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Cardiovascular > 9. Biochemistry I - Contractility > Flashcards

9. Biochemistry I - Contractility Flashcards

1
Q

what are the MUSCULAR PUMPS and what are the RESERVOIRS of the HEART

A

pumps : VENTRICLES
reservoirs : ATRIA

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2
Q

4 VALVES of the HEART:

A

right ventricle:
- TRICUSPID
- PULMONARY

left ventricle:
- MITRAL, BICUSPID
- AORTIC

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3
Q

what CELLS LINE INTERNAL WALLS of the HEART
- INNER LAYER of heart

A

ENDOCARDIUM - ENDOTHELIAL CELLS

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4
Q

what are the SPECIALISED MUSCLE CELLS of the HEART (middle layer)

A

MYOCARDIUM - MYOCYTES

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5
Q

what are the CELLS that COVER the HEART - OUTERMOST LAYER of heart that protect it

A

EPICARDIUM - MESOTHELIAL CELLS (thin layers epithelium) and CONNECTIVE TISSUE

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6
Q

what is the name of the FIBROUS / TOUGH MEMBRANOUS SAC that the HEART is CONTAINED IN

A

PERICARDIUM
- SEROUS - VISCERAL and PARIETAL
- FIBROUS

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7
Q

what is found between the EPICARDIAL and PERICARDIAL LAYERS

A

PERICARDIAL SAC

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8
Q

Characteristics of CARDIAC MUSCLE

A
  • STRIATED
  • INVOLUNATRY
  • SHORT, CYLINDRICAL
  • BRANCHES
  • UNI-NUCLEATED
  • arranged in NETWORK
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9
Q

how do CARDIAC MUSCLES CONTRACT? (speed)
how do they TIRE?

A

contract QUICKLY and RHYTHMICALLY

but DO NOT get FATIGUED

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10
Q

SHAPE of SMOOTH MUSCLE CELLS

A

SPINDLE SHAPED

arranged in SHEETS

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11
Q

how do SMOOTH MUSCLES CELLS CONTRACT? how do they TIRE?

A

Contract SLOWLY, DO NOT get FATIGUED

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12
Q

shape of SKELETAL MUSCLE CELLS

A

LONG, CYLINDRICAL UNBRANCHED CELLS
(multi-nuclei)
arranged in BUNDLES

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13
Q

how do SKELETAL MUSCLE CELLS CONTRACT? how do they TIRE?

A

contract QUICKLY but GET FATIGUED

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14
Q

are CARDIAC MUSCLE CELLS (cardiac MYOCYTES) long or short

A

SHORT
(& CYLINDRICAL, BRANCHED)

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15
Q

CARDIAC MYOCYTES are SEPARATED BY… at the cell junctions

A

INTERCALATED DISCS

  • have DESMOSOMES and GAP JUNCTIONS

desmosomes tie adjacent cells together, allowing force to be transferred

gap junctions electrically connect cells together, allow waves of depolarisation to spread for simultaneous contraction

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16
Q

approx DIAMETER SIZE of CARDIAC MYOCYTE

A

25 μm

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17
Q

approx LENGTH of CARDIAC MYOCYTE

A

100 μm

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18
Q

what is the SARCOLEMMA in CARDIAC MYOCYTES

A

PLASMA MEMBRANE

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19
Q

the SARCOLEMMA has TRANSVERSE INVAGINATIONS called … that have ION CHANNELS which transmit the electrical excitation inside the cell

A

T-TUBULES

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20
Q

CARDIAC MYOCYTES are ABUNDANT in ….

A

MITOCHONDRIA for energy demand

  • occupy 1/3 of cell volume
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21
Q

what in CARDIAC MYOCYTES STORE CA2+ IONS

A

SARCOPLASMIC RETICULUM

22
Q

(CARDIAC) MYOCYTES are composed of BUNDLES of…

A

MYOFIBRILS, containing MYOFILAMENTS

23
Q

what is the name of the BASIC CONTRACTILE UNITS of MYOCYTES
- distinct, repeating microanatomical units in MYOFIBRILS

A

SARCOMERES

24
Q

SARCOMERE is a REGION of MYOFILAMENT strucutres BETWEEN 2 …

A

between two Z-LINES

with THICK MYOSIN filament and THIN ACTIN filament

25
Q

average LENGTH of a SARCOMERE

A

2 μm

26
Q

which FILAMENT is THICK and which is THIN

A

THICK - MYOSIN
THIN - ACTIN

27
Q

STAGES in the CARDIAC CYCLE

A
  1. VENTRICULAR FILLING
    (diastole and then atrial systole completes)
    - inlet valves (tricuspid, mitral) open
  2. ISOVOLUMETRIC PHASE (HIGH PRESSURE)
    (ventricular systole)
    - both VALVES CLOSED
  3. EJECTION AND ATRIAL FILLING
    (ventricular systole)
    - Outlet Valves Open (pulmonary, aortic)
    ventricular pressure exceeds arterial pressure
  4. ISOVOLUMETRIC PHASE (LOW PRESSURE)
    (ventricular diastole)
    - both valves CLOSED

until atrial pressure exceeds ventricular pressure (repeat)

28
Q

what is QT INTERVAL

A

in ECG, time between Q and T waves
- time in which ventricles DEPOLARISE and REPOLARISE

measure of DURATION of VENTRICULAR ACTION POTENTIAL

29
Q

what is the NORMAL QT INTERVAL

A

440 ms

30
Q

what happens when QT INTERVAL is ABOVE 440 ms ie 630 ms

A

LONG QT SYNDROME
- Diagnosis of CARDIAC ARRYTHMIA

can lead to VENTRICULAR FIBRILLATION (rapid, uncoordinated contraction, more like quiver so heart not pumping blood out to body)
and SUDDEN DEATH

31
Q

which ACTION POTENTIAL has an UNSTABLE, slow rising RESTING POTENTIAL at around -60 mv
(pacemaker or non-pacemaker cells)

A

SA NODE PACEMAKER CELLS

32
Q

How is the RESTING POTENTIAL of NON-PACEMAKER cells in VENTRICLE

A

FLAT, STABLE at -90 mv

33
Q

how are ACTION POTENTIAL LENGTH in CARDIAC MUCLES (myocardial) as opposed to SKELETAL MUSCLE cells

A

LONGER ACTION POTENTIALS - 200+ ms

1-5ms action potential in skeletal muscle

34
Q

how are REFRACTORY PERIODS (time when unable to generate another action potential to allow enough time for chambers to refill) in CARDIAC and SKELETAL MUSCLE
(non-pacemaker action potential)

A

LONGER REFRACTORY PERIOD in CARDIAC MUSCLE

  • for protection, prevent tetanus
35
Q

how is the response if STIMULATED during the ARP - ABSOLUTE REFRACTORY PERIOD
(non-pacemaker action potential)

A

NO RESPONSE

36
Q

when do get NON-PROPAGATED RESPONSE (non-spread)
(non-pacemaker action potential)

A

if STIMULATED BETWEEN ARP (ABSOLUTE REFRACTORY PERIOD) and ERP (EFFECTIVE REFRACTORY PERIOD)

37
Q

when can you get a PROPAGATED ACTION POTENTIAL (spreads)
(non-pacemaker action potential)

A

AFTER ERP (EFFECTIVE REFRACTORY PERIOD)

38
Q

what is the KEY MESSENGER for CONTRACTION

A

intracellular CALCIUM CA2+ Influx

39
Q

what is EXCITATION-CONTRACTION COUPLING (ECC)

A

Series of events that link the ACTION POTENTIAL (excitation) of the muscle cell membrane (the sarcolemma)
- starting from the opening of Na+ Channels and Depolarisation, then Ca2+ Channels open and Ca2+ influx

to muscular CONTRACTION
- by Ca2+ release from SR and cross-bridge force production, power stroke

40
Q

what is the 1st thing that happens when the ACTION POTENTIAL enters from adjacent cell and ENTERS T-TUBULE

A

VOLTAGE-GATED CA2+ CHANNELS / L-TYPE Ca2+ channels OPEN

41
Q

CALCIUM-INDUCED CALCIUM RELEASE:
Ca2+ INFLUX induces CA2+ RELEASE from SARCOPLASMIC RETICULUM by OPENING which RECEPTORS

(causes Ca2+ sparks)

A

RYANODINE RECEPTORS-CHANNELS on SR

42
Q

What is an ACTIN FILAMENT covered in that BLOCKS MYOSIN BINDING SITE

A

TROPOMYOSIN - has TROPONINS

43
Q

what does CA2+ RELEASE / SPARKS cause that allow for CONTRACTION

A

CA2+ ions BIND to TROPONIN on ACTIN FILAMENT

  • TROPOMYOSIN MOVES / slides and MYOSIN BINDING SITE is EXPOSED
    so myosin can bind -> power stroke
44
Q

STEPS of the CARDIAC CONTRACTION CYCLE with the SLIDING FILAMENTS (after ca2+ binding causes exposure of myosin binding site on actin)

A
  1. MYOSIN heads SPLIT ATP into ADP and PI, MYOSIN is ACTIVATED
  2. MYOSIN BINDS to ACTIN (binding site) and FORMS CROSS-BRIDGES
  3. POWER STROKE: RELEASE of ADP + PI
    myosin head rotates towards centre of sarcomere / actin pulled closer to centre of myosin which shortens sarcomere
  4. ATP BINDS MYOSIN, MYOSIN DETACHES FROM ACTIN

repeat cycle

45
Q

when does RELAXATION OCCUR

A

when CA2+ UNBINDS from TROPONIN

  • TROPOMYOSIN COVERS BINDING SITE on actin
  • Filaments SLIDE BACK to relaxed position
46
Q

what happens to the CALCIUM after in UNBINDS from TROPONIN during RELAXATION

A
  • PUMPED BACK INTO SARCOPLASMIC RETICULUM via an ATP-ASE
  • REMOVED OUT OF CELL as EXCHANGED FOR NA+
    by NCX ANTIPORTER
    3NA+ IN
    1 CA2+ OUT
47
Q

CA2+ REMOVED FROM CELL during RELAXATION by which TRANSPORTER

A

NCX ANTIPORTER

  • 3 Na+ IN
  • 1 Ca2+ OUT
48
Q

CA2+ REMOVED FROM CELL during RELAXATION by which TRANSPORTER

A

NCX ANTIPORTER

  • 3 Na+ IN
  • 1 Ca2+ OUT
49
Q

how is NA+ GRADIENT MAINTAINED to allow for EXCHANGE with CA2+ during RELAXTION

A

by NA+ - K+ ATP-ASE

  • 3 NA+ OUT
  • 2 K+ IN
50
Q

what causes MYOSIN to DETACH from ACTIN

A

when ATP BINDS to it

51
Q

where is the RYANODINE RECEPTOR CHANNEL found

A

on SARCOPLASMIC RETICULUM - Ca2+ release through

Cardiovascular (16 decks)

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