Sensory and motor pathways Flashcards
What is difference between anterior and lateral spinothalamic tracts of the ascending sensory pathway for Anterolateral system?
Anterior: Crude touch + pressure
Lateral: Pain and temp
Primary and secondary and third order neurons in anterolateral system?
Primary: Peripheral sensory receptors to dorsal horn.
Synapses with second order neurons in dorsal horn of spinal cord (also where crossing happens)
Third order is from thalamus to post-central somatosensory cortex.
Lesions effecting spinothalamic tract results in?
Loss of temp, pain, crude touch below lesion on the contralateral side (brown sequard syndrome because crossing has already occurred).
Which nucleus of the thalamus does each of the tracts of the anterolateral system reach?
Lateral: Central lateral nucleus
Anterior: Ventral posterior lateral nucleus
What are the two tracts of the dorsal column medial lemniscus system?
Gracile and cuneate fasciculus
What is gracile and cuneate fasciculus responsible for detecting?
Gracile: Touch
Cuneate: Proprioception
First, second, third order neurons for dorsal column and the overall tract for gracile and cuneate?
First order: Periphery to Medulla
Cunneate: T6 and above
Gracile: Below T6
Second: Gracile (medial) and cuneate (lateral) ascend ipsilaterally up dorsal column crosses at medulla.
Third: Synapses with third order neurons at either nucleus gracilis or cuneatus of medulla. THEN CROSSES and goes up contralaterally up medial lemniscal tract
Lesions in dorsal columns results in…
Loss of proprioception, touch, vibration to same side
What tracts makes up the descending pyramidal system of the motor pathway?
Lateral and anterior corticospinal
Pathways for both pyramid tracts?
LATERAL motor system
- 80%
- PMC –> Internal capsule (next to basal ganglia) –> medulla (the pyramids) –> cross to contralateral side –> descend in lateral corticospinal tract to lower motor neuron
- DISTAL muscle groups
ANTERIOR (or medial) motor system
- 20%
- Enter pyramids (DONT CROSS) –> descend ipsilateral side
- crosses when at final spinal cord level
- communicates with PROXIMAL muscle groups
(both are pyramidal and all cross to other side of body just at different spot)
Lateral motor system –> anterior horn for distal muscles
Medial motro system –> anterior horn for proximal muscles
Function of pyramidal and extrapyramidal systems?
Pyramidal: - Voluntary
Muscles originate from motor cortex
A direct pathway to influence lower motor neurons
Extrapyramidal:
Involuntary movement
Coordinate movement, control posture, and muscle tone
Indirect ways to influence lower motor neurons
4 tracts of extrapyramidal and its functions? Reticulo and Vestibulo do not cross!
- Rubrospinal tract
- From red nucleus of mid brain and project to spinal cord
- Travels in lateral funiculus (cervical)
- Upper limb control - Reticulospinal tract
- Pons and medulla reticular formation (large cell formation)
- Travel lateral funiculus in medulla and anterior funiculus in pons
- Coordinate automated movement and posture - Vestibulospinal tract:
- From vestibular nuclei
- Controls lower limn muscle tone (=posture and balance) - Tectospinal
- Midbrain Colliculi
- Anterior funiculus (cervical)
- Automated postural head movement
Corpus striatum is made up of
Globus pallidus, putamen, caudate nucleus
They are all cerebral nuclei
Midbrain nuclei consist of?
Substantia nigra and subthalamic nucleus
Where is basal ganglia anatomically?
Collection of grey matter located within white matter of cerebrum and includes several nuclei in diencephalon and brainstem
Substantia nigra
- Midbrain
- Motor planning and movement
- degenerates in parkinsons
Two components of substantia nigra?
- Pars compacta:
- dopaminergic neurons
- black from neuromelanin
- the part that degenerates
Pars reticulata:
- GABAergic neurons
- neurons less densely packed
What degernates in the basal ganglia to cause Parkinson’s disease
Globus pallidus and substantia nigra. dopamine reduce
Treatments of parkinsons?
L-Dopa
Destruction of globus pallidus via surgery
implant neurons containing dopamine
What does cerebellum do?
- fine movements
- coordination
- motor learning
- Compared motor plan with motor action to refine movement
- Inputs to motor thalamus
