neurophysiology Flashcards
neurotransmitters
how many types of NTs can a single neuron type, release?
how do neurons respond to different NTs?
only one !
any given neuron can respond to several NTs
define the following NTs
1 Acetylcholine
2 glutamate
3 GABA
4 Norepinephrine
5 Dopamine
6 Serotonin
1 found in the neurommuscular synapses (autonomic NS )
2 Main excitatory NT in brain
3 Main inhibitory NT in brain
4 Autonomic NS ,learning, emotion behavioural pathways
5 learning, emotion, behavioural pathways
6 learning, emotion, behavioural pathways
NTs are classified by their functions.
Explain the difference between excitatory and inhibitory NTs and give examples for each type.
- Excitatory NTs cause DEPOLARIZATION of post-synaptic neurons
(eg. Glutamate) - Inhibitory NTs cause HYPERPOLARIZATION of post-synaptic neurons
(eg. GABA and Glycine)
true / false :
Some NTs can have both inhibitory & excitatory effects
True
what determines whether a NT is inhibitory or excitatory ?
Determined by the receptor type of the post-synaptic neuron
Explain how acetylcholine can be both inhibitory and excitatory
acetylcholine is excitatory at neuromuscular junctions with skeletal muscle because of its NICOTINIC receptor
it is inhibitory in cardiac muscle bc of its MUSCARINIC receptor
Name and define the 2 types of NT receptor mechanisms
Direct : NTs that opens ion channels and promotes rapid responses iow “fast synapses”
- ACh and amino acids
Indirect : NTs that act through second messengers and promotes long lasting affects iow “slow synapses”
-biogenic amines, peptides & dissolved gases
Discuss the effects of NTs i.t.o. their receptors and how it changes the membrane potential
NT receptors mediate changes to the membrane potential according the the amount of NT released and the amount of time the NT is bound to receptors.
NTs will affect the membrane potential as long as they are bound thus they must be deactivated
How can graded potential be stopped?
Graded potentials will continue as long as NTs are bound to its receptor. In order to stop a graded potential , the NT must be INACTIVATED / REMOVED .
Discuss the 3 ways NT effects are deactivated
1 ACTIVE TRANSPORT
- NT will be actively pump back into the pre-synaptic cell (axon terminal ) or nearby neuroglia where they can be reused or transported into glial cells
2 ENZYMES
- Enzymes are present in the synaptic cleft that will breakdown the NT to quickly stop the signal (thus inactivating the NT)
- eg) acetylcholinterase
3 DIFFUSION
- NTs can diffuse out of the synaptic cleft to REDUCE its signal
Define Acetylcholinesterase & give its chemical reaction
An enzyme found in the synaptic cleft that degrades acetylcholine
NOTE: It assures that no excess of acetylcholine remains in the synaptic cleft to cause the continuous activation of receptors.
(AchE) Acetylcholine -----> Acetate + Choline
What are the products of acetylcholine after its broken down by Acetylcholinesterase and what happens to them ?
The products are acetate and choline.
Both products are reabsorbed and recycled so that they can be used again in transmitting another chemical messege. BUT
Choline is actively transported back into pre-synaptic terminal and used to reform ACETYLCHOLINE with the help of the enzyme ChAT ( Choline acetyl transferase )
what is Acetylcholine made up of ?
Choline and Acetyl CoA
what is the chemical reaction for the formation of Acetylcholine ?
ChAT
Acetyl CoA + Choline ——–> Acetylcholine
True / False : drugs do not alter synaptic activity
FALSE
Many drugs alter synaptic activity
What are the possible effects of drugs on synaptic activity ?
Give 2 examples
A-M-I-R
A- Altering synthesis , storage or release of NTs
M- Modifying NT interaction with its receptor
I- Influencing NT reuptake /destruction
R- Replacing deficient NT with a substitute NT
(examples)
=> SSRI’s
=> Tetanus Toxin
What is a tetanus toxin?
Drug
They prevent the release of GABA from inhibitory neurons at neuromuscular synapses.
- causes uncontrolled muscle spasms (too much excitation) and lock jaw
What are SSRI’s ?
Drugs
Selective Serotonin Reuptake Inhibitors
- they prevent the reuptake of serotonin thus increasing the length of time serotonin is at the synapses
- used to treat depression
How do neurons communicate ?
ELECTRICALLY through electrical gradients & CHEMICALLY through NTs
Define electrical Communication
The movement of ions in and out of cell membranes
- can be small, local or travel long distances down the branches of the cell
=> EPSPs, IPSPs & Action potencial
Define Chemical communication
The release of NTs (ligand) to nearby NT receptors (receptor) at synapses.
- effect on post-synaptic cell will depend on the NT and the receptor/ion channel interaction
How are the Nervous system pathways organized ?
Organized into complex pathways of multicellular connections. (groups of multiple cells interact as neural units)