NPB 101L Lab 4 The Human Cardiovascular System

Purpose of lab

1. Use non-invasive techniques to measure various properties of the human cardiovascular system.

2. To measure changes in blood pressure and heart rate induced by postural changes.

3. to measure cardiovascular responses to exercise at several constant work loads.

Baroreceptor reflex

The primary reflex pathway for homeostatic control of blood pressure (short term regulation of BP)

microcirculation

small blood vessels, including arterioles, capillaries, and venules, all of which can be affected by local changes as the result of inflammation

local metabolites

In cerebral vascular regulation, circulation is controlled almost entirely by

vasodilation

Almost all local anesthetics have this property and sometimes require the administration of vasoconstrictors (ex. Epinephrine) to prolong activity

vasoconstriction

A decrease in the diameter of blood vessels caused by contraction of smooth muscles in the vessel walls.

venous capacitance

regulates the volume of blood returning to the heart, which is a major determinant of the end-diastolic volume of the hear

sympathetic nervous system

A subdivision of the autonomic nervous system that activates nerves, glands and visceral muscles in times of stress or threat (prepares the body for action)

Function of the Circulatory System?

Deliver oxygen and nutrients to tissues and remove waste products and metabolites.

What does the Circulatory system consist of?

heart, blood vessels and blood

What enters the right atria?

De-oxygentated blood from the systemic circulation

How is blood pumped to the pulmonary circulation?

by the right ventricle

What happens when the blood goes to the pulmonary system?

That is where bass exchange occurs. CO2 out, and O2 in.

Where does the oxygenated blood return?

Left Atria

The blood that is returned is pumped out of the heart to the rest of the body by?

the left ventricle

What are the four chambers of the heart?

Right and Left Atria, and also right and left Ventricles

Arteries have smooth muscles and large numbers of elastic fibers in their walls, allowing them to?

stretch and accommodate the blood being ejected from the heart.

There is a minimal changes in capacitance, so pressure in arterial system is determined by what?

primarily by volume changes

Arterioles also have smooth muscle, but less elastic fibers compared to arteries. as a result?

their diameter can be changed to regulate blood flow through organs. Arterioles are the resistance vessels.

• Elastic arteries (like the aorta) stretch — but their capacitance doesn't vary much over time, so pressure changes are still driven mostly by volume.

• Arterioles don’t need to stretch — they use smooth muscle to control diameter, not elastic recoil.

Capillaries

do not contain smooth muscle, so their diameter does not change

Exchange vessels

allow diffusion of solutes and fluid

Venous vessels have very thin wall, and because of there thin walls, the vessels are

very compliant with a very large capacitance in comparison to the arterial and capillary vessels.

Veins and venules contain smooth muscle, so their diameter can change, which leads to

changes in compliance and capacitance

Capacitance can increase by

vasodilatation as a result of local vasodilators, such as metabolites

on the venous side, changes in capacitance dominate over changes in

resistance.

In veins, the body regulates blood return to the heart (venous return) mainly by adjusting how much blood the veins store, not by changing how narrow they are (resistance).

Blood flow is achieved through

differences in pressure (mmHg).

Flow causes friction between blood and the vessel wall, causing the

vessel to resist fluid movement (vol/time).

Vascular Resistance is a measure of how

hard it is for blood to flow through a vessel (mmHg*time/vol).

Flow is equal to

pressure difference over resistance

Pressure (MAP) remains constant so

changes in resistance are used to alter flow rate.

Heart works to keep arterial pressure

higher than venous pressure

Cardiac Output

volume of blood pumped by each of the ventricles per minute

CO?

HR?

SV?

1. Vol of blood pumped by each of the ventricles per min. CO=Hr x SV

2. heart rate, number of beats per minute

2. stroke volume, volume of blood ejected per beat (vol/beat).

Resistance

small changes in the radius can greatly affect resistance. Blood flow is primarily regularly changes in the radius of the vessel.

Pressure in the blood vessel is determined by

volume of blood in the vessel, and how easily the vessel can be stretched, veins are more compliant than arteries.

Compliance

is measure of how easily a vessel can stretch. small changes in venous pressure can greatly alter volume of blood in the venous system.

Vessels that have a high compliance are said to have a

large capacitance (holding capacity).

There is a 10 mL volume increase in two vessels. one stiff with small capacitance and the second very complain, large capacitance vessel. how will this volume change effect pressure in these two vessels?

there will be a greater increase in pressure in the vessel with the smaller compliance. since first vessel is stiff, compliance does not change with the change in volume. with the volume increase, pressure has to increase.

Pressure cuff increases pressure of upper arm to

cause blood vessel to collapse.

pressure from the cuff temporarily exceeds the pressure inside your arteries, causing them to collapse (close off) and block blood flow…. EX: stepping on a hose

As the cuff pressure decreases to just below the systolic pressure, small amounts of blood are able to ?

pass through arteries. this intermittent, turbulent blood flow can be heard as a 'tapping' sound.

What are the sounds heard called?

Korotkoff Sounds

Systolic BP

pressure where korotkoff sound first able to be heard, non laminar or turbulent flow. where Peak pressure generated in the artery.

Diastolic BP

pressure where korotkoff sound no longer heard

Arterial pressure is a function of a

change in volume since its capacitance is fairly constant

an increase in volume occurs in the arterial system when

blood is ejected from the ventricles during systole.

During systole, only about #?? of the blood in the arteries flows out to the tissues right away. The rest causes the arteries to stretch (distend), which increases pressure.

only one third

during diastole the arteries recoil

passively to push blood out of the arteries. this continued blood flow out of the arteries during diastole allows blood flow to the capillaries to be constant.

The maximum arterial pressure that is reached during peak ventricular ejection is called the?

systolic pressure. After this, ventricular relaxation

What is the difference between the systolic pressure and diastolic pressure called?

Pulse pressure

Pulse pressure is

SP minus DP, average systolic and diastolic BP range is 120 over 80.

Pressure is determined by changes in

venous volume and changes in venous compliance.

• Venous pressure = mainly affected by volume & compliance

• Arterial pressure = mainly affected by cardiac output & resistance

• Because veins are more like stretchy storage tanks, while arteries are high-pressure pipes distributing blood.

because veins are highly compliant — they act as blood reservoirs, holding ~70% of total blood volume. So:

• Small changes in volume or stretchiness (compliance) cause noticeable changes in venous pressure.

How much of your blood resides within your veins.

60 to 70 percent

what is normal venous pressure

less than 10 mmHg

Since the volume in the venous side is so large, small changes in

venous capacitance results in large shifts in volume.

Increase sympathetic nerve activity,

decreases diameter of veins, which decreases capacitances

increase venous pressure and increase venous return as

more blood is returned to the heart

Mean Arterial Pressure

average effective pressure that drives blood through the systemic organs. CO times TPR

Total peripheral resistance

overall resistance to flow through the entire systemic circulation

Map can be approximated by

one third time SBP plus two thirds times DBP, which is the weighted average because the heart spends more time in diastole then systole.

The sympathetic nervous system can heavily influence blood pressure by

changing arteriolar resistance and venous capacitance

norepinephrine resale from these nerves causes

vasoconstriction

Norepinephrine: In arterioles

this results in an increase in resistance, which decreases blood flow to the venous side

Norepinephrine: in venous side

vasoconstriction leads to a decrease in capacitance, which decrease venous volume.

Supine position

assume the whole body is at heart level so there is no added hydrostatic pressure

Standing

hydrostatic pressure added to areas below heart level and subtracted from areas above heart level. Decrease in venous return due to pooling.

What acts in a negative feedback manner

Prevents large changes in MAP despite changes in the heart and blood vessels.

The arterial baroreceptors are sensory receptors found in the

aortic arch and carotid sinus that constantly monitor blood pressure by sensing stretch.

The baroreceptors send information to the

Brain

The baroreceptors are active at normal arterial pressure so they supply a

steady input to the central integration centers

based on the information send, an appropriate response is mediated through

changes in sympathetic and parasympathetic activity

Decrease in blood pressure

decreased firing of baroreceptors

Brain sends signals that result in an increase in what and decrease in what?

Increase in sympathetic activity and decrease in parasympathetic activity

The increased sympathetic activity causes

vasoconstriction of the arterioles, which leads to an increase in TPR. Also causes constriction of the veins, which increases venous return.

The decreased parasympathetic activity increases

heart rate, which increases CO and with increased SV.

What work together to increase MAP

TPR and CO (MAP = TPR x CO)

Decrease in BP

Decrease firing rate of baroreceptors.

Decrease in sympathetic and increase in parasympathetic activity

leads to a decrease in BP

Increase in sympathetic and decrease in parasympathetic activity.

leads to a increase in BP.

Active Hyperemia

increased blood flow caused by an increase in metabolic activity. Exercise causes the release of metabolites that can cause vasodilation and increase blood flow

Reactive Hyperemia

reaction to a decrease in blood flow to a tissue with no change in the tissues metabolism

Transient higher than normal blood flow after the removal of

any restriction causing a lower than normal blood flow. examples include when your foot falls asleep, then wakes up. Build up of local metabolites that would normally be swept away in normal blood flow. And elevated (vasodilators) causes a transient increase in flow.

Dive reflex

allows prolonged submersion by limiting rate of oxygen use and direction blood flow to essential organs

How is the dive reflex achieved

By bradycardia (parasympathetic) and vasoconstriction (sympathetic) of all systemic organs. This response is unusual in that both parasympathetic and sympathetic activity are increased

What does the dive reflex allow

it allows a person to survive longer without oxygen underwater than someone in a similar situation on land. Poorly developed in humans compared with diving mammals

What does the dive reflex require

cold and wet conditions to work

What will you measure in the dive Reflex

Electrocardiogram. P wave is depolarization of RA and LA. QRS wave is depolarization of RV and LV. T wave is depolarization of RV and LV.

With a decrease in heart rate, what will you see

an increase in the RR interval distance. Opposite occurs with an increase in heart rate.