1. Pathways: movement and sensation Pedro Amarante Andrade, PhD

2. LEARNING OUTCOMES Learn the cross-sectional anatomy of the spinal cord
Be able to explain the types of connections between and within the CNS and PNS
Understand the basic functions of the brainstem and how it relates to the spinal cord pathways

3. MOVEMENT

4. MOVEMENT OVERVIEW Complex and incompletely understood
Planned in sensorimotor areas of the cortex
Is effected by pathways of descending neurons, under the control of the cerebellum and the basal ganglia
Control is achieved through sensory feedback from muscles/joints
And information from the eyes and ears (vision and balance) also influences the motor pathways

5. MOVEMENT OVERVIEW

6. MOVEMENT OVERVIEW
Biological Psychology: An introduction to Behavioural,
Cognitive, and Clinical Neuroscience.
S. Marc Breedlove, Simon Watson

7. LOCATION OF THE BASAL GANGLIA

8. CONTROL CIRCUITS
The CEREBELLUM: coordinates motor and sensory information
Gets info from the cortex about what muscles SHOULD be doing, and compares this with what is ACTUALLY happening
The basal ganglia: involved in control of background movement, and initiation of movement patterns
Biological Psychology: An introduction to Behavioural, Cognitive, and
Clinical Neuroscience.S. Marc Breedlove, Simon Watson

9. VOLUNTARY MOVEMENT
Although skeletal movement is under our voluntary control, much of it is automatic
Speech, chewing, swallowing comes under the heading of automatic movements that can be altered voluntarily
Can be affected by developmental abnormalities or acquired brain injury

10. CORTICAL ANATOMY OF THE MOTOR SYSTEM

11. CORTICAL ANATOMY OF THE MOTOR SYSTEM
Blood flow to this region increases prior to movement actually occurring suggesting a role in planning the movement flow

12. HOMUNCULI

13. SOMATOTOPIC
CORTEX
The primary motor and sensory cortices are somatotopically arranged in the precentral and postcentral gyri with the body represented upside down and individual areas represented out of proportion to their actual size
Note that disproportionately more cortex devoted to the
movements of the muscles involved in speech

14. THE PATHWAYS
A neural pathway connects one part of the nervous system with another via a bundle of axons
Motor
Efferent
Sensory
Afferent

15. THE PATHWAYS The motor pathways The sensory pathways
The white matter pathways
The grey matter pathways

16. MOTOR PATHWAY Neurons

17. CORTICAL ANATOMY OF THE
MOTOR SYSTEM

18. FUNCTIONAL DIVISIONS OF THE MOTOR SYSTEM
DIRECT activation pathway (pyramidal tracts):
Upper Motor Neurons: corticobulbar and corticospinal tracts
INDIRECT activation pathway (extrapyramidal tracts):
Upper Motor Neurons: corticorubral, corticoreticular, rubrospinal, reticulospinal, vestibulospinal and related tracts
Final common pathway (FCP):
LMNs: generates activity in skeletal muscles

19. FUNCTIONAL DIVISIONS - MOTOR SYS.
SYSTEMS
TRACTS
ORIGIN
CONNECT TO
PYRAMIDAL
Corticobulbar
Cortex
Cranial nerves (Brainstem)
Corticospinal
Spinal cord
EXTRAPYRAMIDAL
Rubrospinal
Red nucleus
Pontine reticulospinal
Reticular formation
Medullary reticulospinal
Lateral vestibulospinal
Vestibular nuclei
Tectospinal
Midbrain tectum

20. THE DIRECT PATHWAYS PYRAMIDAL
PYRAMIDAL CELLS

21. THE DIRECT PATHWAYS PYRAMIDAL
PYRAMIDAL CELLS

22. Wikicommons. Polarlys and Mikael Häggström.
MOTOR TRACTS
Wikicommons. Polarlys and Mikael Häggström.
Sensory and motor neuros travel by different tracts within the spinal cord

23. THE DIRECT ACTIVATION PATHWAY Summary
Originates in the (predominantly) frontal cortex of each hemisphere
Directly connects this cortex to the lower motor neurons
The upper motor neurons synapse on:
anterior horn cells (corticospinal tract)
cranial nerve nuclei (corticobulbar tract)
The lower motor neurons emerge at the spinal and bulbar levels, and activate skeletal muscle
Activity leads to finely controlled, skilled and discrete movements
The ‘express’ route

24. THE INDIRECT PATHWAYS EXTRAPYRAMIDAL
The axons of the UMNs follow
the same path as those of the
corticospinal tract until they reach the brainstem, there some cross over,
others remain uncrossed
The UMNs terminate in the nuclei of
CN III IV V VI VII IX X XI
and XII

25. THE INDIRECT PATHWAYS EXTRAPYRAMIDAL

26. ALL PATHWAYS

27. INDIRECT ACTIVATION PATHWAYS
Sometimes called extrapyramidal pathway
Complex and incompletely understood (especially with regard to speech pathways)
Originates in motor, premotor and sensory cortex, and brainstem
Composed of numerous short pathways and interconnected structures (so are polysynaptic) involving the motor cortex, the basal ganglia, the limbic system, the thalamus, the cerebellum, the reticular formation AND nuclei in the brainstem

28. INDIRECT ACTIVATION PATHWAYS
UMNs synapse
Helps regulate reflexes & mediates subconscious automatic muscle activities e.g. posture and tone
Many of its activities are inhibitory (i.e. prevent too much tone/movement)
The ‘local’ route

29. EXAMPLES OF INDIRECT PATHWAYS
Rubrospinal - large muscle movement as well as fine motor control. Terminates cervical spinal cord. Facilitates flexion in the upper extremities
Reticulospinal - descends from reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb muscles. Involved mainly in locomotion and postural control
Tectospinal - coordinates head and eye movements. Connects midbrain tectum and spinal cord. Mediates reflex postural movements of head in response to visual and auditory stimuli

30. EXAMPLES OF INDIRECT PATHWAYS
Vestibulospinal – Vestibular nuclei receive information through vestibulocochlear nerve about changes in orientation of head. The nuclei relay motor commands through the vestibulospinal tract. Function of these motors commands = to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head.

31. SUMMARY OF DIRECT AND INDIRECT ACTIVATION PATHWAYS
Both pathways end on LMNs
These LMNs receive both excitatory and inhibitory stimulation from both pathways
The sum of this input determines the final response of an individual neuron in the pathway
The indirect pathway provides the framework (muscle tone, posture, regulation of reflex activity)
The direct pathway accomplishes the skilled, discrete muscle actions
The LMNs are referred to as the final common pathways or FCP

32. SENSORY SYSTEM

33. STRUCTURAL CLASSIFICATION OF NEURONS

34. SENSORY SYSTEM 3 or more neurons CNS – Thalamus Organ CNS –Cortex
CNS – Spinal cord
Organ
Ganglion
3 or more neurons

35. SENSORY FASCICULI TRACT ORIGIN CONNECT TO Spinocortical
Cuneatus (upper limbs)
-Gracilis (lower limbs)
Spinal cord
Cortex
Spinocerebellar
Cerebellum
Spinothalamic
Thalamus
Spino-olivary
Olivary complex

36. Wikicommons. Polarlys and Mikael Häggström.
MOTOR & SENSORY TRACTS
Wikicommons. Polarlys and Mikael Häggström.

37. WHITE MATTER PATHWAYS There are three types of white matter pathway:
Commissural
Association
Projection

38. COMMISSURAL WHITE MATTER PATHWAYS
Commissural white matter pathways connect the 2 hemispheres. The largest is the corpus callosum, with its posterior splenium, central body or trunk, anterior genu, and ventrally directed rostrum.
Besides the corpus callosum, commissural white matter pathways include the anterior commissure which connects the olfactory &
temporal regions,
and the posterior commissure

39. ASSOCIATION WHITE MATTER PATHWAYS
Connect cerebral areas within each hemisphere (generally bidirectional)
Contain short association fibres known as "U" or arcuate fibres that link adjacent cortical gyri
Long association fibres, all of which terminate in the frontal lobe are: the cingulate, the arcuate fasciculus, the superior occipitofrontal fasciculus, the inferior occipitofrontal fasciculus, and the uncinate fasciculus

40. PROJECTION WHITE MATTER PATHWAYS
White matter projections consist of long tracts which connect the cortex with the brainstem and spinal cord
These long tracts both ascend and descend.
The corona radiata consists of projection tracts running to and from the cortex
The projections converge at the internal capsule

42. STUDY THE STRETCH REFLEX
Revise the structure and function of the muscle spindle (see lecture 3, Nerves, Muscles and How They Work)
Watch the video or review the pathways involved in the stretch reflex:

43. NOTE THE TERMS: Agonist/antagonist Interneuron Reciprocal innervation
If you are unfamiliar with these terms through your reading, then look them up and write some definitions now

44. PARTICULAR RELEVANCE TO SLT
To perform accurate movements, information re the range, rate and force of contraction, and position of the muscles, is essential.
Muscle spindle actions are involved in controlling the rapid and fine muscle movements required for speech.
Sensory nerves from muscle spindles send out a continuous stream of impulses to the CNS
Muscle tone is maintained via these feedback mechanisms

45. PARALYSED MAN WALKS AGAIN

46. Amyotrophic Lateral Sclerosis