Excitation Contraction Coupling in Cardiac and Skeletal Muscle Flashcards
what occurs during depolarisation of the muscle fibre?
- somatic motor neuron releases ACh at NMJ
2. net entry of Na+ through ACh receptor-channel initiates a muscle AP
what is the role of the transverse tubule?
- AP is propagated from the end plate along the surface of the muscle fibre (sarcolemma)
- AP is propagated into the fibre down the t-tubule membrane
- depolarisation of the t-tubule membrane is “signalled” to membrane of terminal cisternae
where is calcium recycled between?
- sarcoplasmic reticulum/terminal cisternae
- cytoplasm
give examples of junctional foot proteins
- dihydropyridine receptor protein (DHPR)
- ryanodine receptor protein (RYR)
what is dihydropyridine receptor protein (DHPR)?
L-type voltage-gated calcium channel in the t-tubule membrane
what is ryanodine receptor protein (RYR)?
calcium release channel in the SR
What happens during muscular contraction (at the terminal cisternae)?
- somatic motor neuron releases Ach at NMJ
- net entry of Na+ through ACh receptor-channel initiates a muscle AP
- AP in t-tubule alters conformation of DHP receptor
- DHP receptor opens Ca2+ release channels in SR and Ca2+ enters cytoplasm
- Ca2+ binds to troponin, allowing strong actin-myosin binding
what is the significance of the increase in intracellular calcium concentration?
KEY event:
ultimately leads to force generation through interaction of actin and myosin filaments
give an example of a voltage-gated Ca2+ channel blocking drug?
nifedipine
what is nifedipine used to treat?
smooth muscle:
- hypertension
- migraine
- atherosclerosis
what is nifedipine?
a voltage-gated Ca2+ channel blocking drug
what is dantrolene?
spasmolytic drug acting as a skeletal muscle relaxant
what is dantrolene used to treat?
sarcoplasmic reticulum:
muscle spasm
- cerebral palsy, MS
- malignant hyperthermia
what is SERCA?
Ca2+ ATPase Sarcoplasmic Endoplasmic Reticulum Calcium ATPase
what is calcium concentration for muscle to be relaxed?
< 10-7 M
