Synapses

Question 0

What are synaptic vesicles?

Answer 0

well characterized organelles that store fast acting neurotransmitters

Question 1

What are synapses?

Answer 1

specialized contact sites between neurons where signals are propagated from one cell to another with fast speed and high spatial precision
- can be neuron to neuron or neuron to muscle

Question 2

What are neurotransmitters?

Answer 2

fast acting, small, non peptide metabolites (though can be slower acting)

Question 3

Why are neurotransmitters not proteins?

Answer 3

small metabolites are faster to synthesize (continuously recycled) ad can rapidly be taken back into pre-synaptic terminal

Question 4

What is the synaptic clef?

Answer 4

active zone of secretion in chemical synapse

Question 5

What is the structure of an electrical synapse?

Answer 5

gap junctions between neurons

Question 6

What is the difference between excitatory or inhibitory synapses?

Answer 6

Excitatory: Glutamate, Ach, amines; ionotropic Na + receptors on post syn terminal; most are located on dendritic spines (covered by glial cells) and usually segregated on diff portion of neuron from inhibitory synapses but not absolute
Inhibitory: GABA and glycine; ionotropic Cl- channels on post syn terminal

Question 7

How do synaptic vesicles trigger an AP?

Answer 7

synchronous release of neurotransmitters triggers AP

Question 8

What is a neuromuscular junction?

Answer 8

specialized synapse that connects a neuron to a muscle cell

Question 9

What is the role of metabotropic receptors and how do they differ from ionotropic receptors?

Answer 9

modulatory function

slow signaling via second messengers

Question 10

What are neuropeptides?

Answer 10

peptide neurotransmitters that are stored in large dense core vesicles and have slow modulatory actions at the synpase
secreted sparingly in response to a long train of effects

Question 11

What are the steps in synaptic transmission?

Answer 11

1) AP travels down axon opening voltage gates Na channels
2) AP invades nerve terminal and opens voltage gated Ca channels, increasing cystolic Ca
3) Ca triggers synaptic vesicle fusion and neurotransmitter secretion
4) a) At excitatory synapses: opening of neurotransmitter gates ion channels (ionotropic receptors) lets cations (mostly Na+) into post synaptic cells and new AP starts
b) At inhibitory synapse: opening of neurotransmitter ion gated channels (ionotropic recepter) permeable to Cl- hyperpolarized post syn terminal and makes cell less excitable

Question 12

How are neurotranmitters loaded into synaptic vesicles?

Answer 12

Synaptic vesicles contain proton (ATPase) pumps that use ATP hydrolysis to pump protons into their lumens; neurotranmitter channels then use the proton gradient across the membrane of the synaptic vesicles to pump neurotransmitter from the cytosol into synaptic vesicles
- plasma membrane transporters on the pre syn terminal aid by reuptaking neurotransmitter from the synp clef to load into synp vesicle

Question 13

What is the role of amphetamines?

Answer 13

let neurotransmitter stay in synaptic clef from longer

Question 14

What are the steps in vesicle fusion?

Answer 14

1) clustering: vesicles cluster near pm
2) tethering : vesicles tether to pm
3) Docking and priming: proteins help dock syn vesicles and prepare for fusion (protein complex binds to Ca channels and synaptobrevin on synaptic vesicle binds SNARE/SM protein complex on PM)
4) Fusion: Ca dissociates clamps and lets zipper function bring the membranes closer so that fusion can occur

Question 15

What are the causes of tetanus and botulism ?

Answer 15

rupture and cleavage of SNARES by clostridial toxins
botulism causes paralysis by cleaving snares associate with motor neurons that stimulate skeletal muscle, thus producing an inhibition of muscle contraction(same target as botox, targeted can regain fn over time)
tetanus causes prolonged muscle contraction by targeting inhibitory synapses that decrease the activity of motor nuerons

Question 16

What is synaptotagmin ?

Answer 16

Ca 2+ sensor that helps trigger fusion by inducing a conformational change

Question 17

What is optogenetics?

Answer 17

the use of genetically encoded light sensitive proteins to monitor and trigger synaptic activity
- can use light to depolarize membranes and control behavior in animal models

Question 18

What are synapse adhesion molecules?

Answer 18

proteins (e.g. cadherins) that connect pre and post synaptic terminal membranes and aid with specificity
- control the formation and stability of synapses

Question 19

What is the role(s) of the complex network of proteins/molecules at dendritic spines?

Answer 19

• clustering and traffic of receptors
• control of synaptic properties
• structural role in the spine shape and size
• synaptic plasticity (function of synapses subject to modulation)
• family of neurological diseases have to do with problems of the cytoskeletal structure that control features of the dendritic spines ( ALS, Epilepsy, Parkinson, Autism (junctional issues), Alzheimer’s, and mental retardation )