Synapses, Neurotranmitters, And Membrane Receptors Flashcards
One to one synapses
One pre synaptic to one post synaptic
-conveys info
Example of a one to one synapse
NMJ
One to many synapse
One presynaptic to more than one post synaptic
-amplify signal
Example of many to one synapse
Motorneurons in spinal cord
Many to one synapse
More than one pre synaptic to one post synaptic
-allows for integration of many signals. “Decides proper response”
What happens when a neurotransmitter binds
It changes the post synaptic membrane potential
What is it called when the neurotransmitter binding to the receptor changes the post synaptic membrane potential
Post synaptic potentials
Post synaptic potentials
- Can generalize neurotransmitters based on their usual effect
- can be excitatory or inhibitory
What type of post synaptic potentials depolarize cell towards threshold (+)
Excitatory post synaptic potentials
Excitatory post synaptic potentials are usually the result of
Opening Na+ channels
What are some common excitatory post synaptic potentials
Glutamate, acetylcholine
This type of post synaptic membrane potential hyperpolarizes away from threshold (-)
Inhibitory post synaptic potentials
Inhibitory post synaptic potentials are usually the result of
Opening Cl- channels
Examples of inhibitory post synaptic potentials
GABA and glycine
Synaptic integration of IPSPs and EPSPs
Usually each neuron is the post synaptic cell for numerous pre synaptic cells
-signals have to be integrated-combined together and a decision made
How does signal integration happen
Through temporal and spatial summation
Temporal summation
- time
- can be from one or more pre synaptic
- inputs overlap, membrane does not completely repolarize between (additive)
- lateral impulses further depolarize towards threshold
How do ISPSs and EPSPs integrate?
Similarly
Spatial summation
- multiple inputs at the same time
- multiple pre synaptic provide input at the same time, impulses add together
Facilitation, augmentation and potentiation of synaptic activity
- rapid stimulation of pre synaptic increases response in post synaptic
- increase Ca2+ in pre synaptic leads to more NT released
Increased ____ in pre synaptic leaders to more NT released
Ca2+
Short term depression of synaptic activity
Repeated stimulation can expend the stored NT
What does long term modulation of synaptic activity require
Transcriptional changes
- altering receptor cxn on post synaptic cell
- altering amount of NT chores in pre synaptic cell
Consider a cell at RMP, opening of which ion channel would result in EPSP?
Calcium
Consider a cell at RMP, opening of which ion channel would result in an IPSP
Potassium
Substances released by pre synaptic cell, classified by structural features
neurotransmitters
What are some examples of NT
- choline esters
- biogenic amines-derived from aa
- aa
- gaseous transmitters
- neuropeptides
A neurotransmitter must:
- be synthesized from presynaptic cell
- be released from pre synaptic upon stimulation
- if applied exogenously to post-syn, elicit response similar to the normal response
What do NT differ from hormones
Hormones are transported by blood to target organs
What is acetylcholine made from
-acetate and choline (most of which is recycled from previous release)
Where is acetylcholine stored
Vesicles
When is acetylcholine released
In response to increased Ca2+ influx into nerve terminal
How is acetylcholine broken down?
Broken down into acetate and choline by acetylcholine esterase
What are biogenic amines derived from
Aa
Examples of biogenic amines
Tyrosine-dopamine, epinephrine, and norepinephrine
Production of biogenic amines
Based on presence of proper enzymes
Another name for biogenic amines
Monoamines
How are biogenic amines broken down
Broken down by monoamine oxidase (MAO) and Catechol-O-methyltransferase (COMT)
-useful in determining amount of NT released
Biogenic amine: tryptophan
Makes serotonin and melatonin
Biogenic amine: histidine
Makes histamine
Amino acids as NT
Actual amino acids
- GABA, glutamate and glycine
- GABA(a) receptor is site of benzo and barbs action in CNS
What is the site of benzo and barbs actions in CNS
GABA(a) receptor
Amino acid neurotransmitter
Gaseous NT
Cell permeant gasses (NO) that can act on post syn cells
Neuropeptides as NT
Larger molecules like ADH and Oxytocin
- neuromodulators
- neurohormones
Act on pre syn cell to affect amount of NT release, also can be co-secreted with NT to modulate post syn response
Neuromodulators
Example of neuromodulators
VIP with Ach and GI
Made by neurons and released into blood stream to have effects
Neurohormones
Examples of neurohormones
ADH
Released along with NT to augment effect
Purines (adenosine and ATP)
Example of purines
ATP + norepi increases VSMC contraction
What is the function of the signal dictated by
Receptor, not NT
What ar the two types of NT receptors?
Metabotropic and ionotropic
This type of receptor generates 2nd messengers
Metabotropic
This type of NT receptor is an ion channel
Ionotropic
Opening and closing of a ionotropic NT receptor
Dependent upon binding of ligand
Examples of ionotropic receptors
- nicotinic receptors are primarily Na+ channels
- GABA(a) are chloride channels
Receptors are coupled to an intracellular protein. Binding of ligand activates intracellular protein to generate 2nd messenger molecules
Metabotropic
Once 2nd messengers are activated by metabotropic receptors, what can they do
- interact with and alter ionic ion channels
- activate kinases to eventually alter transcription
Receptor tyrosine kinases **
- growth factor signaling
- starts kinase cascade to change transcription
- insulin
- antagonistic
What ar most metabotropic receptors?
G-protein coupled receptors (GPCR)
What targets about 50% of all drugs
Metabotropic receptors
What determines the metabotropic receptors function
The intracellular G protein that they are coupled with
What are the three subtypes of metabotropic receptors
Gs, GI, and Gq
What does Gs and Gi do
Alter activity of adenylate cyclase which makes cAMP
What can cAMP do
Open ion channels and initiate kinase cascade thigh out PKA
What stimulates AC (adenylate cyclase)
Gs, increases cAMP
What inhibits AC (adenylate cyclase)
G1, decreases cAMP
What is cAMP degraded by
Phosphodiesterase (PDE)
Gq activates phospholipase C to make what
IP3 and DAG
____ can open calcium channels on intracellular stores
IP3
____ can activate a kinase cascade through PKC
DAG
To know effect of GPCRs…
Know coupled G-protein and effect of 2nd messenger
B1 and B2 adrenergic receptors
Both are Gs coupled, both make cAMP
- B1 predominantly in heart, cAMP in heart contractions (increases force)
- B2 primarily in smooth muscle, cAMP in smooth muscle relaxes smooth muscles
Important types of GPCRs
- muscarinic (respond to Ach)
- alpha adrenergic (NE and Epi)
- beta adrenergic (NE and Epi)
Important muscarinic receptors
M3 (Gq)
M2 (Gi)
Important alpha adrenergic receptors
a1 (Gq)
A2 (Gi)
Important beta adrenergic receptors
B1 and B2 (Gs)
What makes cGMP?
Guanalyl cyclase
Guanalyl cyclase
- makes cGMP
- can be coupled to receptor or not
- non receptor can be activated by NO
- broken down by PDE
What is cGMP important for
It is a vital second messenger in the phototransduction pathway
Which of the following would be classified as a 2nd messenger
Calcium
Serotonin binds to a receptor and causes a change in membrane polarity, it is a _______
Insufficient data
