Q.Draw labelled diagrams of the following:

Since these are diagrams, here are the parts that must be clearly shown and labelled in each.

(a) Neuron — draw a large cell body with fibres, and label:

• Cell body (cyton) — with cytoplasm, nucleus and the granular Nissl's granules.
• Dendrites — the short, repeatedly branching fibres projecting from the cell body (carry impulses towards it).
• Axon — the single long fibre.
• Myelin sheath — the covering formed by Schwann cells around the axon.
• Nodes of Ranvier — the gaps between adjacent myelin segments.
• Synaptic knobs at the branched axon ending, containing synaptic vesicles.

(b) Brain — draw the brain in side view and label the three divisions and their parts:

• Forebrain — cerebrum (with cerebral cortex), thalamus, hypothalamus; and the corpus callosum joining the hemispheres.
• Midbrain — with the corpora quadrigemina. …

(a) Neuron

A neuron is the structural and functional unit of the neural system, built from three major parts. Draw the cell in the centre with fibres extending from it, and label:

• Cell body (cyton) — the enlarged central portion holding the cytoplasm, the nucleus and the usual cell organelles, along with characteristic granular structures called Nissl's granules.
• Dendrites — the short fibres that branch repeatedly and project out from the cell body; they also contain Nissl's granules and carry impulses towards the cell body.
• Axon — the single long fibre leaving the cell body, whose far end is branched. Label the following features along and at the end of the axon:
  • Myelin sheath — the covering formed by Schwann cells wrapped around a myelinated axon.
  • Nodes of Ranvier — the gaps between two adjacent segments of the myelin sheath.
  • Synaptic knobs — the bulb-like swellings at the ends of the axon branches, containing synaptic vesicles that hold neurotransmitters.

(b) Brain

Draw the brain in side (longitudinal) view so that all three divisions can be seen, and label:

• Forebrain
  • Cerebrum — the large, folded upper part; you may mark its outer cerebral cortex.
  • Corpus callosum — the band of fibres joining the two cerebral hemispheres.
  • Thalamus — the relay centre around which the cerebrum wraps.
  • Hypothalamus — lying at the base of the thalamus.
• Midbrain …