Question

A) Write short notes.
1) Reflex action
2) Root pressure
3) Human brain
4) Transpiration​

Answer 1

Answer:

1 ) Automatic response to stimulus

Answer 2

Explanation:

1)The whole mechanism of reflex action occurs in such a fashion that there is no conscious control of the brain. Stimulation occurs through the peripheral nervous system and the response to this peripheral nerve stimulation is involuntary. In a reflex action, the spinal cord along with the brain stem is responsible for the reflex movements.

2)Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day. When transpiration is high, xylem sap is usually under tension, rather than under pressure, due to transpirational pull. At night in some plants, root pressure causes guttation or exudation of drops of xylem sap from the tips or edges of leaves. Root pressure is studied by removing the shoot of a plant near the soil level. Xylem sap will exude from the cut stem for hours or days due to root pressure. If a pressure gauge is attached to the cut stem, the root pressure can be measured.

3)The brain is one of the largest and most complex organs in the human body.

It is made up of more than 100 billion nerves that communicate in trillions of connections called synapses.

The brain is made up of many specialized areas that work together:

• The cortex is the outermost layer of brain cells. Thinking and voluntary movements begin in the cortex.

• The brain stem is between the spinal cord and the rest of the brain. Basic functions like breathing and sleep are controlled here.

• The basal ganglia are a cluster of structures in the center of the brain. The basal ganglia coordinate messages between multiple other brain areas.

4)Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism. The remaining 97–99.5% is lost by transpiration and guttation.[1] Leaf surfaces are dotted with pores called stomata, and in most plants they are more numerous on the undersides of the foliage. The stomata are bordered by guard cells and their stomatal accessory cells (together known as stomatal complex) that open and close the pore.Transpiration occurs through the stomatal apertures, and can be thought of as a necessary "cost" associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis. Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients and water from roots to shoots. Two major factors influence the rate of water flow from the soil to the roots: the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil. Both of these factors influence the rate of bulk flow of water moving from the roots to the stomatal pores in the leaves via the xylem.