Video 2: Basic Anatomy Continued

Terms and Spatial Orientation

  • Superficial: toward the surface
  • Deep: away from the surface
  • Cranial: toward the head
  • Rostral: toward the nose or beak
  • Caudal: toward the tail

Yet More Terms

  • Fossa: depression, groove
  • Head: proximal portion of a bone
  • Insertion: portion of muscle that is relatively mobile
  • Origin: portion of a muscle that is relatively immobile
  • Joint: articulation
  • Ligament: fibrous connective tissue connecting bones and cartilage
  • Muscle: contractile tissue
  • Neck: constricted portion of a structure
  • Organ: aggregates of tissues with functional unity

Muscles and Fiber Types

  • Are made up of fibers; fibers can be fast and slow twitch
  • Fast twitch muscle fibers:
    • Contract quickly
    • Are for fine movement
    • Fatigue easily
  • Slow twitch muscle fibers:
    • Are for larger movements
    • Exert greater force
    • Move more slowly
    • Have greater endurance
    • Antigravity muscles of trunk

Muscle Function

  • Muscle can only do one thing: contract
  • Contraction brings two points closer together
  • Longer muscles can contract farther than short muscles
  • Muscles with more fibers can exert more force of contraction

Four Critical Definitions Relative To Muscles

  • Origin: The point of attachment of a muscle that is relatively immobile during contraction
  • Insertion: The point of attachment of a muscle that is relatively mobile during contraction
  • Agonist: The muscle that performs the intended action (prime mover)
  • Antagonist: A muscle that opposes the intended action

Nervous Tissue

  • Neurons: Transfer information; communication
  • Glial cells: Nutrient transfer; blood brain barrier; neurotransmitter re-uptake; waste removal; structural support; long term memory

This Is An Awesome System

  • Cerebral cortex contains between 20 \,text{to} \,25 \,text{billion} neurons
  • Each cm^3 has about 44 \,text{million} neurons
  • Because of tremendous density and connectivity, the total number of possible states of your brain is greater than the number of molecules in the universe!
  • Source note: Images from Seikel, Konstantopoulos & Drumright, 2018

Anatomical Divisions of the Nervous System (NS)

  • System of controls
  • Divided into two major components:
    • Central nervous system (CNS)
    • Cerebral cortex
    • Cerebellum
    • Diencephalon
    • Brainstem
    • Spinal cord
    • Peripheral nervous system (PNS)
    • Cranial nerves
    • Spinal nerves
  • Notes: Some CNS structures vs PNS structures are shown in Seikel, Konstantopoulos & Drumright (2018)

Functional Divisions Of Nervous System

  • Autonomic nervous system (ANS)
  • Somatic nervous system
    • Motor control system
    • Sensory systems

Autonomic Nervous System (ANS)

  • Sympathetic nervous system: excitatory response to stimulation
  • Parasympathetic nervous system: damping response following excitation
    • Energy saving; heart deceleration, etc.

Motor Activation of Muscle

  • Impulse to activate muscle arises at the motor strip of the cerebral cortex
  • Head and face region for muscles of speech
  • More dorsal regions for trunk, arms, leg muscles
  • Source: Seikel, Konstantopoulos & Drumright (2018)

Sensorimotor Homunculus

  • Concept: The brain contains somatotopic maps for both motor and somatosensory representations
  • Motor strip and somatosensory strip show disproportionate representation for different body parts (e.g., face, lips, hands)
  • The illustrated “homunculus” demonstrates how cortical space is allocated to control and perceive different body regions
  • (Note: The slide content is a garbled image caption but the key idea is the somatotopic organization of motor and somatosensory cortices)

End of Video 2

  • Knowledge Check Quiz 2: you can retake; the most recent score by the deadline counts
  • Attendance and participation in in-class exercises on Tuesdays are important for the grade

Additional Connections and Context

  • All definitions (origin, insertion, agonist, antagonist) are foundational for understanding muscle mechanics and biomechanics
  • The differentiation between CNS and PNS, plus the autonomic vs somatic divisions, provides the framework for how voluntary and involuntary actions are coordinated
  • The sensory and motor homunculi illustrate the principle of somatotopic organization, a recurring theme in neuroanatomy and neurolinguistics
  • The material is drawn from Seikel, Konstantopoulos & Drumright (2018) and is aligned with Dr. Erin O’Bryan’s CSD 301 Anatomy and Physiology course

Quick Reference Equations and Numerical Notes

  • Neuron counts:
    • The cerebral cortex contains between 20 ext{ to } 25 ext{ billion} neurons
    • Each ext{cm}^3 contains about 44 ext{ million} neurons
  • Conceptual scale: due to density and connectivity, the brain’s possible states exceed the total number of molecules in the universe