Histology Of Nerve And Muscle Flashcards
Skeletal muscle connective tissue- 3
Endomysium- between muscle fibres
Perimysium- wraps bundles
Epimysium- around outside of muscle
There also is a basement membrane
Skeletal muscle innervation
Each fibre inner ages by 1 nerve
One Neuton innervates multiple muscle fibres called a motor unit
Describe skeletal neuromuscular junction
Synaptic
Uses acetyl choline- bonds to post synaptic AChR
What is propixeption (muscle length and tension) in skeletal muscle supplied by
Muscle spindles- encapsulated intrafusal fibres. Mediate stretch reflex and proprioception.
Golgi tendon organs- tension
Where are UMN
Precentral gyrus
Where do UMN cross over
Pyramidal decussation in caudal part of medulla
Muscle Fibre Types
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)
Define Motor Unit
LMN and the fibres it innervates
Reaction to denervation pf motor unit
Collateral sprouting from adjacent motor units to allow reinnervation- larger MU result
Fibre type may change
Sarcomere
Basic unit of contraction
Repeating myosin and actin
Describe sliding filament model
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
What are the the accessory proteins on the sliding filament model
Troponin/ tropomyosin- mediate calcium ion regulation
Nebulin/ Titin- regulated architecture of the filament
Short term energy source in muscle
Creatine phosphate
CP is replenished by creatine kinase
CK released on muscle fibre damage so high blood serum CK- clinically useful
Mitochondrial cytopathies
Disorder due to mutations in mitochondrial gene. Maternal inheritance.
Mitochondrial cytopathies diagnosis
Muscle biopsy- ragged red fibres are accumulations of mitochondria. Look for cytochrome oxidase negative fibres.
Define dystrophy
Genetically determined, destructive and mainly progressive disorder of muscle.
Defects of proteins that affect stability to sarcolemma
Eg duchenne
Neuromuscular transmission
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
Disorders of Neuromuscular transmission
Myasthenia Gravis- Variable weakness, progressive with sustained effort, eye Singh- ptosis
Autoimmune
Anti-AChR antibodies so less ACh
Cell responsible for myelination in PNS
Schwann cell.
Each Schwann cell responsible for one segment of myelin.
Cell responsible for myelination in CNS
Ogliodendrocyte
Where does depolarisation occur
Node of ranvier
Type of conduction in muscle
Saltatory
Damage to motor or sensory Neuron
Neuropathies
