Neural Control and Coordination Test - 13

Correct option: C

• Axons of neurons can be either myelinated or non-myelinated. 
• Myelin sheath is made up of proteins and fatty substances. 
• It allows electrical impulses to transmit quickly and efficiently along the nerve cells.

The axon is covered by a lipid-rich membrane, called myelin sheath. The myelin sheath is formed by Schwann cells and each Schwann cell covers a part of the axon.
Thus, the correct answer is option (A) Axon.

A neuron is the structural and functional unit of the nervous system. Neurons are similar to other cells in the human body in a number of ways, but there is one key difference between neurons and other cells. Neurons are specialized to transmit information throughout the body.
Thus, the correct answer is the option (C), 'Neurons'.

The cornea is the transparent layer of the eye located within otherwise opaque sclera. It serves to refract the light rays. Iris is the coloured part of the eye that controls the amount of light entering the eye by adjusting the size of the pupil, a hole shaped opening in the middle of the eye. Ciliary body and the attached suspensory ligament change the shape (flattened or round) of the lens through relaxation and contraction of ciliary muscles and thereby the focal length to focus on a distant and near object. Thus, the correct answer is option C.    

The cerebrum is the largest and most developmentally advanced part of the human brain. It is responsible for several higher functions, including higher intellectual function, speech, emotion, integration of sensory stimuli of all types, initiation of the final common pathways for movement, and fine control of movement.

A typical bird eye will respond to wavelengths from about 300 to 700 nm. Humans cannot perceive UV light directly because the lens of the eye blocks most light in the wavelength range of 300 - 400 nm. Another big difference between the tetrachromacy vision of humans and birds lies in the retina. The fovea, which is the area of the retina responsible for the precise vision of the details and where there is a big concentration of cones, form a lateral strip rather than a central area. Added to the fact that some birds can have two or even more fovea, birds have a lot more cones than humans and this consequently can visualise colours better than humans. Birds have photopigments, that are sensitive to four or five peak wavelengths. Because of this fact, they are much more sensitive to colours than humans.

The ciliary body is triangular in cross-section, and it encircles the inside of eye behind the coloured iris. It forms part of the middle uveal layer of the eye, that connects posteriorly with the choroid with the anteriorly with the iris. The ciliary body has two portions, the pars plicata at the front and the pars plana at the rear.
The ciliary body has two principal functions are;

• It produces and secretes aqueous humour essential to regulate the pressure within the eye.

• It contains muscles, that act on the crystalline lens via its zonular fibres, in concert with the elastic lens capsule, to change its shape and thus shift the focus of the eye from far to near.

The corpus callosum is a huge band of myelinated fibers, connects the two cerebral hemispheres. It is a flat bundle of neural fibers about 10 cm long beneath the cortex made up of white matter. Hence, the correct answer is option C.

• A retinal ganglion cell is a type of neuron located near the inner surface of the retina of the eye. 
• It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina amacrine cells.