topic 7 - nervous system

• Nervous System Subdivisions


  • Central nervous system (CNS)
  • Brain
  • Spinal cord
  • Peripheral nervous system (PNS)
  • Cranial nerves
  • Spinal nerves
  • Ganglia
• CNS and PNS General Functions


  • Sensory Input: Receptors collect information, Detect changes (internal/external), Pass information to CNS
  • Integration: Processing and evaluating information, CNS determines response
  • Motor Output: Responding to information, CNS initiates nerve impulses to effectors
• Nervous System Cells


  • Neurons (nerve cells)
  • Glial cells
• Neurons


  Basic structural unit of the nervous system, Conduct nerve impulses, High metabolic rate, Extreme longevity, Mostly non-mitotic, All have cell body and one or more processes
• Structures in a Typical Neuron

  • Cell body: biosynthetic center
  • Dendrites: short processes branch from cell body, Receive nerve impulses
  • Axons transmit nerve impulses to other cells
  • Axon hillock: axon connects to the cell body
• Glial Cells or Neuroglia Cells


  • Ependymal
  • Oligodendrocytes
  • Astrocytes
  • Microglial
  • Satellite cells
  • Schwann cells
• Glial Cells


  • Smaller, Mitotic, More of them, Protect and nourish neurons
• Astrocytes


  • Most abundant CNS neuroglia, Bind blood vessels to neurons, Helps form the blood brain barrier
• Microglial cells


  • Protective, immune response role, Become phagocytic macrophages that engulf microorganisms or neuronal debris
• Ependymal cells


  • Produces cerebrospinal fluid (CSF), Line central cavities of brain and spinal cord
• Oligodendrocytes


  • Generates myelin, to coat axons
• Satellite cells


  • Surround neuron cell bodies in PNS (similar role to astrocytes of CNS)
• Schwann cells


  • Form myelin sheaths around nerve fibers (insulation), Similar role to oligodendrocytes, Also helps regenerate fibers
• Nerve Structure


  Cable-like bundle of axons, Connective tissue: Epineurium, Perineurium, Endoneurium, Myelin sheath is within endoneurium
• The Human Brain


  • Cerebrum
  • Diencephalon
  • Brainstem
  • Cerebellum
• Cerebrum


  • Outer surface is wrinkled, Gyrus (Gyri): Folds, elevated ridges, Sulcus (Sulci): Depressions between folds, Fissure (Fissures): Deeper grooves, separating hemispheres
• Gray matter


  Cell bodies, dendrites, unmyelinated axons, Forms the cortex, Superficial brain surface
• White matter


  Myelinated axons, Deep to cortex
• Brain Protection


  • Cranial bones
  • Meninges (protective connective tissue): Dura mater, Arachnoid mater, Pia mater
  • Cerebrospinal fluid (CSF)
  • Blood-brain barrier
• Cranial Meninges


  • 3 layers: Dura mater, Arachnoid mater, Pia mater, Separate brain and bones, Protects blood vessels, Contains CSF (between arachnoid and pia mater)
• Cerebrospinal Fluid (CSF)


  Provides buoyancy for the brain, Protection, Transports nutrients and wastes, Produced in the ventricles by ependymal cells
• Ventricles of the Brain

  • Two lateral ventricles
  • Third ventricle (diencephalon)
  • Fourth ventricle (between pons and cerebellum)
• Blood Brain Barrier


  Prevents molecules from moving from blood to brain, Protects brain via tight junctions, Tight junctions ensure substances pass through, not around endothelial cells, Feet of astrocytes and smooth muscle- like pericytes surround endothelial cells, Help to promote tight junction formation in endothelial cells
• Cerebral Hemispheres


  • Cerebrum is the location of conscious thought processes and origin of intellectual functions, Surface is marked by sulci, gyri, and fissures, Left and right cerebral hemispheres, Longitudinal fissure, Corpus callosum: connects the two hemispheres
• Lobes of the Cerebrum

  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe
  • Insula
• Frontal lobe


  • Voluntary motor function, concentration, verbal communication, decision making, planning, and personality
• Parietal lobe


  • General sensory functions
• Temporal lobe


  • Hearing and smell
• Occipital lobe


  • Processes incoming visual information, Stores visual memories
• Insula


  • Taste, Conscious perception of visceral sensations
• Diencephalon


  • Thalamus
  • Hypothalamus
  • Epithalamus
• Thalamus


  • Paired oval masses, Relay point for processing of sensory info
• Hypothalamus


  • Inferior to the thalamus, Infundibulum attaches to pituitary gland, Master control of ANS + endocrine system, Regulates temperature + sleep-wake cycles, Control of emotional behavior, and food and H2O intake
• Epithalamus


  • Most dorsal portion, Pineal Gland: Projects posteriorly, Secretes melatonin
• Brainstem


  • Midbrain
  • Pons
  • Medulla oblongata
• Midbrain


  • Cerebral aqueduct- connects ventricles, Visual and Auditory reflex, Produces dopamine
• Pons


  • Relays info from cerebrum to cerebellum, Helps regulate breathing
• Medulla Oblongata


  • Inferior aspect of Brainstem, Blends into spinal cord, Helps maintain homeostasis, Autonomic nuclei: Cardiac center, Vasomotor center, Respiratory center, Other nuclei involved in coughing, sneezing, salivation, swallowing, gagging, and vomiting
• Cerebellum


  • Coordinates and fine-tunes skeletal muscle, subconsciously, Stores movement patterns, Equilibrium and posture, Receives proprioceptive (sensory) information, Monitors the position of each body joint and its muscle tone
• Cranial Nerves


  • 12 pairs of nerves originating directly in the brain innervate parts of the head region