Weeks 16-18 Flashcards
(35 cards)
What is the difference between an open loop and a closed loop?
Closed takes into account the disturbance of error.
Final effective pathway
Brain –> spinal cord –> muscle
Final effector pathway for eye movement
Basal ganglia –GABA-> sup. colliculus –Glutamate-> Reticular formation –Glutamate-> Motor neurones –Ach-> Muscles
Final effector pathway for limb movement
Basal ganglia –GABA-> Thalamus –Glutamate-> 1st motor cortex –Glutamate-> Motor neurons –Ach-> Muscles
What makes up a motor unit?
Motorneurone + innervated muscle fibre
The muscle spindle
Spindle is responsible for sensory feedback.
Lies parallel to muscle fibers and detects changes in muscle length.
Enables regulation of muscle contraction and matches force to the task.
Stretch sensitive unit between two contractile units
Stretch of tendons is proportional to
Tension exerted by the muscle.
Alpha motorneurones
Innervate extrafusal muscle fibres which generate muscle tension.
Gamma motorneurones
Innervate intrafusal muscle fibres (spindles). Don’t generate tension.
Makes contracted spindle fiber sensitive to stretch of muscle.
Which sensory afferents have a larger diameter and faster conduction?
Groups 1 and 2.
Group 2 are stretch only afferents.
E.g low threshold mechanoreceptors
Which sensory afferents have a smaller diameter and slower conduction?
Groups 3 and 4.
E.g nociceptors and thermoreceptors
What innervates the golgi tendon organ?
1b afferents.
What is the golgi tendon organ?
Mechanoreceptor activated by 1b afferents that detects change in muscle tension.
What does the primary afferent 1a do? What does 1b do?
1a senses stretch and rate of change in stretch.
1b signal force change in muscle
What muscle group does monosynaptic pathways innervate?
Flexors
What muscle group do poly/oligosynaptic pathways innervate?
Extensors
The 3 cortical pathways
1) Lateral corticospinal tract (skilled limb movements)
2) Ventral corticospinal tract (axial muscle control)
3) Corticobulbar tract (facial muscles)
The 4 brain stem motor pathways
1) Rubrospinal tract (originates in red nucleus, limb control)
2) Tectospinal tract (originates in sup. colliculus, hand-eye coordination during gaze)
3) Reticulospinal tract (automatic movements and posture)
4) Vestibulospinal tracts (posture and balance)
Describe the hierarchical motor organisation
Limbic system
Premotor/supplementary motor cortices
Primary motor cortex
Brain stem
Spinal cord
Motor cortex (contain upper motor neurons)
Located in precentral gyrus (frontal lobe). Broadmans area 4 and 6.
Voluntary movement.
Pyramidal cells in cortical layer V are upper motor neurons.
Axon descends into corticobulbar and corticospinal tracts to spinal cord.
Alzheimer’s pathology
Cortical atrophy - results in widened sulci and narrowed gyri.
Neuronal loss/shrinkage (cholinergic pathways especially)
Reduced glucose uptake in sufferers (shown in PET scan)
Current treatment for alzheimers
Acetylcholinesterase inhibitors.
Inc Ach –> slower progression
Multiple sclerosis
Causes: Degradation of myelinsheath due to failing oligodendrocytes.
Most common in women.
Parkinsons disease pathology
Diminished substantia nigra (containing dopamine cells)
