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BIO 131 Exam 1 Study Guide Prt 2 of 3
Terms in this set (34)
Resting Membrane Potential (RMP) is the ____ in charge across the cell ____ for a cell at ____.
Action Potential (AP) is a very brief, large ____ that travels over long distances through an ____, w/out losing _____.
AP's are for rapid ____ over long ______.
Graded Potentials & Receptor Potentials are good for short....?
In order to get the RMP past Threshold to generate an AP, a _____ graded potential is needed.
Graded Potentials are found on
Dendrites & Cell body
Receptor Potentials are found on
Special senses & Visceral receptors
Equilibrium Potential (Eion) is the charge in the _____, which generates an _____ gradient strong enough to be exactly _____ and ____ to the _______ gradient.
What does the Nernst equation do?
It calculates the equilibrium potentials for any given ion at 37°C.
It calculates the voltage, at which the electrical & concentration gradients for a given ion are equal & opposite
What does the Goldman-Hodgkin-Gate Equation?
It calculates membrane potentials by taking equilibrium potentials & membrane permeability for each ion into account.
A Subthreshold Graded Potential is not....
Strong enough to initiate an AP at the trigger zone because it does not bring the membrane to threshold (-55mV).
A Suprathreshold Graded Potential (STGP) initiates an AP in the axon because....
It brings the membrane in the trigger zone to threshold & opens V-gated channels.
Assume a cell has a charge of +50mV on the outside & -50mV on the inside, what is the RMP?
Assume that the RMP is -70mV and that there is a higher concentration of K+ in the ICF than there is in the ECF. Does K+ move out until there is an even distribution of K+ between ECF & ICF?
Why or why not?
K+ equilibrium potential is -90mV. Because K+ is moving out to the ECF, the RMP will continue to grow more negative until it reaches -90mV.
Assuming that the equilibrium potential for K+ is -90mV & and the RMP of the cell is -70mV, in which direction is there a net movement of K+ until the equilibrium potential is reached? (Which of the 2 gradients, concentration or electrical, is initially stronger?)
Net movement of K+ is toward the ECF.
The Concentration gradient is initially stronger.
When the K+ channel opens the membrane potential will become more ____ & the cell will ____.
What ensures that the AP travels the entire length of the axon?
What ensures that the AP travels only in one direction?
The area behind the leading edge is in absolute refactory period (ARP).
-- Na+ channels are either already open or closed--
What is the difference between continuous & saltatory conduction?
Saltatory conduction have myelinated axons which enables for AP's to travel fast & over long distance.
Continuous are unmyelinated axons, so the AP's travel very slow and only over short distances.
What is the importance of myelin?
It electrically insulates the axon which allows the electrical signal to jump from node to node. This ensures that no charge is lost.
What would happen if the myelin sheath was lost?
The electrical signal would lose its charge over time which would result in slower travel and be carried only for short distances.
What is an EPSP
Excitatory Postsynaptic Potential= depolarizes the postsynaptic cell by bringing them membrane of the postsynaptic cell closer to threshold.
How is an EPSP generated?
By opening Na+ channels and closing K+ channels.
What is an IPSP?
Inhibitory Postsynaptic Potential = hyperpolarizes the postsynaptic cell by moving the membrane of the postsynaptic cell further away from threshold.
How is an IPSP generated?
By opening Cl- channels and opening K+ channels.
What is hypokalemia?
Blood concentration of K+ falls too low. This causes the membrane potential to move further away from the threshold, making it harder to generate an AP.
What is hyperkalemia?
Is when blood concentration of K+ is too high. This causes the membrane potential to move closer to the threshold, making it easier to generate an AP in response to smaller graded potentials.
What is the diff. between Spatial & Temporal summation?
Spatial summation occurs when the currents from nearly simultaneous graded potentials combine.
* the graded potentials originate at diff. locations on the neuron!
Temporal summation is when summation occurs from graded potentials overlapping in time.
* the graded potentials are from the same presynaptic neuron!
What is the diff. between Presynaptic Facilitation & Presynaptic Inhibition?
In Presynaptic Facilitation, input from an excitatory neuron increases neurotransmitter release by the presynaptic cell.
If modulation of a neuron decreases its neurotransmitter release, it is called a Presynaptic Inhibition.
What is the diff. between an Agonist and an Antagonist?
An Agonist binds & activates a receptor.
An Antagonist binds and BLOCKS the receptor w/out inhibiting a response in the target cell.
How do ACh receptor antagonists affect signaling?
With ACh receptors blocked, ACh is unable to bind to the nicotinic ion-channel receptors on the muscle cell membrane. This prevents Na+ from flowing into the muscle cell and trigger a muscle contraction.
-- aka, muscle paralyses--
What is the Absolute Refractory Period?
Represents the time required for the Na+ channel gates to reset to their resting positions.
It is the time when a 2nd AP cannot be triggered.
What is the Relative Refractory Period?
It follows the Absolute Refractory Period.
During this time, some but not all Na_ channel gates have reset to their original positions, & K+ channels are still open.
--only a larger than normal stimulus can initiate a new AP, during this period--
What is the greatest danger when AP transduction along neurons is inhibited in the body?
- how could this lead to death?-
If AP is inhibited then signals cannot be sent to the CNS and PNS. This hinders our bodies natural reflex ability and causes our diaphragm to become flaccid. A loose diaphragm leads to the inability for the lungs in inhale fully, resulting in shortness of breath= difficulty breathing.
No O2= Death.
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