Nerves (from LOs) Flashcards
Define sensory receptor
Specialised cells that detect changes in our surroundings/ energy trasducers.
Define polarised membrane
A membrane with a potential difference across it.
Define depolarised membrane
When the potential difference has changed so that the inside of the cell is less negative compared to the outside.
Define generator potential
A small depolarisation caused by sodium ions entering the cell.
Was the energy transformation for a light receptor?
Light to electrical
What’s the energy transformation for sound receptors?
Kinetic to electrical
What is the energy transformation that occurs for olfactory receptors?
Chemical to electrical
What is the energy transformation that occurs for taste receptors?
Chemical to electrical
What is the energy transformation that occurs for pressure receptors?
Kinetic to electrical
What is the energy transformation that occurs in pressure sensors?
Kinetic to electrical
Explain how a membrane becomes polarised
Sodium potassium pump;
Actively transporting;
3 sodium ions out of the cell and 2 potassium ions into the cell;
Potassium ions diffuse out but sodium ions do not diffuse in
As the more permeable to potassium ions than sodium ions (sodium channels gated/ closed)
Describe how a sensory receptor converts a stimulus into a nerve impulse.
When stimulus occurs, gated sodium channels open;
Sodium ions diffuse into cell;
Generator potential;
Above threshold value (-50mV) voltage gated sodium channels open
Many sodium ions diffuse in
Membrane depolarises to = 40mV
Action potential initiated.
State the relationship between the size of the stimulus and the number of gated channels which open
The larger the stimulus, the more sodium channels open
Define neurone
A nerve cell
Define nerve
Tissue that consists of neurones
Define CNS
The brain and spinal cord. Has overall control over the coordination of the nervous system.
State the function of a sensory neurone
Carry the action potential from a sensory receptor to the CNS
State the function of a motor neurone
Carry an action potential from the CNS to an effector such as a muscle or gland
State the function of a relay neurone
Connect sensory and motor neurones
Where is the cell body positioned in a sensory neurone?
Just outside CNS
Where is the cell body positioned in a relay neurone?
Inside CNS
Where is the cell body positioned in a motor neurone?
Inside CNS
Does a sensory neurone have a myelin sheath?
Yes (most)
Does a relay neurone have a myelin sheath?
No
Does a motor neurone have a myelin sheath?
Yes ( most)
What structure carries impulses to the cell body?
Dendrites/ dendron
What is the structure that carries impulses away from the cell body?
Axon
What is the length of dendron in sensory neurones?
Long singule dendron from receptor to cell body. Dendrites at end of axon.
