sensory receptors Flashcards
Describe the structure of cutaneous receptors.
In cutaneous sensory receptors, the nerve endings are protected by a capsule.
What must the stimulus do to trigger an AP?
Must cause a membrane deformation which activates stretch sensitive ion channels.
Define sensation.
When sensory information reaches consciousness.
Define perception.
When there is an understanding of the sensation. This is a high level function.
Where are stretch sensitive ion channels located?
The distal tip of the afferent axon or in specialised sensory cells that then release neurotransmitters to create a generator potential in the axon’s dendrites.
How does sensory transduction occur in the skin?
Transduction processes in all sensory endings involves opening or closing ion channels.
What is frequency coding?
The bigger the stimulus, the greater the receptor potential and the higher the frequency of AP’s. High frequency equals high stimulus intensity.
What does the muscle spindle do?
The muscle spindle monitors muscle length and the rate at which it changes. Important for reflexes and voluntary movements.
What is skeletal muscle made of?
Extrafusal and intrafusal fibres.
What are extrafusal and intrafusal fibres?
Extrafusal fibres are regular muscle fibres. Intrafusal fibres together with their specialised motor and sensory innervation form muscle spindles.
What are intrafusal fibres controlled by?
A-gamma motoneurones. 2 types: nuclear bag fibres and nuclear chain fibres.
What are the mechanisms of efferent control of spindle function?
When an agonist muscle contracts, the spindle contracts and spindle discharge is decreased. However, the antagonistic muscle lengthens and those muscle spindles increase discharge (outflow of AP’s).
What do golgi tendon organs do?
They monitor muscle tension.
Where are the nerve endings of golgi tendon organs?
They are intermingled with the tendons at the ends of muscles. They act as stretch receptors and monitor stretch in tendons. Tendons are inelastic. Muscles develop tension to stretch them and so golgi tendon organs monitor muscle tension.
What are golgi tendon organs stimulated by?
Increased tension and they cause relaxation of the muscle.
