PSY454 - Chapter 2
How do antidepressants work?
block reuptake of serotonin and norepinephrine
Irreversible ACE inhibitors
cells stop firing. You get muscle spasms and end up with cardiac arrest.
Which process will most likely result in an IPSP?
chloride ions entering the cell
Acetylcholine is synthesized from ______.
choline found in milk, eggs, and nuts
Reversible ACE inhibitors
cognitive enhancers used to treat Alzheimers disease
Dopamine pathway of Hypothalamus to pituitary gland
controls hormones
Dopamine pathway of substantia nigra to the basal ganglia
controls motor coordination
A hormone is a chemical that is ______.
conveyed by the blood to other organs, whose activity it influences
How are neurotransmitters synthesized?
diet -> proteins in blood stream -> neuron (precursors)
Depolarization is to ______, as hyperpolarization is to ______.
excitation; inhibition
Acetylcholine
facilitates the opening of sodium channels (causing depolarization)
Anterior pituitary is to ______, as posterior pituitary is to ______.
glandular tissue; neural tissue
Inhibitory synapses on a neuron ______.
hyperpolarize the postsynaptic cell
Metabotropic receptors
initiate a secondary signal or messenger inside the neuron by releasing a G-protein which bends and releases these proteins inside the cell. Takes longer time and has longer-lasting results Examples: taste, smell, pain
An advantage of nitric oxide is that ______.
it can be made by neurons efficiently
Hypothalamus
maintains a fairly constant circulating of hormones through a negative feedback system
Presynaptic neuron
neuron that delivers synaptic transmission
Postsynaptic neuron
neuron that receives messages
Acetylcholine
neurotransmitter involved in memory and stimulates movement. Involved in peripheral actions (cardiac)
Endorphins
neurotransmitter involved in pain relief
What provides the building blocks for synthesizing all neurotransmitters?
proteins found in the diet
Temporal summation is most likely to occur with ______.
rapid succession of sub threshold of excitation
What is the proper ordering of a reflex arc?
sensory neuron, interneuron, motor neuron
What ion gates in the membrane open during EPSP? What gates open during IPSP?
sodium; potassium or chloride
Transporters
special membrane proteins that facilitate reuptake
Specialized junctions between neurons are called ______.
synapses
Inhibitory postsynaptic potential (IPSP)
temporary hyperpolarization of the cell membrane. This occurs when synaptic input selectively opens the gate for positively charged potassium ions to leave the sell or negatively charged chloride ions to enter the cell
Glutamate
the primary excitatory transmitter (causing depolarization) -comes from the metabolic pathway -involved in epilepsy
What are the sequence of chemical events that occur at the synapse?
-Neurotransmitters are synthesized by precursors in the cell body or axon. -Action potentials travel down the axon, opening calcium channels causing calcium ions to come into the cell. -This causes the synaptic vesicles to fuse with the cell membrane, which causes the release of those molecules to diffuse across the cleft, attach to receptors, and alter the activity of the postsynaptic neuron. -The neurotransmitter molecules separate from the receptors. -Neurotransmitters may be taken back into the presynaptic neuron fro recycling or diffuse away and be metabolized by enzymes
What are the three ways to terminate synaptic transmission?
1. Metabolism 2. Reuptake 3. Autoreception
Three important points about reflexes:
1. Reflexes are slower than conduction along an axon. 2. Several weak stimuli present at slightly different times or slightly different locations produce a stronger reflex than a single stimulus.
How does negative feedback work?
1. receptors detect the amount of transmitter released and inhibit further synthesis release 2. Postsynaptic neurons respond to stimulation by releasing chemicals that travel back to the presynaptic terminal where they inhibit further release
Inotropic receptors
Act instantaneously and open ion channels. Glutamate, acetylcholine, GABA Examples: vision and hearing
Adrenocorticotropic hormone (ACTH) controls secretions of the ______.
Adrenal cortex
Agonists vs. Antagonists
Agonists = boosts efficacy of a particular neurotransmitter Antagonists = reduce the efficacy of a particular neurotransmitter
"Secondary messangers" carry their messengers to ______.
Areas within the postsynaptic cell.
What are second messengers, and what type of synapse relies on them?
At metabotropic synapses, the neurotransmitter attaches to its receptor and thereby releases a chemical (second messenger) within the postsynaptic cell, which alters metabolism or gene expression of the postsynaptic cell.
What is binding?
Attachment of a neurotransmitter to a receptor
How do cannabinoids work?
Bind to 2-AG receptors on presynaptic neurons or GABA. Then, the presynaptic sell stops sending messages.
How do opiate drugs work?
Bind to the same receptors of endorphins
Reuptake is an alternative to which other process?
Breaking down neurotransmitters via an enzymatic process.
What causes synaptic vessels to fuse with the terminal membrane?
Calcium
When the action potential reaches the presynaptic terminal, which ion must enter the presynaptic terminal to release the neurotransmitter?
Calcium
How do cannabinoids affect neurons?
Cannabinoids released by the postsynaptic neuron attach to receptors on presynaptic neurons, where they inhibit further release of both glutamate and GABA.
How do hallucinogens work?
Chemically resemble serotonin and stimulate serotonin type 2A receptors at inappropriate times or for longer duration than usual to distort perception
Hormones
Chemicals secreted by a gland or other cells that is transported to other organs by the blood where it alters activity. Produced by endocrine glands Important for long-lasting changes in multiple body parts
The primary difference between an EPSP and an action potential is that ______.
EPSPs are sub threshold events that decay over time and space.
How to EPSPs and IPSPs relate to the spontaneous firing rate?
EPSPs increase the number of action potentials above the spontaneous firing rate; IPSPs decrease the number of action potentials below the spontaneous firing rate
How do proteins in the diet come together?
Enzymes. DNA and RNA
True or False: generally speaking, a neuron will release a greater number of neurotransmitters than what it will respond to with its own receptors.
False
Why are neurotransmitters stored in vesicles?
For concentration and protection. functions in exocytosis, allows them to release neurotransmitters quickly
Excitatory Postsynaptic Potentials (EPSP)
Graded potential that decays over time and space. Cumulative effect of EPSPs are the basis for both temporal and spatial summation
What evidence led Sherrington to conclude that transmission at the synapse is different from transmission along an axon?
He found that the velocity of conduction through a reflex arc was slower than the velocity of an action potential along an axon. Therefore, some delay must occur at the junction between one neuron and the next.
What are the masters of the endocrine system?
Hypothalamus and pituitary gland
What does a highly active brain area do to increase its blood supply?
In a highly active brain area, many stimulated neurons relate nitric oxide, which dilates the blood vessels in the area and thereby increases blood flow to the area.
Vesicles are located ______.
In presynaptic terminals
GABA
Inhibitory neurotransmitter that allows chloride ions to enter the cell.
G-protein
Initiates a second signal (messenger) inside a neuron -increases concentration of of a "second-messenger" -second messenger communicates to areas within the cell -may open or close ion channels, after production of activating proteins or chromosomes
How do inotropic and metabotropic synapses differ in speed and duration of effects?
Inotropic synapses act ore quickly and more briefly
The "spontaneous firing rate" of a neuron refers to ______.
Its rate of producing action potentials even when it is not stimulated
Neuropeptides
Metabotropic effects utilize a number of different neurotransmitters -Release requires repeated stimulation; trigger neurons to release the same neuropeptide
What happens to serotonin and catecholamine molecules after they stimulate a postsynaptic receptor?
Most are reabsorbed by the presynaptic terminal. Some of their molecules are broken down into inactive chemicals, which then diffuse away.
In what way is a neuropeptide intermediate between neurotransmitters and hormones?
Most neurotransmitters are released in small amounts close to other receptors. Neuropeptides are released into the brain in larger amounts or not at all. When released, they diffuse more widely. Hormones are released into the blood for diffuse delivery throughout the body.
Norepinephrine
Neurotransmitter involved in arousal and mood Important for functioning of sympathetic nervous system
Dopamine
Neurotransmitter involved in control of movement and our sensations of pleasure and reward
Serotonin
Neurotransmitter involved in regulation of mood, sleep, wake patterns, and appetite
How doe nicotine work?
Nicotine stimulates acetylcholine receptors
Can an inhibitory message flow along an axon?
No. Only action potentials propagate along an axon. Inhibitory messages—IPSPs—decay over time and distance.
An action potential causes the release of neurotransmitters by ______.
Opening calcium pores in the membrane
Which part of the pituitary—anterior or posterior—is neural tissue, similar to the hypothalamus? Which part is glandular tissue and produces hormones that control the secretions by other endocrine organs?
Posterior; anterior
What is autoception?
Postsynaptic cells send reverse messages (release retrograde transmitters) to slow the release of further neurotransmitters
Reuptake
Presynaptic neuron takes up most of the neurotransmitter molecules intact and reuses them
A drug that inhibits the action of the enzyme acetylcholinesterase will have the effect of ______.
Prolonging the action of acetylcholine at its synapses
Dopamine's mesolimbocortical pathway
Reward pathway
Tryptophan serves as a precursor for ______.
Serotonin.
What is Sherrington's evidence for inhibition in the nervous system?
Sherrington found that a reflex that stimulates a flexor muscle prevents contraction of the extensor muscles of the same limb. He therefore inferred that an interneuron that excited motor neurons connected to the flexor muscle also inhibited the input to the extensor muscle
What is the primary difference between temporal summation and spatial summation?
Spatial summation depends on contributions from more than one sensory neuron.
Why is methylphenidate generally less disruptive to behavior than cocaine is despite the drugs' similar mechanisms?
The effects of a methylphenidate pill develop and decline much more slowly than the effects of cocaine.
Pituitary Gland
The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.
exocytosis
The release of substances from a cell. Vesicles fuse with presynaptic membrane and release transmitters into the synapse
How do benzodiazepines work?
They are a GABA agonist and bind to that receptor
What do dopamine, norepinephrine, and epinephrine share in common?
They are all synthesized from the same amino acids. They are all catecholamine neurotransmitters
How are neuropeptides special compared to other neurotransmitters?
They are released only after prolonged stimulation, but when they are released, they are released in large amounts by all parts of the neuron. Neuropeptides diffuse widely, producing long-lasting effects of many neurons
How do amphetamine and cocaine influence dopamine synapses?
They interfere with reuptake of released dopamine
How do stimulant drugs work?
They stimulate dopamine synapses by increasing the release of dopamine from the presynaptic terminal AND block reuptake of dopamine
True or False: Most of the brain's excitatory inotropic synapses use the neurotransmitter glutamate.
True
True or False: Temporal and spatial summation ordinarily occur together
True
NMDA
Type of receptor site for Glutamate that is difficult to stimulate, and often requires AMPA to first hypo-polarize cell -Involved in memory formation -Make connections weaker or stronger between neurons
The presynaptic terminal stores high concentrations of molecules in ______.
Vesicles
Autoreceptors monitor the ______.
amount of neurotransmitter released
Catecholamines
are stored in vesicles