C2.2 Neural Signalling Flashcards
What are neurons?
Neurons are highly specialized cells that pass nerve impulses from cell to cell
What is a nerve impulse?
A nerve impulse is an electrical signal passed from cell to cell
What is membrane potential?
Membrane potential is voltage created by an imbalance of charges on either side of the membrane
What is our resting membrane potential?
Our resting membrane potential is 70 mV
Describe the ions during our resting membrane potential…
-Sodium ions are on the outside
-Potassium ions are on the inside
What does a sodium potassium pump do?
-A sodium potassium pump establishes membrane potential
-It actively pumps sodium ions out of the axon and potassium ions into the axon
What is depolarisation?
Depolarisation is when the membrane potential goes from negative to positive due to sodium ions diffusing into the axon
What is repolarisation?
Depolarization is when membrane potential goes from negative to positive due sodium channels closing and potassium ions diffusing out of the axon
How does a nerve impulse pass along an unmyelinated neuron?
- Voltage-gated Na+ channels open
- Na+ ions diffuse into the axon, increasing membrane potential
- If threshold potential is reached more Na+ channels open with more Na+ ions diffusing into the axon
- Depolarisation
- Voltage-gated Na+ channels close, voltage gated K+ channels open
- K+ ions diffuse out of the axon
- Repolarisation
- Sodium potassium pump re-established membrane potential by actively pumping Na+ ions out and K+ ions into the axon
What is the function of myelin sheath?
The function of the myelin sheath is to increase the speed of transmission along the axon by saltatory conduction
What is a synapse?
A synapse is the gap between two neurons
What are NT?
NT are chemicals released by exocytosis into the synapse
Explain how communication between neurons during synaptic transmission is achieved through NT?
- NT are chemicals released by exocytosis after a nerve impulse arrives
- NT are released into the synapse by exocytosis
3.NT bind to receptors at the postsynaptic neuron - NT are broken down
- Excitatory NT cause action potential
- Inhibitory NT prevent threshold potential being reached
Explain how synaptic transmission works?
- Membrane potential reaches end of presynaptic neuron
- Ca+ voltage gated channels open
- Ca+ diffuse into the presynaptic neuron via facilitated diffusion
- Ca+ cuase vesicles full of NT to fuse with the membrane
- NT get released into the synapse by exocytosis
- NT diffuse across the synapse
- NT bind to receptors at postsynaptic neuron
8.This causes voltage gated Na+ channels to open - Na+ ions diffuse into the axon
- If enough Na+ ions enter, action potential initiates
- NT get removed from receptor