Histology Of Nerve And Muscle

Question 1

Skeletal muscle connective tissue- 3

Answer 1

Endomysium- between muscle fibres
Perimysium- wraps bundles
Epimysium- around outside of muscle

There also is a basement membrane

Question 2

Skeletal muscle innervation

Answer 2

Each fibre inner ages by 1 nerve

One Neuton innervates multiple muscle fibres called a motor unit

Question 3

Describe skeletal neuromuscular junction

Answer 3

Synaptic

Uses acetyl choline- bonds to post synaptic AChR

Question 4

What is propixeption (muscle length and tension) in skeletal muscle supplied by

Answer 4

Muscle spindles- encapsulated intrafusal fibres. Mediate stretch reflex and proprioception.
Golgi tendon organs- tension

Question 5

Where are UMN

Answer 5

Precentral gyrus

Question 6

Where do UMN cross over

Answer 6

Pyramidal decussation in caudal part of medulla

Question 7

Muscle Fibre Types

Answer 7

Slow twitch (red fibres)- type 1, oxidative, fatigue resistant

Fast twitch- fatigue rapidly but generate large peak of muscle tension

2A- glycolysis and oxidative (intermediate)
2B- glycolytic (white)

Question 8

Define Motor Unit

Answer 8

LMN and the fibres it innervates

Question 9

Reaction to denervation pf motor unit

Answer 9

Collateral sprouting from adjacent motor units to allow reinnervation- larger MU result
Fibre type may change

Question 10

Sarcomere

Answer 10

Basic unit of contraction

Repeating myosin and actin

Question 11

Describe sliding filament model

Answer 11

Myosin head binds to actin
Hydrolysis of ATP provides energy for conformational change of myosin head, pulling the actin
Sarcomeric shortening due to sliding filaments NOT change in length of either actin or myosin
Initiated by increased calcium ions

Question 12

What are the the accessory proteins on the sliding filament model

Answer 12

Troponin/ tropomyosin- mediate calcium ion regulation

Nebulin/ Titin- regulated architecture of the filament

Question 13

Short term energy source in muscle

Answer 13

Creatine phosphate
CP is replenished by creatine kinase
CK released on muscle fibre damage so high blood serum CK- clinically useful

Question 14

Mitochondrial cytopathies

Answer 14

Disorder due to mutations in mitochondrial gene. Maternal inheritance.

Question 15

Mitochondrial cytopathies diagnosis

Answer 15

Muscle biopsy- ragged red fibres are accumulations of mitochondria. Look for cytochrome oxidase negative fibres.

Question 16

Define dystrophy

Answer 16

Genetically determined, destructive and mainly progressive disorder of muscle.
Defects of proteins that affect stability to sarcolemma
Eg duchenne

Question 17

Neuromuscular transmission

Answer 17

Nerve impulse causes release of acetyl choline from synaptic vesicles
ACh binds to receptors
Action entry results in depolarisation
Action potential travels across the muscle cell membrane and into the T tubule system
Calcium is released from the sarcoplasmic reticulum leading to activation of contraction
Dissociated ACh is hydrolysed by acetylcholineesterase in NMJ

Question 18

Disorders of Neuromuscular transmission

Answer 18

Myasthenia Gravis- Variable weakness, progressive with sustained effort, eye Singh- ptosis
Autoimmune
Anti-AChR antibodies so less ACh

Question 19

Cell responsible for myelination in PNS

Answer 19

Schwann cell.

Each Schwann cell responsible for one segment of myelin.

Question 20

Cell responsible for myelination in CNS

Answer 20

Ogliodendrocyte

Question 21

Where does depolarisation occur

Answer 21

Node of ranvier

Question 22

Type of conduction in muscle

Answer 22

Saltatory

Question 23

Damage to motor or sensory Neuron

Answer 23

Neuropathies