Sensory Receptors 2 Flashcards
Name 3 proprioceptors:
Muscle spindles
Golgi tendon organs
Joint receptors
What do Muscle Spindles measure?
Monitor muscle length and rate of change of muscle length so they control reflexes/voluntary movement
What do Golgi tendon organs monitor?
Monitor tension on tendons (tension produced by muscle contraction so essentially measuring muscle tension)
Joint receptors monitor?
mONITOR Joint angle, rate of angular movemtn and joint tension.
What 3 things do proprioceptors transmit sensory info for?
controlling voluntary movement
spinal cord reflexes
percieving limb/body position and movement in space (Kinaesthesia)
What is a muscle spindle?
Speclised intrafusal muscle fibres contained within a capsule
How ae muscle spindles arranged withinm muscle?
In amongst extrafusal fibres, running parallel to them
Do intrafusal muscle fibres contain myofibrils?
Only the ends do not the centre
What type of motor neurons innervate muscle spindles?
Gamma motor neurons
What type of motor neurons innervate extrafusal fibers?
alpha motor neuons
From what part of an intrafusal muscle fibre do sensory neruons emerge?
The central (lacking myofibriles) section
What makes up golgo tendon organs?
Collagen fibre
Sensory neurons
A capsule
What makes up the capsules around muscle spindles and golgi tendon organs?
Connective tissue
What different groups of afferent neurons emerge from muscle spindles?
Groups I & II
What are nuclear bag fibres?
A type of intrafusal fibre
Theyre bag shaped with nuclei gethered together
What are nuclear chain fibres?
A type of intrafusal fibre
Nuclei lined up in a chain
What are annulospiral endings?
Primary endings from Ia afferent nerves that spiral around the centre of intrafusal fibres (around the nuclei)
What are flower-spray endings?
Secondary endings from type II afferent neurons. (at end of central section of a muscle spindle)
Whats the main difference between alpha and gamma motorneurones?
Alpha are larger in diameter.
How are action potentials triggered in muscle spindles?
- When the muscle stretches
- stretch sensitive ion channels open
- Creates a local generator potential
- causes regenerative action potentials
What does the AP frequency depend on?
The length of the muscle Lo.
How do we determine the rate of change of muscle length?
from the change in AP frequency (i.e. the slope of the line)
How does moving the agonist muscle affect spindle dischargE?
Shortening agonist (contracitng) will reduce spindle discharge Stretching agonist increases spindle discharge
How does moving the antagonist muscle affect spindle discharge?
Shortening antagonist increases spindle discharge
Stretching antagonist decreases spindle discharge.
How does the brain know joint position?
From the information from spindles and joint receptors
How are golgi tendon organs arranged relative to extrafusal muscle fibres?
Then are between the tendons and muscle fibres
What does the golgi tendon organ measure?
Tension in muscle by tendon stretch (i.e. contracting muscle)
How are muscle proprioceptors arranged within muscle?
Muscle spindles lie in parallel with extrafusal muscle fibres and Golgi tendon organs in series.
What happens to GTOs during isometric contraction?
Tnesion increases so Ib sensory axons fire
Muscle stays same length so Ia afferents dont fire
why is gamma motorneuron innervation of muscle spindles important?
Without it muscle spindles wouldnt contract to match extrafusal muscle fibres so wouldnt trigger 1a spindle discharges and so the brain would receive no info about muscle length. Possibly preventing use of that muscle.
Why are gamma motorneurones activated? (hint: think sensitivity)
To main spindle sensitivity to changes in the extrafusal muscle fibre length by making the spindles match it.
How do alpha and gamma motorneurons work together?
By alpha-gamma coactivation
