Neurons and action potentials Flashcards
What is the Soma of a neuron?
Cell body which contains the nucleus.
What is the dendrites of a neuron?
A branched treelike structure attached to the soma, receives information from the terminal button of other neurons.
What is the axon of a neuron?
The long cylindrical structure that conveys information from the soma to the terminal buttons.
What are terminal buttons?
The bud at the end of a brach of an axon forms synapses with another neuron and sends information to it.
What is a synapse?
A junction between the terminal buttons of one axon and the membrane of another neuron.
What is a neurotransmitter?
Chemicals released by terminal buttons and can have excitatory and inhibitory effects on other neuron action potentials.
What are Glial cells?
Cells in the nervous systems that form the myelin sheaths.
What are myelin sheaths?
A sheath that surrounds an axon and insulates then preventing spreading signals between adjacent axons.
What are nodes of ranvier?
Gaps between the myelination which speeds up conduction.
How fast are AP with myelination?
260MPH
How small are neurons in the CNS?
5-100 microns
1 micron = 1/1000mm
What are used to measure neural signals?
Microelectrodes
What do recording and referencing electrodes do?
Recording goes inside the nerve fibre and referencing goes outside, the difference in charge is measured.
Which charges do sodium, potassium and chlorine have?
Sodium- Positive
Potassium- Positive
Chloride- Negative
When do action potentials occur?
- When permeability changes
- When NA+ flows into the fibre
- When K+ flows out of the fibre
Briefly what happens in depolarisation?
-When threshold is met sodium channels open increasing sodium level and causing depolarisation. When it reaches its peak sodium channels close.
What is the resting potential?
-70mv
What is the depolarisation charge?
+40mv
Briefly what is repolarisation?
Potassium channels open at the peak of depolarisation as the sodium channels close causing a decrease in potential.
What is hyperpolarisation?
Occurs during repolarisation in which too much potassium inside the neuron and the charge overshoots and becomes too negative.
What is the refractory period?
Occurring after hyperpolarisation the sodium potassium pump restores the membrane to rest of -70mv, during this period no other action potentials can occur.
Why is the refractory period important?
Allows the signal to travel along the axon as the delay of 1ms prevents the signal from travelling backwards.
What does acetylcholine do?
Regulates motor control, contributing to attention, learning, sleep and memory. E.g. they deteriorate in Alzheimer’s patients.
What does dopamine do?
Influences movement, motivation, emotional pleasure and arousal. e.g. high levels are linked to schizophrenia and low produce tremors in mobility diseases such as Parkinson’s.
What does glutamate do?
A major excitatory neurotransmitter involved in learning and memory. Over supply can overstimulate brain causing migraines or seizures.
What does GABA do?
The primary inhibitory neurotransmitter, undersupply linked to seizures and insomnia.
What is noradrenaline?
Helps control mood and arousal, undersupply can depress mood.
What is seretonin?
Regulates hunger, sleep, arousal and aggression. E.g. Undersupply links to depression.
What do antidepressants do?
Raise seretonin levels.
What do endorphins do?
Act within the pain pathway and emotional centres of the brain, lack of could lower pain threshold and reduce the ability to self-soothe.
What are excitatory neurotransmitters?
They cause depolarisation, the neuron becomes more positive and is more likely to reach the threshold to cause an action potential.
What are inhibitory neurotransmitters?
They cause hyperpolarisation, neuron becomes more negative and decreases the likelihood of an action potential via reaching the threshold.
What is reuptake?
When a synapse is deactivated by the neurotransmitters being taken back up and recycles to the vesicles in the presynaptic neuron.
What is presynaptic auto-receptors?
The stopping of a release of the neurotransmitters before they diffuse across the membrane.
What is enzymatic degradation?
The neurotransmitters being broken down by enzymes to deactivate the synapse.
