Physiology I

Description:	Graded Potentials and Action Potential Generation - Test 3
Category:	Physiology
Created by:	Tri 2 on 2007-11-10

Question	Answer
What is a graded potential?	A subthreshold electrical stimuli that does not produce a true action potential, but does generate electrical signals
What types of stimuli are there?	Electrical, Chemical, and Mechanical
How many types of physiochemical disturbances does stimuli produce and what are they?	2 Types: 1. local, graded, nonpropagated potentials called Receptor or Generator potential AKA Synaptic potentials or Electrotonic Potentials 2. Action potentials (complete depolarization or nerve impulse)
True or False, Graded potentials are conducted with decrement?	True, Decrement think DECREASE. They decrease in magnitude the further they get from the origin.
Why does decrement occur in graded potentials?	Because charges are lost due to leaky channels as the potential is conducted
How far can a graded potential travel?	1-2 mm
True or false, Graded potentials serve as the only communication in some neurons?	True
Name the 4 types of Graded Potentials?	1. Receptor or Generator Potentials 2. Pacemaker Potential 3. Post synaptic Membrane Potential 4. End Plate Potential
Sensory Receptors respond to stimuli from:	1. Mechanoreceptors (movement) 2. Thermoreceptors (temp) 3. Nocioreceptors (pain) 4. Chemoreceptors (Chemical) 5. Electromagnetic Receptors (Vision)
Graded potentials from stimuli are called?	Receptor Potentials
True or False, Graded potentials are responsible for cardiac automaticity?	True, due to the Pacemaker Potential
What type of graded potential develops at the neuromuscular junction?	End Plate Potential
True or False, the size and shape of action potentials are not influenced by the size of the stimulus?	True
True or False, Action Potentials require specific voltage gated ion channels?	True
Can action potentials occur in all regions of the cell membrane?	No, just the portions that are electically exciteable
What is the duration of an action potential?	1 - 5 msec
What senses are dependant upon action potentials?	Sight, Hearing, and Touch
What are the 3 Stages of Action Potentials?	1. Resting or Polarized Stage 2. Depolarization Stage 3. Repolarization Stage
What is the resting membrane potential for Nerves? Heart Pacemaker? Skeletal Muscle?	Nerves = -90mv Heart Pacemaker = -60mv Skeletal Muscle = -83 mv
In what stage of the action potential do Na+ ions flow into the cell?	Depolarization Stage
In what stage of the action potential do K+ ions flow out of the cell?	Repolarization
What is overshoot described as in the action potential generation?	The point at which the membrane potential becomes positive.
What is happening during repolarization?	Na+ channels are inactivated and K+ are opened
True or false, the K+ voltage gate has both fast and slow gates?	False, K+ has a single slow gate whereas Na+ has both.
What is the refractory period?	The time when it is either impossible or more difficult to generate a second action potential
What is absolute refractory?	The period in which the voltage gated channels have not reset and therefore do not respond to stimulation
What is relative refractory?	This is during the period positive after potential in which the cell is hyperpolarized and is more diffficult to generate a second potential
What is voltage Inactivation?	A cell membrane is maintained at a voltage potential above threshold and the voltage gated channels are not reset then action potentials can not be generated
What is accomodation to slow depoalarization?	This is what happens when a slow depolarizaion occurs which does not cause the voltage gated channels to respond and in turn does not produce an action potential.