Chapter 12.3 : The Synapse and The Neurotransmitter

Question 1

chemical synapse

Answer 1

neurons communicate by releasing chemicals

Question 2

acetylcholine

Answer 2

the first discovered neurotransmitter

Question 3

takes 0.50 milliseconds for a neurotransmitter to cross the _________

Answer 3

chemical synapse distance

Question 4

A nerve’s action potential can go no further than to the

Answer 4

synaptic knob / distal end of the axon

Question 5

A chemical synapse consist of three components

Answer 5

– Pre-synaptic membrane
– Synaptic cleft
– Post-synaptic membrane

Question 6

When a synapse is between two neurons, the 1st neuron in the signal pathway is called
the _______ ______ / it releases
neurotransmitter. 2nd neuron is the _____ _____ / it has receptors for the neurotransmitter

Answer 6

presynaptic neuron ; postsynaptic neuron

Question 7

Presynaptic neurons have synaptic vesicles with neurotransmitter and postsynaptic have Presynaptic neurons have synaptic vesicles with neurotransmitter and postsynaptic have
receptors with ligand-regulated ion channels_____ with ligand-regulated ion channels

Answer 7

receptors

Question 8

spinal cord motor neuron soma have about _______ from other neurons

Answer 8

10,000 unique synaptic knobs

• 8,000 ending on its dendrites
• 2,000 ending on its soma

Question 9

Cerebellum’s soma may have as many as _______ synapses

Answer 9

100,000

Question 10

synaptic knob stores _______ ______ containing neurotransmitters

Answer 10

synaptic vesicles

Question 11

synaptic vesicles are docked on ___________ of the __________ / ready to release neurotransmitter on demand

Answer 11

release sites ; plasma membrane

Question 12

postsynaptic neuron receptors function as _____________________

Answer 12

ligand-regulated ion gates

Question 13

The presynaptic neuron may synapse with

Answer 13

• Dendrite
• Soma
• Axon of postsynaptic neuron

Question 14

The presynaptic neuron form different types of synapses

Answer 14

• Axodendritic synapses
• Axosomatic synapses
• Axoaxonic synapses

Question 15

Gap junctions can be thought of as a type of synapse which

Answer 15

allows action potentials to move rapidly between adjacent cells

Question 16

Gap junctions join ___________ /// ions diffuse through
the gap junctions from one cell to the next

Answer 16

adjacent cells

Question 17

Advantage

Answer 17

quick transmission // no delay for release and binding of neurotransmitter // cardiac and smooth muscle, embryonic cells, and some neurons

Question 18

Disadvantage

Answer 18

they cannot integrate information and make decisions

Question 19

Two Types of Neurotransmitter Receptors

Answer 19

Ionotropic receptors and metabotropic receptors

Question 20

Ionotropic receptors

Answer 20

– Ligand binds to integral protein channels which allows either cation or anion to cross plasma membrane
– Ligand receptor and ion channel are part of same protein
– If cations enter cell then it depolarizes / if anions enter cell then it hyperpolarizes

Question 21

Metabotropic receptors

Answer 21

– ligand receptor and ion channel have different types of integral proteins
– metabotropic receptors are “ligand receptors” on external face of membrane that releases “G protein” on their internal face of membrane
– G protein travels to a second integral protein and this intergral protein then functions as the ion channel
– this is Second messenger sytem

Question 22

Synaptic delay. How long it take for the complex sequence of
events to occur

Answer 22

time from the arrival of a signal at the axon terminal of a presynaptic cell to the beginning of an action potential in the
postsynaptic cell
– 0.5 msec for all the complex sequence of
events to occur

Question 23

What are neurotransmitters synthesized by?

Answer 23

in soma and transported down axon of presynaptic neuron

Question 24

How do neurotransmitters alter the the post-synaptic membrane?

Answer 24

Neurotransmitter moves resting membrane potential towards threshold or away from threshold

Question 25

often, it is the _______ and not the ________ that will dictate the outcome

Answer 25

receptor ; neurotransmitter

Question 26

One type of neurotransmitters may may have different effect on different __________ throughout the body

Answer 26

target tissue

Question 27

There are multiple receptors that exist for each ______________

Answer 27

neurotransmitter

Question 28

It is the ______ that determines the effect of the neurotransmitter on the target cell

Answer 28

receptor

Question 29

Ionotropic receptors are always

Answer 29

stimulatory

Question 30

Metabotropic acetylcholine receptors can be

Answer 30

either stimulatory or inhibitory // depends on downstream effect of the second integral protein which is activated by the G protein

Question 31

the same molecule in different ________ may function as a _______, a _________, or a ___________

Answer 31

mechanisms ; hormone ; neurotransmitter ; neuromodulator

Question 32

more than ___ neurotransmitters have been identified

Answer 32

100

Question 33

major neurotransmitter categories according to chemical composition : Monoamines' subcategory Catecholamines

Answer 33

Epinephrine, Norepinephrine, and Dopamine

Question 34

major neurotransmitter categories according to chemical composition : Monoamines' subcategory Indoamines

Answer 34

histamine and serotonin

Question 35

major neurotransmitter categories according to chemical composition : Ace_______

Answer 35

tylcholine

Question 36

major neurotransmitter categories according to chemical composition : Amino acids

Answer 36

GABA, Glycine, Aspartic acid, Glutamic acid.

Question 37

major neurotransmitter categories according to chemical composition : Neuropeptides

Answer 37

Enkephalin, Substance P, Cholecystokinin, and ß-endorphin

Question 38

Monoamines (AKA __________)

Answer 38

Biogenic Amines synthesized from amino acids by removal of the –COOH group // retaining the –NH2 (amino) group

Question 39

___ and ______ bind to monamine receptors

Answer 39

LSD ; mescaline

Question 40

Neuropeptides types

Answer 40

substance P, endorphins, enkephalins (i.e. endogenous opioids) /// this class also include gutbrain peptides (produced my non-neural tissue but have receptors in the brain)

Question 41

Pruines

Answer 41

adenosine triphosphate (ATP) / now recognized as major neurotransmitter in CNS and PNS

Question 42

adenosine triphosphate (ATP) / now recognized as major neurotransmitter in ________

Answer 42

CNS and PNS

Question 43

Gases & Lipids

Answer 43

nitric oxide (NO) & carbon monoxide // activate guanylyl cyclase / function in brain / hydrogen sulfide // (note: NO causes smooth muscle to dialate)

Question 44

Endocannabinoids

Answer 44

(or simply cannabinoids) // brain neurotransmitter / tetrahydrocannabiol (THC) interacts with the endocannabinoid receptors

Question 45

Neuropeptides

Answer 45

* chains of 2 to 40 amino acids * act at lower concentrations than other neurotransmitters * longer lasting effects * stored in axon terminal as larger secretory granules (called dense-core vesicles)

Question 46

Some neuropeptides also released from digestive tract /// Note: _______ cause food cravings

Answer 46

gut-brain peptides

Question 47

Neurotransmitters are diverse in their _____

Answer 47

action

Question 48

Ionotropic receptors are simply

Answer 48

ion channels

Question 49

Metabotropic receptors are __________________ // provide varible __________ outcomes

Answer 49

second messenger systems ; downstream

Question 50

each synapse will use a different type of _________ and ____________________

Answer 50

neurotransmitter ; post synaptic receptor

Question 51

three different types of synapses

Answer 51

– excitatory cholinergic synapse (ionotropic) – inhibitory GABA-ergic synapse (ionotropic) – excitatory adrenergic synapse (metabotropic)

Question 52

excitatory cholinergic synapse is

Answer 52

(ionotropic)

Question 53

inhibitory GABA-ergic synapse is

Answer 53

(ionotropic)

Question 54

excitatory adrenergic synapse is

Answer 54

(metabotropic)

Question 55

metabotropic

Answer 55

second messenger system receptor) /// this maybe either inhibitory or excitatory

Question 56

cholinergic synapse

Answer 56

employs acetylcholine (ACh) as its neurotransmitter – ACh excites some (most!) postsynaptic cells (e.g. skeletal muscle – may inhibits others (e.g. cardiocytes at AV n44ode)

Question 57

Describing the excitatory action

Answer 57

– nerve signal approaching the synapse // opens the voltage-regulated calcium gates at junction between axon and synaptic knob – Ca2+ enters the knob // triggers exocytosis of synaptic vesicles releasing Ach – empty vesicles drop back into the cytoplasm to be refilled with Ach – reserve pool of synaptic vesicles move to the active sites and release their Ach – ACh diffuses across the synaptic cleft – nerve signal approaching the synapse // opens the voltage-regulated calcium gates at junction between axon and synaptic knob – Ca2+ enters the knob // triggers exocytosis of synaptic vesicles releasing Ach – empty vesicles drop back into the cytoplasm to be refilled with Ach – reserve pool of synaptic vesicles move to the active sites and release their Ach – ACh diffuses across the synaptic cleft

Question 58

Inhibitory GABA-ergic Synapse

Answer 58

* GABA-ergic synapse employs - aminobutyric acid as its neurotransmitter * nerve signal triggers release of GABA into synaptic cleft * GABA receptors are chloride channels /// ionotropic receptor type * Cl- enters cell and makes the inside more negative than the resting membrane potential /// move away from threshold! * postsynaptic neuron is inhibited * less likely to fire

Question 59

GABA receptors are ________ ________ /// ionotropic receptor type

Answer 59

chloride channels

Question 60

Adrenergic synapse employs the neurotransmitter _____________ also called noradrenaline

Answer 60

norepinephrine (NE)

Question 61

The receptor on post synaptic membrane for the adrenergic synapses is type __________

Answer 61

metabotropic – not an ion gate but second messenger system – a transmembrane protein associated with a G protein (i.e. metabotropic receptor)

Question 62

NE , monoamines, and neuropeptides acts through NE , monoamines and neuropeptides acts through ________________

Answer 62

second messenger systems