Skeletal muscle A and P

Question 1

Priamry job of the skeletal muscle

Answer 1

To develop tension/force through contraction or shortening of the muscle

Force can only develop in one direction

Question 2

Secondary jobs of the skeletal muscle

Answer 2

*Store E and proteins
*Convert energy to heat eg through shivering to maintain core body temp
* Voluntary control over openings
*Protect and support internal organs

Question 3

Structure of a skeletal muscle

Answer 3

*Huge fibres, cylindrical, striated, multinucleate with lots of protein
*Connective tissue that ensheaths the fibres and connects them to the bones
*Highly vascular and has lots of nerves (stimulus for muscles)
*20-40 µm

Question 4

Junction where muscle meets tendon

Answer 4

Myotendenous junction

Question 5

Structure of the muscle

Answer 5

muscle fibre (made of myofibrils) + connective tissue + endomyseum –> Bundle of muscle fibre makes fascicle + connective tissue + perimyseum –> muscle + connective tissue + epimyseum

CT at muscle and bone ends

Question 6

Myofibril

Answer 6

Made of repeating units called Sarcomeres, has thin actin and thick myosin (REFER TO IMAGE). These are contractile proteins

Question 7

Sarcolemma and transverse tubules - Organelles

Answer 7

*Sarcolemma - the cell membrane
* Transverse tubules - extension of the sarcolemma, wraps around a myofibril to form an extensive network of tubular extensions (invaginations) , they run deep into the muscle to run contractions through APs

Question 8

SR - Organelle

Answer 8

forms a membranous network surrounding the muscle fibre, has intervals with the transverse tubule at the terminal cisternae where it gets signals to release Ca2+ for APs

Question 9

Triad

Answer 9

The place where two terminal cisternae meet with one transverse tubule

Question 10

How are signals passed through the muscle?

Answer 10

Sarcolemma –> transverse tubule –> triad –> terminal cisternae

Question 11

Actin - contractile protein

Answer 11

• Thin, made of two types Globular (G) and F actin. Forms ropy twists that terminate at the z discs.

Slides say that the G actin combine to form the F actin

Question 12

Myosin - contractile protein

Answer 12

Has a long tail and a globular head, they formed in arrays of pairs that face the M line but move away from the M line

Question 13

How does contraction occur

Answer 13

Force travels in one direction and this is possible due to the contraction of the sarcomere towards the M line (z discs move inwards)

Question 14

Sliding filament theory

Answer 14

Myosin and actin slide against each other towards the M line to produce contraction = force

Question 15

Pathway of the electrical signal

Answer 15

APs in brain Brain –> spinal cord –> motor neurons in spinal cord –> motor axons –> muscle fibres

Question 16

What are sarcomeres made of?

Answer 16

Myofilaments - actin and myosin, M line, connects at z discs

Question 17

What is a myofibril made of

Answer 17

Repeating units of sarcomeres

*covered with SR, transverse tubules, have trials at intervals and covered with a sarcolemma

Question 18

What is a muscle fibre made of?

Answer 18

Many microfibrils, covered with a endomyseum

Question 19

What is a fascicle made of?

Answer 19

Many muscle fibres, covered with perimyseum

Question 20

What is a muscle cell?

Answer 20

A muscle fibre

Question 21

What is a muscle made of?

Answer 21

Made of many fascicles, covered with epimyseum.

Question 22

Where does the nerve meet the muscle?

Answer 22

Neuromuscular junction i.e a specialised synapse

Question 23

How many points does a myelinated axon terminate to on a muscle fibre?

Answer 23

1

Question 24

What is a motor unit?

Answer 24

A motor unit + all the muscle fibres it controls

Question 25

What is a synaptic transmission?

Answer 25

At a neuromuscular junction, the transmission of the signal that initiates APs in muscle for muscle contraction