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
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