chapter 4 Flashcards
describe the resting membrane potential
polarized
-70mV
How can you record membrane potential?
comparisons of intracellular and extracellular electrode readings
what did Hodgkin and Huxley experiment on?
-giant squid motor neurons
how are sodium ions distributed?
- higher outside the cell
describe the resting membrane in relation to chloride ions
- concentration is higher outside the cell but only slightly resisted
describe the potassium concentrations in relation to resting potential
concentration is higher inside driven inside by electrostatic pressure but driven out by concentration gradient
what is concentration gradient?
tends to equally distrubute by moving high to low concentration
what is electrostatic pressure?
attractive forces between opposite charges and repelling forces between like charges
what are non-homogenizing factors to maintain resting potential?
passive and active movement
what is passive movement?
random motion due to selectively permeable ion channels
what is active transport?
sodium potassium pumps that maintain stability of resting potential in spite of random motion
what do post synaptic potentials do?
create signals in neurons
what do excitatory neurotransmitters do?
depolarization to make the membrane potential less negative
what do excitatory post synaptic potentials do?
increase the likelihood of an action potentials
what do inhibitory neurotransmitters do?
hyperpolarize the cell and make membrane potential more negative
what do inhibitory post synaptic potentials do?
decrease the likelihood of action potentials
what is the rate of EPSPs and IPSPs?
instantaneous rate of transmission with variable duration
describe amplitude of grade potentials
proprotional to signal intensity
describe transmission of graded potential
decremental transmission that is from weakening passive spread
what is responsible for generation of EPSPs?
sodium influx
what is responsible for IPSPs?
chloride influx
how are postsynaptic potentials integrated?
adding or combining signals into one overall output
what is spatial summation?
integration across post synaptic locations when local EPSPs and IPSPs occur simultaneously
what is temporal summation?
integration across time on the same synapse in rapid succession
what ae action potentials?
massive reversal of membrane potential that does not degrade over space
how are action potentials generated?
voltage-gated sodium ion channels that open or close in response to the membrane potential
when threshold of activation for action potentials is reached what happens?
voltage-gated sodium channels open and sodium rushes in due to electrostatic and concentration gradient
what is the second step during an action potential?
voltage-gated potassium channels open and potassium is driven out due to electrostatic and concentration gradient to repolarize cell
what is the absolute refractory period?
brief post initiation where it is impossible to to initiate new action potentials due to inactive sodium channels
what does the absolute refractory period do?
prevents backwards motion of action potentials and limits firing rate
what is the relative refractory period?
follows absolute period and requires larger than threshold stimulus to initiate new action potentials
describe conduction of an AP
active and passive nondecremental
anterograde conduction
from hillock to boutons
retrograde conduction
boutons to hillock
orthodromic conduction
anterograde
antidromic conduction
retrograde conduction
describe conduction in myelinated axons
instant conduction along myelin with passive, saltatory conduction
when is axonal conduction fater?
in larger, myelinated neurons
describe conduction in interneurons
passive and decremental that functions to integrate neural activity in brain structure
what are some differences in cerebral neurons from squid motor neurons?
fire AP continually, duration, frequency, and amplitude differ, dendrites can conduct APs
directed synapse
site of neurotransmitter release close to post synaptic contact
undirected synapse
site of release and contact for varicosities that is common for monoamines and neuroendocrine system
first step of chemical transmission of signals
AP reaches end of axon terminal
second step of chemical transmission of signals
calcium enters the cell
third step of chemical transmission
release of neurotransmitter into the cell
fourth step of chemical transmission
receptors influnece post synaptic neurons
inotropic refers to
ion permeability
metabotropic refers to
intracellular signalling
sixth step of chemical transmission
neurotransmitter degradation and recycling
small molecule neurotransmitter synthesis
enzymatic conversion of amino acid precursors
large molecule neurotransmitter synthesis
peptides that are processed by enzymes
where are small molecule NT synthesized
cytoplasm and golgi apparatus
how are small molecules NT’s released?
in pulses for each action potential
where are large molecule NT’s released?
into extracellular fluid and ventricles for bloodstream
where are large molecule NT’s synthesized?
cell body, packaged in vesicles and trasported with cytoskeletons to terminal
describe packaging of NT’s
proteins are syntehsized in rough endoplasmic reticulum then transported to the golgi where they bud off the golgi to form vesicles and transporter proteins actively pump NT’s into them after anterograde axonal transport
what are small clear core vesicles?
contain the small molecule NT’s
what are large dense core vesicles?
contains the neuropeptides of 90-250 diameter
what is coexistence?
when more than one type of NT is synthesized and released in neurons
what is anterograde to axon terminal transport of neurotransmitters?
motor proteins of kinesin use steps of attachment/ detachment; microtubules highway system
what does transport of NT require?
energy and calcium
how are NT’s released?
AP in axon terminals that opens voltage-gated calcium channels clustered in the active zone and activate proteins
what do the active proteins in neurotransmitters release do?
mobilize vesicles and fuse vesicles with synaptic membrane
what is vesicle recapturing?
local resynthesis of synaptic vesicles
where are NT receptors?
in presynaptic and postsynaptic cells