Lesson 2: Neural Signalling Flashcards
Cell body
Contains the nucleus and large amounts of rough endoplasmic reticulum for protein and neurotransmitter production.
Dendrites
Short, branched fibers that receive incoming signals and carry them toward the cell body.
Axon
A single, long fiber that carries electrical impulses away from the cell body.
Schwann Cells
Surround the axon, forming the myelin sheath, which provides electrical insulation and aids in nerve regeneration.
Myelin Sheath
A lipid-rich layer that speeds up signal transmission.
Nodes of Ranvier
Gaps in the myelin sheath enabling faster signal transmission through saltatory conduction.
Resting Membrane potential
sodium potassium pump pumps 3 sodium ions out and 2 potassium ions in using ATP.
The membrane is more permeable to potassium ions, so some potassium ions leak out.
There are negative proteins inside the cell contributing to a membrane potential of -70 mV.
Depolarisation/ action potential
A stimulus opens sodium ion channels, allowing sodium ions into the cell.
A threshold potential of -50 mV is reached, opening the voltage-gated sodium ion channels.
Axon rapidly depolarises to +40 mV and an action potential is created.
Repolarisation
Voltage-gated sodium ion channels close and voltage-gated potassium ion channels open.
Potassium ions leave. The potassium ion channels take a long time to close leading to hyper-polarisation.
Axon returns to resting potential.
what is hyperpolarisation?
The membrane becomes slightly more negative than the resting potential.
How do signals travel?
As local currents - sodium ions diffuse laterally, depolarizing adjacent regions of the membrane.
Saltatory Conduction
Action potentials “jump” between nodes of Ranvier, speeding up transmission.
Factors Affecting Speed
Myelination:
Myelinated fibers conduct signals faster than unmyelinated ones.
Axon Diameter:
Larger axons have less resistance, allowing faster signal propagation.
Temperature:
Higher temperatures increase the speed of transmission.
What is a Synapse?
The gap between two neurons or a neuron and an effector cell.
Steps in Synaptic Transmission
An incoming action potential causes calcium ion channels to open in the pre-synaptic membrane.
Calcium ions enter the synaptic knob.
Calcium ions influx triggers synaptic vesicles to fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.
Neurotransmitters bind to receptors on the postsynaptic membrane, opening sodium ion channels.
Sodium ions enter, causing depolarization.
If the threshold is reached, a new action potential is generated in the postsynaptic neuron.
What is the difference between excitatory and inhibitory synapses?
Excitatory synapses depolarize the postsynaptic membrane, while inhibitory synapses hyperpolarize it, making action potentials less likely.
What is the refractory period?
The hyper-polarisation stage.
what causes action potentials to travel in one direction?
the refractory period
Example of inhibitory synapses
Glutamate
Example of excitatory synapses
GABA
name 3 receptors on the skin and their functions
Nociceptors: detect pain.
Thermoreceptors: detect temperature changes.
Pacinian Corpuscles: detect deep pressure.
How does cocaine affect synaptic transmission?
It blocks the reuptake of dopamine, causing amplified signals in the postsynaptic neuron.
