Neural Control and Coordination

• Introduction

  • Definition of Coordination
  • Role of Neural System
  • Role of Endocrine System

• Neural System in Humans

  • Central Nervous System (CNS)
    • Brain
    • Spinal Cord
  • Peripheral Nervous System (PNS)
    • Cranial Nerves
    • Spinal Nerves
    • Nerve Fibers
      • Afferent Fibers (Sensory: Tissues to CNS)
      • Efferent Fibers (Motor: CNS to Tissues)
  • Divisions of PNS
    • Somatic Neural System (To skeletal muscles)
    • Autonomic Neural System (To involuntary organs/smooth muscles)
      • Sympathetic
      • Parasympathetic

• Neuron as Structural and Functional Unit

  • Cell Body (Soma)
    • Cytoplasm
    • Nissl's Granules
  • Dendrites (Receive impulses)
  • Axon (Transmit impulses away)
    • Schwann Cells
    • Myelin Sheath
    • Nodes of Ranvier
  • Types of Neurons
    • Multiplex/Multipolar (1 axon, 2+ dendrites - cerebral cortex)
    • Bipolar (1 axon, 1 dendrite - retina)
    • Unipolar (1 axon only - embryonic stage)

• Generation and Conduction of Nerve Impulse

  • Polarized State (Resting Membrane Potential)
    • High $K^+$ and negative proteins inside
    • High $Na^+$ outside
    • Maintained by $Na^+-K^+$ pump (Active transport: 3 $Na^+$ out, 2 $K^+$ in)
  • Depolarized State (Action Potential)
    • Stimulus applied
    • Influx of $Na^+$ ions
    • Inside becomes positively charged
  • Repolarization
    • Efflux of $K^+$ ions
    • Restoration of resting potential
  • Saltatory Conduction
    • Impulse jumps from node to node in myelinated axons (faster)

• Synapse and Synaptic Transmission

  • Types of Synapses
    • Electrical Synapse (Direct current flow, rare in humans, fast)
    • Chemical Synapse (Uses Neurotransmitters, most common)
  • Mechanism at Chemical Synapse
    • Impulse reaches axon terminal
    • Synaptic Vesicles move and fuse with membrane
    • Release of Neurotransmitter (e.g., Acetylcholine) into Synaptic Cleft
    • Binds to receptors on Post-synaptic membrane
    • Opens ion channels to generate new potential

• Human Central Nervous System

  • Brain (Protected by Cranium and Meninges: Dura mater, Arachnoid, Pia mater)
    • Forebrain
      • Cerebrum (Center of intelligence, memory, motor/sensory areas)
      • Thalamus (Relay station)
      • Hypothalamus (Controls body temp, urge for eating/drinking, secretes hormones)
    • Midbrain
      • Located between forebrain and hindbrain
      • Corpora quadrigemina (Visual and auditory reflexes)
    • Hindbrain
      • Pons (Fiber tracts interconnecting brain regions)
      • Cerebellum (Maintains posture and balance)
      • Medulla Oblongata (Controls respiration, cardiovascular reflexes, gastric secretions)
    • Limbic System
      • Formed by amygdala, hippocampus, etc.
      • Regulates sexual behavior, emotion, and motivation

• Reflex Action and Reflex Arc

  • Definition of Reflex Action (Involuntary, spontaneous response to a stimulus)
  • Reflex Arc Components
    • 1. Receptor (Perceives stimulus)
    • 2. Sensory (Afferent) Neuron (Carries signal to CNS)
    • 3. Interneuron / CNS (Processing)
    • 4. Motor (Efferent) Neuron (Carries signal to effector)
    • 5. Effector (Muscle/Gland showing response)
  • Example: Knee-jerk reflex, withdrawal of hand from hot object

• Sensory Reception and Processing

  • Eye (Photoreceptor)
    • Layers: Sclera, Choroid, Retina
    • Photoreceptor Cells: Rods (Twilight vision, Rhodopsin) and Cones (Daylight/color vision, Photopsins)
    • Fovea (Point of greatest visual acuity)
    • Blind Spot (Optic nerves leave eye, no photoreceptors)
  • Ear (Phono-equilibrium receptor)
    • Outer Ear (Pinna, Auditory meatus, Tympanic membrane)
    • Middle Ear (Ear ossicles: Malleus, Incus, Stapes; Eustachian tube)
    • Inner Ear (Labyrinth: Cochlea for hearing, Vestibular apparatus for body balance)
      • Organ of Corti (Contains hair cells acting as auditory receptors)