Shared Flashcard Set

Details

Membrane Potentials and Action Potentials
Membrane Potentials and Action Potentials
56
Physiology
Post-Graduate
01/19/2013

Additional Physiology Flashcards

 


 

Cards

Term
Why is the resting membrane potential -65mV and not -95mV?
Definition
B/c it is easy to manipulate -65mV rather than -95mV
Term
How is an action potential triggered in a neuron?
Definition
1) Start of the action potential 2)Trigger zone/Axon hillock 3) Voltage gated Na+ channel 4) All or none principle
Term
What is the trigger zone?
Definition
Axon hillock- Where graded potentials come together to form an IPSP or EPSP. 
Term
NT can open ion channel in Pre-synaptic?
Definition
False, NT's open ion channels in dendrites and cell body (post synaptic cell) not pre-synaptic
Term
What does EPSP's and IPSP's stand for?
Definition

EPSP= Excitatory postsynaptic Potential 

IPSP= Inhibitory postsynaptic potential 

Term
Where are the EPSP's and IPSP's summed?
Definition
Axon Hillock/Trigger zone
Term
Define Graded potentials?
Definition

Potentials generated at dendrites and cell body is graded and can decay over distance. 

vs. Action potential are generated at axon hillock/trigger zone and have an "All or none effect" (dont decay over distance) 

Term
T/F: The decay of graded potential is exponential?
Definition
True
Term
What determines if an action potential will occur?
Definition
1) IPSP's 2) EPSP's
Term
What are the two types of graded potential summation?
Definition
1) Spatial 2) Temporal
Term
What is the difference between Spatial and Temporal summation?
Definition

1) Temporal summation are PSP's (postsynaptic potentials) from one presynaptic neuron. The PSP's are sepreated by time and are fired rapidly one after the other and are summated to reach the threshold to cause an Action potential (AP)

2) Spation summation are PSP's from multiple presynaptic neurons (on the same post-synaptic soma) firing IPSP's or EPSP's and the soma summates these to form an AP.

Term
What do they mean by "all or none" when referring to AP?
Definition
Means that the potential will fire regardless after the threshold is reached (At axon hilloc) and will not decay over time. 
Term
Define AP?
Definition
Rapid change in membrane potential from - to + and back to -; All of none
Term
What are the 4 stages of an AP?
Definition
1) Resting stage 2) Threshold 3) Depolarization 4) Repolarization 
Term
What channels are active in the resting stage?
Definition
1) K+ leak channels 
Term
What channels are active during the Depolarization phase of action potential?
Definition
1) Voltage gated Na+ channels
Term
What channels are active during the Repolarization of AP?
Definition
Voltage gated K+ channels
Term
When does the VG Na+ and VG K+ channel open?
Definition
They both respond at the same time to depolarization but K+ channels have SLOW ACTIVATION, so they don't actually have K+ go down the gradient till +35mV
Term
Why don't AP's decay over time?
Definition
Depolarization of the axon at one point causes voltage-gated Na+ channels to open ahead of this point. Thus the AP migrates down the axon. 
Term
List 3 Amino Acid NT and their fxn?
Definition

1) Glutamate- Excitatory NT of brain

2) GABA- Inhibitory NT of brain

3)Glycine- Inhibitory NT of spine 

Term
List 5 amine NT?
Definition
1) Serotonin (5-HT) 2)Histamine 3)Dopamine (DA) 4)Norepinehprine (NE) 5) Epinephrine (E)
Term
Name a purine derivative NT?
Definition
ATP
Term
Name 3 types of peptide NT released by the Hypothalamus?
Definition
1) Thyrotropin releasing hormone 2) Lutenizing hormone releasing hormone 3) Somatostatin 
Term
Name 7 peptide NT released by the Pituatary?
Definition
1) Adrenocortico tropic hormone-ACTH 2)Prolactin 3)Lutenizing Hormone 4) Thyrotropin 5) Growth Hormone 6)Vasopressin 7) Oxytocin
Term
What kind of NT are endorphins?
Definition
Peptide NT
Term
What are 2 types of Peptide NT that are endorphins?
Definition
1) Opiods 2)enkephalins
Term
Name 3 'other' types of peptide NT?
Definition
Substance P, Andgiotensin II, Bradykinin
Term
Where are peptide NT made?
Definition

In the cell body of neuron (and travel all the way down in the terminus of neuron)

-EX. Thyrotropin Hormone, Lutenizing Hormone, Bradykinin, ACTH...etc,

Term
Where are small NT (Dopamine, 5-HT, ATP, Histamine...etc) made?
Definition
Small NT are made in axon terminal?
Term
How is a small NT made?
Definition
Precursor molecule (tryptophan) with the aid of a synthetic enzyme turns into a NT molecule (seratonin) which gets packed into vesicles with the help of Transporter proteins.
Term
Name 2 gas NT and where are they made?
Definition

1) Nitric Oxide (NO) 2) Carbon monoxide (CO)

- Gas NT are not made in cell body or the axon terminal they diffuse right thru the neuron

Term
Name 2 endocannabinoid NT?
Definition
1) Anandamide 2) Arachidonyl glycerol
Term
How effect does THC have in the neuron?
Definition
THC causes the depression of glutamate (excitatory NT of brain) and decrease the amount of Ca2+ released. So THC (comes from weed) slows neural transmission in brain and slows movement
Term
Name the neuron that releases 1) Ach 2) DA 3)NE 4)Glu 5) GABA 6)Peptide
Definition
1) Cholinergic neuron 2) Dopaminergic 3) noradrenergic 4) Glutamatergic 5) GABAergic 6) peptidergic 
Term
Name 3 types of NT receptors and give examples
Definition

1) Transmitter-gated ion channels (aka ionotropic receptors)- Example: Nicotinic receptor and GABA receptor

2) G-protein coupled receptors (aka metabotropic)- ex. Muscarinic receptor 3) Enzyme linked receptor (ex Tyrosine Kinase receptor) 

Term
Give two examples of Ach receptors?
Definition
1) Nicotinic Receptor (Ionotropic receptor) 2) Muscuranic Receptor (Metabatropic receptor) 
Term
On the Nicotinic and muscarinic receptors, note what 1) NT acts on it 2) Agonists 3)Antagonists 
Definition

Nicotinic receptor (Ionotropic receptors)- 1) Ach 2)Ach and Nicotine 3)Curare 

Muscarinic (Metabotropic receptor)- 1) Ach 2)Ach and Muscarine 3) Atropine 

Term
What type of NT receptor is the GABA receptor? What kind of ion channel is GABA?
Definition
Ionotropic receptor/ Transmitter-gated ion channels and it is a chloride ion channel 
Term
What are the 5 things that can bind (agonist) to a GABA receptor?
Definition
1) GABA NT 2) Benzodiazapine 3) Barbiturate 4) Steriod 5) Propofol
Term
Describe the mechanism of giving a patient propofol?
Definition
1) Propofol bind to the GABA receptors (Propofol is an agonist for GABA) 2) GABA receptors activate/open and allow Cl- to go down their gradient (inside the cell) which causes the Vm to become more negative (hyperpolarize) thus creating an IPSP 3) The IPSP summate and DO NOT reach threshold and thus do not creat an AP, thus no neuronal transmission is made in the brain (since GABA receptors are found in the brain) 
Term
What happend when GABA and a pentobarbital is released as NT on the GABA receptors?
Definition
Giving the barbituate adittionally (since GABA NT is naturally occuring in the brain) opens the channel more frequently thus causing more IPSP's
Term
What are three targets of the activated metabotropic receptors?
Definition
1) Enzymes (ex. PLC, Adenyl Cyclase) 2) ion channels 3) Gene transcription 
Term
What is the fxn of Adenyl cyclase and what is it activated by?
Definition

1) Fxn- to make ATP to (secondary messenger molecule) cAMP of GTP to cGMP

2)Activated by diffused G-protein

- Adenyl cyclase is an enzyme that is a targeted by activated G-proteins

Term
What is the fxn of PLC and what activates it?
Definition
1) Fxn- to make IP3, membrane phospholipid, and DAG by splitting PLC (Phospholipase-C) 2) PLC is activated by Acitvated diffused g-protein.
Term
What type of NT receptor are protein kinases?
Definition
Enzyme linked receptors
Term
What is Protein kinase fxn? and what are its indirect effectors?
Definition
Fxn to P-late protein, which changes its conformotion,thus changing the protein's fxn, and the P-lated protein open's ion channels or alters enzyme function. 
Term
Name a fast, short acting fast synaptic potential and a Slow synaptic potentials and has long term effects NT receptor? 
Definition

1) Transmitter gated ion channels (aka ionotropic channels) - Ex. GABA receptors and Nicotinic receptor 

2) G-protein coupled receptor (aka metabotropic receptor)- Ex. Muscarinic

Term
What are 3 ways to terminate a transmitter action? and Give description
Definition

1) Diffusion- NT can diffuse out of the synaptic cleft

2) Breakdown- Enzyme inactivat NT's (Ex. Actelycholinesterase) 3) Re-uptake- NT can be returned to axon terminals for reuse or transported into glial cells 

Term
In Layman terms describe Potentiation of synapses?
Definition
Creating of memories
Term
How does potentiation of synapses work?
Definition

1) Increases the release of NT from presynaptic neuron which, 

2) Inc. the response in the postsynaptic neuron

Term
during Potentiation of synapses, there is an inc. of NT released but what else can it cause?
Definition
Depression of communication
Term
Describe synaptic fatigue?
Definition
After many, many AP eventually the NT stored in vesicles is depleted.
Term
What can clinically happen in a synaptic fatigue?
Definition
Siezure- NT storage depleted 
Supporting users have an ad free experience!