AQA A Level Biology: Receptors Flashcards
What is a receptor?
A specialised cell or protein that detects a stimulus and converts it into a nerve impulse.
What is a stimulus?
A detectable change in the environment that triggers a response.
What are the two types of receptors?
- Cell receptors: Found on the cell surface membrane.
- Sensory receptors: Detect changes in the environment (e.g., in sense organs).
What is the role of receptors in the nervous system?
To convert stimuli into electrical impulses that are transmitted to the central nervous system (CNS).
How does the pacinian corpuscle generate an action potential?
- Pressure deforms the lamellae.
- Stretch-mediated sodium ion channels open.
- Sodium ions diffuse into the neurone.
- If the threshold is reached, an action potential is triggered.
What is a stretch-mediated sodium channel?
A sodium ion channel that opens when the membrane is stretched or deformed.
Where are pacinian corpuscles located?
In the skin (especially fingers, soles of feet) and around joints.
What is the fovea?
A region in the retina with a high concentration of cone cells for sharp, detailed vision.
What are photoreceptors?
Cells in the retina that detect light and convert it into electrical impulses.
What are the two types of photoreceptors?
- Rod cells: Detect low light levels, black and white vision.
- Cone cells: Detect colour and detail in bright light.
What is the pigment found in rod cells?
Rhodopsin – a light-sensitive pigment that breaks down when exposed to light, generating an action potential.
What is the pigment found in cone cells?
Iodopsin – different forms detect red, green, and blue light.
Why do rod cells have high sensitivity?
Many rod cells synapse with a single bipolar neurone, allowing spatial summation to increase the likelihood of reaching the threshold.
Why do rod cells have low visual acuity?
Multiple rod cells share the same neurone, so the brain cannot distinguish between individual points of light.
Why do cone cells have high visual acuity?
Each cone cell is connected to a single bipolar neurone, allowing precise detection of separate points of light.
Why do cone cells have low sensitivity?
They require high light intensity to break down iodopsin, so they are less effective in dim light.
What is the role of the optic nerve?
Transmits electrical impulses from the retina to the brain for processing.
What is the autonomic nervous system?
The part of the nervous system that controls involuntary actions.
What are the two divisions of the autonomic nervous system?
- Sympathetic nervous system: Prepares the body for fight or flight.
- Parasympathetic nervous system: Returns the body to a resting state.
What is the role of the parasympathetic nervous system?
Reduces heart rate, promotes digestion, and conserves energy.
What is the role of the sympathetic nervous system?
Increases heart rate, dilates pupils, and prepares the body for action.
What is the role of the medulla oblongata?
Controls heart rate by sending impulses to the SAN via the autonomic nervous system.
What are baroreceptors?
Pressure receptors that detect changes in blood pressure and send impulses to the medulla.
What are chemoreceptors?
Receptors that detect changes in pH due to CO₂ levels and regulate breathing and heart rate.
How does the body respond to high blood pressure?
- Baroreceptors detect increased pressure.
- Parasympathetic nerves send impulses to decrease heart rate.
How does the body respond to low blood pressure?
- Baroreceptors detect decreased pressure.
- Sympathetic nerves send impulses to increase heart rate.
How does the body respond to high CO₂ levels?
- Chemoreceptors detect lower pH.
- Sympathetic nerves send impulses to the SAN to increase heart rate.
How does the body respond to low CO₂ levels?
- Chemoreceptors detect higher pH.
- Parasympathetic nerves send impulses to the SAN to decrease heart rate.
