Flashcards in Somatic Nervous System And Muscle Contraction Deck (32)
What are the three types of muscle?
How many muscle fibres are there in bundles and what are they called?
What is the muscle fibre membrane called?
What is a muscle fibre made from?
→ 100s-1000s of myofibrils
What does the sarcoplasm contain?
What does the sarcoplasmic reticulum do?
→ Release Ca2+
What is a sarcomere?
→ a contractile unit
What is the anisotropic band?
→ high density band
What is the isotropic band?
→ actin filaments
Describe how the actin myosin binding sites are exposed
→ Troponin forms a complex with tropomyosin
→ When Ca2+ binds to troponin it causes a conformational change to the troponin
→ This causes the tropomyosin to move
→ It exposes the actin-myosin binding sites
→ Allows the myosin head to bind to the actin
Describe the sliding filament theory?
→ Motor neuron stimulates a muscle to contract
→ Release of Ca2+ into the muscle cell
→ myosin has a globular head that ATP binds to
→ ATP is hydrolysed
→ Phosphate bond breaking provides energy for the power stroke
→ releases ADP and an inorganic phosphate
→myosin head is cocked
What does the somatic nervous system do?
→ Provides voluntary control over skeletal muscle
What are motor neurons?
→ Efferent neurons that innervate muscle
What does one motor unit include?
→ A single motor neuron and all the muscle fibres it controls
How do motor units regulate the strength of contraction?
→ Varying how many activated motor units are recruited
Describe what happens at a neuromuscular junction when a stimulus is applied?
→ A stimulus from the brain causes an action potential
→ ACh is released
→ ACh binds to receptors and causes depolarisation of the membrane
→ depolarisation moves along the membrane and through T tubules
→ T tubules enter the muscle and cause depolarisation of the SR
→ SR releases Ca2+
→It is released into the cytosol and causes contraction of muscle fibres
What are the 2 types of cholinergic receptor?
How many molecules of ACh bind to a nicotinic receptor?
What does a single action potential produce?
→ a single twitch
How do you get greater tension within a muscle?
→ if an additional action potential arrives before the muscle relaxes from the first action potential
→ There is summation of the two and greater contraction
What is tetanus?
→ 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)
What is the function of dystrophin?
→ Connects the sarcomere to the plasma membrane
What happens to people with DMD?
→ unable to walk by 10-12 years
→ death by early to mid 20s
What are the effects of a lack of dystrophin?
→ Dysfunction of the sarcolemma stretch
→ ion pores open and there is increased intracellular Ca2+
→ membrane gets torn
What is an indication of muscle damage in DMD?
→ CK (creatine kinase) is lost from the cell and goes into the blood
→ degradation of structural proteins
what is creatine kinase needed for?
→ recycling of ATP
What enables patients with DMD to walk for longer?
→ corticosteroids like prednisone
What is the definition of motor neuron disease?
→ A group of disorders that selectively affect motor neurons