Week3 Nervous System Flashcards
The basic building blocks of the nervous system
Neurons
Three main parts of neurons.
Soma: the cell body
Dendrites: specialised receiving units that collect messages from neighbouring neurons and send them onto the cell body
Axons: conducts electrical impulses away from the cell body to other neurons, muscles or glands
Two important functions of neurons
- Generate electricity that creates nerve impulses.
- Release chemicals to communicate with neurons, muscles and glands
Describe resting potential
Neuron is separated from surrounding fluid by a cell membrane ; substances pass through ion channels
Inner ions are more negatively charged than outer ions, resulting in a net negative charge for the resting neuron
(Polarisation)
What is action potential? How does it occur?
Electrical shift that occurs when a neuron is stimulated
Positive sodium ions enter the neuron, causing brief depolarisation
It begins at one end of the axon and moves down along it
When does the absolute refractory period occur? What happen to the membrane during this period?
After the action potential passes along each point on the axon
The membrane is not excitable, and cannot discharge another impulse during this period
What are All or None events
Action potentials occur, either at a uniform, and maximum intensity, or not at all
What are Graded Potentials? What may happen to them?
Changes in the negative resting potential that do not reach the action potential threshold
They may combine to trigger an action potential in certain circumstances
What is myelin sheath? What colour does it have? What does it allow? If damaged, what would happen?
A layer of fatty insulation that surrounds the axon
White
Allows electrical conduction to take place at a higher speed than in unmyelinated axons
Multiple sclerosis
Myelin sheath is completely formed at birth. True or false?
False
In many neurons, the myelin sheath is not completely formed until some time after birth
What are synapses and what is synaptic space?
The conjunction of an axon terminal of one neuron and the membrane of another cell
A tiny gap between the axon terminal, and the next neuron
Five stages of synaptic transmission.
- Synthesis - formation of neurotransmitters
- Storage - transmitter molecules are stored in synaptic vesicles in axon terminals.
- Release - action potential causes transmitter molecules to move from synaptic vesicles across the gap.
- Binding - transmitter molecules find themselves to receptor sites embedded in the post-synaptic neuronal membrane
- Deactivation - broken down of transmitted by other chemicals or reuptake (transmitter molecules are taking back into the pre-synaptic axon terminals)
Two types of chemical reactions that can occur when a neurotransmitter molecule binds to a receptor
Excitatory: causes the action potential to fire
Inhibitory : prevents the neuron from firing
What is Acetylcholine? Underproduction and overproduction causes?
A neurotransmitter involved in muscle activity and memory
Underproduction is involved in Alzheimer’s
Overproduction occurs with black widow spider bites
What are neuromodulators? A best know category?
Chemicals that modulate sensitivity of many neurons to their specific transmitters, exerting behavioural and physiological effects
Endorphins - inhibit pain transmission while enhancing pleasurable feelings
