Week 3 - Synaptic Transmission & Psychopharmacology Flashcards
What are the basic functions and properties of a relfex arc?
Reflexes are automatic muscular responses to stimuli.
The CIRCUIT from SENSORY NEURON to MUSCLE RESPONSE is called a reflex arc.
Are reflexes slower or faster than conduction along an axon?
SLOWER.
Do several weak stimuli presented at nearby places or times produce a stronger or weaker reflex than one stimulus alone?
STRONGER.
What was Sherringtons’s evidence for synaptic delay?
The speed of conduction long an axon is about 40m/s, but the speed of conduction through a reflex arc is slower and more variable, sometimes 15m/s or less. He presumed the delay occurs at the synapse.
What is the term used to describe the cumulative effect of repeated stimuli within a brief window?
Temporal (over time) Summation.
Are action potentials always depolarisations?
Yes.
Are graded potentials either depolarisations (excitatory) or hyperpolarisations (inhibitory)?
They can be either.
What is a graded depolarisation known as?
An Excitatory postsynaptic potential (ESPS). It results from a flow of sodium ions into the neuron.
What is known as summation over space?
Spatial summation.
Do temporal and spatial summation occur together or separately?
They normally occur together.
Can summation effects depend on the order of stimuli along a dendrite?
Yes! Greater depolarisation would occur if signals begin at the furthest distance along the dendrite and signals continued to be sent at closer and closer points along the dendrite. The opposite is true for signals beginning closest to the soma and moving away, down the dendrite.
What does hyperpolarisation within a cell produce?
An inhibition. It increases the negative charge within the cell, moving it farther from the threshold and decreasing the probability of an action potential.
What is the temporary hyperpolarisation of a cell called?
An Inhibitory Postsynaptic Potential (IPSP)
Is the speed and strength of all synapses the same?
No, they can vary in speed, strength, their combined effects can equal more (or less) than the sum of their signals, and certain combinations of synapses summate with one another more strongly than others do.
Most neurons have a ….., which is a periodic production of action potentials even without synaptic input.
Spontaneous firing rate.
What was Sherrington’s false assumption regarding transmission of signal through a neuron?
He assumed it was too fast to be chemical, and thought it must be electrical.
What happens at the presynaptic terminal that allows the release of neurotransmitters into the synaptic cleft?
Calcium enters the presynaptic terminal via an action potential, releasing neurotransmitters from the terminals into the cleft.
What happens to neurotransmitters after they have separated from their receptors?
They may be taken back into the presynaptic neuron for recycling or they may diffuse away.
Which neurotransmitters are those within the Amino Acid group?
Glutamate, GABA, Glycine, Aspartate, others.
Which neurotransmitter is a modified amino acid?
Acetylcholine
Which are the monoamines?
Serotonin, dopamine, norepinephrine, epinephrine
Which are the neuropeptides?
Endorphins, substance P, neuropeptide Y, many others
Which are the Purines?
ATP, adenosine, maybe others.
Which are the Gases?
NO (nitric oxide), maybe others
What is a neurotransmitter?
A chemical.
What does nitric oxide do?
As a neurotransmitter, it dilates blood vessels nearby increasing bloodflow to the brain and influences other neurons.
How do neurons synthesise neurotransmitters?
Nearly all neurotransmitters are synthesised from amino acids, which the body obtains from proteins in the diet.
What are vesicles?
Tiny spherical packets for neurotransmitter molecule storage in the pre-synaptic terminal.
Where does neurotransmitter synthesis occur?
Mostly at the presynaptic terminal.
Is there any neurotransmitter outside the vesicle?
Yes, the presynaptic terminal also maintains much neurotransmitter outside the vesicles.