ANHS Exs. Phys. Chapter 5 The Circulatory System +Response to Exercise

Who was William Harvey

an English physician that discovered that blood comes out the left side of the heart and returns through the right side in a closed circulatory loop

Feedback Mechanism

a regulatory mechanism that responds to changes in a system after they occur, correcting deviations to maintain homeostasis

Negative feedback

works to reverse a change and return the system to its setpoint

positive feedback

amplifies the change rather than reversing it

Feed-forward mechanism

a regulatory mechanism that anticipates changes and acts to prevent deviation from desired setpoint before changes occur (predictive and proactive)

Examples of feed-forward mechanism

salvation: seeing or smelling food triggers salivation before eating

the cardiovascular control center receives input from

motor cortex, skeletal muscle, baroreceptor reflex

heart and circulatory system are innervated by

sympathetic and parasympathetic nerves

motor cortex functions as

feed-forward control

what do mechanoreceptors and metaboreceptors inform the cardiovascular control center about

that the exercising muscles require additional oxygen and blood

baroreceptors increase and decrease their signaling rate to the

cardiovascular control center, depending on how they stretched

the higher the blood pressure

the more the baroreceptors are stretched

when exercise begins what happens to the heart rate

there is a rapid and initial increase in heart rate

why is there a rapid and initial increase in heart rate at the beginning of exercise

withdraw of the vagal (parasympathetic) tone rather than an immediate increase in sympathetic output

cardiac output equation

q= hr x sv

how does stroke volume respond to exercise

it does not increase linearly but varies among individuals difference in exercise protocols

why does stroke volume increase

due to venous return increase

what are the three major factors that increase venous return

venous constriction, muscle pump, breathing/resp. pump

what is venous restriction

during rest, veins expand; during exercise veins constrict

what is a resp. pump

during expiration, thoracic pressure increases, during inspiration thoracic pressure decreases

how do you find max heart rate

220-age = max heart

cardiovascular drift

exercise above moderate intensity, heart rises slowly over time

what factors increase cardiac drift

decreased venous return over course of exercise, increased stress and sympathetic nervous stimulation

as exercise begins what works harder to increase cardiac output

the myocardium

preload

volume of blood returning to heart rate after diastole ventricles generate force and pressure to open aortic and pulmonary valve

afterload

valves forced to shut by higher bp

double product

estimates how much work the heart is doing

double product equation

double product equation= heart rate x systolic blood pressure

double product values

@ rest= 8,000 @max ex. = 42,000 or higher

blood is comprised of

plasma and formed elements

what does plasma do

transports oxygen and carbon dioxide, essential ions, glucose, fatty acids, and vitamins

what is formed elements

white blood cells, platelets, and red blood cells

blood functions to

deliver oxygen and nutrients to tissues, remove carbon dioxide and other metabolic end products, transport hormones

what percent of our body weight is blood

7%

hematocrit

% of formed elements in the blood

men and woman have what percent of hematocrit

42-48% men 37-42 % women

arterial blood vessels

transport blood away from the heart

venous vessels

transport blood toward the heart

arterioles

smallest arterial vessels, branch into capillaries

artery and vein walls have what

vascular smooth muscles

what occurs in the capillaries

exchange of gases, nutrients, and end products

arterioles have control over what

blood flow to organs

capillaries have no what

smooth muscle, cannot constrict, precapillary sphincters constrict, shunting from the part of the tissue served by capillary

onset of exercise what is the sympathetic response

stimulation of vascular smooth muscle of arterial and venous vessels, causing constriction

2 notable exceptions to vasoconstriction response

during exercise, vascular smooth muscle around coronary arteries, cerebral arteries also dilate, facilitating blood flow

the body at rest has more blood than it needs, while during exercise

the body has less blood than it needs

vasodilation factors

higher co2, higher H, adenosine, K, nitric oxide is a potent vasal dilator

blood is distributed through

two-effector model of blood flow restriction

skeletal muscle blood flow

at rest= 1L/min exercise= 20 L/min

at rest how much cardiac output flows through skeletal muscle

10-15%

at max exercise how much cardiac output flows through skeletal muscle

80-85%

redistribution of blood flow is accomplished by

shunting blood away from tissues that have less metabolic activity toward more metabolically active tissue

force of ventricular contraction creates

a pressure gradient

blood moves from an area of

high concentration or low

why does blood flow down circulatory system

because of high pressure in aorta and pulmonary artery

to equalize pressure blood flows

down the circulatory system where pressure progressively drops

what is total peripheral resistance

resistance that blood encounters can determine bp, sum of resistance to blood flow by all vessels

average arterial blood pressure equation

MAP= cardiac output x TPR

blood flow equation

blood flow = pressure gradient / TPR

systolic bp normal

less than 120/80

systolic exercise bp

180-200

systolic resistance bp

400/250

diastolic bp

tpr decreases

during systole pressure

blood is ejected from ventricles, pressure peaks at end of systole

during diastole

ventricles relax, pressure reaches lowest point at end of diastole

MAP can be used to report bp

MAP= diastolic pressure + 1/3 (systolic-diastolic)

arterial bp is never

constant, rises and falls with each cycle

circulatory response to exercise

arterial bp and flow must increase, bp must not become too high or low, to satisfy blood and o2 demand of contracting muscles, cardiac output must increase

when vasodilation happens TPR

decreases