Term
| Sensory information includes all input regarding... |
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Definition
| somatosensation and the special senses (vision, hearing, olfaction, taste and vestibular sense.) |
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Term
| The types of somatosensory information that are processed by the CNS include... |
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Definition
| touch, pressure, pain, thermal sense, vibratory sense, proprioception (sensory feedback regarding static joint position, muscle length and force), and kinesthesis (sensation of limb movement). |
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Term
| Classification of Sensory Receptors (Less common) |
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Definition
A. Interoceptors signal changes within the body (e.g., stomach distension)
B. Proprioceptors signal changes in body position (e.g., spindles & tendon organs)
C. Exteroceptors respond to stimuli arising outside the body |
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Term
| Classification of Sensory Receptors (More common terminology) |
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Definition
A. Chemoreceptors:
- for example: the receptors used for smell, taste, and blood pH.
B. Photoreceptors:
- for example: the rods and cones of the retina
C. Thermoreceptors:
- for example: receptors that respond to heat & cold
D. Mechanoreceptors:
- This is the most varied group and includes receptors for touch, muscle length & force, auditory and vestibular receptors.
E. Nociceptors:
- These receptors signal pain in viscera and body wall (muscles, joints, and skin) |
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Term
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Definition
| signal changes within the body (e.g., stomach distension) |
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Definition
| signal changes in body position (e.g., spindles & tendon organs) |
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Term
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Definition
| respond to stimuli arising outside the body |
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Definition
| - for example: the receptors used for smell, taste, and blood pH. |
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Term
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Definition
| - for example: the rods and cones of the retina |
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Term
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Definition
| - for example: receptors that respond to heat & cold |
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Term
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Definition
| - This is the most varied group and includes receptors for touch, muscle length & force, auditory and vestibular receptors. |
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Term
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Definition
| - These receptors signal pain in viscera and body wall (muscles, joints, and skin) |
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Term
| The receptor's function is to... |
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Definition
| translate energy forms (e.g., pressure, temperature, mechanical vibration, light, sound vibration, etc.)into action potentials which reach the CNS so that the signal can be perceived at a higher level (i.e., the cortex). |
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Term
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Definition
| Are transducers. They lie at the "border" between the nervous system and the outside world. |
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Term
| If some receptors are specialized endings of afferent neurons, this means what or what happens? |
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Definition
| The afferent neuron is activated directly when the stimulus energy impinges upon the specialized plasma membrane of the receptor. |
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Term
| Some receptors are cells that are separate from the afferent neuron, and they have a specialized membrane that is activated by the stimulus (e.g., hair cells of the auditory and vestibular system). What happens then? |
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Definition
| Upon stimulation, the receptor cell releases a chemical messenger which crosses the extracellular cleft and binds to the afferent nerve ending, similar to a synapse, causing activation of the sensory neuron. |
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Term
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Definition
| The response of the receptor to stimulation. Which is usually a graded potential. |
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Term
| Do receptor potentials normally require temporal and spatial summation to reach threshold? |
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Definition
| Yes, and convert to all-or-none action potentials in the peripheral axon of the afferent neuron. |
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Term
| What are two basic structural categories of cutaneous receptors? |
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Definition
A. Encapsulated receptors have multiple layers of epithelial tissue surrounding the receptive ending of the sensory neuron. The capsule is thought to serve as a mechanical filter to modify the stimulus.
B. Non-encapsulated receptors include free (or bare) nerve endings. The presence or absence of a connective tissue capsule around the receptor ending partly determines how the receptor responds to a stimulus. |
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Term
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Definition
| have multiple layers of epithelial tissue surrounding the receptive ending of the sensory neuron. The capsule is thought to serve as a mechanical filter to modify the stimulus. |
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Term
| Non-encapsulated receptors |
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Definition
| include free (or bare) nerve endings. The presence or absence of a connective tissue capsule around the receptor ending partly determines how the receptor responds to a stimulus. |
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Term
| Do receptors show adaptation to a stimulus? |
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Definition
All receptors show some degree of adaptation to a stimulus. This means that the frequency of action potentials progressively decreases, even though the stimulus may continue to be applied to the receptor.
A. Slowly adapting receptors signal static conditions (e.g., static position).
B. Rapidly adapting receptors signal changes in stimuli (e.g., a change in position). |
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Term
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Definition
A. Slowly adapting receptors signal static conditions (e.g., static position).
B. Rapidly adapting receptors signal changes in stimuli (e.g., a change in position). |
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Term
| Types of Cutaneous Receptors: |
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Definition
Free nerve endings
Hair receptors
Merkel's receptors
Meissner's corpuscles
Pacinian corpuscles
Ruffini Endings |
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Term
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Definition
A. Non-encapsulated, may be rapidly or slowly adapting.
B. Found subcutaneously and throughout the body.
C. Respond to a variety of stimuli: pain, temperature, mechanical deformation (crude touch).
D. Innervated either by Group III (A-delta) lightly myelinated axons or by Group IV (C) unmyelinated axons. |
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Term
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Definition
A. Non-encapsulated, however rapidly adapting.
B. Nerve ending is wrapped around the base of the hair follicle.
C. Bending the hair is thought to deform the sensory ending, sending action potentials along the sensory axons.
D. Respond well to movement (i.e., brushing across the skin), but not to steady pressure.
E. Innervated by Group III (A-delta) lightly myelinated axons. |
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Term
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Definition
A. Non-encapsulated; slowly adapting; also called Merkel's tactile disks
B. Found in both hairy and glabrous (hairless) skin.
C. Sensory axons branch several times at the terminal to insert into the base of several specialized cells called "Merkel cells" located under the epidermis.
D. Thought to be a mechanoreceptor that is responsive to pressure
E. Innervated by A-beta myelinated axons. |
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Term
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Definition
A. Encapsulated, rapidly adapting
B. Found between epidermis and dermis of glabrous skin.
C. Pressure applied to dermis compresses capsule and nerve endings to activate sensory receptor.
D. High density of Meissner's corpuscles in fingertips; are thought to be responsible for fine tactile discriminative sense, stereognosis (ability to identify objects by touch), and two-point discrimination (the minimum distance by which two stimuli can be separated and still be perceived as two stimuli (~2 mm for fingertips; several cm for the back).
E. Innervated by A-beta myelinated axons. |
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Term
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Definition
A. Encapsulated; rapidly adapting
B. Found subcutaneously over the entire body and in other connective tissue sites.
C. Nerve ending is heavily encapsulated in multiple layers (lamellae) of epithelial tissue with a fluid space between layers.
D. Rapidly applied forces are transmitted to the nerve ending, but static, maintained forces are not (due to elastic properties of lamellae).
E. Extremely sensitive receptors; respond to as little as 1 mm deformation of skin.
F. The most rapidly adapting of cutaneous receptors, Pacinian corpuscles are poor at sensing static pressure, but very good at sensing vibration.
G. Innervated by A-beta myelinated axons. |
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Term
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Definition
A. Encapsulated; slowly adapting.
B. Widespread in dermis, subcutaneous tissue, and other connective tissue sites.
C. Good at sensing static or maintained pressure or stretch applied to skin overlying the receptor.
D. Innervated by A-beta myelinated axons. |
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Term
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Definition
| The cutaneous receptor responds to stimuli only within a defined region of the skin surrounding the receptor. |
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Term
| The more closely spaced are the receptors, the... |
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Definition
| smaller the skin area that each receptor monitors. |
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Term
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Definition
| Localization of the stimulus is facilitated by a processes. It is at the level of the spinal cord in which the most intensely stimulated neuron of the most intensely activated receptor inhibits less intensely stimulated neurons via the action of inhibitory interneurons in the cord. |
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Term
| The smaller the receptive field, the... |
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Definition
| greater is its acuity or discriminative ability. |
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Term
| Fingertips are richly innervated with cutaneous receptors and have much smaller or larger receptive fields than the elbow or the back? |
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Definition
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Term
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Definition
| the sense of position and movement of the limbs. |
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Term
| Limb proprioception is divided into two submodalities: |
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Definition
| sense of stationary position of the limbs (limb position sense) and sense of limb movement (kinesthesia). These sensations are important for maintaining balance and for controlling limb movements. |
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Term
| Four main types of receptors signal the stationary position of the limb and the speed and direction of limb movement: |
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Definition
| joint receptors, muscle spindles, golgi tendon organs and cutaneous mechanoreceptors. |
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Term
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Definition
A. Free nerve endings, Ruffini’s endings, Paciniform corpuscles, and Ligament receptors
B. Rapidly or slowly adapting.
C. Found in joints, joint capsules
D. Sensitive to joint movement, tension, and to extremes of joint position (e.g., full flexion or full extension)
D. Surprisingly joint receptors do not play a major role in sensing position of the limb at rest as can be demonstrated in patients with artificial joints, in which many of the joint receptors have been removed along with the diseased joint. These patients still have a good sense of static position via other receptors such as muscle spindles (located in muscle) and mechanoreceptors located in muscle and skin. |
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Term
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Definition
| A spindle shaped muscle stretch receptor found in parallel with skeletal muscle fibers. Skeletal muscle fibers are sometimes called extrafusal muscle fibers to distinguish them from the intrafusal muscle fibers found within the muscle spindle capsule. |
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Term
Muscle Spindle:
Encapsulated?
Adapting? |
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Definition
| Encapsulated, slowly adapting |
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Term
| Skeletal muscle fibers are sometimes called extrafusal muscle fibers to distinguish them from what? |
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Definition
| the intrafusal muscle fibers found within the muscle spindle capsule. |
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Term
| "nuclear bag" or "nuclear chain" |
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Definition
| Intrafusal muscle fibers, depending on the arrangement of their nuclei in the middle (equatorial) portion of the intrafusal muscle fibers. |
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Term
| Sensory innervation of the muscle spindle consists of... |
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Definition
| group Ia and group II afferents. |
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Term
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Definition
| The Ia afferent wraps itself primarily around the center or equatorial region, forming the annulospiral ending. |
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Term
| The group II afferent, is primarily found on what and forms what? |
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Definition
| A nuclear chain fiber and a flower-spray ending. |
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Term
| The group II endings tend to have what type of discharge? |
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Definition
| A steady, slow rate of discharge (called the static response) that increases a little when the muscle is stretched and decreases when the muscle shortens. |
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Term
| Group Ia ending gives what type of dynamic response? |
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Definition
| It rapidly increases its firing rate with rapid stretch and can cease firing altogether when the muscle is shortened (i.e., during contraction). |
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Term
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Definition
| Direct monosynaptic activation of alpha motor neurons that innervate extrafusal muscle from the same muscle in which the spindle lies. |
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Term
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Definition
| The homonymous muscle forms the monosynaptic reflex loop and is the anatomical substrate for the monosynatpic stretch reflex. |
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Term
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Definition
| Intrafusal muscle fibers also have a motor innervation by way of gamma motor neurons. Gamma motor neurons, innervate in the central region of each of the striated poles of the intrafusal fibers. Activation of a gamma motor neuron causes the polar regions to contract, activating the sensory endings in the central or equatorial region. Gamma motor neurons can set the sensitivity of the spindle (gamma bias) by providing varying degrees of activation of the polar regions, thus making the equatorial region more sensitive to minor stretches of muscle. |
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Term
| alpha-gamma co-activation |
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Definition
| alpha and gamma motor neurons are simultaneously activated by descending motor pathways. To prevent unloading of the spindle and the disruption of feedback to the spinal cord during natural movements involving shortening contractions. |
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Term
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Definition
A. Encapsulated
B. A few tendon organs are found in the tendon proper, but most are found in the aponeurosis of origin or insertion.
C. Tendon organs lie in series with muscle fibers, connecting with 5-25 muscle fibers, each from a different motor unit.
D. The sensory innervation of the tendon organ is the group Ib afferent. Endings of this afferent are intertwined between collagen fascicles of the tendon organ.
E. When the muscle contracts, the inserting muscle fibers pull on the collagen fascicles and squeeze the Ib nerve endings, sending action potentials along the Ib afferent to the spinal cord.
F. The tendon organ is a sensitive muscle force receptor, and its afferent provides the CNS with a measure of local intramuscular force. |
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Term
| Golgi Tendon Organ are mostly found in the... |
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Definition
| aponeurosis of origin or insertion. |
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Term
| Golgi Tendon Organ is a sensitive muscle _____ receptor |
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Definition
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Term
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Definition
| Primary afferents from muscle spindle (annulospiral ending) primarily from nuclear bag, but also from nuclear chain fibers; heavily myelinated |
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Term
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Definition
| Primary afferent from Golgi tendon organ; heavily myelinated |
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Term
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Definition
| Secondary afferent from muscle spindle (flower spray ending); primarily nuclear chain fibers; myelinated |
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Term
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Definition
| Lower threshold cutaneous mechanoreceptors for touch, pressure, 2-point discrimination, vibratory sense; myelinated |
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Term
| A-delta afferent or Group III afferent |
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Definition
| Higher threshold cutaneous mechanoreceptors (nociceptors); lightly myelinated |
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Term
| C fiber or Group IV afferent |
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Definition
| High threshold cutaneous and joint afferent; nociceptors; unmyelinated; very small; nerve endings too |
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Term
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Definition
| area of skin supplied by a single afferent spinal nerve (dorsal root) or by afferents of cranial nerve V (trigeminal). |
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Term
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Definition
| the part of the spinal cord that encompasses a single spinal nerve (dorsal and ventral root). |
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Term
| What segments innervate the most distal parts of the body? |
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Definition
| index and middle finger, C7; great toe, L4,5 |
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Term
| There is no dermatome associated with either the C1 or the coccygeal spinal nerve because |
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Definition
| these nerves have no dorsal roots |
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Term
| Landmark dermatomes to be especially familiar with are: |
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Definition
V1: nose, orbital area and ventral lateral skull
V2: upper lip, maxilla and temporal region
V3: lower lip, mandibula, and ventral ear
C2: occiput
C4: posterior neck and upper shoulder
C6, C7, C8: hand
C6: thumb
C7: index and middle fingers
C8: ring and little fingers
T1: upper thorax and anterior surface of upper extremity
T4: nipple zone
T5: inferior angle of scapula
T10: umbilical zone
L1: inguinal region
L4: lateral thigh, anterior surface of knee, and medial leg, great toe
L5: middle three toes, sole of foot (sometimes great toe)
S2: genitalia and back of thigh
S5: perianal region |
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