Question

Write short notes on the following:

(a) Neural coordination

(b) Forebrain

(c) Midbrain

(d) Hindbrain

(e) Retina

(f) Ear ossicles

(g) Cochlea

(h) Organ of Corti

(i) Synapse

Answer 1

(a) Neural coordination: The nervous system provides quick coordination of various parts of the body through electric impulses. These impulses are short lived but quick.

(b) Forebrain consists of the cerebrum, cerebral hemispheres, olfactory lobes and diencephalon (thalamus and hypothalamus). It helps in the interpretation of stimulus received by effector organs.

(c) Midbrain consists of tectum (visual and auditory stimuli) and tegmentum (contains nuclei for pain modulation, motor coordination and movement planning). It helps in the relay of impulse from effector organ to the forebrain.

(d) Pons, cerebellum and medulla together form the hindbrain. It helps to maintain the balance of body and body posture. It also has regulatory centres for controlling the involuntary actions.

(e) The retina is the innermost layer of the eyeball and contains photoreceptor rods and cones.

(f) Ear ossicles: Three small bones present between the tympanic membrane and oval window are collectively referred to as ossicles, they are namely malleus, incus and stapes. It increases the amplification of sound waves.

(g) Cochlea: Cochlea is a spiral hollow structure containing three fluid-filled canals. Organ of corti is located in middle cochlear canal and has hair cells (mechanoreceptors) on its basilar membrane. Thus, cochlea houses sensory system for hearing only and is not associated with balancing.

(h) Organ of corti: Organ of corti is located in middle cochlear canal and has hair cells (mechanoreceptors) on its basilar membrane. It generates the auditory impulse which is carried by auditory nerves.

(i) Synapse: Two neurons are never physically connected to each other and synapse is the region of close proximity between two neurons where information from one neuron is transmitted to the next one.