Neuromuscular Transmission ppt 7 Flashcards
(35 cards)
What is an NMJ?
Neuromuscular junction , the axons of motor neurons innervate skeletal muscle fibers.
The neuron intercept at the motor end plate
What are key features of a peripheral synapse?
- Only one motor neuron innervates a muscle fiber,
- Only excitatory input (no inhibitory input) is received by each muscle fiber,
- Only one neurotransmitter (Ach) activates the muscle fibers
- One kind of receptor channel (nicotinic acetylcholine receptor channel)
What are the key features of a central synapse?
- More complex than that at the nerve-muscle synapse.
- Inhibitory as well as excitatory inputs to a central neuron.
What is Myasthenia Gravis?
Is an autoimmune disease in which antibodies attack the Nicotinic Ach receptors.
Prevents the Muscle Contraction
What are the typical symptom of myasthenia graves?
muscle weakness that increases during periods of activity and improves after periods of rest
Myasthenia graves is usually associated with
underlying thymoma
What is a Tension test?
A test fo MG
Administration of edrophonium, a short acting AchE inhibitor, rapidly improves symptoms
What is abnormally elevated in patients with MG?
ACh antibodies. AntiMuSK antibody (30-40%)
What is the treatment for MG?
AChE inhibitors
Thymectomy
What is Lambert Eaton syndrome (LEMS)?
-Auto immune disease in which antibodies attack calcium channels in the PRESYNAPTIC terminal.
What are the typical symptoms of LEMS?
- Weakness of proximal arms and legs
- Affects the legs more than the arms.
- Difficulties climbing stairs and rising from a sitting position
LEMS is usually associated with
small cell lung cancer?
As oppose to MG, LEMS usually improves with
Exercise
What is Botulism?
-Clostridium botulinumis a bacterium that produces dangerous toxins that block nerve functions and can lead to respiratory and muscular paralysis.
What is the mechanism of action for Botulinum toxin?
Botulinum toxin is a specific protease that cleaves SNARE proteins present in the vesicular and presynaptic cell membranes. These SNARE proteins are involved in exocytosis, preventing the release of neurons transmitters.
What is the time os incubation for botulinum toxin?
normal: 12-36 hour
can be 6hr- 10 days
What is the presentation of a baby with infantile botulism?
Classic presentation for infantile botulism includes antecedent constipation with the ascending paralysis, ptosis, dilated or unreactive pupils, and weakness in the arms and legs.
What causes infantile botulism?
Spores in Honey
Types A and B- BAby
What is wound botulism?
- Spores get into an open wound and are able to reproduce in
- Two weeks to appear.
- Associated with injecting black tar heroin.
What is inhalation botulism?
- Does not occur naturally, it is associated with accidental or intentional (e.g. bioterrorism)
- The median lethal is three times greater than in foodborne cases.
What is tetanus?
- Clostridium bacteria that produce tetanus toxin.
- 7 to 21 days.
- Inhibitory spinal interneurons. Damage to which results in disinhibition of spinal motor neurons.
- Hyperexcitation= tetanic contractions
What is the MOA of tetanus toxin?
Protease that cleaves SNARE proteins, abolition of release of inhibitory neurotransmitter from spinal interneurons.
What is a neurotransmitter?
Chemical substance that is synthesized in a neuron, released at a synapse to elicit a specific response.
What is neruomodulator?
Chemical messenger released by a neuron that does not directly cause EPSPs or IPSPs but instead affects the strength of synaptic transmission.
