Unit 6 explanation

Unit VI – Nervous System, Sense Organs & Endocrinology

1. Nervous System in Vertebrates

• Basic Plan: CNS (brain & spinal cord), PNS (cranial & spinal nerves), ANS (sympathetic & parasympathetic).
• Comparative Brain:
  • Fishes – small forebrain, large midbrain.
  • Amphibians – olfactory lobes well developed, small cerebellum.
  • Reptiles – enlarged forebrain, cerebral hemispheres begin.
  • Birds – large cerebellum, moderate hemispheres.
  • Mammals – highly developed neocortex.
• Spinal cord: dorsal, hollow, grey inside, white outside, dorsal & ventral roots.

2. Sense Organs

• Types: Eye (vision), Ear (hearing/balance), Olfactory (smell), Gustatory (taste), Tactile (skin).
• Comparative Eye:
  • Fishes – spherical lens.
  • Amphibians – dual focus, nictitating membrane.
  • Reptiles – eyelids well developed.
  • Birds – pecten present.
  • Mammals – binocular vision in primates.
• Comparative Ear:
  • Fishes – internal ear only.
  • Amphibians – tympanum first appears.
  • Reptiles – tympanum + ossicle.
  • Birds – one ossicle (columella).
  • Mammals – three ossicles (malleus, incus, stapes).

3. Endocrine Glands in Vertebrates

• Pituitary – master gland (GH, FSH, LH, TSH, ACTH).
• Thyroid – thyroxine, metabolism.
• Parathyroid – calcium balance.
• Pancreas – insulin & glucagon.
• Adrenal – adrenaline, corticosteroids.
• Gonads – testosterone, estrogen, progesterone.
• Comparative: simpler in lower vertebrates, neuroendocrine integration in mammals.

Exam-Oriented Notes

Long Answers:

• Comparative brain of vertebrates
• Comparative account of eye/ear
• Endocrine glands & hormones (with disorders)

Short Answers:

• Sympathetic vs parasympathetic system
• Pituitary hormones
• Structure of mammalian eye/ear

Very Short:

• Ossicles of mammalian ear
• Pecten in birds
• One hormone of pancreas