9. Biochemistry I - Contractility

Question 1

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

Answer 1

pumps : VENTRICLES
reservoirs : ATRIA

Question 2

4 VALVES of the HEART:

Answer 2

right ventricle:
- TRICUSPID
- PULMONARY

left ventricle:
- MITRAL, BICUSPID
- AORTIC

Question 3

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

Answer 3

ENDOCARDIUM - ENDOTHELIAL CELLS

Question 4

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

Answer 4

MYOCARDIUM - MYOCYTES

Question 5

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

Answer 5

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

Question 6

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

Answer 6

PERICARDIUM
- SEROUS - VISCERAL and PARIETAL
- FIBROUS

Question 7

what is found between the EPICARDIAL and PERICARDIAL LAYERS

Answer 7

PERICARDIAL SAC

Question 8

Characteristics of CARDIAC MUSCLE

Answer 8

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

Question 9

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

Answer 9

contract QUICKLY and RHYTHMICALLY

but DO NOT get FATIGUED

Question 10

SHAPE of SMOOTH MUSCLE CELLS

Answer 10

SPINDLE SHAPED

arranged in SHEETS

Question 11

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

Answer 11

Contract SLOWLY, DO NOT get FATIGUED

Question 12

shape of SKELETAL MUSCLE CELLS

Answer 12

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

Question 13

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

Answer 13

contract QUICKLY but GET FATIGUED

Question 14

are CARDIAC MUSCLE CELLS (cardiac MYOCYTES) long or short

Answer 14

SHORT
(& CYLINDRICAL, BRANCHED)

Question 15

CARDIAC MYOCYTES are SEPARATED BY… at the cell junctions

Answer 15

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

Question 16

approx DIAMETER SIZE of CARDIAC MYOCYTE

Answer 16

25 μm

Question 17

approx LENGTH of CARDIAC MYOCYTE

Answer 17

100 μm

Question 18

what is the SARCOLEMMA in CARDIAC MYOCYTES

Answer 18

PLASMA MEMBRANE

Question 19

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

Answer 19

T-TUBULES

Question 20

CARDIAC MYOCYTES are ABUNDANT in ….

Answer 20

MITOCHONDRIA for energy demand

• occupy 1/3 of cell volume

Question 21

what in CARDIAC MYOCYTES STORE CA2+ IONS

Answer 21

SARCOPLASMIC RETICULUM

Question 22

(CARDIAC) MYOCYTES are composed of BUNDLES of…

Answer 22

MYOFIBRILS, containing MYOFILAMENTS

Question 23

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

Answer 23

SARCOMERES

Question 24

SARCOMERE is a REGION of MYOFILAMENT strucutres BETWEEN 2 …

Answer 24

between two Z-LINES

with THICK MYOSIN filament and THIN ACTIN filament

Question 25

average LENGTH of a SARCOMERE

Answer 25

2 μm

Question 26

which FILAMENT is THICK and which is THIN

Answer 26

THICK - MYOSIN THIN - ACTIN

Question 27

STAGES in the CARDIAC CYCLE

Answer 27

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)

Question 28

what is QT INTERVAL

Answer 28

in ECG, time between Q and T waves - time in which ventricles DEPOLARISE and REPOLARISE measure of DURATION of VENTRICULAR ACTION POTENTIAL

Question 29

what is the NORMAL QT INTERVAL

Answer 29

440 ms

Question 30

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

Answer 30

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

Question 31

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

Answer 31

SA NODE PACEMAKER CELLS

Question 32

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

Answer 32

FLAT, STABLE at -90 mv

Question 33

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

Answer 33

LONGER ACTION POTENTIALS - 200+ ms 1-5ms action potential in skeletal muscle

Question 34

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)

Answer 34

LONGER REFRACTORY PERIOD in CARDIAC MUSCLE - for protection, prevent tetanus

Question 35

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

Answer 35

NO RESPONSE

Question 36

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

Answer 36

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

Question 37

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

Answer 37

AFTER ERP (EFFECTIVE REFRACTORY PERIOD)

Question 38

what is the KEY MESSENGER for CONTRACTION

Answer 38

intracellular CALCIUM CA2+ Influx

Question 39

what is EXCITATION-CONTRACTION COUPLING (ECC)

Answer 39

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

Question 40

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

Answer 40

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

Question 41

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

Answer 41

RYANODINE RECEPTORS-CHANNELS on SR

Question 42

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

Answer 42

TROPOMYOSIN - has TROPONINS

Question 43

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

Answer 43

CA2+ ions BIND to TROPONIN on ACTIN FILAMENT - TROPOMYOSIN MOVES / slides and MYOSIN BINDING SITE is EXPOSED so myosin can bind -> power stroke

Question 44

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

Answer 44

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

Question 45

when does RELAXATION OCCUR

Answer 45

when CA2+ UNBINDS from TROPONIN - TROPOMYOSIN COVERS BINDING SITE on actin - Filaments SLIDE BACK to relaxed position

Question 46

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

Answer 46

- 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

Question 47

CA2+ REMOVED FROM CELL during RELAXATION by which TRANSPORTER

Answer 47

NCX ANTIPORTER - 3 Na+ IN - 1 Ca2+ OUT

Question 48

CA2+ REMOVED FROM CELL during RELAXATION by which TRANSPORTER

Answer 48

NCX ANTIPORTER - 3 Na+ IN - 1 Ca2+ OUT

Question 49

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

Answer 49

by NA+ - K+ ATP-ASE - 3 NA+ OUT - 2 K+ IN

Question 50

what causes MYOSIN to DETACH from ACTIN

Answer 50

when ATP BINDS to it

Question 51

where is the RYANODINE RECEPTOR CHANNEL found

Answer 51

on SARCOPLASMIC RETICULUM - Ca2+ release through