Flashcards in Test #2: CH4- neural conduction+ synaptic transmission Deck (63):
What is the purpose of this chapter?
To know how the neurons communicate through the nervous system.
The process involves...
-how signals are generated in the resting potential -->
-how signals transmit to neurons --->
- then neuron travels to the synapse -->
- then synapses sends the message to the next neuron
What is parkinson's disease?
Rigid muscles and slowness in communication of the NS that results in slow executing (put into effect) voluntary movements.
What are the three terms that are involved in the transmissions resulting in parkinson's disease?
Substantia nigra (black substance)
Striatum (part of the brain that controls movements)
Explain the transmission process of voluntary moments people can make before being diagnosed with parkinson's disease
1) Substantia nigra (neuron)
2) Dopamine (chemical)
3) Striatum (part of the brain that helps control movement)
Explain the transmission process of a person with Parkinson's disease
1) Substantia cells die
2) Dopamine production is decreased
3) lessening the amount of dopamine traveling to the striatum (a part of the brain that helps control movement)
What is the function of the striatum (a part of then brain)?
Helps control movement
In parkinson's disease there are low levels of dopamine so why not devise a medicine that produced or helps produce dopamine?
Dopamine does not readily penetrate through the blood brain barrier.
What is a medicine that has helped with people suffering from Parkinson's disease?
Why use L-dopa for Parkinson's disease?
L-dopa is the chemical precursor (a substance from which another is formed) of dopamine.
It readily penetrates through the blood brain barrier--> then converted into dopamine once inside of the brain
The differences in electrical charge between the inside and outside of a cell
What is the intracellular electrode called (electrode inside of the neuron membrane)?
their tips are so tiny and important because they are able to pierce through the neural membrane
What does it mean when the tip of an intracellular electrode is inserted in the neuron and is -70 mV is recorded inside of the neuron.
Means that it is 70 mV less than the outside.
Steady membrane potential of -70mV is called the neuron's...
When is a neuron polarized?
when the neuron is in it's resting state of -70 mV
negatively and positively charged particles
( from neural tissue that were separated)
Abbreviation for sodium ions
Abbreviation for potassium ions
In resting neurons, there are more ___ ions outside of the cell than inside
In resting neurons, there are more ___ inside of the cell than outside of the cell
special pores inside of the neural membrane that are specific to a particular ion (Na+ and K+) in which they can pass through
(Opposites attract) when the -70mV attracts the positive ion, Na+ into resting neurons in the membrane potential
pushes negative charges apart
positive charges apart
and opposite charges together
There is pressure of the ___ to enter the resting neurons
Pressure for Na+ ions to move down their concentration gradient
Ions that move from areas of high concentration to low concentration
Why is it that Na+ ions that are under electrostatic pressure under random movement not rush into the neurons, reducing the membrane potential?
Because sodium (Na+) ion channels are closed reducing flow into the neuron
Are the potassium ion channels closed like the sodium channels in the resting neuron (-70mV)?
No the potassium (K+) ion channels are open, but only a few of the K+ ions can leave they're held back by the negative resting membrane potential.
Sodium- Potassium pumps
mechanisms in the cell membrane that continually exchange three Na+ions inside the neuron for two K+ ions outside
mechanisms in the membrane of a cell that actively transports ions or molecules across the membrane.
Three factors that influence distribution of Na+ and K+ ions across the neural membrane
1) ins inmotion move down their concentration gradients, thus Na+ will tend to enter and K+ will tend to exit
2)The negative internal charge will create pressure for both Na+ and K+ to enter
3) sodium-potassium pumps transports 3 Na+ put for every K+ they transport in
What are the two possible effects of neurotransmitter molecules binding to postsynaptic receptors?
Depolarization (decrease the resting membrane potential (ex: -70Mv to -67Mv)
hyper polarization - increasing the resting membrane potential (ex: -70Mv to -72Mv)
Excitatory postsynaptic potentials (EPSP)
Postsynaptic depolarization that increase the likely hood the neuron will fire
Inhibitory postsynaptic potentials (IPSP)
Postsynaptic hyper polarization that decrease the likely hood the neuron will fire.
Involves EPSP and IPSP.
exactly how it sounds
weak signals elicit (respond) in small postsynaptic potential,
Strong signals elicit (respond) in large ones
What are the two characteristics of posthypnotic transmission
1) It's rapid almost instantaneously but...
It's decremental( decrease)
2)They decrease in speed and strength as they travel through the neuron
Where are action potentials generated?
at the axon initial segment
Threshold of excitation
How are action potentials generated
If the sum of the depolarizations and hyper polarization reach the reaching the axon initial segments at any time is sufficient to depolarize the members to a level usually around 65-mV where the action potential is generated
The action potential
reversal of the membrane potential from about -70 to about +50mV
They are all or none responses- either they either occur to their full extent or they don't
Adding or combining individual signals into one over all signal
Each multipolar neuron adds together all graded _______ and ______ potentials reaching its ____ and decided on whether to fire or not to fire depending on the ____
When two EPSPs are produced in different parts of the receptive membrane forma a greater EPSP. Vise vera for the IPSP.
EPSP and IPSP cancel each other out
post synaptic potentials produced in rapid succession at the same time sum to form a greater signal.
How are action potential produced and how are they conducted throughout the axon?
thought the action of voltage activated ion channels
voltage activated ion channels
ion channels that open or close in response to the changes in the level of the membrane potential
Why id the membrane potential relatively constant even though the Na+ neurons drive into the cell?
resting membrane is relatively impermeable (not allowing to pass through) to the Na+ ions because the few that do pass in are pumped out
What happens to the membrane potential of the axon is depolarized (decreased) to the threshold of excitation by the EPSP
-the voltage activated sodium channels open wide, Na+ rush in- changing membrane potential from -70 to +50mV
- then trigger the opening of voltage activated potassium channels to open
-At this point the K+ are driven out of the cell then sodium ion channel closes
-marks the end of - the "rising phase" and marks the beginning of rising phase
relative refectory period
the period of which it is possible to fire the neuron again but only by applying higher than normal levels of stimulation.
What occurs after the absolute refectory period?
relative refectory period
What occurs after the relative factory period?
the amount of stimulation necessary to fire a neuron returns to baseline
Absolute refractory period
a brief period about 1-2 seconds after the initiation of of an action potentential during which it is impossible to elicit a second one
Refectory period is responsible for two important characteristics of neural activity
1) that neurons travel in one direction throughout the axon
the rate of neural firing is related to the intensity of the stimulation
Why are axon conductions of action potential different from from EPSP and IPSP?
1)Conduction of action potentials are non decremental, they grow stronger as they move further along axon
2) conducted more slowly than postsynaptic potentials
3)IPSP + EPSP are passive- Conduction of axon potential is active
Opposite to the normal direction, conduction from axon terminals bad towards the cell body
axonal conduction in the normal direction- from the cell body to the axon terminals
Nodes of ravier
the gaps in between adjacent myelin segments on an axon
conduction of an action potential from one node of racier to the next along myelinated axon
Tiny nodules of various shapes that are located on the surfaces of dendrites and are the sites of most excitatory synapses in the mature mammalian brain
synapses at which the site of the neurotransmitters release of the site of neurotransmitter reception are in close proximity.
Non directed synapses
Synapses at which the site of neurotransmitters release and the site of neuron transmitter reception are not close together.
Short amino acid
Three factors that help to keep a neuron at rest