FUNCTIONAL ANATOMY - Peripheral Sensory Receptors Flashcards
What are the five main functional classfications of sensory receptors?
Mechanoreceptors
Chemoreceptors
Thermoreceptors
Photoreceptors
Nociceptors
What is the receptive field of sensory (afferent) neurones?
Receptive field is a defined area of the body where sensory stimuli will activate that specific neurone
What is lateral inhibition?
Lateral inhibition is the process in which sensory (afferent) neurones inhibit the activity of adjacent neurones to sharpen the localisation and pattern recognition of sensory information
What are dermatomes?
Defined regions of the skin innervated by sensory (afferent) neurones from a single dorsal nerve root
What are the five structural classifications of skin sensory receptors?
Free-nerve ending
Pacinian corpuscle
Ruffini corpuscle
Merkel cells
Meissners corpuscle
Which two sensory stimuli are detected by free-nerve endings?
Pain
Temperature
Why is it essential to have ‘hot’ and ‘cold’ free nerve endings to differentiate between temperatures?
It is essential to have ‘hot’ and ‘cold’ free nerve endings to differentiate between hot and cold temperatures as the action potential frequency is the same at 15°C and 40°C and thus without two distinct types of free nerve endings, it would be impossible to differentiate between hot and cold temperatures
Which sensory stimulus is detected by pacinian corpuscles?
Local pressure
Which sensory stimulus is detected by ruffini corpuscles?
Skin stretching
Which sensory stimulus is detected by merkel cells?
Skin deformation
Which modality is detected by meissners corpuscles?
Sideways shearing of skin
What is sensory adaptation?
Adaptation is a decrease in neural response due to a continued application of a stimulus to sensory receptors
Which sensory modality does not exhibit adaptation?
Pain does not exhibit adaptation
What are centrally-projecting tracts?
Sensory (afferent) neuronal pathways transmitting sensory information from the periphery to the central nervous system
What are the two main centrally-projecting tracts for sensory information from the skin?
Medial lemniscal system
Extralemniscal system
What sensory information is transported by the medial lemniscal system from the skin to the central nervous system?
Precise sensory information such as touch and proprioception
What sensory information is transported by the extralemniscal system from the skin to the central nervous system?
Sensory information such as pain and temperature
Describe how the the medial lemniscal tranmits sensory information from the skin to the somatosensory cortex
The medial lemniscal system transmits sensory information through the ipsilateral dorsal funiculus of the spinal cord to the brain stem followed by relaying the sensory information through the thalamus followed by the somatosensory cortex
Describe how the the extralemniscal tranmits sensory information from the skin to the somatosensory cortex
The extralemniscal system transmits sensory information through the contralateral ventro-lateral funiculi of the spinal cord to the brain stem, followed by relaying the sensory information through the thalamus followed by the somatosensory cortex
What are the two sensory receptors found in muscle?
Muscle spindles
Golgi tendon organs
What are the two components of muscle spindles?
Extrafusal fibres
Intrafusal fibres
What type of LMN (efferent) fibre innervates extrafusal fibres?
Alpha motor fibres
What type of LMN (efferent) fibre innervates intrafusal fibres?
Gamma motor fibres
What are the two classifications of intrafusal fibres?
Nuclear bag intrafusal fibres
Nuclear chain intrafusal fibres
What are the two classifications of sensory neurones which coil around intrafusal fibres?
Type Ia fibres
Type II fibres
What information is transmitted by type Ia sensory fibres?
Information on how far and fast the muscle is stretched
What information is transmitted by type II sensory fibres?
Information on how far the muscle is stretched
Why is alpha/gamma co-activation essential for proprioception?
Coordinated activation of alpha and gamma motor (efferent) neurones stimulates the coordinated contraction of both extrafusal fibres and intrafusal fibres. Contraction of extrafusal fibres is responsible for generating force and movement, however this can slacken the intrafusal fibres, making coordinated contraction of both fibres essential to maintain the position of the sensory neurone wrapped around the intrafusal fibres, to maintain the sensitivity of changes in muscle length even during active contraction - allowing the muscle spindle to provide precise proprioceptive information to the central nervous system
What is the key function of the golgi tendon organs?
Prevent excessive muscle tension
