Synapses

Question 1

What determines the function of a chemical synapse?

Answer 1

the receptor, not the neurotransmitter

Question 2

What do chemical synapses involve?

Answer 2

neurotransmitters that are released into the presynaptic cell and bind receptors to excite, inhibit, or modify post synaptic cells

Question 3

How many NTs have been identified?

Answer 3

over 100

Question 4

What is the largest known neurotransmitter-receptor family?

Answer 4

serotonin receptor subtypes

Question 5

What are the presynaptic events that occur within the presynaptic neuron?

Answer 5

1. action potential arrives at the synaptic terminal causes membrane depolarization
2. VG Ca2+ channels open
3. Ca2+ enters the synaptic terminal
4. exocytosis of vesicles filled with NT

Question 6

What dictates the amount of NT released from the presynaptic cell?

Answer 6

the amount of Ca2+ that enters

Question 7

What is a synaptic delay?

Answer 7

the amount of time it takes between pre-synaptic depolarization and post-synaptic response

Question 8

How does synaptic delay alter?

Answer 8

the more complex the reflex, the more synaptic delay

Question 9

What causes the synaptic delay?

Answer 9

due to the time for calcium entry for exocytosis, presynaptic NT release, diffusion in the synaptic cleft, and post synaptic receptor activation

Question 10

What are the two classifications of NT?

Answer 10

small molecules and neuropeptides

Question 11

What are characteristics of small molecule NT?

Answer 11

-rapidly acting
-elicit acute responses

Question 12

What are some examples of small molecule NTs?

Answer 12

acetylcholine, norepinephrine, dopamine, serotonin, histamine, glycine, GABA, glutamate, and nitric oxide

Question 13

What are characteristics of neuropeptides?

Answer 13

larger molecules
-slower
-effects are slower, more potent, and more prolonged
-fewer neuropeptides produced and release

Question 14

What are some examples of neuropeptides?

Answer 14

LH, ACTH, GH, vasopressin, oxytocin, angiotenison II, and substance P

Question 15

What is substance P associated with?

Answer 15

inflammation and pain pathway

Question 16

What are the three ways to terminate the NT action?

Answer 16

-re-uptake of NT by the pre-synaptic membrane
-inactivation of NT by the enzymes in the synapse
-diffusion of NT away from the synapse

Question 17

What are ionotropic receptors?

Answer 17

receptors on the post synaptic cell that directly affect ion channels

Question 18

What can the binding of NT on an ionotropic receptor cause?

Answer 18

-changes in cell membrane potential
-stimulate muscle contraction and/or relaxation
-stimulate secretion
-act as a second messenger to alter cellular activity

Question 19

What are metabotropic receptors?

Answer 19

G protein coupled receptors on post synaptic cells

Question 20

What causes EPSPs?

Answer 20

-opening of Na+ or Ca2+ channels
-closing of K+ or Cl- channels

Question 21

What causes IPSPs?

Answer 21

-opening of Cl- channels
-increased in K+ conductance
-closing of Na+ or Ca2+ channels

Question 22

Is only one graded potential needed for an action potential?

Answer 22

no, usually the summation of GPs are needed to make an AP

Question 23

What are the two types of summation?

Answer 23

-spatial
-temporal

Question 24

What is spatial summation?

Answer 24

when there are simultaneous EPSPs or IPSPs form multiple presynaptic neuron onto one post synaptic neuron

Question 25

What is temporal summation?

Answer 25

successive EPSPs or IPSPs from a single presynaptic nerve terminal

Question 26

What can cause a change in excitability of a neuron?

Answer 26

-synaptic input -prolonged activation -changes in membrane permeability, ion concentration, and other chemicals

Question 27

What type of response of glutamate cause?

Answer 27

excitatory response

Question 28

What type of response does GABA cause?

Answer 28

inhibitory response

Question 29

What does an axo-axonal inhibitory signal cause?

Answer 29

causes less Ca2+ to enter the synaptic cleft and decreases the amount of NT released which causes a smaller EPSP

Question 30

What does an axo-axonal facilitation signal cause?

Answer 30

cause more Ca2+ to enter the synaptic cleft and increase the amount of NT released which causes a larger EPSP

Question 31

What is synaptic fatigue?

Answer 31

when each successive stimulus is identical, but the response is progressively smaller -due to a presynaptic change

Question 32

What is long term potentiation?

Answer 32

enhanced stimulation on the post-synaptic neuron after a brief period of rapidly repeated stimulation of presynaptic neuron -becomes easier to cause an action potential

Question 33

What is long term depression?

Answer 33

the opposite of LTP -decreases the synaptic strength

Question 34

What can cause increased excitability of a neuron?

Answer 34

-hyperkalemia (up to 6 mM) -hypocalcemia -alkalosis -caffeine and theophylline -upregulation of receptors

Question 35

What can cause decreased excitability of a neuron?

Answer 35

-hyperkalemia (above 6 mM) -hypokalemia -hypercalcemia -acidosis -anesthetics -down regulation of receptors -hypoxia -fatigue