Synapses

Question 1

what are the 3 different kinds of synapses?

Answer 1

-Axon + cell body (Axosomatic)
-Axon + dendrite (axodendritic)
-Axon + axon (axo-axonic)

Question 2

What happens in depolarization?

Answer 2

1. The action potential triggers voltage gated Na+ channels to open
2. Na+ rushes in, inside of axon becomes less negative and reaches threshold
3. voltage gated Ca+ channels open, Ca+ moves in (down its concentration gradient)
4. Ca+ triggers synaptic vesicles with neurotransmitters in it to fuse with membrane and release neurotransmitter into synaptic cleft
5. below threshold Ca+ channels close, Ca+ pumps will now pump Ca+ out (using energy)

Question 3

where are voltage gated Na+ channels? voltage gated Ca+ channels?

Answer 3

Voltage gated Na+ channels traverse whole axon, but Ca+ channels are only on the tip

Question 4

_________ are channels where ligand binds to protein, it opens and lets an ion through

Answer 4

Ionotropic channel (ligand- gated channel)

Question 5

Ionotropic channels are _____, while metabotropic channels are _____

Answer 5

fast, slow

Question 6

______ are channels where ligand binds and there is a signaling cascade in the cell

Answer 6

Metabotropic channel (usually GPCR)

Question 7

can ligands have both metabotropic or ionotropic effect ?

Answer 7

YES: GABA-a: binds to ionotropic, but GABA-B binds to metabotropic

Question 8

____________ is the enzyme that catalyzes the creation of Ach

Answer 8

Choline acetylase/Choline acetyltransferase

Question 9

________ is the enzyme that breaks down Ach

Answer 9

Acetylcholinesterase (ACE)

Question 10

where are the degradative enzymes usually located?

Answer 10

post-synaptic cell

Question 11

what is end-plate potential?

Answer 11

when Ach binds to ligand gated channels on muscle fiber → channels open → Na rushes in → graded potential (graded potential in muscle fiber)

Question 12

contrast neuron-muscle junction and neuron-neuron junction

Answer 12

• Neuron-Muscle junction:
  Large area for neurotransmitters
  LARGE depolarization
  ~60mV change
  Graded potential

-Neuron-Neuron junction:
has small area
depolarization is small
only 1mV change

Question 13

Ach channel is a ________ cation channel

Answer 13

monovalent

Question 14

what determines the direction of monovalent cations through the Ach channel?

Answer 14

Concentration gradient
Charge difference

Question 15

More Na+ ______ neuron, More K+ _____ neuron bc Na+/K+ pump

Answer 15

outside, inside

Question 16

At rest _____ driving force is much greater than ____

Answer 16

Na+
K+

Question 17

(-) DF for (+) ion = going ____ cell

Answer 17

INTO

Question 18

(+) DF for (+) ion = going ____ of cell

Answer 18

OUT

Question 19

________ has ligand gated channels that bind Ach and allow Na+ to enter

Answer 19

End plate region

Question 20

what are the steps at end plate regions?

Answer 20

Ach binds to Ach ligand gated channel → Na+ goes in at end plate region → Na+ diffuses and causes depolarization within the muscle fiber → if you reach threshold outside end plate, voltage gated Na+ channels open → AP fires → muscle fiber contracts

Question 21

Normal threshold = _____ depolarization from rest, but graded potentials are usually _____mV

Answer 21

~15mV
~60mV

Question 22

why is graded potential so much higher than threshold?

Answer 22

it Exceeds threshold dramatically to ensure that the muscle fires

Question 23

________ blocks degradation of AcH

Answer 23

Eserine
- causes Ach concentration to increase

Question 24

_______ blocks Ach ligand gated channels

Answer 24

Curare
- will never reach threshold since ACH cant trigger channels

Question 25

Neuron-neuron synapses can be _______, but neuron-muscle synapses are ALWAYS _____

Answer 25

inhibitory or excitatory
ALWAYS excitatory

Question 26

where are small neurotransmitters assembled?

Answer 26

in the terminal

Question 27

where are large neurotransmitters assembled?

Answer 27

in cell body but then transported down axon for release

Question 28

what are some examples of large neurotransmitters and what are their functions?

Answer 28

Endorphins and Enkephalin (natural painkillers)

Question 29

Inhibiting degradative enzymes → _______ neurotransmitters concentration

Answer 29

INCREASES

Question 30

____ = degradative enzyme on presynaptic neuron

Answer 30

MAO

Question 31

____ = degradative enzyme on post-synaptic cell

Answer 31

COMT

Question 32

What are the 3 ways to deal with Neurotransmitters?

Answer 32

Reuptake
Diffuse away into interstitial fluid
Degradation

Question 33

which ways are used to get rid of small vs large neurotransmitters?

Answer 33

LARGE: diffusion, degradation
SMALL: reuptake, diffusion, degradation

Question 34

what is IPSP? what can cause this?

Answer 34

• input on post-synaptic neuron that reduces likelihood of AP firing
  -K+ rushes out → more negative → farther from threshold
  -Cl- channel opens → Cl- rushes in → more negative → farther from threshold

Question 35

what is EPSP? what can cause this?

Answer 35

-input on post-synaptic that increases likelihood of AP firing
-Na+ rushes in → more positive → closer to threshold
- is a graded potential

Question 36

when can a depolarizing IPSP happen?

Answer 36

just depends on the driving forces and equilibrium potentials; driving force can switch
EX: Cl- below Equilibrium potential causes depolarization, but once it hits Eq. potential it causes mV to decrease
** look on summary, its confusing**