein permeability (ex. liver, spleen)

filtration coefficient (Kf)

* high Kf = high H2O permeability (ex. kidneys)
* low Kf = low H2O permeability

major functions of lymphatic system

* homeostatic re-circulation: collects excess leaked fluid from the capillaries and returns it to the blood circulation
* absorption: transport absorbed fat to blood via lacteals
* immune: Production, maintenance, and distribution of lymphocytes (T-cells and B-cells); delivery of pathogens, antigens, and dendritic cells to lymph nodes

lacteals

specialized structures in intestinal villi that transport absorbed fat

how does lymphatic flow occur? what is the speed?

* slow
* occurs by skeletal muscle pump and peristaltic smooth muscle contraction
* helped by valves

what happens when the lymphatic system doesn’t recover excess fluid?

edema

what could cause edema?

increased capillary pressure, decreased plasma proteins, increased capillary permeability, blockage of lymph return

Viagra → ___ PDE3 → does not allow conversion of cGMP and cAMP to GMP and AMP → more cGMP and cAMP → smooth muscle ___ → blood vessels ___ → more blood flow → PENILE ERECTION!!!

inhibits, relaxes, dilate

does smooth muscle have sarcomeres?

no

does smooth muscle have troponin?

no

Opening of IP3 receptors (and some RyR) on sarcoplasmic reticulum release ___ into the cytoplasm

Ca2+

what regulates contraction in smooth muscles

myosin light chain (MLC)

MLC is regulated by ___, which leads to ___

calmodulin/MLC kinase (MLCK), contraction

MLC phosphatase reverses ___ function, leading to ___

MLCK, relaxation

Smooth muscle activity constricts and dilates ___

blood vessels

epinephrine functions

increases cardiac output, heart rate, stroke volume, and contractile force

pathway for increased contractile force

epi → beta-1 adrenergic receptor → Gsa → cAMP → PKA

what receptor does epi bind to increase blood pressure?

alpha-1 adrenergic on smooth muscle of blood vessels

pathway for increasing blood pressure

thromboxane → Gq g-protein signaling → IP3 receptors on sarcoplasmic reticulum are activated → calcium is released into cytoplasm → increased contraction of smooth muscle → elevates BP 

what does thyroid hormone do?

increases cardiac output, heart rate, stroke volume, and contractile force

how does TH increase contractile force

TH-receptor-mediated regulation of genes related to contractility; elevates Ca2+ ATPase pump and decreases phospholamban

how does TH effect blood pressure?

decreases it

what receptor does TH bind to to effect blood pressure

beta-2 adrenergic receptor

pathway of TH effect on blood pressure

TH increases expression of beta-2 adrenergic receptors → activates cAMP → inhibits MLCK → relaxes smooth muscle → dilation of blood vessels → decreased BP → elevated blood flow to skeletal muscles 

hyperthyroidism

low systemic vascular resistance (dilation of BP), high heart rate, increased ejection fraction, increased cardiac output

nitric oxide

gasouse signaling molecule

where and in response to what is NO released

released by endothelial cells in response to shear force of blood flow (high BP)

NO activates guanylate cyclase (GC) → ___ → ___

increases cGMP; activates protein kinase G (PKG)

what does NO release do to blood pressure

decrease it

how does NO make blood pressure go down?

* Increases MLC phosphatase → inactivates MLC → muscle relaxation → dilates blood vessels → blood pressure goes down
* Inhibits IP3-R receptors on sarcoplasmic reticulum, so Ca+ is not released and can’t bind to calmodulin → MLCK does not get activates → inactivates MLC  → muscle relaxation → dilates blood vessels → blood pressure goes down

compliance

* how easily a heart chamber of blood vessel expands when filled with blood
* change in volume over change in pressure

what is compliance on a curve of volume v.s. pressure

slope of the curve

veins have ___ compliance because they need to ___

high, have a large change in volume in response to a small change in pressure

veins have ___ elasticity

low (store very little pressure even with large volume changes)

arteries have ___ compliance because ___

low, a massive change in pressure is required for a small change in volume

arteries have ___ elasticity

high (a small volume change results in a large pressure change)

what are the 3 lines of defense in the immune system?

prevention of infection → targeted destruction of pathogens → specific targeting of pathogens/immunological memory

the first two line of defense of the immune system are ___

nonspecific

the third line of defense of the immune system is ___

specific

1st line: prevention of infection

* Skin
* Mucous membranes
* Secretions of skin and mucous membranes

2nd line: targeted destruction of pathogens

* Phagocytic white blood cells
* Antimicrobial proteins 
* The inflammatory response 

3rd line: specific targeting of pathogens; immunological memory

* Lymphocytes 
* Antibodies 

nonspecific lines of defense

* first line: physical barriers, inflammatory response
* second line: phagocytes, immunological surveillance, interferon, complement, fever