Costanzo Neurophysiology - Somatosensory System Flashcards
What does the somatosensory system include?
Sensations of touch, movement, temperature and pain
What are the pathways in the somatosensory system?
Dorsal column system
Anterolateral system
What signals does the dorsal column system process?
Sensations of fine touch, pressure, two point discrimination, vibration, and proprioception
What fibers make up the dorsal column system?
group II fibers
What is the course of the dorsal column system?
Primary afferent neurons have cell bodies in the dorsal root.
Axons ascend ipsilaterally to the nucleus gracilis and nucleus cuneatus of the medulla.
Second order neurons then cross the midline and ascend to the contralateral thalamus and synapse on third order neurons.
Third order neurons ascend to somatosensory cortex, and synapse on fourth order neurons?
This card is actually not that much of a fuck. This is why neuro is hard.
What does the anterolateral system processs?
Sensations of temperature, pain, and light touch
What fibers make up the anterolateral system? Where do they terminate?
Made up of group III and IV fibers
Enters spinal cord and terminates in the dorsal horn
What is the course of the anterolateral system?
Second order neurons cross the midline to the anterolateral quadrant of the spinal cord and ascend to contralateral thalamus.
Synapse on third order neurons at contralateral thalamus.
Third order neurons ascend to somatosensory cortex and synapse on fourth order neurons.
Describe the structure of a Pacinian corpuscle.
Onion-like structures in the subcutaneous skin, surrounding unmyelinated nerve endings.
What sensations do Pacinian corpuscles detect?
Vibration, tapping
What is the adaptation rate of Pacinian corpuscles?
rapid
Describe the structure of a Meissner’s corpuscle?
Present in non-hairy skin
Pretty lame, Costanzo.
What sensations do Meissner’s corpuscles detect?
velocity (?). Also, fuck you Costanzo.
What is the adaptation rate of Meissner’s corpuscles?
Rapid
Describe the structure of a Ruffini’s corpuscle.
Encapsulated
What sensations do Ruffini’s corpuscles detect?
Pressure
What is the adaptation rate of Ruffini’s corpuscles?
Slowly adapting
Describe the structure of a Merkel’s disc.
Transducer is on epithelial cells
What sensations do Merkel’s discs detect?
location
What is the adaptation rate of Merkel’s discs?
slowly adapting
What does the thalamus do?
Arrange information from different parts of the body somatotopically
What happens with destruction of the thalamic nuclei?
Loss of sensation on the contralateral side of the body
What is another word for the somatosensory cortex?
Sensory homunculus
What are the major areas of the somatosensory areas of the cerebral cortex?
SI and SII
What is the arrangement of SI?
Somatotopic representation similar to that in the thalamus
What is another name for the ‘map’ of the body in the somatosensory cortex?
Sensory homunculus
What are the largest areas of the somatosensory cortex?
Areas that represent face, hands and fingers - precise localization is most important.
I know, you’re wondering about the genitals. Fairly small area actually. Now you have a scientific justification for that “wrong hole” excuse! Yay science!
What is the neurological term for pain, and what does in entail in a general sense?
Term = nociception
Associated with detection and perception of noxious stimuli
What are the receptors for pain?
Free nerve endings in skin, muscle and viscera
What is an important neurotransmitter for pain?
Substance P
What class of drugs inhibit the release of substance P?
Opiods
How is fast pain carried?
Group III fibers
Rapid onset and offset, localized
How is slow pain carried?
Carried by C fibers
Characterized by achy, burning or throbbing that is poorly localized
