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Flashcards in Sensory Receptors Deck (15):

In cutaneous sensory receptors, the nerve endings

are protected by a capsule


In many cases, the stimulus required to trigger an AP depends on

causing a membrane deformation which activates stretch sensitive ion channels


Stretch sensitive ion channels may be present

in the distal tip of the affront axon or in specialised sensory cells that then release neurotransmitter to create a generator potential in the axon's dendrites


Explain sensory transduction in the skin

The transduction process in all sensory endings involves opening or closing of ion channels


Explain frequency coding

- the bigger the stimulus, the greater the receptor potential and therefore the higher the frequency of APs
- this is the frequency coding of APs
- high frequency = high stimulus intensity


What do muscle spindles monitor?
What is this important for?

Muscle length and the rate at which it changes

Important for reflexes as well as voluntary movement


What fibres is skeletal muscle made up of?

Extrafusal and intrafusal fibres


Extrafusal fibres are

regular muscle fibres


Intrafusal fibres have

specialised motor and sensory innervation from muscle spindles


The end of intrafusal fibres contains

sarcomeres and are contractile


Intrafusal fibres are controlled by

gamma motoneurones


Muscle stretch is the

adequate stimulus for these receptors


As the muscle lengthens,

ion channels open and so length is monitored


Describe the efferent control of spindle function

- agonist muscle contracts, spindle contracts and output is decreased
- this causes antagonistic muscle to lengthen and those spindles increase their outflow of APs
- this allows you to know exactly what is happening around the joint position


Describe the role and mechanism of action of the Golgi tendon organs

- monitor muscle tension
- nerve endings are intermingled with the tendons at the ends of muscles
- act as stretch receptors and monitor the stretch in tendons
- since tendons are inelastic, the muscles must develop tension to stretch them and so measure muscle tension