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anatomy lectures > descending pathways > Flashcards

descending pathways Flashcards

1
Q

function

A
  • modify all the activity of ascending stimuli
  • control conscious and reflex response to stimuli
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2
Q

modes of control

A
  • internal control
  • external control
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3
Q

external control

A
  • sensory guided
  • parietal cortex, premotor cortex, cerebellum
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4
Q

internal control

A
  • non-sensory guided
  • prefrontal cortex, supplementary motor area, basal ganglia
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5
Q

key features of the primary motor cortex

A
  • inverse
  • disproportionate
  • contralateral
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6
Q

motor projection fibers

A

neurons in the motor cortex that give rise to axons that travel through the corona radiate and internal capsule

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7
Q

commissural fibers

A

axons of neurons that join two cerebral hemispheres

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8
Q

association fibers

A

axons of neurons that unite different parts of the same cerebral hemispheres

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9
Q

first order neurons

A
  • upper motor neurons
  • cell body originates in the cerebral cortex or brainstem
  • does not transmit impulses directly to muscles
  • glutamatergic
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10
Q

second order neurons

A
  • lower motor neurons
  • cell body originates in the anterior grey column of the spinal cord, brainstem, or cranial nerve nuclei
  • transmit impulses directly to muscles
  • acetylcholine
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11
Q

spinal reflex arc examples

A
  • patellar reflex
  • abdominal skin reflex
  • plantar reflex
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12
Q

plantar reflex

A

big toe curls with stimuli

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13
Q

pyramidal tracts

A
  • pass through the medullary pyramids (some corticobulbar tracts may not)
  • synapse on cranial nerves or with neurons in the anterior horn of the spinal cord
  • voluntary movement
  • most fibers originate in motor cortex
  • most fibers cross to contralateral side
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14
Q

extrapyramidal tracts

A
  • do not pass through the medullary pyramids
  • coordination of movements, posture control and muscle tone
  • most fibers originate in the brainstem
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15
Q

pyramidal tract examples

A
  • lateral corticospinal tract
  • anterior corticospinal tract
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16
Q

extrapyramidal tract examples

A
  • rubrospinal tract
  • reticulospinal tract
  • olivospinal tract
  • vestibulospinal tract
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17
Q

pyramidal tracts are either …

A

corticospinal or corticobulbar tracts

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18
Q

where are most of the cell bodies of the pyramidal tracts located

A

on the precentral gyrus of the frontal lobe (primary motor cortex)

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19
Q

pyramidal tract input

A
  • supplementary motor area
  • premotor cortex fibers
  • parietal lobe
  • cingulate gyrus
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20
Q

where do corticospinal tracts originate

A
  • layer 5 of cortex
  • internal pyramidal layer contains large pyramidal neurons
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21
Q

corticospinal tract input

A
  • from motor and pre-motor cortical areas
  • somatosensory cortex
  • parietal lobe
  • cingulate gyrus
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22
Q

where do corticospinal tracts travel through

A
  • internal capsule to the cerebral peduncles
  • come to lie on ventral surface of the medulla (the pyramids)
23
Q

types of corticospinal tracts

A
  • anterior corticospinal tracts
  • lateral corticospinal tracts
24
Q

anterior coticospinal tracts

A
  • controls central axial and proximal muscles involved in postural control
  • fibers decussate in the spinal cord
25
Q

lateral corticospinal tracts

A
  • controls appendicular muscles for fine movement of ipsilateral limbs
  • fibers decussate in the pyramids
26
Q

corticobulbar tract other name

A

corticonuclear tract

27
Q

corticobulbar tract

A
  • initially follows the same pathway as corticospinal tracts
  • synapse with the motor nuclei of the CN beginning at upper pons
  • some fibers decussate
28
Q

corticobulbar tract function

A
  • responsible for voluntary movement of the face muscles (CNVII) and head/neck (CNXI)
  • involved in phonation, swallowing, facial expression (CNVII and IX)
29
Q

pyramidal disorders

A
  • upper motor neuron lesion (UMN)
  • lower motor neuron lesion (LMN)
30
Q

upper motor neuron lesion (UMN)

A
  • causes spastic paralysis (muscles tighten, stiffen, contract)
  • hypertonia
  • absence of UMN control, LMN exhibits hyperactivity
  • caused by neuritis, direct trauma, spinal cord accident, or tbi
31
Q

lower motor neuron lesion (LMN)

A
  • causes flaccid paralysis (muscles are limp, lack firmness)
  • hypotonia
  • loss of reflexes
  • muscle atrophy
32
Q

example of lmn lesion

A

bulbar lesion of the facial nerve

33
Q

bulbar lesions

A
  • injuries to the cranial nerve nuclei or axons of the glossopharyngeal, vagus, and/or hypoglossal nerve
  • caused by lesions to the lower motor neurons, brainstem stroke, tumor
34
Q

bulbar palsy

A
  • paralysis produced by bulbar lesions
  • nucleus of the glossopharyngeal or vagus nerve (pharyngeal muscle weakness and posterior 1/3 of the tongue)
  • nucleus of the hypoglossal nerve (progressive loss of speech and tongue muscle atrophy)
35
Q

lou gehrig’s disease (ALS)

A
  • pyramidal disorder
  • upper and lower motor neuron disease
  • muscle weakening, twitching
  • inability to move arms, legs, body
  • progressive deterioration
  • muscles in chest stop working, it becomes hard to breath alone
  • caused by genetic defect in 10% of cases, idiopathic
  • breathing or swallowing muscles usually affected first
  • does not affect senses
  • rarely affects bladder, bowel, or cognition
  • no cure
36
Q

extrapyramidal tract function

A
  • involuntary and automatic control of movement, posture, and muscle tone
  • more control over medial muscles than periphery (more gross motor movements than fine motor)
37
Q

structures involved in extrapyramidal tracts

A
  • basal ganglia
  • red nucleus
  • substantial nigra
  • reticular formation
  • cerebellum
38
Q

how many extrapyramidal tracts are there

A
  • vestibulospinal
  • reticulospinal
  • rubrospinal
  • tectospinal
39
Q

vestibulospinal tract

A
  • arises from vestinular nuclei
  • conveys balance information to spinal cord
  • ipsilateral
40
Q

reticulospinal tract

A
  • arises in the reticular formation of the pons
  • medial fibers (excites voluntary movements)
  • lateral fibers (inhibits voluntary movements)
41
Q

rubrospinal tract

A
  • arises from the red nuclei
  • contralateral
  • plays a role in fine control of the hand
42
Q

tectospinal tract

A
  • arises in the superior colliculi
  • receives input from optic nerves
  • coordinates head movements in relation to visual stimuli
43
Q

extrapyramidal syndrome

A

collections of symptoms that usually occur after long-term use of psychiatric medication

44
Q

extrapyramidal syndrome examples

A
  • akathisia
  • dystonia
  • parkinsonism
  • tardive dyskinesia
45
Q

akathisia

A

motor restlessness

46
Q

dystonia

A

involuntary muscle contraction (eyes, tongue, neck, limbs)

47
Q

parkinsonism

A

parkinson-like signs (tremor, rigidity, bradykinesia)

48
Q

bradykinesia

A

slowness of movement and speed (or progressive hesitations/halts) as movements are continued

49
Q

tardive dyskinesia

A
  • repetitive, involuntary movements
  • chewing, tongue protrusion, lip puckering
50
Q

extrapyramidal disease

A

impairments of the central nervous system

51
Q

extrapyramidal disease examples

A
  • parkinson’s disease
  • huntington’s chorea
  • tourette syndrome
52
Q

parkinson’s disease

A

a brain disorder that causes unintended or uncontrollable movements, such as shaking, stiffness, and difficulty with balance and coordination

53
Q

huntington’s chorea

A
  • movement disorders associated with Huntington’s disease
  • both involuntary movement problems and impairments in voluntary movements
  • involuntary jerking or writhing movements (chorea)
  • muscle problems (rigidity or muscle contracture)
  • slow or unusual eye movements
54
Q

tourette syndrome

A
  • neurodevelopmental disorder
  • characterized by involuntary movements and sounds (tics)

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