1-09 Chemical Events At The Synapse (Part 2)

Front 1

Objective

Identify two kinds of effects that a neurotransmitter can have.

Back 1

1. Ionotropic
When the neurotransmitter binds to a receptor site on the postsynaptic neuron, it causes ion channels to open. For instance, glutamate—an excitatory neurotransmitter—causes sodium channels to open, whereas GABA—an inhibitory neurotransmitter—opens calcium channels.

2. Metabotropic
The binding of a neurotransmitter to a receptor may trigger a series of chemical reactions in the postsynaptic neuron that are slower and that last longer than ionotropic effects. These effects rely on a second messenger that communicates to different areas within the postsynaptic neuron.

Front 2

Objective

Distinguish between the effects of hormones and neurotransmitters.

Back 2

Hormones broadcast a signal more widely throughout the body, whereas neurotransmitters tend to be localized primarily in specific areas of the nervous system.

Front 3

Objective

Compare the role of the anterior and posterior pituitary.

Back 3

The anterior pituitary secretes six hormones that regulate the rest of the endocrine system. These hormones are (the abbreviation of the hormones and the glands they regulate appear in parentheses):

1. adrenocorticotropic hormone (ACTH; adrenal cortex)
2. thyroid-stimulating hormone (TSH; thyroid)
3. prolactin (mammary glands)
4. luteinizing hormone (LH; gonads)
5. follicle-stimulating hormone (FSH; gonads)
6. growth hormone

The posterior pituitary is considered an extension of the hypothalamus. It delivers two hormones synthesized in the hypothalamus—oxytocin and vasopressin—into the bloodstream. Oxytocin regulates an number of sexual and parental behaviors, whereas vasopressin is mostly involved in maintaining water balance in the body.

Front 4

Objective

Give examples of inactivation and reuptake.

Back 4

Inactivation is the breakdown of a molecule by an enzyme. For instance, monoamine oxidase (MAO) breaks down monoamines such as serotonin and dopamine; acetylcholinesterase breaks down acetylcholine.

Reuptake is the recycling of neurotransmitters by the presynaptic neuron so that they can be reused at a later time. There are specific transporter proteins in the membranes of the presynaptic terminal, such as dopamine transporters, that bind to neurotransmitters in the synaptic cleft and draw them back into the terminal.

Front 5

Objective

Describe the relationship of D2 and D4 receptors with personality.

Back 5

Variations in D2 receptor have been linked to severe alcoholism, whereas variations in D4 receptors have been linked to “novelty-seeking” tendencies, which include impulsivity, adventurousness, and a short temper.

Front 6

ionotropic effect

Back 6

Direct effect of a neurotransmitter on the postsynaptic receptors; activates or deactivates ionotropic receptors (ion channels); ionotropic effects begin within one to a few milliseconds and last only about 20 ms

Front 7

metabotropic effect

Back 7

The binding of a neurotransmitter to a receptor may trigger a series of chemical reactions in the postsynaptic neuron that are slower and that last longer than ionotropic effects

Front 8

G-protein

Back 8

Protein that is coupled to guanosine triphosphate (GTP), an energy-storing molecule; the G-protein increases the concentration of the second messenger, such as cyclic AMP, inside the cell

Front 9

second messenger

Back 9

Molecule (e.g. cyclic AMP) that communicates to different areas within the cell. It opens or closes ion channels in the membrane or alters the production of proteins or activates a portion of a chromosome; an ionotropic synapse has effects localized to one point on the membrane, whereas a metabotropic synapse, by way of its second messenger, influences activity in a larger area of the cell and over a longer time.

Front 10

neuromodulator

Back 10

Metabotropic neurotransmitter that does not directly excite or inhibit the postsynaptic cell but increase or decrease the release of other transmitters or alter the response of postsynaptic cells to various inputs

Front 11

hormone

Back 11

Chemical that is secreted, in most cases by a gland but also by other kinds of cells, and conveyed by the blood to other organs, whose activity it influences

Front 12

pituitary gland

Back 12

Structure attached to the hypothalamus, which consists of the anterior pituitary and the posterior pituitary, which release different sets of hormones

Front 13

releasing hormone

Back 13

Hormones secreted by the hypothalamus that flow through the blood to the anterior pituitary and stimulates or inhibits the release of hormones: ACTH, TSH, prolactin, GH, FSH, and LH

Front 14

acetylcholinesterase

Back 14

Enzyme that breaks down acetylcholine into 2 fragments: acetate & choline; the choline diffuses back to the presynaptic neuron, which takes it up and reconnects it with acetate already in the cell to form acetylcholine again

Front 15

reuptake

Back 15

The process by which the presynaptic neuron takes up most of these neurotransmitter molecules and reuses them; this process occurs through transporters

Front 16

transporter

Back 16

Special membrane proteins involved in the reuptake process

Front 17

autoreceptor

Back 17

Receptors that detect the amount of transmitter released and inhibit further synthesis and release after it reaches a certain level