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BIOL 1412 > Topic 11: Cardiovascular Physiology > Flashcards

Topic 11: Cardiovascular Physiology Flashcards

1
Q

What parts make up the conduction system of the heart?

A
  1. Sinoatrial (SA) node
    - rate = 100 APs/min
    - modified by PSNS to 75 APs/min
    - the pacemaker
  2. Atrioventricular (AV) node
    - rate = 50 APs/min
  3. Bundle of his (AV bundle)
    - originates at AV node
    - ONLY route for electrical activity from A to V and Bundle Branches
    - 30 APs/min
  4. Purkinje fibres
    - terminal fibres ~> stimulate contraction of the ventricular myocardium
    - 30 APs/min
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2
Q

What are non-contractile cardiac muscle cells?

A

They are cell modified to initiate & distribute impulses throughout the heart. They produce APs spontaneously (without stimulus), but at different rates

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3
Q

Describe the pathway of APs in the heart

A

SA node
\/
AV node
\/
Bundle of his
\/
Bundle Branches
\/
Purkinje fibres
\/
Ventricular contractile myocardium

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4
Q

What would happen if the conduction system of the heart is damaged?

A

The next fastest AP becomes the new pacemaker (ie. if the SA node gets damaged, the AV node takes over)

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5
Q

What are the phases of pacemaker activity?

A
  1. Pacemaker potential
    - low K+ permeability
    - slow inward leak of Na+ ~> slow depolarization to threshold (-40mV)
  2. AP depolarization
    - Ca++ voltage gates open
    - Ca++ voltage gates close at peak
  3. AP repolarization
    - at peak, K+ OUT (gates open)
    - K+ voltage gates close below threshold
  4. Na+ channels open at -50mV
    - starts potential again
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6
Q

What is the role of Na+ in AP depolarization of the pacemaker?

A

Na+ voltage gates close at the threshold, so they are NOT involved in the AP

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7
Q

What is the threshold for SA & AV node action potential?

A

-40mV

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8
Q

What is the resting membrane potential of the pacemaker?

A

There is NO resting membrane potential

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9
Q

What are the phases of ventricular myocardial APs?

A
  1. Depolarization
    • Na+ voltage gates open
    • MP to +30mV
  2. Plateau
    • Na+ channels close
    • Ca++ slow voltage gates open
  3. Repolarization
    • Ca++ channels close
    • K+ voltage gates open
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10
Q

What causes blood flow through the heart?

A

Emptying pressure changes

Valves

Myocardial contraction

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11
Q

What do diastole and systole mean?

A

Diastole = relax
Systole = contract

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12
Q

What happens during ventricular systole?

A

Higher pressure in ventricles forces AV valves shut
Higher pressure pushes semilunar valves open, and blood enters vessels (1st sound)

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13
Q

What happens during ventricular diastole?

A

Pressure drops, higher pressure in aorta/pulmonary trunk forces semilunar valves shut (2nd sound)

AV valves open when pressure in ventricles drop

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14
Q

How does blood flow create heart sounds?

A

Turbulent flow: noisy due to blood turbulence when valves shut

Laminar flow: no sound

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15
Q

What are Korotkoff Sounds?

A

Turbulence heard in brachial artery during BP measurements:
• begin = systolic pressure
• stop = diastolic pressure
• due to cardiac cycle events

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16
Q

What is cardiac output and how is it calculated?

A

Volume or blood ejected by each ventricle in 1 min

CO = HR (bpm) x Stroke Volume (mL/beat)

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17
Q

What is stroke volume (SV)?

A

It is the volume of blood ejected by each ventricle per beat

  • equal to EDV — ESV
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18
Q

What is EDV and ESV?

A

End Diastolic Volume: volume of blood in each ventricle at the end of ventricular diastole (~120ml)

End Systolic Volume: volume of blood in each ventricle at the end of ventricular systole (~50ml)

SV = 120ml — 50ml = 70ml

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19
Q

What is the basic HR rate set by?

A

SA node (intrinsic control)

*all modifiers are extrinsic: these change the pacemaker potential

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20
Q

What are the types of neural extrinsic control of HR?

A

SNS (thoracic nerves): sympathetic signals cause Na++ channels to open wider, allowing membrane potential to reach threshold faster

PSNS (Vagus nerve): parasympathetic signals increase K+ permeability at the SA node, causing the potential to become more negative during repolarization

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21
Q

What are the hormonal extrinsic factors affecting HR?

A

Epinephrine, NE, thyroid hormone all cause increased HR

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22
Q

What are the 3 components of the cardiac cycle?

A
  1. Electrical activity (ECG)
    - small currents flow through salty body fluids
    - potential difference measured using electrode pairs (1 par = lead)
    - recorded as waves
  2. Mechanical activity
    - 2 main events: systole & diastole
  3. Blood flow through the heart
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23
Q

Describe ECG waves

A

> P wave: atrial depolarization ~> followed by contraction

> QRS wave: ventricular depolarization ~> contraction

> T wave: ventricular repolarization ~> followed by relaxation

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24
Q

What is Frank-Starling’s Law of the Heart?

A

Force of ejection is directly proportional to length of ventricular contractile fibres

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25
What can cause an elevated venous return?
Exercise ~> venous return speeds up Lower HR ~> has longer to fill
26
How can the endocrine system affect the extrinsic control of stroke volume?
Epinephrine and NE use the same mechanism as SNS: increased force/stroke volume Thyroid hormone increases force by increasing the amount or elimination receptors in cardiac muscle cells
27
What are some factors that can increase the force of stroke volume?
- raising external Ca++ (therefore more moves during AP) - digitalis (drug): increases Ca++ inside
28
What are some factors that can decrease the force of stroke volume?
- acidosis - ⬆️ external K+ - Ca++ channel blockers (drugs), eg. verapamil
29
What is the formula for blood flow?
Flow = ΔBP gradient/resistance
30
Define blood flow
Volume of blood flowing through any tissue/min (ie. ml/min)
31
What does resistance depend on?
1. Vessel length 2. Blood viscosity 3. Radius of arterioles, controlled by smooth muscle innervated by SNS - vasodilation: + radius (- resistance) - vasoconstriction: - radius (+ resistance)
32
What is resistance of blood flow?
Opposes flow: friction of blood rubbing against vessel walls
33
How does vasoconstriction affect blood flow to organs?
a) Decreases radius (+ resistance, - flow) b) pressure in artery increases c) pressure in organ decreases (less blood flow into organ capillaries) vaso*dialation* is the opposite
34
True or false: even local vasoconstriction/dilation (ie. to 1 organ), can change the systemic BP
False There is no observable change in systemic BP. In order for the systemic BP to change, the vasoconstriction/dilation must be systemic
35
What are the 2 types of intrinsic regulation (allows organ to control its own blood flow) of vasoconstriction/dilation?
1. Myogenic regulation - when smooth muscle is stretched, it contracts, increasing systemic BP 2. Metabolic regulation - changing blood chemicals affects metabolism
36
Extrinsic regulation of vasoconstriction/dilation control the nervous and endocrine systems. What are the 2 types of extrinsic regulation?
1. Neural regulation (SNS) 2. Endocrine (hormonal) - epinephrine - others
37
HR is one of the essential aspects of cardiac output (CO). What are the factors that can affect HR?
1. Neural • SNS (thoracic nerves) ~> *+HR*: ⬆️ Na+ permeability allows membrane potential of SA node to reach threshold faster • PSNS (Vagus nerve) ~> *-HR*: ⬆️ K+ permeability causes membrane potential of SA node to become more (-) in repolarization 2. Hormonal • E, NE: *+HR* ~> same as SNS • Thyroid hormone: *+HR* (slow) 3. Other • Ions ~> eg. Too high K+ (Hyperkalemia) affects Na+ channels in pacemaker, leading to ⬇️ HR, may lead to CA • Fever: *+HR* • Age: ⬇️ with age • Fitness: higher fitness, ⬇️ HR
38
In regards to cardiac output, what are the 3 main factors that influence stroke volume (SV)?
1. Venous return • higher return results in heart muscle stretch (using Frank-Starling) 2. SNS • ⬆️ force of contraction by opening more Ca++ channels = ⬆️ SV 3. Hormones • E, NE: same as SNS • Thyroid hormone (slow)
39
True or false: the waves observed on an ECG machine is the sum of the action potentials in the heart
False The waves are the sum of the electrical activity of ALL myocardial cells
40
What is occurring in the heart during the P wave?
Atrial depolarization, followed by contraction
41
What is occurring in the heart during the QRS wave?
Ventricular depolarization, followed by contraction (*atrial repolarization also occurs at this time)
42
What is occurring in the heart during the T wave?
Ventricular repolarization, followed by relaxation
43
What occurs during the following ECG intervals? P-Q S-T T-P
P-Q: atria contract, signals pass through AV node S-T: ventricles contract, atria relax T-P: heart at rest
44
One kind of abnormality of the heart beat is called Tachycardia. What does this mean?
Resting HR > 100bpm
45
One kind of abnormality of the heart beat is called Bradycardia. What does this mean?
Resting HR < 60bpm
46
One kind of abnormality of the heart beat is called Heart Block. What does this mean?
Conduction through AV node slowed ~> longer P-Q interval
47
What occurs during a 3rd degree heart block?
No conduction through AV node: > atria fire at SA node rate (~75AP/min) > ventricles fire at Bundle/Perkinje rate (30AP/min)
48
How is mean arterial pressure (MAP) calculated?
MAP = CO x TPR (total peripheral resistance)
49
What is total peripheral resistance (TPR)?
The resistance in ALL arterioles
50
Baroreceptor reflexes are a type of neural control (extrinsic) over the MAP. Explain what they are
They contain stretch receptors which monitor the MAP in the a) *carotid sinus* (brain BP) b) *aortic arch* (systemic BP)
51
Chemoreceptor reflexes are a type of neural control (extrinsic) over the MAP. Explain what they are
They respond to pH, CO2, and O2. They are found in the aortic arch and carotid sinus. They are involved in regulation of respiration, but they affect BP
52
If the MAP gets too high, how do baroreceptors address it?
Baroreceptor impulses ⬆️ \/ Medulla: \/ ⬇️SNS & ⬆️PSNS
53
If the pH or O2 concentration goes ⬇️, how do chemoreceptors respond?
Chemoreceptor impulses increase \/ Medullary cardiovascular center \/ ⬆️SNS & ⬆️epinephrine \/ ⬆️TPR, ⬆️HR, ⬆️CO \/ ⬆️MAP
54
What is the Renin-Angiotensin System?
A form of hormonal control over the MAP. The steps are: > ⬇️BP or Na+ ~> kidneys release RENIN (enzyme) into blood > renin converts ANGIOTENSINOGEN (protein) into ANGIOTENSIN I > ANGIOTENSIN-CONVERTING ENZYME (ACE) converts it to ANGIOTENSIN II in lungs > this causes: constricting blood vessels, ⬆️aldosterone, ADH RESULT: ⬆️MAP
55
What does atrial natriuretic peptide (ANP) cause?
⬇️renin, ⬇️aldosterone, ⬇️ADH = ⬇️urine production ⬇️vasoconstriction Overall ⬇️MAP
56
What are the 3 ways that solutes enter and leave capillaries?
1. Diffusion (major route) - usually between endothelial cells 2. Vesicular transport - large proteins (eg. antibodies) - occurs via *transcytosis* ~> passes through the cell 3. Mediated transport - requires membrane carrier protein - mainly in the brain
57
How do fluids (H2O) enter and leave capillaries?
1. Osmosis 2. Bulk flow (due to pressure differences) - BP - blood osmotic P (BOP): due to plasma proteins - ISF hydrostatic P (IFHP) - ISF osmotic P (IFOP): due to ISF proteins
58
Fluid leaving capillaries is called ______, and fluid entering capillaries is called ______.
filtration, absorption
59
What is the net filtration pressure (NFP)?
The sum of hydrostatic and osmotic pressures acting on the capillary NFP = (BHP + IFOP) - (BOP + IFHP)
60
What is edema and how does it occur?
Edema is an accumulation of fluid in the tissue (ISF) causing swelling Due to: > ⬆️BP > ⬆️IFOP > ⬇️BOP > obstructed lymph vessels
61
What is circulatory shock, and what are the 2 types?
Inadequate blood flow Types: 1. Hypovolemic shock - ⬇️blood volume - due to blood loss, burns, diarrhea, vomiting 2. Vascular shock - expanded blood vessels - systemic vasodilation (⬇️BP)
62
What are some examples of vascular shock?
Anaphylactic shock > allergic reactions > due to high histamine released from mast cells Septic shock > due to bacterial toxins Cardiogenic shock > pump failure (⬇️CO) > heart can’t sustain blood flow
63
What are the stages of circulatory shock?
1. Compensatory 2. Progressive 3. Irreversible
64
What is happening in the progressive stage of circulatory shock?
- bodily mechanisms inadequate: requires intervention - ⬇️CO, ⬇️cardiac activity - ⬇️blood to the brain, ⬇️CV control - damage to viscera, esp. kidneys
65
What are the functions of RBCs?
a) Transport O2 (iron) & CO2 (globin) b) Buffer: globin binds to H+ c) Carbonic anhydrase (CA): important for CO2 transport
66
What is jaundice?
Excess bilirubin in blood because: > excess RBC breakdown > liver dysfunction > blockage of bile excretion
67
What are the 2 types of WBCs?
Granulocytes & Agranulocytes
68
What are the 3 granulocytes?
Neutrophils > phagocytic > 1st to infected area Eosinophils > attack parasites > break down chemicals releases in allergic reactions Basophils > secrete histamine: ⬆️inflammation > secrete heparin: ❌local clotting
69
What is hemostasis?
The process of stopping bleeding. It involves: - Vascular Spasm - Platelet plug formation - Clot Formation - Clot retraction & repair - Fibrinolysis
70
What is vascular spasm?
Vasoconstriction of damaged arteries, arterioles - ⇓ blood flow (minutes to hours)
71
What occurs during platelet plug formation?
Platelets stick to damaged blood vessel, release chemicals (factors) which: a) cause more platelets to stick (+ feedback) b) promote clotting c) begin healing
72
What occurs during the 3 stages of clot formation?
1. Production of prothrombin activator by: i. extrinsic pathway – uses factors released by damaged tissues ii. intrinsic pathway - uses factors contained in blood ~> usually both together - require Ca++, tissue, platelet or plasma factors 2. Prothrombin converted to thrombin 3. Fibrinogen converted to fibrin
73
What is hemophilia?
Clotting is abnormal or absent > ~83% is type A: lack clotting factor 8
74
How do hormones regulate vasoconstriction/dilation (arteriolar radius)?
a) epinephrine - vasoconstriction = skin, viscera ~> reinforces SNS - vasodilation = heart, skeletal muscle, liver ~> opposes SNS b) other hormones - angiotensin II, ADH = vasoconstriction - histamine = vasodilation
75
What externally controls vasoconstriction/dilation (arteriolar radius)?
Nervous & Endocrine System
76
What is occurring during the absolute refractory period of myocardial APs that does not allow for another AP?
Na+ channels inactivated until MP is close to - 70 mV
77
Explain excitation-contraction coupling in myocardial cells
AP on sarcolemma causes: 1. Ca++ voltage gates open in T-tubules and release into ICF 2. Ca++ binds to chemical gates on SR, which causes a large ⬆️ in Ca++ in ICF 3. Ca++ binds to troponin, exposes myosin binding sites on actin 4. Crossbridges form ~> sliding filament mechanism ~> contraction
78
What is the approximate total blood volume in the body?
~5 L
79
What 3 things must be controlled to regulate MAP?
1. Cardiac Output 2. Total peripheral resistance (TPR) 3. Blood Volume
80
What is blood pressure?
Hydrostatic pressure exerted by blood on wall of vessel – results when flow is opposed by resistance
81
Aldosterone is a hormone secreted by the adrenal glands. How does it affect blood pressure?
It tells the nephrons to reabsorb more Na+ into the bloodstream, which causes H2O to follow due to osmotic pressure Result: ⬆️ BP
82
What are the 2 types of agranulocytes?
Monocytes & Lymphocytes
83
Describe the following blood clotting issues: - thrombus - embolus - hemophilia
thrombus = a stationary clot in an undamaged vessel embolus = free floating clot hemophilia = clotting abnormal/absent
84
What does blood plasma consist of?
1. H2O (~90%) 2. Proteins (~7%) - albumins - globulins - fibrinogen 3. Electrolytes (ions) 4. Other solutes

BIOL 1412 (15 decks)

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