Chapter 3 Flashcards
reflex arc
circuit from sensory neuron to muscle (receptor - cord - back)
temporal summation
repeated weak stimuli over a brief time has cumulative effect (critical to brain function, usually occurs with spatial summation)
presynaptic neuron
relesases neurotransmitters across gap - message delivery
postsynaptic neuron
neurotransmitters bind to receptors in the postsynaptic neuron - message receiver
graded potential
light stimulation producing slight depolarization or hyperpolarization
Excitatory Postsynaptic Potential (EPSP)
graded depolarization from flow of sodium - if threshold is not reached it decays quickly
spatial summation
synaptic inputs from separate locations combine effects on a neuron (critical to brain function, usually occurs with temporal summation)
flexors
muscles that “bring in”
extensors
muscles that “move away”
interneuron
neurons whose axons and dendrites are confined within a given structure
Inhibitory Postsynaptic Potential (IPSP)
temporary hyperpolarization of a membrane - occurs when input selectively opens potassium gates to cell
spontaneous firing rate
rate at which neurons produce action potentials without synaptic input
sequence of chemical events at a synapse
- neurons synthesize neurotransmitters (small in axons, neuropeptides in soma)
- AP travels down axon, @ presynaptic terminal AP allows calcium to enter which releases neurotransmitters from terminals and into synaptic cleft
- molecules diffuse across cleft and bind to receptors, altering activity of post synaptic neurone
- neurotransmitters separate from receptors and diffuse away or be taken back into presynaptic neuron for recycling
- some postsynaptic cells send messages of inhibition to prevent release of more neurotransmitters
neurotransmitter
chemical that affect another neurone - more than 100 known
amino acids
type of neurotransmitter containing an amine group (GABA, glutamate, aspartate, glycine)
monoamine
type of neurotransmitter formed by a change in some amino acids (indoleamines, serotonin, dopamine, catecholamines, dopamine, norepinephrine, epinephrine)
acetylcholine
chemical similar to an amino acid but containing N(CH3)3 group (one member family); controls functions such as memory, attention, sleep, heart rate, and muscular activity.
neuropeptides
chains of amino acids (endorphins, substance P, neuropeptide Y, others)
purines
category of chemicals including adenosine and its derivatives (ATP, adenosine, others); relaxes smooth muscle cells which improves blood flow to tissues
type of neurotransmitter- gases
nitric oxide, maybe others
Synthesis of neurotransmitters
neurons synthesize nearly all transmitters from amino acids which the body obtains from proteins in the diet
cetecholamines
epinephrine, norepinephrine and dopamine - contain a chatechol and an amine group
monoamine oxydase (MAO)
An enzyme that breaks down and thereby inactivates monoamine transmitters such as serotonin, dopamine, and norepinephrine
ionoptropic effects
synaptic effects that depend on the rapid opening of some kind of gate in the membrane - very fast, well suited to visual information that needs to be updated quickly. Most excitatory ionotropic effects use glutamate, most inhibitory use GABA.
transmitter gated/ligand gated
channels opened by a neurotransmitter attaching to a receptor
metabotropic effects
by way of second messenger system, influences activity in much of the cell over a longer period of time - neurotransmitter binds to receptor and bends protein that goes through membrane of the cell. This receptor is attached to a G protein (protein attached to GTP) which releases and takes its energy elsewhere in the cell. (taste, smell, pain, arousal, attention, emotion)
G protein
Protein with guanosine triphosphate attached - energy storing molecule (result of this is increase in second messenger)
Second messenger
A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signal received by a signal receptor protein.
neuropeptides/neuromodulators
synthesized in soma, released and diffused widely by dendrites, axons, and cell bodies (resembling hormones) - release primes other dendrites to release the same neurpopeptide resulting in substantial amounts released (although less often than neurotransmitters). Because they alter gene activity, results are long lasting.
neurogliaform cell
a neuron shaped like a glial cell that releases huge amounts of GABA (a neurotransmitter) all at once forming a “cloud” that spreads to a large number of neurons and produces widespread inhibition (similar to neuropeptide diffusion)
Hormones
chemicals secreted by cells in one part of the body and conveyed by blood to influence other cells
endocrine glands
Glands of the endocrine system that release hormones into the bloodstream hypothalamus pineal gland pituitary gland parathyroid gland thyroid gland thymus liver adrenal gland kidney pancreas ovary placenta testis
protein and peptide hormones
protein - long, peptide - short; composed of chains of amino acids, they attach to membrane receptors and activate a second messenger within cell exactly like metabotropic synapse (many chemicals serve as hormones and neurotransmitters)
pituitary gland
anterior pituitary - glandular tissue, posterior pituitary - neural tissue (considered etension of hypothalamus); attached to hypothalamus where oxytocin and vassopressin are synthesized - these migrate down axons in posterior pituitary and are released into blood. Anterior pituitary produces 6 hormones whose release are controlled by hypothalamus.
releasing hormones
hypothalamus secretes releasing hormones that travel to anterior pituitary to stimulate release of hormones including adrenocorticotropic hormone, TSH, prolactin, somatropin (growth hormone GH), gonadotropins (FSH and LH),
acetylcholinesterase
enzyme that breaks down acetylcholine after release by presynaptic cell. Choline is reabsorbed by presynaptic cell and bound with acetyl groups inside cell to reform acetylcholine
reuptake
A process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane
transporters
Specialized receptors in the presynaptic membrane that recognize transmitter molecules and return them to the presynaptic neuron for reuse; dopamine transporters in caudate nucleus are highly efficient and reuptake accounts for almost all dopamine released
COMT (catechol-o-methyltransferase)
if dopamine released in areas with fewer transporters, this enzyme breaks down the excess into inactive chemicals that cannot stimulate the dopamine receptors
autoreceptors
Receptors that respond to released transmitters and inhibit further synthesis and release
gap junction
In electrical synapses, points that provide cytoplasmic channels from one cell to another with special membrane proteins (pores); membranes of each cell are in direct contact
antagonist
A drug that blocks the effect of a neurotransmitter
agonist
A chemical that mimics or increases the action of a neurotransmitter
affinity
a drug’s tendency to bind with a particular receptor
efficacy
a drug’s tendency to activate a receptor
self-stimulation of the brain
relates to experiment w/ OLDS AND MILNER; rats with electrodes in brain that stimulate certain areas will press a button over and over
nucleus accumbens
A cluster of neurons in the basal ganglia that is a crucial part of the brain’s reward mechanism
dopamine transporter
membrane protein that enables the presynaptic neuron to reabsorb dopamine after releasing it
nicotine
- found in tobacco products
- stimulates acetylcholine receptor, increasing dopamine release in nucleus accumbens
tetrahydracannabinol (THC)
- main active ingredient in cannabis and related substances
- used to treat pain and nausea
- Glaucoma
- increase appetite, altered sensory experience
- purified name “dronabinol”
- excites negative feedback receptors on presynaptic cells that usually respond to anandamide and 2AG
anandamide
One of the natural endocannabinoid chemicals which binds to specific receptors that can also bind to the amdocannabinoids in marijuana
hallucinogenic drugs
distort perception; LSD, mushrooms, peyote; looks like serotonin, stimulates 2A serotonin receptor for longer than normal and at inappropriate times
alcoholism
A disorder that involves long-term, repeated, uncontrolled, compulsive, and excessive use of alcoholic beverages and that impairs the drinker’s health and social relationships.
Type I Alcoholism
Type I Alcoholism develops gradually, usually after age 25; relatives may not always have history of alcohol abuse
Type II Alcoholism
more rapid onset, usually before age 25; affects mostly men with close relatives who have alcohol problems
tolerance
progressive decrease in a person’s responsiveness to a drug
withdrawal
a pattern of uncomfortable or painful physical symptoms and cravings experienced by the user when the level of drug is decreased or the drug is eliminated
antabuse
Disulfiram; medication that blocks the metabolism of alcohol into acetaldehyde, a toxic substance, and is used to help alcoholics refrain from alcohol use
methadone
- a strong opioid agonist
- can be taken orally
- slow reactions so it satisfies the craving but does not produce a rush
- produces less intense withdrawal symptoms than morphine
amphetamines and cocaine
stimulant drugs - increase excitement, alertness and activity while elevating mood and decreasing fatigue; stimulate dopamine synapses in the nucleus accumbens by blocking reuptake
methyphenidate (ritalin)
prescribed for ADHD, blocks reuptake of dopamine in the same way as cocaine at the same brain receptors (differences relate to dose and time course - more gradual)
opiates
chemically similar to or derived from the opium poppy (heroin, morphine, methadone); relaxation, decreased sensitivity to pain by stimulating endorphin receptors (heroin enters brain faster than morphine - produces bigger rush and is more addictive)
MDMA
low dose: stimulant, high dose: sensory distortions; releases dopamine and serotonin, damages axons containing serotonin
2-AG
binds to cannabinoid receptors
alcohol
facilitates response at GABA(a) receptor (main inhibitory site of the brain) and blocks activity at glutamate receptors (main excitatory site); increases stimulation at dopamine receptors in nucleus accumbens
