Ch. 9 Flashcards
Human circulatory system is a considered closed because?
veins and arteries are continuous with each other through smaller vessels
what is considered the smallest most numerous of blood vessels?
capillaries
All exchanges of O2 and CO2, and nutrients occur where?
Tissues
What is mixed venous blood?
mixture of venous blood from both upper and lower body that accumulates in the right side of the heart
The heart is often considered to be two pumps in one. What are the two pumps composed of?
1 pump: right atrium and right ventricle
2 pump: left atrium and left ventricle
The right side of the heart is separated from the left side by muscular wall called? and what is its purpose?
inter-ventricular septum; prevent the mixing of blood from two sides of the heart
What is the right and left AV valve called?
R: tricuspid valve L: bicuspid valve
Backflow from arteries into ventricles is prevented by what?
pulmonary semilunar valve (R ventricle) aortic semilunar valve (L ventricle)
blood is delivered from right heart into lungs through what?
pulmonary circuit
What happens to the blood when it reaches lungs?
O2 is loaded into the blood and CO2 is released; oxygenated blood travels to left side of heart and is pumped into tissues of body via systemic circuit
What are the purposes of cardiovascular system?
- transport of O2 to tissues and removal of waste
- transport of nutrients to tissues
- regulation of body temperature
what is myocardium responsible for?
contracting and forcing blood out of the heart
where does myocardium receive its blood supply?
R and L coronary arteries
What are intercalated discs?
intercellular connections permit the transmission of electrical impulses from one fiber to another
What is functional syncytium?
when one heart fiber is depolarized to contract, all connecting heart fibers become excited and contract as a unit
When does atrial contraction occur?
occurs during ventricular diastole
Approximately how many seconds after atrial contraction does ventricle contract?
0.1 seconds
A rising heart rate results in what for systole and diastole?
a rising heart rate results in a greater time reduction in diastole whereas systole is less affected
Where is blood pressure the greatest?
blood pressure is greatest within the arteries
What is blood pressure?
Blood pressure is force exerted by blood against the arterial walls and is determined by how much blood is pumped and the resistance to blood flow
arterial blood pressure can be estimated by use of what tool?
sphygmomanometer
What is normal BP for female and males?
F: 110/70; M: 120/80
What is systolic blood pressure?
pressure generated as blood is ejected from the heart during ventricular systole
What is pulse pressure?
difference between systolic BP and diastolic BP
average pressure during cardiac cycle is called? what is its purpose?
mean arterial pressure; determines the rate of blood flow through the systemic circuit
What is the equation for mean arterial pressure?
DBP + 0.33( pulse pressure)
why can’t the MAP equation be used to compute MAP during exercise?
Bc it is based on the timing of the cardiac cycle at rest
The time spent in systole occupies what % of total cardiac cycle at rest; during maximal exercise, systole account for what % of total cardiac cycle time?
33% at rest; 66% during exercise
what blood pressure is considered hypertension?
140/90
Hypertension can be classified into two categories:
- primary or essential hypertension (95% of all hypertension cases in US)
- secondary hypertension (caused as a result of some known disease)
What health complications can hypertension cause?
- increase workload on left ventricle (left ventricular hypertrophy)
- major risk for developing arteriosclerosis and heart attacks
Mean arterial blood pressure is determined by two factors:
- cardiac output
2. total vascular resistance
What is the equation for mean arterial blood pressure?
MABP: cardiac output x total vascular resistance
What factors contribute to increase of blood pressure?
- increase in blood volume
- increase in heart rate
- increase in stroke volume
- blood viscosity increases
- increases in peripheral resistance
How is blood pressure regulated?
Acute regulation of BP is achieved by sympathetic nervous system; long term regulation of BP is primarily function of kidneys
How does kidney regulate BP
controlling blood volume
Where is the cardiovascular control center located?
medular oblongata
What happens when there is an increase in arterial pressure?
- triggers baroreceptors to send impulses to CCC which responds by decreasing sympathetic activity
- results in lowering cardiac output/or vascular resistance
- lowers blood pressure
Spontaneous electrical activity is limited to special region located where?
right atrium
What is the pacemaker for the heart called?
SA node (sinoatrial node)
What is an electrocardiogram? anaylsis during exercise can help detect what?
recording of electrical changes that occur in the myocardium during cardiac cycle; help detect coronary artery disease
What does the P wave indicate?
The first deflection which indicates the depolarization of atria
What does the QRS complex indicate?
represents the depolarization of ventricles (occurs 0.10 secs after P wave)
What does the T wave indicate ?
repolarization of the ventricles
When does the QRS complex occur? when does T wave occur?
QRS: occurs at the beginning of systole
T wave: occurs at beginning of diastole
What causes the rise and downfall in intraventricular pressure?
rise at beginning of systole: results in first heart sound due to closure of AV valve
downfall at end of systole: results in second heart sound due to closure of pulmonary and aortic semi lunar valves
What is cardiac output?
Q is product of heart rate and stroke volume
Q= HR x SV
During exercise, increase in CO is due to increase in BOTH what?
strove volume and heart rate
Two most prominent factors that influence heart rate are:
parasympathetic and sympathetic nervous system
how does parasympatheic nervous system act as a braking system in slowing down heart rate?
- vagus nerve make contact with both SA and AV node
- when stimulated these nerve ending release acetylcholine which causes decrease in activity of both SA and AV nodes due to hyper-polarization
- reduced heart rate
what is parasympathetic tone?
even at rest vagus nerves carry impulses to SA and AV node
sympathetic fibers reach heart by means of what?
cardiac accelerator nerves which innervate both SA node and ventricles
Sympathetic nervous system process
- cardiac accelerator nerves innervate both SA node and ventricles
- endings of these fibers release norepinephrine upon stimulation
- act on beta receptors in heart and cause an increase in rate rate and myocardial contraction
At rest, normal balance between parasympathetic tone and sympathetic activity to heart is maintained by?
cardiovascular control center (medulla oblongata)
What does the cardiovascular control center do when there is an increase in resting blood pressure above normal level?
- stimulates pressure receptors in the carotid arteries and the arch of the aorta
- in return sends impulses to the cardiovascular control center
- in response the cardiovascular control center increases parasympathetic activity to the heart to slow the heart rate and reduce cardiac output
- this reduction in CO causes blood pressure to decline back toward normal
What does the cardiovascular control center do when there is an increase in right atrial pressure?
- signals the CCC that there is an increase in venous return
- in order to prevent backup of blood in systemic venous system, an increase in cardiac output must result
- CCC responds by sending sympathetic accelerator nerve impulses to the heart which increase heart rate and cardiac output
- results in increase in cardiac output lowers right atrial pressure
Regulatory reflexes what influences regulation of heart rate:
- change in body temperature
- pressure receptors located in right atrium
3, increase in resting blood pressure
Heart rate is regulated by what?
autonomic nervous system
Heart rate variability is?
refers to the variation in time between heartbeats
The time interval between two heart beats can be measured as what kind of time interval using ECG
R-R time interval
What is considered to be a good index of healthy balance between sympathetic and parasympathetic nervous systems for HRV
a wide variation in HRV
what does a low HRV indicate?
indicates imbalance exists in autonomic regulations
What is the physiological significance of HRV?
time variation between heartbeats reflects autonomic balance and is an excellent noninvasive screening tool for many diseases
What are some risks for low heart rate variability?
- independent risk factor for the development of cardiovascular disease, including heart failure, myocardial infarction and hypertension
What is the physiological cause of low HRV?
two opposing acting branches of the autonomic nervous system is referred to as sympathovagal balance and is reflected in beat to beat changes in cardiac cycle
what are some factors that influence sympathovagal balance and thus affect HRV?
- w/ advancing age or some disease states there is a decrease in parasympathetic tone at rest OR increase in sympathetic nervous system outflow
- this results in disturbance in sympathovagal balance and a decrease in HRV
What are some examples of diseases that promote a decrease in HRV?
- depression, hypertension, heart disease, and myocardial infarction
- physical inactivity
stroke volume at rest or during exercise is regulated by 3 factors:
- end diastolic volume (volume of blood in ventricles at end of diastole)
- average aortic BP
- strength of ventricular contraction
What is referred to as preload?
End diastolic Volume
How does EDV influence stroke volume?
strength of ventricular contractions increased with enlargement of EDV
What is the Frank Starling Law of the heart?
- relationship between stroke volume and ventricular contraction
- increase in EDV results in lengthening of cardiac fibers which improves force of contraction
How does the fiber length influence cardiac contractility?
- increase in length of fibers increases number of myosin crossbridge interaction with actin, resulting in increased force production
- rise in cardiac contractility results in increase in amount of blood pumped per beat
What is the principle variable that influences EDV?
- rate of venous return to the heart
- increase in venous return results in rise in EDV and increases in stroke volume
- increase in EDV plays key role in increase in stroke volume observed during UPRIGHT exercise
What factors regulate venous return during exercise?
- venoconstriction
- muscle pump
- respiratory pump
How does venoconstriction increase venous return?
- decreases the diameter of vessels and increasing the pressure within vein
- end result is to drive blood back to heart
- occurs via sympathetic constriction of smooth muscle in veins
How does muscle pump regulate venous return during exercise?
- result of the mechanical action of rhythmic skeletal muscle contractions
- when muscle contract during exercise, they compress vein and push blood back to heart
- between contractions, blood refills the veins and process is repeated
- during sustained muscular contractions, muscle pump cannot operate
How does respiratory pump regulate venous return during exercise?
- during inspiration, pressure within chest decreases and abdominal pressure increases
- creates a flow of venous blood from abdominal region into thorax and promotes venous return
- respiratory pump is a dominant factor that promotes venous return to heart during UPRIGHT exercise
In order to eject blood, pressure generated by left ventricle must exceed what?
pressure in aorta
How does increase in aortic pressure impact stroke volume?
decrease in stroke volume
arteriole dilation in working muscles impacts afterload how?
it minimizes afterload and makes it easier for heart to pump a large volume of blood
increase sympathetic stimulation of heart impacts stroke volume how?
- increases stroke volume at any level of EDV
- sympathetic stimulation in creases ventricular contractibility via increase level of intracellular ca, resulting in higher myosin cross bridge interaction with actin
During upright exercises, the exercise induced increases in Stroke volume occurs due to:
increases in EDV and cardiac contractility due to circulating catecholamines and or sympathetic stimulation
equation for cardiac output
cardiac output = cardiac rate x stroke volume
- stroke volume: contraction strength, EDV, mean arterial pressure
- cardiac rate: parasympathetic and sympathetic nerve
Blood is composed of two principle components:
plasma and cells
Plasma contains what?
ions, proteins, and hormones
cells that make up blood are what?
RBC, platelets, and white blood cells
what is hemoglobin?
used for transport of oxygen
what are the roles of platelets and white blood cells?
platelets: important role in blood clotting
WBC: preventing infections
What is hematocrit?
- the % of blood that is composed of cells
- hematocrit is principally influenced by increases or decreases in RBC numbers
- average hematocrit for males: 42%
- average hematocrit for females: 38%
Since blood is more viscous than water, what is a major contributor to viscosity?
- [] of RBCs found in blood
- during period of anemia viscosity of blood is lowered
What is the relationship among pressure, resistance and flow?
- rate of flow is proportional to pressure difference between two ends of tube
- blood flow is directly related to pressure differences across the tube
- increase in pressure will increase flow
- flow rate is DIRECTLY proportional to pressure difference across the system but INVERSELY proportion to resistance
What is the equation for blood flow?
BF = change in pressure/resistance
- blood flow can be increased by either an increase in BP or decrease in resistance
What factor contribute to resistance of blood flow?
- resistance is DIRECTLY proportional to length of vessel and viscosity of blood
MOST IMPORTANT VARIABLE determining vascular resistance is what?
diameter of blood vessel because vascular resistance is inversely proportional to the fourth power of the radius of a vessel
what is equation for resistance?
Resistance = (length x viscosity)/radius^4
- reducing radius of blood vessel by 1/2 would increase resistance 16 fold
Where does the greatest vascular resistance in blood flow occur?
arterioles; approx 70 to 80% of decline in arterial pressure occurs across arterioles
Increased Oxygen delivery to exercising skeletal muscle is accomplished by two mechanisms:
- increased cardiac output
2. redistribution of blood flow from inactive organs to skeletal muscle
How does exercise impact cardiac output?
- CO increases during exercise in direction proportion to metabolic rate
- increase in CO during exercise in upright position is achieved by increase in both stroke volume and heart rate
In untrained or moderately trained subjects, SV does not increase beyond a workload of?
40-60% of VO2 max
At work rates greater than 40-60% VO2 max, rise in CO is achieved by
increases in heart rate alone
Stroke volume does not plateau in endurance athletes because
they have improved ventricular filling during heavy exercise due to increased venous return
Decrease in maximal heart rate with age in YOUNG ADULTS can be estimated by what formula:
Max HR: 220 - age
What formula is used for older adults and young children to predict maximal heart rate?
Max HR: 208 - 0.7 x age (years)
What does the arterial mixed venous oxygen differene (a - vo2) represent?
- amount of O2 that is taken up from 100 ml of blood by tissues during one trip around systemic circuit
- increase in difference during exercise is due to increae in amount of O2 taken up and used for oxidative production of ATP
What is Fick’s equation:
Vo2 = Q (aka CO) x (a-Vo2 diff)
- VO2 is equal to the product of CO and the Vo2 diff
Change in blood flow to muscle and the splanchnic circulation is dictated by
exercise intensity
At rest, what percent of total cardiac output is directed toward skeletal muscle?
15-20%
What percent of total cardiac output is directed toward skeletal muscle during maximal exercise?
80-85%
During heavy exercise, the percentage of total cardiac output that goes to brain is…
reduced compared to at rest
Even though the total cardiac output that reaches myocardium is the same during maximal exercise as it rest, the total coronary blood flow is
increased due to the increase in cardiac output during heavy exercise
what happens to skin blood flow during maximal exercise?
increases during both light and moderate exercise, but decreases during maximal exercise
what happens to blood flow to abdominals during heavy exercise?
it is reduced; important bc shifting of blood flow away from less active tissues and toward skeletal muscles
At rest, what percent of capillaries in skeletal muscles are open at any one time?
50-80%; however during intense exercise, almost ALL all capillaries in contracting muscle are open resulting in increased O2 delivery to contracting muscle fibers
What is autoregulation?
- the increase in muscle blood flow that occurs during exercise is regulated by several factors that promote vasodilation
- most important factor in regulating blood flow to muscles during exercise
What determine the overall need for blood flow to muscles?
- number of motor units recruited
2. intensity of exercise
What factors are responsible for the auto regulation of muscle blood flow to match the metabolic demand?
skeletal muscle blood flow is controlled by an interaction between vasodilators including nitric oxide, prostaglandins, ATP, adenosine, and endothelium derived hyperpolarization factors
What are the jobs of ATP & adenosine, nitric oxide & prostaglandins, and endothelium derived hyperpolarization factors?
- Nitric oxide and Prostaglandins: potent vasodilators
- ATP and adenosine: increase muscle blood flow during exercise
- endothelium: promote hyperpolarization of smooth muscle cells in arterioles resulting in smooth muscle relaxation
Even though vascular resistance in skeletal muscle decreases during exercise, what happens to vascular resistance to flow of visceral organs and inactivity tissue?
- increases due to an increase sympathetic output of these organs, which is regulated by CCC
- blood flow to viscera can only decrease only 20-30% of resting values
