- Created by: Rachelezy
- Created on: 13-02-20 10:44
Types of Receptors (Basics)
- Detect changes in light
- e.g. Pacinian Corpuscle detect mechanical stimuli in the form of pressure and vibration
- Found in joints, tendons, and ligaments (also fingers, soles of feet and external genitalia)
- Contain a single sensory neurone located in lamellae (connective tissue) which forms layers separated by a gel.
Contains stretch mediated sodium channels in the cell surface membrane:
- When not under pressure, these channels are closed - Under pressure these become deformed
- They open and allow the rapid influx of sodium ions to occur.
- Positive charge on the sodium ions changes the membrane potential, causing the membrane to become depolarised
- Results in a generator potential being generated which goes on to create an action potential in the axon.
Photoreceptors in the eye (Overview)
- Light receptors in the eye
- Light enters through the pupil and amount of light entering is controlled by muscles in the iris.
- Lens of the eye focuses the light on the retina (this is where photoreceptors are located, more specifically the fovea)
- Nerve impulses then carried via the optic nerve to the brain
Blind Spot - Point where the optic nerve leaves the eye (no photoreceptor cells are located here)
Photoreceptors in the eye (Rod and Cone Cells)
- Involved in colour vision
- Present at the greatest density in the fovea
- Contain the pigment iodopsin
- Not sensitive to light so require quite bright light to work
- Contains three different primary pigments (red, blue and green)
- Provide good visual acuity as each cone cell has its own synapse via a bipolar neurone which connects to the optic sensory neurone
- Mainly concentrated in highest density outside of the fovea
- Very sensitive to light - are stimulated by low light conditions
- Provide low visual acuity because more than one rod cell shares the same synapse with a bipolar cell - multiple rods have to be stimulated in order for a generator potential to occur.
Simple Reflex Arc
Stimulus --> Receptor --> Sensory neurone --> Intermediate (relay) Neurone --> Motor Neurone --> Effector --> Response
Sensory Neurone - Carries nerve impulse from the receptor to the spinal cord
Intermediate (relay) Neurone - Located entirely in spinal cord and relays the nerve impulse from sensory neurone to the motor neurone
Motor Neurone - Carried nerve impulse from the spinal cord to the effector (can be a muscle or gland)
Reflex that bypasses the brain