Somatic Nervous System And Muscle Contraction

Question 1

What are the three types of muscle?

Answer 1

→ Skeletal
→ Smooth
→ Cardiac

Question 2

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

Answer 2

→ fasciculi

Question 3

What is the muscle fibre membrane called?

Answer 3

→ Sarcolemma

Question 4

What is a muscle fibre made from?

Answer 4

→ 100s-1000s of myofibrils

Question 5

What does the sarcoplasm contain?

Answer 5

→ glycogen
→ fat
→ mitochondria
→ enzymes

Question 6

What does the sarcoplasmic reticulum do?

Answer 6

→ Release Ca2+

Question 7

What is a sarcomere?

Answer 7

→ a contractile unit

Question 8

What is the anisotropic band?

Answer 8

→ high density band

Question 9

What is the isotropic band?

Answer 9

→ actin filaments

→ titin

Question 10

Describe how the actin myosin binding sites are exposed

Answer 10

→ 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

Question 11

Describe the sliding filament theory?

Answer 11

→ 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

Question 12

What does the somatic nervous system do?

Answer 12

→ Provides voluntary control over skeletal muscle

Question 13

What are motor neurons?

Answer 13

→ Efferent neurons that innervate muscle

Question 14

What does one motor unit include?

Answer 14

→ A single motor neuron and all the muscle fibres it controls

Question 15

How do motor units regulate the strength of contraction?

Answer 15

→ Varying how many activated motor units are recruited

Question 16

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

Answer 16

→ 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

Question 17

What are the 2 types of cholinergic receptor?

Answer 17

→ Muscarinic

→ Nicotinic

Question 18

How many molecules of ACh bind to a nicotinic receptor?

Answer 18

→ 2

Question 19

What does a single action potential produce?

Answer 19

→ a single twitch

Question 20

How do you get greater tension within a muscle?

Answer 20

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

Question 21

What is tetanus?

Answer 21

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

Question 22

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

Answer 22

→ dystrophin

Question 23

What is the function of dystrophin?

Answer 23

→ Connects the sarcomere to the plasma membrane

Question 24

What happens to people with DMD?

Answer 24

→ unable to walk by 10-12 years

→ death by early to mid 20s

Question 25

What are the effects of a lack of dystrophin?

Answer 25

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

Question 26

What is an indication of muscle damage in DMD?

Answer 26

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

Question 27

what is creatine kinase needed for?

Answer 27

→ recycling of ATP

Question 28

What enables patients with DMD to walk for longer?

Answer 28

→ corticosteroids like prednisone

Question 29

What is the definition of motor neuron disease?

Answer 29

→ A group of disorders that selectively affect motor neurons

Question 30

How do people with ALS die?

Answer 30

→ Ventilatory failure

Question 31

What is myasthenia gravis?

Answer 31

→chronic autoimmune motor neuron disease

→ Body makes antibodies against AChRs at neuromuscular junctions

Question 32

How do you treat myasthesia gravis?

Answer 32

→ ACh inhibitors