Flashcards in Roles of Sensory Receptors Deck (22):
What is a pacinian corpuscle?
A pressure sensor found in the skin
What are sensory receptors?
Cells/sensory nerve endings that respond to a stimulus in the internal or external environment in an organism and can create action potentials.
Specialised cells that can detect changes in our surroundings, most are energy transducers that convert one form of energy to another.
What is a transducer?
A cell that converts one form of energy into another - in this case to an electrical impulse.
What is a stimulus?
A change in the environment, whether that's a change in the energy level or the presence of a new chemical.
If the stimulus is a change in light intensity. What is the sensory receptor and what is the energy change involved?
Light sensitive cells (rods and cones) in the retina.
Light to electrical.
If the stimulus is a change in pressure of the skin. What is the sensory receptor and what is the energy change involved?
Pacinian corpuscles in the skin.
Movement to electrical
If the stimulus is chemicals in the air. What is the sensory receptor and what is the energy change involved?
Olfactory cells in epithelium lining the nose.
These receptors detect the presence of a chemical and create an electrical nerve impulse.
Describe the structure of a pacinian corpuscle.
The corpuscle is an oval-shaped structure that consists of a series of concentric rings of connective tissue wrapped around the end of a nerve cell.
What happens to the pacinian corpuscle when pressure on the skin changes?
When pressure on the skin changes this deforms the rings of connective tissue, which push against the nerve ending.
What happens when pressure on the skin is constant?
They stop responding as the pacinian corpuscle only responds to changes in in pressure.
Cells associated with the nervous system have specialised channels in their membranes. What are they?
Sodium channels specific to sodium ions.
Potassium channels specific to potassium ions.
What are the sodium channels sensitive to?
Small movements of the membrane.
What does the sodium channel do if the membrane becomes deformed? What happens as a result?
The sodium ion channels open.
This allows sodium ions to diffuse into the cell, producing a generator potential (also called a receptor potential).
What do sodium/potassium pumps do?
They actively pump sodium ions out of the cell and potassium ions into the cell.
What is the number of sodium/potassium ions pumped in/out?
Three sodium ions are pumped out for every two potassium ions pumped in.
What is the result of the ionic movements of sodium and potassium?
The cell is negatively charged inside compared with the outside. The negative potential is enhanced by the presence of negatively charged anions inside the cell.
What is the membrane said to be when it is inactive?
Polarised. Negatively charged inside compared with the outside.
How is a nerve impulse created?
By altering the permeability of the nerve cell membrane to sodium ions. This is achieved by opening the sodium ion channels. As the sodium ion channels open, the membrane permeability is increased and sodium ions can move across the cell membrane down their concentration gradient into the cell.
What does the movement of sodium ions into the cell cause?
Creates a change in the potential difference (charge) across the membrane. Inside of the cell becomes less negative than the outside of the cell compared to normal. This is called depolarisation.
What is depolarisation?
When the inside of the cell becomes less negatively charged than the outside of the cell compared to normal.
What happens if a small stimulus is detected?
Only a small number of sodium channels will open.