Block 2 Neuroscience

Front 1

What is the basic pathway for sensory stimuli to be perceived?

Back 1

stimulus -> sensory receptors -> spinal cord -> medulla/brainstem -> thalamus -> cortex

Front 2

What is the direction of sensory pathways?

Back 2

go up (periphery to cortex)

Front 3

What is the direction of motor pathways?

Back 3

go down (cortex to muscles)

Front 4

Receptive field

Back 4

the area in the periphery where application of an adequate stimulus causes response

Front 5

three general categories of sensory receptors

Back 5

exteroreceptive, proprioceptive, interoceptive

Front 6

exteroreceptive receptors

Back 6

code information from the external world, mainly via skin. mechanoreceptors (touch), thermoreceptors (warming and cooling), nociceptors (sharp and burning pain).

Front 7

propioceptive receptors

Back 7

code information about muscle length, muscle tension, joint angles. Muscle afferent receptors = golgi tendon organs (tension) and muscle spindles (length).

Front 8

interoceptive receptors

Back 8

code information about changes inside the body; visceral afferent receptors; localize sensation and pain poorly.

Front 9

stimulus transduction

Back 9

at peripheral terminal stimulus activates receptors and ion channels -> generates receptor potential (depolarization) -> if receptor potential is strong enough, generates action potential -> signal conveyed to spinal cord

Front 10

rate code

Back 10

frequency of action potential firing

Front 11

spatial summation code

Back 11

number of neuron firing

Front 12

what two things does the conduction velocity depend on?

Back 12

axon diameter
thickness of myelin

Front 13

A-alpha and A-beta fibers

Back 13

large myelinated fibers that conduct APs very fast

Front 14

A-delta fibers

Back 14

thin myelinated that conduct APs moderately fast

Front 15

C fibers

Back 15

unmyelinated fibers that conduct APs slowly

Front 16

slowly adapting response

Back 16

respond best to a sustained, unchanging stimulus; sense pressure and shape of objects.

Front 17

rapidly adapting response

Back 17

respond only when stimulus changes (on and offset); sense impact and motion of objects on skin

Front 18

spatial resolution for stimulus depends on ______ and ______.

Back 18

receptive field size
innervation density

Front 19

T/F superficial receptors have a large receptive field size.

Back 19

False; superficial receptors have a small receptive field size; deep receptors have a large receptive field size.

Front 20

innervation density

Back 20

density is high in very sensitive areas; low in insensitive areas. 2-point discrimination best for fingers, mouth; worst for back and calves

Front 21

mechanoreceptors

Back 21

mediate tactile/touch sensation; very sensitive to force; don't respond to painful stimuli; silent w/o stimulation (don't fire APs spontaneously); myelinated axons; fast conduction velocities; signal reaches spinal cord quickly.

Front 22

what are the two types of superficial mechanoreceptors and where are they located?

Back 22

Merkel discs and Meissner's corpuscles; found in border b/t epidermis and dermis

Front 23

what are the two types of deep mechanoreceptors and where are they located?

Back 23

Ruffini endings and Pacinian corpuscles; found in dermis

Front 24

Merkel disks

Back 24

Fine touch, 2-point discrimination; sharpest resolution of surface texture; bumpy vs. smooth. Receptive field: multiple small spots. Several disks innervated by single axon. SLOWLY adapting response (encodes force).

Front 25

Meissner's corpuscles

Back 25

Fine touch, 2-point discrimination; sense abrupt changes in edges, bumps, corners; help adjust grip and release when lifting objects; receptive field - single spot; RAPIDLY adapting response encodes on/offset of skin indentation; corpuscle encloses a stack of flattened epithelial cells with sensory terminal entwined b/t layers; axon myelinated.

Front 26

Ruffini Endings

Back 26

sense stretch of skin; help determine shape of grasped objects; receptive field - large and diffuse; ending encapsulated; myelinated axon surrounds collagen fibrils; SLOWLY adapting response responds to stretching of skin

Front 27

Pacinian Corpuscles

Back 27

respond to high frequency vibration; MOST SENSITIVE, even distribution through skin; receptive field - large and diffuse; fluid filled capsule wrapped around bare nerve endings; filters out sustained stimuli; RAPIDLY adapting response

Front 28

Hair Follicle

Back 28

receptive field: around base of hair follicle
bare axon wraps around base of hair follicle; axon myelinated
rapidly adapting response

Front 29

thermoreceptors

Back 29

encode skin temperature and discharge continuously at normal skin temperature

Front 30

cooling receptors

Back 30

increase firing rate when skin is cooled. stop firing when skin is warmed. free nerve endings with myelinated axons. small receptive fields; infrequent distribution.

Front 31

warming receptors

Back 31

increase firing rate when skin is warmed above 32 degrees. stop firing when cooled. free nerve endings with UNmyelinated axons. very small receptive fields.

Front 32

cooling and warming receptors respond best to _______ in skin temperatures

Back 32

changes

Front 33

nociceptors

Back 33

pain receptors; respond to stimuli that damage or threaten to damage tissue (70% of receptors in the dorsal root ganglion); all innervation to tooth pulp and cornea

Front 34

what are the two types of nociceptors?

Back 34

A-mechanonociceptors (axon myelinated)
Polymodal nociceptors (axon unmyelinated)

Front 35

A-mechanonociceptors

Back 35

respond to intense mechanical force, sometimes intense heat; free nerve endings; small receptive fields; slowly adapting response; mediate fast, initial pain, sharp "prickling" quality; easy to localize

Front 36

polymodal nociceptors

Back 36

respond to intense mechanical force, high heat, noxious chemicals; free nerve endings, no sheath; small receptive fields; slowly adapting response; mediate slow, aching, "burning" quality of pain; difficult to localize

Front 37

dorsal columns

Back 37

(1) fasciculus gracilis
(2) fasciculus cuneatus
convey tactile, vibration, joint position information to brain

Front 38

anterolateral tracts

Back 38

convey pain, temperature info to brain

Front 39

dorsal horn

Back 39

receives sensory input

Front 40

ventral horn

Back 40

contains motor neurons that send efferent info to muscles

Front 41

Laminae I/II

Back 41

receive nociceptive primary afferent input from dorsal roots (Marginal zone & substantia gelatinosa)

Front 42

Laminae III/IV

Back 42

receive tactile/vibration afferent input from dorsal roots

Front 43

what does damage to the dorsal column system pathway cause?

Back 43

loss in fine touch and vibration sensation carried by the dorsal column on the same side immediately below the spinal level of the lesion

Front 44

dorsal column system

Back 44

relays somatosensory input from body (neck-toes) to cortex; relays input about 2-point discrimination, fine touch, vibration and limb position

Front 45

what is the primary afferent input to the dorsal column system?

Back 45

all mechanoreceptors afferents that mediate fine touch (Merkel, Meissner, Pacinian, Ruffini, hair follicle afferents)

Front 46

how many segments are in the human spinal cord?

Back 46

31 (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)

Front 47

what arteries supply the lateral aspects of the midbrain (including the corticospinal tract)?

Back 47

PCA (posterior cerebral artery) and the superior cerebellar artery

Front 48

what arteries supply the medial aspect of the midbrain?

Back 48

basilar artery and posterior communicating artery

Front 49

what artery supplies the lateral aspect of the caudal medulla?

Back 49

posterior spinal a.

Front 50

what arteries supply the medial aspects of the caudal medulla (including the corticospinal tract)?

Back 50

anterior spinal a. and penetrating branches of the vertebral a.

Front 51

what arteries supply the lateral aspects of the rostral medulla?

Back 51

vertebral a. and posterior inferior cerebellar a. (PICA)

Front 52

what arteries supply the medial aspect of rostral medulla?

Back 52

anterior spinal a. and penetrating branches of the vertebral a.

Front 53

what arteries supply the pontine tegmentum and dorsolateral quadrant of the pons?

Back 53

anterior inferior cerebellar a. (AICA), long circumferential branches of the basilar a. and the superior cerebellar a.

Front 54

what artery supplies the lateral aspect of the rostral pons?

Back 54

superior cerebellar a.

Front 55

occlusion of PCA

Back 55

Weber's syndrome

Front 56

occlusion of superior cerebellar a.

Back 56

lateral pontine syndromes

Front 57

cervical enlargement

Back 57

extends from C5 to T1; supplies the upper extremities

Front 58

lumbar enlargement

Back 58

extends from L2 to S3; supplies the lower extremities

Front 59

condus medullaris

Back 59

the conical termination of the sacral spinal cord, located between the L1 and L2 vertebrae

Front 60

filum terminale

Back 60

a condensation of pia mater from the conus medullaris to the coccygeal ligament

Front 61

cauda equina

Back 61

large number of lumbosacral roots surrounding the filum terminale

Front 62

dermatome for upper arm (lateral surface)?

Back 62

C5

Front 63

dermatome for thumb and lateral forearm?

Back 63

C6

Front 64

dermatome for middle finger?

Back 64

C7

Front 65

dermatome for little finger?

Back 65

C8

Front 66

dermatome for nipple?

Back 66

T4

Front 67

dermatome for umbilicus?

Back 67

T10

Front 68

dermatome for big toe?

Back 68

L5

Front 69

dermatome for heel?

Back 69

S1

Front 70

dermatome for back of thigh?

Back 70

S2

Front 71

gray matter is divided into ____ and white matter is divided into ____

Back 71

horns
funiculi

Front 72

anterolateral sulcus

Back 72

marks the exit of the ventral roots

Front 73

posterolateral sulcus

Back 73

marks the entry of the dorsal roots

Front 74

dorsal horn

Back 74

sensory (receives sensory input; mediates synapses; neurons give rise to ascending efferent pathways)

Front 75

ventral horn

Back 75

motor (houses alpha motoneurons, gamma motoneurons, and interneurons; neurons innervate extrafusal and intrafusal muscle fibers)

Front 76

lateral horn

Back 76

intermediolateral cell column from T1 to L2-3; thoracolumbar sympathetic outflow

Front 77

the intermediolateral cell column from T1 to L2-3 gives rise to what type of fibers and where do they synapse?

Back 77

preganglionic sympathetic that synapse in the paravertebral and prevertebral ganglia

Front 78

what types of neuron fibers are found from S2-4 and where do they synapse?

Back 78

preganglionic parasympathetic that synapse in terminal ganglia within walls of the pelvic viscera

Front 79

dorsal root lesions

Back 79

hypesthesia or anesthesia

Front 80

ventral root lesions

Back 80

may lead to complete flaccid paralysis and atrophy of the muscles; involvement of autonomic preganglionic fibers may result in autonomic dysfunction

Front 81

spinal cord transection

Back 81

destruction of ascending and/or descending tracts produces sensory, motor, or mixed deficits

Front 82

Rexed's Lamination

Back 82

subdivides the gray matter into 9 (I-IX) laminae plus area X surrounding the central canal
I-V=sensory (I & II=pain & temperature)
V=dorsal nucleus of Clark
IX=groups of motor neurons

Front 83

spinal cord hemisection (Brown-Sequard Syndrome)

Back 83

(1) loss of fine touch, vibration and proprioception ipsilateral to & below lesion
(2) loss of pain & temperature contralateral to & below lesion
(3) spastic paralysis ipsilateral to & below lesion

Front 84

syringomyelia

Back 84

damage to crossing fibers around the central canal

Front 85

spinal shock

Back 85

flaccid paralysis and anesthesia initially (acute), over time there is spastic paralysis and pain sensation (chronic)

Front 86

lesion

Back 86

a zone of localized dysfunction with the CNS or PNS

Front 87

T/F somatosensory information above the lesion in that pathway is intact

Back 87

true

Front 88

what deficits occur with a lesion on one entire side of cord?

Back 88

(1) ipsilateral loss of fine discrimination, joint position, vibration below lesion
(2) contralateral loss of pain and temperature by 2-3 segments below lesion
(3) minor loss of crude touch

Front 89

an alternating sensory loss in body (fine discrimination loss on one side; pain and temperature loss on the other) indicates what type of lesion?

Back 89

unilateral

Front 90

what deficits result from lesions in brainstem (above caudal medulla) or higher?

Back 90

contralateral loss of both tactile and pain/temp in body

Front 91

white matter increases caudal to rostral OR rostral to caudal

Back 91

caudal to rostral

Front 92

function of thalamus

Back 92

processes and relays information between sensory or motor systems and the cerebral cortex

Front 93

function of hypothalamus

Back 93

regulates endocrine system by influencing secretion of the pituitary gland; involved with the autonomic nervous system; makes numerous connections with other parts of the brain

Front 94

function of pineal gland

Back 94

secretes melatonin

Front 95

medial geniculate nucleus (MGN)

Back 95

located at the posterior pole of the thalamus just lateral to the superior colliculus; function = relay in the AUDITORY pathway

Front 96

lateral geniculate nucleus (LGN)

Back 96

located at the posterior pole of the thalamus in the region of the superior and inferior colliculi; function = relay in the VISUAL pathway

Front 97

the midbrain is divided into what two regions by the cerebral aqueduct?

Back 97

(1) tectum
(2) tegmentum

Front 98

tectum

Back 98

superior (dorsal) to the cerebral aqueduct and consists of two bumps (superior colliculi-VISUAL relay and reflexes and inferior colliculi-AUDITORY relay and reflexes)

Front 99

cerebral peduncles

Back 99

bundles of nerve fibers that make up two halves of the midbrain

Front 100

interpeduncular fossa

Back 100

part of the subarachnoid space located between the cerebral peduncles; ventral side of midbrain; contains mamillary bodies and oculomotor nerves

Front 101

pons

Back 101

middle part of the brainstem characterized by narrow transverse grooves and elevations

Front 102

medullary pyramids

Back 102

elongated elevations on the anterior surface of the medulla on either side of the midline; function=ipsilateral fiber tracts carrying motor information from the primary motor cortex en route to the spinal cord

Front 103

pyramidal decussation

Back 103

the region where pyramidal fibers cross the midline of the medulla located at the inferior end of the medulla just superior to the spinal cord

Front 104

olives

Back 104

elevations just lateral to the pyramids

Front 105

substantia nigra

Back 105

heavily pigmented nuclear mass within the cerebral peduncle

Front 106

crus cerebri

Back 106

ventral part of the cerebral peduncle; consists of several fiber tracts

Front 107

red nucleus

Back 107

oval structure centrally located within the midbrain tegmentum; dark in color due to its vascularity; functions as a relay between the cerebral and cerebellar cortices and the spinal cord

Front 108

CN III-oculomotor

Back 108

located in the midline, just superior to the pons; emerge from the interpeduncular fossa b/t the posterior cerebral and superior cerebellar arteries

Front 109

CN IV-trochlear

Back 109

only CNs to emerge from the dorsal surface of brainstem (just below each inferior colliculus)

Front 110

CN V-trigeminal

Back 110

emerge from the lateral sides of the pons

Front 111

CN VI-abducent

Back 111

located near the midline, they emerge at the jx of pons w/ medulla

Front 112

spinal neurons

Back 112

gray matter on inside of spinal cord contains cell bodies of neurons

Front 113

nucleus or nuclei

Back 113

clusters of neuronal cell bodies that connect functional systems

Front 114

tracts

Back 114

bundles of projecting axons that have similar connections course through the white matter on the outside of the spinal cord; sensory tracts transmit sensory information up toward the brain; motor tracts transmit information down toward muscles

Front 115

lumbar: fasciculus gracilis or cuneatus?

Back 115

fasciculus gracilis only

Front 116

thoracic: fasciculus gracilis or cuneatus?

Back 116

T7 and below: fasciculus gracilis only
T6 and above: both

Front 117

cervical: fasciculus cuneatus or gracilis?

Back 117

both

Front 118

somatotopy of axons in dorsal columns

Back 118

medial -> lateral
leg -> trunk -> arm -> neck

Front 119

VPL nucleus receives input from which two systems?

Back 119

spinothalamic & dorsal column medial lemniscal

Front 120

what are the three major tracts involved in the anterolateral system?

Back 120

(1) spinothalamic tract
(2) spinoreticular tract
(3) spinomesencephalic tract

Front 121

central lateral nucleus of thalamus

Back 121

3rd order axons project to many areas of cortex, particularly limbic cortex (affect/mood); involved in emotional suffering

Front 122

functions of thalamus

Back 122

(1) process nociceptive information
(2) relay information to cerebral cortex by 3rd order neurons that pass through posterior limb of internal capsule and corona radiata

Front 123

rod monochromacy

Back 123

rare hereditary condition d/t absence of cone-based vision in the eye; rod monochromats experience glare in bright conditions (photophobia); acuity is very poor (20/200 at its best); poor fixation, nystagmus, visual field defects and serious refractive errors

Front 124

what causes rod monochromacy?

Back 124

mutations in CNG channel subunits or GNAT2 (cone transducin), so cones are unable to hyperpolarize in response to light

Front 125

red-green dichromacy

Back 125

missing the function of one of the three cone types

Front 126

what types of dichromacy are sex-linked?

Back 126

protanopia
deuteranopia
(inherited recessively through the L/M gene array located on the X chromosome)

Front 127

characteristics of congenital color vision defects

Back 127

present at birth
type and severity same throughout life
type can be classified precisely
both eyes equally affected
visual acuity is unaffected
predominantly protan or deutan
higher incidence in males

Front 128

characteristics of acquired color vision defects

Back 128

onset after birth
type/severity can fluctuate
type not easily classified -combined defects
monocular differences often occur
visual acuity is often reduced
predominantly tritan
equal incidence in males/females

Front 129

Usher's syndrome

Back 129

most common form of deaf-blindness; progressive vision and hearing loss, also associated with reduced odor identification, vestibular dysfunction, and reduced sperm motility; in general, defects with sensory cilia (proteins found in actin core of stereocilia and the CC & Calycal process)

Front 130

retinitis pigmentosa

Back 130

primary rod loss
autosomal dominant
have difficulty seeing in dim light
have a gradual peripheral vision loss
lots of glare
lots of contrast sensitivity

Front 131

what is the function of the geniculostriate system?

Back 131

conscious visual perception (helps you understand what you are seeing)

Front 132

what is the function of the retinotectal system?

Back 132

directing eye movements and visual attention (helps you not to miss important things)

Front 133

geniculostriate system pathway

Back 133

retina (ganglion cells) -> CN II -> optic chiasm -> optic tract -> lateral geniculate nucleus (LGN) -> optic radiation/Meyer's loop -> VI (primary visual cortex, Brodmann's area 17 & 18), extra striate cortex

Front 134

retino-tectal system

Back 134

retina (ganglion cells) -> CN II -> optic chiasm -> optic tract -> superior colliculi -> pulvinar nucleus of thalamus -> extra striate cortex

Front 135

what is a common side effect of temporal lobectomies?

Back 135

damage to the temporal lobe could damage Myers' loop and produce a restricted visual field defect

Front 136

what is the function of the pupillary control system?

Back 136

pupillary control of light intensity

Front 137

consensual light reflex

Back 137

bilateral control of constriction even if light enters only one eye due to linkage via the posterior commissure

Front 138

pathway for pupillary constriction

Back 138

retina -> CN II -> pregeniculate body -> pretectal area -> edinger-westphal nucleus -> CN III -> ciliary ganglion -> constrictor pupillae muscle

Front 139

why can emotion cause dilation?

Back 139

dilation pathway has input from arousal systems via the sympathetic autonomic system

Front 140

pathway for pupillary dilation

Back 140

retina -> CN II -> midbrain reticular formation -> thoracic cord -> (sympathetic ganglion) -> superior cervical ganglion -> dilator pupillae mm.

Front 141

what is accommodation?

Back 141

focusing the eye

Front 142

what does contraction of ciliary muscle cause?

Back 142

thickening of the lens

Front 143

what three things happen when visual attention is directed to a nearby object?

Back 143

(1) convergence of the two eyes (so the image of the object falls on both foveae)
(2) contraction of the ciliary muscle to thicken the lens (increase in optical power)
(3) pupillary constriction (increase depth of field)

Front 144

how does the accommodation reflex differ from the pupillary reflex?

Back 144

-can be voluntarily controlled
-regulated by a "negative feedback" mechanism that automatically adjusts the focal power of the lens
-pathway includes cerebral cortex (to determine if the image is blurry)

Front 145

what does cortical magnification refer to?

Back 145

fovea is over-represented in the calcarine cortex; corresponds to enhanced acuity at the center of gaze; lesions of visual cortex that affect the foveal representation result in severe deficits for the patients, while lesions in the periphery can go unnoticed

Front 146

hemianopia

Back 146

loss of vision in a hemifield

Front 147

quadrantanopia

Back 147

loss in a quadrant

Front 148

homonymous

Back 148

corresponding loss in each eye

Front 149

heteronomous

Back 149

non-corresponding loss in each eye

Front 150

what is the basis for fMRI?

Back 150

flickering annulus=as the annulus expands, you activate different photoreceptors at greater eccentricities; measure the brain response (for which site responds best); used to predict which area would be affected by resecting a tumore

Front 151

what are the two specialized systems of the extrastriate visual areas?

Back 151

(1) Termporal lobe pathways for recognition of objects ("what is it?")
(2) Parietal lobe pathways for localization ("where is it?") - involved in directing visual attention to an object of interest (lesion= "attentional neglect")

Front 152

lesion of hMT+

Back 152

results in motion blindness

Front 153

lesion of V1 (striate cortex)

Back 153

causes blindness

Front 154

lesion of V2 (fusiform face area)

Back 154

causes inability to recognize faces (prosopagnosia)

Front 155

lesion of V4/V8

Back 155

loss of color vision (cerebral achromatopsia)

Front 156

lesion of PVA (primarily right side)

Back 156

attentional neglect (primarily on the left side of fixation of objects)

Front 157

rhizotomy

Back 157

surgical cutting of dorsal roots; used for pain relief, b/c adjacent dorsal root territories overlap, surgeons typically cut dorsal roots adjacent to affected dermatome; lose fine discrimination, joint position, vibration, pain/temperature in dermatome innervated by cut dorsal roots

Front 158

cordotomy

Back 158

surgical cutting of anterolateral fiber tracts in spinal cord; used for pain relief of terminally ill, cut 2-3 segments above dermatome where highest level of pain begins; if cut 1 side=lose pain & temp on contralateral side; pain often recurs w/i 6 mo

Front 159

what is the basis of age related macular degeneration (AMD)?

Back 159

progressive loss of central visual field; degeneration of macular cones

Front 160

dry form AMD

Back 160

90%; accumulation of drusen (lipid and protein) in Bruch’s membrane between the choroid and RPE -> macular RPE atrophy

Front 161

wet form AMD

Back 161

10%; coroidal neovascularization (growing too many blood vessels -> damages cones)

Front 162

somatic motor - function?

Back 162

innervate skeletal muscles in the head and neck that are derived from myotomes

Front 163

branchial motor - function?

Back 163

innervate skeletal muscles derived from branchial arches: muscles of mastication, facial expression, pharynx, larynx, middle ear, trapezius m.

Front 164

visceral motor - function?

Back 164

preganglionic parasympathetic innervation to cardiac m, smooth m, and glands

Front 165

visceral sensory - function?

Back 165

special - taste
general - control of cardiorespiratory and digestive functions

Front 166

somatic sensory - function?

Back 166

convey touch, pain, temperature, position and vibration from skin, muscles and joints of the head

Front 167

special sensory - function?

Back 167

hearing and balance

Front 168

somatic motor - brainstem nuclei & CN?

Back 168

oculomotor - III
trochlear - IV
abducens - VI
hypoglossal - XII

Front 169

branchial motor - brainstem nuclei & CN?

Back 169

motor nucleus of V - V
facial nucleus - VII
nucleus ambiguus - IX and X
spinal accessory nucleus - XI

Front 170

visceral motor - brainstem nuclei & CN?

Back 170

Edinger-Westphal - III
superior salivatory - VII
inferior salivatory - IX
dorsal motor nucleus of X - X

Front 171

visceral sensory (special) - brainstem nuclei & CN?

Back 171

rostral nucleus solitarius (gustatory nucleus) - VII, IX and X

Front 172

visceral sensory (general) - brainstem nuclei & CN?

Back 172

caudal nucleus solitarius (cardiorespiratory nucleus) - IX and X

Front 173

somatic sensory - brainstem nuclei & CN?

Back 173

trigeminal nucleus - V, VII, IX, and X

Front 174

special sensory - brainstem nuclei & CN?

Back 174

cochlear nucleus - VII
vestibular nucleus - VIII

Front 175

brainstem functions (3)?

Back 175

(1) integrative: regulate consciousness as well as motor, respiratory and cardiovascular fx (reticular formation)
(2) conduit: ascending sensory and descending motor tracts pass through brainstem
(3) cranial nerve functions:
-CNs emanate from brainstem
-cell bodies of CNs are located in brainstem
-CN nuclei are arranged in functional columns

Front 176

where are nociceptors located?

Back 176

skin, muscle, joints, bone and internal visceral organs

Front 177

what type of pain do A-delta fibers mediate?

Back 177

first pain (immediate, short-lasting, pricking quality)

Front 178

what type of pain do C fibers mediate?

Back 178

second pain (delayed, long lasting, burning quality)

Front 179

primary neurons - anterolateral system

Back 179

enter spinal cord dorsal horn (lateral part) and synapse in Lamina I/II (marginal zone and substantia gelatinosa); some synapse on Lamina V and few near central canal (Lamina X) (NT=substance P and glutamate)

Front 180

secondary neurons - anterolateral system

Back 180

cross to contralateral side of spinal cord with 2-3 segments and ascend in ventrolateral funiculus

Front 181

three major pathways for termination in higher brain centers - anterolateral system

Back 181

1) spinothalamic tract
2) spinoreticular tract
3) spinomesencephalic tract

Front 182

spinothalamic tract

Back 182

majority of 2nd order ascending fibers terminate in the thalamus; mediates discriminative aspects of pain and temp sensation, such as location and intensity of the noxious stimulus; in the thalamus, axons terminate in:
(1) VPL nucleus
(2) Central lateral nucleus

Front 183

VPL nucleus of the thalamus

Back 183

3rd order axons project to ipsilateral SI cortex; principle relay nucleus for discriminative somatosensory info from body (neck-toes); somatotopically organized

Front 184

central lateral nucleus of the thalamus

Back 184

3rd order axons project to many areas of cortex, particularly limbic cortex (affect/emotion); involved in emotional suffering, not somatotopically organized

Front 185

where do 3rd order neurons pass through on the way to the SI cortex (spinothalamic tract)?

Back 185

posterior limb of internal capsule and corona radiata

Front 186

spinoreticular tract

Back 186

2nd order axons ascend from spinal cord and terminate in medulla and pons in a region called the reticular formation; other axons then relay info from reticular formation to thalamus and diffusely to many areas of the cortex; mediates changes in level of attention to painful stimuli and involved with forebrain arousal and affective response

Front 187

spinomesencephalic tract

Back 187

some 2nd order axons terminate in the midbrain in the superior colliculus and in a region of gray matter surrounding the cerebral aqueduct (Periaqueductal Gray - PAG); activation leads to stimulating the central modulation of pain

Front 188

what areas of the cortex do thalamic neurons project to (pain stimulus)?

Back 188

(1) somatosensory cortex: SI areas 3b, 1, 2 and also SII (help localize stimulus on body)
(2) cingulate gyrus: part of limbic system (processes emotional component)
(3) insular cortex: processes info on the internal, autonomic state of body; integrates sensory, affective, and cognitive components of pain

Front 189

what happens with a lesion of the insular cortex?

Back 189

asymbolia for pain (patients can perceive noxious stimuli as painful and localize the pain to a body part, but don't display appropriate emotional responses to pain)

Front 190

mechanism for endogenous pain control

Back 190

spinomesencephalic ascending pathway activates the PAG (periaqueductal gray) -> raphe nuclei (medulla) & locus ceruleus (pons) -> negative feedback down spinal cord (synapse on inhibitory interneurons which supress ascending signals)

Front 191

when do we see referred pain and why?

Back 191

visceral pain is poorly localized - refers to a dermatome innervated by the spinal segment to which the visceral afferent project; both signals synapse onto the same secondary spinothalamic neuron (convergence)

Front 192

anesthesia

Back 192

lack of sensation

Front 193

analgesia

Back 193

lack of pain

Front 194

athermia

Back 194

lack of thermal sensation

Front 195

hyperalgesia

Back 195

increased pain from normally painful stimulus

Front 196

allodynia

Back 196

pain from a normally non-painful stimulus, light touch

Front 197

hypoalgesia

Back 197

decreased pain from normally painful stimulus

Front 198

paresthesia

Back 198

unpleasant, abnormal sensation; tingling, prickling, tickling

Front 199

pruritus

Back 199

itching

Front 200

acute pain

Back 200

serves critical function; warning that injury should be avoided or treated

Front 201

chronic pain

Back 201

when pain does not go away or adapt; pain continues after healing or in absence of apparent injury; serves no useful purpose

Front 202

nociceptive pain

Back 202

pain resulting from tissue damage; well-localized, throbbing quality, activation of nociceptors and release of inflammatory chemicals that act on C fibers

Front 203

what kinds of drugs are used for nociceptive pain?

Back 203

NSAIDs, opioid drugs

Front 204

neuropathic pain

Back 204

direct damage to nerves in the peripheral or central nervous system; often has burning, lancinating, electrical quality

Front 205

what kinds of drugs are used for neuropathic pain?

Back 205

tricyclic antidepressants, anticonvulsants

Front 206

examples of neuropathic pain

Back 206

-post herpetic neuralgia following shingles
-diabetic neuropathy
-entrapment neuropathy (carpal tunnel syndrome)

Front 207

examples of nociceptive pain

Back 207

mild: sprained ankle, infected cut, diaper rash
more severe: rheumatoid arthritis, tumor that invades skin or soft tissue, bone fracture

Front 208

the trigeminal nerve contains peripheral afferent neurons that innervate what areas?

Back 208

face, head, nasal sinuses, inside of nose, mouth (inc. teeth and gums) and anterior 2/3 of tongue

Front 209

what are the three divisions of the trigeminal nerve?

Back 209

(1) opthalmic: nose, nasal cavity, forehead, top head
(2) maxillary: upper jaw, lip, teeth; cheek
(3) mandibular: lower jaw, lip, teeth; chin

Front 210

trigeminal nucleus for fine touch?

Back 210

main (chief or principle) sensory nucleus located in pons

Front 211

trigeminal nucleus for pain/temp?

Back 211

spinal trigeminal nucleus extending from pons down to cervical spinal cord

Front 212

thalamic relay nuclei for trigeminal sensory system?

Back 212

ventral posterior medial nucleus (both fine touch, pain and temp info go through VPM - stay segregated)

Front 213

somatotopy of head and face in VPM

Back 213

tongue is medial, face is lateral

Front 214

what is the pathway for trigeminal discriminative touch?

Back 214

fine touch receptors enter pons and synapse in chief sensory nucleus V -> 2nd order neurons cross to contralateral pons and form trigeminal lemniscus -> ascend to the VPM nucleus in thalmus -> 3rd order neurons project from VPM to lateral SI cortex

Front 215

what is the minor pathway for crude touch in the trigeminal pathway?

Back 215

some mechanoreceptors enter the pons and descend down the spinal tract of V & synapse there -> second order neurons then send fibers that cross the midline and ascend in the trigeminothalamic tract to the VPM

Front 216

what is the minor pathway for the oral cavity?

Back 216

dorsal trigeminal tract; second order neurons don't cross but ascend on the ipsilateral side to the ipsilateral VPM (bilateral representation)

Front 217

what is the pain/temp pathway for the trigeminal system?

Back 217

primary neuron=nociceptor -> enter in the V in the pons, but do not synapse -> fibers descend ipsilaterally in the spinal trigeminal tract -> synapse in the spinal trigeminal nucleus in the caudal medulla -> secondary neuron crosses to the contralateral medulla and ascends to the VPM (ascends as the trigeminalthalamic tract -> joins up w/ spinalthalamic tract of body) -> tertiary neuron goes to SI cortex through lateral part of the posterior limb of the internal capsule, some project to reticular formation

Front 218

trigeminal neuralgia

Back 218

a lancinating, severe pain that lasts seconds to minutes, episodes brought on my chewing or shaving or touching trigger points on the face; unknown etiology; fine touch, vibration, facial sensation is normal

Front 219

patients with alternating sensory loss indicates what type of lesion?

Back 219

unilateral

Front 220

glove and stocking loss (peripheral neuropathy)

Back 220

affects multiple dermatomes (most likely caused by diabetes and metabolic disease); lack of fine discrimination, pain and temp in skin, only in parts of limbs

Front 221

complete cord transection

Back 221

bilateral loss of all sensation (tactile and pain) below lesion (also loss of motor control); cause - trauma, fracture or dislocated vertebrae that causes cord compression, penetrating injury, tumor

Front 222

anterior cord syndrome

Back 222

bilateral loss of pain and temp below lesion, but fine discrimination, vibration, joint position ok; possible cause: anterior spinal artery embolism

Front 223

posterior cord syndrome

Back 223

loss of fine discrimination, vibration, and joint position below level of lesion, but pain and temperature ok

Front 224

central cord syndrome (small lesion)

Back 224

cuts anterolateral fibers that cross spinal cord in ant commissure; usually affects only the dermatomes of the spinal segments that have the lesion; presents with "cape-like" sensory loss of pain and temp in upper arms and shoulders

Front 225

unilateral lesion in VPM of thalamus

Back 225

contralateral loss of fine discrimination and loss of pain and temperature in face, head

Front 226

unilateral lesion in VPL nucleus of thalamus

Back 226

contralateral loss of fine discrimination and pain/temp in body

Front 227

unilateral lesion in primary somatosensory I cortex

Back 227

contralateral loss of fine discrimination and pain/temp in body and/or face

Front 228

brain stem lesion in lateral medulla

Back 228

loss of pain/temp sensation in body on contralateral side
loss of pain/temp sensation in face on ipsilateral & contralateral sides
if lesion affects entire medulla on one side, get loss of fine touch in body on contralateral side (fine touch intact if medial lemniscus is not affected)