Central control of movement-I

Central control of movement-I - Central Control of Movement...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Central Control of Movement I Gemechu Wirtu PHSI 0441, Spring 2012 Sources: - Cunningham and Klein Chapter 10 - Boron and Boulpaep – Chapter 16 - Others as cited
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Neural circuit Even in the most primitive animals, a neuron never functions alone and needs synaptic networks called circuits . Within a CNS region, neurons form synaptic connections called local circuits In simpler animals (Jelly fish), major neurons lack specialization and are multifunctional (e.g. same neuron can serve as photodetector, pattern generator for swimming rhythms, and motor neurons) In higher animals, each neuron in a circuit may have very specialized properties; circuits may primarily be: - Sensory (e.g. retina) - Motor (e.g. ventral root of spinal cord)
Background image of page 2
Local circuits in the spinal c. consisting of inputs (e.g., sensory axons of dorsal roots), interneurons (excitatory/inhibitory), and outputs (e.g., α motor neurons that send their axons through the ventral roots). Most local circuits contain 3 elements: input axons, interneurons, & projection (output) neurons; Sp. c. inputs come from: - dorsal root afferents - UMN from brain - Spinal segments (ipsi- and contraleteral)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Local circuits in the cerebral cortex consisting of inputs (e.g. from the thalamus), excitatory and inhibitory interneurons, and output neurons (e.g. pyramidal cells) Drawing by S.R. Cajal of Golgi-stained cortex of a 1.5 month old infant
Background image of page 4
Movement α motor neuron is signaled by descending upper motor neurons or from incoming sensory neurons (or interneurons) in a reflex arc Extrafusal muscle fibers contract by commands from α lower motor neuron Movement is by contraction of a number of extrafusal skeletal muscle fibers within varying numbers of motor units Thus the α motor neuron is the “final common neural pathway” by which the nervous system can initiate the extrafusal muscle contractions that result in movement
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Movement is divided into 2 general forms 1. Learned, voluntary, conscious and skilled form Dominated by flexor muscle activation Due to contraction of a few muscle groups, which are distal to the spinal column In the spinal cord gray mater, the α motor neurons that control the more distal muscles are located laterally Initiated by UMN whose tracts project through more lateral regions of spinal c. white mater and terminate in lateral regions of spinal c. gray mater
Background image of page 6
Movement is divided into 2 general forms (cont.) 2. Postural and antigravity; mostly subconscious and involuntary muscle activity Dominated by extensor muscle contraction Maintenance of posture includes longer-term contraction of larger groups of muscles, which are closer to or proximal to the spinal column In the spinal cord, the neurons controlling proximal and axial muscles for posture are located medially UMN tracts project through and terminate in more medial regions of spinal c. white and gray mater, respectively
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Hierarchical organization of control of movement Central control of movement is hierarchically
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 32

Central control of movement-I - Central Control of Movement...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online