6.3 Muscles and Joint Receptors Flashcards
What proportion of fibres in a muscle nerve are sensory
2/3
What are the 3 main types of sensory ending in muscles
muscle spindles, golgi tendon organs, fine afferents
Describe muscle spindle sensory endings
They are large complex mechanoreceptors that are modified muscle fibres. Muscle spindles have a large diameter and hence fast conduction. There are 2 types of muscle spindle fibres. Primary (1a) fibres are very dynamically sensitive and respond to stretch and acceleration in the changing of length. Secondary fibres (II) respond to the static length of muscle, they are slower in response. The sensitivity of both types of fibre can be adjusted by the gamma motor system.
Describe golgi tendon organ sensory endings
They are large mechanoreceptors that are inserted in connective tissue fascicles in the tendon (where the muscle meets the tendon). They have large diameter sensory fibres and are very sensitive to active force development. They detect changes in force/tension.
Describe fine afferent sensory endings
They are either lightly myelinated (group 3) or unmyelinated (group 4). The are very small so are hard to see with a microscope and hard to take electrical recordings of. They can be metaboreceptors (such as ergoreceptors) that monitor the metabolic state of muscles with roles in cardiovascular and respiratory reflexes. They can also be mechanoreceptors and nociceptors.
Where are joint receptors found
Joint receptors are found in connective tissue in joint capsules, ligaments and fat pads
Describe the types of joint receptors
Joint receptors play a crucial role in maintaining joint stability and facilitating reflexive adjustments during movement. They respond to forces in the connective tissue. They are innervated by Group II, III, and IV afferent fibers.
There are 4 types. Type 1 have a ruffini like structure and are slowly adapting. Type 2 have a pacinian corpuscle like structure and are rapidly adapting. Type 3 have a golgi like structure and are slowly adapting. Type 4 are free nerve endings.
What type of transduction is muscle and joint receptors
Mechanotransduction
Describe mechanotransduction
Mechanotransduction is a cells conversion of a mechanical stimulus (the muscles/joints moving) into an electrical signal. All mechanoreceptors have the same transduction mechanism. This is where a transduction channel in the membrane is anchored to the cytoskeleton in side the cell and anchored to a protein extracellularly. So when things move, as the receptor is anchored, the channel is pulled open.
Can channel families in mammalian cells be used for both mechanosensory and thermosensory purposes
Yes
