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Lecture 18

01:119:116 Lecture 18: Lecture 18 - Nervous System Organization

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Biological Sciences
Dr.Christy Beal

Lecture 18 - Nervous System Organization I. Nervous System Organization A. Cnidarians ➢ No central control, nerve net ➢ Simplest animals with nervous systems ○ Fig 49.2 B. Echinoderms (Sea Star) ➢ Nerve ring ➢ Central control structure signals muscles C. Bilateria ➢ Lots of variation ➢ Planarian - simple CNS, brain, eyespot, ladder type nervous system ➢ Annelids/Arthropods - more complex, brain, ganglia D. Vertebrates ➢ Brain and spinal cord = CNS ➢ Nerves and ganglia = PNS E. Nervous System & Lifestyle ➢ Chiton - slow → simple ➢ Squid - fast → complex II. Glial Cells (Glia) A. Types of Adult Glial Cells ➢ 5 types: Ependymal, Astrocytes, & Microglia = support ➢ Oligodendrocytes & Schwann cells are myelinated ○ (like insulation around the cells) ○ Fig 49.3 B. Radial Glia ➢ Forms tracks in developing embryo ➢ Glial cells in adult develop from radial glia in embryo ➢ Zika has been linked to death of neural progenitor cells like radial glia → microcephaly III. Central Nervous System (CNS) Fig 49.5 A. Brain ➢ Brain - central control organ ➢ Structure: ○ Ventricles - cavities ○ Grey matter surrounds white matter ○ Cerebrospinal fluid B. Spinal Cord ➢ Link between the brain and rest of nerve system ➢ Structure: ○ Small central canal w/ fluid ○ Gray matter surrounds canal ○ White matter surrounds gray ➢ Functions: ○ Transmits impulses from/to brain ○ Reflex actions → rapid & involuntary ■ Knee-jerk reaction ● Quad stretches → don’t fall! ■ Fig 49.7 IV. Peripheral Nervous System A. Sensory Receptors ➢ Transmits info to and from CNS ➢ Sensory receptors → detect stimuli ○ Visual, auditory, etc. B. Nerves ➢ Cranial Nerves ○ Hind part of brain ○ Head & upper body ➢ Spinal Nerves ○ Origin in spinal cord ○ Entire body C. Two Functional Components of PNS ➢ Afferent (sensory) (Arrives at CNS) ○ Receptors not effectors ➢ Visceral: ○ You are not aware of ■ Ex: Blood pressure ➢ Soma
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