Ch 50

Question 1

Name 2 types of striated muscle

Answer 1

Cardiac & Skeletal muscle

Question 2

The striations are due to contractile units called

Answer 2

Sarcomeres

Question 3

A single muscle cell is a muscle fiber, which contains a bundle of myofibrils. What makes up the myofibrils?

Answer 3

Microfilaments

Question 4

Define Microfilaments

Answer 4

thick filaments called myosin & thin filaments called actin

Question 5

When the muscle contracts, what happens to the sarcomeres?

Answer 5

They shorten. Actin & myosin will overlap & shorten sarcomeres

Question 6

Name events in order that occur from the moment action potential reaches synaptic terminal of a motor neuron at neuromuscular junction to muscle contraction

Answer 6

1) VG Ca++ channels open & Ca++ enters synaptic terminal
2) Neurotransmitter release of acetylcholine from synaptic vesicles
3) Acetylcholine binds to muscle fiber receptors & causes action potential in skeletal muscle
4) The muscle action potential causes Ca++ to be released from Sarcoplasmic Reticulum
5) Calcium binds to troponin & moves tropomyosin out of
myosin binding sites on actin filaments to cause contraction

Question 7

Name events in order that occur withIn sarcomeres to cause muscle contraction

Answer 7

1) Sarcomeres are in relaxed state; ATP is bound to myosin heads
2) ATP is hydrolyzed to ADP & Pi on Myosin Head
3) Myosin head forms a cross bridge to actin thin filaments
4) Pi & ADP are removed from myosin heads connected to Actin, which causes a Power Stroke
5) ATP binds to myosin heads & causes them to detach from Actin. Sarcomeres relax once more

Question 8

Why do muscles enter a contracted state during rigor mortis?

Answer 8

as cells die, they stop making ATP that is needed to bind to myosin to detach from actin & cause sarcomeres to relax. With no ATP, muscles are stuck in power stroke contracted state. ATP is required for muscle relaxation