Term 2 Midterm Material Flashcards

Question

Why do arteries have more smooth muscle than veins?

Answer 1

Arteries have more smooth muscle (and therefore more ability to constrict) than veins because arteries experience higher blood pressure than veins, so they need to be stronger, and they help produce pressure to push blood through the circuits. Also note that arteries in the periphery are effective at controlling blood flow by constriction of their thick tunica media smooth muscle layer (i.e., which organs receiving more or less blood). Veins don’t have enough smooth muscle to control blood flow in this manner.

Answer 2

False. The right side of the heart receives blood from the systemic circuit and pushes it into the pulmonary circuit. The left side of the heart receives blood from the pulmonary circuit and pushes it into the systemic circuit.

Answer 3

False. The left side of the heart receives blood from the pulmonary circuit and pushes it into the systemic circuit. The right side of the heart receives blood from the systemic circuit and pushes it into the pulmonary circuit.

Answer 4

* Both are striated, unlike smooth muscle. * Cardiac muscle is mononucleate (located near the centre of the cell); skeletal muscle is multinucleate (located on the periphery of the cell). * Cardiac muscle lacks the neuromuscular junctions that can be found in skeletal muscle, so cardiac muscle fibres to not need a motor neuron to stimulate them to contract, but skeletal muscle fibres do. * Cardiac myocytes are not innervated from somatic motor neurons. * Cardiac myocytes have reduced T-tubules and sarcoplasmic reticulum compared to skeletal muscle. * Cardiac myocytes form a functional syncytium, linked by intercalated discs (that physically link two cells at myofibril Z-lines), and gap junctions. * Intercalated discs with gap junctions mean that myocytes are (1) physically and (2) electrochemically linked and can act as a single large unit.

Answer 5

* There are two sets - atrioventricular and semilunar valves. * AV valves have associated structures (chordae tendineae and papillary muscles) * SL valves have a structure that means that increased pressure on the receiving side just closes them more tightly. * Heart valves open in response to pressure build-up, but only in one direction. They close when the pressure gradient reverses. This prevents backflow of blood. * Damage to these valves could result in backflow of blood and disrupt the heart's ability to pump blood throughout each circuit.

Answer 6

* Cardiac muscle cells lack neuromuscular junctions. * Instead, the heart coordinates the timing of atrial and ventricular contractions by a specialized internal conduction system formed from modified cardiac muscle tissue. * This system **transmits electrical depolarization** (In the form of action potentials) from the right atrium to the rest of the heart, with a brief delay. * Sometimes an irregular heartbeat, called an arrhythmia, is the first sign of a conduction disorder. If left untreated, severe conduction disorders can lead to **sudden cardiac arrest, in which the heart suddenly stops beating**.

Answer 7

Reducing blood flow through coronary vessels will reduce oxygen supply to the heart, reducing the heart’s ability to produce ATP to supply for its high metabolic demands. The person may experience angina: pain related to reduced blood flow through the heart. If a coronary blood vessel becomes completely blocked, preventing blood flow to part of the heart wall, a heart attack (i.e., myocardial ischemia) may result.

Answer 8

Damage to a heart valve would result in backflow through the valves. The heart will have to work a lot harder to accommodate this backflow. Semilunar valves are easier to successfully replace because there are no accessory structures to worry about as is the case with AV valves.

Answer 9

* APs of cardiac muscle are slower and last ~200x longer than myofibre APs (which never have a plateau phase). * The APs are prolonged because they involve the opening of L-Type voltage-gated calcium channels, which open slowly after depolarization, and remain open for long periods of time. * The plateau phase represents the open VG-calcium channels, and because some VG-potassium channels are open as well.

Answer 10

* Because of the duration of the AP, cardiac myocytes cannot produce tetanus. * A single AP generates a single contraction. * The very long AP outlasts the twitch (i.e. the single contraction), which prevents temporal summation (i.e., tetanus).

Answer 11

* The SA node membrane potential is never at rest - it constantly depolarizes, triggering an AP, then repolarizes, etc… * SA node is connected to the medulla oblongata via the vagus nerve which can adjust heart rate as necessary. * Gradual repolarization always occurs after depolarization in an SA node cell (= pacemaker cells). * Electrical activity can be broken into two parts: * (1) Action potentials → depolarization generated by T-type VG-calcium channels, instead of VG-sodium channels. * (2) Pacemaker potential → slow depolarization that automatically occurs. * VG-K channels are still involved in the repolarization phase of the SA node AP. * The ‘funny channel’ is opened by hyperpolarization. During the pacemaker potential, the ‘funny current’ flows across the cardiac myocyte plasma membrane, due to opening of the ‘funny channel'. * The ‘funny channel’ (HCN-channel) is a VG-cation channel that ONLY opens when the membrane is hyperpolarized. This channel allows sodium to enter the cell, leading to depolarization, brining the membrane back toward action potential threshold.

Answer 12

* SA node cells are electrically coupled to both the neighbouring cardiac myocytes and the next components in the conduction pathway. * The internodal pathways allow the depolarization to rapidly spread across both atria. * The second node in the pathway = AV node, slows the spread of SA depolarization through the system. * Due to reduced gap junctions between AV node cells (AV node can also act as a pacemaker, but its intrinsic rhythm is much slower than the SA node, so SA node determines heart rate. * Atrial contraction occurs during the 100ms delay at the AV node. * The geometry of the ventricular conduction pathways ensures that contraction first occurs far from the arteries, ensuring that blood is efficiently pushed into arteries and not trapped in the ventricle. (i.e., the parts of the ventricle closest to the atrium are the last to be depolarized since the impulse is directed down through the Purkinje fibres and then back up (= apex of the heart contracts first).

Answer 13

* The P wave relates to atrial wall depolarization * Note, you will never see an electrical signal of the atria repolarizing because it occurs while the much larger ventricles are depolarizing. * P-R interval → conduction through AV node and AV bundle. * QRS complex → ventricular walls depolarize * T wave → repolarization of the ventricle myocytes at the end of their APs.

Answer 14

The myocardium. It is principally composed of cardiac muscle cells (myocytes). Cardiomyocytes have a characteristic branched structure which join to others to form an interconnected branched network which provides structural strength to the beating heart.

Answer 15

Cardiac = A; Skeletal = B Both types have sarcomeres, myosin and actin fibres, and striations. Cardiac nuclei are in the centre of the cell and skeletal muscle nuclei are on the periphery of the cell. Cardiac muscle only has one nuclei and skeletal myofibers are multinucleate Skeletal muscle has more T-tubules and a more extensive sarcoplasmic reticulum than cardiac. Cardiac muscle has gap junctions and intercalated discs, and skeletal muscle does not. Cardiac muscle lacks neuromuscular junctions.

Answer 16

* Involves calcium-induced calcium release. * L-type VG-channels allow calcium ions to enter the cell (following their electrochemical gradient). * Increased intracellular calcium concentration causes the release of much, much, much more calcium from stores in the sarcoplasmic reticulum. * Depolarization of the sarcolemma opens VG-CC, allowing calcium to enter the cell. * Elevated calcium concentration triggers the opening of RyR, allowing calcium to escape the sarcoplasmic reticulum. * Elevated cytoplasmic calcium concentration triggers actin-myosin ATPase.

Answer 17

* In skeletal muscle → no ion flow through DHPR; mechanical coupling of DHPR and RyR * In cardiac muscle → calcium flows through DHPR into cytosol; biochemical coupling of DHPR and RyR. * Once calcium is present, the contraction cycle in a cardiac myocyte closely resembles what occurs in a skeletal muscle fibre.

Answer 18

One similarity = calcium binds troponin in the contraction cycle to expose the binding site for myosin. One difference = the DHPR/RyR interaction is mechanical coupling in skeletal muscle where calcium does not flow through DHPR; the DHPR/RyR interaction is biochemical coupling in cardiac muscle where calcium does flow through the DRPR into the cytosol.

Answer 19

* The main target of the ANS synapses in the heart are the two nodes in the conduction system, especially the SA node. * Parasympathetic slows the heart rate, sympathetic speeds. * An ANS synapse may cause ligand binding to the funny channel to increase permeability to sodium and allow more ion flow. The increased activation of funny channels results in more APs and a faster heart rate. * Norepinephrine (NE) released by sympathetic post ganglionic axons enhances the activation of funny channels, leading to more depolarization and a more rapid return to threshold. NE works through metabotropic receptors that lead to the production of cyclic-AMP (the cyclic nucleotide that enhances the function of the funny channels). The cAMP allows the channels to stay open for longer and contribute more to the more rapid depolarization. * Increasing the number of open VG-K channels will hyperpolarize the membrane and can create an IPSP to slow down the heart rate. * Acetylcholine leads to the opening of additional voltage-gated potassium channels, hyperpolarizing the cell and _prolonging the pacemaker potential phase_. During the repolarization phase, during parasympathetic stimulation, hyperpolarization will occur. This slows the heart rate because there will be slower depolarization via the funny channels and more time will be spend in the pacemaker phase.

Answer 20

* Sympathetic activation * An ANS synapse may cause ligand binding to the funny channel to increase permeability to sodium and allow more ion flow. The increased activation of funny channels results in more APs and a faster heart rate. * Norepinephrine (NE) released by sympathetic post ganglionic axons enhances the activation of funny channels, leading to more depolarization and a more rapid return to threshold. NE works through metabotropic receptors that lead to the production of cyclic-AMP (the cyclic nucleotide that enhances the function of the funny channels). The cAMP allows the channels to stay open for longer and contribute more to the more rapid depolarization.

Answer 21

* Parasympathetic division * Increasing the number of open VG-K channels will hyperpolarize the membrane and can create an IPSP to slow down the heart rate. * Acetylcholine leads to the opening of additional voltage-gated potassium channels, hyperpolarizing the cell and _prolonging the pacemaker potential phase_. During the repolarization phase, during parasympathetic stimulation, hyperpolarization will occur. This slows the heart rate because there will be slower depolarization via the funny channels and more time will be spend in the pacemaker phase.

Answer 22

Damaged SA node: A → abnormal P wave Damaged ventricular wall: B → abnormal, longer than usual T wave → current is not spreading normally through the ventricular wall

Answer 23

Cardiac output = the volume of blood (mL) moved through the heart per time (minutes). CO = mL/min = SV x HR

Answer 24

The number of times the heart goes through the entire cardiac cycle per minute.

Answer 25

The volume of blood (mL) ejected into the aorta (or pulmonary trunk) during each ventricular systole.

Answer 26

* Atrial systole completes the filling of the ventricles, which reach their EDV = ventricles achieve their maximum volume.

Answer 27

* A significant fraction of the EDV remains in the ventricle (= ESV) * SV = EDV - ESV

Answer 28

The volume of blood that is delivered to the right atrium during the cardiac cycle. VR is affected by CO and by constriction of vessels or compression of veins. Note CO may not always = VR due to the stretchy and compressible nature of veins (i.e., veins can store deoxygenated blood).

Answer 29

The duration of ventricular diastole, which determines the time the AV valves are open. Filling time is a function of heart rate. Increased HR = decreased filling time. Thus, HR also decreases EDV due to decreased filling time.

Answer 30

The amount of force produced during a contraction for a given preload. When contractility is enhanced (e.g., by sympathetic activity or by epinephrine), a higher SV is produced for the same EDV.

Answer 31

The amount of force the ventricle must generate to open its semilunar valve. Increased aortic pressure or pulmonary artery pressure = increased afterload. Afterload is directly affected by resistance (pressure) in blood vessels.

Answer 32

The amount of stretching of the heart wall due to blood within the ventricle. Increased EDV = increased stretch = increased tension (force) produced upon contraction = increased pressure generated due to optimized sarcomere length.

Answer 33

* Atrial systole completes the filling of the ventricles (= EDV). * Ventricular systole involves a period of isovolumetric contraction and a period of ventricular ejection.

Answer 34

* Skeletal muscles use more oxygen and nutrients, and generate more waste products and heat. Thermal homeostasis must be maintained by radiating heat away at the dermis. * These changes all require more blood flow. * During exercise, sympathetic activity increases, including increased epinephrine secretion from the adrenal medulla leading to increased heart rate, and increased CO. * As HR increases, length of diastole decreases, filling time decreases, EDV decreases, and ejection fraction and stroke volume will also decrease. * HOWEVER, during exercise sympathetic activity increases as does skeletal muscle contraction, which increases venous return and increases contractility, thereby increasing SV.

Answer 35

* During activity, sympathetic activity increases, as does skeletal muscle contraction, which leads to increased venous return, increased contractility, and increased SV (= increased CO). * Increased HR decreases filling time, decreasing EDV, ejection fraction, and SV (= decreased CO). * Prolonged training requiring increased oxygen use increases production of RBCs, and thus increases blood volume, therefore increases venous return and increases myocyte stretching, which triggers addition of sarcomeres (= eccentric hypertrophy).

Answer 36

* **Concentric** → seen in CVD and causes increased afterload and increased ventricular wall thickness (pressure overload) * **Eccentric** → associated with athletic training and pregnancy, and is related to increased venous return and increases in ventricular volume (volume overload) * Myocytes in the heart wall get their oxygen from coronary arteries. Concentric hypertrophy increases the oxygen requirement in the heart, but there are no coronary arteries to supply the new myocytes. So concentric hypertrophy is associated with insufficient oxygen supply to the heart. Eccentric hypertrophy does not have this problem with oxygen supply.

Answer 37

False. Decreased EDV = decreased stroke volume.

Answer 38

False. Increased end-diastolic volume increases stroke volume.

Answer 39

False. Increased EDV = decreased SV

Answer 40

False. Increased ESV = decreased SV

Answer 41

False. The greater the afterload, the lower the pumping efficiency of the heart, and the larger the ESV.

Answer 42

False. The greater the contractility, the smaller the end-systolic volume.

Answer 43

False. In general, when venous return increases, stroke volume increases. When venous return decreases, stroke volume decreases.

Answer 44

False. Increase in filling time increases the end diastolic volume.

Answer 45

False. Sympathetic stimulation increases heart rate and parasympathetic stimulation decreases heart rate.

Answer 46

It involves adjustments to heart rate in response to an increase in venous return. When the walls of the right atrium are stretched, stretch receptors there stimulate sympathetic activity to increase heart rate.

Answer 47

Muscular contractions compress veins and assist valves in directing venous blood toward the right atrium, increasing venous return.

Answer 48

Large reductions in blood volume due to bleeding or dehydration reduce venous return.

Answer 49

Changes in peripheral blood flow patterns can increase or decrease venous return.

Answer 50

False. Parasympathetic activation slows the heart rate but has little influence on contractility.

Answer 51

False. Many hormones increase contractility.

Answer 52

False. CO = SV x HR

Answer 53

True. CO = SV x HR

Answer 54

False. SV and HR are the same for each ventricle despite their structural differences. The left ventricle is more powerful than the right because it does more work to propel the blood throughout the systemic circuit. The pulmonary circuit does not necessitate such force, so the smaller right ventricle is adequate.

Answer 55

False. ## Footnote SV and HR are the same for each ventricle despite their structural differences. The left ventricle is more powerful than the right because it does more work to propel the blood throughout the systemic circuit. The pulmonary circuit does not necessitate such force, so the smaller right ventricle is adequate.

Answer 56

CO = SV x HR = 5250mL/min

Answer 57

The % of EDV that is released during ejection phase. SV/EDV x 100%

Answer 58

EDV decreases ESV decreases SV decreases

Answer 59

SV decreases ESV increases

Answer 60

SV decreases ESV increases

Answer 61

False. If there was a major blood loss (e.g., due to haemorrhage), preload would decrease.

Answer 62

False. If there was major blood loss afterload would decrease.

Answer 63

**Increasing stroke volume is more energy efficient than increasing heartbeat.**

Answer 64

**The Frank-Starling law describes how increased filling of the ventricles produces increases in stroke volume, due to stretching the ventricular myocardium.**

Answer 65

The atria are contracting (= atrial systole); the ventricles are still relaxed; the AV valves are open. Notice the rise and fall of pressure in the left atria and ventricle as pressure in the aorta continues to drop.

Answer 66

The atria relax; the ventricles contract; the AV valves shut; the SL valves will open. The AV valve shuts when the pressure is higher in the ventricle than the atria. Notice the aortic valve only opens when ventricular pressure exceeds that in the aorta. As such, there is a short period of time when the pressure is rising in the ventricle (i.e., both valves are shut), and there is no change in ventricular volume. Ventricular ejection is the top of the bell curve of ventricular pressure when blood is pumped into the aorta from the left ventricle.

Answer 67

Atria are still relaxed; the ventricles start to relax; the SL valves shut again.

Answer 68

Venous return and filling time.

Answer 69

Afterload and contractility

Answer 70

False. CO increases greatly during exercise, due to increases in both heart rate and stroke volume. Prolonged aerobic training tends to lead to **increases** in stroke volume and **decreases** in heart rate.

Answer 71

* A pressure gradient will produce a force that moves fluid in the direction of lower pressure. * A larger pressure gradient creates more force. * The velocity (i.e., flow rate) is slowed by resistance (caused by friction between the walls of the tube and the fluid, as well as viscosity).

Answer 72

* **Length** → the longer the vessel, the more surface that is in contact with the blood, thus the more friction blood will encounter (more length = more resistance) * **Viscosity** → a measure of resistance due to interactions among molecules in a moving fluid; blood is ~5x more viscous than water. * **Diameter** → in a small diameter vessel, proportionally more of the blood inside will be in contact or near the wall of the vessel, which is the source of most friction (smaller diameter = larger resistance) * **Turbulence** → occurs due to shifts or changes in the geometry of the vessel walls (i.e., branches, tight curves, irregular surfaces); turbulence increases resistance

Answer 73

* The farther the vessels are from the ventricle (the source of the pressure gradient), the lower the average pressure within them. * Arterial pressure is highest during and just after ventricular systole, and lowest during diastole.

Answer 74

* Cuff pressure blocks blood flow. * Pulse pressure = difference between systolic and diastolic pressure.

Answer 75

_120-130 mm/Hg_ 70-80 mm/Hg Systolic/diastolic

Answer 76

* Gravity either opposes or enhances blood flow, according to the location of the vessels relative to the heart. * Veins contain valves to help prevent backflow → mostly not present in the head; less common in the torso, common in limbs. * Skeletal muscle contractions work with venous valves to provide a secondary pump that helps propel blood toward the trunk, countering the force of gravity.

Answer 77

True. This is because the resistance associated with diameter is proportional to the radius⁴ (it relates to the volume inside the cylinder).

Answer 78

False. A change in diameter of a vessel wall will always produce a **larger** change in resistance than an equivalent change in length. This is because the resistance associated with diameter is proportional to the radius⁴ (it relates to the volume inside the cylinder).

Answer 79

Vessel diameter increases → less resistance to flow → increased blood flow

Answer 80

Vessel diameter decreases and introduces turbulent flow due to the irregular surface → increases resistance to flow rate → decreases blood flow

Answer 81

Enhanced pressure gradient → increased blood flow

Answer 82

Increases viscosity → increases internal resistance to flow → decreases blood flow

Answer 83

Increases vessel length → increases resistance to flow rate → decreases blood flow

Answer 84

* High diastolic pressure can lead to progressive heart failure because diastolic pressure is the main determinant of afterload, and increasing afterload means the heart muscle will have to work harder to reach the same level of cardiac output. In that case, there is extra demand on coronary arteries to supply the heart with a greater oxygen supply, but if they fail to meet the additional demand, then the heart muscle will become progressively weaker. * Isolated systolic hypertension is associated with elevated risk for ischemic incidents because increased pulse pressure exerts greater force on the blood vessels which increases the risk of plaque ruptures which may then lead to blood clots and heart attacks. * Low blood pressure is associated with risk of fainting because of the threat of low oxygen supply to the brain.

Answer 85

There’s no valves in the head veins because they are usually totally assisted by gravity. And there are also not a lot of postural muscles in the head and neck to provide an external pressure assistance. Blood isn’t necessarily rushing to the head as the arteries will be mostly unaffected. However, veins and sinuses will have a really hard time generating enough pressure to move the blood back up to the heart.

Answer 86

Deep vein thrombosis: when blood pools for too long in deep veins the clotting cycle may start even though there is no damage to the vessels → clot formation can lead to heart attacks.

Answer 87

Compression socks, low dose anticoagulants, elevation of lower limbs

Answer 88

False. Higher pressure gradients and lower resistance lead to increased blood flow.

Answer 89

Luminal diameter → resistance increases as diameter decreases Most resistance in the circuit comes from the many capillaries in it, which have the smallest lumen diameter.

Answer 90

False. Mean blood pressure decreases as blood moves through a circuit.

Answer 91

Increased luminal diameter.

Answer 92

Arterial pressure → fluctuates according to the cardiac cycle.

Answer 93

The capillary wall consists of a layer of endothelial cells and a basement layer. ## Footnote **Continuous →** complete endothelial layer with no obvious gaps; some fluid can flow between endothelial cells, and transport can occur across the endothelial membrane **Fenestrated →** pores allow for faster exchange of water and small solutes (including small peptides); found in many (neuro)endocrine organs (e.g., hypothalamus, pituitary, thyroid), and in areas involved in absorption (intestine) or filtration (kidneys); fenestrated capillaries can be found in the median eminence, for example, and in the parts of the hypothalamus that are responsible for sensing the osmolarity of blood plasma. **Sinusoidal →** have a discontinuous basement membrane; even very large proteins (e.g., plasma proteins) can freely exchange into tissue fluid; found in some endocrine organs (e.g., adrenals) and in liver, bone marrow, and spleen, which produce or recycle large plasma proteins and blood cells.

Answer 94

* Capillaries form networks known as beds. * Precapillary sphincters produce pulses of contraction and dilation, causing blood flow to be pulsatile in each capillary * Arteriovenous anastomoses can dilate, diverting blood away from the higher resistance capillary bed. * Contraction of smooth muscle in arterioles can reduce blood supply to the entire capillary bed

Answer 95

Diffusion refers to the passive movement of substances due to concentration differences. It is always passive (does not require ATP) and it can be either free or facilitated (i.e., involving carrier proteins or channels).

Answer 96

Osmosis is the diffusion of water molecules across a selectively permeable membrane. Osmotic pressure → the force that is pushing water to flow by osmosis → can be measured by the force it takes to stop the flow

Answer 97

Filtration refers to the movement of fluid through small pores in response to pressure differences. Hydrostatic pressure → refers to the force exerted on the vessel wall by the fluid inside it.

Answer 98

**Capillary hydrostatic pressure, CHP** → the pressure of the blood contents inside the capillary on the capillary walls. **Blood colloid osmotic pressure, BCOP** → the pressure driving water from ISF due to the large, suspended molecules (especially proteins) in plasma that are unable to cross the capillary wall. **Net filtration pressure, NFP** → the pressure gradient available to produce filtration. **NFP = CHP - BCOP**

Answer 99

* BCOP is a constant value, and related to the concentration of colloidal particles in plasma. * CHP is initially (relatively) high in the proximal part of the capillary, as blood enters from the arteriole. * CHP \> BCOP = **+NFP** * Meaning a pressure gradient that *_favours fluid movement into the ISF._* * By the middle of the capillary bed, forces are balanced, and there will be no pressure gradient to drive filtration. * CHP = BCOP = 0NFP * *_No net movement in either direction_* * Near a venule, there is negative NFP, favouring reabsorption * CHP \< BCOP = **-NFP** * Meaning a pressure gradient that favours fluid movement from interstitial fluid to plasma.

Answer 100

* **Metabolic acids** are produced during breakdown or synthesis of nutrients (e.g., lactic acid, pyruvic acid, and ketone bodies) * **Volatile acids** (e.g., carbonic acid) are formed when certain gases like carbon dioxide dissolve in water. * Inside RBCs, protons can bind hemoglobin, buffering the pH and enhancing gas transport and exchange. * Plasma proteins are also able to buffer some protons in ECF because several R groups on amino acids can act as weak acids. * Blood and other body fluids contain a large reserve of bicarbonate which can bind and buffer protons generated from metabolism. * Carbonic acid is a volatile acid and can be broken down in RBCs by **carbonic anhydrase** to carbon dioxide and water, which can be easily eliminated by the lungs.

Answer 101

False. Sinusoid capillaries allow for the most exchange; continuous allows the least.

Answer 102

False. Fenestrated capillaries are only found in parts of the brain lacking a blood brain barrier. For example, the median eminence, and in the parts of the hypothalamus that are responsible for sensing the osmolarity of blood plasma.

Answer 103

True. These tend to be lower resistance pathways than capillary beds due to fewer branching points and slightly wide diameters, which facilitates velocity of blood flow.

Answer 104

False. Arteriovenous anastomoses have a smooth muscle layer and is not a capillary, so does not allow exchange. Thoroughfare channels are capillaries and do allow exchange of substances.

Answer 105

Decreases CHP → decreases NFP

Answer 106

Increase BCOP → decreases NFP

Answer 107

Decreases BCOP → increases NFP

Answer 108

Increase CHP → increases NFP

Answer 109

Increases CHP → increases NFP

Answer 110

Decrease in plasma proteins Increase in blood volume Decrease in venous return

Answer 111

Decrease in blood volume Increase in plasma osmolarity (dehydration)

Answer 112

* Capillary hypoperfusion leads to acidosis (and specifically, acidosis from build-up of metabolic acids) because of anaerobic metabolism using ATP at a fast rate and generating wastes. * If there isn’t enough blood flow through the capillaries to allow enough oxygen per unit time to facilitate mitochondrial ATP production (i.e., aerobic metabolism), then the cells will switch to anaerobic metabolism, which generates significant lactic acid waste.

Answer 113

* Vasoconstriction and vasodilation refer to the amount of tension produced in the smooth muscle of the tunica media. * Smooth muscle shortens and produces tension in response to calcium elevation but has different contractile mechanisms than striated muscle. * Contraction reduces blood flow. * Dilation enhances blood flow.

Answer 114

* Intrinsic regulation → autoregulation of blood vessel diameter by factors occurring within the local environment of the blood vessel. * **Direct stimuli** known to cause vasodilation in peripheral tissues (i.e., increases blood flow and thereby oxygen delivery and waste removal): * Decreased oxygen concentration * Increased carbon dioxide concentration * Increased proton concentration * Increased potassium concentration * **Indirect** stimuli that can cause vasodilation * Paracrine factors → remain in their local environment (e.g., nitric oxide (NO) is a soluble gas that drives smooth muscle relaxation) * **Metabolic** → paracrine vasoconstriction factors which are constantly secreted at basal levels, helping to maintain baseline vessel tone. * **Myogenic** → stretching vascular smooth muscle triggers increased contraction, returning vessel diameter to original length.

Answer 115

* Extrinsic regulation → mechanisms involving the organ system that integrate signals throughout the body (i.e., nervous and endocrine systems).

Answer 116

* Sympathetic activity is higher when the body is cold and lower when the body is warm. * Blood flow through blood vessels in skin is precisely regulated by the CNS to maintain homeostasis → constricts vessels when core temperature is low, dilates when high. * Although skin is not metabolically active during exercise, blood flow increases to skin driven by the CNS have a critical role to lose heat generated by skeletal muscle. * **Extrinsic regulation \> intrinsic regulation**

Answer 117

* Intrinsic regulation \> extrinsic regulation within skeletal muscles during exercise hyperaemia. * Although sympathetic activity increases during exercise, promoting vasoconstriction (alpha-1 receptors), this effect is much smaller than the vasodilation that occurs due to metabolic factors (e.g., decreased oxygen concentration, increased carbon dioxide and metabolic waste concentration). * Adenosine → a paracrine factor released when ATP is used → a key driver of vasodilation in coronary arterioles.

Answer 118

Dilation of arterioles in skeletal muscle and skin increases blood flow in those tissues; however, vasoconstriction in vessels of other areas like the GI tract will restrict blood flow there to direct more blood to the skin/skeletal muscle/heart. Blood flows according to paths of least resistance. Since resistance is increased in vessels that are vasoconstricted, the blood will preferentially flow to areas of lesser resistance instead.

Answer 119

False. It is a homeostatic response.

Answer 120

False. This is an example of extrinsic regulation.

Answer 121

False. This would lead to vasodilation.

Answer 122

False. This is an example of homeostasis.

Answer 123

* Alpha-1 receptors → elevate intracellular calcium, enhancing smooth muscle contraction (i.e., vasoconstriction) * Most sensitive to NE. * Beta receptors → elevate intracellular cAMP, reducing smooth muscle contraction (i.e., vasodilation) * Most sensitive to E * Note: β receptor activation has the opposite effect on contraction in cardiac muscle because of the different contraction pathways in smooth and striated muscle. β receptor activation in cardiac muscle enhances contraction, and in smooth muscle β receptor activation inhibits contraction.

Answer 124

False. β receptor activation in cardiac muscle enhances contraction, and in smooth muscle β receptor activation inhibits contraction.

Answer 125

False. Beta-receptors are most sensitive to epinephrine (E)

Answer 126

False. Alpha-1 receptors are most sensitive to norepinephrine.

Answer 127

* Sympathetic postganglionic axons of the ANS make synapses on vascular smooth muscle → vasomotor fibres * Action potentials in vasomotor fibres lead to enhanced contraction in smooth muscle (= increased ‘vasomotor tone’) * The parasympathetic division does not synapse on blood vessels.

Answer 128

* Erectile tissue in the reproductive system is one exception where there is parasympathetic innervation of vascular tissue. * Parasympathetic postganglionic neurons that innervate erectile tissue release NO (instead of or in addition to ACh) * NO leads to vasodilation. * Viagra enhances the NO-mediated signalling pathway to maintain vasodilation.

Answer 129

Adenosine causes vasodilation in coronary arterioles which increases blood flow to the heart.

Answer 130

Sympathetic nervous system vasodilates superficial vessels of skin in extremities when temperature is high to radiate heat for thermal homeostasis.

Answer 131

ED drugs cause blood vessels to dilate. Taking multiple drugs that cause vasodilation and lower blood pressure could lead to dangerously low blood pressure. If already hypotensive, taking ED to vasodilate blood vessels could lead to dangerous hypotension as well. If you have low blood pressure, the heart will have a hard time pumping blood all the way up to the brain.

Answer 132

Sex is a form of exercise for most people that causes increases in cardiac output. This increases strain on the cardiovascular system. There is a very strong link between erectile dysfunction and heart disease, so increasing strain on the cardiovascular system could be dangerous.

Answer 133

* Altering vasomotor tone requires constant neural (and cardiac) activity - energy intensive * Adjustments to blood volume are slow, but they can maintain blood pressure through the circulatory system without constant energy input.

Answer 134

* **Sensors** → neurons in large elastic arteries * **Integrators** → neurons in the hindbrain * **Effectors** → organs of the CV system * **Regulated variables** → mean arterial blood pressure (baro); blood pH, P_O2, and P_CO2 (chemo)

Answer 135

**Chemoreceptor (increasing CO2, decreasing pH)** → The cardioaccelerator and vasomotor centres will be stimulated, cardioinhibitory centre will be inhibited → increased cardiac output and vasoconstriction (i.e., blood pressure). Vasoconstriction helps with venous return to get more blood to the heart to help increase cardiac output, and to increase capillary hydrostatic pressure to increase the amount of filtration that’s happening in every capillary bed. **Baroreceptor (increasing mean arterial pressure)** → When blood pressure is high the cardioinhibitory centre will be stimulated, cardioacceleratory centre and vasomotor centres will be inhibited → decreased CO and vasodilation. Vasodilation helps increase blood flow and reduce blood pressure. When blood pressure is low, just the opposite occurs.

Answer 136

Low blood pressure (or blood volume) leads to lower levels of perfusion through kidney tissue, stimulating the release of EPO and renin. **EPO** → drives RBC production, increases blood volume **Renin** → part of the hormonal axis known as the RAAS - it catalyzes the first step in the production of angiotensin II and leads to increased plasma volume. **Angiotensin II** → has short-term effects on blood pressure → produces vasoconstriction in most blood vessels → it also acts as a regulatory hormone, enhancing the release of aldosterone, and anti-diuretic hormone (ADH). **Aldosterone** → a mineralcorticoid (synthesized in the adrenal cortex) hormone that primarily acts on the kidney to retain sodium cations which contributes to water retention. **ADH** → secreted from the posterior lobe of the pituitary gland → stimulates water retention by the kidney and acts inside the brain to produce thirst

Answer 137

Long-term hormonal responses are more energy efficient but slower. Short-term neuronal responses are energy intensive but are much faster. * Short term responses to blood loss involve neural reflexes and the physiological stress response. * Medium term → reductions in blood pressure leads to reductions in CHP, which lead to ‘recall of fluid’ from the ISF. * Long term → increases in ADH and aldosterone leads to increased fluid intake and fluid retention, while EPO restores RBCs.

Answer 138

* Occurs after major blood loss (\>20% volume lost) * Rapid, weak pulse, cold, pale, thirsty, sweating * The transition to irreversible shock is triggered by baroreceptor and chemoreceptor reflexes that attempt to maintain blood flow to the brain at the expense of all the other organs → leads to a fatal positive feedback loop.

Answer 139

False. Inhibiting baroreceptors leads to increased CO and increased HR.

Answer 140

* When blood pressure is disturbed, blood pressure is restored to the set point (i.e., homeostasis). * When blood chemistry is disturbed, blood pressure is moved to a new set point (i.e., allostasis).

Answer 141

All blood must be filtered by the kidneys. This is an indirect feedback loop. In a direct feedback loop everything is detected in a single step, but in this loop multiple stages and multiple effectors are involved.

Answer 142

High blood pressure (or blood volume) leads to increasing stretching in heart chamber walls, which leads to the release of natriuretic peptides (ANP, and BNP). * ANP → released by the atria * BNP → released by the ventricles * These peptides are regulatory hormones that inhibit the release of renin (and therefore aldosterone), ADH, and epinephrine. * These peptides also stimulate the kidneys to increase excretion of sodium cations, which also leads to water loss. * They also produce vasodilation in most blood vessels.

Answer 143

The heart is a good sensor because the atria sense high blood volume with stretching. The heart uses pressures to move blood and can detect it. Long-term hormonal responses are more energy efficient but slower. Short-term neuronal responses are energy intensive but are much faster.

Answer 144

* Skin is pale because venous return is diverted to deep veins. * The patient is cold because there is reduced blood flow to the integument. * Sweating is because of sympathetic nervous system activation. * Thirst is because of more ADH being produced. * The pulse is weak because of low blood volume. * The pulse is rapid because the heart is pumping rapidly to attempt to ensure the body still has a blood supply. * Alcohol is a vasodilator and can rapidly decrease blood pressure.

Answer 145

External respiration = exchange of oxygen and carbon dioxide between blood, lung tissue, and the external environment = primary function of the respiratory system. Secondary functions: * **Sensory** → neurons in the nasal cavity detect smells * **Barrier** → keeps foreign substances in air from entering the body * **Communication** → airflow may be manipulated for speech/song.

Answer 146

* Upper parts → responsible for conditioning inhaled air, and reabsorbing heat and water from exhaled air. * Lower parts → conduct air to gas exchange surfaces (and perform gas exchange. * Conducting portions are a series of flexible, branching tubes: * Larynx * Trachea * Bronchi (3 types) * Bronchioles (2 types) * 1 tracheaa → 2 primary bronchia → 5 lobar bronchia → 10s of 1000s of terminal bronchioles → ~150,000,000 alveoli per lung * Respiratory portions are the pulmonary lobules → respiratory bronchioles and alveolar sacs which contain capillary-wrapped alveoli (gas-exchange structures).

Answer 147

* During quiet breathing, the diaphragm and external intercostals contract and expand the thoracic cavity, then relax. * Movements of inspiratory muscles during inhalation expand the lungs, creating a negative pressure gradient that pulls air through the airways to the lungs. When the muscles stop contracting, they resume the original position, and the pressure gradient reverses.

Answer 148

* Somatic motor neurons located in the cervical and thoracic spinal cord innervate inspiratory skeletal muscles to produce breathing movements that are rhythmic. * Phrenic motor neurons send their axons in the phrenic nerve and innervate the myofibres of the diaphragm → no phrenic motor neuron activity = no breathing! * Respiratory centres in the pons integrate information from the forebrain and sensory neurons and can adjust the ongoing rhythm generated by the respiratory centres in the medulla (which synapse onto motor neurons that drive breathing muscles) → no medullary respiratory centre activity = no breathing!

Answer 149

A single quiet breath moves ~500mL into and then back out of the lungs (the resting tidal volume).

Answer 150

Vital capacity → Expiratory reserve volume + tidal volume + inspiratory reserve volume

Answer 151

Some air remains in the lungs even after maximal exhalation = residual volume.

Answer 152

False. Only the upper respiratory tract shares parts with the digestive system.

Answer 153

False. External respiration will fail (i.e., the diaphragm is a skeletal muscle)

Answer 154

Mucous protection in the upper respiratory tract is more effective than macrophages in the lower respiratory tract. The lower respiratory tract is where the lungs and alveoli are – infections there will directly affect gas exchange.

Answer 155

Pressure needs to be lower in the pulmonary circuit to prevent damage to the single epithelial layer between air/blood. The capillaries should neither rupture, nor force fluid out to make gas exchange and external respiration as efficient as possible.

Answer 156

The force of surface tension after exhalation will cause alveoli to collapse, leading to decreased surface area for gas exchange. This leads to difficulty breathing.

Answer 157

Similarities: They’re both pumps that create a pressure gradient. Differences: The heart doesn’t require CNS intervention but breathing does. Pericardium (heart cavity) vs. pleura (lung cavity). Cardiac muscle (cardiac) vs. skeletal muscle (respiratory).

Answer 158

His high lung capacity increases the alveolar surface area which makes gas exchange more efficient for him. He can extract more oxygen per breath than the average male. In the same way, his total lung capacity increases the amount of THC (from weed) that he can exchange in one breath, so he may get high faster than the average male.

Answer 159

* Respiratory minute volume (V_E) measures the amount of air moved into the respiratory system per minute. * V_E = respiratory rate (f) x tidal volume (V_T) * Alveolar ventilation (V_A) is a measure of the amount of air that reaches the alveoli per minute. * V_A = breaths per minute (f) x (Tidal volume - anatomical dead space) * These measurements differ due to the anatomical dead space → some inhaled air never reaches the alveoli.

Answer 160

* **(1) Protective reflexes** → cause forceful exhalation against partial constriction of the airways, which create high pressures to clear the airway. * **Sneeze** → triggered by presence of irritants in nasal cavity * **Cough** → triggered by irritants in the lower respiratory tract * **(2) Inflation (and deflation) reflexes** are activated by baroreceptors in the lungs. * Regulate breathing rhythm to avoid over or under inflation. * **(3) Chemoreceptor reflexes** are activated from sensors in elastic arteries and the medulla oblongata. * Sensitive to changes in P_CO2 → elevations in metabolic activity increase respiratory rate

Answer 161

* **Resistance** → a measure of how much force is needed to make air flow rapidly through conducting pathways. * **Compliance** → a measure of how much work it takes to expand the lungs at a given pressure * More force required for expansion = LOWER compliance * Less force required for expansion = HIGHER compliance * Relates to (1) properties of lung tissue or (2) properties of skeletomuscular elements.

Answer 162

* **Restrictive → lower capacity for air across most measures of lung function** * Respiratory distress syndrome → reduced/absent surfactant * Arthritis in rib articulations * **Obstructive → increased residual capacities** * Asthma → inflammation and bronchoconstriction * Chronic bronchitis → inflammation leading to overproduction of mucous that clogs airways

Answer 163

* Caused by destruction of respiratory tissue → loss of alveolar structure and gas exchange surfaces → result of prolonged exposure to toxic particulates * Alveoli walls deteriorate, leading to merging of adjacent alveoli → walls may even tear * Associated with increased compliance → less tissue in alveolar wall → lungs are easier to inflate * Lack of elastic recoil in lung tissue means exhalation is comparatively harder → accessory muscles are used even in quiet breathing. * Respiratory rate increases due to reduction in gas exchange surfaces (equivalent to increased anatomical dead space) * Carbon dioxide cannot be adequately removed * Chemoreceptor and baroreceptor reflexes increase respiration rate to attempt to maintain blood oxygenation and try to correct the high P_CO2.

Answer 164

* Deflation * Stretch receptors in smooth muscle around bronchioles → stimulated by lung expansion * Respiratory muscles are inhibited by the respiratory rhythmicity centres → inhalation stops * Expiratory centres stimulated → forced exhalation * Inflation * Stretch receptors in the alveolar walls are stimulated as elastic fibres recoil and the alveolar volume is reduced * Expiratory centres are inhibited → exhalation stops * Forced inhalation begins by stimulation of inspiratory centres in the pons * These baroreceptors send information to respiratory centres in the pons, which regulates breathing rhythm to prevent over or under inflation.

Answer 165

* Chemoreceptors in the respiratory centres in the medulla oblongata respond to concentration of hydrogen ions (pH) and carbon dioxide in cerebrospinal fluid * Trigger reflexive adjustments in the depth and rate of respiration * Chemoreceptors of carotid bodies are sensitive to changes in pH, P_CO2 and P_O2 in arterial blood * By cranial nerve IX * Trigger reflexive adjustments in respiratory and cardiovascular activity * Chemoreceptors of aortic bodies are sensitive to changes in pH, P_CO2, and P_O2 in arterial blood * By cranial nerve X * Trigger reflexive adjustments in respiratory and cardiovascular activity * These chemoreceptors are more sensitive to changes in P_CO2than changes in P_O2.

Answer 166

False. They both require changes in CNS activity.

Answer 167

True. Baroreceptors are also found in the digestive system.

Answer 168

False. Increased stretching of bronchiole walls promotes exhalation and inhibits further inhalation.

Answer 169

False. Elevations in metabolic activity leads to an increase in breathing frequency.

Answer 170

* **Restrictive lung disease** → reduced compliance → patient unable to fully fill their lungs → characterized by lower capacity for air across most measures of lung function → easier to detect and diagnose through forced vital capacity because resting tidal volume is small * A patient does more work to get the same total volume of air, examples: * Respiratory distress syndrome → absence of surfactant * Arthritis in rib articulations * **Obstructive lung disease** → increased resistance → lung volume is normal, but conducting pathways are obstructed → characterized by increased residual capacities → reduction is seen during the first second of a forced expiration → typically measured from the ratio of FEV₁/FVC. * Getting air into the lungs will take more time because resistance affects flow rate, or it will require a much stronger initial pressure gradient to compensate, examples: * Asthma → caused by inflammation and bronchoconstriction in airways. * Chronic bronchitis → caused by inflammation leading to overproduction of mucous that clogs airways

Answer 171

False. Obstructive lung disease is associated with increased resistance.

Answer 172

False. Restrictive lung disease is associated with reduced compliance.

Answer 173

False. Obstructive lung disease is characterized by increased residual capacities.

Answer 174

False. Restrictive lung disease is characterized by lower capacity for air across most measures of lung function.

Answer 175

* FEV₁ is a great measure of resistance. * FVC is variable from person to person. * In obstructive lung disease, FEV₁ is reduced due to an obstruction of air escaping from the lungs, so the ratio will be reduced. * In restrictive lung disease, FEV₁ and FVC are equally reduced, so the ratio will be approximately normal.

Answer 176

Emphysema is not associated with reduced compliance like restrictive lung disease is, it is associated with increased compliance. Thus, it is more likely to look like obstructive lung disease (which has increased resistance).

Answer 177

Morphine helps with anxiety by relieving shortness-of- breath. Opioids makes you breathe more slowly and less deeply, helping the patient to feel calmer.

Answer 178

* Partial pressure → pressure exerted by a single gas within a mixture of gases (Dalton's law = pressure contributions for each individual gas can be considered independently according to their proportion in the mixture) * Oxygen content is lower in alveolar air compared to inhaled air

Answer 179

* Blood arriving at pulmonary capillaries is deoxygenated (low P_O2) and relatively high in P_CO2. * The thin wall created by alveolar type I cells and pulmonary capillary endothelial cells allows for oxygen to diffuse into blood, and CO₂ to diffuse into the alveolar cavity. * Blood arriving at systemic capillaries is oxygenated (high P_O2) and relatively low in P_CO2. * Oxygen can diffuse down its concentration gradient into tissue, while the pressure gradient favours the uptake of CO₂ into blood.

Answer 180

* Fick's Law → Diffusion of a particular gas at a given temperature is **enhanced** by (1) a large surface area and (2) a steep partial pressure gradient, and **reduced** by a thick barrier.

Answer 181

* The vast majority of O₂ in blood is transported bound to Hb in RBCs. * Hb binds O₂ cooperatively. * If one of its four subunits is bound to oxygen, the others become more likely to bind as well → keeps oxygen saturation high at rest, even in systemic venous blood.

Answer 182

* (1) Dissolved in solution, (2) bound to Hb, or (3) converted to carbonic acid and bicarbonate/H⁺ * CO₂ can reversibly bind Hb (especially when P_O2 is low) * Most will be converted to carbonic acid by carbonic anhydrase * H⁺ generated by carbonic acid dissociation can also bind Hb → buffering against changes in pH → favours O₂ offload (and thus CO₂ uptake) by Hb.

Answer 183

* At higher altitudes, the air is ‘thinner’ (**lower total atmospheric pressure**). Although the proportions of the gas molecules are the same, the partial pressures of each gas are lower. * The changes in P_CO2 are negligible, but because P_O2 is lower, alveolar oxygen levels are also lower, and the rate of diffusion of O₂ across the blood-air barrier will be slower (due to a reduced P_O2 gradient). * Altitude sickness leads to hyperventilation and alkalosis in the short term. * Hypoxia stimulates respiratory reflexes → increases minute ventilation (V_E) → loss of CO₂ from blood → alkalosis → O₂ offload is less efficient → HR (therefore CO) increases to maintain O₂ delivery → leads to higher demands * Long-term compensation is driven by endocrine signalling * Hypoxia triggers EPO release → increases RBC levels in blood → improves oxygen transport even at lower alveolar P_O2.

Answer 184

* The oxygen content lower in alveolar air compared to inhaled air because of air that is stuck in the anatomical dead space that mixes with the inhaled air. * The water vapour goes up because air is humidified by the structures of the upper respiratory system upon inhalation. * If you were stuck in a completely sealed room CO₂ would increase, O₂ would decrease, and water vapour in the room would increase. * If you were way up high in the mountains everything would be proportionally lower because the total pressure at high altitude is decreased.

Answer 185

* This fluid accumulation will affect external respiration because the inflammation increases the distance between the alveoli and capillaries (i.e., the thickness of the barrier increases), so there will be a lower rate of diffusion and less efficiency in gas exchange. * This decrease in gas exchange will result in less O₂ delivery to tissues. * Since the blood in the pulmonary circuit is not fully oxygenated, there will be a decreased P_O2 in the blood going out to the tissues, so there will be less of an oxygen gradient in other tissues, which will slow down the rate of diffusion in those tissues as well.

Answer 186

* During exercise, skeletal muscle metabolic rate increases, and oxygen is used for aerobic ATP production → decrease in P_O2 promotes offloading of oxygen by Hb, meaning substantial oxygen can be delivered even without an increase in blood flow. * **Bohr effect →** During exercise, skeletal muscles create more CO₂ and may create metabolic acids if metabolism becomes anaerobic → both factors lead to increased H⁺ and therefore decreased pH → decreased pH leads to ‘right-shift’ in the Hb saturation curve, favouring oxygen offload to tissues even at a higher P_O2 * When tissues increase in temperature (heat is a by-product of ATP production), Hb saturation curves shift, favouring oxygen offload → higher temperatures favour offload → again enhancing oxygen delivery to active tissues.

Answer 187

False. Increasing pH = more basic Increasing H⁺ → decreasing pH = more acidic

Answer 188

False. A right shift in a Hb saturation curve indicates **less** oxygen will be bound to Hb for a given partial pressure (compared to ‘normal’).

Answer 189

False. Venous blood oxygen saturation **decreases** during aerobic exercise.

Answer 190

False. More CO₂ leads to more carbonic acid production → decreased pH → right-shift of Hb saturation curve → favours oxygen offload

Answer 191

Semilunar valves are easier to successfully replace because there are no accessory structures to worry about as is the case with AV valves.

Answer 192

* The most important hormone to consider for local control of blood flow is epinephrine because smooth muscle in different tissues expresses different adrenergic receptor subtypes which can produce opposite effects since they couple to different G-proteins that lead to different biochemical changes when activated. * **α₁ receptors** → elevate intracellular calcium, enhancing smooth muscle contraction (i.e., vasoconstriction) * Most sensitive to norepinephrine (NE) * **β receptors →** elevate intracellular cAMP, reducing smooth muscle contraction (i.e., vasodilation) * Most sensitive to epinephrine (E) * β receptor activation has the opposite effect on contraction in cardiac muscle because of the different contraction pathways in smooth and striated muscle. * β receptor activation in cardiac muscle enhances contraction, and in smooth muscle β receptor activation inhibits contraction.