0331 Transmission between cells and the neuromuscular Junction Flashcards
• There are chemical and electrical synapses for communication between a neuron and another cell • Chemical synaptic transmission is mediated by neurotransmitter: – often produced in the presynaptic terminal – released in the synaptic cleft in a Ca2+ dependant manor, and – binds to postsynaptic receptors – Degraded/reuptaken and recycled • NT receptor activation results in the opening of channels that depolarise or hyperpolarise the postsynaptic membrane, thereby altering its excitabil
What are the two types of synapses that allow communication between a neuron and another cell
Chemical and Electrical synapses
What is the difference between electrical and chemical synapses
Electrical synapses are allow flow of ions between 2 cell membranes via gap junctions. They are a direct link between the cytoplasm of adjacent cells. Chemical synapses allow communication between excitable cells. They occur via a complex mechanism involving neurotransmitters, Ca+, ligand receptors and enzymes
Where are neurotransmitters produced?
In the cell body (ER and golgi for peptide NT) and the presynaptic terminal (non-peptide NT)
Where are neurotransmitters released and what moelculeregulates this release
Neurotransmitters are released from their vesicles in the synaptic cleft. This release is regulated by CA + (calcium).
What do neurotransmitters released into the synaptic cleft bind to
Neurotransmitters released into the synaptic cleft bind to postsynaptic receptors (ionotropic and metabotropic)
What are the3 ways neurotransmitters can be inactivated
Re-uptake into presynaptic terminal, degradation and diffusion.
Neurotransmitters released into the synaptic cleft can be reabsorbed into the synaptic terminal via Na dependant transport . Neurotransmitters can also be degraded in the synaptic cleft before they reach ligand receptors in the postsynaptic membrane via breakdown by enzymes
Explain in a few key sentences how an action potential may be generated via neurotransmitter release
Ca+ signals the release of a quart (amount of neurotransmitter in a vesicle) NT into synaptic cleft. NT binds to specific ligand receptors which cause opening of ion channels in the postsynaptic membrane. Channel activation causes depolarisation of the postsynaptic membrane which excites an action potential
What is a neuromuscular junction
A neuromuscular junction is a specialised synapse that connects the nervous system to the muscular system. The postsynaptic membrane has post junctional folds. NMJ is a excitatory synapes. Vesicles release Acetyl Choline as neurotransmitters.
Where do electrical synapses between 2 cell membranes occur
Electrical synapses can occur in glial cells and neurons (but also smooth muscles, cardiac muscles)
What is a vesicle
A small fluid filled vacuole from within a body
What are gap junctions
Gap junctions are specialized intercellular connections between 2 adjacent cells made of channels.
What transporters regulate Ca2+ release into the presynaptic cleft
Voltage gated Ca2+ channels
What is the role of Ca2+ in a chemical synapse?
Intracellular Ca2+ causes synaptic vesicle fusion with the presynaptic membrane. This fusion releases the contents of vesicles into the synaptic cleft
Where are vesicles proteins synthesized in the neuron and where are they processed and sorted?
Vesicles proteins are synthesized in the rough endoplasmic reticulum and pass through the golgi apparatus network for processing (non-peptide)
What is the role of the fast axonal transport microtubule system?
Transport of vesicles from the cell body to pre-synaptic cleft
