Exam 1 Flashcards
Neuron Doctrine
theorized that brain was composed of individual, highly specialized cells called neurons
parikaryon
soma or cell body
neurites
cellular fibers emerging from the soma (dendrites and axon)
pre-synaptic terminals
contain synaptic vesicles which contain neurochemicals essential for neuronal function (neurotransmitters)
dendrites
neurites of the neuron; there are many and are typically short
axon
neurite of neuron; only 1 but can be long
myelin sheath
protein cover on axon; works as insulating coat
presynaptic ending
synaptic vesicles filled with neurotransmitters in tip of axon
synaptic cleft
fusing of synaptic vesicles’ membrane and nerve ending membrane resulting in release of neurotransmitters into synaptic cleft
synapse
gap between 2 neurons; between presynaptic and postsynaptic ending
postsynaptic ending
uptake of neurotransmitters by receptor sites
neurotransmitter receptors
proteins embedded in membrane of post-synaptic cells that bind neurotransmitters released into synapse
when neurotransmitters bind to neurotransmitter receptors
opens a pore for charged ions to enter or exit the neuron; effectively changes the electrical charge of the post-synaptic neuron
excited
positive ions move in (inside positive)
inhibited
positive ions move out (inside negative)
neurotransmitter re-uptake pumps
specialized proteins embedded in the membrane of the pre-synaptic terminal bind and transport neurotransmitters back into pre-synaptic terminal for breakdown or packaging
example of blocking of neurotransmitter re-uptake pumps
antidepressants block to stop reuptake of serotonin (SSRI’s)
also cocaine :)
unipolar neuron
one neurite (i.e. sensory neuron)
bipolar neuron
two neurites (i.e. interneuron)
multipolar neuron
many neurites (i.e. motor neuron or pyramidal neuron)
Law of Dynamic Polarization
nerve cells are polarized, receiving information on their cell bodies and dendrites and conducting information to distant locations through axons (many exceptions to law)
axo-dendritic connections
synapses; information flows from dendrites to soma to axon
axo-somatic synapses
synapses on cell body
axo-axonic synapses
synapses on beginning of axon
axo-synaptic synapses
pre-synaptic terminal contact with other pre-synaptic terminal
revised Law of Dynamic Polarization
information flows from presynaptic cell to postsynaptic cell with respect to a specific synapse
interneurons
lie between sensory and motor neurons; can be pre or postsynaptic dependent upon synapse in question
neuronal membrane
site of important cellular events that control neuronal function
water
polar molecule and hydrogen bonding among water molecules; slight positive charge on hydrogen and slight negative charge on oxygen
organic molecules
nonpolar and composed of long chains of carbon and hydrogen; not soluble in water
phospholipids
phosphate head attaches to lipid hydrocarbon tail; form a lipid bilayer
hydrophilic
water-loving
hydrophobic
water fearing
amphipathic
having both a hydrophobic and hydrophilic region
synaptic vesicle membrane
water soluble neurotransmitter inside vesicle and water soluble outside in presynaptic terminal
fluid mosaic
hydrophilic channels and pumps that float in neuronal membrane
transcription
production of an RNA copy of DNA occurring in nucleus
mRNA
template for synthesis of proteins
some amino acids…
also function as neurotransmitters
glutamate, aspartate (neuronal excitation); glycine (neuronal inhibition), tyrosine, tryptophan (precursors for classical neurotransmitters like dopamine and serotonin)
translation
assembly of amino acids in specific sequence encoded for by mRNA creating a protein
neurotransmitters
chemical molecules released from neurons that act as chemical signals between neurons
classical neurotransmitters
small chemical molecules
noradrenaline (norepinephrine)
affects attention and responding actions in brain; contracts blood vessels, increasing blood flow (classical)
gaba
calms firing nerves in the central nervous system; high levels improve focus, low levels cause anxiety; contributes to motor control and vision (classical)
dopamine
feelings of pleasure, addiction, movement and motivation; people repeat behaviors that lead to dopamine release (classical)
glutamate
most common; involves in learning and memory; regulates development and creation of nerve contacts (classical)
serotonin
contributes to well-being and happiness; helps sleep cycle and digestive system regulation; affected by exercise and light exposure (classical)
acetylcholine
involved in thought, learning, and memory; activates muscle action in body; also associated with attention and awakening (classical)
peptide neurotransmitters
short peptides (small proteins); often co-transmitters and are released with small chemical neurotransmitters; increases affinity of receptor to bind neurotransmitter; released in brain and used as neurochemical signals between neurons
endorphins
released during exercise, excitement, and sex, producing well-being and euphoria; reduces pain (peptide)
ion channels and pumps
proteins bound to cell membrane of neurons that bind and transport charged ions across cell membranes
metabotropic neurotransmitter receptors
a neurotransmitter receptor linked to a neighboring ion channel by an intracellular signaling molecule; binding activates signaling molecule which opens or closes an ion channel
ionotropic neurotransmitter receptors
neurotransmitter receptor itself is a neurotransmitter-gated ion channel; receptors have a ligand binding site and an ion channel that opens or closes when binding site is occupied by neurotransmitter
ligand
a molecule that binds to another larger molecule
continuum of efficacy
neurotransmitters act by this; rapidly bind to and activate receptors and then are released from and deactivate a neurotransmitter receptor
affinity
how fast and strong a ligand binds a receptor
potency
how biologically effective a ligand is once bound
agonists
ligands that bind to a receptor and activate it biologically; produce a response in a target neuron; high affinity and high potency
antagonists
ligands that bind to a receptor but do not activate it biologically; usually have higher affinity so receptor is blocked from functioning; all exogenous; high affinity but low potency
exogenous
foreign substances
endogenous
substances made in the body
allosteric modifiers
binds to a receptor at a different location than agonists and antagonists; increases ability of receptor to bind a ligand; naturally made or drug
example of allosteric modifier
anti-anxiety meds bind to allosteric site on GABA receptors, binding GABA more strongly to increase calming effect
acetylcholine (ACh)
synthesized in pre-synaptic terminal by enzyme cholineacetyltransferase (ChAT) which fuses acetate (from Acetyl-CoA) and choline together
3 mechanisms terminating post-synaptic ACh activity
desensitization (receptors become less responsive); diffusion of ACh out of synapse; breakdown of transmitter molecule
acetylcholinesterase (AChE)
breaks down acetylcholine
physostigmine
naturally occuring drug that blocks AChE
insecticides
man-made AChE blockers; acetylcholine makes muscles in bugs contract for breathing but insecticide blocks breakdown so their muscles spazz and insect dies
neuromuscular junction
interface between nerve and muscle; connection between a motor neuron and a skeletal muscle cholinergic synapse; uses ACh as a neurotransmitter
gamma-aminobutyric acid (GABA)
produces widespread neural inhibition; derivative of amino acid glutamate; last-minute shut off for action potential
glutamic acid decarboxylase
converts glutamate to GABA by getting rid of carboxyl group
GABA transaminase
recycles GABA back to glutamate for re-uptake and use
GABA A receptors
produces neuronal inhibition; ionotropic and function as Cl- channels; have at least two allosteric binding sites (one for benzodiazepines and one for barbiturates)
benzodiazepines and barbiturates
anti-anxiety meds that increase neural inhibition
presynaptic inhibition
GABA blocks ability of synaptic terminal to release neurotransmitters
GABA receptor blockers
produce excitation and produce seizures in behaving animals
epilepsy
loss of GABA producing neurons
glutamate
chemically similar to GABA, mediates most excitation in brain; majority of glutamate receptors are ionotropic receptors
AMPA
most active glutamate receptor - causes excitation due to increase Na+ influx
Kainate
causes excitation due to increase Na+ influx
NMDA
causes excitation due to increase in Na+ and Ca2+; very important; BIG DADDY
glycine
important amino acid for inhibition, especially in spinal cord where it is used instead of GABA
strychnine
type of poison; glycine antagonist; causes spinal seizures
dopamine and norepinephrine
share core structure of catechol ring group and a nitrogen-containing side group (amine); synthesis starts with tyrosine
serotonin
core structure of an indole ring group and a nitrogen-containing side group (amine; starts with L-Tryptophan)
peptide hormones
released from brain into blood stream to act as neurochemical signals between brain and body
orthograde/anterograde axoplasmic transport
peptide transmitters are synthesized and packaged into vesicles in the cell body and sent down axon to synaptic terminal via this; synthesized as large proteins and chopped up into small pieces by enzymes in vesicle; away from cell body (to neurites)
peptide transmitters after release
diffuse away from synapse or broken down by enzymes
peptide transmitters
considered metabolically expensive (lot of energy needed) so they tend to act at low concentrations for a long period of time
endorphins/enkephalins
family of peptides that act as natural pain killers (endogenous opiates); peptide transmitters
vasopressin and oxytocin
peptides involved in social recognition, aggression, nurturing, affiliation, water retention, milk letdown, maternal instincts - oxytocin in bloodstream for uterine contractions (peptide transmitters)
structural proteins
determine nerve cell shape and movement (actin, tubulin, elastin)
enzymes
catalysts that is a protein
axoplasmic transport
transport of new proteins to distant locations in neurites
retrograde transport
towards cell body (from neurites)
exocytosis
fusion of synaptic vesicle with plasma membrane; synaptic vesicle contents (neurotransmitters) are dumped into synapse
endocytosis
piece of membrane pinches back to form a new vesicle
neuronal growth
neurons send out neural processes; axon growth; exocytosis exceeds endocytosis; axons from one neuron grow and connect with another neuron to form synapses
neuronal pruning
neural processes (axons) withdraw; endocytosis exceeds exocytosis; axons from one neuron withdraw connection with another neuron
mature synapse
stable associations between neurons; exocytosis and endocytosis are precisely balanced
Chemoaffinity Hypothesis
explains how neurites find way during development
chemical signals (trophic factors)
proteins that help nerve cells develop and recognize each other; are exchanged between potential synaptic partners
growth cone
tip of growing neuronal axon; sends out filopodia (finger feet)
withdrawal and approach cycles of neurons
if correct synaptic partner: filopodia flatten out, presynaptic and postsynaptic densities appear
neural adaptation
at mature synpase, concentration of postsynaptic receptors in membrane can be up-regulated or down-regulated based upon amount of neurotransmitter released and received by receptors on postsynaptic cell
problem with down-regulation
desensitization; presynaptic cell increases trophic influence, overwhelms post synaptic cell; postsynaptic cell decreases receptor complement and becomes less sensitive to neurotransmitter presence
problem with up-regulation
denervation supersensitivity; presynaptic cell decreases trophic influence, starves postsynaptic cell; postsynaptic cell increases receptor complement and becomes supersensitive to remaining neurotransmitter around cell
Schwann cells
in PNS; myelinates a single neuronal axon; when axon damaged or severed, Schwann cell forms guidance tube to guide regenerating end of axon to target end of axon
Oligodendrocytes
in CNS; myelinates multiple axons; when axon damaged or severed, oligodendrocytes fail to respond, withdraws remaining myelin support, damage is permanent
