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The Central Nervous System

The Central Nervous System. Brain and spinal cord. Features of the CNS. Sensory input Motor output Association neurons connect the two. Nervous tissue develops from ectoderm. Sequence of brain development. Ventricles and central canal are filled with CSF.

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The Central Nervous System

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  1. The Central Nervous System Brain and spinal cord

  2. Features of the CNS • Sensory input • Motor output • Association neurons connect the two

  3. Nervous tissue develops from ectoderm

  4. Sequence of brain development

  5. Ventricles and central canal are filled with CSF

  6. Most of the brain mass is the cerebrum (and is highly organized)

  7. Cerebral lobes are paired

  8. Mapping the homunculus

  9. Basal nuclei control voluntary movements • From motor cortex to putamen (glutamate) • From putamen to other basal nuclei (inhibitory signal, GABA)

  10. The motor circuit includes excitatory and inhibitory signals

  11. Right and left hemispheres are not symmetrical in function

  12. Aphasias informed our knowledge of language function

  13. Structure and function of the limbic system (and diencephalon) • Aggression • Fear • Satiety • Sex drive • Reward and punishment

  14. Organization of short-term and long-term memory Glutamate and GABA are key (and regulation of Na and Ca ions)

  15. More about the organization of memory • Amygdala intensifies emotional memories • Stress can impair memory retrieval by hippocampus and prefrontal cortex • Prefrontal cortex connects with many regions of the brain

  16. The chemical basis of learning? • LTP (long-term potentiation) occurs at synapses • GABA is normally inhibitor • A “retrograde messenger” can lessen the effect of GABA • Synapses become more excitable

  17. The diencephalon • Thalamus • Relay center for sensory input (except smell) • Epithalamus • Choroid plexus, pineal gland • Hypothalamus • Regulates hunger, thirst, body temperature, limbic system, endocrine system, autonomic system… • Pituitary gland • Major regulator of endocrine system

  18. Hypothalamus is regulated by higher brain centers

  19. Midbrain is between the diencephalon and pons • Relexes and relay centers (corpora quadrigemina) • Nuclei control motor coordination • Two systems of dopaminergic neurons • Mesolimbic system to forebrain (behavior) • Nigrostriatal from basal nuclei (coordination)

  20. Midbrain is between the diencephalon and pons • Relexes and relay centers (corpora quadrigemina) • Nuclei control motor coordination • Two systems of dopaminergic neurons • Mesolimbic system to forebrain (behavior) • Nigrostriatal from basal nuclei (coordination)

  21. Metencephalon- pon and cerebellum • Pons • Nuclei for cranial nerves • Respiratory centers • Cerebellum • Connects with cerebrum through thalamus • Proprioreceptors • Mostly inhibitory (Purkinje cells)

  22. Myencephalon- medulla oblongata • All communicaiton between spinal cord and brain passes through here • Nuclei for motor control • “vital centers” • Vasomotor (constriction, dilaiton) • Cardiac control • Respiratory center

  23. Reticular Activating Center (RAS) • Ascends from pons to midbrain • Stimulatory neurotransmitters (NTs) are released in thalamus and other parts of brain • Ventrolateral preoptic nucleus releases NTs that permit sleep • Still other NTs promote arousal

  24. Spinal cord tracts Ascending (sensory) Descending (motor) Refer to tables 8.4 and 8.5

  25. Ascending tracts

  26. Descending tracts • Corticospinal (pyramidal) tracts from precentral gyrus to spinal cord • Reticulospinal (extrapyramidal) tracts controlled by midbrain, descend from brain stem; multiple synapses

  27. Higher motor neuron control: effect of cerebellum is indirect

  28. The Peripheral nervous system Cranial and spinal nerves Cell bodies outside the CNS

  29. Cranial nerves • See Table 8.6 for review • Mostly associated with special senses or skeletal muscles of the head and neck • Named according to position and function • Most are mixed nerves

  30. Spinal nerves • 31 pairs • All mixed, but separate into sensory (dorsal root) and motor (ventral root) • Dorsal root ganglion contains cell bodies of sensory neurons • Motor neurons: cell bodies is in spinal cord (motor) or ganglia (autonomic)

  31. Reflex arcs • Simple reflexes do not involve brain • Simplest reflexes involve a single synapse • Include somatic and autonomic reflexes

  32. Summary • Central nervous system consists of brain and spinal cord • Conscious and unconscious functions are controlled by different parts of the brain • “Lower” parts of the brain include relay centers • Spinal cord tracts carry information to and from the brain • Cranial and spinal nerves connect the periphery to the central nervous system

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