Patho Flashcards
1
Q
What are concentrated in the Nodes of Ranvier?
A
Voltage-gated Na Channels
2
Q
What layer of the peripheral nerve aids regeneration of neurons?
A
Endoneurium
Does not extend into the CNS which is why limited regeneration occurs in CNS
3
Q
What are fascicles? What surrounds them?
A
bundles of nerves composed of endoneurium & blood vessels
surrounded by perineurium
4
Q
What do oligodendrocytes form? Where are they located?
A
Form myelin in the CNS
5
Q
How are oligodendrocytes of CNS different than the schwann cells of PNS?
A
Oligodendrocytes cover multiple axons at once; schwann cells cover a single axon
6
Q
What do astrocytes to in CNS (5 functions)? What types of matter are they composed of?
A
Function:
- waste & metabolite transport
- uptake of neurotransmitter (regulate synaptic activity)
- ion concentration regulation
- maintains tight junctions between capillaries that forms BBB
- role in repair and scarring in brain
Astrocytes are composed of grey matter
7
Q
What is gliosis?
A
When astrocytes fill cytoplasm with microfibrils forming special scar tissue in CNS when tissue is destroyed
8
Q
Job of microglia?
A
phagocytic cell that cleans up debris after cell damage, infection, or cell death
9
Q
Function of ependymal cells?
A
Forms lining of neural tube cavity (the ventricle system)
In some areas, ependymal cells combine with a rich vascular network to form the choroid plexus where CSF production occurs
10
Q
Briefly describe an AP.
A
- cell at rest (-90mV)
- stimulus occurs
- nerve depolarized to threshold potential (-60mV)
- Na channels open and Na floods into the cell further depolarizing cell (+30mV)
- inactivation gate on Na voltage gated channels close
- K channels open & K floods out of cell repolarizing cell
11
Q
Phases of an action potential?
A
- depolarization
- overshoot
- repolarization
- resting/polarized
12
Q
Excitatory neurotransmitters (6)
A
- ACh
- Serotonin
- Dopamine
- NE
- Epi
- Glutamate
13
Q
Inhibitory neurotransmitters (2)
A
glycine
GABA
14
Q
Neuropeptides (pain sensation and perception)
A
Neuromodulators & neurohormones - modify work of other NT
substance P
endophins
enkephalins
15
Q
_____ neurons of the CNS have short preganglionic neurons that release __2__ and act on __3__ receptors of ___4____ postganglionic neurons that release __5___ or ___5___.
A
- Sympathetic
- ACh
- N2 receptors
- long
- ACh or NE
16
Q
__1__ neurons of the CNS have long preganglionic neurons that release __2__ to act on __3__ receptors of ___4___ postganglionic neurons, that release __5____.
A
- Parasympathetic
- ACh
- N2
- short
- ACh
17
Q
__1__ neurons have single __2___ that release __3__ to act on __4__ receptors of ___5__.
A
- Somatic
- motoneuron
- ACh
- N2
- Skeletal muscle
18
Q
When stimulated by a motoneuron, the nicotinic 2 receptor, activated by ACh, opens what ion channels?
A
Na & K
19
Q
Sequence of events in neuromuscular transmission (7)
A
- AP travels down motoneuron to presynaptic terminal
- depolarization opens Ca channels, and Ca flows INTO the presynaptic terminal
- Exocytosis of ACh
- ACh binds N2 on motor end plate
- Na and K channels open
- depolarization of motor end plate causes AP in muscle
- ACh degraded to choline and acetate by acetylcholinesterase and reuptake occurs by Na-choline cotransporter
20
Q
Most common type of intracranial neuroepithelial type tumor?
A
Astrocytoma (80%) - neuroglial tumor
21
Q
What is medulloblastoma?
A
cancer of blastocytes in cerebellum (undifferentiated cells) in infants and children
22
Q
What percentages of the bodies O2 does the brain use? What percentage of the cardiac output does it receive?
A
O2: 20%
CO: 15%
without O2 cells stop functioning in 10s and die in 4-6 min
23
Q
What is the major fuel source of the brain?
A
glucose
no glycogen stores (like muscle cells) so relies on blood supply and glial cell stores
24
Q
describe the hierarchy of control
A
the forebrain controls the brainstem
and
the brainstem controls the spinal cord
dominance of forebrain because it is made later in development, more specialized, and built from earlier structures
newer functions added onto older functions anteriorly, making them more vulnerable to injury
25
what does the ectoderm create during neural development?
- neural plate (primordial nervous system)
| - neural tube
26
What does the neural crest become as it moves rostrally?
- neurons
- support cells of PNS
- 10 most rostral segments (fore brain, mid brain, hind brain)
27
what is the neural plate the primordial of?
nervous system
28
what does the neural tube become?
CNS
29
what is the soma?
skin, muscle, and skeletal structures of body wall innervated by somatic nervous system
30
what innervates the viscera?
autonomic nervous system
31
List the 5 cell column types.
```
Dorsal Root Ganglia
Dorsal Horn cell column
ventral horn cell column
sympathetic chain ganglia
parasymphathetic chain ganglia
```
32
Name the 4 cell columns contained within the dorsal root ganglia.
special somatic afferent
general somatic afferent
special visceral afferent
general visceral afferent
33
What information do the special somatic afferents convey & where are they located? Where are their receptors located?
internal sensory information
i.e. joint & tendon sensation, proprioception, position, posture and movement of body
SSA are located in dorsal root ganglia
receptors primarily located in muscles, tendons, and joints
34
What information do special sensory IA cell column relay? Where to they originate?
the IA cell columns relay information (from the special sensory afferents in the dorsal ganglion) to reflexes concerned with posture and movement
they also send information to:
- the cerebellum (for coordination of movement)
- the forebrain (contributes to the experience of the information)
they are originate in the dorsal horn column
35
what do general somatic afferents innervate? what is their distribution? what information do they convey? where are they located?
they innervate the skin & other somatic structures with a wide distribution
information about pressure & pain, touch, and temperature
located in the dorsal root
36
What information do general somatic afferent IA neurons convey? where do they originate?
general somatic afferent IA neurons relay info to:
- protective & local reflexes
- forebrain (so information can be precieved as sensation - pressure, pain, hot, cold)
they originate in the dorsal horn
37
What do special visceral afferents innervate? what information do they convey? where are they located?
they innervate specialized gut related receptors such as taste buds and olfactory mucosa
special visceral afferents convey information about the gut
they are located in the dorsal root ganglion
38
what information do special visceral IA columns convey? where do they originate?
information from gut to:
- reflex circuits to produce salvation, chewing, and swallowing
- forebrain for perception (taste and smell)
they originate in the dorsal horn
39
What do general visceral afferents innervate? what information do they convey?
GVA innervate visceral structures of the GI & GU systems, heart, and great vessels
convey information about fullness and discomfort
40
What do GVA-IA neurons innervate?
GVA-IA relay info to:
- vital reflex circuits
- forebrain: for experience of bladder pressure and stomach fullness
41
What do OA do? what system do them work in?
relay information to LMN
| they work in the ventral horn
42
what are GVE (preganglionic neurons)? where do they work? are they sensory or motor?
they are output neurons of the ANS (SNS and PSNS)
they work in the ventral horn cell column
they are motor neurons
43
what do SVE (or pharyngeal efferents) innervate? are they motor or sensory?
they innervate the muscles of mastification, facial expression, pharynx, and larynx. As well as the mm for moving the head.
they are motor neurons
44
what do the GSE supply?
they supply motor output to skeletal muscle
45
what is the final common pathway refer to?
LMN
46
Trace the course of a UMN.
motor cortex
crosses in medulla in pyramid
ends in grey matter of ventral horn cell column at level it will work upon
47
how many cell columns are in the dorsal horn cell column? in the ventral cell column?
4 in dorsal
| 3 in ventral
48
what type of matter makes up longitudinal tracts? what are the three layers that make them up?
```
white matter
layers:
inner - archilayer
middle - paleolayer
outer - neolayer
```
49
describe the significance of the archilayer of the longitudinal tracts.
- embryonic neurons migrate to this layer to form the reticular formation
- contains circuits for reflexes
- as it enters brainstem it gets bigger and contains VITAL reflexes (respiration, cardiovascular fxn, swallowing, vomiting)
- reticular activating system is in the lateral portion of the reticular formation of the medulla, pons, midbrain
- sensory from all modalities enter here including somatosensory, auditory, visual, and visceral afferents
- made of short fibers
- maximum of 5 segments
- allows motor neurons to act together
50
what is the significance of the paleolayer of longitudinal tract?
contains most of the major fiber tracts required for sensation and motor function
larger diameter, longer fibers of the spinoreticular and spinothalamic tracts
functional at birth
*Facilitates primitive functions
51
what is the significance of the neolayer of longitudinal tracts?
necessary for delicate, highly coordinated skills like manipulative finger and toe movements
functional at 2 years of age
babies lack a developed paleolayer which is why they can't do anything)
52
what layers of the longitudinal tracts have collateral communication pathways between grey matter? what is the significance of this?
the inner and middle layers
provides alternative route to bypass damage
the outer layer lacks this so if it is damage there is loss of function
53
A patient with a stroke has lost the ability to make fine motor hand movements. What layer of the longitudinal tract was most likely damaged? Which is intact?
the neolayer was damaged so they lost distal hand function
but the paleolayer is intact which preserves basic life functions
54
Name the two pyramidal tracts. Are these ascending or descending tracts? Where do they cross? Which is the bigger tract?
- lateral corticospinal tract (bigger): crosses in pyramid
- anterior corticospinal tract: crosses at spinal cord level
they are descending tracts
55
what information do spinothalamic tracts convey? where do they terminate?
conscious pain, temperature, CRUDE touch, and pressure
there is a lateral and anterior tract
they terminate in area of cerebral cortex which perceives these sensations
56
what does the cerebral cortex do, where is it?
outer layer of cerebrum
made of folded grey matter
important for consciousness
57
where do extrapyramidal tracts control impulses? are they voluntary?
at segmental level
| they are not voluntary
58
where does the spinal cord span to and from?
foramen magnum at base of skull to L1 or L2
59
what is the cauda equina?
when the dorsal and ventral roots of the caudal portion of spinal cord angle downward
60
what replaces cell columns in the brain stem?
nuclei
61
Functions of medulla?
autonomic center for breathing, BP, and reflexes of swallowing, coughing, and vomiting
62
function of pons?
attached to cerebellum
aids in balance and breathing
63
function of midbrain
eye movement
| contains relay nuclei of auditory and visual systems
64
what is the major relay center for information going to and from the cerebral cortex?
the thalamus (somatic)
65
what are the dorsal horn and ventral horn parts of the diencephalon?
dorsal horn - thalamus & subthalamus
ventral horn - hypothalamus
66
Where information is processed by the thalamus?
Sensory information going TO the cerebral cortex
Motor information coming FROM the cerebral cortex going TO the brainstem & spinal cord
Information of the RAS
67
What system does the sub thalamus contain?
movement control systems related to the basal ganglia
68
what is the function of the hypothalamus?
Autonomic
integration of homeostatic control of bodies internal environment (blood gas, water balance, good consumption, endocrine, ANS)
69
what is the internal capsule?
broad band on fibers between thalamus and basal ganglia
contains fibers that connects cerebral cortex to deeper structures (basal ganglia, thalamus, midbrain, pons, medulla, spinal cord)
70
Describe the corpus collosum, gyrus, and sulci of the teleencephalon.
corpus collosum: axons connecting cortexes of two lobes (cerebral hemispheres)
gyrus: ridges
sulcus: valley between two ridges
71
what happens when broca's area and wernicke's area damaged?
damaged broker's area = speech production impairment
damaged wrenicke's area = speech/written language comprehension impairment
72
what two body parts make up the majority of the motor and sensory cortexes?
hands
head (mouth)
73
What is the progression from superior to inferior of the body related to the sensory and motor cortexes?
superior
- feet
- trunk
- hand
- neck
- eyes
- face
- lip
- jaw
- tounge
74
Number of cervical, thoracic, lumbar, sacral, and coccygeal spinal nerves??
```
cervical - 8
thoracic - 12
lumbar - 5
sacral - 5
coccygeal - 2+
```
75
Cervical nerves 1-7 pass __1__ their corresponding vertebra. Cervical nerve 8 passes above __2___ vertebra. Thoracic nerves 1-12 pass __3___ their corresponding vertebra.
1. above their vertebra
3. above T1
3. below their vertebra
76
After the ventral and dorsal root of nerves merge they divide into: __ and ___
dorsal primary rami
| ventral primary rami
77
dorsal primary rami contain what type of fibers?
sensory fibers and motor fibers to the back
78
ventral primary rami contain what type of fibers?
motor and sensory fibers to the anterior trunk and extremeties
79
what are the meninges? what three layers compose them?
protective membranes surrounding the brain and spinal cord
1. pia mater
2. arachnoid mater
3. dura mater
80
describe the pia mater
adheres to brain, contains blood supply, and allows no liquid penetration
81
describe arachnoid mater
web-like trabeculations filled with CSF, helps with shock absorption, allows no liquid penetration
82
describe dura mater
2 membranes (acts as one)
one attached to bone
tough
forms dural venous sinuses for veins to pass through (superior and inferior sagittal sinus, cavernous sinus, transverse sinus)
83
what does the subarachnoid space lie between? what does it contain? is it real or potential?
pia mater and arachnoid space
contains CSF & weblike trabeculations
real space
84
Is the sub-dural space real or potential? When a bleed occurs it is usually ____ pressure from the ____ system.
potential
When a bleed occurs it is usually low pressure from the venous system.
85
What does the epi-dural space lie between? Is the epi-dural space real or potential? When a bleed occurs it is usually ____ pressure from the ____ system.
lies between bone and dura mater
potential space
When a bleed occurs it is usually high pressure from the arterial system.
86
What freely passes through the brain barriers? What also can pass through the barrier? Of these which has the highest rate of diffusion across the barrier?
water, CO2, & O2
medications: lipid soluble drugs diffusing faster
87
CSF brain barrier is composed of ____ _____ epithelial cells. These cells facilitate ___.
choroid plexus
These cells facilitate waste removal
88
Does the Brain have lymphatic vessels?
No, it but it does have immune cells
89
List the arteries that make up the circle of willis
- 2 vertebral arteries
- 1 basal artery (splits to 2 posterior cerebral arteries)
- 2 internal carotid
- 2 middle cerebral arteries
- 2 anterior cerebral arteries
90
where does the venous drainage of the brain occur?
into the dural venous sinuses and into the internal jugular vein within the dura mater
91
What are the significances of the cavernous and transverse sinuses?
cavernous - close to nose can important infection from zit
transverse - close to ear can import infection from ear infection
92
What is the ventricular system, how many, names of them?
```
cavities filled with CSF
there are 4 ventricles:
- 2 lateral
- 3rd ventricle
- 4th ventricle
```
93
what is the choroid plexus? where do they arise?
specialized capillaries that produce CSF (125-150mL)
they arise in pia mater, in the lateral, 3rd, and forth ventricles
94
where is CSF reabsorbed?
through arachnoid villi located in the subarachnoid space in the sagittal sinus
95
ventricular drainage of CSF?
arachnoid villi to right and left ventricle to 3rd ventricle to 4th ventricle to subarachnoid space to cistern in spinal cord or superior sagittal sinus
96
Where are nociceptors and thermoreceptors located?
skin
thermoreceptors - temp
nociceptors - extremes of pain & temperature
97
Mechanoreceptors sense what 3 things? what types of receptors do they have and where are they located?
touch
audition
vestibular
98
photo receptors modality:
vision
99
chemoreceptors sense 4 things, list them, their receptors, and the location of their receptors.
1. olfaction
2. taste
3. PaO2
4. pH of CSF
100
Describe the sensation encoded by the following mechanoreceptors:
1. pacinian corpuscle
2. meissner's corpuscle
3. Hair follicles
4. ruffini corpuscle
5. merkel's receptors
1. pacinian corpuscle: vibrations
2. meissner's corpuscle: 2 point discrimination
3. Hair follicles: velocity and direction of movement
4. ruffini corpuscle*: stretch and joint rotation
5. merkel's receptors: vertical indentation of skin
101
where does input for proprioceptive information come from?
muscles, tendons, joints, & stretch fibers in skin
102
what type of fibers make up thermal, mechanical, and polymodal NOCICEPTOR receptors?
sensory and motor
thermal and mechanical - myelinated A delta fibers (they are fast; example: fast pain, touch, pressure, temp)
polymodal - unmyelinated C fibers (ex. slow pain, postganglionic autonomic nerves, olfaction)
as you go down alphabet and roman numerals nerve fibers get slower and smaller
1-a= motorneuron = largest and fastest
103
what makes up a sensory unit?
receptor, ganglion, and axon
104
describe the 1st, 2nd, 3rd neuron sensory system arrangement?
at what levels are many interneurons located?
first order neurons: periphery to CNS (dorsal horn)
second order neurons: reflex networks and to the thalamus (up a tract)
third order neurons: thalamus to cortex
many interneurons process and modify information at level of the 2nd & 3rd order neurons
105
Where do spinothalamic nerves cross the spinal cord?
when they enter the spine (crosses dorsal horn grey matter)
106
what sensory units are required for the limb and trunk? what sensory units are required for the face and cranial structures?
Dorsal Root Ganglion is required for the limbs and trunk.
Trigeminal sensory neurons are required for the face and cranial structures
107
where do the cranial nerves send their axons to?
nuclei in the brainstem
108
another term for dorsal column
medial lemniscal pathway
109
what information does the dorsal column transmit?
RAPID transmission of:
discriminative touch
proprioception
vibration
110
describe the pathway of the dorsal column (3 neurons)
1. receptor through dorsal root ganglion to dorsal horn of spinal cord
2. transmitted to dorsal column
information travels up dorsal column of white matter to the input association neurons in the medulla (called the medial lemniscus)
In the medulla the axons cross at the medial lemniscus and travel to the thalamus
3. The fibers than go to the primary sensory cortex
111
What pathway are you stimulating when you use a tuning fork to assess sensation of a boney joint?
Dorsal column - medial lemniscus pathway or discriminative pathway
112
What pathways is required for stereognosis (identifying objects without looking at them)?
afferents to dorsal horn to dorsal column - medial lemniscus pathway
proprioception information travels up the dorsal column (white matter) to the medulla (where it crosses), passes to the thalamus (integrates sensory and motor information), and final message sent to the primary somatosensory cortex
113
What two things must a patient have for stereognosis to occur?
higher order parietal association cortex must function
prior learning of object
114
what is astereognosis?
When the patient cannot associate the shape of the object with the name of the object
Occurs when dorsal column pathway is intact but when the parietal association cortex is broken
115
What is another name for the lateral spinothalamic and anterior spinothalamic pathways?
neospinothalamic - lateral
paleospinothalamic - anterior
116
what information does the lateral spinothalamic tract convey? rapid or slow?
bright, sharp pain through 3 AXON pathway
relatively rapid transmission
117
what information does the anterior spinothalamic pathway convey? rapid or slow?
transmission of information that is general (doesn't require discrete localization or intensity) SLOW transmission
slow pain, temp, crude touch, pressure
it is older
118
what does the RAS/reticular formation control
startle reflex, wakefulness, BP, and HR (ANS)
119
where does the anterior spinothalamic pathway convey fibers to?
RAS in brainstem
intralaminar nuclei of thalamus which connects to LIMBIC system providing touch with the affective/emotional aspects
120
describe the functions of 1st, 2nd, and 3rd order neurons in the somatosensory system
1st: transmit info from periphery to CNS (through dorsal root ganglion neuron or trigeminal sensory neurons)
2nd: transmit infö from CNS to thalamus (and/or initiate reflexes at spinal cord level)
3rd: transmit info from thalamus to cerebral cortex
121
what is the pathway of the anterolateral pathway
receptor to dorsal root ganglion to dorsal horn
crosses at anterior commissure at segment level to the anterolateral tracts
lateral goes to thalamus and than to cortex
anterior gives fibers to RAS than goes to thalamus (gives fibers to limbic system for emotion), and than to cortex
122
what 4 things does perception involve?
awareness of stimuli
localization
discrimination of characteristics
interpretation of their meaning
123
where does interpretation occur?
thalamus - here it enters the consciousness and is interpreted into rough localization and crude sense
somatosensory cortex - full interpretation
124
where is the primary somatosensory cortex located?
parietal lobe
125
where is the somatosensory association cortex and what is it function?
behind primary somatosensory cortex and transforms raw material into experience by integrating information with past experiences
126
where is the ANS located? what is its function?
CNS and PNS
| coordinated and maintains a steady stage amount viscera
127
In the ANS, which is myelinated and which is unmylinated: preganglionic neuron and post ganglionic neurons
preganglionic - myelinated
| post ganglionic - unmyelinated
128
where does the SNS receive input from?
T1-L2
| thoracolumbar division
129
The sympathetic chain ganglia is ____vertebral; while the sympathetic ganglia is ___vertebral.
The sympathetic chain ganglia is paravertebral; while the sympathetic ganglia is prevertebral.
130
where does the PNS receive information from?
cranial nerve nuclei and sacral region of spinal cord
| craniosacral division
131
where do preganglionic neurons travel to in the PNS?
ganglia close to the organs they innervated
132
the descending motor tract involves what parts of the brain?
brain stem, cerebellum, basal ganglia, and motor cortex
133
where is the motor cortex located?
posterior aspect of frontal lobe
134
name the 3 parts of the motor cortex
primary motor (aka motor strip)
premotor
supplementary motor cortex
135
where does the motor cortex collect information from
```
thalamus
sensory cortex
cerebellum
basal ganglia
premotor cortex
```
136
the motor cortex is divided by the "motor homunculus" what parts receive the most innervation? what is the role of the motor cortex?
hands, face (for speech)
the motor cortex controls specific muscle movements
137
What type of movements are generated by the premotor cortex?
patterned movements (done by prefrontal association cortex)
this lies anterior to the motor cortex
138
what type of movements does the supplementary motor cortex control?
complex, skillful movements that involves both sides of the body
139
Name a few places the output neurons of the primary motor cortex project to.
- Premotor and somatosensory areas on the same side
- Opposite side of the cortex
- Descend to subcortical structures such as the basal ganglia and thalamus
- Brain stem and spinal cord
140
Describe the tract of the UMN (the pyramidal system).
bet cells in the primary motor cortex to internal capsule through pons and medulla to pyramids to segmental level of spinal cord LMN
(may also travel down corticobulbar tract instead of corticospinal)
141
where to 80% of UMN cross? what is the name of this tract?
at the junction between the medulla and spinal cord (at the pyramidal system)
this is called the lateral corticospinal tract
142
what corticospinal tract does not cross in the medulla? what vertebral level does it most commonly innervated?
anterior corticospinal tract
the cervical level
143
where do cells in the extrapyramidal system originate? how do they differ from the pyramidal system?
premotor cortex
supplementary cortex
basal ganglia
they don't follow the same route (don't go thru pyramids)
their axons are project to the reticular formation (in the brainstem) and the reticulospinal system (to ancient LMN)
144
how are pyramidal disorders characterized?
spasticity and paralysis
145
how are extrapyramidal disorders characterized?
involuntary movements, ridigity, immobility without paralysis
146
1. what is the reflex called that involves structures in the brain?
2. what is the reflex called that involves multiple segments?
2. what is the reflex called that involves one cord segment?
1. suprasegmental
2. intersegmental
3. segmental
147
what reflex is important for muscle tone and posture? when should you test it?
stretch reflex
test when person has problems with mm tone or posture
148
what are the two type of stretch receptors? what information do they transmit? for what purpose?
muscle spindle receptors - they transmit information about muscle LENGTH and RATE of stretch (contracts mm, maintains muscle tone)
golgi tendon receptors - transmits info about muscle TENSION or FORCE of contraction (relaxes mm before you rip it)
149
what type of neurons does the muscles spindle work with?
Ia nerve fibers (they are intrafusal fibers - specialized sensory organs for detecting length and rate of stretch)
150
describe the pathway of the stretch reflex
muscle spindle detects stretch (mechanoreceptor): sends info on Ia neuron to spinal cord, synapses with motor neuron, tells mm to contract
also sends info on mm length to brain (synapses with internuncial neurons), sends this info via dorsal column (to brain stem, cerebellum, and cortex), to send inhibitory stimulus to motor units of antagonistic mm group
151
what is reciprocal innervation?
sensory input tells one neuron to contract one muscle and another neuron to relax a different neuron (antagonistic muscle)
152
what type of receptors are muscle spindles 1a neurons?
mechanoreceptors with special somatic afferents
153
where are muscle spindles located?
in muscle belly
154
What do descending fiber of the motor pathway SYNAPSE with and ACTIVATE? (2 things)... Why?
alpha motor neurons
gamma motor neurons
so that the sensitivity of the muscle spindles is coordinated with the muscle movement
155
can we control our stretch reflex?
yes, central control over motor neurons allows us to suppress it, otherwise any movement we made would be opposed and prevented by tone maintenance
156
golgi tendon reflex
stretch receptors in the tendons
Sense when a muscle contracts (not stretches)
Group Ib afferent neurons are excited
Synapse on inhibitory interneurons in spinal cord
Inhibitory neurons synapse on alpha motor neurons
they inhibit firing of the motor neuron which relaxes the same muscle that was just contracted
Also cause synergistic muscles to relax and antagonistic muscles to contract
Exact opposite of stretch reflex
157
flexor withdrawal reflex
Flexor reflex afferent fibers are activated
Synapse on multiple interneurons
Ipsilateral side reflexes are activated that cause flexor response
Contralateral side gets crossed-extension reflex which extends to maintain balance
Afterdischarge makes the flexion stay a while
158
function of basal ganglia
Function is to influence the motor cortex via pathways through the thalamus
plan/execute SMOOTH movements
also affective/cognitive function
159
There are two pathways from basal ganglia to motor cortex. which is inhibitory and which is excitatory?
inhibitory - indirect
| excitatory - direct
160
Parkinsons is caused by damage to which of the two BG/motor cortex pathways? Sx?
Both inhibitory and excitatory
| Tremors, shuffling gait, slow movements
161
Huntington's is caused by damage to which of the two BG/motor cortex pathways? Sx?
inhibitory
| chorea
162
function of cerebellum? what happens with damage?
Regulates movement and posture
Helps to control rate, range, force and direction of movement
damage = lack of coordination (loss of inhibitory feedback) = ataxia (errors in rate, range, force, and direction of movement)
163
three divisions of cerebellum?
vestibulocerebellar - balance and eye movements
spinocerebellar - syngerny of movements
pontocerebellar - plan and initiate movments
164
examples of cerebellar damage
ataxia
uncoordinated movements
dysdiadochokinesia
intention tremors
165
vestibular system function
equalibrium and balance
detects angular and linear acceleration of head
creates stable vision image
adjusts posture to maintain balance
166
semicircular canals angular or linear?
angular
167
utricle and saccule angular or linear
linear
168
how do semicircular canals work? same for otoliths
When the head is rotated the endolymph in the canals is “sloshed”, this moves the cupula over the hair cells, which depolarizes the hair cells. The hair cells will either excite or inhibit the afferent vestibular nerves.
Rotation of the head to the left stimulates the left semicircular canals and rotation to the right stimulates the right semicircular canals.
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where do afferents from the vestibular hair cells terminate
Superior, Medial, Lateral, Inferior nuclei in medulla
semicircular canals help with VOR (eye movements)
utricles help with posture
