neuroscience - chapter 9

Question 1

What are the two general types of receptors?

Answer 1

We now know that there are many NTs
Each NT can have many types of receptors Receptors fall into two general categories:
Ionotropic Receptors (allow ions to cross) Metabotropic Receptors (use metabolic pathways)

Question 2

Describe ionotropic receptors

Answer 2

Transmitter binds to the receptor and the pore opens
– (“ligand-gated channels”)
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* Ions pass through the channel
* The electrical response is fast, and short-lived

Question 3

Give an example of a ionotropic receptor

Answer 3

Example: the nicotinic ACh receptor, but most ionotropic receptors are similar (Glutamate-gated receptor is probably a tetramer)
Made of 5 subunits
2 ACh molecules must simultaneously bind to both α subunits

Question 4

Describe the subunits of ionotropic receptors.

Answer 4

Different receptors have slightly different subunits
The different subunits determine which ions pass through
This determines if it is excitatory (Na) or inhibitory (Cl)
-A diagram of the polypeptides that are the different subunits: we can see 4 common areas M1-M4 On the right: the M1-M4 regions of the alpha subunit of ACh receptor in the membrane.

Question 5

Describe metabotropic receptors.

Answer 5

Receptor is linked to a G-protein
– The G-protein activates channels or enzymes indirectly
– Responses are diverse, slower, and longer-lived

Question 6

Name the two different receptors for acetylcholine receptors.

Answer 6

-Nicotinic receptors are ionotropic
-Muscarinic receptors are metabotropic

Question 7

Describe both. (Nicotinic receptors and muscarinic receptors)

Answer 7

Nicotinic receptors are ionotropic
Found in NMJ and in the brain (blocked by curare)
Muscarinic receptors are metabotropic (and there are several sub-types)
Found in smooth muscles (heart, gut) and the brain. Atropine blocks muscarinic receptors (belladonna)

Question 8

What type of receptors does dopamine have?

Answer 8

Dopamine only has metabotropic receptors.

Question 9

Describe dopamine metabotropic receptors.

Answer 9

-Both D1 and D2 receptors activate “2nd messengers”
-D1 activates the enzyme adenylyl cyclase (cAMP increases)
-D2 Inhibits the enzyme adenylyl cyclase (cAMP decreases)
-Antischizophrenics block D2 receptors

-Gi - inhibitory G-protein
-Gs- excitatory G-protein
-There are several subtypes D1 and
D2 “families” D1 and D5 (D1b) are coupled to Gs
-D2 family D3 and D4 coupled to Gi

Question 10

What types of receptors does GABA have?

Answer 10

GABAa is ionotropic and GABAb is metabotropic

Question 11

Talk about GABAa.

Answer 11

-The GABAA Receptor (Ionotropic)
GABA is the most common inhibitory NT
-Cl- passes into the cell
-Many drugs enhance the effect of GABA
-Benzodiazepine (Valium) (Increases frequency)
-Barbiturates (Increases duration)
-Interacts with alcohol (complex effects)
-Neurosteroids