Ch 15 Lower Motor Neuron Circuits and Motor

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Ch. 15: Lower Motor Neuron Circuits and Motor Control - a model for understanding

Ch. 15: Lower Motor Neuron Circuits and Motor Control - a model for understanding the nervous system 1/19/2022 55 -485

Neural centers responsible for movement • 4 interactive subsystems contribute to motor control 1/19/2022

Neural centers responsible for movement • 4 interactive subsystems contribute to motor control 1/19/2022 55 -485

Neural centers responsible for movement 1) Gray matter of spinal cord and brainstem -

Neural centers responsible for movement 1) Gray matter of spinal cord and brainstem - local motor neurons innervate skeletal muscle cells - motor neurons of cranial nerves from cell bodies in the brain stem - local circuit neurons are the major source of synaptic input to the lower motor neurons. 1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

Neural centers responsible for movement 2) Upper motor neurons - cell bodies in brainstem

Neural centers responsible for movement 2) Upper motor neurons - cell bodies in brainstem or cerebral cortex 1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

Neural centers responsible for movement 3) Cerebellum - regulate activity of upper motor neurons

Neural centers responsible for movement 3) Cerebellum - regulate activity of upper motor neurons 1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

Neural centers responsible for movement • 4) Basal Ganglia • Regulate upper motor neurons

Neural centers responsible for movement • 4) Basal Ganglia • Regulate upper motor neurons 1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

Basal ganglia - caudate, putamen, globus pallidus -subthalamic nucleus, substantia nigra 1/19/2022 55 -485

Basal ganglia - caudate, putamen, globus pallidus -subthalamic nucleus, substantia nigra 1/19/2022 55 -485

1) Gray matter of spinal cord and brainstem • Lower motor neurons send axons

1) Gray matter of spinal cord and brainstem • Lower motor neurons send axons out of the brain stem and spinal cord to innervate skeletal muscles of the head and body. 1/19/2022 55 -485

Gray matter of spinal cord and brainstem • Local circuit neurons – Synaptic input

Gray matter of spinal cord and brainstem • Local circuit neurons – Synaptic input to lower motor neurons 1/19/2022 55 -485

Gray matter of spinal cord and brainstem • Lower motor neurons convey voluntary and

Gray matter of spinal cord and brainstem • Lower motor neurons convey voluntary and reflex commands to skeletel muscle 1/19/2022 55 -485

Gray matter of spinal cord and brainstem • Local circuit neurons – Receive descending

Gray matter of spinal cord and brainstem • Local circuit neurons – Receive descending projections from higher brain centers – Also receive sensory input from higher brain centers 1/19/2022 55 -485

Gray matter of spinal cord and brainstem • Circuits provide co-ordination between muscle groups

Gray matter of spinal cord and brainstem • Circuits provide co-ordination between muscle groups for movement – Are the final common path for movement. 1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

2) Upper motor neurons • Cell bodies in the brainstem or cerebral cortex •

2) Upper motor neurons • Cell bodies in the brainstem or cerebral cortex • Axons descend to synapse with local circuit neurons, sometimes directly onto lower motor neurons 1/19/2022 55 -485

2) Upper motor neurons • In the cortex – Initiate voluntary movements – Initiate

2) Upper motor neurons • In the cortex – Initiate voluntary movements – Initiate complex spatiotemporal sequences of skilled movements – E. g. descending projections from the frontal lobe (primary motor cortex and lateral premotor cortex) 1/19/2022 55 -485

2) Upper motor neurons • In the brainstem – Regulate muscle tone for orienting

2) Upper motor neurons • In the brainstem – Regulate muscle tone for orienting eyes, head and body wrt sensory information (balance, somatic, sound, vision input) – Imp. For movement and posture 1/19/2022 55 -485

3) Cerebellum • Does not directly access local circuit neurons or lower motor neurons

3) Cerebellum • Does not directly access local circuit neurons or lower motor neurons • Regulate the upper motor neurons • Located on the dorsal suface of the pons 1/19/2022 55 -485

3) Cerebellum • Detects the difference between an intended movement and the movement that

3) Cerebellum • Detects the difference between an intended movement and the movement that is actually performed (servomechanism) • Reduces movement error in short term and in long term (learning) eg. Riding a bike. 1/19/2022 55 -485

4) Basal ganglia • No direct access to local circuit neurons or to lower

4) Basal ganglia • No direct access to local circuit neurons or to lower motor neurons • Regulate upper motor neurons • Suppress unwanted movement • Prepare upper motor neurons for movements to start 1/19/2022 55 -485

How does thought lead to movement? • Still poorly understood • Clear picture at

How does thought lead to movement? • Still poorly understood • Clear picture at the level of muscles themselves. • Start with the lower motor neurons and their targets. 1/19/2022 55 -485

Motor neuron - muscle relationships • Neuronal tracer injections into the cell body show

Motor neuron - muscle relationships • Neuronal tracer injections into the cell body show the pathway on motor neuron axons • motor neuron pools are all of the motor neurons that innervate a muscle. 1/19/2022 55 -485

Motor neuron - muscle relationships • Motor neuron pools run together in the spinal

Motor neuron - muscle relationships • Motor neuron pools run together in the spinal cord. • An orderly arrangement between the motor neuron pools and the muscles that they innervate*** - a rule for the nervous system (mapping, topography) 1/19/2022 55 -485

Motor neuron - muscle relationships • Fig. 15. 3 – Topography – Neurons for

Motor neuron - muscle relationships • Fig. 15. 3 – Topography – Neurons for postural muscles are medial in the cord – Neurons for the shoulders are next most lateral – Neurons for upper arms are next lateral. – Neurons for distal extremeties are most lateral. 1/19/2022 55 -485

Motor neuron - muscle relationships • Spatial organization gives information about functions 1/19/2022 55

Motor neuron - muscle relationships • Spatial organization gives information about functions 1/19/2022 55 -485

Motor neuron - muscle relationships • Two types of lower motor neurons in the

Motor neuron - muscle relationships • Two types of lower motor neurons in the motor neuron pools – Small motor neurons – motor neurons 1/19/2022 55 -485

1/19/2022 55 -485

1/19/2022 55 -485

Small motor neurons • Innervate sensory structures in skeletal muscle (muscle spindles) • Muscle

Small motor neurons • Innervate sensory structures in skeletal muscle (muscle spindles) • Muscle spindles are embedded in connective tissue – Are called intrafusal muscle fibers 1/19/2022 55 -485

Small motor neurons • In Intrafusal muscle fibers – Sets the intrafusal muscle fiber

Small motor neurons • In Intrafusal muscle fibers – Sets the intrafusal muscle fiber to an appropriate length for the sensory neuron to function. 1/19/2022 55 -485

motor neurons • Large • Innervate extrafusal muscle fibers. These generate force for

motor neurons • Large • Innervate extrafusal muscle fibers. These generate force for movement and posture. 1/19/2022 55 -485

LOWER MOTOR NEURON LOWER MOTOR NEURON PARAPLEGIA DRLOWER MOTOR NEURON LOWER MOTOR NEURON PARAPLEGIA DR
UPPER MOTOR NEURON LOWER MOTOR NEURON DR SHUBHANGIUPPER MOTOR NEURON LOWER MOTOR NEURON DR SHUBHANGI
Lower Motor Neuron Circuits and Motor Control ILower Motor Neuron Circuits and Motor Control I
Motor Neuron Diseases n Motor Neuron Diseases nMotor Neuron Diseases n Motor Neuron Diseases n
Motor neuron disease Multiple sclerosis Motor neuron diseaseMotor neuron disease Multiple sclerosis Motor neuron disease
Motor neuron disease Multiple sclerosis Motor neuron diseaseMotor neuron disease Multiple sclerosis Motor neuron disease
Neuron Neuron Neuron Mitocondrie Membrana Nucleu RE rugosNeuron Neuron Neuron Mitocondrie Membrana Nucleu RE rugos
Neuron Talk What one neuron tells another neuronNeuron Talk What one neuron tells another neuron
Motor Neuron diseases Classification Lower motor neurons disordersMotor Neuron diseases Classification Lower motor neurons disorders
Motor Function Upper VS lower Motor neuron signsMotor Function Upper VS lower Motor neuron signs
Nerve Excitation Biophysics Neurons Motor neuron Sensory neuronNerve Excitation Biophysics Neurons Motor neuron Sensory neuron
Input Integration Response Interneuron Sensory Neuron Motor NeuronInput Integration Response Interneuron Sensory Neuron Motor Neuron
Somatic Motor Pathways Upper motor neurons lower motorSomatic Motor Pathways Upper motor neurons lower motor
UPPER AND LOWER MOTOR NEURON FUNCTION AND LESIONUPPER AND LOWER MOTOR NEURON FUNCTION AND LESION
Upper Motor Neuron Lesion UMNL Pyramidal Lesion LowerUpper Motor Neuron Lesion UMNL Pyramidal Lesion Lower
Lower Motor Neuron Conditions Paediatric Orthopaedics Presentation 2Lower Motor Neuron Conditions Paediatric Orthopaedics Presentation 2
Motor neuron muscle relationships Two types of lowerMotor neuron muscle relationships Two types of lower
Motor neuron muscle relationships Two types of lowerMotor neuron muscle relationships Two types of lower
A motor unit consists of one motor neuronA motor unit consists of one motor neuron
A motor unit consists of one motor neuronA motor unit consists of one motor neuron
Lower Bound Theory Lower Bounds Lower bound anLower Bound Theory Lower Bounds Lower bound an
Nervous System Neuron Neuron Neurons Schwann cells andNervous System Neuron Neuron Neurons Schwann cells and
The Brain and neuron Content Brain Neuron NeuralThe Brain and neuron Content Brain Neuron Neural
Neuron The neuron Neurons The functional and structuralNeuron The neuron Neurons The functional and structural