Session 4 - Pyramidal Tracts Flashcards Preview

Semester 5 - CNS > Session 4 - Pyramidal Tracts > Flashcards

Flashcards in Session 4 - Pyramidal Tracts Deck (23):
1

What are the two main classes of descending tracts?

Pyramidal tracts
Extrapyramidal tracts

2

What do pyramidal tracts do?

Maintain somatic control of muscle by making direct (monosynaptic) contact with LMN supplying distal muscle of extremities

3

What are the two mains part of the pyramidal tract?

Corticospinal
Corticotubular

4

What are the two different part of the corticospinal tract?

Lateral and anterior

5

Outline the path of the corticospinal tract

 Skeletal Muscle α-LMN
 Lateral decussates in Medullary Pyramids
 Anterior remains ipsilateral

6

Where does the corticotubular pyramid extend to?

 Cranial Nerve Nuclei

7

What are extrapyramidal tracts?

Indirect contact (polysynaptic) with motor neurones, via regulation of ventral horn interneurons.

8

What is the difference in relationships with LMN's between pyramidal and extra-pyramidal systems

Pyramidal system has direct (monosynaptic) contact with lower motor neurones supplying the distal muscles of extremities (e.g. the hand)

The extra-pyramidal system has an indirect contact with the rest of the motor neurone pool.

9

Give three causes of upper motor neurone lesions

 Stroke
 Spinal cord injury
 Motor neurone disease

10

Give three causes of LMN lesions

 Trauma
 Peripheral neuropathy
 Motor neurone disease

11

Give key signs of UMN lesions

 Hypertonia
 Hyerreflexia
 Clonus
 +’ve Babinski sign
 No fasiculations
 Clasp-knife reflex
 No muscle wasting
 Muscle weakness

12

Give key signs of LMN lesions

 Hypotonia
 Hyporeflexia
 Fasciculations
 Muscle wasting
 Muscle weakness

13

Where does hypertonia, hyperreflexia and spastic paralysis come from in a UMN lesion?

Loss of descending inhibition of spinal reflexes

14

What is clasp knife reflex?

 Increased tone gives resistance to movement, but when sufficient force is applied resistance suddenly decreases

15

What is clonus caused by?

 Loss of descending inhibition leads to self re-excitation of hyperactive reflexes

16

What is a positive Babinski sign?

 Scrape along lateral edge of foot and in towards great toe
 Dorsiflexion of hallux, extension/flaring of toes (Loss of descending inhibition means the reflex is unable to be suppressed)

17

What is hypotonia caused by in LMN lesions?

 Lack of LMN means muscle cannot contract to produce tone

18

Name the extra-pyramidal tracts

Tectospinal tract
Vestibulospinal tract
Reticulospinal tract
Rubrospinal and rubrobulbar tract

19

Where does the tectospinal tract arise and what does it do?

– Main inputs are from the superior and inferior colliculi in the midbrain; decussate in the midbrain
– Innervate Motor neurone pools of neck – coordinate eye-head movements, responses to visual & auditory stimuli

20

Where does vestibulospinal tract arise and what does it do?

– Originates from vestibular nuclei in the Pons; remain ipsilateral;
– Innervates motor-neurone pools of anti-gravity muscles - balance reflexes.

21

Where does reticulospinal tract arise and what does it do

– Widespread inputs, including from motor cortex, medulla oblongata, pons and midbrain
- remain ipsilateral
– Medullary (lateral tract) - Flexor reflex facilitation
- Extensor reflex inhibition
– Pontine (medial tract) - Extensor reflex facilitation
– Role in regulation of posture and rhythmic movements

22

Where does rubrospinal tract arise and what does it do?

– Originates from red nucleus (tegmentum of the mid-brain at superior colliculus), inputs include motor cortex
- Decussates at level of nucleus
– Control flexor tone in distal muscles, also tone of facial muscles

23

Where do corticospinal tracts arise from?

1/3 motor cortex
1/3 secondary motor cortex
1/3 parietal lobe

(2/3 precentral gyrus, 1/3 post-central gyrus)