Histology Of Nerve Anf Muscle In Health And Disease

Question 1

What is the basic structure of skeletal muscle

Answer 1

Skeletal muscle has the individual muscle fibres arranged in myofibers and arranged in bundles called fascicles.
There is 3 types of connective tissue within skeletal muscle including epimysium, perimysium and endomysium.
The skeletal muscle does have a basement membrane which surrounds the individual myofibers with collagen, glycoproteins and proteoglycans.
They also have a vascular supply

Question 2

What is the innervation of the skeletal muscle

Answer 2

Each muscle fibre is innervated by one nerve which has cell bodies in the anterior horn of the spinal cord/brainstem
One neurone is able to innervate multiple motor units of multiple muscle fibres
Nerve impulses pass over neuromuscular junctions

Question 3

How does a nerve impulse travel across the synapse at the neuromuscular junction

Answer 3

The nerve impulse reaches the synapse of the pre-synaptic neurone and this stimulates the release of acetyl-choline into the synaptic cleft which binds to post-synaptic acetyl-choline receptors on the post-synaptic membrane to allow the nerve impulse to continue to travel

Question 4

What does enzyme histochemistry

Answer 4

This revels different fibre types in a muscle biopsy

Question 5

What are type 1 muscle fibres

Answer 5

Type 1 fibres are reliant on oxidative, fatigue resistant but have a slow twitch

Question 6

What are type 2 muscle fibres

Answer 6

They are fatigued rapidly but are able to generate a large peak of muscle tension. Type 2 muscle fibres have a fast twitch

Question 7

What are the sub types of type 2 muscle fibres

Answer 7

2a- intermediate- glycolytic and oxidative
2b- glycolytic

Question 8

Why does the size of the motor unit vary between the muscles

Answer 8

Because of the need for fine motor skills

Question 9

What can loss of innervation of the muscle fibre cause

Answer 9

Can cause fibre atrophy

Question 10

What allows re innervation of muscle fibres which lose innervation

Answer 10

Collateral spouting of axons from adjacent motor units to re innervate that muscle fibre

Question 11

What does re innervation of muscle fibres result in

Answer 11

Larger motor units within the body
Conversion of fibre types in the muscle in fibre type grouping

Question 12

What is a sarcomere

Answer 12

Basic unit of contraction

Question 13

What is a sarcomere made up of

Answer 13

Repeating arrangements of thick filaments which are myosin and thin filaments which are actin

Question 14

What other proteins are present in a sarcomere

Answer 14

Alpha actinin
Titin
Nebulin
Desmin

Question 15

What is desmin for in a sarcomere

Answer 15

This links the myofibrils to each other and the sarcolemma

Question 16

What is linked to actin in skeletal muscle

Answer 16

Troponin C
Troponin I
Troponin T
Tropomyosin

Question 17

What is the tropomyosin complex linked to in skeletal muscle

Answer 17

Calcium regulation for contraction

Question 18

What is the theory of muscle contraction

Answer 18

The sliding filament theory

Question 19

What happens during sliding filament theory which causes the muscle contraction

Answer 19

The heads of the myosin bind to actin due to the presence of calcium ions which bind to troponin C lifting the tropomyosin complex from the actin. The heads of the myosin then bend at the hinge region and in turn pull the actin which shortens it and in turn shortening the length of the sarcomere and so producing the muscle contraction

Question 20

Where does the energy for immediate contraction come from

Answer 20

ATP

Question 21

What is creating kinase

Answer 21

This is an enzyme which binds phosphate to something so in this example phosphate is blinded to creating to replenish the creative phosphate energy stores in muscle fibres

Question 22

How can mitochondrial cytopathies be diagnosed

Answer 22

Through muscle biopsies

Question 23

What is a dystrophy

Answer 23

A dystrophy is a genetically determined destructive and progressive disorders affecting muscles

Question 24

What causes a muscle dystrophy

Answer 24

Defects of proteins that confer stability to the sarcolemma

Question 25

What protein maintains muscle stability

Answer 25

Dystrophin

Question 26

Where is dystrophin located

Answer 26

X-linked process, found on the short arm of chromosome 21

Question 27

What are disorders that can affect neuromuscular transmission

Answer 27

The most common is myasthenia gravis which is an autoimmune disease where anti-acetyl-choline receptor antibodies which reduces the binding of acetyl-choline could show progressive weakness

Question 28

How can neuromuscular transmission disorders be improved

Answer 28

Myasthenia gravis can be improved by acetyl cholinesterase

Question 29

What cell is responsible for the myelin sheath in the PNS

Answer 29

The Schwann cells

Question 30

What is a node of ranvier

Answer 30

This is a node on a axon where depolarisation of the axon occurs

Question 31

What does myelination of an axon allow for

Answer 31

Myelination allows for saltatory conduction

Question 32

What are pathologies of damage to motor/sensory neurons

Answer 32

Neuropathies

Question 33

What are pathologies of the damage to axons known as

Answer 33

Axonopathies

Question 34

What is it called when there is selective damage to the myelin sheath

Answer 34

Demyelination

Question 35

How does demyelination occur

Answer 35

Injury to Schwann cells or myelin sheath

Question 36

How does demyelination begin on an axon

Answer 36

With a thin myelin sheath

Question 37

What does demyelination result in

Answer 37

Functional impairment with slow conduction of action potential