Peripheral Somatosensory System Flashcards
Loss of sensory function can result from ____ and ____ nervous system lesions
central; peripheral
In the 3-neuron pathway what does the first order neuron do?
Brings information from sensory receptors into the spinal cord
In the 3-neuron pathway what does the second-order neuron do?
Conveys information between the spinal cord or brainstem to the thalamus
In a 3-neuron pathway what does the third-order neuron do?
Conveys information from the thalamus to the cerebral cortex
True or False
The cerebellum uses sensory input to modify motor input but it does not percieve it
True
What are the parts of the brain that can consciously percieve somatosensory information?
Thalamus and Cerebral Cortex
What does the peripheral somatosensory information do?
Conveys information from the skin and musculoskeletal system to the spinal cord
What does the peripheral nervous system convert mechanical, chemical, or thermal stimulation into?
Receptor potentials
When is an axon potential produced in a peripheral axon?
When the receptor potential exceeds the threshold of the trigger zone
List the pathway that the axon potential travels along in the Peripheral Somatosensory System.
- Axon potential travels along distal peripheral axon
- pas the T-junction that leads to the cellbody in the dorsal root ganglion
- Goes down proximal peripheral axon into spinal cord
When does the axon potential reach the central nervous system?
When it reaches the spinal cord
Which of the 3-neuron order’s is this?
Pseduounipolar neurons that have distal axons, cell bodies in the dorsal root ganglia and proximal axons
First-order somatosensory neurons
What do the axons of the ventral ramus innervate?
Anterior and lateral trunk and limbs
What do the axons of the dorsal ramus innervate?
Skin and deep muscles of the back
What are sensory receptors?
Specialized end organs that communicate with peripheral nerves or are free nerve endings
What is the following receptor called?
Have ion channels that are responsive to mechanical, thermal, chemical, or electromagnetic energy from environmental stimuli which converts into action potential transmitting the information to the CNS
Sensory Receptor
What are sensory receptors classifed as?
- Chemoreceptors
- Mechanoreceptors
- Thermoreceptors
What is the name of the following sensory receptor?
Consist of free nerve endings or specialized end-organs and respond to mechanical deformation of the receptor by touch, pressure, stretch of vibration
Mechanoreceptor
What is the name of the following sensory receptor?
Free nerve endings and respond to exogenous chemicals or substances released by cells, including damaged cells following injury or infection
Chemoreceptors
What is the name of the following sensory receptor?
Free nerve endings and respond to heating or cooling
Thermoreceptors
Is the following a tonic or phasic sensory receptor?
Respond the entire time a stimulus is present providing constant input to the CNS
Tonic Receptor
Is the following a tonic or phasic sensory receptor?
Adapt to a constant stimulus and stop responding while the stimulus is present
Phasic Receptor
What is the role of a phasic receptor?
Alert the body about a change in a stimulus
Which cutaneous sensory receptor is the following?
- axons myelinated by A(beta) fibers; respond to hair movement; phasic receptors; small receptive field diameter
- axons are lightly myelinated A(gamma): respond to hair movement; phasic receptors; small receptive field diameter
Hair Follicle Nerve Ending
Which cutaneous sensory receptor is the following?
- Axons are myelinated A(beta) fibers: respond to dynamic movement across skin, slippage during grip; phasic receptors; small receptive field diameter
Meissner’s Corpuscle
Which cutaneous sensory receptor is the following?
- Axons are myelinated A(beta) fibers: respond to light pressure, curvature, edges; tonic receptors; small receptive field diameter
Merkel Cell
Which cutaneous sensory receptor is the following?
- Reponds to nociceptive mechanical stimuli and cold stimuli; tonic receptors; medium receptive field diameter
Lightly Myelinated A(gamma)
Which cutaneous sensory receptor is the following?
- Responds to nocieptive mechanical stimuli; pleasant mechanical stimuli; ticklish mechanical stimuli; pruritic stimuli; thermal stimuli; chemical stimuli; tonic receptors; medium field diameter
Unmyelinated C fibers
Which cutaneous sensory receptor is the following?
- Axons are myelinated A(beta) fibers: respond to vibration; phasic receptors;large receptive field diameter
Pacinian Corpuscle
Which cutaneous sensory receptor is the following?
- Axons are myelinated A(beta) fibers: respond to stretch of skin; tonic receptors; large receptive field diameter
Ruffini Corpuscle
Why are larger diameter axons able to transmit information faster than smaller diameter axons?
Due to the low resistance to current flow in large-diameter axons and because they are myelinated allowing saltatory conduction of action potential to take place
Large-diameter peripheral somatosensory axons only transmit action potential triggered by what?
Mechanical Stimuli
Medium & small-diameter peripheral somatosensory axons are polymodal and transmit signals which sensory modalities
- mechanical
- thermal
- chemical
When does the activity of polymodal neurons increase?
Following tissue injury
20% of cutaneous and 50% of visceral nociceptors are ___
silent nociceptors
What is a receptive field?
Area of skin innervated by a single peripheral somatosensory neuron