9. Biochemistry I - Contractility Flashcards
what are the MUSCULAR PUMPS and what are the RESERVOIRS of the HEART
pumps : VENTRICLES
reservoirs : ATRIA
4 VALVES of the HEART:
right ventricle:
- TRICUSPID
- PULMONARY
left ventricle:
- MITRAL, BICUSPID
- AORTIC
what CELLS LINE INTERNAL WALLS of the HEART
- INNER LAYER of heart
ENDOCARDIUM - ENDOTHELIAL CELLS
what are the SPECIALISED MUSCLE CELLS of the HEART (middle layer)
MYOCARDIUM - MYOCYTES
what are the CELLS that COVER the HEART - OUTERMOST LAYER of heart that protect it
EPICARDIUM - MESOTHELIAL CELLS (thin layers epithelium) and CONNECTIVE TISSUE
what is the name of the FIBROUS / TOUGH MEMBRANOUS SAC that the HEART is CONTAINED IN
PERICARDIUM
- SEROUS - VISCERAL and PARIETAL
- FIBROUS
what is found between the EPICARDIAL and PERICARDIAL LAYERS
PERICARDIAL SAC
Characteristics of CARDIAC MUSCLE
- STRIATED
- INVOLUNATRY
- SHORT, CYLINDRICAL
- BRANCHES
- UNI-NUCLEATED
- arranged in NETWORK
how do CARDIAC MUSCLES CONTRACT? (speed)
how do they TIRE?
contract QUICKLY and RHYTHMICALLY
but DO NOT get FATIGUED
SHAPE of SMOOTH MUSCLE CELLS
SPINDLE SHAPED
arranged in SHEETS
how do SMOOTH MUSCLES CELLS CONTRACT? how do they TIRE?
Contract SLOWLY, DO NOT get FATIGUED
shape of SKELETAL MUSCLE CELLS
LONG, CYLINDRICAL UNBRANCHED CELLS
(multi-nuclei)
arranged in BUNDLES
how do SKELETAL MUSCLE CELLS CONTRACT? how do they TIRE?
contract QUICKLY but GET FATIGUED
are CARDIAC MUSCLE CELLS (cardiac MYOCYTES) long or short
SHORT
(& CYLINDRICAL, BRANCHED)
CARDIAC MYOCYTES are SEPARATED BY… at the cell junctions
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
approx DIAMETER SIZE of CARDIAC MYOCYTE
25 μm
approx LENGTH of CARDIAC MYOCYTE
100 μm
what is the SARCOLEMMA in CARDIAC MYOCYTES
PLASMA MEMBRANE
the SARCOLEMMA has TRANSVERSE INVAGINATIONS called … that have ION CHANNELS which transmit the electrical excitation inside the cell
T-TUBULES
CARDIAC MYOCYTES are ABUNDANT in ….
MITOCHONDRIA for energy demand
- occupy 1/3 of cell volume
what in CARDIAC MYOCYTES STORE CA2+ IONS
SARCOPLASMIC RETICULUM
(CARDIAC) MYOCYTES are composed of BUNDLES of…
MYOFIBRILS, containing MYOFILAMENTS
what is the name of the BASIC CONTRACTILE UNITS of MYOCYTES
- distinct, repeating microanatomical units in MYOFIBRILS
SARCOMERES
SARCOMERE is a REGION of MYOFILAMENT strucutres BETWEEN 2 …
between two Z-LINES
with THICK MYOSIN filament and THIN ACTIN filament
average LENGTH of a SARCOMERE
2 μm
which FILAMENT is THICK and which is THIN
THICK - MYOSIN
THIN - ACTIN
STAGES in the CARDIAC CYCLE
- VENTRICULAR FILLING
(diastole and then atrial systole completes)
- inlet valves (tricuspid, mitral) open - ISOVOLUMETRIC PHASE (HIGH PRESSURE)
(ventricular systole)
- both VALVES CLOSED - EJECTION AND ATRIAL FILLING
(ventricular systole)
- Outlet Valves Open (pulmonary, aortic)
ventricular pressure exceeds arterial pressure - ISOVOLUMETRIC PHASE (LOW PRESSURE)
(ventricular diastole)
- both valves CLOSED
until atrial pressure exceeds ventricular pressure (repeat)
what is QT INTERVAL
in ECG, time between Q and T waves
- time in which ventricles DEPOLARISE and REPOLARISE
measure of DURATION of VENTRICULAR ACTION POTENTIAL
what is the NORMAL QT INTERVAL
440 ms
what happens when QT INTERVAL is ABOVE 440 ms ie 630 ms
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
which ACTION POTENTIAL has an UNSTABLE, slow rising RESTING POTENTIAL at around -60 mv
(pacemaker or non-pacemaker cells)
SA NODE PACEMAKER CELLS
How is the RESTING POTENTIAL of NON-PACEMAKER cells in VENTRICLE
FLAT, STABLE at -90 mv
how are ACTION POTENTIAL LENGTH in CARDIAC MUCLES (myocardial) as opposed to SKELETAL MUSCLE cells
LONGER ACTION POTENTIALS - 200+ ms
1-5ms action potential in skeletal muscle
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)
LONGER REFRACTORY PERIOD in CARDIAC MUSCLE
- for protection, prevent tetanus
how is the response if STIMULATED during the ARP - ABSOLUTE REFRACTORY PERIOD
(non-pacemaker action potential)
NO RESPONSE
when do get NON-PROPAGATED RESPONSE (non-spread)
(non-pacemaker action potential)
if STIMULATED BETWEEN ARP (ABSOLUTE REFRACTORY PERIOD) and ERP (EFFECTIVE REFRACTORY PERIOD)
when can you get a PROPAGATED ACTION POTENTIAL (spreads)
(non-pacemaker action potential)
AFTER ERP (EFFECTIVE REFRACTORY PERIOD)
what is the KEY MESSENGER for CONTRACTION
intracellular CALCIUM CA2+ Influx
what is EXCITATION-CONTRACTION COUPLING (ECC)
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
what is the 1st thing that happens when the ACTION POTENTIAL enters from adjacent cell and ENTERS T-TUBULE
VOLTAGE-GATED CA2+ CHANNELS / L-TYPE Ca2+ channels OPEN
CALCIUM-INDUCED CALCIUM RELEASE:
Ca2+ INFLUX induces CA2+ RELEASE from SARCOPLASMIC RETICULUM by OPENING which RECEPTORS
(causes Ca2+ sparks)
RYANODINE RECEPTORS-CHANNELS on SR
What is an ACTIN FILAMENT covered in that BLOCKS MYOSIN BINDING SITE
TROPOMYOSIN - has TROPONINS
what does CA2+ RELEASE / SPARKS cause that allow for CONTRACTION
CA2+ ions BIND to TROPONIN on ACTIN FILAMENT
- TROPOMYOSIN MOVES / slides and MYOSIN BINDING SITE is EXPOSED
so myosin can bind -> power stroke
STEPS of the CARDIAC CONTRACTION CYCLE with the SLIDING FILAMENTS (after ca2+ binding causes exposure of myosin binding site on actin)
- MYOSIN heads SPLIT ATP into ADP and PI, MYOSIN is ACTIVATED
- MYOSIN BINDS to ACTIN (binding site) and FORMS CROSS-BRIDGES
- POWER STROKE: RELEASE of ADP + PI
myosin head rotates towards centre of sarcomere / actin pulled closer to centre of myosin which shortens sarcomere - ATP BINDS MYOSIN, MYOSIN DETACHES FROM ACTIN
repeat cycle
when does RELAXATION OCCUR
when CA2+ UNBINDS from TROPONIN
- TROPOMYOSIN COVERS BINDING SITE on actin
- Filaments SLIDE BACK to relaxed position
what happens to the CALCIUM after in UNBINDS from TROPONIN during RELAXATION
- 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
CA2+ REMOVED FROM CELL during RELAXATION by which TRANSPORTER
NCX ANTIPORTER
- 3 Na+ IN
- 1 Ca2+ OUT
CA2+ REMOVED FROM CELL during RELAXATION by which TRANSPORTER
NCX ANTIPORTER
- 3 Na+ IN
- 1 Ca2+ OUT
how is NA+ GRADIENT MAINTAINED to allow for EXCHANGE with CA2+ during RELAXTION
by NA+ - K+ ATP-ASE
- 3 NA+ OUT
- 2 K+ IN
what causes MYOSIN to DETACH from ACTIN
when ATP BINDS to it
where is the RYANODINE RECEPTOR CHANNEL found
on SARCOPLASMIC RETICULUM - Ca2+ release through
