spinal cord+descending tracts, motor cortex and cerebellum Flashcards
1
Q
where are alpha motor neurons located?
A
anterior horn of spinal cord, grey matter, and part of somatic motor system (voluntary movement)
2
Q
function of alpha motor neurons in spinal cord
A
- initiate muscle contractions
- release acetylcholine at junctions to activate muscle fibres
- contraction of skeletal muscle then alpha motor neurons are essential for voluntary movement
3
Q
what do alpha neurons form?
A
- make up motor units (alpha motor neuron and all muscle fibres it innervates)
- small motor units for finer movements and larger for more force
4
Q
cerebellums role
A
- modulate motor output and refines voluntary movement
- adjustor of motor control systems
5
Q
what ways does the cerebellum contribute to motor control
A
- coordination and precision
- error detection and correction
- motor learning
- posture and balance
- timing and rhythm
- feedforward control
6
Q
what makes up the 31 Paris of spinal nerves
A
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
7
Q
anatomy of the spinal nerves
A
- each nerve has a neural (motor) and dorsal sensory) root
- consists of grey and white matter
8
Q
what does grey matter consist of?
A
- H shaped structure
- anterior and posterior horns
- alpha motor neurons in anterior horn
9
Q
what does white matter consist of?
A
- myelinated nerve fibres and bundled into tracts carrying sensory info up and motor info down spinal cord
10
Q
name the 6 descending fibre systems to the spinal cord
A
- corticospinal tract
- rubrospinal tract
- reticulosppinal tract
- vestibulospinal tract
- tectospinal tract
- corticobulbar tract
11
Q
corticospinal tract
A
- origin: primary motor cortex
- function: voluntary, fine motor control of muscles
- largest descending tract
- direct and indirect connections to motor neurons
12
Q
rubrospinal tract
A
- origin: red nucleus, brainstem
- midbrains collection of cell bodies
- function: motor control and coordination
- highly vascularised- inputs from cerebellum and primary motor cortex
- activation of flexor motor neurons
13
Q
reticulospinal tract
A
- origin: reticular formation in brainstem
- function: muscle tone modulation, reflex activity and autonomic functions (involuntary)
14
Q
tectospinal tract
A
- coordinates head and eye movements in response to visual stimuli
- axons travel down spinal cord
15
Q
vestibulospinal tract
A
- origin: vestibular nuclei in brainstem
- function: regulates posture and balance
- contracts and relaxes muscles to maintain balance, posture and muscle head movements
- innervates neck and controls eye movements
- excitation of extensors and inhibition of flexors
16
Q
corticobulber tract
A
- controls facial muscles and head through connections with cranial motor nerve nuclei
17
Q
which tracts make up the lateral descending system?
A
- corticospinal tract
- rubrospinal tract
18
Q
which tracts make up the medial descending system?
A
- reticulospinal tract
- vestibulospinal tract
19
Q
pathway of the corticospinal tract
A
- 90% are lateral
- through internal capsule, cerebral pundicles and pyramids of the medulla oblongata before crossing onto contralateral side
- continue down spinal cord as lateral tract controls limbs and anterior tract controls axial muscles
20
Q
corticobulber tract pathway
A
- upper motor neurons project from cerebral cortex to brainstem via cerebral peduncles and innervates interneurons/cranial nerves
- interneurons innervate reticular formation
21
Q
rubrospinal tract pathway
A
- axons descend in the lateral funiculus of spinal cord
- fibres terminate on interneurons projecting to ventral horn
22
Q
reticulospinal tract pathway
A
- medial and lateral tracts
- medial = arises from pons and projects ipsilaterally to entire spinal cord. facilitates extensor spinal reflexes
- lateral = arises from medulla and projects bilaterally to spinal cord. surpasses extensor activity
23
Q
vestibulospinal tract pathway
A
- medial and lateral tracts
- medial = arises from ipsilateral and contralateral medial vestibular nuclei at non-medulla junction
- descends in ventral funiculus of cervical spinal cord and terminates in ipsilateral ventral horn
- lateral = arises from neurons of lateral vestibular nucleus at pons-medulla junction. descends entire length of spinal cordoned receives inhibitory pints from cerebellum
24
Q
describe the motor cortex
A
- region of the cerebral cortex
- planning, controlling and executing voluntary movements
25
Q
primary motor cortex (M1)
A
- location: precentral gyros of the frontal lobe
- execution of voluntary movements by sending signals to muscles on contralateral side of the body
- somatotopically organised
26
Q
premotor cortex
A
- location: anterior to primary motor cortex
- planning and coordinating movements- receives info from sensory areas to organise motor movements
27
Q
supplementary motor area (SMA)
A
- location: medial surface of hemisphere
- plan and execute complex movements
- coordinates bilateral movements and both sides of body
28
Q
how many neurons are there in the brain?
A
86 billion neurons in the brain
29
Q
explain the cerebellums rule of 3?
A
- 3 of everything
- 3 lobes (anterior, posterior, flocculonodular)
- 3 functional subdivisions
- 3 pairs of peduncles
- 3 pairs of deep nuclei
- 3 cortical layers
30
Q
the cerebellum?
A
- 10% of the brains volume
- coordination, maintenance of posture, maintenance of muscle tone/balance and motor learning
31
Q
cerebellums coordination and precision function
A
- receives input from the sensory systems, and visual and vestibular info
- inputs help cerebellum fine-tune motor commands for accurate and smooth movement
32
Q
cerebellums error detection and correction function
A
- compares intended motor output from motor cortex with actual feedback received from body’s sensory systems
- if error, it sends corrective signal to adjust allowing precise movements
33
Q
cerebellums motor learning function
A
- stores motor memories and adjusts future movements based on past experiences
- essential for learning new skills and refine original patterns with practice
34
Q
cerebellums posture and balance function
A
- receives info about body’s position and orientation in space and integrates this info to modulate muscle activity ensuring stability during movements
35
Q
cerebellums timing and rhythm function
A
- coordinates timing of muscle contractions
- smooth and well-timed execution of complex movements
36
Q
cerebellums feedforward control function
A
- predicting the consequences of motor commands allowing for adjustments before the movement occurs
37
Q
was is ataxia cerebellar damage
A
- abnormal execution of multi-jointed voluntary movements due to lack of coordination
- caused by stroke, MS, tumours
- unsteady and clumsy
- struggles with precise motor control like walking, reaching and fine movements, movement can appear jerky
38
Q
dysmetria cerebellar damage
A
- type of ataxia
- lack of coordination = inability to control range of movement and judge distance
- overshoot or undershoot targets
39
Q
major components of cerebellum?
A
- cerebellar peduncles
- cerebellar cortex
- deep cerebellar nuclei
40
Q
what are the cerebellar peduncles?
A
- bundles of axons connecting cerebellum to other parts of CNS facilitating coordination, communication and motor functions
- superior, middle and inferior
41
Q
superior peduncle
A
- dorsal aspect of brainstem
- carry efferent fibres, transmit signals to midbrain and thalamus
- motor coordination and control
- crossing of fibres in midbrain
42
Q
middle peduncle
A
- located in ventral aspect of pons
-afferent fibres carrying input from cerebral cortex to cerebellum - convey info about planned/ongoing movements
- learning and integration of sensory info
43
Q
inferior peduncle
A
- dorsal aspect of medulla oblongata
- afferent and efferent fibres carrying input from spinal cord to cerebellum
- output info to vestibular nuclei and reticular formation influencing balance, posture and coordination
44
Q
what is the cerebellar cortex?
A
- neural circuitry integrating inputs from cortex, brainstem and spinal cord
- modulates motor outputs
45
Q
cerebrocerebellum
A
- largest, protects to and from cerebral cortex
- planning and execution of voluntary movement
- connected with cerebral cortex especially motor planning and coordination areas
46
Q
major components of cerebellar cortex
A
- cerebrocerebellum
- spinocerebellum
- vestibulocerebellum
47
Q
spinocerebellum
A
- coordination of muscle activity and maintenance of posture
- input from spinal cord
48
Q
vestibulocerebellum
A
- control of balance and eye movements
- input from vestibular system
49
Q
main components of the deep cerebellar nuclei
A
- dentate
- interposed
- fastigial
50
Q
dentate
A
- most lateral
- in cerebrocerebellum
- output to motor cortex via superior peduncle and thalamus
51
Q
interposed
A
- located in intermediate cortex od spinocerebellum
- output to red nucleus via superior peduncle
52
Q
fastigial
A
- most medial
- output to spinal cord and vestibular nucleus
53
Q
what does cerebellar circuitry involve?
A
- multiple layers of neurons and cell types with intricate circuitry
- highly folded structure = folia
54
Q
main components of the cerebellar circuitry
A
- mossy fibres (granule layer)
- granule cells (granule layer)
- climbing fibres (granule layer)
- purkinje cells (purkinje cell layer)
- parallel fibres (molecular layer)
55
Q
what are purkinje cells?
A
- cell body and vast dendrite tree
- dendrites receive afferent input from parallel fibres and climbing tree
- output to deep cerebellar nuclei
- cerebellar output via purkinje cells
- inhibitory function
56
Q
mossy fibres
A
- primary neurons carrying info Tinto cerebellum
- activate granule cells and cellebellar nuclei
57
Q
granule cells
A
- attach to parallel fibres which synapse with dendrites of prukinje cells
58
Q
climbing fibre
A
- only one
- excites purkinje cells directly
- originates in inferior olive
- senses error signals to elicit learning
59
Q
conditioned blink eye response
A
- UCS elicits reflex response causing an UCR
- sufficient number of paired association CS elicits CR and attenuates UCR
60
Q
Marr-Albus-Ito hypothesis
A
- mechanism underpinning eye-blink response
- associative learning
- simultaneous activation of climbing fibres and mossy fibres causes long-term changes in parallel fibre to purkinje synapses, resulting in long term depression
- as purkinje cells are inhibitory, LTD increases output of deep cerebellar nuclei
