Neuron Biology Flashcards
What are the 4 basic elements in the structure of a neuron?
- Dendrite - recieves signals
- Soma - processes information
- Axon - transmits between neurons
- Synapse - point of connection between neurons.
Describe the structure and function of the Dendrite? (3)
- Tree like structure that gathers input from surrounding neurons.
- Mushroom shaped spines cover the dendrite and recieve input from other axons.
- Recieved signals travel to the SOMA.
Describe the structure and function of the Soma? (2)
- Soma houses the DNA of the neuron.
- Accumulates signals from dendrites and causes the nueron to fire down the axon if they exceed a threshold. This occurs in the axon hilock.
Describe the structure and function of an Axon?
- An axon is a tube-like nerve fiber that carries signals to the axon terminals.
- Axons coated in myelin are protected and their signals travel faster.
What are the three classes of neuron?
- Sensory Nuerons
- Motor Neurons
- Relay Neurons
What is the role of sensory neurons?
Tell the brain what is happening outside the body.
What is the role of Motor Neurons?
Allow the brain to control muscles
What are the role of relay neurons?
Allow sensory and motor neurons to communicate.
What are the main parts of the CNS?
The brain and spinal cord.
What is the cell membrane of an Axon?
The cell membrane of an axon is a double layer of lipids which sperates the inside of the cell with the outside.
What is the membrane potential?
Ions on either side of the membrane are unequally distributed causing a potential.
What is the resting potential?
The potential across the membranes which do not cause the neuron to fire. Typically (-70mV)
What are the membrane channels?
Allow ions to travel from one side of the membrane to another
What are leaky channels?
Always open and allow sodium and pottasium ions through.
What are voltage gated channels?
Only open when the voltage is high enough. Normally closed at resting potential.
Why is resting potential -70mV instead of 0?
- There are more pottasium ions in the cell which allows pottassium ions to travel through the pottasium leaky channels easier.
- There is a sodium potassium pump which uses energy to move three sodium ions for ever 2 pottasium ions.
What is an action potential?
The change in potential which travels across the neuron. Occurs at -55mV.
What is the All-or-None law?
Subthreshold stimulus will cause no excitation. Superthreshold stimus will cause full excitation.
What is polarisation?
If the outside of the membrane is positive and the inside is negative.
What is HyperPolarisation?
If the membrane potential is more negative than resting.
what is depolarisation?
if the membrane potential is more positive than resting.
What are the 6 steps of action potential?
- Initially at resting potential, volted gated channels are closed.
- Stimuli causes some volted gated channels to open.
- Sodium channels open, causes sodium to rush into the cell causing depolarisation as voltage exceeds 30mv.
- Voltage gated sodium channels close.
- Pottassium channels open, causing repolarisation to occur as pottasium leaves the cell.
- Sodium and pottassium pump restore the resting potential.
What is a synapse?
Junction between nerve/muscle cells.
Describe Synaptic transmission?
- When the presynaptic neuron is exicted by an action potential.
- Vesicles in the axon terminals release neurotransmiiters into the synaptic cleft.
- Some neurotransmitters will bind to receptors in the postsynaptic cell causing some effect. (some nuero transmitters are excitory or inhibitory.)
Describe the types of synaptic connections?
- Axodendritic - axon terminal links to dendrite
- Axosomatic - axon terminal links to the soma.
- Axoaxonal - axon terminal links to axon.
- Dendrodendrititc - Dendrite links to dentrite.
