 grows towards sunlight.
Conclusion: By the above experiment it is proved that roots grow towards gravity (earth) away from sun light.
Give an example to show how hormones can influence visible changes in your body.
What are the effects of hormones on human beings?
- Endocrine glands secrete chemical substances called Hormones directly into blood.
- Hormones act on the cells of other organs and increase or decrease the metabolism of carbohydrates, proteins and fats.
- The external features by which the males and females can be distinguished are called secondary sexual characters.
- Testosterone in males and estrogen in females promotes the development of secondary sexual characteristics.
- For example, if a dog chases us, our nervous system stimulate the adrenal glands to secrete more adrenaline hormone into our body.
- When we are afraid, the rate of heart beat increases, the breath rate will be faster, blood pressure increases, the hair on the body becomes errect.
- All these changes occur due to the production of Adrenaline hormone.
How does a neuron differ from an ordinary cell in structure? Write notes.
|Neuron (Nerve cell)||Ordinary cell|
|1. It is the longest cell in our body.||1. Generally cells are round or oval shaped.|
|2. It belongs to only nervous system.||2. These are the structural units of body.|
|3. Nerve cell has three parts: 1. Cyton 2. Axon 3. Dendrites||3. Commonly divided as 1. Cytoplasm and 2. Nucleoplasm|
|4. These cells carry impulses to brain and spinal cord.||4. Involve in metabolic activities.|
|5. These are not regenerated.||5. The cells have cell division and replace the death cells.|
|6. Nerve cells end with dendrites.||6. These cells do not have end points.|
|7. Some nerve cells are covered with lipid coat.||7. Generally these are covered with plasma membrane.|
|8. Nissl granules are special character of nerve cells.||8. These cells do not have Nissl granules.|
Is the structure of neuron suitable for transmission of impulses? Analyse.
- Yes. The structure of neuron is suitable for transmission of impulses.
- Neurons are the functional units which receive and process information and generate responses.
- Cell body is the centre for all the synthetic activity of the neuron.
- Dendrites arise from the cell body receive information from other neurons and carry this information to the cell body.
- The axon or nerve fibre gives out several branches that end in nerve terminals. These make connect with the dendrites or the axons of another neuron.
- Myelinated sheath prevents the leakage of electrical currents from axon. Myelinated axons conduct impulses much faster than unmyelinated axons.
Man is the most intelligent animal. What could be the fact that helped us to reach such a conclusion?
- Man is the most intelligent animal in animal kingdom.
- This is possible by well development of brain and its marvellous function.
- Human brain has abilities to learn from concepts.
- It understands, applies logic and reason.
- The brain also recognizes patterns and comprehends ideas.
- The human brain has ability in making plans, solving problems, making decisions and retaining information.
- Man is the only animal who uses language to communicate.
- Intelligence enables humans to experience and think.
- It has also consciousness and self-awareness.
The axon of nerve cell in hand is shorter than the axon of nerve cell in leg. Do you support this statement? Why?
- Yes, I support the above statement.
- The axon of nerve cell in hand is shorter than the axon of nerve cell in leg.
- The sciatic nerve is the large nerve in humans and animals. It begins in the lower back and runs through the buttock and lower limbs.
- Sciatic nerve present in the leg is the largest and widest single nerve in the human body. It measures about 1 mt in length.
- Usually the length of leg is more in size than hand. Hence the axon of nerve cell in hand is shorter than the axon of nerve cell in leg.
Organs respond to the external stimulus by a fraction of second. How do you feel about such controlling mechanism of human body?
- Organs 