Synaptic Transmission Flashcards
Communication witihin Neurons - Resting Potential, mV
-70mV
Communication witihin Neurons - Resting Potential, Na+
High Na+ inside the cell
Low Na+ outside the cell
Move in down electrochemical gradient
Communication witihin Neurons - Resting Potential, K+
Low K+ inside the cell
High K+ outside the cell
Move out down chemical gradient
Communication witihin Neurons - Excitation Threshold, mV
-55mV
Communication witihin Neurons - Excitation Threshold
If enough Na+ move into the cell, excitation threshold will be reached
Na+ channels will open, allowing an influx of Na+ into the cell, further depolarising the membrane
Communication witihin Neurons - Action Potential
Action potential is fired after excitation threshold has been reached
After firing, Na+ channels close and K+ channels open for repolarisation
Communication witihin Neurons - Action Potential, mV
30mV
Communication witihin Neurons - Refractory Period
Hyperpolarisation occurs as too many ions are taken out
Na+ / K+ pump redistributes charges
3 Na+ in, 2 K+ out, 1 ATP
Communication witihin Neurons - Refractory Period, Hyperpolarisation, mV
-80mV
Communication witihin Neurons - Refractory Period, Absolute
No stimulus could generate another action potential
Communication witihin Neurons - Refractory Period, Relative
A stimulus would need to be stronger than average in order to generate another action potential
Communication witihin Neurons - All-or-Nothing Principle
An action potential will only fire if excitation threshold is reached
Strength of a stimulus does not relate to the amount of depolarisation that occurs
If excitation threshold is not reached, and action potential will not be fired
Communication between Neurons - Neurotransmitters
Chemical substances released by the axon terminal after the arrival of an action potential
Communication between Neurons - Neurotransmitters, Mechanism
Ca2+ channels open at the presynaptic terminal when action potential arrives, with the influx of Ca2+ resulting in the release of neurotransmitters into the synaotic cleft
Neurotransmitters diffuse across the cleft and bind to complementary ligand-gated Na+ receptors in the postsynaptic membrane
If this binding blocks Na+, action potentials are inhibited
If this binging opens Na+ channels, another action potential is started in the next neuron
Neurotransmitters are then reuptaken or broken down and reused
Communication with Neurons - Excitatory Current
An action potential is propogated along the axon when Na+ difuse down the chemical gradient and depolarise the adjacent section of the membrane
Communication between Neurons - Neurotransmitters, Summation
One action potential from one neuron will not release sufficient neurotransmitter to generate an impulse in the next neuron therefore summation is required
Communication between Neurons - Neurotransmitters, Summation, Temporal
Multiple impulses are sent along the same neuron in a short period of time
Communication between Neurons - Neurotransmitters, Summation, Spatial
Multiple impulses are sent along different neurons at the same time
Communication between Neurons - Neurotransmitters, Dopamine
Inhibitory
Allows feelings of pleasure and reward
Communication between Neurons - Neurotransmitters, Serotonin
Inhibitory
Communication between Neurons - Neurotransmitters, Acetylcholine
Excitatory
Allows motor control and coordination
Communication between Neurons - Neurotransmitters, GABA
Inhibitory
Communication between Neurons - Neurotransmitters, Glycine
Inhibitory
Communication between Neurons - Neurotransmitters, Glutamate
Excitatroy
Communication between Neurons - Neurotransmitters, Norepinephrine
Excitatory and Inhibitory
Communication between Neurons - Neurotransmitters, Effects of Drugs, Epilepsy
Epilepsy is a result of overexcitation
Anti-epileptics reduce excitation
Phenytoin binds to Na+ channels, blocking them from opening, meaning that Na+ cannot enter the cell and depolarise the membrane
Topiramate antagonises glutamate so it cannot excite neurons, blocks Ca2+ channels so they cannot stimulate the release of neurotransmitters into synaptic clefts
Clonezepam agonises GABA resulting in more inhibited impulses
Communication between Neurons - Neurotransmitters, Effects of Drugs, Mental Health
Increased dopamine levels result in schizophrenia, tourettes, OCD and mania
Decreased dopamine levels result in ADHA, depression and Parkinson’s
Communication between Neurons - Neurotransmitters, Effects of Drugs, Addiction
Addictive substances tend to stimulate the nucleus accumbens
This increases dopamine levels, increasing feelings of pleasure and decreases GABA resulting in increased excitation
Communication between Neurons - Neurotransmitters, Effects of Drugs, DOPA
Increases dopamine levels
Used to treat Parkinson’s
Communication between Neurons - Neurotransmitters, Effects of Drugs, Cocaine
Increases serotonin, dopamine and norepinephrine
Communication between Neurons - Neurotransmitters, Effects of Drugs, Methyletalymine / Ritaline
Blocks reuptake of neurotransmitters resulting in slowed elongated excitation
Used to treat ADHD
Communication between Neurons - Neurotransmitters, Effects of Drugs, Amphetamine
Increases dopamine
Communication between Neurons - Neurotransmitters, Effects of Drugs, Antipsychotics
Block dopamine receptors
Communication between Neurons - Neurotransmitters, Effects of Drugs, Alcohol
Antagonises Na+ channels, serotonin and glutamate
Agonises dopamine and GABA
Together these reduce responsivity due to enhanced inhibitory impulses, and associates with pleasure but acts as a depressant
Communication between Neurons - Neurotransmitters, Loewi
Conducted a study with frog heart
Heart A was electrically stimulated in Beaker A
Heart A was removed from Beaker A and replaced with Heart B
Heart B showed activity despite no stimulation
Supports that there must have been a chemical released by Heart A that remained in Beaker A to stimulate Heart B
Communication between Neurons - Neurotransmitters, Sherrington
Conducted research on reflexes and summation
Measured that transmission within neurons took place at 40 m / s
Transmission between neurons took place at 5 m / s
The difference in speed indicates that the mechanisms of communication differ for between and within neurons
