Ch. 14 Cardiovascular Physiology

What is the vertebrate circulatory plan

heart -> arteries -> arterioles -> capillaries -> venules -> veins

Layers of elastic artery (superficial to deep)

Tunica externa

Tunica media

Tunica intima (internal elastic membrane and endothelium

Layers of large vein

Tunica externa

Tunica media

Tunica intima

Endothelium

Lumen

open cavity within a biological tube

Tunica Intima

vascular endothelium and basement membrane

Tunica Media

smooth muscle and sheets of ECM

Tunica Externa

collagen fiber connective tissue

What do capillaries lack

tunica media and tunica externa

What is occasionally present in capillaries

contractile pericyte cell present

Transcytosis

transport of large water-soluble substances across the cell

Paracellular pathway

small molecules such as water and ions can move through pores

Continuous capillaries

basement membrane, endothelium layer (tunica intima), and intercellular cleft

Fenestrated Capillaries

basement membrane and pores in the endothelium layer

Sinusoid Capillaries

incomplete basement membrane and interceullar gap

Where are continuous capillaries found

least permeable, most common. Abundant in skin, muscles, lungs, and CNS

What is often associated with continuous capillaries

pericytes

What do the brain capillary endothelial cells have

lack intercellular clefts and have tight junctions around their entire perimeter.

What is the brain capillary endothelial cells the base layer of

the structural basis of blood brain barrier

Where do fenestrated capillaries occur

areas of active filtration (i.e. kidney) or absorption (i.e. small intestine) and areas of endocrine hormone secretion.

What are the fenestrations usually covered by

very thin diaphragm made of extracellular glycoproteins. This diaphragm has little effect on solute and fluid movement.

When do number of fenestrations in capillaries increase

during active absorption of nutrients in digestive tract organs

Which capillary is the most permeable

sinusoid

Which capillary has large intercellular clefts as well as fenestrations

sinusoid

Which capillary is irregularly shaped and have larger lumens than other capillaries

sinusoid

What is able to pass the walls in the sinusoid capillaries

large molecules and even cells

Macrophages do what

extend processes through the clefts to catch "prey" or, in liver, form part of the sinusoid wall

Vasoconstriction

diameter of the vessel decreases

Vasodilation

diameter of the vessel increases

What is the primary target of vasoconstriction and vasodilation

arterioles

Angiogenesis

minor vessels undergo remodeling

What is angiogenesis controlled by

activators or inhibitors

What do growth factors do

cause basement membrane to dissolve and endothelial cells to proliferate

What is angiogenesis often induced by

hypoxic condition

Steps of angiogenesis

1. production of protease

2. endothelium

3. proliferation

4. vascular tube formation

5. maturation

Steps of angiogensis further broken down

1.hypoxia induces HIF-1 expression and the consequent release of pro-angiogenic factors, of which VEGF is the most important

2. hypoxia also upregulates protease expression leading to basement membrane degradation and pericyte detachment

3. specialized endothelial cells- "tip cells"- migrate alon angiogenic factor gradient

4. endothelial cells are differentiated into highly proliferative stalk cells which make up the main body of the new vessel

5. VEGF stimulates DLL4 secretion which binds to Notch-1 receptors; this down regulates VEGFR suppressing proliferation

6. TPDGFB stimulates pericyte attachment and reduces proliferation and VEGF sensitivity. Blood supply stimulates further tumor growth.

What are vertebrate circulatory systems

comprised of one or more pumps in a series

What is special about mammal and bird circulatory systems

they have completely separated pulmonary and systemic circuits

What is Law of bulk flow's other name

Darcy's law

What is the law of bulk flow similar to

Ohm's law

What is the law of bulk flow

flow is equal to pressure differences divided by resistance

flow is proportional to pressure difference and inversely proportional to resistance

look at Law of Bulk flow slide

Flow

volume of fluid that moves past a given point per unit of time

What is confined in the circulatory system

flow

What is poiseuille's equation

Q = [(pir^4Delta P) / (8nl)] incorporates resistance

What alters resistance in a blood vessel

change in diameter, viscosity, vessel length

What does flow follow

the path of least resistance

What does controlling resistance do

fluid (blood) can be directed and redirected to certain body parts

How is resistance varied in resistors

resistors in series have higher resistance than resistors in parallel

How is velocity determined

by pressure and cross sectional area

What happens when blood vessels split

velocity in each channel decreases

What must the total flow of the capillary equal

the total flow of the arteriole

What is slow blood flow in capillaries necessary for

capillary exchange

What is the law of LaPlace

vessels with large diameter experience greater amounts of transmural pressure (difference between internal and external pressure)

What does increasing the thickness of the wall do

aids to reduce the stress of the walls

What must vessels do to deal with changes in pressure

must change diameter

What are elastic vessels capable of

changing diameter to accommodate changes in pressure

How is regulation of flow controlled

arterioles control blood distribution through vasoconstriction and vasodilation thus altering resistance

What is myogenic autoregulation

negative feedback loop that helps maintain blood flow to tissues

Increased blood flow increases what

pressure and causes stretching

What does stretching do

causes smooth muscle to contract and thus vasoconstriction

What does impaired dilation do

causes artery collapse and ischemia

What does force-mediated dilation cause

increased flow and vasogenic edema

What are the vasoconstrictors

noradrenaline

adrenaline

vasopressin

angiotensin II

What are the vasodilators

histamine

kinins

atrial natriuretic peptide (ANP)

Vasoactive intestinal peptide (VIP)

What is the origin of noradrenaline

vasoconstrictor; adrenal medulla, postganglionic nerve endings

What is the origin of adrenaline

vasoconstrictor; adrenal medulla

What is the origin of vasopressin

vasoconstrictor; posterior pituitary

What is the origin of Angiotensin II

vasoconstrictor; conversion of angiotensin I in the lung

What is the origin of histamine

vasodilator; mast cells

What is the origin of kinin

vasodilator; pancreas, salivary glands, sweat glands

What is the origin of atrial natriuretic peptide (ANP)

vasodilator; atria

What is the origin of Vasoactive intestinal peptide (VIP)

vasodilator; autonomic nerve endings, gastrointestinal tract nerves

What are the two factors that control blood pressure

elasticity of elastic arteries and volume of blood pumped into arteries (stroke volume and cardiac output)

Systolic pressure

ventricular systol causes blood to be ejected into arteries and pressure increases so blood flows away from the heart

Diastolic pressure

no blood being pumped BUT elastic arteries (mainly aorta) serve as pressure reserve

Pulse pressure

pressure on arteries during systole and diastole (systolic-diastolic pressure)

Ventricular contraction

contraction of the ventricles pushes blood into the elastic arteries, causing them to stretch

Steps of what follows ventricular contraction

1. ventricle contracts

2. semilunar valve opens. blood is ejected from ventricles flows into the arteries

3. aorta and arteries expand and store pressure in elastic walls

Ventricular relaxation

elastic recoil in the arteries maintains driving pressure during ventricular diastole

Steps of what follows ventricular relaxation

1. isovolumetric ventricular relaxation

2. semilunar valve shuts, preventing flow back into ventricle

3. elastic recoil of arteries sends blood forward into the rest of circulatory system

What is blood pressure measured with

BP cuff aka sphygmomanometer

What does the sphygomomanometer do

cuts off circulation by applying pressure

What does reducing pressure until blood flow begins

systolic pressure exceeds force exerted by sphygomomanometer

Karotkoff cells

thumping of intermittent flow

When do you stop reducing pressure

when karotkoff sounds are no longer heard (diastolic pressure exceeds force exerted by sphymomanometer)

What is pressure like in the capillaries

it has dropped significantly

Why are capillaries weak

b/c high pressure would cause rupture (LaPlace law)

Why are capillaries permeable

b/c low pressure is still enough to force filtrate out

Mean arterieal pressure

mean arterial pressure=diastolic pressure + 1/3 (pulse pressure)

Why is mean arterial pressure closer to diastolic pressure

because diastole lasts about 2x as long as systole

What is arteriole diameter controlled by

tonic release of norepinephrine

What happens when there's a change in signal rate where norepinephrine is increased on alpha receptors

as signal rate increases, blood vessels constricts, diameter gets smaller

What happens when there's a change in signal rate where norepinephrine is decreased on alpha receptors

as signal rate decreases, the blood vessels dilates, diameter gets larger

Controls of BP: increased activity of muscular pump and respiratory pump

increases venous return, increases stroke volume, increases cardiac output, increases mean arterial pressure (MAP)

Controls of BP: Decreased release of ANP

increases conservation of Na+ and water by kidneys, increases blood volume, increases stroke volume, increases cardiac output

Controls of BP: Fluid loss from hemorrhage, excessive sweating (path with increased conservation)

decreases BV and BP, increases conservation of Na+ and water in kidneys, increase blood volume, increases venous return, increases stroke volume, increases cardiac output, increases mean arterial pressure

Controls of BP: Fluid loss from hemorrhage, excessive sweating (path with baroreceptors)

decreases BV and BP, leads to Baroreceptors, activation of vasomotor and cardio-acceleratory centers in brain stem (leads to increased Stroke volume, heart rate, and decreased diameter of blood vessels), increases cardiac output while also decreases peripheral resistance, increases MAP

Crisis stressors (exercise, trauma, increased body temp)

decreases blood pH, O2, and increases Co2 which lead to chemoreceptors and the activation of vasomotor and accelerator centers in brain stem (decreases diameter of blood vessels, increases HR, and increases stroke volume, increases cardiac output, increases MAP

Increased vasomotor tone; bloodborne chemicals (epinephrine, NE, ADH, angiotensin II)

decreases diameter of blood vessels, increased peripheral resistance, increased MAP

Dehydration, high hematocrit

increases blood viscosity, increases peripheral resistance, increased MAP

Increased body size

increase blood vessel length, increases peripheral resistance, increases MAP