Cutaneous perception Flashcards
What are the sensory modalities?
Light, sound, taste, temperature, pressure and smell
What does a mechanoreceptor detect?
Touch, pressure, vibration, proprioception
What do thermoreceptors detect?
Changes in temperature
What do nociceptors detect?
Pain resulting from physical or chemical change
What do free nerve endings detect?
Pain, thermal, tickle, itch, some touch
What do encapsulated nerve endings detect?
Touch, pressure, vibration
Characteristics of encapsulated nerve endings
Large axon diameter
Myelinated A fibers
Characteristics of free nerve endings
Small axon diameter
Unmyelinated C fibers
What are the two touch modalities?
Crude and fine touch
What is crude touch?
No information about location, size, shape, texture
What are the two types of receptors?
Rapidly acting and slowly acting
What are the two rapidly adapting receptors?
Meissner corpuscle
Hair root plexus
Where are Meissner corpuscles found?
Hairless skin, e.g. hands, lips, tongue etc
Where are hair root plexuses found?
Around hair follicles
What are the two types of slowly adapting receptors?
Merkel discs
Ruffini corpuscles
Characteristics of Merkel discs
Detect fine touch
Free nerve endings, found in epidermis
Characteristics of Ruffini corpuscle
Encapsulated nerve endings
Deep in dermis
Sensitive to stretching during movement
Which receptors detect pain?
Nociceptors
Where are nociceptors found?
Everywhere except the brain
Characteristics of nociceptors
Free nerve endings, little adaptation
When are nociceptors activated?
Intense mechanical, thermal or chemical stimuli capable of causing damage
Characteristics of fast pain
Within 0.1 sec, acute and sharp pain, carried by myelinated A-delta which are precisely located, very fast AP
Characteristics of slow pain
More than a second, chronic and burning pain, carried by unmyelinated C fibers (AP is slower), diffusely located, intensity increases over time
Function of proprioceptors
Prevent tissue damage from excessive muscle extension
Information on body position (muscle contraction, tension in tendons, position of joints)
Function of muscle spindle
Detect changes in muscle stretch
Function of Golgi tendon organs
Detect changes in tendon tension and protect from excessive tension
Function of joint kinaesthetic receptors
Monitor stretch in synovial joints and provide information about joint position and movement
Characteristics of thermoreceptors
Free nerve endings, rapidly adapting but sustain firing at low frequencies
Characteristics of cold receptors
Abundant, can have myelinated A-delta or unmyelinated C fibers, activated between 10-40 degrees
Characteristics of warm receptors
Unmyelinated C fibres, activated between 32-48 degrees
Characteristics of dorsal column-medial lemniscal
Discriminative touch, crossover in medulla, cuneate nucleus (upper body), gracile nucleus (lower body)
Characteristics of corticospinal tract
Motor (descending), crossover in spinomedullary junction
Characteristics of spinocerebellar tract
Proprioception, no functional crossover
Characteristics of spinothalamic tract
Pain and temperature, crossover in spinal cord
What impact does decussation have?
The RHS of the bra
Function of spinothalamic tract
Routes pain information from spinal cord to brainstem and thalamus, information then relayed to somatosensory cortex (pain perception)
Function of spinofeticular tract
Emotional response to pain, descending modulation of pain processing
Effect of thalamic lesion
Sensory loss throughout opposite side
Effect of brain stem lesion
Contralateral sensory loss below face and ipsilateral on face
Effect of central cord lesion
Areas of loss, often asymmetrical and dissociated
Effect of unilateral cord lesion/hemisection
Contralateral spinothalamic loss; ipsilateral corticospinal muscle weakness and dorsal column (touch) loss
Effects of tranverse cord lesion
Loss of all sensory and motor modalities below the lesion
