The Sensorimotor System Flashcards
Explain the concept of adequate
stimulus
Adequate stimulus: The type of stimulus that a sensory organ is adapted to. Light energy for the eye.
Describe sensory transduction and
sensory threshold
Sensory transduction: Conversion of electrical energy from a stimulus into a change in membrane potential in a receptor cell.
Sensory threshold: the minimum intensity of a stimulus needed to trigger a detectable sensation
Explain how sensory systems encode
stimulus intensity and location.
Sensory receptors encode the intensity of a stimulus through sensory adaptation, where the number of activated receptors and strength of electrical signals sent to the nervous system increase proportionally to the stimulus intensity
Define adaptation
How our senses adjust to continuous stimuli over time.
Sensory adaptation: progressive decrease in a receptor’s response to sustained stimulation.
Describe each step of the Dorsal column-
medial lemniscus pathway
1) Mechanoreceptors activated by touch
2) Unipolar neurons that are connected to that receptor synapse onto (talk to) the dorsal column of spinal cord
3) These neurons then travel ipsilaterally to the medulla to synapse onto dorsal column nuclei
4) The next set of neurons decussates (crosses over) to contralateral (opposite)
side and travels up the medial lemniscus to
synapse on the thalamus
5) The neurons that come from the thalamus projects to primary somatosensory cortex (S1)
6) Neurons ascend to thalamus
7) The left thalamus receives info about the
right and vice versa
Identify & describe fiber types involved
in touch and pain (ex: C Fiber)
A delta: Large-diameter, myelinated axons (sends pain information fast)
C fibers: Thin, unmyelinated fibers (Sends pain information slowly after injury)
Describe phantom limb pain
A type of chronic neuropathic pain that is
perceived to occur where the limb once was.
Somatosensation
Touch
Gustatory
Taste
Olfaction
Smell
Auditory
Hearing
Visual
Eyesight
Proprioception
Where our bodies are in the world
Patient IW
Needed his eyes to coordinate movement
Sensory receptor organs
Organs specialized to detect a stimulus
Receptor cells
Convert the stimulus into an electrical signal
What type of energy do our senses use to communicate with our brains?
Action Potentials
How does our brain recognize distinct senses?
Separate nerve tracts called labeled lines
What are detectors?
An organ or cell that is able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve.
Ex. Rod, cones, free nerve endings, messiner corpuscle
Receptor potential
The change in membrane potential that occurs when a receptor is activated by a stimulus
Tactile acuity
The ability to accurately detect a stimulus
Slow adapting receptors
A receptor that fires
for the duration of a
constant stimulus
Rapidly adapting receptors
A receptor that fires at the
onset and offset of an
otherwise continuous
stimulus
Modality
Detected by which class of sensory receptor is activated
What is sensory information mediated by?
Dorsal root ganglion cells
Mechanoreceptors
Directly impacted by mechanical stimulus causing ion channels to open
4 Types
Paninian Corpuscle: Vibration and pressure
Ruffini Corpuscle: Stretch
Merkel’s Disc: Touch
Free Nerve Endings: Pain, itch, temperature
Type 1 Fibers
Superficially located
Type 2 Fibers
Deeper in the skin
What type of receptor is the Paninian Corpuscle?
RA, Type 2
What type of receptor is the Ruffini Corpuscle?
SA, Type 2, Wide receptive fields
What type of receptor is Merkel’s disc?
SA, Type 1, Smallest receptive fields
What type of receptor is Meissner’s corpuscles?
RA, Type 1
Ascending tracts
Information from peripheral nerves is
sent to central nervous system
Primary somatosensory cortex (s1)
Located in the postcentral gyrus;
receives touch information from the opposite side of the body.
Nociceptors
Peripheral receptors on free nerve endings
that respond to painful stimuli.
Descending tracts
Motor commands from the brain to muscles and glands
Dorsal horn
Neurons process afferent sensory information (towards the brain)
Ventral horn
Neurons process efferent sensory information (away from the brain)
