Neuromuscular Junction Flashcards
What gap junctions made of?
Connexon channels
What type of synapses are gap junctions?
Electrical synapses
Where are gap junctions (electrical synapses) present?
In cardiac and smooth muscle
Where are chemical synapses present?
Skeletal muscle
What are gap junctions?
Connections between adjacent cells that allow the flow of ions and electrical pulses
What is a chemical synapse?
Calcium concentration gradient at axonal terminal end triggering exocytosis of neurotransmitters
How can Ach have different affects on different receptors?
Metabotropic: Muscarinic receptors leads to hyperpolarization ( increased K+)
Ionotropic receptors: leads to membrane depolarization
What is retrograde and anterograde movement?
Retrograde: movement from axon terminal to the soma
Anterograde: movement from soma towards axon terminal
What does kinesis do?
Carries vesicles from soma to axon ending via ATP
What does dynein do?
Carries recycled vesicles from axon to some via ATP
What negative affect can dynein have?
It can carry viruses from to the neuron nucleus
What does the neural musculojunction include?
The motor endplate + axonal ending
What is the purpose of the post-junctional fold?
To increase the surface area of the sarcolemma
What is the purpose of SNARE proteins?
To mediate transmitter vesicle docking, fusion and release of cytokines
What do v-SNAREs do?
Involved in vesicle binding
What do t-SNAREs do?
Synaptic membrane binding
What are common v-SNAREs?
Synaptobrevin and Synaptotagmin
What are common t-SNAREs?
Syntaxin and SNAP-25
How does Botox B and Tetanus toxin work?
By cleaving synaptobrevin
How does Botox A work?
By cleaving SNAP-25
What is the purpose of synaptotagmin work?
Binds Ca2+ triggering the release of vesicles
Where is synaptobrevin located?
In the vesicle membrane
Where is syntaxin located?
In the pre-synaptic membrane
Where is SNAP-25 located?
In the pre-synaptic membrane
Where is synaptotagmin located?
In the vesicle membrane
What does MEEPs stand for and what is it?
Miniature-endplate potentials; it is the amount of ACh released from one vesicle
How much depolarization does one MEPP amount to?
.4 mV
What is one quanta?
One MEEP/one vesicle release
What do SNARE proteins use for energy?
GTP for fusion
ATP for release
What occurs in Myasthenia Gravis?
Autoreactive antibodies bind to AChR blocking the binding of ACh
What is collapse fusion?
When the vesicle becomes a part of the membrane
What is the clinical significance of myasthenia gravis?
Causes asymmetrical ptosis
What is Lambert-Eaton Syndrome?
Ca2+ channel autoimmune deficiency
What occurs in LE syndrome?
Antibodies attack calcium channels resulting in a reduced number or channels which reduces the amount of neurotransmitter release
