Brain Stem Motor Function 1172022 brain stem 1

Brain Stem Motor Function 1/17/2022 brain stem 1

Neural centers for control of movements Motor cortex Basal ganglia cerebellum Brain Stem Spinal Cord 1/17/2022 Skeletal muscles brain stem 3

Functional Anatomy Brain stem in the physiological sense is comprised of – Medulla, Pons, Mesencephalon (midbrain) Neuronal circuits within this area control many physiological functions – BP, respiration, body temp, sleep & wakefulness, GIT 1/17/2022 brain stem 4

Functional Anatomy Control of physiological functions – Stereotyped movements of the body – Equilibrium and balance – Eye movement In addition Reticular formation (RF) and Vestibular Nuclei – Important components of motor control system 1/17/2022 brain stem 5

Functional Anatomy Serves as a way station for – Command signals from higher neural centres that command the brain stem to Initiate, modify specific control functions throughout the body 1/17/2022 brain stem 6

Brain Stem Motor Centers Red nucleus Midbrain Vestibular nucleus Pontine Ret. formation Medullar Ret. formation Medulla oblongata 1/17/2022 brain stem 7

Brain Stem Motor centres – Red nucleus – Lateral vestibular nucleus (Deiter’s nucleus) – Certain parts of reticular formation in pons and medulla oblongata 1/17/2022 brain stem 8

Motor centres Have efferent fibres that influence motor pathways in – Spinal cord – Cranial motor nerves Form part of efferent pathways from higher motor centres 1/17/2022 brain stem 9

The Red Nucleus Lie in the midbrain Receive signals from the – Motor cortex, Cerebellum Project signals to the spinal cord: Rubro-Spinal Tract (RUST) Stimulation of the system – Excitation of Flexors – Inhibition of extensors 1/17/2022 brain stem 10

Red Nucleus RUST crosses over the opposite side Runs through the spinal cord close to CST Connect to MN Red nucleus RUST - Extensors – Inhibit extensors – Excite flexors + Flexors 1/17/2022 brain stem 11

Reticular Formation Brain stem reticular formation – Two areas with motor control activity Pontine reticular nucleus Medullar reticular nucleus – Give rise to reticulospinal tracts 1/17/2022 brain stem 12

Reticular formation The two sets of nuclei Function antagonistically to each other – Pontine exciting the Antigravity muscles – Medullary inhibiting them 1/17/2022 brain stem 13

Pontine Reticular Nucleus Pontine reticular Nucleus Located in the pons, extends to midbrain Transmit excitatory signals down the spinal cord – Pontine (medial) Reticulospinal tract (MREST) Terminate on MN M-REST 1/17/2022 + Extensors – Excite extensors (antigravity) – Inhibit flexors - Flexors brain stem 14

Pontine Reticular Nucleus Pontine reticular Nucleus Pontine (medial) Reticulospinal tract (M -REST) – Also excite Axial muscles which support body against gravity – Muscle of the vertebral Extensor muscles of limbs + Extensors M-REST 1/17/2022 - Flexors brain stem 15

Pontine Reticular Nucleus Cells of the Pontine R. N have Cerebral cortex, basal ganglia, cerebellum – High degree of excitability (inherent) Vestibular N. , Cerebellum Excitability is held in check by Excitatory signals ++ -- Inhibitory signals Pontine R. N – Inhibitory signals Cerebral cortex Basal ganglia Cerebellum 1/17/2022 ++ brain stem α MN, γ MN excitability increases Muscle spaciticity 16

Pontine Reticular Nucleus Receive excitatory signals from – Vest. Nucleus – Cerebellum (deep nucleus) Vestibular N. , Cerebellum Excitatory signals ++ If unopposed by medullary syst -- Inhibitory signals Pontine R. N – Causes powerful excitation of antigravity muscles – SPACITICITY 1/17/2022 Cerebral cortex, basal ganglia, cerebellum brain stem ++ α MN, γ MN excitability increases Muscle spaciticity 17

Medullary Reticular Nucleus Medullar reticular Nucleus Located in the reticular area of medulla Transmit inhibitory signals down the spinal cord – Medullar (lateral) Reticulospinal tract (L-REST) Connect to MN L-REST – Inhibit extensors – Excite flexors - Extensors + Flexors 1/17/2022 brain stem 18

Medullar Reticular System Receive strong imputes by way of collaterals from CST, RUST, other motor pathways These normally activate the medullar inhibitory system This counteracts the excitatory effects of Pontine reticular system Pontine R. N CST, RUST, other motor pathways ++ Medullar R. N -- ++ α MN, γ MN 1/17/2022 brain stem 19

Medullar Reticular System Medullar R. N Pontine R. N CST, RUST, other motor pathways ++ CST, RUST cerebella • These normally inhibit medullar inhibitory system -- ++ α MN, MN 1/17/2022 • Can also receive inhibitory imputes by way of collaterals from CST, RUST, cerebellum • When the brain wishes to cause excitation of Pontine reticular system, to facilitate standing brain stem 20

Vestibular Nucleus Located in the pons and medullar Project to spinal cord – Vestibulospinal tract (VEST) Connect to MN – Excite extensors – Inhibit flexors + Extensors VEST 1/17/2022 - Flexors brain stem 21

Vestibular Nucleus Provide strong excitatory signals to antigravity muscles Selectively control the excitation of different antigravity muscles + Extensors VEST 1/17/2022 – To maintain equilibrium and balance in response to vestibular apparatus - Flexors brain stem 22

Brain Stem Motor Effects CST RUST L - REST Flexors excited VEST M- REST Extensors inhibited Flexors inhibited Extensors excited 1/17/2022 brain stem 23