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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
What is the function of the bundle of HIS
transmits actions potentials into the right and left bundle branches, purkinje fibers and ventricles
26
What portions of the ventricles contract first?
lower parts of the ventricles contract first to push the blood up the heart
27
What are the 2 types of cells that contract the heart do to action potentials?
1. Cardiac myocytes (heart muscle cells) | 2. Pacemaker cells
28
What is the first step in cardiac myocytes contracting the heart?
FAST Depolarization (gets less negative): Na+ voltage-gated channels let Na+ in
29
What is the second step in cardiac myocytes contracting the heart?
Plateau (maintained depolarization) - Ca2+ comes in slowly - Some K+ channels open and K+ leaks out
30
What is the third step in cardiac myocytes contracting the heart?
Repolarization (gets more negative) - Ca2+ channels close - more K+ channels open
31
Define refractory
unresponsive
32
What does the refractory period mean in physiology?
It's the time period when the muscle cells is unresponsive to stimulation
33
What is the absolute refractory period?
the period when the cell will not respond regardless of the strength of stimuli
34
What is the relative refractory period?
the period when the cell will respond only if the stimulus is "suprathreshold"
35
What is special about pacemaker cells?
They are autorhythmic
36
Define autorhythmic
They generate their own action potentials
37
What is a pacemaker potential?
the resting membrane potential of pacemaker cells
38
What is different about pacemaker potentials?
they are unstable
39
What causes pacemaker cell depolarization?
calcium (not sodium)
40
What is an electrocardiogram?
a COMPOSITE record of action potentials of all active cells in a heartbeat
41
What are the different waves of an ECG?
P, QRS and T
42
What is the P wave?
Depolarization of atria
43
What is the PQ interval?
Atrial systole (contraction)
44
What is the QRS wave?
- Depolarization of ventricles | - Repolarization of atria
45
What is the ST segment?
ventricular systole (contraction)
46
What is the T wave?
Repolarization of ventricles
47
What is after the T wave?
ventricular diastole (relaxation)

Physiology 202 (43 decks)

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