Physiology Ch:7 - The Cardiovascular system and its control

What are the major functions of the cardiovascular system? 

It delivers O2 and nutrients, removes Co2 and other waste, transports hormones and other molecules, supports temp balance, controls fluid regulation, maintains acid-base balance, and regulates immune function 

What is the function of the heart?

the heart generates pressure to drive blood through vessels

What are the four chambers of the heart?

right and left atria: top, receiving chambers

right and left ventricles: bottom, pumping chambers

How does the blood flow through the right heart? 

pulmonary circulation. pumps deoxygenated blood from body to lungs. Superior inferior venae cavae - RA - tricuspid alve - RV - pulmonary valve - pulmonary arteries - lungs 

How does the blood flow through the left heart?

Systematic circulation. Pumps oxygenated blood from lungs to body. Lungs - pulmonary veins - LA - mitral valve - LV - aortic valve - aorta

What is myocardium?

cardiac muscle. LV has the most. One fiber type (similar to type 1). Highly oxidative, high capillary density, high number of mitochondria, and striations.

What does the LV do?

Must pump blood to entire body, has the thickest walls (hypertrophy), LV hypertrophies with both exercise and disease, exercise adaptations and disease adaptations differ greatly

What are cardiac muscle fibers connected to? 

They are connected to intercalated disks. Desmosomes hold cells together. Structures called gap junctions rapidly conduct action potentials. 

What are skeletal muscle cells?

large, long, unbranched, and multinucleated. Intermittent, voluntary contractions (SOMATIC), action potential leads to CA2+ released from SR

What are myocardial cells?

small, short, branched, and one nucleus. Continuous, involuntary, rhythmic contractions (AUTONOMIC). Calcium coming into t-tubules triggers further calcium-induced calcium release from SR.

What is the myocardial blood supply? 

Right coronary artery (supplies right side of heart). Left (main) coronary artery (supplies left side of heart via left anterior descending artery (the widowmaker) and circumflex artery. 

What is heart disease?

atherosclerosis - coronary artery disease. Heart disease is where you have a disruption in blood flow to the heart itself.

What is a heart attack?

also known as myocardial infarction (MI). Occurs when blood flow to the heart muscle is blocked. This blockage usually results from a buildup of plaque (fatty deposits) in the coronary arteries. which supply blood to the heart.

How can heart attacks be treated? 

Via a clot buster medications that break up blockages and/or stent which is a small expandable tube made of metal mesh that is inserted into a narrow or blocked heat artery to keep it open.

What is intrinsic control of heart activity?

spontaneous rhythmicity: special heart cells generate and spread an electrical signal. Involved the SA node, AV node, AV bundle of His, and Purkinje fibers. Electrical signal spreads directly cell to cell within heart via gap junctions. Intrinsic HR could be 100 beats/min. Observed in heart transplant patients (no neural innervation).

What does the SA node do?

initiates contraction signal. Made of peacemaker cells in upper posterior RA wall. Signal spreads from SA node via RA/LA to AV node. Stimulates RA, LA contraction.

What does the AV node do? 

delays, then relays signal to AV bundle located in the ventricle. AV node located in RA wall near center of heart. Delay allows RA, LA to contract before RV, LV. AV bundle relays signal along RV, LV to delivers to Purkinje fibers. 

What do the purkinje fibers do?

Travels along interventricular spetum. Divides into right and left branches. Sends signal toward apex (bottom, pointy part) of heart. Fibers send signal directly into RV, LV. From terminal branches of right and left bundle branches. Spread throughout entire ventricle wall. Stimulate RV, LV contraction. 

What is extrinsic control of heart activity?

Reaches heart via the vagus nerve (cranial nerve x). Carries inhibitory impulses to SA, AV nodes. Decreases Hr, force of contraction. Decreases HR below intrinsic HR. Intrisnic HR alone is 100 beats/min. Normal resting HR (RHR) is 60 to 100 beats/min. Elite endurance athlete have 35 beats/min.

What is the sympathetic nervous system?

Opposite effects of parasympathetic. Carries excitatory impulses to SA, AV nodes. Increase Hr, force of contraction. Endocrine system can also exert similar effect. Increase HR above intrinsic HR. Determines HR during physical, conditional stress. Max possible HR is around 25 beats/min.

What are extrinsic effects of endurance training?

endurance training reduces resting HR. Autonomic neural hypothesis: shift in autonomic neural balance (sympathetic vs. parasympathetic). Intrinsic rate hypothesis: change in inherent cardiac peacemaker rate (aka electrical remodeling of the SA node itself). Latest evidence indicates that both are likely contributors.

What is an electrocardiogram (EKG)?

Recording of hearts electrical activity. Diagnostic tol for coronary artery disease. 3 basic phases: P wave - atrial depolarization. QRS complex - ventricular depolarization. T wave - ventricular repolarization.

ST segment - ventricular repolarization. PR interval - includes AV delay. QT interval - ventricular depolarization and repolarization.

What are cardiac arrhythmias?

decreased HR - bradycardia (pathological vs. exercise induced).

Increased HR - tachycardia (pathological vs. exercise induced).

What is the cardiac cycle? 

All mechanical and electrical events occurring during one heart beat. Diastole - relaxation phase. Chambers fill with blood. Lasts twice as long as systole. 

FILLLLL (diastole) - PUMP (systole) 

What is ventricular systole?

QRS complex to T wave. 1/3 of cardiac cycle. Contraction begins, ventricular pressure arises, atrioventricular valves close to prevent back-flow. (heart sound 1 “lub”). Semilunar valve open, Blood is ejected, At end, blood in ventricle = end systolic volume (ESV).

What is ventricular diastole?

T wave to next QRS complex. 2/3 of cardiac cycle. Relaxation begins. Ventricular pressure drops, semilunar valves open (heart sound 2 “dub”). Atrioventricular valves open. Fill 70% passively, 30% by atrial contraction. At end, blood in ventricle = end diastolic volume (EDV).

What is stroke volume? 

Volume of blood pumped in one heartbeat. During systole, most (not all) blood ejected. EDV - ESV = SV. 100 mL - 40 mL = 60 mL. 

What is ejection fraction?

% of EDV pumped. SV/EDV = EF. 60 mL/100 mL = 0.6 = 60%. Clinical index of heart contractile function.

What is cardiac output?

total volume of blood pumped per minute. Q = HR x SV. RHR is approx. 70 beats/min, standing SV is approx. 70 mL/beat. 70 beats/min x 70 mL/beat = 4,900 mL/min. Use L/min (4.9 L.min).

What is resting cardiac output? 

Resting cardiac output is approx. 4.2 to 5.6 L/min. Average total blood volume approx. 5 L. Total blood volume circulates once every min. 

How do you calculate stroke volume? 

It is the difference between EDV and ESV 

EDV - ESV = SV 

How do you calculate the ejection fraction?

EF = SV/EDV x 100

How do you calculate cardiac output?

Q = HR x SV

What are the special pumping actions of the heart?

functional syncytium and torsional contraction

What is functional syncytium? 

pumping of the heart as one unit, so that the fibers of the heart do not pull apart during contraction 

What is torsional contraction?

increase contractionally during intense exercise to enhance left ventricle filling

What is systole during torsional contraction?

the heart twists gradually, storing energy like a spring

What is diastole during torsional diastole?

abrupt untwisting allows atrial filling due to change in pressure gradient at most superior vs. inferior aspect of the ventricle (dynamic relaxation)

What is the vascular system?

arteries carry blood away from the heart, arteries control blood flow and feed capillaries. Capillaries provide site for nutrient and waste exchange. Venules collect blood from capillaries. Veins carry blood from venules back to heart.

What is blood pressure systolic pressure? 

highest pressure in artery (during systole). Top number approx. 110 to 120 mmHg 

What is blood pressure diastolic pressure?

lowest pressure in artery (during systole). Bottom number approx. 70 to 80 mmHg

What is general hemodynamics?

blood flow: required by all tissues

pressure: force that drives flow. Provided by heart contraction. Blood flow from region of high pressure (LV, arteries) to region of low pressure (veins, RA) 

resistance (R): force that opposes flow. provided by physical properties of vessels. radius most important factor (larger radius leads to less resistance)

easiest way to change flow is to modify resistance via change in radius through either: vasoconstriction (VC), vasodilation (VD). 

arterioles: resistance vessels, control of systemic resistance, site of most potent vasocontstriction and vasodilation. responsible for 70-80% of pdrop from LV to RA 

What is distribution of blood? 

blood flow to sites where most needed. often regions of increase metabolism to increase blood flow.

At rest (Q=5 l/min), in liver, kidneys receive  50% of Q. skeletal muscles receives approx. 20% of Q 

heavy exercise (Q=25l/min), exercising muscles receive 80% of Q via VD, flow to liver, kidneys decrease via VC. 

What are the three types of intrinsic control and what is it?

ability of local tissues to constrict or dilate arterioles thst serve them. alternation of regional flow based on need. three types: metabolic, endothelial, myogenic

what are metabolic mechanisms in intrinsic control?

vasodilation - VD, buildup of local metabolic by-products such as decreased O2 and increased CO2.

what are endothelial mechanisms? 

are secreted by vasculture endothelium itself (mostly vasodilation - VD). Nitric oxide (NO), prostaglandins, EDHF 

What are myogenic mechanisms? 

VC, VD. local pressure changes causing VC, VD. increase P to increase VC, whereas decrease P to increase VD. 

What is extrinsic control of blood flow?

upstream of local intrinsic control. redistribution of flow at organ, system level. The sympathetic nervous system innervating smooth muscle in arteries and arterioles. increased sympathetic activity to increased vasoconstriction (VC), sympathetic activity to vasoconstriction (passive VD).

What is local control of muscle blood flow?

increase of blood flow to exercising muscle to match its metabolic demand. Functional sympatholysis inhibition of sympathetic vasoconstriction by reducing vascular responsiveness to x-adrenergic receptor actvation. Allows muscle to overcome vasoconstriction and increase blood flow

What is distribution of venous blood? 

At rest, veins contain 2/3 of blood volume. High capacity to hold blood volume, elastic, balloon like vessel walls. Blood reservoir. Venous reservoir can be liberated, sent back to heart and into arteries. Sympathetic stimulation, venoconstriction. 

What is intrinsic control of blood pressure?

blood pressure maintained by autonomic reflexes. Baroreceptors are sensitive to changes in arterial pressure. Afferent signals from baroreceptors to brain. efferent signals from brain to heart, vessels. adjustment of arterial pressure back to normal

how does blood return to the heart?

the upright posture makes venous return to heart more difficult. Assisted by 3 mechanisms: one-way venous values, muscle pump, respiratory pump.

What is blood?

3 major functions: transportation (O2, nutrients, waste), temp regulation, acid-base (pH) balance. Blood is made of plasma and formed elements. Plasma makes up 55% to 60% of blood volume. Formed elements (40% to 45%).

What do plasma and formed elements consist of?

plasma: 90% water, 7% protein, 3% nutrients, ions, etc.

Formed elements: red blood cells (erkocytes: 99%), white blood cells (leukocytes : <1%), platelets (1%)

What is hematocrit?

total % volume composed of formed elements. Low is low, low of formed elements. High could be sign of dehydration.

What are red blood cells?

No nucleus, unable to reproduce. Replaced regularly via hematopoiesis, life span 4 months, produced and destroyed at equal rates.

What is hemoglobin?

oxygen-transporting protein in red blood cells (4 oz per hemoglobin). heme (pigment, iron, O2) and globin (protein). 250 million hemoglobin per red blood cell. oxygen carrying: 20 mL O2 per 100 mL blood

What is blood viscosity? 

thickness of blood (due to red blood cells), twice as viscous as water. Viscosity increased, and hematocrit increased. Plasma volume must increase as red blood cells increase. Occurs in athletes after training, acclimation. hematocrit and viscosity remain stable. Otherwise, blood flow or O2 transport must suffer.