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Psychology 210. Lecture 6 Kevin R Smith. The motor system. Outline Muscles Reflexes Brain motor system Disorders of movement. Types of Muscles. Smooth muscle Digestive tract Arteries Reproductive system Controlled by autonomic nervous system Striated muscle: Two types

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psychology 210

Psychology 210

Lecture 6

Kevin R Smith

the motor system
The motor system
  • Outline
    • Muscles
    • Reflexes
    • Brain motor system
    • Disorders of movement
types of muscles
Types of Muscles
  • Smooth muscle
    • Digestive tract
    • Arteries
    • Reproductive system
    • Controlled by autonomic nervous system
  • Striated muscle: Two types
    • Cardiac muscle
    • Skeletal muscle
  • Monosynaptic reflexes
    • Involves only one synapse (two neurons)
  • Polysynaptic reflexes
    • Involve more than one synapse
polysynaptic reflexes
Reciprocal inhibition

When one muscle is voluntarily contracted, the other is automatically inhibited

Polysynaptic reflexes
polysynaptic reflexes1
Polysynaptic reflexes
  • Flexion reflex
    • Jerking hand away from hot surface
    • Pain receptors transmit info to interneurons in spinal cord
    • Interneurons excite the muscles and inhibit the reciprocal muscles
    • Leads to the action
reflexes change
Reflexes change….
  • Born with
    • Rooting
    • Stepping
    • Babinski
    • Grasping
  • All are gone by 1 year of age
    • Never actually gone, but rather inhibited
pathway to the brain
Pathway to the Brain
  • Two routes
    • Lateral pathway
      • Voluntary movements
    • Ventromedial pathway
      • Automatic processes
lateral pathway
Lateral pathway
  • Information comes from the motor cortex or the red nucleus to the spinal cord
  • Contralateral organization
ventromedial pathway
Ventromedial pathway
  • Posture
  • Coordinating head and trunk movements with eye movements
  • Respiration, coughing, sneezing
  • Does not appear to initiate movements
  • Plays a role in coordinating movements
    • Contracts and relaxes the muscles at the right times to produce a sequence of movements
  • Receives information from motor cortex via the pons
  • Sends excitatory information back to motor cortex via the thalamus
basal ganglia
Basal Ganglia
  • Collection of cell bodies
    • Caudate nucleus
    • Putamen
    • Globus pallidus
  • Like the cerebellum, receives information from the motor cortex and sends it back to the motor cortex via the thalamus
    • The information is inhibitory though
the basal ganglia
The Basal Ganglia
  • Damage can lead to Parkinson’s Disease
  • Theory
    • Less dopaminergic activity in Basal Ganglia
    • Less inhibition of thalamus
    • Overstimulation of thalamus
    • Less activity in frontal lobe
symptoms of parkinson s disease
Symptoms of Parkinson’s Disease
  • Difficulty moving
  • Tremor in resting body parts
  • Frozen facial expressions
  • Stooped posture
  • Loss of balance, frequent falls
  • Autonomic disturbances
  • Premature death
causes of parkinson s disease
Causes of Parkinson’s Disease
  • Degeneration of substantia nigra (midbrain)
  • Less dopaminergic activity in basal ganglia
  • Genetics in early-onset cases
  • Correlates with exposure to toxins:
    • Synthetic heroin
    • Agricultural chemicals
    • Solvents
treatments of parkinson s disease
Treatments of Parkinson’s Disease
  • L-DOPA
    • Precursor to Dopamine
    • Leads to an increase in the amount of dopaminergic activity throughout the body
    • Benefit: increases in dopamine levels in the basal ganglia lead to a decrease in the PD symptoms
    • Cost: BAD side effects
      • Increases in dopamine levels throughout the body lead to issues with the liver and other organs
      • ONLY treats the symptoms, not the cause
motor cortex
Motor cortex
  • Primary motor cortex
  • Supplementary motor area (SMA)
  • Premotor area
  • Involved in the planning of controlled movements
  • Receives information from the visual pathway and send info to primary motor cortex and the brainstem
premotor areas
Premotor areas
  • Involved in the sensory guidance of movements
  • Orienting the body correctly to pick up a glass
  • The fine coordination needed comes from the cerebellum
  • Motor systems are highly intertwined with feedback from the visual system
  • Gives the ability to change a movement throughout the movement
disorders of the motor system
Disorders of the motor system
  • Toxins
  • Myasthenia gravis
  • Muscular dystrophy
  • Polio
  • Lou Gehrig’s disease
  • Huntington’s Disease
  • Parkinson’s Disease
  • Cholinergic agonists (e.g. black widow spider toxin) overstimulate the neuromuscular junction, producing convulsions followed by paralysis.
  • Cholinergic antagonists paralyze muscles:
    • Curare
    • Botulinum toxin
    • Cobra venom
myasthenia gravis
Myasthenia gravis
  • Autoimmune disorder
  • Results in the breakdown of acetylcholine (ACh) receptors on the muscle fiber
  • Symptoms include extreme weakness, fatigue, droopy eyelids, slurred speech, difficulty swallowing and breathing
  • Treatments include medications that suppress the immune system or inhibit acetylcholinesterase (AChE)
muscular dystrophy
Muscular dystrophy
  • Heritable conditions involving the muscle protein dystrophin.
  • Premature muscle growth is followed by degeneration.
  • Gene therapy may provide effective treatments soon.
  • The polio virus destroys alpha motor neurons.
  • Without neural input, muscles degenerate.
  • Vaccination may eradicate polio world-wide in the next few years.
lou gehrig s disease
Lou Gehrig’s Disease
  • aka Amyotrophic Lateral Sclerosis
  • Motor neurons in the spinal cord and brainstem degenerate.
  • 5-10% of cases are due to genetic defects
    • The rest are sporadic: no known cause
  • Correlated environmental factors include vigorous activity and viruses.
  • Treatments for symptoms are being developed
huntington s disease
Huntington’s Disease
  • A genetically programmed degeneration of neurons
  • Produces involuntary, jerky movements, depression, hallucination and delusions.
huntington s disease1
Huntington’s Disease
  • Heritable condition
    • Parents with HD pass it on 50% of the time
  • Antibiotics and fetal tissue transplants and maintaining activity may provide treatment in the future.