4.2 Flashcards
The ____, ____ and the ____ have the largest nuclei of cells in the post central gyrus
hand, foot, and face
an area of skin innervated by cutaneous sensory nerve fibers from one spinal nerve
Dermatomes
There is some ___ in the skin between fibers from
adjacent spinal nerves so it is difficult to detect a loss of sensation when only one spinal nerve is affected
overlap
- distribute nerve fibers from the spinal nerves into different peripheral nerves
Plexuses
area of skin innervated by cutaneous sensory
nerve fibers from a single peripheral nerve
Peripheral nerve fields
- Because of the distribution of _____,
areas of cutaneous innervation can be mapped out by dermatomes and by peripheral nerve fields
nerve fibers in plexuses -
dermatomes, dermatome -
- Injury to a single dorsal root or spinal nerve will result in a modest sensory loss because of overlap of ____ (usually the patient can report a change in sensation, but not total loss of sensation); this area would correspond to a ______
Injury to a plexus or a peripheral nerve (which is distal to a plexus) will result in loss of sensibility in an area corresponding to a _____
nerve field -
- Sensations carried by the Anterolateral pathway (a.k.a. lateral spinothalamic tract)
pain and temperature
Sensations carried in the Dorsal column pathway
discriminative touch and joint position sense (proprioception)
Lamina ____, ____, and ___ are primary for synapsing of pain and temperature neurons
1, 2, 5
Sensation from the anterior half of the head is carried by cranial nerve _____
V, the trigeminal nerve
Neurons in the dorsal horn are arranged in sheets that run parallel to the long axis of the spinal cord
Laminae of the dorsal horn
The trigeminal pain and temperature pathway takes a different course through the ____ from touch and proprioception, therefore these senses must be tested separately
brain stem
Sensation from the face also travels through ____ pathways separate from the sensation ascending from the rest of the body
brain stem
Hemi-section of the cord causes- ipsilateral (same side) spastic paralysis and loss of position sense
- contralateral (opposite side) loss of pain and thermal sense
Brown-Sequard Syndrome
- Branches of the trigeminal nerve supply three dermatomes but unlike the dermatomes of the neck and trunk, the dermatomes of the face do not overlap
The three Dermatomes and branches are:
a) V1: ophthalmic nerve
b) V2: maxillary nerve
c) V3: mandibular nerve -
a pseudounipolar neuron that conveys action potentials from a receptor into the CNS (spinal cord or brain stem)
First-order neuron
a multipolar neuron that decussates and ascends within the CNS to synapse in the thalamus
Second-order neuron
a multipolar neuron that ascends from the thalamus to the parietal lobe of the cerebral cortex
Third order neuron
Anterolateral pathway (a.k.a. lateral spinothalamic tract) pathway
first order neuron
(1) Cell body: located in a dorsal root ganglion
(2) Peripheral process: travels from a pain or
temperature receptor through a peripheral nerve
3-enters the DORSAL HORN and synapses with a -second order neuron
-second order neuron
-Decussates at the same level of the spinal
cord where the cell body is located
-) Axons ascend the spinal cord in the anterior
part of the lateral white columns
(anterolateral pathway)
third order neuron -) Cell body: located in one of the nuclei of the thalamus - Terminates on cortical neurons in the postcentral gyrus
Dorsal column pathway
First order neuron
-Cell body: located in a dorsal root ganglion
-Peripheral process: travels through a peripheral
nerve from receptors in the skin, muscles, tendons,
and joints
-Central processes pass through a DORSAL ROOT into the spinal cord, enter the ipsilateral posterior white column and ascend to nuclei in the dorsal part of the medulla (nucleus gracilis or nucleus cuneatus) where they synapse on second order neurons - Dorsal column pathway
second order neuron
- Cell body: located in either the nucleus gracilis or nucleus cuneatus in the posterior medulla
- Axon: decussates in the medulla and ascends to the thalamus
Third order third order neuron -) Cell body: located in one of the nuclei of the thalamus - Terminates on cortical neurons in the postcentral gyrus
