Sensory receptors Flashcards
What are the 3 types of sensory receptors
Mechanoreceptors- pressure, touch
Proprioreceptors- mechanoreceptors in joints and muscles- Signal info about body position
Nociceptors- respond to painful stimuli
What is a receptor potential
Adequate stimulus causes graded membrane potential change
Adequate stimulus=membrane deformation
Occurs in skin mechano/proprioceptors
What does High stimulus intensity mean for APs
Produces most APs
What does the frequency coding of stimulus intensity involve
- Larger stimulus
- Larger receptor potential
- Higher frequency of APs
What happens to mechanoreceptors once there is a maintained stimulus
Adaptation
Mechanoreceptors adapt to maintained stimulus
Only signals when theres a change in stimulus
What sensory receptors can’t adapt
Nociceptors
What is a receptive field
Somatic sensory neuron activated by stimuli in specific area
What is lateral inhibition
Receptors at edge of a stimulus more strongly inhibited than receptors near centre
What are some different proprioceptors
Muscle spindles
Golgi tendon organs
Joint receptors
What is the function of muscle spindles
Monitors Rate of change of muscle length
What is the function of golgi tendon organs
Monitor tension on tendons
What is the function of joint receptors
Monitors Rate of angular movement and Tension on joint
What 3 things do these proprioceptors do
Control voluntary movements
Generate spinal reflex movements
Kinaesthesia- info on body position and function
What are muscle spindles made up of
Intrafusal and extrafusal muscle fibres
What are the two types of intrafusal fibre
Nuclear bag fibres- bag shaped with nuclei
Nuclear chain fibres- nuclei in a chain
What are annulospiral endings
Primary endings from Ia afferent nerves wrapped around intrafusal fibres
What do the ends of intrafusal fibres contain
Sarcomeres
What is the function of gamma a motor neuron
Innervate extrafusal muscle
What is the function of Gamma (y) motoneurones
Innervate
Cause contraction of contractile ends of intrafusal fibres
When a muscle length changes from L0 to L1 what happens to APs
Increase in AP frequency proportional to velocity of stretch
Increase of AP frequency at new steady state
What is the function of stretch receptors?
monitor stretch of tendon
How do muscles develop tension
Contract to stretch the tendons
How does GTO monitor muscle tension
Muscle contraction increases tension
This stretches nerve endings of GTO
Initiates APs in group 1b afferent fibre from GTO
What would happen if a motor neuron fired without y
Extrafusal muscle contracts and shortens
Intrafusal stays same length (becomes slack)
1a sensory firing decreases
What happens when a and y fire together
Muscle and spindle shorten together
No drop off in 1a firing
In reality how do a and y motor neurons work togther
a-y coactivation
spindle 1a report muscle shortening
y motor nerves maintain stretch sensitivity of spindle
