Lecture 4 Flashcards
difference in electrical charge between the inside and the outside of a cell
membrane potential
membrane potential is measured with the use of _______
microelectrodes
resting membrane potential is measured as about _____
-70 mV charge
neuron state of resting membrane potential
polarized
membrane potential of a polarized neuron
not 0
in resting neurons, there are more _____ ions outside the cell while there are more ____ ions inside the cell
- Na+ ions
- K+ ions
specialized pores in the neural membrane
ion channels
2 types of pressure
- electrostatic pressure
- pressure from random motion
transporter discovered by Alan Hodgkin and Andrew Huxley in the 1950s
sodium-potassium pumps
disturbance of the resting membrane potential
postsynaptic potentials (PSPs)
2 effects when neurotransmitters are released
- depolarize of receptive membrane
- hyperpolarize of receptive membrane
decreasing the resting membrane potential
depolarize of receptive membrane
increasing the resting membrane potential
hyperpolarize of receptive membrane
this depolarization is an upward deflection on the oscilloscope
postsynaptic depolarization
other term for postsynaptic depolarization
excitatory postsynaptic potentials (ESPs)
postsynaptic depolarization ___ the likelihood that the neuron will fire
increase
this hyperpolarization is a downward deflection on the oscilloscope
postsynaptic hyperpolarization
postsynaptic hyperpolarization is also called
inhibitory postsynaptic potentials
postsynaptic hyperpolarization ____ the likelihood that the neuron will fire
derease
ESPs and ISPs are all ____
PSPs
ESPs and ISPs are ______, meaning the amplitudes of PSPs are proportional to the intensity of the signals that elicit them
(e.g., weak signals elicit small PSPs, and strong signals elicit large ones)
graded potential
important characteristics of transmission of PSPs
- it is rapid
- is is decremental
determines whether a neuron fires
- net effect of synapsis activity
- balance between excitatory and inhibitory signals
a massive but momentary—lasting for 1 millisecond—reversal of the membrane potential from about −70 to about +50 mV.
action potential
action potential are _____ responses
all-or-none
what does “all-or-none” responses mean
they either occur to their full extent or do not occur at all
summation of postsynaptic potentials
- spatial summation
- temporal summation
summation occurs when EPSPs and IPSPs from different locations on neurons make their way to the axon initial segment and summate there
spatial summation
occurs when EPSPs and IPSPs from a single location on a neuron make their way to the axon initial segment and summate there
temporal summation
3 possible combinations under spatial summation
- 2 EPSPs summated to produce a greater EPSP
- 2 IPSPs summated to produce a greater IPSP
- 1 EPSP and 1 IPSP cancel each other out
conduction of action potentials
- ionic basis
- refractory periods
- axonal conduction
- the hodgkin-huxley model in perspective
an action potential is brought on by momentary variations in the permeability of the membrane for diffusible ions from the perspective of ions
ionic basis
(refractory period) period during which it is possible to fire the neuron again but only by applying higher-than normal levels of stimulation
relative refractory period
[refractory period wherein] there is a brief period of about 1 to 2 milliseconds after the initiation of an AP during which it is impossible to elicit a second AP; followed by the relative refractory period
absolute refractory period
responsible for two important characteristics of neural activity
refractory periods
2 important characteristics of neural activity:
- responsible for the normal travel of Als along axons in one direction
- responsible for the relationship between neural firing rate and the intensity of the stimulation
2 important ways of how AP conduction along an axon differs from PSP conduction
- Al conduction is non-decremental
- APs are conducted more slowly than PSPs
an action potential will be generated and will
travel along the axon back to the cell body, given that the electrical stimulation of sufficient intensity is applied to the terminal end of an axon
antidromic conduction
axonal conduction in the natural direction from cell body to terminal buttons
orthodromic conduction
transmission of action potentials in myelinated actions
saltatory conduction
provided a simple, effective introduction to what we now understand about the general ways in which neurons conduct signals
Hodgkin-Huxley model
synaptic transmission: from electrical signals to ______ signals
chemical
synapses of axon terminal buttons on dendrites
axodendritic synapses
small nodules on dendrite surfaces where many axodendritic synapses terminate
dendritic spines
synaptic arrangement examples:
- axodendritic synapses
- axosomatic synapses
- dendrodendritic synapses
- axoaxonic synapses
most common synaptic arrangements
- axodendritic synapses
- axosomatic synapses
synapses at which the site of release is at some distance from the site of reception
nondirected synapses
with close proximity between the site of neurotransmitter release and receptors
directed synapses
mediate presynaptic facilitation and inhibition
axoaxonic synapses
large neurotransmitters are called ______
neuropeptides
neuropeptides are ______ composed of between 3 and 36 amino acids
short amino acid chains
they are short proteins
neuropeptides
concept in neuron which states that many neurons can contain two neurotransmitters
co-existence
process of neurotransmitter release
exocytosis
proteins with specific binding sites for particular neurotransmitters
receptors
any molecule that binds to another
ligand
subtypes of receptors
- ionotropic receptors
- metabotropic receptors
(receptor subtype) ligand-activated ion channels
ionotropic receptors
(receptor subtype) associated with signal proteins and G proteins
metabotropic receptors
metabotropic receptors with two unconventional traits
autoreceptors
two unconventional traits of autoreceptors
- bind to their neuron’s own neurotransmitter molecules
- found on the presynaptic membrane rather than the postsynaptic one
2 mechanisms preventing the clogging of synapse
- reuptake by transporters
- enzymatic degradation
narrow spaces between adjacent cells bridged by protein channels
gap junctions
protein channels
connexins
other term for gap junctions
electrical synapses
gap junctions connect the ____ of two neighboring cells
cytoplasm
neurotransmitters are crucial for _____ in the nervous system as they play essential roles in transmitting signals between neurons
intercellular communication
classes of neurotransmitters
- amino acid neurotransmitters
- monoamine neurotransmitters
- acetylcholine
- unconventional neurotransmitters
- neuropeptides
molecular building blocks of proteins
amino acids
4 primary amino acid neurotransmitters
- glutamate
- aspartate
- glycine
- gamma-aminobutyric acid (GABA)
most prevalent excitatory neurotransmitter
glutamate
most prevalent inhibitory neurotransmitter but can have excitatory effects in some synapses
GABA
synthesized from single amino acids
monoamines
monoamines have ____ effects and are found in groups of neurons primarily in the ___
- diffuse effects
- brainstem
4 major monoamine neurotransmitters
- dopamine
- epinephrine
- norepinephrine
- serotonin
plays a crucial role in various brain functions
dopamine
neurons releasing epinephrine
adrenergic
neurons releasing norepinephrine
noradrenergic
also called 5-Hydroxytryptamine or 5-HT
serotonin
serotonin is synthesized from what amino acid
tryptophan
serotonin is classified as ____
indolamine
a unique small-molecule neurotransmitter
acetylcholine
where is acetylcholine found?
- neuromuscular junctions
- autonomic nervous system synapses
- central nervous system synapses
neurons releasing acetylcholine
cholinergic
two classes of unconventional neurotransmitters
- soluble-gas neurotransmitters
- endocannabinoids
- Produced in neural cytoplasm and diffused through cell membranes
- Regulate presynaptic neuron activity, involved in retrograde transmission
soluble-gas neurotransmitters
synthesized from fatty compounds
endocannabinoids
examples of endocannabinoids
- anandamide
examples of soluble-gas neurotransmitters
- nitric oxide
- carbon monoxide
approx number of neuropeptides that were identified
100
actions of neuropeptides depend on
amino acid sequences
5 categories of neuropeptides
- pituitary peptides
- hypothalamic peptides
- brain-gut peptides
- opioid peptides
- miscellaneous peptides
Originally identified as pituitary hormones
pituitary peptides
First identified as hypothalamic hormones
hypothalamic peptides
initially discovered in the gut
brain-gut peptides
structurally similar to opium components
opioid peptides
A catch-all category for others.
miscellaneous peptides
explores the influence of drugs on neurotransmitter systems and their impact on behavior
pharmacology of synaptic transmission and behavior
key players in brain function and behavior
neurotransmitters
can either facilitate or inhibit synaptic transmission
drugs
enhance neurotransmitter effects
agonists
inhibit neurotransmitter effects
antagonists
steps of neurotransmission
- Synthesis of the neurotransmitter.
- Storage in vesicles.
- Breakdown of leaked neurotransmitter in the cytoplasm.
- Exocytosis of neurotransmitters.
- Inhibitory feedback via autoreceptors.
- Activation of postsynaptic receptors.
- Deactivation of neurotransmitters.
bind to postsynaptic receptors and activate them
agonists
bind to postsynaptic receptors without activating them, blocking access to the neurotransmitter
antagonists
3 influential lines of research in behavioral pharmacology
- discovery of Receptor Subtypes:
WRINKLES AND DARTS - discovery of Endogenous Opioids: PLEASURE AND PAIN
- discovery of Antipsychotic Drugs: TREMORS AND MENTAL ILLNESS
found at motor neuron-muscle fiber junctions in the PNS
nicotinic receptors
abundant in the autonomic nervous system (ANS)
muscarinic receptors
Nicotinic receptors are _____, while muscarinic receptors are _____
- ionotropic
- metabotropic
an extract used by South Americans, is a nicotinic receptor blocker, paralyzing by blocking neuromuscular junction transmission
curare
a neurotoxin, is a nicotinic antagonist, inhibiting acetylcholine release at neuromuscular junctions
botox
obtained from opium poppy seed pods, used for pleasurable effects throughout human history.
opium
a major psychoactive component of opium, is addictive but also serves as an effective painkiller
morphine
