Lecture 25: Skeletal Muscle: Structure & Function

Question 1

Why do we need cardiac muscle?

Answer 1

• The main function is to contract and make sure that the heart is pumping blood

Question 2

Why do we need smooth muscle?

Answer 2

• For the control of movement of fluids contraction = movement of blood, urine, digested food

Question 3

Why do we need skeletal muscle?

Answer 3

• To move
• Maintain posture
• Heat generation (numerous + highly active)

Question 4

Structure of Skeletal Muscle

Answer 4

• Muscle
• Muscle bundle
• Muscle Fibre / Myocyte / Muscle Cell
• Myofibril
• Sarcomere
• Myofilaments

Question 5

The skeletal muscle cell membrane is called the….and the cytoplasm is called…

Answer 5

• Sarcolemma

- Sarcoplasm

Question 6

The contractile unit is called the…

Answer 6

• Sarcomere

Question 7

The sarcoplasmic reticulum acts as an….

Answer 7

• Internal calcium store

Question 8

A triad is a…

Answer 8

• T-tubule sandwiched between two sarcoplasmic reticulum

Question 9

The motor unit consists of ….

Answer 9

• One somatic neuron and muscle fibres innervated by its branched

Question 10

Excitation occurs at the….an AP reaches end of motor neuron, which causes _____ entry into nerve terminal. Synaptic vesicles release ____, which diffuse into synaptic cleft. ____ stimulates receptors on the adjacent muscle fibre. ____polarisation of muscle sarcolemma, initiating an action potential. ______ coupling occurs. AP travels over _____ and T-Tubules, triggering release of _____ ions from the adjacent _____ _____. Ca2+ ions diffuse in the _______ where a cross-bridge formation occurs.

Answer 10

• Neuromuscular Junction
• Ca2+
• ACh
• De
• Electro-chemical-electro
• Sarcolemma
• Ca2+
• Sarcoplasmic Reticulum
• Myofilaments

Question 11

What is cross-bridge cycling?

Answer 11

• The myosin head is in an energised state, with ATP bound. In this stage it has a high affinity to bind with the actin
• Calcium interacted with troponin which exposes active sites
• Actin and Myosin interact
• Energised myosin head pulls the actin / POWERSTROKE
• Each part is driven by high energy bonds of ATP

Question 12

Do the actin and myosin become shorter?

Answer 12

• No, they just slide into each other

Question 13

What is the powerstroke?

Answer 13

• The flipping of the myosin head

Question 14

How does uncoupling of the cross-bridge formation occur?

Answer 14

• ATP must bind to the myosin

Question 15

During the relaxation state there’s ______ re-uptake and _____ of the cross-bridge.

Answer 15

• Calcium

- Uncoupling