PS267 Lecture Notes - Lecture 7: Alpha Motor Neuron, Rubrospinal Tract, Neuromuscular Junction
Chapter 8: Action
● 30-40% of brain is devoted to visual modality (says visual scientists)
● If you talk to a motor control expert, they say 50% of brain is devoted to motor system
● Humans have extraordinary ability to develop new motor skills
● And what can go wrong… Parkinson’s, MPTP
Parkinson’s disease
● Can’t move face muscles in coordinated way
● Shaking
● Disrupts posture
MPTP (synthetic form of heroin)
● Selective neurotoxin for dopamine
OVERVIEW
● Anatomy and control of motor structure
● Physiological analysis of motor pathways
Muscle Basics 101
● Muscle contraction is the basis of all movements
● Alpha motor neurons in the spinal cord communicate with muscle fibers by releasing
acetylcholine, which influences muscle activity by causing muscle contractions
● An electromyogram is recorded from electrodes placed on skin over muscle to measure
electrical activity produced by the firing of alpha motor neurons
● Antagonist pairs of muscles (extensors vs flexors) span most of our joints, eg biceps vs
triceps
● The synapse where a motor neuron's axon meets a muscle fibre = neuromuscular
junction
● Affector: carries neural impulses to CNS (sensory)
● Effector: receives neural impulses from CNS (motor, muscles)
● Muscles are activated by the alpha motor neurons
Motor unit is relationship between one alpha motor neuron and groups of muscles (single
muscle or groups)
Two major outputs from brain to spinal cord
● Pyramidal system (human beings extremely dependent on this, controls digits in hands
and toes) - starts in neocortex
○ Corticospinal tract
■ Medullary pyramids is where motor movements cross hemispheres
● Extrapyramidal system - starts in midbrain, many systems involved in whole body
movement
○ Rubrospinal tract
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
If you talk to a motor control expert, they say 50% of brain is devoted to motor system. 30-40% of brain is devoted to visual modality (says visual scientists) Humans have extraordinary ability to develop new motor skills. And what can go wrong parkinson"s, mptp. Can"t move face muscles in coordinated way. Muscle contraction is the basis of all movements. Alpha motor neurons in the spinal cord communicate with muscle fibers by releasing acetylcholine, which influences muscle activity by causing muscle contractions. An electromyogram is recorded from electrodes placed on skin over muscle to measure electrical activity produced by the firing of alpha motor neurons. Antagonist pairs of muscles (extensors vs flexors) span most of our joints, eg biceps vs triceps. The synapse where a motor neuron"s axon meets a muscle fibre = neuromuscular junction. Affector: carries neural impulses to cns (sensory) Effector: receives neural impulses from cns (motor, muscles) Muscles are activated by the alpha motor neurons.
