Sensory Receptors Flashcards
Name six types of sensory receptors and their functions
Mechanoreceptors respond to mechanical stimuli such as touch, hearing, balance and blood pressure.
Proprioreceptors sense where the body and limbs are and they’re found in joints and muscles.
Nocireceptors detect pain and heat.
Thermoreceptors detect cold and warmth.
Chemoreceptors respond to changes in pH and chemical changes.
Photoreceptors respond to different wavelengths of light.
What is the frequency coding of stimulus intensity?
This means the that the larger the stimulus, the larger the receptor potential so the higher the frequency of Action Potentials in a sensory nerve.
What is adaptation?
Some mechanoreceptors only respond to changes in stimulus instead of responding to a long term stimulus. Different receptors show different levels of adaptation.
What receptors show no adaptation?
Nocireceptors are free nerve endings that don’t adapt as it’s important to feel pain.
What receptors are fast adapting and what are slow adapting?
Merkel receptors which detect steady pressure and texture and ruffini corpuscle which detects stretch are slow adapting receptors.
Meissner’s corpuscle responds to flutter and strokes and pacinian corpuscle senses vibration are both rapid adapters.
What structure of the pacinian corpuscle is important for adaptation?
The non neuronal part or the capsule is important as it changes the structure of the fluid to dissipate the mechanical stretch of the nerve ending.
What affects the ability to determine between two points on the skin?
Two things affect this and they are the receptor field and convergence of sensory Neurons.
The receptor field is the specific area that a somatic sensory neurone is activated by.
Convergence is when multiple presynaptic neurones synapse onto less postsynaptic neurones which allows a sum of threshold to form a large secondary receptor field.
A large receptive field and convergence means an insensitive area.
What is acuity?
The ability to locate a stimulus on the skin and tell it apart from another closeby.
What is lateral inhibition?
It’s when a primary neuron senses a stimulus and sends it to secondary neurones which inhibit others beside it so that the tertiary neurones are also inhibited so the perception of the stimulus is enhanced. This allows sharpening of the signal and allows for more precise locating.
Where does all sensory information go?
It goes to the brain via the thalamus to the somatosensory cortex. The most sensitive areas occupy the most cortical space.
Name three types of proprioreceptors and what they do
Muscle spindles monitor muscle length and the rate of change of muscle length so control reflexes and voluntary movement.
Golgi tendon organs monitor tension on tendons and muscles.
Joint receptors monitor joint angle, rate of angular movement and tension on the joint.
What are intrafusal muscle fibres?
These are muscle fibres contained within a connective tissue capsule and they have specialised sensory and motor function.
What are two types of intrafusal fibres?
Nuclear bag fibres which are bag shaped and have all the nuclei together.
Nuclear chain fibres that have their nuclei lined up in a chain.
How do muscle spindles and GTOs lie next to the extrafusal muscle fibres?
Muscle spindles lie parallel and GTOs in series.
Describe the comings and goings of the CNS to the muscle spindles
Sensory neurones come from the intrafusal fibres to the CNS.
Alpha motor neurones come from the CNS and attach to extrafusal muscle fibres to innervate them.
Gamma motorneurones innervate the contractile ends of intrafusal fibres so when they shorten the ends of the fibre the central area gets stretched.
