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MECHANISM OF MUSCULAR CONTRACTION - Coggle Diagram
MECHANISM OF MUSCULAR CONTRACTION
NEUROMUSCULAR JUNCTION
THE POINT WHERE NEURONE MEETS SKELETAL MUSCLE
SKELETAL MUSCLE IS MADE OF HUNDREDS OF CYLINDRICAL MUSCLE FIBRES
BOUNDED BY SARCOLEMMA MEMBRANE
CONTAINS MYOFIBRILS COVERED WITH CYTOPLASM (SARCOPLASM)
HAS SARCOPLASMIC RETICULUM
MADE UP OF MYOFIBRILS, COMPOSING OF THICK FILAMENT (MYOSIN) & THIN FILAMENT (ACTIN, TROPONIN, TROPOMYOSIN)
MECHANISM
EXPLAINED USING THE SLIDING FILAMENT HYPOTHESIS OF MUSCULAR CONTRACTION BY HUXLEY AND HANSON
WHEN MUSCLE IS RESTING, OUTSIDE IS (+) & INSIDE IS (-)
ARRIVAL OF IMPULSE CAUSES DEPOLARISATION OF FIBRE - INSIDE BECOMES (+) & OUTSIDE BECOMES (-)
ACTION POTENTIAL IS GENERATED & SPREADS INTO FIBRE THROUGH T-TUBULES, THIS STIMULATES SARCOPLASMIC RETICULUM TO RELEASE Ca2+ INTO SARCOPLASM
Ca2+ ATTACHES TO TROPONIN CAUSING TROPONIN AND TROPOMYOSIN TO MOVE AWAY FROM MYOSIN BINDING SITE
AT THE SAME TIME, AN ATP ATTACHED ITSELF TO MYOSIN HEAD WHICH CONTAINS ATPASE ENZYME
ATP IS HYDROLYSED INTO ADP + P, CAUSING MYOSIN HEAD TO BECOME ACTIVATED AND BENT. THE HEAD THEN ATTACHES TO THE MYOSIN BINDING SITE ON THE ACTIN, FORMING CROSS-BRIDGES
THE RELEASE OF ADP + P FROM MYOSIN HEAD RETURNS IT TO THE ORIGINAL CONFORMATION, CAUSING IT TO PULL THE ACTIN INWARDS IN A SLIDING MOVEMENT
ATTACHMENT OF NEW ATP TO MYOSIN HEAD DETACHES THE CROSS-BRIDGE
CYCLE REPEATS WITH CROSS-BRIDGES REFORMING A LITTLE FURTHER ALONG THIN FILAMENT
H-BAND, I-BAND & SARCOMERE SHORTEN BUT WIDTH OF A-BAND REMAINS THE SAME
WHEN IMPULSE STOPS, Ca 2+ IS ABSORBED BACK INTO SARCOPLASMIC RETICULUM. MYOSIN BINDING SITES WILL BE BLOCKED AGAIN & NO CROSS-BRIDGES ARE FORMED
MUSCLE RELAXES & FILAMENT SLIDES BACK TO THE RESTING STATE
AUTONOMIC NERVOUS SYSTEM
CONTROLS INVOLUNTARY ACTIVITIES (HEART RATE, PERISTALSIS, SWEATING)
CONSISTS OF MOTOR NEURONES PASSING TO THE SMOOTH MUSCLES OF ORGANS
MOTOR NEURONE IS MADE UP OF PREANGLIONIC NEURONE FROM CNS
SYNAPSES WITH ONE OR MORE POSTANGLIONIC NEURONES WHICH LEAD TO EFFECTORS
DIVISIONS
SYMPATHETIC NERVOUS SYSTEM (FIGHT OR FLIGHT)
PARASYMPATHETIC NERVOUS SYSTEM (REST & DIGEST)
DRUG ABUSE & ADDICTION
DRUGS INTERFERE WITH IMPULSE TRANSMISSION
ENHANCING IMPULSE TRANSMISSION
BLOCK REABSORPTION OF NEUROTRANSMITTER INTO SYNAPTIC KNOB
INHIBIT FORMATION OR ACTION OF ENZYMES INVOLVED IN HYDROLYSIS OF NEUROTRANSMITTERS
MIMIC ACTIONS OF NEUROTRANSMITTERS
DELAYING IMPULSE TRANSMISSION
BREAKING DOWN NEUROTRANSMITTERS
INHIBIT FORMATION OR ACTION OF NEUROTRANSMITTER
PREVENT RELEASE OF NEUROTRANSMITTER
DRUG GROUPS
STIMULANTS
CAFFEINE
NICOTINE
COCAINE
DEPRESSANTS
TRANQUILISERS
SEDATIVES (BARBITURATES
ANTI-DEPRESSANTS
HEROIN
MORPHINE
HALLUCINOGENS
LSD
MARIJUANA
INHALANTS
ETHER
CHLOROFORM
GUMS / GLUE