Synapses, Receptors and the Autonomic Nervous System

Question 1

Define synapses

Answer 1

junction between neurons or neurons and another type of cell

Question 2

What occurs at a chemical synapse and in what order?

Answer 2

1. AP arrives at the presynaptic axon terminal
2. Voltage gates Ca+ ion channels open and enter the presynaptic terminal, causing the release of neurotransmitter into the synaptic cleft
3. Neurotransmitter diffuses across the synaptic cleft and combines with a ligand-gated receptor on the postsynaptic cell
4. This binding causes the channels to open and Na+ ions enter and depolarize the postsynaptic membrane
5. If depolarization reaches threshold, an AP is generated in the postsynaptic neuron

Question 3

Why are synapses important?

Answer 3

to have more control over and regular signals

Question 4

What can open/close ligand-gated ion channels?

Answer 4

hormones, second messengers, or neurotransmitter to allow ions to pass

Question 5

Describe what it mean when a ligand gated ion channel is described to be activating? inhibiting?

Answer 5

A ligand gated channel can be activating, depolarizing the membrane and make it easier to fire the AP, or inhibiting, hyperpolarizing the membrane and making it harder to fire the AP. This is determined by the charge of the ion passing through the channel

Question 6

What is the purpose of a G-protein coupled receptor?

Answer 6

Activate the intracellular signaling cascase by GDP phosphorylation into GTP when a neurotransmitter binds a g-protein. Does not transmit APs

Question 7

What does it mean when a G-protein coupled receptor is described as activating? inhibiting?

Answer 7

An activating g-protein activates downstream pathways where as an inhibiting g-protein inhibits downstream pathways

Question 8

Provide an example of a G-protein coupled receptor

Answer 8

Muscarinic receptors that bind ACh or adrenergic receptors that bind epinephrine or norepinephrine

Question 9

Provide a summary of the sympathetic nervous system

Answer 9

Overall function is to mobilize the body for activity, “fight or flight”, most of the physiological effects are due to epinephrine and norepinephrine being released systemically at specific organs

Question 10

Provide a summary of the parasympathetic nervous system

Answer 10

Overall function is restorative and to conserve energy, “rest and digest”, exclusively driven by acetylcholine