Ch.5, Synapses

Question 1

ACh effect on mammals and frogs

Answer 1

mammals: decreases heart rate, activates VOLUNTARY skeletal muscles in the somatic nervous system, can excite or inhibit organs in the autonomic nervous system; HOWEVER, its effect depends on the receptor site not just the neurotransmitter
frogs: same thing

Question 2

NE

Answer 2

norepinephrine: raises heart rate in mammals

Question 3

EP/ adrenaline

Answer 3

same thing, raises heart rate in frogs

Question 4

Otto Lowei

Answer 4

discovered neurotransmitter ACh in frog hearts, first discovered in the ANS

Question 5

Features of a Chemical Synapse (x)

Answer 5

ASYMMETRICAL LOOK, pre and post look very different
-Unidirectional info flow: MUST specify pre and post-synaptic
-Pre = efferent, sending
-Post= afferent, receiving
separated by synaptic cleft
-has slight delay on communication, not simultaneous or immediate
-Converts chemical signal (neurotransmitter) into electrical signal (change in membrane potential) (transduction)

Question 6

Features of an electrical synapse

Answer 6

SYMMETRICAL LOOK

-info flow is bidirectional: NO NEED TO SPECIFY PRE AND POST
-Seperated by gap junctions: act as hydrophilic channels that allow metabolites to pass/mostly polar molecules (nucleotides, sugars, amino acids)
-instantaneous: in the heart and hypothalamus (for hormone release) where neurons must work completely in sync for function
includes glial cells/tripartite synapse

Question 7

Microtubule of the chemical synapse

Answer 7

tracks that transport substances to the axon terminal

Question 8

Synaptic vesicle of the chemical synapse

Answer 8

round granules that contain neurotransmitter

Question 9

Storage granule

Answer 9

large compartment that holds synaptic vesicles

Question 10

Postsynaptic receptor vs post-synaptic membrane vs presynaptic membrane

Answer 10

1. presynaptic membrane: has molecules that transmit chemical messages
2. postsynaptic membrane: contains receptor molecules that receive chemical messages
3. Postsynpatic receptor: site to which a neurotransmitter molecule binds

Question 11

Synaptic cleft

Answer 11

small space separating presynaptic terminal and post-synaptic dendritic spine

Question 12

Advantages of chemical vs electrical synapses

Answer 12

Chemical: flexibility, learning memory, plasticity
Electrical: instantaneous allows for synchronization of large population of neurons

Question 13

Importance of synapses

Answer 13

1. learning, memory, plasticity
2. sites of drug action: drugs work either by inhibiting or exciting a response
3. neuronal communication
4. sites of neurological disorders, like neurodevelopmental or neurodegenerative (ADHD, alzheimers, autism, depression, schizophrenia)

Question 14

Why does alcohol work as a depressant?

Answer 14

it excites GABA in the brain, which is a depressant: therefore has a depressant effect

Question 15

5 steps of anterograde synaptic neurotransmission in order

Answer 15

anterograde: forward moving, going from pre to post
S-P-R-R-I
1. Synthesis: neuortransmitter is made or sent to neuron.
2. Packaging and storage: neurotransmitter is stored into vesicles to await the arrival of an action potential.
3. Release through exocytosis once threshhold is reached
4. Receptor action: binds to site and activates
5. Inactivation: don’t want to constantly excite the cell

Question 16

Process of exocytosis in neurotransmission

Answer 16

action potential arriving at the terminal allows vesicles to bind to the membrane, fuse to it, and release neurotransmitter

Question 17

8 types of synapses

Answer 17

Axodendritic: axon synapsing onto dendrite
Axoaxonic: axon terminal ends on another axon
Axosomatic: axon terminal ends on a cell body b
Axosecretory: hormone release, directly into capillaries
Axoextracellular: axon to somewhere outside the cell
Axosynaptic: axon terminal ends on another terminal
Axomuscular: motor neurons sending to muscle cells
Dendrodentric: dendrite sending to another dendrite

Question 18

Connexin, connexon/hemichannels: what they are and where they they are

Answer 18

Connexin: 1 of the proteins needed to make a hemichannel
Connexon/hemichannel: 6 connexins joined to make a hemichannel

Question 19

Major structural identifying feature of electrical synapses

Answer 19

fused pre and post-synaptic membranes: cytoplasm of two neurons is directly in contact

Question 20

How does the structure of inhibitory and excitatory synapses differ?

Answer 20

Excitatory: wider cleft, rounder vesicles, dense material on membranes (greater postsynaptic density)
Inhibitory: narrower cleft, flatter vesicles, sparse material on membranes (less postsynaptic density)

Question 21

Post-synaptic density

Answer 21

an electron-dense structure located at the postsynaptic membrane of excitatory synapses, containing a high concentration of scaffolding and signaling proteins.

Question 22

Why are inhibitory synapses located closer to the cell body?

Answer 22

“open the gates” idea, want it to be close so the cell doesn’t keep getting excited: otherwise this will likely lead to rundown of the cell/seizures
any synapse located closer to the initial segment =more effect on initial segment

Question 23

four criteria of neurotransmitters

Answer 23

RAMS
-Synthesis: neurotransmitter must be made in neuron or sent to it
-Release: its release must cause a response in the target cell
-same receptor action must be obtained when done experimentally
Mechanism to inactive

Question 24

EPSPs and IPSps

Answer 24

decay rapidly over time, both forms of graded potentials

Question 25

Why do cytoplasms need to be fused in electrical synapses

Answer 25

Bc the exchange of ions is directly between cells, vs in chemical synapses they communicate using chemical proxies