Chapter 5 (Neurotransmitters and hormones)

Question 1

5 steps of neurotransmission

Answer 1

Step 1 and 2 : Synthesis and storage - They are derived in 2 general ways :

• Synthesized in the axon terminal (building blocks from food pumped into cell via transporters)
• Synthesized in the cell body (according to instructions contained in the DNA)

Step 3 : Release of the neurotransmitter (at terminal, action potential opens voltage-sensitive calcium Ca++ channels, it enters terminal and binds to protein calmodulin forming a complex)

Step 4 : Activation of Receptor Sites (after being released, neurotransmitter diffuses across the synapse and activates receptors on postsynaptic membrane, transmitter-activated receptors : ionotropic or metabotropic receptors, autoreceptors : on presynaptic membrane, quantum : small amount of neurotransmitter in vesicle to produce effect

Step 5 : Deactivation of neurotransmitter (4 different ways : diffusion, degradation, reuptake, taken up by neighbouring glial cells)

Question 2

How do you get a neurotransmitter? It must be?

Answer 2

Neurotransmitter must be :

1. Synthesized and stored in the axon terminal
2. Packaged and stored within vesicles at axon terminal
3. Transported to presynaptic membrane and released in response to action potential
4. Able to activate receptors on target cell membrane located on postsynaptic membrane
5. Inactivated, degraded or removed so does not continue to interact with receptor and work indefinitely

Question 3

Type 1 and Type 2 Synapses

Answer 3

Type 1 : Excitatory, typically located on dendrites, large active zone, dense material on membranes

Type 2 : Inhibitory, typically located on cell body, small active zone, sparse material on membranes

Question 4

Classification of neurotransmitter (small molecules)

Answer 4

Small molecule : quick-acting neurotransmitters, synthesized in axon terminal from dietary nutrients and packaged ready for use in axon terminals (amines : Dopamine (DA), Norepinephrine (NE) and Serotonin (5-HT)

Question 5

Ionotropic receptors

Answer 5

Embedded membrane protein with 2 parts (binding site for neurotransmitter, pore that regulates ion flow to directly and rapidly change membrane voltage, allows movement of ions such as Na+ K+ and Ca2+ across membrane)

Question 6

Metabotropic receptors

Answer 6

Embedded membrane protein with binding site for neurotransmitter but NO pore, indirectly produces change in nearby ion channels or in cell’s metabolic activity, linked to G-protein that can affect other receptors or act with second messengers to affect other cellular processes)

Question 7

Activating System

Answer 7

In CNS, neural pathways that coordinate brain activity through a single neurotransmitter, 4 power supplies to the brain, cell bodies located in a nucleus in brainstem and axons distributed through a wide region of the brain (ex. Alzheimer’s, Schizophrenia is related to dopamine & many positive symptoms, this can also impact movement with someone that has Parkinson’s, serotonin = mood, OCD)

Question 8

Alzheimer’s

Answer 8

Degenerative brain disorder, appears as progressive memory loss and later develops into most common cause of generalized dementia

Question 9

Hormones

Answer 9

Hormones are in all receptors of the brain and can affect almost every neuron in the brain
important = receptors all brains, hypothalamus in charge and controls aspects of behaviour, goes hypothalamus - pituitary gland - endocrine glands - organs and tissues, posterior pituitary = carries hormone into bloodstream where they affect other regions or body, anterior pituitary = stimulates production and secretion of hormones, stress response = cortex (responds by producing steroid hormones for normal body function), medulla (thinner portion, specialized par of SNS), HPA Axis : adrenal cortices produce stress hormones = cortisol