Chapter 14 Blood vessels, blood flow, blood pressure

As blood enters capillary beds, velocity of blood flow __________

Decreases

When the resistance increases blood flow _______

Decreases

What are sinusoids? What type of cells do they have?

Large blood filled spaces that function in the exchange of substances between blood and tissue Have phagocytes

Describe fenestrated capillaries

Large pores that allow for rapid diffusion of small water soluble substances

Vein anatomy

Larger diameter than arteries but walls are only half as thick Walls contain smooth muscle, elastic and fibrous connective tissue Contain one-way valves that permit blood flow toward the heart but prevent it from flowing back to organs/tissues (only in peripheral veins not central veins)

Capillaries contain _______ walls

Leaky

What condition occurs when MAP is less than normal? Higher than normal?

Less: hypotension Higher: hypertension

what type of muscle do arterioles have? What does this allow?

Lined with smooth muscle that can relax/contract allowing resistance of blood flow to be regulated

The Aorta has ____ resistance

Little

Hormonal control of MAP

Long term Regulates blood volume

Blood pressure in veins is significantly ________than arteries

Lower

Mean arterial pressure equation

MAP = SV x HR x TPR

How to calculate mean arterial pressure

MAP= (SP+ (2DP))/3 MAP= CO x TPR

Describe the continuous capillaries

Most common type of capillaries Contain intracellular clefts (narrow spaces between tight junctions of continuous capillary endothelial cells) Highly permeable to water soluble substances with small molecular size and lipid soluble substances

Net filtration pressure formula

NFP= filtration pressure - absorption pressure (Pcap + Piif) - (Pif- picap)

What are four intrinsic mechanisms to regulate blood flow? What do they do

Nitric oxide: vasodilation Prostacyclin: Vasodilation Adenosine: vasodilator in coronary arteries Endothelin 1: vasoconstrictor

Does the parasympathetic nervous system innervate arteriolar smooth muscle? Is there any exceptions?

No except in external genitalia vasodilation

What happens in arterioles With increased sympathetic nerve activity

Norepinephrine binds to alpha adrenergic receptors (vasoconstriction) Increase TPR Increase MAP

What is interstitial osmotic pressure? What does it usually favor?

Osmotic force exerted by proteins in the interstitial fluid Favors filtration

Calloid osmotic pressure (oncotic pressure)

Osmotic pressure that is exerted by proteins

In the systemic circuit what are the formulas for pressure gradient

P= pressure in aorta- pressure in vena cava P= MAP- CVP

In the pulmonary circuit what is the formula for pressure gradient

P= pulmonary arterial pressure- pulmonary venous pressure

Describe discontinuous capillaries

Serve as a transition from fenestrated capillaries to sinusoids Found in areas where proteins and cells must cross the endothelium

arterioles function

Serves as passageway for blood to enter capillaries where exchange between blood and tissue takes place

Neural control of mean arterial pressure

Short term Regulates CO and TPR Managed through negative feedback control Controlled by integration center (cardiovascular control center) of the medulla oblongata

What are the three types of exchange across capillary walls

Simple diffusion Transcytosis Mediated transport

Describe simple diffusion

Small solutes (lipid and water soluble) move across capillary walls by simple diffusion Lipid soluble solutes diffuse across the plasma membrane of endothelial cells Water soluble solid to diffuse through water filled pores between endothelial cells

Venule anatomy

Smaller than arterioles with thinner walls that contain little or no smooth muscle

Describe the anatomy of capillaries

Smallest blood vessels Thin walls consisting of a single layer of endothelial cells with pores between them (allows for small diffusion)

The _________ muscle in the walls of veins contract or relax in response to input from the ___________nervous system and certain chemical agents

Smooth Sympathetic

What are precapillary sphincters? How are they controlled?

Smooth muscle that surrounds capillaries on the arteriolar end that regulate blood flow through capillaries Affected by local control Increase in metabolites relax sphincters and increase blood flow through capillaries

What are four factors that affect venous pressure

skeletal muscle pump, respiratory pump, blood volume, venomotor tone

What Instruments are used to measure blood pressure

sphygmomanometer and stethoscope

Pulse pressure formula

systolic pressure - diastolic pressure

Blood pressure formula

systolic/diastolic

What makes up microcirculation

arterioles, capillaries, venules

myogenic response

A change in vascular resistance that occurs in response to stretch of blood vessels Does not require actions of sympathetic nerves, hormones, other chemical agents

What happens upon standing that makes a person feel dizzy

A drop of MAP and increase in hydrostatic pressure upon standing (orthostatic hypotension) may cause a person to feel dizzy because of decrease in blood flow to the brain

Edema

A shift in fluid from plasma to interstitial fluid that causes swelling of tissues

Describe blood volume as it relates to venous pressure

An increase in blood volume produces an increase in venous pressure and MAP A decrease in blood volume produces a decrease in venous pressure and MAP

What happens when there is an increase in Venomotor tone

An increase in venomotor tone promote a rise in CO and MAP

Where are Arterial baroreceptors (aka sinoaortic baroreceptors)

Aortic arch and carotid sinus of carotid arteries

Arterial end of capillaries is for ________ while venous end is for ________

Arterial end filtration Venous end reabsorption

What type of vessel has the largest pressure drop because of its high resistance

Arterioles

What type of vessels provide the greatest resistance to blood flow?

Arterioles

________ contribute to 60% of TPR

Arterioles

what happens in arterioles When Eppinette friend secreted from the adrenal medulla in response to sympathetic activity binds to Alpha receptors? Binds to beta-2 receptors?

Binding to alpha receptors causes vasoconstriction Binding to beta to receptors activates CAMP which causes vasodilation and decreased resistance of blood flow

What are the 4 Starling forces?

Capillary hydrostatic pressure (Pcap) • interstitial fluid hydrostatic pressure (Pif) • capillary osmotic pressure (piCAP) • Interstitial fluid osmotic pressure (piif)

_______ hydrostatic pressure and _______ Osmotic pressure favor filtration

Capillary hydrostatic pressure and interstitial fluid osmotic pressure

Total peripheral resistance

Combined resistance of all the blood vessels within the systemic circuit

What does venules connect? What is their function?

Connect capillaries to veins Exchange between blood and interstitial occurs in capillaries and small venules

Vasomotion

Contraction and relaxation of precapillary sphincter's

What does venomotor tone

Degree of tension exerted by smooth muscles in walls of vein

Capillary hydrostatic pressure

Favors filtration Equal to the blood pressure in capillaries Blood pressure decreases as blood flows from the arteriolar end of the capillary to the Venule end

Capillary osmotic pressure

Favors reabsorption Does not change his blood flows from one end of the capillary to the other

Interstitial fluid hydrostatic pressure

Favors reabsorption Is usually low

Filtration and absorption in capillary walls

Filtration: fluid moving from blood to interstitial fluid Absorption: fluid moving from interstitial fluid to blood

How to calculate Oregon blood flow

Flow= P/ organ resistance Flow= MAP/ organ resistance

flow rate formula

Flow= P/R

Osmotic pressure

Force exerted on water by non-permeating solutes

The systemic circuit has _______ resistance

Greater

Veins have _______ compliance

High (A large increase in blood volume is required for a large increase in pressure)

What end of a capillary is NFP higher? Lower?

Higher at arteriolar end Lower at venule end

active hyperemia

Increase in blood flow following an increase in metabolic activity (observed during exercise)

Changes associated with increased metabolic activity causes ________ while changes associated with decreased metabolic activity causes ________

Increased metabolic activity causes vasodilation Decreased metabolic activity induces vasoconstriction

Describe the process of the respiratory pump when you inhale

Inhale -> diaphragm pulls downward and rib cage expands -> lowers pressure in thoracic cavity and raises pressure in abdominal cavity -> pressure gradient that promotes the movement of blood from abdominal veins to central veins -> increasing blood flow toward the heart

What are meta-arterioles? What are their functions

Intermediate between arterioles and capillaries Serve as shunts by directly connecting arterioles to venules

_______ hydrostatic pressure and _______ Osmotic pressure favor absorption

Interstitial fluid hydrostatic pressure and capillary osmotic pressure

What does intrinsic controls use to regulate blood flow? What does extrinsic control use to regulate MAP?

Intrinsic control uses metabolites that regulate blood flow Extrinsic controls use the ANS and hormones to regulate mean arterial pressure

arteriolar tone

Partial vasoconstriction of arterioles due to inherent contractile activity of smooth muscle

How to calculate hydrostatic pressure gradient

Pcap- Pif

perfusion pressure. What happens to blood flow and arterial pressure if perfusion pressure increases?

Pressure gradient that drives blood flow through a given organ or tissue If perfusion pressure increases blood flow increases and arteriolar pressure rises

Arterial baroreceptors

Pressure in aortic arch and carotid sinus

What is the Function of capillaries

Primary site where exchange of nutrients and waste products occur between blood and tissues

Describe transcytosis

Proteins are selectively transported across endothelial cells Requires energy Uses endocytosis and exocytosis

Describe mediated transport

Receptor mediated Certain solutes are transported across endothelial cells by mediated transport in the brain

A decrease in oxygen and increase in CO2 causes ________ of arteriolar smooth muscle

Relaxation

What are Starling forces?

The forces that drive the movement of fluid into an out of capillaries

What vessel is the volume Reservoir

Veins are the volume reservoir (blood reservoir) due to high compliance

The pulmonary and systemic circuit have different or the same pressure gradient

The pressure gradient is smaller in the pulmonary circuit because the pulmonary arterial pressure is lower than aortic pressure

What is the respiratory pump

The rise in thoracic pressure drives the forward movement of blood from the central veins to the heart, thereby promoting increased venous return and CO (increase in venous pressure)

The pulmonary and systemic circuit have different or the same flow

The same

What are the largest veins

Vena cavae

How does long-term regulation of blood pressure occur

Through blood volume regulation

In vasculature, what is the tunics intima, túnica media, and túnica externa

Tunica intima: internal elastic membrane endothelial layer Tunica media: external elastic membrane made of sheets of smooth muscle and loose connective tissue Tunica externa: smooth muscle in veins made of collagen and elastic fibers

How is turbulence caused? What does turbulent blood flow cause?

Turbulence is caused when pressure inside the artery is higher than pressure outside of it which forces the vessels to open and causes turbulent blood flow into the artery through a narrow opening. Causes audible vibrations (korotkoff sounds)

A decrease in metabolic activity causes a decrease in CO2 and increase in oxygen which causes _______ of arterioles

Vasoconstriction

What is vasoconstriction? What is vasodilation?

Vasoconstriction: decrease in vessel radius Vasodilation: increase in vessel radius

What two hormones cause vasoconstriction and increase MAP in arterioles

Vasopressin (ADH) Angiotensin II

What are the three main factors affecting blood flow

Vessel radius (as radius decreases, resistance increases) Vessel length (longer vessels have greater resistance) Blood viscosity (as viscosity increases resistance increases)

What happens when NFP is positive? When it's negative?

When NFP is positive filtration occurs. When NFP is negative absorption occurs.

What happens when arterial pressure rises and arteries expand

When arterial pressure rises -> arteries expand (stretching their walls and sensory endings of the baroreceptors within them) -> induces depolarization -> triggers action potentials conducted to CNS via baroreceptor axons

What is the skeletal muscle pump

When skeletal muscles contract, they press against veins traveling between them, which raises the venous pressure of blood Increased pressure -> forces distal valves to close -> prevents blood from flowing backward -> forces proximal valves to open -> allows blood to flow toward the heart

Baroreceptors

a type of sensory receptor neuron in blood vessels and the heart that respond to changes in pressure within the cardiovascular system

Venus pooling

accumulation of blood in the veins

________ are pressure reservoirs. Which means they have _____ compliance.

arteries Low compliance ( A small increase in blood volume causes a large increase in blood pressure)

What are the three types of capillaries

continuous, fenestrated, sinusoidal (discontinuous)

Arteries have ______ blood pressure

highest

reactive hyperemia

if blood supply cut off then restored, flow increases above normal

What happens when there's an increase in venous pressure

increase in venous pressure enhance venous return -> increases end diastolic volume -> increases stroke volume -> increases CO -> increases MAP