Synaptic transmission Flashcards
What is a synapse?
Transmission of electric nerve impulses between two nerve cells or neuron and effector
Name 2 chemical messengers
Hormones and Neurotransmitters
What are the 2 types of synapses, which one is more rare?
Electrical and chemical, electrical is rarer.
Where are gap junctions most common?
Heart and smooth muscle
Where can chemical synapses exist?
From neuron to neuron and neuron to effector
Three types of Synapses?
Axosomatic, axodendritic, axoaxonal synapses.
What are the 6 steps of the generation of a synaptic response?
- AP conduction to the terminal
- Calcium enters the picture
- Vesicles are released
- Chemical messenger binds
- The chemical messenger moves on
Name 3 ways neurotransmitter effect is terminated
Reuptake via astrocytes or axon terminal.
Degradation via enzymes.
Diffusion away from synaptic cleft.
Name 2 ways molecules enter and exit a cell, what is required for it to happen?
Endocytosis and Exocytosis. ATP is required.
What determines how much neurotransmitter is released?
Higher frequencies of impulses.
How would the amount of neurotransmitter released affect the size of the graded potential?
Larger the amount of neurotransmitter, larger the graded potential.
Which neurotransmitter is being released and which post synaptic receptor is activated is also important. Why?
The RMP can go up and down in a post synaptic cell.
Synaptic transmission can be?
Excitatory or inhibitory
Specialised types of synapses?
Excitatory Postsynaptic potential.
Inhibitory postsynaptic potential
What types of summation is there?
No summation
Temporal summation
Spatial summation.
What happens when both an EPSP and an IPSP are received?
They will almost completely cancel each other out.
What is a neural circuit?
A functional group of neurons which process a special kind of information
What are the 3 types of neuronal circuits?
- Diverging circuit
- Converging circuit
- Reverberating circuit
What is the neuromuscular junction?
When a motor neuron meets a skeletal muscle
Which neurotransmitter binds to the receptor on the sarcolemma?
Acetylcholine (ACh)
Describe phase 1 of the events at the neuromuscular junction.
- Action potential arrives at axon terminal at neuromuscular junction.
- Ach released, binds to receptors on sarcolemma.
- Ion permeability of Sarcolemma changes
- Local change in membrane voltage occurs.
- Local depolarization (End-plate potential) ignites action potential in sarcolemma.
Describe phase 2 of the events at the neuromuscular junction
- AP travels across the entire sarcolemma.
- AP travels along t-tubules.
- SR releases Ca2+ which binds to troponin, myosin binding sites on actin become exposed.
- Myosin head binds to actin, contraction begins.
What breaks down Ach after performing its function?
Acetylcholine esterase.
What would happen in the absence of ACh-esterase?
The muscle would stay contracted
How do inhibitory synapses assist our physiology?
The patellar reflex
What is reciprocal inhibition?
When efferent impulses of alpha motor neurons to antagonist muscles are reduced
What is Myasthenia Gravis?
Autoimmune disease in which Ach receptors in the neuromuscular junction are destroyed, sufferers have Ach receptor anti-bodies.
What are some symptoms of Myasthenia Gravis?
Muscle fatigue, Ptosis, Diplopia, difficulty chewing and swallowing, respiratory problems, myasthenia crisis causing respiratory arrest.
What are some treatment options for Myasthenia Gravis?
ACh-esterase inhibitors
What is Curare Poisoning?
Prevents ACh binding post synaptically, causes flaccid paralysis of skeletal muscle.
How is Curare used in medicine?
Previously used in conjunction with general anasthesia.
What do organophosphates do? How do you treat it?
inhibit ACh esterase. Cause contraction of pupils and convulsions, twitching and jerking through effects at neuromuscular junction. Atropine (ACh receptor blocker).
What does botulism do? How can you treat it?
Prevents release of ACh, causes flaccid paralysis of muscles. Can be fatal, cause muscle weakness. Antitoxin, ventilator, stomach pump, surgery. Infants don’t have immunity to prevent infection if ingested, therefore any child under 1 shouldn’t be given honey.
