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Sensory and Motor Systems

30 April 2012. Sensory and Motor Systems. Sexual Behavior: Summary. Hormones play two roles in sexual development and behavior Organizational: Prenatal exposure to androgens masculinize sex organs AND brain structures

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Sensory and Motor Systems

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  1. 30 April 2012 Sensory and Motor Systems

  2. Sexual Behavior: Summary • Hormones play two roles in sexual development and behavior • Organizational:Prenatal exposure to androgens masculinize sex organs AND brain structures • Activational: Exposure to sex hormones (estradiol, progesterone, testosterone) in adulthood leads to the expression of sexual behavior • Gender, Gender Identity, Sexual Orientation and Sexual Behaviordepend on brain organization

  3. What does the sry gene code for? • Sex Determining Factor • Testis Determining Factor • Anti-Mullerian Hormone • Wolffian Hormone • Androgens

  4. Which of the following does NOT originate from Wolffian tissue? • Epididymis • Vas Deferens • Prostate • Glans • All of the above are Wolffian structures

  5. Berthold’s Capons suggested • Sex-specific morphology is dependent on hormone levels in development • Sex-specific behavior is dependent on hormone levels in development • Organization of the brain is sex-specific • All of the above • Only 1 and 2 above

  6. Which of the following is NOT supported by evidence? • Sexual identity is a biological trait • Brain organization is affected by hormones • Sexual behavior is affected by hormones • Sexual orientation is a behavioral choice • All of the above are supported by evidence

  7. Skeletal Muscle • “Striated” muscle (not “smooth” Cardiac) • Responsible for voluntary movements • Made up of many individual muscle fibers • Fibers originate during development from the fusion of cells in the mesoderm • Because of this cell fusion, muscle fibers are “multinucleated” (they contain more than one nucleus) • Innervated by the Alpha Motor Neuron

  8. The Motor Unit A single a-motor neuron and all the muscle fibers it innervates The set of all a-motor neurons innervating a muscle is called a Motor Neuron Pool

  9. Alpha Motor Neurons • “Final Common Path” for all movement • Cell bodies lie in the ventral horn of the spinal cord • Axons leave the spinal cord via the ventral root • Innervate skeletal muscle • Neurotransmitter is ACh

  10. Sensory nerve fibers > Organization of lower motor neuron cell bodies Dorsal Root > Ventral Root

  11. Lower motor neuron cell bodies are somatotopically organized

  12. Three types of Motor Units Start of muscle contraction

  13. Three types of Motor Units

  14. Motor unit recruitment

  15. Control of contraction magnitude • Rate of firing of Alpha Motor Neuron • Recruitment of additional motor units for the same muscle

  16. Graded muscle contraction by temporal summation of action potentials

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