Nervous System 2.0 (for midterm 2) Flashcards
What is the main function of the somatosensory system?
to mediate sensations such as touch, pressure, limb position, vibration, temperature and pain
What senses stimulation? Where are they located?
Receptors in the skin, muscle and tendon receive sensations and send information to the CNS
What are the 3 subsystems of the somatosensory system?
cutaneous mechanoreceptors
proprioception
pain and temperature
What kind of sensory information do cutaneous mechanoreceptors receive?
touch, vibration, pressure on the skin
What kind of sensory information do proprioceptors receive? Where are these?
limb positioning
load on joints
located in muscles, tendons and joints
How is sensory information transported from the body (ex. finger tips) to the brain?
via sensory receptors with dorsal root ganglia and cranial nerve ganglia
What are dorsal root ganglia?
the cell bodies of afferent fibers (sensory receptors for the body)
What are cranial nerve ganglia?
the cell bodies of afferent fibers (sensory receptors for the brain)
Explain how a sensory stimulation would be transferred from the finger tip to the brain?
dorsal root ganglia extend axons into the finger and up the spinal cord
information travels from the finger tip through the dorsal root ganglia cell body and up the spinal cord
synapse at the top of the spinal cord
synapse in the thalamus
cranial nerve ganglia axon extends into the somatosensory cortex of the cerebral cortex
Where does the dorsal root ganglia synapse with the cranial nerve ganglia?
in the thalamus
What part of the brain does the cranial nerve ganglia synapse to transmit the somatosensory information to the brain?
the somatosensory cortex of the cerebral cortex
What is a dermatome?
the region of the body that is innervated by a single dorsal root ganglion and its spinal nerve
Give an example of a dermatome
Cervical nerve 2 innervates the back of the head and neck
What type of membrane receptors are mechanoreceptors?
transmembrane cation channels
called PIEZO channels
Explain the transduction of mechanosensory afferents
Mechanoreceptors have PIEZO channels closed to both inside and outside of afferent nerve
Na+ is high extracellularly and low intracellularly
- mechanoreceptors on the afferent nerve membrane sense a stimulus (ex. pressure on skin)
- stretching of the membrane in response to the pressure stimulus opens the PIEZO channels (ie., changes the permeability of the membrane)
- Na+ fluxes into the afferent causing a depolarization current across the afferent membrane (generator/receptor current)
- if stimulus is strong enough, an AP is generated
How is the firing frequency of APs in mechanosensory afferent nerves related to the stimulus?
the frequency of APs is proportional to the magnitude of membrane depolarization or the strength of the stimulus
ex. weak stimulus = weak receptor potential (doesn’t reach threshold)
strong stimulus = receptor potential reaches threshold and causes strong spike potential
What are the cutaneous mechanoreceptors for touch?
Merkel cells
Meissner cells
Pacinian cells
Ruffini cells
What type of afferent axons are involved with touch cutaneous mechanoreceptors?
Abeta
myelinated, fairly thick
What is the axon diameter of afferents involved with touch cutaneous mechanoreceptors?
6-12 um
second largest
What is the conduction velocity of afferents involved with touch cutaneous mechanoreceptors?
35-75 m/s
second fastest
Are afferents associated with cutaneous mechanoreceptors for touch myelinated?
yes
What are the proprioception receptor types?
muscle spindles and Golgi tendon organ
What are the afferent axon types for proprioception?
Aalpha
Ia
II
Ib (Golgi organ)
Are afferent axons for proprioception myelinated?
yes