Flashcards in Somatic Nervous System And Muscle Contraction Deck (32)
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What are the three types of muscle?

β†’ Skeletal
β†’ Smooth
β†’ Cardiac


How many muscle fibres are there in bundles and what are they called?

β†’ fasciculi


What is the muscle fibre membrane called?

β†’ Sarcolemma


What is a muscle fibre made from?

β†’ 100s-1000s of myofibrils


What does the sarcoplasm contain?

β†’ glycogen
β†’ fat
β†’ mitochondria
β†’ enzymes


What does the sarcoplasmic reticulum do?

β†’ Release Ca2+


What is a sarcomere?

β†’ a contractile unit


What is the anisotropic band?

β†’ high density band


What is the isotropic band?

β†’ actin filaments
β†’ titin


Describe how the actin myosin binding sites are exposed

β†’ Troponin forms a complex with tropomyosin
β†’ When Ca2+ binds to troponin it causes a conformational change to the troponin
β†’ This causes the tropomyosin to move
β†’ It exposes the actin-myosin binding sites
β†’ Allows the myosin head to bind to the actin


Describe the sliding filament theory?

β†’ Motor neuron stimulates a muscle to contract
β†’ Release of Ca2+ into the muscle cell
β†’ myosin has a globular head that ATP binds to
β†’ ATP is hydrolysed
β†’ Phosphate bond breaking provides energy for the power stroke
β†’ releases ADP and an inorganic phosphate
β†’myosin head is cocked


What does the somatic nervous system do?

β†’ Provides voluntary control over skeletal muscle


What are motor neurons?

β†’ Efferent neurons that innervate muscle


What does one motor unit include?

β†’ A single motor neuron and all the muscle fibres it controls


How do motor units regulate the strength of contraction?

β†’ Varying how many activated motor units are recruited


Describe what happens at a neuromuscular junction when a stimulus is applied?

β†’ A stimulus from the brain causes an action potential
β†’ ACh is released
β†’ ACh binds to receptors and causes depolarisation of the membrane
β†’ depolarisation moves along the membrane and through T tubules
β†’ T tubules enter the muscle and cause depolarisation of the SR
β†’ SR releases Ca2+
β†’It is released into the cytosol and causes contraction of muscle fibres


What are the 2 types of cholinergic receptor?

β†’ Muscarinic
β†’ Nicotinic


How many molecules of ACh bind to a nicotinic receptor?

β†’ 2


What does a single action potential produce?

β†’ a single twitch


How do you get greater tension within a muscle?

β†’ if an additional action potential arrives before the muscle relaxes from the first action potential
β†’ There is summation of the two and greater contraction


What is tetanus?

β†’ When the rate of action potentials is so high that the muscle doesn't relax between stimuli


What is the mutated gene in DMD? (duchenne muscular dystrophy)

β†’ dystrophin


What is the function of dystrophin?

β†’ Connects the sarcomere to the plasma membrane


What happens to people with DMD?

β†’ unable to walk by 10-12 years
β†’ death by early to mid 20s


What are the effects of a lack of dystrophin?

β†’ Dysfunction of the sarcolemma stretch
β†’ ion pores open and there is increased intracellular Ca2+
β†’ membrane gets torn


What is an indication of muscle damage in DMD?

β†’ CK (creatine kinase) is lost from the cell and goes into the blood
β†’ degradation of structural proteins


what is creatine kinase needed for?

β†’ recycling of ATP


What enables patients with DMD to walk for longer?

β†’ corticosteroids like prednisone


What is the definition of motor neuron disease?

β†’ A group of disorders that selectively affect motor neurons


How do people with ALS die?

β†’ Ventilatory failure