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PAR2021 Cardiology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

Describe the elements of contractile cardia cells.

A
  • Striated like skeletal muscle
  • Short, fat and branched
  • Interconnected
  • Cardiac cells interlock - intercalated discs
  • 25-34% of cardia cells are large mitochondria
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2
Q

What type of respiration does the heart rely on?

A

Almost exclusively on Aerobic respiration

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3
Q

What is the difference between cardiac and skeletal muscle?

A

Skeletal

  • Striated, long, cylindrical, multinucleated
  • No gap junctions between cells
  • Stimulated individually
  • Many T Tubules
  • Elaborate sarcoplasmic reticulum
  • Calcium binds to troponin
  • Supply of ATP through aerobic and anaerobic

Cardiac- striated, short, branched, 1-2 nuclei per cell

  • Has gap junctions
  • Fewer and wider T Tubules
  • Less elaborate sarcoplasmic reticulum
  • Calcuim binds to troponin
  • Supply of ATP through Aerobic respiration only
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4
Q

Are pacemaker cells extrinsic or intrinsic?

A

Intrinsic - they are self-excitable
- Spontaneously depolarise

-> cardia cells are connected through gap junction so they when pacemaker cells depolarise, it can depolarise all the cells.

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5
Q

Define cardiac contractility

A

Ability of fibres to shorten when stimulated

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6
Q

Define cardiac conductivity

A

Fibres transmit action potential easily

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7
Q

Define cardiac Excitability

A

Capactity to respond to a stimulus

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8
Q

Define cardiac Automaticity

A

Ability of heart to spontaneously depolarise without neuro-humoral control

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9
Q

What is the refractory period?

A

The time that the cell will not respond to a stimulus

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10
Q

What is expansibility?

A

The ability of the heart to stretch as it fills

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11
Q

What is the sequence of excitation in cardiac muscles?

A
  1. SA node generates impulse
  2. The impulse pauses (0.1s) at AV node
  3. AV bundle connects atria to ventricles
  4. Bundle branches conduct impulses through the inter-ventricular septum
  5. The subendocardial conducting network depolarises the contractile cells of both ventricles
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12
Q

What is the resting membrane potential of the cardiac muscles?

A

-90mV

  • high concentration of Na+ outside cell
  • Inside cell is negatively charges due to presence of high concentrations on anion (some cations are present in K+)
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13
Q

What is the threshold potential?

A

-70mV

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14
Q

How is resting membrane potential maintained?

A

RMP is maintained by Na+/K+ pump, using energy to move ions against concentration gradient

3Na+ out, 2K+ in

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15
Q

What happens during an action potential?

A
  • AP stimulation results in cell membrane becoming permeable to Na+ ions
  • As cell interior becomes less negative, fast sodium channels open at about -60mV to allow even more Na+ to enter cell
  • Depolarisation occurs when interior of cell reaches +20-+30mV compared to outside of cell
  • The depolarisation stimulates depolarisation in adjacent cell
  • Once depolarisation occurs, K+ begins moving into cell, restoring the negative environment through repolarisation`
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16
Q

When does depolarisation occur during an AP?

A

Depolarisation occurs when interior of cell reaches +20-+30mV compared to outside of cell

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17
Q

What occurs at Phase 0?

A

Rapid depolarisation
- Na+ into cell till +20-+30mV

  • occurs in 2ms
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18
Q

What occurs at Phase 1?

A

Beginning of repolarisation

  • Na+ channels close
  • K+ channels open
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19
Q

What occurs at Phase 2?

A

Plateau phase

  • K+ moving in
  • Slow Ca+ channels are opened
  • Cl- channels open in response to Ca+
  • Balances electrical signal for short period
20
Q

What occurs at Phase 3?

A

Repolarisation

  • K+ channels remain open
  • Na+/Ca+ exchanger open
  • Na+/K+ pumps open

Net outward current flow creating negative membrane potential

21
Q

What are the two parts to the refractory period?

A

Absolute refractory period (ARP)

Relative refractory period (RRP)

22
Q

When does the ARP start and finish?

A

Begins with phase 0
Ends half way through Phase 3

  • Approximately peak of T wave on ECG
  • Makes up 2/3 the overall refractory period
  • Because cardiac cells have not repolarised to their threshold potential (-60 to -70mV) they cannot pass on another action potential and contract.
23
Q

When does the RRP start and finish?

A

Half way through phase 3 to the end of phase 3

  • Downstroke of T wave on ECG
  • cardia cells have repolarised to their threshold potential and can be stimulated but another AP
24
Q

Describe the 3 steps on a pacemaker cells action potential

A

Pacemaker cells have unstable resting potential

  1. PACEMAKER POTENTIAL Slow depolarisation due to both opening of Na+ and closing of K+ channels
  2. DEPOLARISATION the AP begins when pacemaker potential reaches threshold.
    Depolarisation is due to Ca2+ influx through Ca2+ channels
  3. REPOLARISATION is due to Ca2+ channels inactivating and K+ opening, bringing membrane potential back to it’s most negative voltage
25
Q

What is the threshold potential for pacemaker cells?

A

-40mV

26
Q

What nervous system is the vagus nerve in?

A

Parasympathetics

27
Q

Where does the Cardioinhibitory and cardioaccelatry centres sit?

A

Medula oblongata

28
Q

Why is there no AP over the P wave?

A

P wave is passive

29
Q

What is perfusion?

A

The circulation of blood through the a vascular bed of tissue

-> The level of perfusion is determined by the ability to provide adequate blood supply to tissue or organs to provide nutritional demands and remove waste.

30
Q

What is the function of the cardiovascular system

A
  • Distribute oxygen and glucose
  • collect waste and return to elimination sites
  • thermoregulation
  • hormone distribution
31
Q

What are the components of the CV system?

A 
Heart - pumping force
Arteries - Distribution
Arterioles - Flow & pressure regulation
Capillaries - Exchange
Veins - Collection
32
Q

What is Hydrostatic pressure?

A

Force exerted by fluid pressing against a wall

33
Q

What is osmotic pressure?

A

The force that opposes hydrostatic pressure.

Movement of solutes

34
Q

What is the formula for Cardiac Output?

A

CO = HR x SV

35
Q

What is the formula for BP?

A

CO x R

36
Q

What are the four perfusion factors?

A
  • Heart Rate
  • Stroke Volume
  • Resistance
  • Viscocity
37
Q

What is the formula for Mean arterial pressure?

A

MAP = diastoilic pressure + (pulse pressure/3)

38
Q

How do you calculate pulse pressure?

A

Difference between systolic and diastolic pressure.

39
Q

What are the elements for blood pressure regulation?

A
  • Cardiac Centre
  • Vasomotor centre
  • Baroreceptors
  • Chemoreceptors
  • Adrenal medulla
  • Angiotensin II
  • Antidiuretic hormones
40
Q

Where does the parasympathetic and sympathetic NS originate

A

Parasympathetic - Medulla oblongata

Sympathetic - spinal cord

41
Q

Explain Starlings law

A
  • Increased venous return increases end diastolic vol.
  • Increased end diastolic volume causes stretching of ventricular wall
  • This results in an increase in the force of cardiac contraction
  • With all other factors remaining constant, the result is an increase in stroke vol, CO, and BP
42
Q

What diseases is hypertension a risk factor for?

A
  • Stroke
  • Renal failure
  • Chronic/congestive heart failure
  • Acute myocardial infarction
43
Q

What’s classes as normal BP?

A

<120 / <80

44
Q

What’s classed as high to normal BP?

A

120-139 / 80-89

45
Q

What’s classed as mild (Grade 1) hypertension?

A

140 - 159 / 90 - 99

46
Q

What’s classed as moderate (Grade 2) hypertension?

A

160 - 179 / 100 - 109

47
Q

What’s classed as severe (Grade 3) hypertension?

A

180/110

PAR2021 Cardiology (12 decks)

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