Neuronal Communication 5.3 -by J + M Flashcards
Name 4 receptors and state where they are found/ what stimulus they receive
Mechanoreceptors-skin/ touch
Photoreceptors-eyes/ light
Chemoreceptors-aorta and carotid artery/ pH
Thermoreceptors-skin, hypothalamus/ temperature
Describe the structures of the three different types of neurons
SENSORY- receptor, dendron, cell body, axon
RELAY- dendrites, cell body, axon, pre-synaptic terminal
MOTOR-dendrites around cell body, axon with nodes of ranviers, axon terminal
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What value is the resting potential
-60mv
What value is the threshold potential
-50mv
At what value does the membrane become depolarised
+40mv
What value is the membrane REpolarised?
-70mv
What is it called if the value is more negative than -70mv
HYPERpolarised
When is the axon polarised and what does it mean?
At resting potential, the axon is polarised; meaning that inside the membrane is more negative than outside
Name 5 specialised features of NERVES
Long Voltage gated ion channels NA+/K+ co-transporter pump Potential difference of -70mv inside compared to outside All organelles in cell body
What is a pacinian corpuscle?
What is its structure?
A pressure sensor that detects changes in pressure on the skin.
-oval-shaped
-concentric rings of connective tissue wrapped around the end of the nerve cell
When pressure deforms the rings they push against the nerve ending. If the pressure is constant, they stop responding.
What are transducers?
A cell which converts one form of energy into another
What is a generator potential?
The depolarization of the membrane of the receptor cell
How is the resting potential created?
Sodium/potassium pump actively transports 3Na+ out of the cell for 2K+ going into the cell.
This means that the charge inside the cell is lowered compared to the charge outside of the cell.
This is increased by potassium channels which allow the build-up of 2K+ to move out of cell down the concentration gradient, making the cell even more negative.
Negative anions reduce the resting potential further
What does it mean when the neurone is polarised?
It is at its resting potential, which is -60Mv, or the inside of the neurone is more negative than the outside.
What is depolarisation?
When the inside of the cell becomes less negative compared to the outside.
How does depolarization occur?
A stimulus (change in energy levels of the environment) cause sodium channels open, causing sodium to move down the concentration gradient, into the cell making it less negative and depolarised.
How is an action potential created?
When a stimulus creates a generator potential, sodium channels open to make the neurone less negative.
If enough generator potentials combine, enough sodium will enter the neurone to raise the potential above the threshold potential and trigger an action potential.
This triggers the voltage-gated sodium ion channels to open and sodium floods in raising the potential to +40
Summarise the stages of the action potential in 5 steps.
1) Sodium-ion channels open and some sodium flows down concentration gradient into the neurone
2) The Neurone becomes depolarised, it reaches the threshold potential (-50Mv) when the voltage-gated ion channels open
3) Sodium comes flooding in raising the potential to +40 Mv inside the cell. Positive feedback causes more VG sodium channels to open
4) The Sodium ion channels close and potassium channels open, so K+ comes flooding out of the cell, lowering the potential back down.
5) Potential overshoots making the cell hyperpolarised.
How is an action potential passed down a neurone?
The movement of sodium into the neurone causes the VG sodium channels to open.
This increases the concentration of sodium further, and sodium diffuses down the neurone to where concentrations are lower. This is called a Local Current.
This raises the Potential of that section, causing the VG gated sodium channels in that section to also open.
What is a Local current?
The sideways movement of sodium along a neurone.
What is saltatory conduction?
When the action potential jumps between nodes of Ranvier, as ions cant pass through the myelin sheath.
How and why does saltatory conduction occur?
For an action potential to be passed along a neurone, ions need to pass through the cell membrane.
As ions cant pass through the fatty myelin sheath, this can only occur at the nodes of Ranvier.
This means the sodium ions have to diffuse from one node to another.
This means the action potential appears to jump from one node to the next.
What is the advantage of saltatory conduction?
Forcing the action potential to jump between nodes enables faster transmission.
This is why myelinated neurones can transmit a signal faster than non-myelinated.
How does our brain detect the different intensities of stimuli?
When a stimulus is at a higher intensity, more sodium channels are opened in the sensory receptor.
This produces more generator potentials, so there are more frequent action potentials.
Your brain interprets a higher frequency of action potentials as an increase in the intensity of the stimuli.
What is the name of the gap between two synapses?
Synaptic cleft
about 20 nm wide
What is a cholinergic synapse?
A Synapse which uses acetylcholine as a neurotransmitter.
What is a neurotransmitter?
A chemical used as a signalling molecule between neurones in a synapse.
