Neuroscience Lecture 1 Flashcards
What are a Neurone’s properties?
EXCITABILITY- Ability to RESPOND to STIMULI.
CONDUCTIVITY- GENERATE electrical signals known as ACTION POTENTIALS.
SECRETION- Chemical NEUROTRANSMITTERS are used to bridge gaps at SYNAPSES between neurons.
How many neurones are there in the human brain?
86 billion.
How many connections can an average neurone make?
1000
What is the approximate charge across a membrane?
-70 mV
What is a chemical gradient?
Difference in SOLUTE concentrations across the membrane
What is an electrical gradient?
Difference in CHARGE across the membrane
How does the Na+/ K+ ATPase membrane protein PUMP work to sustain an ion gradient?
The pump pumps out 3 Na+ for every 2 K+ it brings in.
Works CONSTANTLY with the presence of ATP.
To maintain a resting potential.
What is the equilibrium potential of an ion?
Is the point which there would be no net movement of the ion across the membrane.
What is the equilibrium potential of Potassium and Sodium?
EK = -80mV ENa = +60mV
Which ion (Sodium/ Potassium) is the membrane for permeable to? Why?
Potassium, -80mV
The RESTING MEMBRANE POTENTIAL is around -70 mV in neurones.
What is each stage of an action potential?
- Membrane at Rest
- Local Potential
- Depolarisation
- Repolarisation.
- Absolute Refractory Period
- Relative Refractory Period.
- Hyperpolarisation
- Resting state.
Action Potential- Describe the membrane at rest?
At rest the membrane potential is around -70mV. Voltage gated SODIUM and POTASSIUM channels are now CLOSED.
Action Potential- Describe the membrane at its local potential?
Membrane potential RISES because of the opening of LIGNARD GATED ion channels (ion channels).
Do NOT reach threshold= Diminish and no action potential.
Threshold REACHED= Action potential will fire.
Action Potential- Describe the membrane at depolarisation?
Membrane has reached threshold potential.
Potential rises rapidly because VOLTAGE GATED SODIUM ION CHANNELS are OPEN.
Potassium channels remain CLOSED.
Action Potential- Describe the membrane at REPOLARISATION?
Membrane potential has peaked and falls back towards resting potential.
Voltage gated sodium ion channels = INACTIVATED. VOLTAGE GATED POTASSIUM ION CHANNELS = OPEN to bring membrane back to potassium equilibrium.
Absolute Refractivity Period?
Lasts for 1ms.
IMPOSSIBLE to fire ANOTHER action potential.
POTASSIUM CHANNELS= CLOSING.
SODIUM CHANNELS= INACTIVATED.
Relative Refractory Period?
Lasts for SEVERAL MILLISECONDS.
It is possible to fire an action potential, but a LARGER stimuli is required.
Potassium channels = closing.
Sodium channels = DE-INACTIVATED.
What is meant by the All or nothing response?
This principal shows the threshold is either reached and an action potential is produce or it is NOT.
How are action potentials unidirectional?
They travel along the axon and are then followed by the refractory period.
What is myelination? What does myelination do?
MYELINATION is when the neuron axon is INSULATED allowing for more RAPID conduction of the action potential.
What is continuous propagation?
CONTINUOUS PROPAGATION is where an action potential progresses along an UNMYELINATED axon.
What is saltatory propagation?
SALTATORY PROPGATION is where an action potential progresses along a MYELINATED axon.
What are areas without myelin called?
Nodes of Ranvier.
How does the nodes of ranvier allow for faster conduction?
Action potential jumps along these nodes.
How do you increase the speed an action potential travels?
LARGER DIAMETER of axon.
MORE MYELINATION.
What cells myelinated peripheral axons?
SCHWANN cells
What cells myelinated CNS axons?
OLIGODENDROCYTES
What is MULTIPLE SCHLEROSIS (MS)?
Autoimmune disorder when myelination of central nerves is targeted.
What is GUILLAIN- BARRÉ SYNDROME?
Autoimmune disorder when myelination of peripheral nerves is targeted.
At a chemical synapse the pre and post- synaptic elements, what is the gap they are separated called?
SYNAPTIC CLEFT.
Describe the stages of synaptic transmission?
- Action potential OPENS voltage-gated Ca2+ channels in presynaptic membrane.
- Ca2+ ions enter the presynaptic terminal, which TRIGGERS the RELEASE of ACh from vesicles.
- Ach DIFFUSES across the synaptic cleft.
- Ach interacts with Ach receptors which causes OPENS Na+ ion channels so there is an INFLUX of Na+ ions.
- The influx of Na+ ions produces an EPSP (excitatory postsynaptic potential).
- If the EPSP reaches -55mV an action potential is TRIGGERED in the postsynaptic neuron.
What is the main excitatory/ inhibitory neurotransmitter in the brain?
E- Glutamate
I- GABA
Name and give examples of 4 types of Neurotransmitter:
- Amino Acid Neurotransmitters- Glutamate, GABA, glycine.
- Monoamines Neutrotransmitters- Serotonin (5-HT).
- Catecholamines (Also monoamines)- Dopamine, epinephrine, norephrine.
- Peptide neurotransmitters- Substance P, endorphins
What monoamine neurotransmitters deprived from?
Amino acids.
What is the rate determining step of the synthesis of acetylcholine? Is it saturated or not saturated?
Chloline Acetylransferases (ChAt).
Not saturated.
What enzymes are need to produce domaine? Which is the rate determining step?
Tyrosine Hydroxylase (Rate determining step). Dopa Decarboxylase (DDC)
What receptors are used to transport glutamate into the vesicle?
Glutamate VGlut 1 Receptors.
What substrate is used as an example treatment for Parkinson’s Disease, targeting synthesis by providing additional substrate for dopamine production?
L- Dopa.
How are action potentials released?
- Action potential reaches the PRESYNAPTIC terminal.
- VOLTAGE GATED CALCIUM ion channels OPEN.
- INFLUX of Calcium ions.
- Influx of calcium ions cause the vesicles to BIND with the presynaptic membrane.
- Contents of vesicles is RELEASED by EXOCYTOSIS.