Lecture 5: Sensation and Somatosensory Pathways part 1 Flashcards
(22 cards)
What are the 3 functions of the nervous system?
sensation
integration
motor
What is “sensation”?
The conscious or unconscious awareness of external or internal stimuli
What is “perception”?
The action of the mind by which it refers its sensations to an external object as their cause.
Touch, pressure, proprioception, kinesthesia, itch/tickle, temperature, and pain are examples of what kind of sense?
General sense
Special senses include what?
gustation, vision, audition, equilibrium, olfaction
What 4 events must occur in the process of sensation?
stimulation of a receptor
transduction
transmission
translation
Where do most conscious sensations occur?
Cerebral cortex
What is transduction?
Conversion of one form of energy to another
(Graded potential - the amplitude= strength of the stimulation)
What are the 3 types of microscopic structures of sensory receptors?
free nerve endings
encapsulated
separate cells
Special senses have what type of microscopic structure?
separate cells
What type of sensory receptors have generator potential?
Free nerve endings and encapsulated nerve endings
What are the 4 major categories of tactile mechanoreceptors?
Merkel’s disks
Meissner’s corpuscles
Ruffini endings
Pacinian corpuscles
What receptors detect discriminitive touch and pressure (slow adapting)?
Merkel disk (Type 1 cutaneous mechanoreceptor)
What do Meissner corpuscles detect?
Discriminitve touch, pressure, vibration low frequency,
(rapidly adapting and most sensitive to onset of touch)
What does Ruffini corpuscles detect?
Discriminitive touch - detect skin stretch and CONTINUOUS touch
(slowly adapting)
What do Pacinian (lamellated) corpuscles detect?
Pressure, vibration (high f), itch/tickle
(rapidly adapting)
When extrafusal fibres are stimulated to contract by alpha motor neurons, gamma motor neurons simultaneously stimulate intrafusal mm fibres to contract to produce smooth movement of limbs. What is this process called?
Alpha-gamma coactivation
What are the sensory modalities of the posterior column - medial lemniscus?
touch, pressure, vibration and conscious proprioception from limbs, trunk, neck and posterior head.
What is the medial component of the posterior column consisting of axons from trunk and LE?
Fasciculus gracilis
What are the sensory modalities of the Anterolateral (Spinothalamic) Pathway?
Lateral STT: pain (discriminitive components) and temperature
Anterior STT: tickle, itch, crude touch and firm pressure
Where is the primary somatosensory cortex located?
Postcentreal gyrus of each parietal lobe.
What are the sensory modalities of the Spinocerebellar Pathway - Dorsal?
non-conscious proprioception
