November 26, 2015

Senior Intermediate Zoology 4 Marks Questions from Chapters 3 and 4

Q: Describe the structure of synovial joint with a neat labelled diagram.

A: i. A typical synovial joint is enclosed by a double layered synovial capsule. Outer layer of synovial capsule is continuous with periosteum and also contains ligaments. Inner layer is known as synovial membrane.
ii. Tips of bones that are enclosed by synovial capsule are covered by a layer of hyaline cartilage.
iii. The cavity enclosed by synovial capsule is known as synovial cavity and is filled with synovial fluid secreted by the synovial membrane.
iv. Synovial fluid acts as a lubricant and allows free movement of bones at the joint.
v. Synovial joints are movable joints.

Q: Give an account of retina of human eye.
A: a. Retina is also known as nervous tunic.
b. It is the inner layer of the eye ball. Its non visual part is formed by pigmented epithelium and visual part by neurons.
c. The neurons are arranged in three layers, namely, photoreceptor layer (rods and cones), bipolar layer and ganglion cell layer.
d. The centre of posterior part of retina is known as yellow spot and the depression present in the centre of yellow spot is known as fovea centralis. It is responsible for sharp and central vision.
e. All axons of ganglion cells exit the eye ball as optic nerve and it ends in the visual cortex of occipital lobe of brain.
f. The point where optic nerve exits the eye ball is known as blind spot (no vision part).
g. When light rays are focussed on retina, they generate impulses in rods and cones. Light induces the dissociation of photo pigments. As a result, action potentials develop in ganglion cells and are transmitted to the brain through the optic nerve, where the images are processed and the image is formed on retina.

Q: What is Cori cycle? Explain the process.
A: During rapid contractions, lactic acid is formed in the muscle. Major part of it is transported to the liver by blood, where it is converted into pyruvic acid and then glucose by gluconeogenesis. This glucose is again transported to the muscle by the blood for use of the muscle. These cyclical events between muscle and liver constitute Cori cycle.

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