13.3 Sensory receptors Flashcards
(22 cards)
What does the body use to detect changes in its environment?
Specialised group of cells - sensory receptors
Where are sensory receptors often located?
Sense organs, e.g. ear and eye
What do sensory receptors do with a stimulus?
Convert the stimulus into a nerve impulse
What happens after the sensory receptor converts a stimulus into a nerve impulse?
The information is passed through the nervous system and into the CNS, usually the brain
What does the brain do after the sensory receptor converts a stimulus into a nerve impulse?
The brain coordinates the respnse and sends an impulse to an effector (muscle/gland) to provide the desired response
What are the 2 main features of a sensory receptor?
- Specific to a single type of stimulus
2. Act as a transducer - converts a stimulus into a nerve impulse
Name the 4 types of sensory receptors.
Mechanoreceptor
Chemoreceptor
Thermoreceptor
Photoreceptor
What are the characteristics of the mechanoreceptor?
Stimulus: Pressure and movement
Example of receptor: Pacinian corpuscle (detects pressure)
Example of sense organ: Skin
What are the characteristics of the chemoreceptor?
Stimulus: Chemicals
Example of receptor: Olfactory receptor (detects smell)
Example of sense organ: Nose
What are the characteristics of the thermoreceptor?
Stimulus: Heat
Example of receptor: End-bulbs of Krause
Example of sense organ: Tongue
What are the characteristics of the thermoreceptor?
Stimulus: Light
Example of receptor: Cone cell (Detects light wavelengths)
Example of sense organ: Eye
What do sensory receptors detect?
A range of stimuli e.g. light, heat, sound or pressure
What does the receptor convert the stimulus into?
A nervous impulse, called a generator potential
Give an example of a receptor responding to stimuli?
A rod cell (in eye) responds to light and produces a generator potential
What are pacinian corpuscles?
Sensory receptors that detect mechanical pressure
Where are pacinian corpuscles located?
- Deep within skin, most abundant in fingers + soles of feet.
- Within joints, enabling you to know which joints are changing direction.
What is in the centre of the corpuscle and what is it surrounded by?
The end of a sensory neurone, sourrounded by connective tissue.
Each tissue layer is separated by a gel layer.
What can be found in the membrane of the sensory neruone?
Sodium ion channels
What is the role of the sodium ion channels in the membrane of the neurone?
To transport sodium ions across the membrane
What’s special about the neurone ending in a Pacinian corpuscle?
It has a sodium channel called a ‘stretch-mediated sodium channel’
What happens to stretch-mediated sodium channels when they stretch?
Their permeability to sodium changes
Describe the 5 step process of how a Pacinian corpuscle converts mechanical pressure into a nerve impulse?
- In its resting state, the stretch-mediated sodium ion channels, in the sensory neuron membrane, are too narrow to allow sodium ions to pass through them.
The neurone of the Pacinian corpuscle has a resting potential. - When pressure is applied to the Pacinian corpuscle, the corpuscle changes shape.
This causes the membrane surrounding the neurone to stretch. - When the membrane stretches, the sodium ion channels widen.
Sodium ions can now diffuse into the neurone. - The influx of positive sodium ions changes the potential of the membrane - the membrane becomes depolarised.
This results in a generator potential. - The generator potential creates an action potential (nerve impulse) that passes along the sensory neurone.
The action potential will then be transmitted along neurones to the CNS.
