The Central Nervous System MBBS Notes | EduRev

 Page 1


Chapter 8 
The Central Nervous System 
Page 2


Chapter 8 
The Central Nervous System 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
CNS 
? Consists of: 
? Brain. 
? Spinal cord. 
? Receives input from 
sensory neurons. 
? Directs activity of motor 
neurons. 
? Association neurons 
maintain homeostasis in 
the internal 
environment. 
Page 3


Chapter 8 
The Central Nervous System 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
CNS 
? Consists of: 
? Brain. 
? Spinal cord. 
? Receives input from 
sensory neurons. 
? Directs activity of motor 
neurons. 
? Association neurons 
maintain homeostasis in 
the internal 
environment. 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
Embryonic Development 
? Groove appears in ectoderm to fuse to form neural tube by 
20
th
 day after conception.  Neural tube eventually forms the 
CNS. 
? During 5
th
 week, modified: 
? Forebrain: telencephalon and diencephalon. 
? Midbrain: unchanged. 
? Hindbrain: metencephalon and myelencephalon. 
? Part of ectoderm where fusion occurs becomes neural crest. 
? Neural crest forms ganglia of PNS. 
Page 4


Chapter 8 
The Central Nervous System 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
CNS 
? Consists of: 
? Brain. 
? Spinal cord. 
? Receives input from 
sensory neurons. 
? Directs activity of motor 
neurons. 
? Association neurons 
maintain homeostasis in 
the internal 
environment. 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
Embryonic Development 
? Groove appears in ectoderm to fuse to form neural tube by 
20
th
 day after conception.  Neural tube eventually forms the 
CNS. 
? During 5
th
 week, modified: 
? Forebrain: telencephalon and diencephalon. 
? Midbrain: unchanged. 
? Hindbrain: metencephalon and myelencephalon. 
? Part of ectoderm where fusion occurs becomes neural crest. 
? Neural crest forms ganglia of PNS. 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
Embryonic Development (continued) 
Page 5


Chapter 8 
The Central Nervous System 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
CNS 
? Consists of: 
? Brain. 
? Spinal cord. 
? Receives input from 
sensory neurons. 
? Directs activity of motor 
neurons. 
? Association neurons 
maintain homeostasis in 
the internal 
environment. 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
Embryonic Development 
? Groove appears in ectoderm to fuse to form neural tube by 
20
th
 day after conception.  Neural tube eventually forms the 
CNS. 
? During 5
th
 week, modified: 
? Forebrain: telencephalon and diencephalon. 
? Midbrain: unchanged. 
? Hindbrain: metencephalon and myelencephalon. 
? Part of ectoderm where fusion occurs becomes neural crest. 
? Neural crest forms ganglia of PNS. 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
Embryonic Development (continued) 
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 
Embryonic Development (continued) 
? Telencephalon grows disproportionately 
forming 2 the hemispheres of the cerebrum. 
? Ventricles and central canal become filled with 
cerebral spinal fluid (CSF). 
? CNS composed of gray and white matter. 
? Gray matter consists of neuron cell bodies and 
dendrites. 
? White matter (myelin) consists of axon tracts.