Chapter 3 - Synapses and Synaptic Transmission

Question 1

presynaptic terminal

Answer 1

located at the end of the axon

• projection specialized for the release of chemicals to the postsynaptic terminals
• contains neurotransmitters

Question 2

Synaptic communication sequence

Answer 2

1) action potential arrives at the presynaptic terminal
2) membrane of the presynaptic terminal depolarizes, opening voltage-gated calcium channels
3) influx of Ca into neuron terminal combined with liberation of Ca from intracellular stores triggers the movement of the synaptic vesicles
4) synaptic vesicles fuse with the membrane, releasing neurotransmitters into the cleft
5) neurotransmitter diffuses across the cleft
6) neurotransmitter contacts and binds with receptor on the postsynaptic membrane
7) receptor changes shape by:
a) opens an ion channel
b) activates intracellular messengers

Question 3

postsynaptic potentials

Answer 3

local changes in ion concentration across the postsynaptic membrane

Question 4

Neurotransmitters

Answer 4

effect of the neurotransmitter is based on the receptor it binds(inhibitory or excitatory)
- determined by the nature of the post-synaptic receptor

Question 5

Ligand-gated receptors

Answer 5

binding of neurotransmitter opens channels for action potential
- faster response, short duration

Question 6

G-protein activated receptors

Answer 6

2nd messenger

• binds to membrane and then 2nd messenger begins cascade of response
• slower response, longer duration

Question 7

Action at the Synapse

Answer 7

1) action potential arrives at the presynaptic terminal
2) membrane depolarizes
3) Ca in the nerve terminal
- Ca channels open -> into
- vesicles migrate to presynaptic terminal and releases neurotransmitter
4) neurotransmitter diffuses across
5) shape of membrane changes

Question 8

EPSP

Answer 8

Excitatory postsynaptic potential

• local potential
• neurotransmitter binds to receptor and opens Na+ channels causing action potential(depolarization)
• if binds to neuromuscular junction = muscle contraction

Question 9

IPSP

Answer 9

Inhibitory postsynaptic potential

• local potential
• hyperpolarization K+ channels open making it more negative making less possible for action potential

Question 10

Facilitation

Answer 10

axoaxonic synapse

• if excitatory from presynaptic terminal = more neurotransmitter released
  
  • therefore more effect on postsynaptic terminal
• more Ca into presynaptic terminal

Question 11

Inhibition

Answer 11

axoaxonic synapse

• if inhibitory from presynaptic terminal = less neurotransmitter
  - therefore less effect on postsynaptic terminal
• less Ca into presynaptic terminal

Question 12

Cholinergic Neurotransmitters

Answer 12

Acetylcholine(ACh)

• post ganglionic parasympathetic
• preganglionic parasympathetics and sympathetics
• in autonomic nervous system
• excitatory

Question 13

Muscarinic receptors

Answer 13

activated by muscarine

• a poison from a mushroom
• cholinergic

Question 14

Nicotinic receptors

Answer 14

activated by nicotine

- cholinergic

Question 15

Amino acid transmitter substance

Answer 15

GABA = inhibits
Glutamate = excitatory
Glycine = primarily in spinal cord(inhibitory)

Question 16

Amines

Answer 16

Dopamine(DA)
Epinephrine(adrenaline)
Histamine
Norepinephrine(NE)
Serotonin(5-HT)

Question 17

Dopamine(DA)

Answer 17

excitatory or inhibiting

• low levels = Parkinson’s
• schizophrenia = give drugs to interfere with dopamine
  - possibly have too much dopamine causing disease)

Question 18

Epinephrine(adrenaline)

Answer 18

not a big effect on nervous system

Question 19

Histamine

Answer 19

concentrated in hypothalamus

- inhibitory

Question 20

Norepinephrine(NE)

Answer 20

sleep/wake cycle and alertness

• in locus cerelius
• neurons for postganglionic parasympathetic system

Question 21

Serotonin(5-HT)

Answer 21

regulation of mood

• for raphe nuclei in brain stem
• descending pain control system
• decreased serotonin = depression

Question 22

Neuroactive peptides

Answer 22

endorphins
enkephalins
substance P

Question 23

Endorphins

Answer 23

powerful analgesic(feel better)

• everywhere
• opium releases endorphins
• runner’s high(exercise)

Question 24

Enkephalins

Answer 24

located in dorsal gray horn(sensory)

• can suppress painful stimuli
• similar to endorphins

Question 25

Substance P

Answer 25

excitatory

Question 26

Agonist

Answer 26

can mimic the effects of a neurotransmitter

Question 27

antagonist

Answer 27

blocks the release of a neurotransmitter or binds to a receptor to prevent neurotransmitter from binding
- Ex: blocks ACh binding

Question 28

Skeletal muscle contraction

Answer 28

1) action potential arrives
2) nerve secretes acetylcholine into the synaptic cleft
3) ACh binds to receptors on muscle membrane that opens the ion channels
4) action potential depolarizes the muscle and travels along the T tubules
5) reaches the sarcoplasmic reticulum and causes the myofibrils to release calcium
6) calcium initiates attraction of actin and myosin causing them to slide together
7) get shortening of sarcomeres
8) muscle contraction would continue as long as calcium remains in the area

Question 29

Myasthenia Gravis

Answer 29

autoimmune disorder

• body creates antibodies against ACh receptors
  - ACh is released and binds wherever possible
  - with repeated contractions of muscle, continuously gets weaker
  - eyelids droopy, along with facial muscles
  - proximal weakness sometims