Sensory Systems Flashcards
Describe somatosensory.
Bodily sensation of touch, pain, temperature, vibration, and proprioception.
Received from sensory receptors in skin, joints, ligaments, muscle and fascia. It detects changes in the environment or within the body.
What are the 5 different types of cutaneous mechanoreceptors?
- Free nerve endings
- Merkel cells
- Meissner corpuscles
- Ruffini endings
- Pacinian corpuscles
What do free nerve endings convey? What type of receptor fields do they have?
Temperature, pain, crude touch.
Have small or large receptor fields.
What do merkel cells convey? What type of receptor fields?
Light touch (shape and texture)
Small receptor fields
What do meissner corpuscles convey? What type of receptor fields?
Light touch (motion detection and grip control by responding to very low frequency vibrations)
Small receptor fields
What do ruffini endings convey? What type of receptor fields?
- Stretching of skin = helps provide secondary info, like proprioception.
- Vibration and pressure
Large receptor fields
What do pacinian corpuscles convey? What type of receptor fields?
Vibration and pressure = big scale vibration/pressure movements; gross movements
Large receptor fields
What is proprioception? What 3 types of receptors detect it?
The sense of joint/limb position in space.
- Muscle spindles
- Golgi tendon organs
- Joint receptors
Describe a muscle spindle and what 2 responses they can trigger.
A muscle spindle is composed of intrafusal fibers. They detect the rate and degree of a muscle stretch.
Responses:
- Muscle contraction
- Antagonist inhibition (crucial for the myotactic reflex)
Describe Golgi tendon organs. What 2 responses do they trigger?
Located near the muscle-tendon junction.
Monitors tension within tendons for proper grading of muscle contractions and force needed.
Responses:
- Muscle relaxation (“autogenic inhibition”)
- Inhibit muscle spindles
**Exception: golgi tendon organs can trigger contraction right before a muscle is passively stretched.
Describe joint receptors. What other important receptors are included with the joint receptors?
Monitors stretch in synovial joints. It sends info to cerebellum and spinal reflex arcs.
Other receptors:
- Pacinian = AROM and compression
- Ruffini = indicate end-range and PROM
- Free nerve endings = pain from joint inflammation; non-noxious stress (pressure, temperature, vibration)
Describe A alpha (type 1) axon.
Myelinated with biggest fiber diameter
Receptors = muscle spindles and golgi tendon organ
Sensory modalities = proprioception
Describe A beta (type 2) axon.
Myelinated
Receptors = muscle spindles, meissner corpuscle, merkel receptor, pacinian corpuscle, ruffini ending, hair receptor.
Sensory modalities = proprioception, superficial touch, deep touch/vibration, touch/vibration
Describe A delta (toye 3) axon.
Myelinated
Receptors = free nerve ending
Sensory modalities = Pain, cool temperature, and itch
Describe C (type 4) axon.
Not myelinated with smallest diameter and slowest conduction
Receptors = free nerve endings
Sensory modalities = pain, warm temperature, and itch
Where do the dorsal and ventral rami carry information from?
Dorsal rami = back of body
Ventral rami = ventral trunk and limbs
When does the spinal nerve form? What kind of information is carried in the dorsal and ventral spinal nerves?
Spinal nerve forms after the rami.
They bifurcate into different fibers:
- all sensory input goes to dorsal root
- all motor output comes from the ventral root.
What is within the dorsal root ganglions?
Location where the cell bodies lie.
*everything proximal to the ganglion is considered part of the CNS.
What are dermatomes?
Area of skin with sensory innervation by a single dorsal spinal root.
What are cutaneous peripheral nerves?
They supply an area of the skin that is related to a peripheral nerve.
*can contain fibers from several spinal nerve roots.
What is the general pathway for the somatosensory system?
Cutaneous/muscle receptor –> PNS –> dorsal horn –> white matter tracts –> thalamus –> postcentral gyrus
What column does light touch, proprioception, and vibration travel?
Dorsal column
What column does pain, temperature, pressure, and crude touch travel?
Anterolateral column
Describe the function of the thalamus.
A crucial relay structure for all afferent pathways traveling to the cortex.
What are the 3 relay nuclei?
- Medial nuclear group
- Lateral nuclear group
- Anterior nuclear group
What is the internal medullary lamina?
Contains intralaminar nuclei that project to multiple cortical locations.
*receives input from RAS
What is the responsibility of the thalamic reticular nucleus?
It is in charge of thalamic integration. It does NOT project to cortex.
Where does the ventral posterior lateral nucleus (VPL) relay info to?
Sends somatosensory from the spinal cord to the primary sensory cortex.
Where does the ventral posteromedial nucleus (VPM) relay info to?
Sends somatosensory from cranial nerves to the primary sensory cortex.
Where does the ventral lateral nucleus (VL) relay info to?
Sends information from the cerebellum and basal ganglia to the primary motor cortex and association motor cortices.
Where does the ventral anterior nucleus (VA) relay information from and to?
Sends information from the cerebellum and basal ganglion to the primary motor cortex, association motor cortices, and other frontal lobe structures.
Where does the lateral geniculate nucleus (LGN) relay information?
Sends vision to primary visual cortex.
Where does the medial geniculate nucleus (MGN) relay information?
Sends auditory to primary auditory cortex.
Where does the mediodorsal nucleus (MD)? relay info from?
Sends information from the limbic and basal ganglia to the frontal cortex.
Where does the anterior nucleus relay info from?
Sends information from the mamillary body and hippocampus to the cingulate gyrus.
