Brain Stem Motor Function April 25, 2019 brain stem

Neural centers for control of movements Motor cortex Basal ganglia Brain Stem cerebellum Spinal Cord Skeletal muscles April 25, 2019 brain stem

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 April 25, 2019 brain stem

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 April 25, 2019 brain stem

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 April 25, 2019 brain stem

Brain Stem Motor Centers Red nucleus Midbrain Vestibular nucleus Pons Pontine Ret. formation Medullar Ret. formation Medulla oblongata April 25, 2019 brain stem

Brain Stem Motor centres Red nucleus Lateral vestibular nucleus (Deiter’s nucleus) Certain parts of reticular formation in pons and medulla oblongata April 25, 2019 brain stem

Motor centres Have efferent fibres that influence motor pathways in Spinal cord Cranial motor nerves Form part of efferent pathways from higher motor centres April 25, 2019 brain stem

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 April 25, 2019 brain stem

Red Nucleus RUST crosses over the opposite side Runs through the spinal cord close to CST Connect to MN Inhibit extensors Excite flexors Red nucleus RUST Extensors + Flexors April 25, 2019 brain stem

Reticular Formation Brain stem reticular formation Two areas with motor control activity Pontine reticular nucleus Medullar reticular nucleus Give rise to reticulospinal tracts April 25, 2019 brain stem

Reticular formation The two sets of nuclei Function antagonistically to each other Pontine exciting the Antigravity muscles Medullary inhibiting them April 25, 2019 brain stem

Pontine Reticular Nucleus Located in the pons, extends to midbrain Transmit excitatory signals down the spinal cord Pontine (medial) Reticulospinal tract (M-REST) Terminate on MN Excite extensors (antigravity) Inhibit flexors + Extensors - Flexors M-REST April 25, 2019 brain stem

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 - Flexors M-REST April 25, 2019 brain stem

Pontine Reticular Nucleus Cells of the Pontine R.N have High degree of excitability (inherent) Excitability is held in check by Inhibitory signals Cerebral cortex Basal ganglia Cerebellum Cerebral cortex, basal ganglia, cerebellum Vestibular N., Cerebellum Inhibitory signals Excitatory signals ++ - - Pontine R.N Muscle spaciticity + + α MN, γ MN excitability increases April 25, 2019 brain stem

Pontine Reticular Nucleus Receive excitatory signals from Vest. Nucleus Cerebellum (deep nucleus) If unopposed by medullary syst Causes powerful excitation of antigravity muscles SPACITICITY Cerebral cortex, basal ganglia, cerebellum Vestibular N., Cerebellum Inhibitory signals Excitatory signals ++ - - Pontine R.N Muscle spaciticity + + α MN, γ MN excitability increases April 25, 2019 brain stem

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 Inhibit extensors Excite flexors L-REST Extensors + Flexors April 25, 2019 brain stem

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 April 25, 2019 brain stem

Medullar Reticular System Medullar R.N Can also receive inhibitory imputes by way of collaterals from CST, RUST, cerebellum These normally inhibit medullar inhibitory system When the brain wishes to cause excitation of Pontine reticular system, to facilitate standing Pontine R.N CST, RUST, other motor pathways ++ - - CST, RUST cerebella ++ α MN, MN April 25, 2019 brain stem

Vestibular Nucleus Located in the pons and medullar Project to spinal cord Vestibulospinal tract (VEST) Connect to MN Excite extensors Inhibit flexors + Extensors - Flexors VEST April 25, 2019 brain stem

Vestibular Nucleus Vestibular Nucleus Provide strong excitatory signals to antigravity muscles Selectively control the excitation of different antigravity muscles To maintain equilibrium and balance in response to vestibular apparatus + Extensors - Flexors VEST April 25, 2019 brain stem

Brain Stem Motor Effects CST RUST L - REST VEST Flexors excited Extensors inhibited M- REST Flexors inhibited Extensors excited April 25, 2019 brain stem