Week 10

Question 1

Define ischemic. What causes myocardial ischemia?

Answer 1

Ischemic: tissue with deficient oxygen supply because of inadequate blood flow (reduced, not blocked. blocked = infarct)

Most common cause of myocardial ischemia is atherosclerosis of the coronary arteries. Inadequacy of blood flow is relative to tissues metabolic requirement, so sufficient flow may be possible at rest but not when stressed by exercise or emotion! Increased sympathoadrenal system = high heart rate and blood pressure = high oxygen requirement. Mental stress can constrict arteries by damaged endothelium which normally prevents constriction

Question 2

What is angina pectoris? what drugs relieve this condition?

Answer 2

Substernal (chest) pain that may be referred to the left arm and shoulder. This is a result of myocardial ischemia that increases blood lactic acid (produced by anaerobic metabolism). Nitroglycerin (dynamite!) produces vasodilation to improve heart circulation and decreases ventricle work.

Question 3

What happens when myocardial cells perform anaerobic respiration for more than a few minutes?

Answer 3

They cannot metabolize anaerobically for very long and prolonged ischemia causes necrosis. This sudden and irreversible injury is a myocardial infarction (heart attack). The damage is permanent as myocardial cells do not divide to replace dead cells. Noncontractile scar tissue forms at the infarct

Question 4

What greater threat occurs AFTER a myocardial infarction?

Answer 4

Reperfusion injury. After heart becomes re-perfused with blood, larger numbers of cells die by apoptosis due to Ca2+ accumulation and production of superoxide free radicals. This leads to a great increase in the size of the infarct and weakens ventricle walls to become thin and distend under pressure

Question 5

What is the effect of a myocardial infarction on an ECG?

Answer 5

Ischemia results in depression of the ST segment

Atherosclerotic plaques that induce thrombi, that totally block coronary artery, causes elevated ST segment

Question 6

What tests would be performed to confirm presence of a myocardial infarction?

Answer 6

Rise in troponin I in blood (primary test!)
Creatine phosphokinase MB (CPK-MB) in blood
lactate dehydrogenase (LDH) in blood

Question 7

What is the term for abnormal heart rhythms? Term for fast and slow and what normally causes each?

Answer 7

Arrhythmia = abnormal heart rythm (detected by ECG).

Tachycardia = faster than 100 bpm. Sympathetic nervous system during exercise or emergencies.

Bradycardia = slower than 60 bpm. Athlete’s Bradycardia result of parasympathetic inhibition of SA node.

Question 8

What can cause abnormal tachycardia?

Answer 8

Fast pacing by the atria (e.g. drugs) and abnormally fast ectopic pacemakers
Paraoxysmal Supraventricular Tachycardia (SVT) is sporadic tachycardia that originates in the atria and produces fast heartbeat. Often treated with adenosine
Ventricular Tachycardia is when ectopic pacemakers in the ventricles are abnormally fast and cause rapid beating independent of atria. This can quickly lead to ventricular fibrillation and death.

Question 9

Define flutter and fibrillation. What is the result of fibrillation in each chamber?

Answer 9

Flutter = coordinated rapid contractions quickly degenerates into
Fibrillation = uncoordinated rapid contractions (danger!)

Atrial fibrillation makes atria ineffectual, but since ventricles fill 80% of end-diastolic volume before atrial contraction, atria fibrillation only reduces cardiac output by about 15%. The main concern is thrombi formation leading to stroke (Eddie currents have low oxygen and lead to clotting)

Ventricular fibrillation will cause death in a few minutes due to inability to pump blood and deliver oxygen to the brain/heart. Fibrillation culminates in Asystole (cessation of beating)

Question 10

Normal treatment for atrial fibrillation is _______ but an alternative to drug therapy is ______

Answer 10

Antithrombitic and anti arrhythmia drugs, such as Warfarin

Percutaneous catheter ablation. Destroys atrial tissue around the pulmonary veins (usual source of electrical abnormality) and electrically separates this area from the surrounding tissue of the left atria

Question 11

What causes ventricular fibrillation?

Answer 11

Circus Rhythms: continuous recycling of electrical waves. Normally prevented by refractory period of entire myocardium, but chaotic electrical activity messes this up. Focal Excitation occurs when a region outside the SA node is damaged and spontaneously depolarizes. Reentry is when an action potential can be continuously regenerated and conducted along a pathway (like around a scar) not in a refractory phase. An external shock (like a wall outlet!) in the middle of the T wave also causes fibrillation

Question 12

Describe how fibrillation can be stopped

Answer 12

Electrical Defibrillation: electric shock depolarizes all of the myocardial cells at the same time, causing them to enter refractory state. Circus rhythms stop and SA node (hopefully) starts up normal rhythm again.
Implantable Converter-defibrillator can be implanted in a patient to detect when ventricular fibrillation occurs and deliver defibrillating shocks.

Question 13

Three basic functions of lymphatic system

Answer 13

Transports interstitial fluid back to the blood (eventually draining in left/right subclavian veins)
Transport absorbed fat from small intestine to blood
Provide immunological defense via lymphocytes

Question 14

What is fluid called once it enters the lymphatic capillaries? where is the fluid carried?

Answer 14

Lymph. From merging lymphatic capillaries, lymph is carried into larger lymphatic vessels called lymph ducts. The ducts empty into the thoracic duct or the right lymphatic duct which then drain into the left and right subclavian veins. Lymph is filtered through lymph nodes and then returns to the cardiovascular system.

Question 15

Describe the structure of lymph ducts. How do they move fluid?

Answer 15

Walls have same three layers and valves as veins. Fluid is moved by peristaltic waves of contraction and by contraction of skeletal muscle. Peristaltic waves are produced by smooth muscle in the lymph ducts that contain a pacemaker that initiates action potentials and entry of Ca2+, stimulating contraction. This action increases in response to stretch of the vessel.

Question 16

What is contained in the lymph nodes and lymphoid organs? name the lymphoid organs.

Answer 16

Lymph nodes contain phagocytic cells which remove pathogens and germinal centers to produce new lymphocytes. Tonsils, thymus, and spleen are the lymphoid organs and also contain germinal centers for lymphocyte production.

Question 17

What harmful process can the lymphatic system cause? What symptom would this produce in the lymph nodes?

Answer 17

The lymphatic system may also help transport cancer cells and help cancer spread or metastasize. Lymph nodes are hard and not painful if cancerous. If lymph nodes are painful and swollen, that is infection.

Question 18

What determines cardiac output and what is the cardiac output of each ventricle? What is total blood volume and how does that relate to the cardiac output?

Answer 18

Cardiac output is the volume of blood pumped peer minute and is equal to stroke volume x cardiac rate. Normal output is 5.5 L per minute in each ventricle. Output of the right and left needs to be the same, but since right (pulmonary) is a shorter circulation it has low resistance, low pressure, and high blood flow compared to systemic circulation

Total blood volume averages 5.5 L, therefore each ventricle pumps a total blood volume each minute! It takes a minute for a drop of blood to complete the systemic and pulmonary circuits.

Question 19

What regulates the cardiac rate and when does this regulation occur?

Answer 19

Sympathetic (in atrial musculature, not SA node) and parasympathetic innervations (in SA node) which are continuously active to some degree.
(nor)Epinephrine bind Beta 1 adrenergic receptors to stimulate cAMP production and activate HCN and Ca2+ channels of pacemaker cells to increase diastolic depolarization = faster cardiac rate.
Vagus nerve releases acetylcholine to bind muscarinic receptors and open K+ channels, countering the inward Na+ diffusion and slowing diastolic depolarization = slower cardiac rate. Vagus is always active and keeps rate slower than the 90-100 bpm that it would be without vagus. Vagus = main rate determiner

Question 20

What is the name for mechanisms that influence cardiac rate?

Answer 20

chronotropic effect. Increase in rate is a positive chronotropic effect (sympathetic innervation) and decrease in rate is a negative chronotropic effect (parasympathetic innervation)

Question 21

What controls autonomic innervation of the heart?

Answer 21

the Cardiac Control Center in the medulla oblongata. This is in turn affected by higher brain areas and by sensory feedback from pressure receptors called Baroreceptors in the aorta and carotid arteries. Through this, a fall in blood pressure can produce an increase in heart rate

Question 22

What three variables determine stroke volume

Answer 22

1. End Diastolic Volume (EDV): the volume of blood in the ventricles at the end of diastole (before systole) also called the *Preload (workload imposed prior to contraction). Directly proportional to stroke volume
2. Total Peripheral Resistance: frictional resistance or impedance to blood flow in the Arterioles. Presents impedance after ventricle contracts and is thus called an *Afterload. Inversely proportional to stroke volume
3. Contractility: strength of ventricular contraction. Directly proportional to stroke volume

Question 23

What causes increased total peripheral resistance? What is the effect on the heart if total peripheral resistance is high?

Answer 23

High arterial blood pressure = high total peripheral resistance. Can be caused by lots of things, such as vasoconstriction in the cold or atherosclerosis.

Result is an increased after load and decrease in stroke volume. Ih healthy people, ventricles will compensate by increasing contraction strength. Inability to compensate will lead to congestive heart failure

Question 24

**Explain what the Frank-Starling Law of the Heart is

Answer 24

Strength of ventricular contraction is directly related to the end-diastolic volume. Even when the heart is removed from the body, there is still a built-in, intrinsic, property of the heart that will increase contraction strength if EDV is increased. This is one of the mechanisms for intrinsic control of contraction strength

Question 25

**What are the 3 mechanisms for intrinsic control of contraction strength (ensures that contraction strength and stroke volume increase when needed)
(maybe 4? I’m not convinced the fourth is actually something different)

Answer 25

1. Frank-Starling Law: as EDV rises so does contraction strength. High EDV causes myocardium to be increasingly stretched so actin filaments overlap with myosin only at the edges of A bands. This increases interactions between actin and myosin = more force for contraction. (unlike skeletal muscles!! resting is not ideal length)
2. Stretching causes increased RyR2 sensitivity = more Ca2+ release = stronger contraction
3. Anrep effect: increased NCX activity = increase Ca2+ gradually
   (4. Stretched cardiac muscle is more sensitive to Ca2+)

Question 26

Explain how the heart adjusts to a rise in total peripheral resistance

Answer 26

Rise in peripheral resistance causes decrease in stroke volume. More blood remains in ventricle and EDV is greater for the next cycle. The ventricle is stretched to a greater degree in the next cycle and contracts more strongly to eject more blood.

Question 27

What effects the rate at which atria and ventricles are filled with blood?

Answer 27

Total blood volume and (more importantly) venous pressure. Venous pressure is the driving force for the return of blood to the heart. Venous return occurs because pressure is highest in venules and lowest at the venae cavae (at right atrium) and the pressure difference promotes blood flow to the heart. Sympathetic nerve activity (stimulates smooth muscle contraction), the skeletal muscle pump, and the respiratory pump also aid venous return.

Question 28

What does compliance mean? Which vessels have greater compliance and what is the result of that characteristic? What names are given to vessels with high/low capacitance

Answer 28

Compliance means that pressure will cause increased distention or expansion. Veins have thinner, less muscular walls and have a higher compliance, meaning they can hold more blood. *Two thirds of total blood volume is in the veins!

Veins are thus capacitance vessels and arterioles are resistance vessels

Question 29

Review the distribution of fluid in the body. *What determines distribution of water in/out tissues?

Answer 29

two thirds is intracellular
one third is extracellular
Of the extracellular fluid, 80% is in tissues (interstitial fluid) and 20% is in blood plasma

Blood pressure causes fluid to move from plasma to interstitial while Osmotic forces draw water from tissues to vascular system

Question 30

Distribution of extracellular fluid between plasma and tissue is in a state of _________

Answer 30

Dynamic equilibrium. Interstitial fluid is not a stagnant pond, it is continuously circulating between tissue and blood. This gives tissue cells a fresh supply of nutrients and constant waste removal

Question 31

What is the net filtration pressure and how does it cause filtration

Answer 31

Net filtration pressure = hydrostatic pressure of the blood in capillaries minus hydrostatic pressure of tissue fluid outside capillaries.
Normally, hydrostatic pressure of the interstitial fluid is kept low by removal of fluid through drainage into lymphatic vessels. So the net pressure stays high and keeps the fluid filtering within capillaries.

Question 32

What causes there to be different concentrations in interstitial fluid and plasma? What is the result of the different concentrations?

Answer 32

Most molecules are filtered along with water through capillary pores and so have the same concentration in interstitial fluid and plasma. Proteins, however, are restricted from filtering and have a higher concentration in plasma. The osmotic pressure exerted by plasma proteins (albumin!) create the colloid osmotic pressure. The colloid osmotic pressure difference between the plasma and interstitial fluid is called the oncotic pressure. Oncotic pressure = colloid osmotic pressure of the plasma (because interstitial pressure is negligible) and has a value of 25 mmHg, and favors movement of water into capillaries.

Question 33

What determines if fluid moves into or out of capillaries? Explain where each activity occurs and why

Answer 33

The magnitude of the net filtration pressure determines flow of fluid in/out capillaries. Forces that affect fluid distribution across capillary are Starling Forces. As blood travels from arteriolar to venular capillaries the hydrostatic (blood) pressure decreases. This causes Starling forces to be positive at the arteriolar end, meaning fluid moves out of the capillary, and negative at the venular end, meaning fluid moves into the capillary.
Arteriolar capillary = fluid flows out
Venular capillary = fluid flows in

Question 34

*What are the two forces that determine fluid movement in capillaries? what creates them?

Answer 34

Blood Pressure (created by arterioles and heart activity?) and Osmotic pressure (created by concentration of plasma proteins)

Question 35

Why is the return of fluid at the venular ends of capillaries not equal to the amount of fluid leaving capillaries at arteriolar ends?

Answer 35

About 10-15% of the fluid is returned to the blood by way of the lymphatic system instead of the vascular system (which gets 85-90%)

Question 36

What causes edema (excess fluid in tissues)? 6 possible causes

Answer 36

1. High arterial blood pressure
2. Venous obstruction: thrombus or mechanical compression of veins (pregnancy)
3. Leakage of plasma proteins into interstitial fluid: allergies and inflammation
4. Myxedema: excessive glycoprotein production in ECM, caused by hypothyroidism
5. Decreased plasma protein concentration: result of liver disease (not making proteins) or kidney disease (excreting proteins)
6. Obstruction of the lymphatic drainage: due to parasitic larvae in elephantiases or surgery (especially breast surgery)

Question 37

How does urine production in the kidneys occur? (hint: similar to another process) What happens to most of the filtrate produced by the kidneys?

Answer 37

formation of urine begins the same as formation of interstitial fluid, by filtration of plasma through capillaries. These fenestrated capillaries are called Glomeruli and the filtrate they produce is mostly reabsorbed. 98 to 99% is reabsorbed to vascular system and 1-2% excreted. About 1.5 L of urine is excreted daily, so a small decrease in reabsorption (say from 99% to 98%) actually ends up with double the urination, a whole liter more.

Question 38

What mechanisms regulate the percentage of glomerular filtrate that is reabsorbed (aka regulate blood volume)

Answer 38

1. Antidiuretic hormone (ADH) or arginine vasopressin: released in increased plasma osmolality (dehydration or salt intake). ADH stimulates water reabsorption from filtrate, decreasing urination.
2. Aldosterone: secreted during salt deprivation (low blood volume) to stimulate reabsorption of salt by kidneys (“salt retaining hormone”). Increases blood volume but no change in plasma osmolality! Salt and water reabsorbed in equal amounts = no dilution.
3. Sympathetic nervous system: atria stretch receptors detect increased blood volume and increase sympathetic heart activity while decreasing sympathetic kidney activity = vasodilation and increased blood flow of renal arteries, promoting more urination and lowering the blood volume

Question 39

Review the mechanism of antidiuretic hormone, from production to stimulation to removal from system.

Answer 39

Produced in hypothalamus (supraoptic and paraventricular nuclei) then transported (via hypothalamo-hypophyseal tract) to posterior pituitary and stored. Release is stimulated by increased plasma osmolality (dehydration or salt intake) which triggers osmoreceptors in the hypothalamus. Thirst sensation occurs and ADH is released to stimulate water reabsorption from kidney filtrate. Person drinks more, urinates less, so blood volume raises and dilutes plasma concentration. Dilution inhibits ADH release and more urine is excreted (water = diuretic). Raised blood volume inhibits ADH release too as stretch receptors in the cardiovascular system signal inhibition, causing more water to be eliminated by kidneys. Low blood volume decreases stretch receptors = more ADH secretion = retain water.

Question 40

What hormonal response occurs when the blood volume rises and the atria stretches?

Answer 40

Stretch receptors in the atria stimulate secretion of Atrial Natriuretic Peptide which increases salt and water excretion in the urine and lowering blood volume
(Left atria, among other structures, stretch receptors also stimulate inhibition of ADH and lowering of blood volume)

Question 41

*Describe the mechanism of Aldosterone release from the kidneys

Answer 41

Renin-Angiotensin-Aldosterone System: salt deprivation lowers blood volume and signals the Juxtaglomerular Apparatus to secrete Renin enzyme into the blood. This cleaves Angiotensinogen to Angiotensin I, which passes through lung capillaries where Angiotensin Converting Enzyme (ACE) converts it to Angiotensin II. Angiotensin II is a vasoconstrictor that causes arteries to contract and thus increases blood pressure. It also promotes a rise in blood volume by stimulating the thirst center in the hypothalamus and the secretion of Aldosterone from the adrenal cortex.
End result = drink more, retain NaCl, urinate less, increase blood volume and blood pressure

Question 42

What is included in extrinsic regulation of the blood flow?

Answer 42

Extrinsic regulation is control by the autonomic nervous system and endocrine system. For example, angiotensin II causes vasoconstriction (so does ADH/vasopressin, but its negligible)

Question 43

most reliable birth control is

Answer 43

Abstinence - no sexual intercourse.

Question 44

Describe the Natural Family Planning method of birth control. How effective is it

Answer 44

75% effective if couple doesn’t work as a team, but 99% effective if couples follow guidelines and cooperate in a stable arrangement.

Track the woman’s ovulation by measuring basal body temperature (slight drop during LH peak, sharp rise after LH peak and remains high for luteal phase), detect spinnbarkeit, detect mittleshmerz, detect rising and softening of the cervix at ovulation along with increased cervical diameter, monitor mood changes (increase libido during ovulation). Only have intercourse AFTER ovulation during luteal phase for absolute lowest risk

Question 45

Describe the oral contraceptive method of birth control. How effective is it? What side effects may occur?

Answer 45

Synthetic estrogen and progesterone are taken once day for three weeks after the last day of menstruation. Rise in ovarian steroids causes negative feedback on gonadotropin secretion and ovulation never occurs. The entire cycle is a false luteal phase! The endometrium does thicken in response so women take placebo pills for the fourth week to cause a fall in estrogen and progesterone and a mini-menstruation to prevent overgrowth of endometrium.

98% effective. Blood clots (especially in smokers) are a side effect, also breast cancer risk and cervical cancer risk. Newer pills may reduce endometrial and ovarian cancer risk and osteoporosis.

Question 46

Describe non-oral hormone contraceptives

Answer 46

Vaginal Rings and Contraceptive Patches deliver contraceptive steroids through a mucous membrane or the skin, respectively. A non-oral route bypasses the liver and permits lower doses, causing fewer side effects. Depo-Provera is an injectable hormone contraceptive that is only administered once every 3 months. Long-Acting Reversible Contraceptive Devices (LARCs) may also employ hormones, such as Intrauterine Devices (IUDs) and Subdermal Hormonal Implants. Both contain hormones such as progestin that inhibit ovulation.

Question 47

Describe the Rhythm method of contraception. How effective is it?

Answer 47

Woman tracks cyclic changes in basal body temperature that occur in response to cyclic changes in ovarian hormones to know when ovulation is occurring. On the day of LH peak, as estradiol declines, basal body temp drops. One day after LH peak, temp rises as progesterone secretion occurs. Temp remains elevated through the luteal phase.
Another method includes examining cervical mucus that becomes sticky spinnbarkeit at ovulation.
Can be unreliable because cycles are variable and predicting next month’s cycle is difficult

Question 48

Describe intrauterine devices (3 types)

Answer 48

IUDs are small pieces of plastic inserted by a physician in the uterus. Non-copper IUDs alter the uterine environment so fertilization will not occur, and if it does implantation will not occur. Copper IUDs contain copper ions that kill sperm. Hormone IUDs have hormones that prevent ovulation and implantation.

Question 49

Describe the diaphragm and cervical cap contraceptive methods

Answer 49

Diaphragm is a soft lates cup that lodges behind the pubic bone and fits over the cervix. It is inserted into the vagina no more than 2 hours before sex along with spermicidal jelly. It should be left in place for 6 hours after sex.
The Cervical Cap is a mini diaphragm that fits over just the cervix and is used with spermicidal jelly.
These barrier methods also offer STD protection (along with condoms both male and female)

Question 50

Describe contraceptive vaccines

Answer 50

In development now. One example is a vaccine against hCG, a hormone necessary for implantation of the embryo. hCG is not normally present so there is not autoimmune risk, but immunization does wear off with time. Another option could be an antisperm vaccine, but that might be permanently effective

Question 51

What are the two surgical contraceptive methods

Answer 51

Vasectomy and Tubal Ligation, both of which are viewed as permanent. Vasectomy is cutting and tying ductus (vas) deferens. Tubal ligation is cutting and sealing oviducts to block passage of the egg. Done using a laparoscopy.

Question 52

What is another name for a stroke and what are the two categories of stroke? What are risk factors for stroke?

Answer 52

Cerebrovascular accident.
1. ischemic stroke, caused by blockage of a cerebral artery by a thrombus and usually the result of atherosclerosis
2. hemorrhagic stroke, caused by bleeding from a cerebral artery, often because of an aneurism.
Hypertension, atrial fibrillation, high blood cholesterol, and diabetes are risk factors for stroke.

Question 53

What are treatments for stroke? When do they need to be administered and why?

Answer 53

Ischemic stroke can be treated with anticoagulant and thrombolytic drugs, but these are most effective if delivered soon after the ischemic injury. This is because of excitotoxicity, a process whereby neurons die as a result of the ischemia-induced impairment in the removal of glutamate from the synaptic clefts. This results in excessive inflow of Ca2+through the NMDA receptors, causing neuron death.

Question 54

How do artificial pacemakers work?

Answer 54

An artificial pacemaker is implanted under the skin below the clavicle. This is a battery-powered device with electrodes that are threaded into the heart through a vein using fluoroscopy for guidance, and used to correct such arrhythmias as a blockage in conduction of the impulse in the AV node or bundle of His. Some stimulate just one chamber, and some stimulate both an atrium and a ventricle by delivering a low-voltage shock causing depolarization and contraction. Most sense if a heartbeat is delayed and stimulate the heart on demand to maintain a good cardiac rate, and some can even sense if a person is exercising and adjust the cardiac rate accordingly.

Question 55

What is lymphedema and what causes it? Two main mechanisms of causing lymphedema

Answer 55

Lymphedema is a swelling of an arm or leg caused by excessive amounts of fluid and protein in the interstitial fluid. This results from blockage or destruction of the lymphatic drainage, usually because of surgery or radiation treatments for breast and other cancers. Lymphedema can also occur in the tropical equatorial regions because of infection with a species of nematode worm, which can block lymphatic vessels and cause enormous swelling of a leg or scrotum in the disease Elephantiasis

Question 56

What is a tropical disease born from bloodsucking insects? What do they transmit and how does it affect the body?

Answer 56

Filariasis is a tropical disease in which bloodsucking insects such as mosquitos spread a parasitic nematode worm. In elephantiasis, species of these worms take up residence in the lymphatic system, where their larvae block the lymphatic drainage. The edema that results can greatly swell tissues and produce a thickening and cracking of the skin. This disease is found in about 72 tropical countries, where over a billion people live and are threatened by infection. However, there is effective drug therapy available against the filariasis parasite, and the disease may be eradicated in the next several years.

Question 57

Why is hydration important during exercise? When/why might sports drinks be helpful?

Answer 57

Sweating can cause the loss of a substantial amount of water (up to 900 mL per hour). Lowered blood volume can lower the cardiac output and blood flow. This reduces the ability of the body to dissipate heat and limits the extent of the exercise. Drinking appropriate amounts of water helps if the exercise is not too long and strenuous. If it is, then electrolytes (Na+, K+, and Cl−) that are also lost in sweat must be replenished. When that happens, drinking water may quench thirst (because the water restores a normal plasma osmolality, satisfying the osmoreceptors) but not maintain the blood volume. Sports drinks containing electrolytes and a mixture of different sugars (to maintain blood glucose when glycogen stores are depleted) can improve physical performance when exercise lasts 60 minutes or longer.

Question 58

What are ACE inhibitors and ARBs used for and how do they work? How is this related to covid-19?

Answer 58

Angiotensin converting enzyme inhibitors (ACE inhibitors) are drugs that prevent the conversion of angiotensin I to angiotensin II, reducing vasoconstriction. This lowers total peripheral resistance and blood pressure. ACE inhibitors (captopril, enalapril, and lisinopril) help to treat hypertension, heart failure, stroke, and potential kidney failure, and aid the survival of people with myocardial infarctions. Angiotensin receptor blockers (ARBs) (telmisartan, losartan, and valsartan) inhibit the binding of angiotensin II to its receptors on vascular smooth muscles, reducing vasoconstriction. This promotes vasodilation and a lowering of the blood pressure.
Angiotensin II is destroyed by angiotensin converting enzyme 2 (ACE2). the spike protein on the SARS-CoV-2 virus (which causes Covid-19) gains entrance to body cells by binding to ACE2 on plasma membranes.

Question 59

Describe the standard method for assessing coronary artery disease.

Answer 59

An angiogram is an X-ray picture taken after a catheter is inserted into a brachial or femoral artery, threaded under guidance by a fluoroscope to the desired site at the coronary arteries, and iodine contrast (dye) is injected. Reveals atherosclerotic plaque, a thrombus, or a spasm.

Question 60

What is coronary angioplasty? What other device is also often implemented in this procedure? If those are still insufficient, what surgery may be performed?

Answer 60

Coronary angioplasty inserts a catheter with a balloon into the occluded site of a coronary artery and then inflates the balloon to push the artery open. However, restenosis (recurrence of narrowing) often occurs after this balloon angioplasty, and for that reason, a stent—a metallic mesh tube—is often inserted to support the opened section of the coronary artery. If required, a coronary artery bypass grafting (CABG) surgery may be performed involving the grafting of a vessel taken from the patient onto the aorta so that it bypasses the narrowed coronary artery

Question 61

How does regular aerobic exercise benefit the heart?

Answer 61

Reduces the resting cardiac rate and increases stroke volume. Because of the increased stroke volume, the resting cardiac rate can be lower while maintaining the same cardiac output. Training increases the vagus nerve parasympathetic inhibition of the SA node to slow the resting cardiac rate. Exercise training also increases blood volume, which thereby increases end-diastolic volume and stroke volume. Also makes the heart muscle more compliant and contract more forcefully. Result is improved oxygen delivery to the muscles and long term benefits to cardiovascular function

Question 62

Describe how the sympathetic system regulates blood flow. What are the two types of fibers involved?

Answer 62

Sympathoadrenal stimulation increases cardiac output, even when calm the system is active to some degree. Adrenergic sympathetic fibers release norepinephrine and activate alpha adrenergic receptors to cause a basal level of vasoconstriction. Their activity increases during fight-or-flight. Cholinergic sympathetic fibers release acetylcholine during fight-or-flight to cause vasodilation in skeletal muscles. Blood flow decreases to viscera and skin and increases to skeletal muscles, giving an extra edge to respond.

Question 63

Describe how the parasympathetic system controls blood flow

Answer 63

Always uses cholinergic signaling to promote vasodilation. Present in only digestive tract, external genitalia, and salivary glands, so not as important as sympathetic system

Question 64

What are the two types of auto regulation of blood flow and what organs use them most?

Answer 64

Myogenic = vascular smooth muscle dilates in response to decreased arterial pressure and constricts with high blood pressure. This protects the BRAIN from rupturing due to high blood pressure (cerebrovascular accident or CVA, stroke)

Metabolic = chemical environment causes vasodilation, such as decreased O2, increased CO2, decreased pH, release of K+ and paracrine regulators (adenosine, NO). KIDNEYs use this a lot (I think…)

Question 65

What is hyperemia? two types

Answer 65

Reactive hyperemia: when vasodilation is caused by a constriction that allows metabolic products to accumulate in an area. The metabolic products signal vasodilation after constriction ends and the area is thus warm and red

Active hyperemia: similar increase in blood flow due to increased metabolism (like during exercise). Helps to wash out vasodilator metabolites so blood flow falls to pre-exercise levels after exercise ends.

Question 66

What organ has the highest density of capillaries (why?) and what happens to blood flow as this organ contracts?

Answer 66

The heart has 2500-4000 capillaries per mm cubed (skeletal muscles have 300-400) so that every cell is within 10 µm of a capillary and fast gas exchange occurs. Contraction of myocardium squeezes coronary arteries and blood flow in the coronary vessels is less during systole than diastole. Myoglobin in the myocardium stores oxygen to be used during systole to provide continuous oxygen supply.

Question 67

What type of respiration is the heart specialized for and how?

Answer 67

Aerobic respiration. Myocardial cells contain myoglobin to provide continuous oxygen supply. They have a large amount of mitochondria and respiratory enzymes. Almost all ATP is produced by aerobic respiration and turnover is as fast as 10 seconds from break down to resynthesis! 50-70% of ATP is obtained from B-oxidation of fatty acids, the rest from glucose/lactate.
Normal hearts always respire aerobically, even during heavy exercise. The oxygen demand is met by increased coronary blood flow

Question 68

what mechanisms regulate coronary blood flow?

Answer 68

Sympathoadrenal stimulation of alpha adrenergic receptors (by norepinephrine) cause vasoconstriction at rest. Beta adrenergic receptors (by epinephrine) cause vasodilation during fight-or-flight.
Most important mechanism is intrinsic metabolic changes! Increased concentrations of CO2, K+, and paracrine regulators (NO, adenosine, prostaglandins) act directly on smooth muscle to cause vasodilation.

Question 69

Describe where blood is primarily flowing during exercise and what mechanisms divert blood flow to these areas

Answer 69

Blood flow increases in dynamically exercising skeletal muscles and the heart because of increased total blood flow (cardiac output), metabolic vasodilation in the exercising muscle, and diversion of blood away from viscera and skin due to vasoconstriction.
Brain blood flow is fairly constant from rest to exercise, though some motor areas may increase blood flow. Heavy exercise will eventually cause decreased cerebral blood flow because hyperventilation lowers blood CO2 and stimulates cerebral vasoconstriction, possibly contributing to central fatigue.

Question 70

How much does cardiac output increase during exercise? What factors affect how much cardiac output is increased?

Answer 70

Resting output is 5 L/min, exercise is 5L in 12 seconds, due to increased cardiac rate which is limited by a maximum value determined mainly by age. Athletes can increase stroke volume to improve cardiac output and deliver more oxygen (raise their VO2 max). Stroke volume increases because venous return is aided by skeletal muscle pump and respiratory pump during exercise. The EDV is unchanged, but stroke volume increases because the Ejection Fraction increases! Fraction changed by increased contractility and decreased peripheral resistance (from sympathoadrenal stimulation)

Question 71

Contrast cerebral and cutaneous blood flow

Answer 71

Cerebral: regulated by intrinsic mechanism, flow is relatively constant, brain cannot tolerate low rates of blood flow

Cutaneous: regulated by extrinsic mechanisms, flow is the most varied of any organ, skin can tolerate lowest rates of blood flow

Question 72

Describe regulation of cerebral circulation and why it is so important

Answer 72

Brain needs a very constant blood flow of 750 ml/minute, too low and you lose consciousness and two high can cause dangerous intracranial pressure. Sympathetic activity only occurs when pressure is very high (200 mmHg) to cause vasoconstriction. Normally regulation occurs by intrinsic mechanisms/ autoregulation both myogenic and metabolic

Question 73

Describe myogenic regulation of cerebral blood flow

Answer 73

automatic constriction/dilation occurs in response to rising/falling blood pressure. inadequate ventilation and subsequent CO2 rise, caused by decreased cerebrospinal fluid pH, also causes dilation while a fall in CO2 causes constriction. CO2 falls during hyperventilation and this is what causes dizziness!