descending pathways

Question 1

motor system evolution

Answer 1

-as animals evolved with more complex nerous systems and motor capabilities more pathways evolved

Question 2

steps of motor system evolution

Answer 2

• reticular formation
• vestibular system
• development of tectum
• development of red nucleus
• development of cerebral cortex to control the above systems
• then the devlopment of the pyramidal tract

Question 3

how are the descending pathway neurons of the limbs organized in the ventral horn
- example

Answer 3

• somatotopic organization
• more medial you are in the spinal cord the more medial the muscles are

Question 4

what are the 2 groups of descending pathways

Answer 4

lateral ( lateral cortico spinal tract) and medial pathways ( vestibulo spinal tract, reticulospinal, tectospinal)

Question 5

why are the lateral cortico spinal tract lateral?

Answer 5

◼ Control of distal musculature
- such as hands and fingers

Question 6

why are vestibulo spinal , reticulospinal, and tectospinal tracts medial

Answer 6

◼ Control of axial and proximal
musculature
- such as balance and equilibrium

Question 7

what cells are located in the cortex

Answer 7

Giant pyramidal cells
- (betz cells)

Question 8

when does the motor cortex fire

Answer 8

Fires impulses prior to muscle
movement

Question 9

how is the motor cortex organized to produce

Answer 9

◼ Organized to produce simple
movements of individual body parts

Question 10

what does the motor cortex determine

Answer 10

Determines direction, amplitude,
speed, and force of movement

Question 11

the motor cortex is not organized to control ______ muscles

Answer 11

individual

Question 12

what is the somatotopic organization of of the primary motor cortex

Answer 12

More area given to parts of body that perform
more precise and delicate movements as compared
to those that perform less precise movements.

Question 13

what is the efferent patheay

Answer 13

pathway:
-axons travel through white matter  internal capsule
 cruscerebri/cerebral peduncle
 pyramidal fibers pierce the pons  pyramids of medulla
 lateral
corticospinal tract

Question 14

where is the the crus ceribri and sunstantia ( cerbral peduncle )

Answer 14

Question 15

where are the pyranidal fibers in the pons ( cortical spinal tract)

Answer 15

Question 16

what does the premotor cortex produce movements in response to
- what types of movements does it direct?

Answer 16

• visual and other stimuli
• Directs reaching and grasping
  movements

Question 17

what is the supplementary motor cortex concerned with

Answer 17

Concerned with movement that is
self- generated

Question 18

what is included in the motor asscocaiation cortex

Answer 18

• premotor cortex
• supplementary motor cortex

Question 19

photo of premotor and primary motor cortex

Answer 19

Question 20

what is the corticobulbart tract pathway

Answer 20

◼ Cell bodies in motor cortex (lateral
convexity)
◼ Fibers leave through internal capsule
◼ Exit in midbrain, pons and medulla
◼ Innervate cranial nerve motor nuclei
◼ Crossed and uncrossed fibers

Question 21

what nuclei are innervated by the corticobulbar tract

Answer 21

Trigeminal motor nucleus
Nucleus ambiguus
Facial motor nucleus (upper face)
Facial motor nucleus (lower face)
Hypoglossal nucleus

Question 22

what are the functions of:
Trigeminal motor nucleus
Nucleus ambiguus
Facial motor nucleus (upper face)
Facial motor nucleus (lower face)
Hypoglossal nucleus
responsible for

Answer 22

trigeminal: muscles of mastication
- Ambiguus: pharynx and larynx muscles
- 2 subnuclei for facial nucleus upper face and lower face
- Hypoglossal: tongue muscles

Question 23

what is the organization of the fibers of the corticobulbar tract
- how is this different than corticospinal

Answer 23

• crossed and uncrossed fibers
• completely crossed - cortico spinal

Question 24

how are the nerves of the lower face and tongue organized
- ex
- what does this resemble

Answer 24

• theyre completely crossed
• so left buccinators are controlled by the right motor cortex
  -similar to corticospinal r=tract

Question 25

what is bells palsy produced by

Answer 25

- lesion to the facial nerve and facial nucleus

Question 26

what does a lession to the left facial nerve cause

Answer 26

- paralysis to the left half of the face including the eye, mouth, and forehead

Question 27

what happens when you get a lesion to the cortex before it gets to the motor nucleus of 7 on the right side

Answer 27

- the axons will degenerate and pt loses control of the lower part of the face of the left side

Question 28

what does it mean a pt has paralysis to the lower half of the face vs the whole half

Answer 28

- lower half = stroke ( central weakness/lesion) - whole half = bells palsey (peripheral weaknes/lesion)

Question 29

how many neurons in the upper face vs lower face - what happens if there is a stroke in the right side

Answer 29

- upper face has 2 neurons ( one goes right the other goes left) - lower face has 1 - lower left face droops but upper doesnt since the left neuron is still functional

Question 30

what are the 2 categories of pahthophysiology of the motor cortex

Answer 30

epilepsy lesions

Question 31

jacksonian march

Answer 31

- observed epileptic seisures and observed the pattern of spread of the convulsion - he came up with a somatatopic map of the motor cortex - he observed the convulsion would spread to different body parts ( this is the jacksonian march)

Question 32

what occurs in LMN lesions

Answer 32

Severee muscle atrophy fasciculation ( rippling) hyporeflexia decreased/ flacid muscle tone

Question 33

what occurs in UMN lesions

Answer 33

- slight muscle atrophy - no fasciculation - hyperreflexia - increased/spastic muscle tone

Question 34

why should their be spasticity in the UMN lesion

Answer 34

cerebral cortec acts on the reticuloformation in a inhibatory way. - if inputs of the cerebral cortex are removed the reticuloformation is no longer inhibited causing spasticity

Question 35

spastic hemiplegia

Answer 35

- paralysis of the lower half of the face - arm has excess tone ( flexion in the elbow,) - excess tone in the lower limb as well

Question 36

babinski response - what is normal and abnormal

Answer 36

- response that appears with a person with a stroke - if you stroke the the sole of the foot you get flaring of the foot ( midly interitating stimulus that induces withdrwal response) - normal would cause toes to curl

Question 37

how does the babinski respose affect babies? what does this mean? what occurs if you have stroke

Answer 37

- babies flare toes when you touch the foot but get surpessed as you begin to walk and become an adult. however if you have a stroke this resposne will reappear