evolution of vertebrate brain - sponges are only multicellular animals w/o nerves 

• cnidarians - have simplest nervous systems (nerve net)
  • no control/association
• flatworms - simplest animals w/ association in nervous system
  • bigger mass of nervous tissue (beginnings of brain) >> complex control
• interneurons/tracts added to brain as it evolved (interneurons - complex, high-level neurons found in brain/spinal cord)
• hindbrain (rhombencephalon) - extension of spinal cord
  • coordinates motor reflexes
  • cerebellum (“little cerebrum”) - controls balance, body position
  • pons - controls automatic functions, links cerebellum/medulla oblongata w/ other parts of brain
  • medulla oblongata - contains respiration, circulation
• midbrain (mesencephalon) - consists of mostly optic lobes that receive/process visual information
  • controls eye/ear reflex
• forebrain (prosencephalon) - processes most of sensory information
  • diencephalons - thalamus, hypothalamus
  • thalamus - relays info between spinal cord and cerebrum
  • hypothalamus - controls emotions, pituitary gland
  • cerebrum (telencephalon) - dominant part of mammalian brain
• ascending tracts - carry sensory info to brain
• descending tracts - carry impulses from brain to motor neurons

human forebrain - divided into 2 hemispheres connected by corpus callosum 

• each hemisphere receives info from opposite side
• cerebral cortex - layer of gray matter on outer surface of cerebrum
  • contains 10% of all neurons in brain
  • folded/wrinkled to increase surface area
  • primary motor cortex - right in front of central sulcus (crease), controls mov’t
  • primary somatosensory cortex - right behind central sulcus, receives info from sensory neurons of skin/muscles
  • auditory cortex - in temporal lobe
  • visual cortex - in occipital lobe
  • association cortex - used for higher mental activities
• basal ganglia - collections of cell bodies, dentrites that produce gray matter islands
  • receives info from ascending tracts, motor commands from cerebrum/cortex
  • sends info to spinal cord to control mov’t
  • damaged ganglia >> Parkinson's
• thalamus - main area of senses (especially pain)
  • receives visual, auditory, somatosensory info
  • relays info to occipital (visual), temporal (auditory), parietal (somatosensory) lobes
• hypothalamus - controls instinct
  • regulates body temperature, hunger, thirst, emotion
  • controls pituitary gland (regulates other endocrine glands)
• limbic system - responsible for emotional responses
  • includes hypothalamus, hippocampus (may control memories), amygdala

spinal cord - cable of neurons going from brain through backbone 

• protected by vertebral column and meninges (membrane layers that also cover the brain)
• inner zone (gray matter) - consists of interneuron, motor neuron, neuroglia cell bodies
  • unmyelinated cell bodies
• outer zone (white matter) - consists of sensory axons (in dorsal column) and motor axons (in ventral column)
  • myelinated axons
• controls reflexes (sudden involuntary muscle mov’t)
  • doesn’t require higher level processing of info
  • only uses a few neurons >> very fast
  • monosynaptic reflex arc - simplest reflex (like knee-jerk reflex), sensory nerve connects directly to motor neuron
  • most reflexes usually involve an interneuron between sensory/motor neurons
• regeneration - implanted nerve axons can’t penetrate spinal cord tissue
  • factor in spinal cord inhibits nerve growth
  • use of fibroblast growth factor shows limited improvement in neuron regeneration ability