Synapse

Question 1

Synapse

Answer 1

specialized junction where the axon terminal contacts with another neuron or cell type. Mediate information and impulse

• CNS synapse examples:
  Axodentritic: axon to dendrite
  Axosomatic: axon to cell body
  Axoaxonic: axon to axon
  Dendrodentritic: dendrite to dendrite

Question 2

NMJ

Answer 2

neuronal muscle junction:
muscle and neuron

Question 3

how many synapses are in a neuron?

Answer 3

1,000 - 10,000

Question 4

what are 2 types of synapses?

Answer 4

1. chemically
2. electrical

Question 5

electrical synapses

Answer 5

• Direct transfer of ionic current from one cell to the next
• Ions can flow bidirectionally
• Cells are electrically coupled
• Speed is very fast
• Common in neuronal cells

Question 6

chemical synapses

Answer 6

Occur between neurons and between neurons and muscle cells

Question 7

what are the steps of releasing a neurotransmitter?

Answer 7

1. Neurotransmitter is synthesized and then stored in
   the vesicles
2. Action potential enters the axon terminal (presynaptic
   terminal)
3. Depolarization of presynaptic terminal causes
   opening of voltage gated Ca++ channels
4. Influx of Ca++ through channels
5. Ca++ activates proteins in the vesicles and active zone
   Activated proteins causes synaptic vesicles to fuse
   with membrane
6. Neurotransmitter is release -> exocytosis
7. Transmitter binds with receptor molecules in
   postsynaptic membrane
8. Opening or closing of postsynaptic channels
9. Postsynaptic causes excitatory or inhibitory
   postsynaptic potential that changes the excitability of
   the postsynaptic cells
10. Retrieval of vesicular membrane from the plasma
    membrane

Question 8

what is the criteria to be a neurotransmitter?

Answer 8

A substance that transmits nerve impulses across the synapse

• Must be present at presynaptic terminal
• Released by depolarization (Ca++ -dependent)
• Specific receptors must be present
• When added extracellular fluid, must mimic the effects of presynaptic stimulation
• A mechanism for removal should exist
• Effects of drugs must block/ mimic the neurotransmitter physiological effects

Question 9

2 classifications of neurotransmitters?

Answer 9

1. excitatory (depolarization)
2. inhibitory (hyperpolarization)

Question 10

Acetylcholine

Answer 10

stimulates muscle contraction, hormone release, in CNS wakefulness, attentiveness, anger, aggression, thirst

Question 11

Glutamate

Answer 11

excitatory neurotransmitter associated with learning and memory

Question 12

Dopamine

Answer 12

Inhibitory neurotransmitter, controlling movement, posture, in CNS, positive reinforcement, dependency

Question 13

GABA

Answer 13

inhibitory neurotransmitter, in CNS, motor control, vision, other cortical

Question 14

Norepinephrine

Answer 14

`attentiveness, emotion, sleepin, dreaming, learning’ also controls fight or flight reactions, heart stimulator vasoconstrictor

Question 15

Serotonin

Answer 15

regulate body temperature, mood, sleep, appetite, pain, depression, impulsive behavior

Question 16

2 major categories of receptors

Answer 16

1. Transmitter (ligand) gated ion channels
2. G-protein coupled receptors

*Ligand binding to the receptors activates G proteins. Serves as a molecular “on-off” switch

Question 17

EPSPs

Answer 17

Excitatory postsynaptic potential

• open up ligand-gated Na+ channels (Na+ comes in)
• Moves resting membrane potential TOWARD threshold (depolarization)

Question 18

IPSPs

Answer 18

Inhibitory postsynaptic potentials

• Open up ligand-gated Cl- channels (Cl- comes in)
• Moves resting membrane potential AWAY from the threshold (hyperpolarization)

Question 19

Temporal summation

Answer 19

if EPSP in pre-synaptic knob are successively repeated without delay so the effect of the previous stimulus is summated to the next

Question 20

Spatial summation

Answer 20

when EPSP is in more than one synaptic knob at the same time

Question 21

Modification of synaptic transmission

Answer 21

• Drugs act by interfering with or stimulating normal process in the neuron involved in neurotransmitter synthesis, storage, and release, and in receptor activation
• Disease can also affect synaptic mechanisms

Question 22

What do you think that can change neurons and their connections?

Answer 22

• accidents
• diseases
• drugs and alcohols

Question 23

A chemical synapse is a…

• Direct connection of channels between cells that allow the flow of neurotransmitters
• Space between neurons that acquire the diffusion of a neurotransmitter to affect the next cell
• Direct connection of channels between cells that allow the flow of ions
• Space between neurons, require the diffusion of ions to affect the next cell

Answer 23

Space between neurons that acquire the diffusion of a neurotransmitter to affect the next cell

Question 24

Arrange the events in the correct sequence when the action potential reaches the terminal knob

a. Influx of Ca++ through channels
b. Transmitter binds to the receptor molecules in postsynaptic membrane
c. Depolarization of presynaptic terminal causes opening of voltage gated Ca++ channels
d. Neurotransmitter is released via exocytosis
e. Action potential enters the axon terminal
f. Ca++ activates proteins in the vesicle and active zone. Activated proteins causes synaptic vesicles to fuse with membrane

Answer 24

E-C-A-F-D-B

Question 25

Excitatory postsynaptic potentials (EPSP) open________

Ligand-gated Na+ channels
ligand -gated K+ channels
Ligand-gated Cl- channels
All of the above

Answer 25

all the above

Question 26

Spatial summation takes place when_______

EPSP is in more that one synaptic knob at the same time
EPSP in pre-synaptic knob are successively repeated without significant delay
both

Answer 26

EPSP is in more that one synaptic knob at the same time

Question 27

Are action potentials and graded potentials the same?

True
False

Answer 27

false