Neuromuscular dysfunction

1. M S . S H A M A P R A V E E N
T U T O R P H Y S I O L O G Y
Neuromuscular dysfunction

2. Myasthenia Gravis
 Autoimmune disease
 Characterized by weakness and fatigability of skeletal
muscles that gradually worsens as the muscles are
used.
 Decrease in the number of AChR present on the
motor end plate due to production of circulating
autoantibodies against these receptors.
 Postsynaptic folds are flattened or simplified.

3. Features
 Due to postsynaptic changes along with the presynaptic
rundown, after a few motor nerve impulses, the
successive contractile responses become feebler, causing
fatigue.
 Women are affected more than men in a ratio of 3:2.
 The muscle weakness increases during prolonged use of
the muscle & improves after rest or sleep.
 The extraocular muscles and eyelids are often involved
early in the course of diseases. Therefore, diplopia and
ptosis (drooping of eyelids) are early symptoms.
 Proximal limb muscles are commonly affected. In severe
cases, respiratory muscle paralysis leads to death.

4. Ptosis seen in Myasthenia Gravis

5. Physiological basis of treatment
 Administration of AChE inhibitors: Pyridostigmine
& neostigmine (increase the concentration of Ach at
the neuromuscular junction.
 Thymectomy: it blunts down the immune response
and improve the condition.
 Immunosuppression: immunosuppressive drugs
glucocoticoids and azathioprine are useful.
 Plasmapheresis: it removes AChR antibodies from
plasma.

6. Lambert- Eaton Myasthenic Syndrome
 Presynaptic disorder of the neuromuscular junction due
to production of autoantibodies against voltage- gated
Ca++ channels.
 The decreased Ca++ influx in the presynaptic axon
terminals results in impaired Ach release from the nerve
endings.
 The muscular weakness is primarily seen in the limb
muscles.
 Patients show incremental response to repetitive nerve
stimulation as calcium level raises with AP. With
prolonged contractions, muscle strength increases.

8. THANK YOU