Nervous Systems Brain Development 2007-2008

Central nervous system Peripheral nervous system Spinal cord Sensory pathways Motor pathways Brain Sympathetic arousal & energy production “fight or flight” Parasympathetic calming & back to maintenance “rest & digest” Somatic (voluntary) nervous system Autonomic (involuntary) nervous system Sympathetic division Parasympathetic division

Types of neurons sensory neuron interneuron “associative” motor neuron cell body sensory neuron cell body axon interneuron “associative” dendrites dendrites cell body motor neuron

Cephalization = Brain evolution Cephalization = clustering of neurons in “brain” at front (anterior) end of bilaterally symmetrical animals  where sense organs are Cnidarian nerve net Flatworm Platyhelminthes nerve cords associative neurons Echinoderm radial nerve nerve ribs Simplest nervous system no control of complex actions More organization but still based on nerve nets; supports more complex movement Simplest, defined central nervous system more complex muscle control

Cephalization = Brain evolution increase in interneurons in brain region brain ventral nerve cords Arthropod Earthworm central nervous system peripheral nerves Mollusk brain giant axon More complex brains connected to all other parts of body by peripheral nerves More complex brains in predators most sophisticated invertebrate nervous system Further brain development ganglia = neuron clusters along CNS

Evolution of vertebrate brain Shark Frog Cat Bird Human Spinal cord Hind: Medulla oblongata Optic tectum Hind: Cerebellum Midbrain Fore: Cerebrum Olfactory tract Crocodile forebrain forebrain dominant cerebrum hindbrain forebrain

Human brain

Functional divisions of brain Hindbrain evolutionary older structures of the brain regulate essential autonomic & integrative functions brainstem pons medulla oblongata midbrain cerebellum thalamus, hypothalamus

Brainstem The “lower brain” Functions medulla oblongata pons midbrain homeostasis coordination of movement conduction of impulses to higher brain centers

Medulla oblongata & Pons Controls autonomic homeostatic functions heart & blood vessel activity breathing swallowing vomiting digestion Relays information to & from higher brain centers

Midbrain Involved in the integration of sensory information regulation of visual reflexes regulation of auditory reflexes

Reticular Formation Sleep & wakefulness produces patterns of electrical activity in the brain recorded as an ElectroEncephaloGram (EEG) most dreaming during REM (rapid eye movement) sleep

Cerebrum Most highly evolved structure of mammalian brain Cerebrum divided hemispheres left = right side of body right = left side of body Corpus callosum major connection between 2 hemispheres

Lateralization of Brain Function Left hemisphere language, math, logic operations, processing of serial sequences of information, visual & auditory details detailed activities required for motor control Right hemisphere pattern recognition, spatial relationships, non-verbal ideation, emotional processing, parallel processing of information

Cerebrum specialization Regions of the cerebrum are specialized for different functions Lobes frontal temporal occipital parietal

Limbic system Mediates basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory Amygdala involved in recognizing emotional content of facial expression

Simplest Nerve Circuit Reflex, or automatic response rapid response automated signal only goes to spinal cord no higher level processing adaptive value essential actions don’t need to think or make decisions about blinking balance pupil dilation startle

Eye Blink or Pain Withdrawal Reflex Gray matter Interneuron Stimulus White matter Receptor in skin Sensory neuron Motor neuron Spinal cord Effector (muscle)

Review of nervous system With Mr.A cerebrum cerebellum spinal cord cervical nerves thoracic lumbar femoral nerve sciatic tibial Review of nervous system With Mr.A 2007-2008