Exam 1 Flashcards
(116 cards)
1
Q
Neural crest cells become the
A
PNS (including dorsal root ganglia, schwann cells, ganglia of ANS and melanocytes)
2
Q
Neural tube becomes the
A
CNS- brainstem and spinal cord
3
Q
the corpus callosum is the…
A
bridge of commissural fibers
4
Q
the meningeal layer is present in the:
A
brain only - it is the true external layer over the brain
5
Q
what structure forms CSF?
A
the choroid plexus (500ml/day)
6
Q
Hydrocephalus is
A
obstructive blockage of the normal flow of CSF out the ventricular system
7
Q
Ligand gated channels
A
have local signals (EPSPs and IPSPs that are graded and decay)
8
Q
Voltage gate channels
A
have an all or non response to neurotransmitter release
9
Q
Habituation
A
increased benign stimulus will cause a smaller response
10
Q
sensitization
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intense, noxious stimuli will strengthen the response
11
Q
Long-term potentiation
A
sustained long-term increase in synaptic strength elicited by a brief, high frequency stimulation (tetanus)
- hippocampus
12
Q
Long-term depression
A
increase in synaptic strength elicited by low frequency tetanus
- studied in cerebellum
13
Q
sensory transduction
A
conversion of stimulus energy into neural energy (action potentials)
14
Q
stimulus energy is
A
mechanical, chemical and light
15
Q
if a receptor potential reaches threshold…
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an AP will happen
16
Q
Meissner’s corpuscles are found in the
A
dermis of the skin and are mechanoreceptors
- slow receptors, low threshold
17
Q
pacinian corpuscles are
A
sensitive to vibration and pressure in the skin. respond to sudden disturbances, especially vibration
-rapid acting receptors, high threshold
18
Q
what determines the frequency of the action potentials?
A
the intensity of the stimulus
19
Q
Rapidly adapting receptors:
A
respond only to onset or offset of stimulus
20
Q
slowly adapting receptors
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continue signaling for the duration of the stimulus
21
Q
receptive fields
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areas on the body that excite or inhibit the firing of a particular sensory neuron
22
Q
the tips of the fingers have the smallest receptive fields and the largest…
A
number of receptive fields per area
- most sensitive parts of the body
23
Q
the center of the receptive field is _________ and the periphery is __________
A
excitatory and inhibitory
24
Q
mechanoreceptors:
A
touch/pressure, proprioception and air waves
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photoreceptors
light
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chemoreceptors detect
smell, taste, blood gas levels
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thermoreceptors
heat and cold
28
Ia (A-alpha) fiber are the primary afferents for what?
muscle spindles
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Ib (A-alpha) fibers innervate what type of receptors?
GTOs
fast acting
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Type II fibers innervate
secondary afferents of muscle spindles, touch, pressure, vibration
fast acting
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Type III (A-delta) fibers
touch and pressure; pain and temp
- slow
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Type IV (C) fibers
pain and temperature; unmyelinated
must generate high intensity stimulation to generate an AP
- slow acting
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if a fiber type has slower conduction velocities...
more resistance to the flow of the current, less myelination, higher thersholds
34
Role of the Alpha motor neuron
innervate the extrafusal muscle fiber
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Role of the Gamma motor neuron
innervate the intrafusal muscle fiber
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Type I joint receptors are
SA, Low threshold
regulate muscle tone during mvmt
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Type II joint receptors are
RA, low threshold
info about beginning and end of movement- boost muscle tone at beginning
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Type III joint receptors are
SA, high threshold
sudden joint movement; reflex contraction to limit further movement
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Type IV joint receptors
are free nerve endings
SA, high threshold
contribute to flexion reflex or co-contraction pattern around joint to prevent further movement
40
Muscle spindles attach to the....
periphysium
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fibers that make up the bulk of muscle are referred to as
extrafusal muscle fibers
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contractile elements of muscle spindles are located...
at the poles/ends of fibers with centrally located nuclei
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Intrafusal muscle fibers are
fibers within the CT capsules
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Primary/dynamic sensory receptors are located in the
nuclear bags (nuclei clumped in the middle)
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primary/dynamic receptors
- responsive to movement, encode duration and velocity of stretch
- info carried to CNS by Type Ia fibers
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Secondary/static receptors
- located peripherally near contractile elements
- responsive to static muscle length
- info carried to CNS by Type II fibers
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Each contractile element of muscle spindles is innervated by:
gamma motor neuron
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activation of the gamma motor neuron
contraction of the contractile component; used to adjust the sensitivity of each receptor/reset noncontractile component
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receptors are specialized by their...
morphology
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lateral inhibition
excitation greatest at center of field, inhibitory at periphery
- sharpens peak of activity within brain
- occurs in dorsal column nuclei up to CNS
- presents in visual system
- serves to enhance distinction between two stimuli and aid in pattern recognition
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amplitude of the action potential
small diameter fibers have lower amplitude because potential changes across the membrane are smaller
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stimulus during stretch of the sensory receptors:
mechanical deformation of the afferent endings
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purpose of contraction of the intrafusal muscle fiber
to prevent unloading of the receptor during extrafusal muscle contraction
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alpha-gamma coactivation
during the alpha motor neuron firing, gamma motor neuron is also fired; results in muscle spindle adjustment that parallels contraction of the extrafusal muscle fiber
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stimulation of the gamma motor neurons aside from alpha-gamma co-activation:
- increase in sensitivity of both primary and secondary endings
- allows for fine-tuning of spindle as the difficult of the task increases
56
GTOs are...
- encased receptors
- at musculo-tendinous junctions
- combines with collagen of the epi and perimysium
- receptor is located at end of the Ib nerve fibers
- intertwines with collagen of receptor capsule
57
GTO response
- contraction of extrafusal fiber
- causes tension of collagen bundles
- compression of afferent nerve ending
- receptor potential activated--> AP
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T/F GTO is highly sensitive to small changes in muscle tension
True- provides continuous feedback to regulate muscle tension
59
GTOs have a ______ threshold to tension
high
- plays a protective role by inhibiting alpha motor neuron activation of contracting muscle with extremes (autogenic inhibition)
60
Primary thermal receptor
- free nerve ending in dermis
- continuous with A-delta and C fibers
- classified by response to cold/heat
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cold afferents respond to temp changes in the
10-33 degree celsius range
| travels over both A-delta and C fibers
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heat afferents respond to temperature changes in the
32-45 degree C range (some can respond >45)
| restricted to C fibers
63
Nociceptors
- dermal layers of skin and deep tissues
- free nerve ending
- primary stimulus: mechanical damage to tissues (temp extremes or distruction of tissues)
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C-polymodal nociceptors
- majority of cutaneous receptors (>90%)
- free nerve endings
- activated by thermal (45 degrees celsius), crushing, and chemicals
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A-delta mechanoreceptive nociceptors
- high threshold for stimulation with small receptive areas
- sharp pain stimulus
- hyperalgesia
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A-delta mechanothermal nociceptors
- max responsive with 45-53 degrees C, but can respond to those
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A-delta fibers are activated by
muscle stretch or contraction (ergoreceptive)
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C fibers are activated by
intense mechanical or chemical stimuli (ischemic muscle pain)
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joint receptors are activated by
- intense pressure and movement
| - sensitized by inflammation
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output of the retina is the
ganglion cell
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pathways carrying ascending sensory information enter the spinal cord at the
dorsal root of each spinal nerve
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dorsal column medial lemnsicus pathway carries modalities of
- conscious proprioception
- discriminative touch
- position sense
- vibratory sensations
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Kinesthesia
sense of perception of movement of joints
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stereognosis
ability to identify an object by feel (sensations of proprioceptione and discriminative touch musc be intact)
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unconscious proprioception is mediated by
spinocerebellar tracts
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First order neuron (DCML)
- cell body located in dorsal root ganglia from S5-C1
- pseudounipolar
- heavily myelinated
- ascend in fasciculus gracilis (from S5-T7) and cuneatus (from T6-C1)
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the two fasciculi comprising the dorsal/posterior columns
fasciculus gracilis and cuneatus
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second order neuron in ascending pathway (DCML)
- cell bodies in nucleus gracilis and cuneatus
- located at caudal medulla
- synapse
- axons of these fibers for IAF that cross to form contralateral medial lemniscus
- projects of VPL
79
the medial lemniscus projects to the
VPL
| ventral posterolateral nucleus of the thalamus
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Where does the dorsal-column medial lemniscus pathway decussate?
the caudal medulla
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3rd order neurons DCML
- cell bodies in VPL
- axons project through posterior limb of internal capsule to primary somatosensory (3,1,2)
- somatotopic organization
- index finger and tongue (greatest representation in this region)
82
Proprioception lower extremity
- includes nucleus of Z and Dorsal nucleus of clarke (T1-L2)
- extra neuron between DR ganglion and nucleus gracillis
- second neuron ascends ipsilaterally with dorsolateral fasciculus (with DSCT)
- synapse in nucleus X at rostral end of nucleus gracillis
- join IAF crossing to ascend as part of the contralateral medial lemniscus
83
spinothalamic carries what sensory modalities?
pain, temperature, non-discriminative touch for the body
84
trigeminothalamic path caries
pain and sensation for anterior 2/3 of the face, oral and nasal cavities
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lateral spinothalamic
carries pain and temperature
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First order neuron (LSTT)
- pseudounipolar
- cell body DR ganglion
- free nerve nedings
- A-delta fibers (prickling pain)
- enter laterally and bifurcate at Lissauer's tract
- could ascend or enter dorsal horn and synapse on neurons in substantia gelatinosa/nucleus proprius)
- neurotransmitter is glutamate
87
second order neuron (LSTT)
- somewhere in substantia gelatinosa
- cross midline through anterior white commissure to form LSTT
- lateral fibers Lower SC; medial fibers from higher levels of SC
- reaches VPL and intra-laminar thalamic nuclei (CM)
88
Third order neuron (LSTT)
- located in VPL
- axons maintain lateral and medial considerations (LE, UE)
- ascend to primary somatosensory cortex (sup. thalamic radiation)
- post central gyrus, areas 3, 1 and 2
- homunculus upside down hanging by lower limb with leg in midline cortex
89
spinoreticulothalamic path
- parallel LSTT
- synapse in reticular formation
- reaches medial and intralaminar thalamic nuclei projecting to cortical areas and limbic system
- limbic connects to hypothalamus influencing ANS
- emotional domain of pain and activates SNS response
90
Spinomesencephalic pathway
- parallels LSTT
- projects to superior colliculus and periaqueductal gray in midbrain
- activates descending pathways critical for modulating incoming stimuli
91
spinoreticulothalamic and spinomesencephalic pathways can activate...
descending pathways originating from Raphe nuclei (serotonin) and locus ceruleus (norepinephrine) of the reticular formation
- they modify painful sensations
92
anterior spinothalamic pathway carries sensation of
light or non-discriminative touch as well as pain sensation
| utilizes C fibers to carry sensation of burning pain
93
random second pathway in the ASTT
the second order neuron of the ASTT may travel up or down 10-12 segments before crossing through anterior white commissure
- once they cross they form the anterior spinothalamic pathway
- ascends to VPL
- carries non-specific temperature information
94
trigeminal nerve sensory component
- pain, temperature, light touch and discriminative touch
| - conscious and unconscious proprioception to anterior 2/3 of the face
95
which components of the trigeminal nerve are exclusively sensory
V1 and V2
| V3 is the motor to muscles of mastication
96
first order neuron (trigeminal pain and temp)
- cell body in trigeminal ganglia
- A-delta and C fibers
- enter spinal tract of V (mid pons)
- descend ipsilaterally to spinal trigeminal nucleus in medulla
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second order neuron (trigeminal pain and temp)
- cell body in spinal nucleus of V( middle/caudal pons adjacent to tract)
- 3 divisions to this nucleus
- cross midline and line up adjacent to ML
- ascends contralaterally as ventral trigeminal thalamic tract
- synapses in VPM
98
third order neuron of the ventral trigeminal thalamic tract (pain and temp)
- cell body in VPM (medial division)
- ascend to cortex in posterior limb of internal capsule
- terminate or synapse in face area of primary somatosensory cortex (3, 1 and 2)
99
trigeminal neuralgia
excrutiating pain set off only by mild stimulation
100
first order neuron (trigeminal proprioception/ discriminative touch)
- cell bodies in trigeminal ganglia (like with pain and temp)
- pathway similar to pain and temp for this branch
101
second order neuron (trigeminal proprioception/ discriminative touch)
- cell bodies in main sensory nucleus V
- 2 point discrimination of trigeminal nerve
- axons cross midline and ascend with VTT)
- extra pathway ascends ipsilaterally DTT
- ascend to VPM
102
3rd order neurons (trigeminal proprioception/ discriminative touch)
- cell bodies in VMP thalamic nucleus
| - ascend to posterior limb of internal capsule to synapse in primary somatosensory cortex (3, 1, 2)
103
Mesencephalic nucleus of V houses
first order neurons for conscious proprioception of the trigeminal nerve
104
Myotatic reflex
- involves descending component from mesencephalic nucleus in jaw-jerk reflex
- only one synapse- afferent and efferent limbs (LMN)
105
ionotropic neurotransmitters
receptors are localized with actual ion channel
- fast neurotransmitters
- excitatory (Ach, glutamate, epinephrine)
- inhibitory (GAMA, glycine)
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metabotropic neurotransmitters
- receptors located on membrane
| - activate ion channel via second messenger system
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neuropeptides
metabotropic
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neurotransmitters are colocalized with __________ in axonal terminals
neuropeptides
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what determines the action of the neurotransmitter?
the post-synaptic receptor (excitatory vs. inhibitory)
110
fast neurotransmitters are associated with
ionotropic receptors but they also act on metabotropic
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tendon organ reflex
protective mechanism where GTO inhibits max contacting muscle to avoid injury (autogenic inhibition)
112
reciprocal facilitation
activation of the antagonist muscle to facilitate the release of tension
113
flexor withdrawal
where ipsilateral flexors perform withdrawal while contralateral extensors help stabilize
114
Merkel cells
mechanoreceptors found in epidermis (slow adapting type 1)
| - provide info on pressure, position and deep static touch
115
Meissner's corpuslces
- mechanoreceptor in the skin responsible for light touch (highest sensitivity when sensing vibration 10-50Hz)
- rapidly adapting (like pacinian)
116
Ruffinin endings
- slowly adapting mechanoreceptors
- enlarged dendritic endings with elongated capsules
- sensitive to skin stretch
