Skeletal Muscle

Question 1

What is fasciculations?

Answer 1

These are small involuntary muscle movements from muscle contraction and relaxation which are visible under the skin.

Question 2

Describe the structure of a circular muscle.

Answer 2

These have concentric fibres and act as sphincters, to adjust the size of an opening.

Question 3

What are the different types of parallel muscle?

Answer 3

Fan shaped: close together at one end and a wider spread at the other
Strap: shaped like a strap
Fusiform: wider and cylindrical in the middle and taper off at the ends.

Question 4

What are the different types of muscle?

Answer 4

Circular, parallel and penate.

Question 5

What are the different types of penate muscle?

Answer 5

Unipennate: fasicles attach to same side of tendon
Bipennate: fasicles attach to both sides of a central tendon
Multi penate: central tendon branches and fasicles attach to this

Question 6

What is a pennate muscle?

Answer 6

This is a muscle which has one or more aponeurosis running through the tissue from the tendon, leading to fasicles being present.

Question 7

How are origin and insertion defined in muscles?

Answer 7

The origin is the area with the larger mass and the insertion is on the structure which is moved by the muscle.

Question 8

What is compartment syndrome?

Answer 8

In the limbs, the muscles are split into compartments which are surrounded by tough fascia. If there is bleeding in a compartment then this leads to a build up of pressure which causes pain on rest.

Question 9

What is the treatment for compartment syndrome?

Answer 9

Fasciotomy

Question 10

In terms of muscle movements, what is an agonist?

Answer 10

This is the prime mover of a muscle

Question 11

What is an antagonist in terms of muscle movement?

Answer 11

These oppose the agonists (prime movers) but are necessary for fine motor control to be possible.

Question 12

What is a synergist?

Answer 12

This is a muscle which assists the agonist in the movement, however alone is unable to perform the movement.

Question 13

What is the role of neutralisers in muscle movements?

Answer 13

These remove unwanted affects caused by the agonist.

Question 14

What function of muscle movement do fixators have?

Answer 14

These hold a body part still whilst another is moving.

Question 15

What is isotonic muscle contraction?

Answer 15

This is where tension in the muscle remains constant but length varies.

Question 16

What is the difference between concentric and eccentric muscle contraction?

Answer 16

Concentric is where the muscle shortens whilst eccentric is where the muscle is exerting a force whilst extended

Question 17

Give an example of eccentric muscle contraction

Answer 17

Walking downhill

Question 18

Give an example of isometric muscle contraction

Answer 18

Hand grip

Question 19

What is isometric muscle contraction?

Answer 19

This is where tension varies in a muscle but muscle length remains constant.

Question 20

What is the distribution on a first class level?

Answer 20

In this case, the fulcrum is central with load and effort at opposite ends.

Question 21

Where is load found in a second class lever?

Answer 21

Load is in the middle of the lever and the fulcrum is at one end.

Question 22

What is the class of lever in which effort is acting in the middle with load at one end and the fulcrum at the other?

Answer 22

Third class lever

Question 23

What is a motor unit?

Answer 23

This is a motor neurone and the muscle fibres it innervates

Question 24

What can be said about all the muscle fibres in a motor unit?

Answer 24

They will all have the same contractile type (fast/slow)

Question 25

What is a muscle spindle?

Answer 25

This is a structure innervated by two sensory and one motor neurone. The motor neurone keeps the muscle taught whilst the sensory fibres relay rate of change of muscle length.

Question 26

Where on the muscle is the muscle spindle found?

Answer 26

It is walled off from the rest of the muscle by a collagen sheath.

Question 27

What condition can cause platings to struggle to perform accurate movement in the absence of vision?

Answer 27

Large-fibre sensory neuropathy

Question 28

State two things which control muscle contraction force:

Answer 28

Size principle: small motor neurones will be recruited first and this means it starts with the slow type fibres and progresses to the faster fibres Rate code: multiple action potentials sum up to increase force of contraction.

Question 29

What is the limit of summation of action potentials in skeletal muscle called?

Answer 29

Tetanus

Question 30

What is muscle tone?

Answer 30

This is stiffness and tension retained by muscle and controlled by motor control centres in the brain.

Question 31

What is hypotonia?

Answer 31

This is lack of muscular tone.

Question 32

Describe the process which occurs at a Neuromuscular junction

Answer 32

The action potential causes voltage gated calcium channels to open and calcium influx. This causes release of acetylcholine containing vesicles which cross the synaptic cleft and hint to nicotinic acetylcholine receptors. This opens sodium channels and this depolarises membrane and so calcium channels open. Calcium flows into the cell and binds to troponin, causing conformational change and allowing myosin heads to bind to actin molecule.

Question 33

What facilitates muscle relaxation?

Answer 33

Calcium is pumped back into the sarcoplasmic recticulum by SERCA.

Question 34

What enzyme is responsible for the breakdown of acetylcholine in the synaptic cleft?

Answer 34

Acetylcholineesterase

Question 35

What ion channel is important for repolarisation after the action potential?

Answer 35

Cl-

Question 36

What is myotonia?

Answer 36

This is a condition where you cannot relax muscles at your own will due to ion channelopathies.

Question 37

What ion channel mutation is common for causing myotonia congenita?

Answer 37

Cl-

Question 38

What is the difference between most excitable cells and skeletal muscle?

Answer 38

Most return to their resting membrane potential by the action of K+ however in skeletal muscle Cl- has a major role in repolarisation.