Exam #4 Flashcards
(92 cards)
What percent of your body weight does skin account for?
16%
Discrimination touch
- Perception of pressure, vibration, and texture
- Mediated by 4 different categories of mechanoreceptors in the skin
Pain and temperature
Free nerve endings
Proprioception
Registration of tension and stress in muscles and joints
Rapidly adapting (RA)
Respond to changes in stimulation, but do not continue to respond to constant stimulation
Slowly adapting (SA)
Respond to constant stimulation
Punctate
Small receptive fields with distinct boundaries
Diffuse
Large receptive fields with non-distinct boundaries
4 receptor types enervated by nerve fibers
- Merkel disks
- Meissner corpuscles
- Ruffini ending
- Pacinian corpuscles
Merkel disks
Constant source of stimulation over a small area (shallow)
ex: carrying a pebble
Meissner corpuscles
Respond best to active touch, involved in detailed object exploration (shallow)
Ruffini ending
Constant stimulation over a larger area, also detects skin stretch (deep)
Pacinian corpuscles
Extremely sensitive over a large receptive field (deepest)
ex: blow gently on the palm of your hand
How do receptors work? (2 steps)
- Mechanical stimulus (ex: pressure) deforms receptors’ membrane
- This starts a cascade of events that ultimately results in an AP
3 primary types of proprioceptors
- Muscle spindles
- Golgi tendon organs
- Joint receptors
Muscle spindles
Mechanoreceptors that detect changes in muscle fiber length (stretch) and velocity (speed of stretch), maintains intended limb movement position, direction, and velocity
Golgi-tendon organs
In skeletal muscle near insertion of tendon, detects changes in muscle tension (ex: force), not good at detecting muscle length changes
Joint receptors
Detect change in force and rotation applied to joint, joint movement angle
Peripheral sensory apparatus (in vestibular system)
- Semicircular canals and otolithic organ
- Detects and relays info about head orientation and head angular and linear acceleration to brain
- Orients head with respect to gravity
Central processing system
Processes info in conjunction with other sensory inputs for position and movement of head in space
Motor output system
- Generates compensatory eye movements and compensatory body movements during head and postural adjustments
- Sense of orientation
- Detection of linear and angular acceleration
Semicircular canals
Detects rotational movements by using hair cells to sense fluid displacements
Otolithic organ
Detects linear acceleration and head orientation, otoconia crystals (little rocks) stimulate hair cells in canals
Gate control theory of pain
Pain is actively suppressed in emergency situations by messages sent from brain to Dorsal Horn, pain continues when emergency is over