Somatosensory I Flashcards
The somatosensory system can be divided into 3 subsystems: one that processes touch, pressure, & vibration; one that processes proprioception; and one that processes pain and temperature information.
True
False
True
Explanation
This statement is true: the somatosensory system can be divided into 3 subsystems: one system will process information from exteroceptors that allow us to sense touch (discriminative) touch, pressure, & vibration; one system that will process information from proprioceptors that allows us to sense limb/body positions and movements; and one that processes information from exteroceptors that allow us to sense pain and temperature (and crude touch) information.
The primary afferents of the somatosensory system are pseudo-unipolar neurons.
True
False
True
Explanation
This statement is true: the primary afferents (sensory neurons) of the somatosensory system are pseudo-unipolar neurons that have their cell bodies in the dorsal or cranial root (trigeminal/semiulnar) ganglia. Their peripheral processes are traveling with the peripheral nerve and their central processes enter the spinal cord as the dorsal root or the brainstem as the cranial sensory root.
Which of the following fiber types conducts action potentials at the highest speed?
Group Ia
Group II
Group III
Group IV
Group la
Explanation
Group Ia fibers have the largest axon diameter and are heavily myelinated and they conduct at the highest speeds. Then in order of decreasing axon diameter and conduction velocity are Group Ib and II (these fibers are myelinated); and then group III and IV (which are unmyelinated).
The majority of the mechanoreceptors contain stress gated ion channels selective for anions.
True
False
False
Explanation
This statement is false: the majority of mechanoreceptors have stress gated ion channels selected for cations creating a depolarizing current (receptor potential (which is nothing more than a graded potential generate by a receptor).
Which of the following statements best reflects the density of receptors, receptive field size, and cortical representations in somatosensory cortex?
As receptor density decreases, receptive field size decreases, and cortical representation decreases.
As receptor density increases, receptive field size increases, and cortical representation increases.
As receptor density decreases, receptive field size decreases, and cortical representation decreases.
As receptor density increases, receptive field size decreases, and cortical representation increases.
As receptor density increases, receptive field size decreases, and cortical representation increases.
Explanation
The density of the receptors determines the size of the receptive field. The greater the density of the receptors the smaller the receptive field. There is an inverse relationship between receptive field size and cortical representation such that the smaller the receptive field the larger the cortical representation.
Which of the following cutaneous mechanoreceptors is rapidly adapting and important for sensing tapping or movement in non-hairy skin?
Meissner’s corpuscle
Pacinian corpuscle
Ruffini corpuscle
Meissner’s corpuscle
Explanation
The Meissner’s corpuscle is a rapidly adapting mechanoreceptor that is allows us to sense tapping or movement in non-hairy skin. The Pacinian corpuscle is a rapidly adapting receptor that allows us to sense deep pressure and vibration. The Ruffini corpuscle is a slowly adapting mechanorecptor that allows us to feel skin stretch.
Which of the following cutaneous mechanoreceptors is located deep in the dermis or subcutaneous tissue? Select all that apply.
Pacinian corpuscle
Meissner’s corpuscle
Merkel cell
Ruffini corpuscle
Hair follicle
Pacinian corpuscle, Ruffini corpuscle, Hair follicle
Explanation
There are 3 deep cutaneous mechanoreceptors: Pacinian corpuscle, Ruffini corpuscle, and the hair follicle; Meissner’s corpuscles and Merkel cells are superficial mechanoreceptors.
Merkel cells allow us to have discriminitative touch.
True
False
True
Explanation
This statement is true: Merkel cells allow us to have discriminative touch, localization of touch, & the ability to determine object characteristics.
Which proprioceptor is important for monitoring muscle length and transmits information about the velocity of limb movements to the CNS?
Golgi tendon organ
Hair follicle
Muscle spindle
Muscle spindle
Explanation
The muscle spindle (specifically the group Ia primary afferent) monitors changes in muscle length that allow the CNS to determine the velocity of limb movements. The Golgi tendon organ is important for conveying information about muscle tension, and the hair follicle allows us to determine movement of stimuli in hairy skin.
Which of the following central pathways relays touch, pressure, vibration and proprioceptive sensations to primary somatosensory cortex? Select all that apply.
Posterior Columns-Medial Lemniscal System
Anterior spinocerebellar tract
Cuneocerebellar tract
Trigeminal System
Trigeminal System & Posterior Columns-Medial Lemniscal System
Explanation
The PCMLS conveys touch, pressure, vibration & proprioceptive information from the body to primary somatosensory cortex and the Trigeminal System conveys these sensations from the face to primary somatosensory cortex. The anterior spinocerebellar tract (and posterior spinocerebellar tract - not shown) and the cuneocerebellar tracts convey proprioceptive information from the body (lower limb and upper limb respectively) to the cerebellum.
The lower limb representation in primary somatosensory cortex is located in the posterior paracentral gyrus.
True
False
True
Explanation
This statement is true: the lower limb is represented in the posterior paracentral gyrus, and the upper limb and face are represented in the postcentral gyrus (upper limb in the upper 1/2 and the face in the lower 1/2).
The primary proprioceptive afferents of the trigeminal system are located in the principal sensory nucleus.
True
False
False
Explanation
This statement is false: the primary proprioceptive afferents are located in the mesencepahlic nucleus, and the second order neurons of the trigeminal system are located in the principle sensory nucleus.
The somatotopic organization of primary somatosensory cortex is fixed and cannot be changed.
True
False
False
Explanation
This statement is false: the somatotopic organization of primary somatosensory cortex can change as a result of (development) experience and injury.
In order to sense the spatial location of two separate stimuli on the surface of the digits, two separate populations of cortical neurons must be activated in primary somatosensory cortex.
True
False
True
Explanation
This statement is true: in order for someone to be aware of two separate stimuli placed on the surface of the digits (or anywhere else for that matter) two separate populations of cortical neurons must be activated.
