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EXAM #2 Study Set
antagonists
Chemicals that hinder a neurotransmitter from functioning.
Haloperidol is a __ for dopamine
graded potentials
This is not an all-or-none polarity change like an action potential but has levels of strength that can ultimately influence the production of an action potential.
axon hillock
Place where the axon meets the cell body.
action potential
A temporary reversal of membrane polarity caused by voltage-gated ion channels reaching their threshold. This localized polarity change travels down the axon away from the cell body.
synaptic cleft
A tiny space between the terminal bouton on the presynaptic cell and the postsynaptic cell.
calcium (Ca++)
a positively charged ion that has a higher concentration in extracellular fluid
entering a neuron at the synapse facilitates exocytosis of neurotransmitters.
summation
The combined influences of EPSPs and IPSPs that determine the rate of action potentials.
monoamine oxidase inhibitors (MAOIs)
antidepressants that inhibit enzymes that break apart monoamines.
sodium-potassium pump
A process of pulling three Na+ ions out of the neuron for every two K+ ions that are pumped in.
requires ATP for energy.
ionotropic receptor
A neurotransmitter receptor that opens ion channels directly.
ion channels
Large proteins in the neuron membrane that selectively permit the flow of specific ions into and out of a neuron.
neurotransmitters
Chemical messengers released from vesicles in presynaptic cells that act as keys fitting into receptors on postsynaptic cells.
glutamate
most common excitatory neurotransmitter.
receptors are kainite, NMDA and AMPA.
chemically gated
An ion channel that opens and closes by a chemical such as a neurotransmitter.
epinephrine (EPI)
An excitatory neurotransmitter in higher concentrations in the peripheral nervous system.
monoamines
A class of neurotransmitters created from a single amino acid.
Dopamine, norepinephrine, epinephrine, histamines, and serotonin are all monoamines
ligand
Any chemical that binds to a receptor, including neurotransmitters, hormones, and certain drugs and chemicals.
glycine
Less common inhibitory neurotransmitter.
mostly found in spinal cord
connectomics
A new branch of neuroscience focused on mapping the brain using connections between neurons.
excitatory postsynaptic potential (EPSP)
When a postsynaptic neuron depolarizes, increasing the likelihood of an action potential.
neuropeptides
Small neurotransmitters that work in conjunction with other neurotransmitters.
serve a number of functions beyond signaling other neurons: gene expression, the activity of glial cells, blood flow, and pain perception.
temporal summation
additive influence on action potentials of EPSPs or IPSPs occurring in rapid succession around the same time
serotonin (5-HT)
An excitatory and inhibitory neurotransmitter
functions: mood, sleep, hunger, and pain.
dendritic spines
Small protuberances that are along the dendrites.
meet terminal boutons of axons from other neurons to form a synapse.
axon initial segment (AIS)
segment of an axon just past the axon hillock where an electrical signal (action potential) begins.
electrical synapse
connection between two cells where they are physically connected, and cytoplasm can flow between gap junctions.
axoplasmic transport
process by which vesicles are moved down the axon along microtubules.
chloride (Cl-)
a negatively charged ion
has a higher concentration in extracellular fluid.
If it enters the cell, it causes hyperpolarization.
axosomatic
When an axon from one neuron communicates with the soma (cell body) of another neuron.
relative refractory period
When the membrane potential is hyperpolarized, making a new action potential difficult but not impossible to generate.
axodendritic
When an axon from one neuron communicates with the dendrite of another neuron.
absolute refractory period
Between 1–2 msec after an action potential starts, when another action potential cannot be generated.
saltatory conduction
In a myelinated axon, it is the bouncing of action potentials from one node of Ranvier to the next, increasing the speed of the action potential propagating down the axon.
excitation
When a neurotransmitter increases the likelihood of an action potential on the postsynaptic neuron.
Example: Glutamate
agonists
Chemicals that help a neurotransmitter function.
Example: SSRI's
threshold potential
A specific membrane polarity that opens voltage-gated ion channels.
inhibitory postsynaptic potential (IPSP)
When a postsynaptic neuron hyperpolarizes or is prevented from depolarizing, decreasing the likelihood of an action potential
reuptake
A process where neurotransmitters are removed from the synaptic cleft and taken back into the presynaptic cell for repackaging into vesicles.
neuron membrane
surrounding of a neuron made of two layers of lipids and large proteins.
selectively permeable to molecules and ions.
potassium (K+)
positively charged ion.
is in a higher concentration in the intracellular fluid
responsible for repolarization when exiting neurons.
resting potential
difference in millivolts comparing the inside and outside of a neuron:
a neuron is negative (-70mV) on the inside compared to the outside.
inhibition
When a neurotransmitter reduces the likelihood of an action potential on the post-synaptic neuron
Example: GABA
repolarization
process where the polarity of a neuron is restored, caused by K+ channels opening and K+ leaving the neuron.
exocytosis
release of neurotransmitters when a vesicle fuses with the membrane of a terminal bouton.
This process is initiated by Ca++ caused by depolarization opening Ca++ channels
spatial summation
additive influence on action potentials of EPSPs and IPSPs generated at different locations on the neuron.
voltage-gated
An ion channel that opens and closes when the membrane around it reaches a specific polarity.
endogenous opioids
A type of neuropeptide that is involved in pain perception and sexual activity.
endorphins
metabotropic receptor
A neurotransmitter receptor that affects an ion channel through a second messenger system.
2nd Messenger: G-Protein
norepinephrine (NE)
An excitatory neurotransmitter in higher concentration in the central nervous system.
created from dopamine
involved in arousal, attention, + fight-or-flight response
synapse
place where two neurons communicate with one another.
gap junctions
In an electrical synapse, the place where two neurons are attached to one another to allow the flow of molecules and ions between them through connexons.
hyperpolarization
An increase in polarity of a neuron from the resting potential.
reduces the likelihood of an action potential.
b/c of continuous movement of K+ out of neuron
resting potential foes from -70mV to -74mV
connexon
An assembly of six proteins embedded in a neuron membrane that forms a pore.
two neurons connect to form a large channel between them.
chemical synapse
A type of synapse where the terminal bouton of one neuron communicates with another neuron, but the neurons do not touch.
sodium (Na+)
a positively charged ion.
higher concentration in extracellular fluid and causes depolarization when entering a neuron.
connectome
map of the connections between neurons of an animal.
GABA (gamma-aminobutyric acid)
Most common inhibitory neurotransmitter.
Agonists: Alcohol + benzodiazepines (ex. Xanax)
Agonists can prevent seizures —> addictive
depolarization
reduction of membrane potential of a neuron caused by Na+ channels opening and Na+ enters the neuron.
membrane becomes less polarized
axoaxonic
When an axon from one neuron communicates with the axon of another neuron.
acetylcholine (ACh)
A common excitatory neurotransmitter throughout the brain and body.
works at the neuromuscular junction.
histamines
Neurotransmitters found in the hypothalamus
Functions: allergic reactions, arousal, and attention.
Antagonist: Antihistamines
dopamine (DA)
An excitatory or inhibitory neurotransmitter
functions: motivation, addiction, and motor movements.
all-or-none law
Rule that once an action potential starts, it does not stop or diminish in strength.
Auto receptors
receptor molecule located on the presynaptic
neuron that responds to the neurotransmitter
released by the presynaptic neuron.
Regulate release + synthesis of NTs
serve to inhibit activity of NT
Up-Regulation
Increase in the # of receptor sites b/c of too little NTs in synaptic cleft
drugs reduce NTs release + # of receptors literally increase at postsynaptic cleft
Down-Regulation
Less receptors are available b/c there are too many NTs in synaptic cleft
drugs increase NT release + # of postsynaptic receptors decreases
Glial Cells
Neuron support cells
Functions: holds neuron in place, supply nutrients (sugar) + O2, insulate w/myelin, remove dead neurons, remove neuro toxins + protect neurons from diseases
Astrocytes
Provides nutrients from vascular system, repair damaged nervous tissue, protect blood-brain barrier
star shaped found in CNS
important in neuronal comm. + memory
replicate easily —> lead cause for brain tumors
Dysfunction: neurodegenerative disorders: Huntingtons, ALZ, ALS
Oligodendrocytes
Create myelin, move around brain looking to help
found in CNS
Microglia
Destroy pathogens tht get through blood-brain barrier, clear damaged/unused neurons (pruning)
smallest glial cells
important in development
over productive pruning in schizophrenia + autism
Schwann Cells
Wraps myelin around portions of one axon
functions same as other glial cells
found in PNS
Multipolar Neurons
Has one axon leaving cell body w/several axon collaterals toward terminal ends + several dendrites
most common
Bipolar Neurons
found in retina + olfactory system + hearing
has one branching axon and only one dendrite
Unipolar Neurons
Contains axon that is splits into two branches
found in spinal cord
simplest for pain + touch
Sensory/Afferent Neurons
Brings info from sensory organs to brain
Motor/Efferent Neurons
Relays info from CNS to muscles
Reflexes***
Vesicles
Balloon-Like structures tht hold + release NTs
neural firing drives them to synapse + they release NTs
