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Physiology 202 > Unit 1 Lecture 2 and 3 > Flashcards

Unit 1 Lecture 2 and 3 Flashcards

1
Q

What does cardiac muscle consist of?

A
  • Branches
  • Striations
  • 1-2 nuclei
  • Mitochondria
  • Intercalated discs
  • gap junctions
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2
Q

what are the layers of cardiac muscle?

A

muscle -> muscle fiber -> myofibril

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3
Q

what makes up myofibrils?

A

actin and myosin

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4
Q

How are myofibrils arranged?

A

in sarcomeres

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5
Q

What is important of the branching pattern of cardiac muscle?

A

it forms a network that can make electrical impulses in all directions

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6
Q

what allows electrical impulses to pass quickly from one cell to the next?

A

gap junctions

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7
Q

Where are gap junctions located?

A

intercalated discs

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8
Q

What is also found in intercalated discs?

A

desmosomes

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9
Q

what is the importance of desmosomes?

A

hold adjacent cells together

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10
Q

What is the conduction system of the heart?

A

The system of the heart that causes it to contract

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11
Q

What structures make up the conduction system?

A

Sinoatrial (SA) node, Atriventricular (AV) node, Atrioventricular (AV) bundle (bundle of HIS), Right and left bundle branches, and purkinje fibers

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12
Q

What is the role of the SA node?

A

pacemaker

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13
Q

Where is the SA node found?

A

right atrial wall

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14
Q

What does the SA node, “pacemaker”, do?

A

spontaneously discharges action potentials at 100-120 beats/min

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15
Q

What modifies the rate of action potentials discharging in animals?

A

autonomic nerves

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16
Q

What is the resting heart rate (due to autonomic nerves)

A

70 beats/min

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17
Q

How do the atria and ventricles contract?

A

in a coordinated fashion

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18
Q

How is the cardiac muscle excited in the conduction system?

A

depolarization of the SA node

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19
Q

What generally happens during conduction of the heart?

A

electrical impulses travel down and across both atria -> atrial muscle fiber contraction

20
Q

What is found at the AV border during the conduction system?

A

poorly conducting tissue (small fibers, w/ few gap junctions)

21
Q

What does the poorly conducting tissues do

A

it slows the impulse by 0.1 sec

22
Q

What happens because of the effects of poorly conducting tissues?

A

the atria has more time to fully empty before the ventricles begin to contract

23
Q

What is connected to the atrioventricular (AV) node?

A

bundle of HIS

24
Q

What stems off of the bundle of HIS

A

right and left bundle branches and purkinje fibers

25
Q

What is the function of the bundle of HIS

A

transmits actions potentials into the right and left bundle branches, purkinje fibers and ventricles

26
Q

What portions of the ventricles contract first?

A

lower parts of the ventricles contract first to push the blood up the heart

27
Q

What are the 2 types of cells that contract the heart do to action potentials?

A
  1. Cardiac myocytes (heart muscle cells)

2. Pacemaker cells

28
Q

What is the first step in cardiac myocytes contracting the heart?

A

FAST Depolarization (gets less negative):

Na+ voltage-gated channels let Na+ in

29
Q

What is the second step in cardiac myocytes contracting the heart?

A

Plateau (maintained depolarization)

  • Ca2+ comes in slowly
  • Some K+ channels open and K+ leaks out
30
Q

What is the third step in cardiac myocytes contracting the heart?

A

Repolarization (gets more negative)

  • Ca2+ channels close
  • more K+ channels open
31
Q

Define refractory

A

unresponsive

32
Q

What does the refractory period mean in physiology?

A

It’s the time period when the muscle cells is unresponsive to stimulation

33
Q

What is the absolute refractory period?

A

the period when the cell will not respond regardless of the strength of stimuli

34
Q

What is the relative refractory period?

A

the period when the cell will respond only if the stimulus is “suprathreshold”

35
Q

What is special about pacemaker cells?

A

They are autorhythmic

36
Q

Define autorhythmic

A

They generate their own action potentials

37
Q

What is a pacemaker potential?

A

the resting membrane potential of pacemaker cells

38
Q

What is different about pacemaker potentials?

A

they are unstable

39
Q

What causes pacemaker cell depolarization?

A

calcium (not sodium)

40
Q

What is an electrocardiogram?

A

a COMPOSITE record of action potentials of all active cells in a heartbeat

41
Q

What are the different waves of an ECG?

A

P, QRS and T

42
Q

What is the P wave?

A

Depolarization of atria

43
Q

What is the PQ interval?

A

Atrial systole (contraction)

44
Q

What is the QRS wave?

A
  • Depolarization of ventricles

- Repolarization of atria

45
Q

What is the ST segment?

A

ventricular systole (contraction)

46
Q

What is the T wave?

A

Repolarization of ventricles

47
Q

What is after the T wave?

A

ventricular diastole (relaxation)

Physiology 202 (43 decks)

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