write the notes 1)root pressure 2)transpiration 3)nerve cell 4)human brain 5)reflex action
Answers
1.Root pressure is the transverse osmotic pressure within the cells of root system that causes sap to rise through a plant stem to the leaves. It occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low at day time.
2. Transpiration is the process of movement of water through a plant and its evaporation from aerial parts,such as leaves,stems and flowers. Leaves surfaces are dotted with pores called as stomata, and in most plants they are more numerous on the undersides of the foliage.
3. Nerve cells carry signals from sense organs to the spinal cord and brain. The signals passes through neurons via synapses. Synapses are microscopic voids between cells where chemicals are released from the axon terminal of one cell to specialized chemical receptors on the dendrites of the receiving cell.
4. The brain stem is at the back of the brain (actually underneath it in humans). It joins rest of the brain with spinal cord. It has lots of different parts that controls different jobs in the body:for instance, the brain stem controls breathing, heartbeat, sneezing, eye blinking and swallowing.
5. Reflex action is a spontaneous, automatic and mechanical response to stimulus or sudden action to something in the environment.