descending pathways Flashcards
1
Q
function
A
- modify all the activity of ascending stimuli
- control conscious and reflex response to stimuli
2
Q
modes of control
A
- internal control
- external control
3
Q
external control
A
- sensory guided
- parietal cortex, premotor cortex, cerebellum
4
Q
internal control
A
- non-sensory guided
- prefrontal cortex, supplementary motor area, basal ganglia
5
Q
key features of the primary motor cortex
A
- inverse
- disproportionate
- contralateral
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
7
Q
commissural fibers
A
axons of neurons that join two cerebral hemispheres
8
Q
association fibers
A
axons of neurons that unite different parts of the same cerebral hemispheres
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
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
11
Q
spinal reflex arc examples
A
- patellar reflex
- abdominal skin reflex
- plantar reflex
12
Q
plantar reflex
A
big toe curls with stimuli
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
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
15
Q
pyramidal tract examples
A
- lateral corticospinal tract
- anterior corticospinal tract
16
Q
extrapyramidal tract examples
A
- rubrospinal tract
- reticulospinal tract
- olivospinal tract
- vestibulospinal tract
17
Q
pyramidal tracts are either …
A
corticospinal or corticobulbar tracts
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)
19
Q
pyramidal tract input
A
- supplementary motor area
- premotor cortex fibers
- parietal lobe
- cingulate gyrus
20
Q
where do corticospinal tracts originate
A
- layer 5 of cortex
- internal pyramidal layer contains large pyramidal neurons
21
Q
corticospinal tract input
A
- from motor and pre-motor cortical areas
- somatosensory cortex
- parietal lobe
- cingulate gyrus
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
lateral corticospinal tracts
- controls appendicular muscles for fine movement of ipsilateral limbs
- fibers decussate in the pyramids
26
corticobulbar tract other name
corticonuclear tract
27
corticobulbar tract
- initially follows the same pathway as corticospinal tracts
- synapse with the motor nuclei of the CN beginning at upper pons
- some fibers decussate
28
corticobulbar tract function
- responsible for voluntary movement of the face muscles (CNVII) and head/neck (CNXI)
- involved in phonation, swallowing, facial expression (CNVII and IX)
29
pyramidal disorders
- upper motor neuron lesion (UMN)
- lower motor neuron lesion (LMN)
30
upper motor neuron lesion (UMN)
- 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
lower motor neuron lesion (LMN)
- causes flaccid paralysis (muscles are limp, lack firmness)
- hypotonia
- loss of reflexes
- muscle atrophy
32
example of lmn lesion
bulbar lesion of the facial nerve
33
bulbar lesions
- 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
bulbar palsy
- 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
lou gehrig's disease (ALS)
- 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
extrapyramidal tract function
- 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
structures involved in extrapyramidal tracts
- basal ganglia
- red nucleus
- substantial nigra
- reticular formation
- cerebellum
38
how many extrapyramidal tracts are there
- vestibulospinal
- reticulospinal
- rubrospinal
- tectospinal
39
vestibulospinal tract
- arises from vestinular nuclei
- conveys balance information to spinal cord
- ipsilateral
40
reticulospinal tract
- arises in the reticular formation of the pons
- medial fibers (excites voluntary movements)
- lateral fibers (inhibits voluntary movements)
41
rubrospinal tract
- arises from the red nuclei
- contralateral
- plays a role in fine control of the hand
42
tectospinal tract
- arises in the superior colliculi
- receives input from optic nerves
- coordinates head movements in relation to visual stimuli
43
extrapyramidal syndrome
collections of symptoms that usually occur after long-term use of psychiatric medication
44
extrapyramidal syndrome examples
- akathisia
- dystonia
- parkinsonism
- tardive dyskinesia
45
akathisia
motor restlessness
46
dystonia
involuntary muscle contraction (eyes, tongue, neck, limbs)
47
parkinsonism
parkinson-like signs (tremor, rigidity, bradykinesia)
48
bradykinesia
slowness of movement and speed (or progressive hesitations/halts) as movements are continued
49
tardive dyskinesia
- repetitive, involuntary movements
- chewing, tongue protrusion, lip puckering
50
extrapyramidal disease
impairments of the central nervous system
51
extrapyramidal disease examples
- parkinson's disease
- huntington's chorea
- tourette syndrome
52
parkinson's disease
a brain disorder that causes unintended or uncontrollable movements, such as shaking, stiffness, and difficulty with balance and coordination
53
huntington's chorea
- 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
tourette syndrome
- neurodevelopmental disorder
- characterized by involuntary movements and sounds (tics)
