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Physiology > Electrical Activity And Muscle Contraction > Flashcards

Electrical Activity And Muscle Contraction Flashcards

1
Q

What are heart cells called and the 2 types

A

Myocytes

1- conducting cells : fast spread of AP

2- work cells : cells which generate contraction force

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2
Q

Where are work cells found

A

In both Atria and ventricles

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3
Q

What are the 2 ways ap can spread in heart

A

Through conducting fibres

Cell to cell via gap junctions

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4
Q

Which cells have spontaneous depolarisation which causes contraction

A

SAN

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5
Q

When is the SAN

A

Right atrium

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6
Q

Where does AP spread from the san

A

To internodal pathways and then spread across both atria

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7
Q

How is ap spread to both atria before going to the AVN

A

Through gap junctions

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8
Q

Why is there a delay in ap spread down AVN

A

To allow all the blood to leave the atria after contraction

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9
Q

How does ap spread to the apex of heart

A

Down bundle of his , purkinje fibres

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10
Q

What do purkinje fibres on both sides of heart all

A

Ventricle contraction upwards of the heart

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11
Q

What is the spontaneous depolarisation of the SAN called

A

Pacemaker potential

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12
Q

What channel opens in the initial depolarisation in the SAN (pacemaker potential)

A

Non specific cation channels open and cations + flood into cell

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13
Q

Which channels open at the SAN to cause rapid depolarisation once reached threshold

A

Ca2+ channels

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14
Q

Which channels cause repolarisation at the SAN

A

Voltage gated K+ channels

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15
Q

Ap in the ventricle cells is different. What causes depolarisation

A

Voltage gated NA channels

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16
Q

Which channels initially cause repolarisation in ventricle cells

A

Fast opening K+ channels

17
Q

Why is there a plateau phase in repolarisation at ventricle cells

A

Voltage gated ca channels open and counteract the K+ channels leaving the cells

18
Q

What are the ca2+ called in ventricle AP

A

Trigger calcium

19
Q

What happens after plateau phase

A

Ca channels shut

Slow opening K channels open and cause repolarisation again

Goes to resting potential

20
Q

How is contraction triggered in ventricle cells

A

By the trigger ca flooding which bind at the SR to release Ca2+

21
Q

what are the channels which ca flood out of and later bind to troponin to cause contraction

A

Ryanodine receptor channels

22
Q

What are the 2 ways relaxation occurs

A

Removal of ca back to the sr via ca2ATPase channels

Or

Removal out of the cell via NA/ ca anti Porter

23
Q

Why can na/ca anti Porter work to remove ca out of cell

A

Gradient produced by the na/k pump

24
Q

What factor affects force/ contraction

A

Number of myosin actin cross bridges which is dependant on number of ca bound to troponin via trigger ca release out of SR

25
Q

When does muscle contraction first occur in response to an AP

A

At the plateau phase when trigger calcium enters cell

26
Q

How does the heart avoid tetanus

A

It has a long refractory period which allows muscle to relax first via removal of ca

27
Q

What machine records depolarisation and repolarisation of working cells(contracting)

A

Electrocardiogram ECG

28
Q

Why is ecg different to ap

A

Because it records sum of of electrical activity of all working cells

29
Q

What is the point in the ecg which is where heart is relaxed

A

Isoelectric point

30
Q

Which wave is first in an ecg and what does it represent

A

P wave

Represents atrial depolarisation

31
Q

What happens after P wave

A

QRS complex

32
Q

What is the dip at Q representing

A

Initial ventricular depolarisation

33
Q

What does R represent

A

Ventricular depolarisation

34
Q

What does S represent (downward curve at QRS)

A

Depolarisation upwards by purkinje fibres up the heart muscle

35
Q

What wave comes after the QRS complex and what does it show

A

T wave

It shows ventricular repolarisation

36
Q

What is the interval called between P and the R wave and what does it show

A

Pr interval

It shows the conduction down the AVN and bundle of His

37
Q

What is the interval called between S/Q and T

A

ST interval

Start of repolarisation of the ventricle

38
Q

What is an irregular rhythm called

A

Arrhythmias

39
Q

What are the 2 types of arrhythmia

A

1- impulse propagation : random AP occurrence and slow firing

2- impulse initiation : uncontrollable AP firing in atria or ventricle = atrial fibrillation/ ventricular fibrillation

Physiology (31 decks)

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