Science [2 Mark Questions]

Two main organs of our central nervous system are:

1. Brain and spinal cord.
2. Spinal cord sends the command to muscles to act without involving thinking process.
3. This phenomenon is known as reflex action.

Hormones are the substances produced by glands that are released into blood and travel through the body to other cells. The hormone is thyroxin and the purpose of the thyroid gland is to make, store, and release thyroid hormones into the blood.

Water harvesting refers to the process of storing the rain water for future use. This water can be stored in any tank or can. There are following type of system used in water harvesting process.

1. Setting rooftop water collecting units.
2. Digging a series of deep pits in the beds of rive.

Nastic movements: These are non-directional movements which are neither towards nor away from the stimulus.
Example: Drooping of leaves.
Curvature movements: In such movements plant organs move towards or away from the stimulus.
Example: Bending of shoot towards source of light (Phototropism) and movement of root away from the source of light (geotropism).

1. Gustatory receptors are located on the tongue. They help to detect taste.

The olfactory receptors are located in the nose. They help to detect smell.

2.  

1. Pineal gland.
2. Pituitary gland.
3. Thyroid gland.
4. Thymus.

Control and coordination of functioning of various systems is under the direct control of nervous system. It is the nervous system which governs the way a particular organ or organ system has to work. This control is achieved by a complex network of neurons which carry signals in the form of electric impulses; to and from the brain.The hormonal system, on the other hand, coordinates the functioning of nervous system. The hormonal system has somewhat indirect control on various functions. It tells a system to either slow down or pace; according to the situation.
Nervous and hormonal systems are complementary to each other. Thus, it can be said that nervous and hormonal system together perform the function of control and coordination in human beings.

Cytokinin are the hormones which induce cell division which is very much needed for young fruits and seeds. to support the growth and development cytokinins are present in higher concentrations. So fruits ripen easily and seeds give rise to plant lets.

When a nerve impulse reaches the muscle, the muscle fibre must move. Muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses. When this happens, new arrangements of these proteins give the muscle cells a shorter form.

Geotropism is the influence of gravity on plant growth or movement. Geotropism guides plant roots to grown downward, or if growing horizontally in shallow topsoil, to occasionally branch and send some roots vertically downward.

The folding of leaves of a sensitive plant is not a case of tropism (like thigmotropism) because in this case the direction of movement of leaves does not depend on the direction of stimulus (touch).

The movement of a plant part in response to an external stimulus in which the direction of response is not determined by the direction of stimulus is called nastic movement. Example: The folding up of the leaves of a sensitive plant on touching is an example of thigmonasty.

In stress situations adrenaline is released into the blood by adrenal glands. Its target organ is heart which as results heart rates increases so as to increase the supply of the oxygen to the muscles, blood to digestive system and skin is reduced and breathing rate increases. All these responses together prepare the body to face any stressful situation.

A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus (or a particular type of change in the environment). Example: Photoreceptors and Phonoreceptors.An effecter is the part of the body which can respond to the stimulus according to the instructions sent from the nervous system (spinal cord and brain). Example: Muscles and glands.

Tendrils are the thin, thread-like growths on the stems or leaves of climbing plants. The two types of tendrils are stem tendrils and leaf tendrils. The tendrils grow towards the things they happen to touch. This phenomenon is known as thigmotropism.

Photonasty	Thigmonasty
The non-directional movement of a plant part (usually petals of flowers) in response to light is called photonasty. Example: The opening and closing of petals of dandelion flowers in response to the intensity of light.	The non-directional movement of a plant part in response to the touch of an object is called thigmonasty. Example: In Mimosa pudica plant, the leaves fold up in response to touch.

1. Bending of stem towards light.
2. Folding up of leaves of a sensitive plant on touching.

The function of insulin hormone is to lower the blood sugar level (or blood glucose level). People having severe diabetes are treated by giving injections of insulin.

Receptors detect all the information from our environment. These receptors are located in our sense organs. In case any of the receptors do not work properly we will not be able to perceive that particular information.

The endocrine glands do not have ducts to secrete their hormones. They release hormones directly into the blood of a person and reach the concerned body part through the blood and act on it.

Auxin:

1. It is responsible for the photo-tropism and geotropism.
2. It promotes root initiation in callus and stem cutting.

1. A dandelion flower opens up in the morning in bright light. This phenomenon is known is positive photonasty.
2. At night, the dandelion flower closes and this phenomenon is known as negative photonasty.

Examples of reflex action are:

1. When light acts as a stimulus, the pupil of the eye changes in size.
2. Sudden blinking when an insect comes very near to the eyes.
3. Sudden jerky withdrawal of hand or leg when pricked by a pin.

The feedback mechanism regulates the timing and amount of hormone to be secreted, e.g. if a person has more sugar in his blood, it is detected by the cells of the pancreas. As a result, more insulin will be secreted to oxidise the sugar. As blood sugar level falls, insulin secretion is reduced.

The movement of leaves of the sensitive plant, Mimosa pudica or "touch me not", occurs in response to touch or contact stimuli. This movement is independent of growth. The movement of shoot towards light is known as phototropism. This type of movement is directional and is growth dependent.

Autonomic nervous system means self governing nervous system. Its function is to control and regulate the functions of the internal organs of our body involuntarily.

1. Both the processes are similar as the response is not determined by the direction of the stimulus. They are nastic movement.
2. The first process of folding up of leaf is thigmonastic and the stimulus is touch. The second process of closing of petals is photonastic and the stimulus is light.

When a piece of thread is tightly tied around an animal’s pancreatic duct, the pancreatic juice containing digestive enzymes will not be able to reach the small intestine. The pancreatic juice contains enzymes which help in the digestion of food. In its absence (due to the blockage of the pancreatic duct), the animal would have difficulty in digesting certain food substances.
However, the pancreas being an endocrine gland releases insulin directly into the blood. Since, the main function of insulin is to maintain the blood sugar level in the body; the animal will not suffer from diabetes.

Receptors are sensory structures (organs/ tissues/ cells) that detect changes in the environment, which are called stimuli, and turn them into electrical impulses to be transferred to the brain. The tongue has taste buds which can detect chemicals in food and identify taste. Hence, it is considered as receptor. Effector is an organ that responds to stimulus. The tongue is a muscular organ that can respond to a stimulus. Hence, it is also considered as an effector organ.

The directional growth movement of a plant part in response to the touch of an object is called thigmotropism. Example: Tendrils grow towards any support which they happen to touch and wind around it.

Diabetes is caused due to less or no secretion of hormone insulin by pancreas. In such a person, blood sugar level is high. Insulin converts extra sugar present in blood into glycogen. Thus, patients suffering from diabetes are given insulin injection to control their blood sugar level.

Tropic movements:

1. These movements are always in the direction of the stimulus.
2. These movements are slow.
3. These movements are exhibited by all parts of a plant. For example, movement of shoot towards the light and not towards gravity.

Nastic movements:

1. These movements are neither away nor towards the stimulus.
2. These movements are fast.
3. These movements are exhibited by the flat organs (like leaves and petals of flowers) of a plant. For example, the bending and drooping of leaves in ‘Touch-me-not’ plant.

1. The phenomenon exhibited by the positions of plant parts A and B is geotropism.
2. The stimulus which causes plant part A to grow and bend upwards and part B to bend downwards is gravity.

1. During the daytime the petals of moon flower close when there is bright light.
2. At night, when it is dark the petals of moon flower opens up. This phenomenon is known as photonasty.

Gibberellins:

1. Gibberellins are useful in promoting the growth of the plants.
2. They are also useful in in increasing sugar yield in sugarcane.

There are 5 sense organs: Eyes, ears, nose, tongue and skin.

Phototropism – The movement of a plant part in response to light is called phototropism.
Example - Stem bends towards the light is positive phototropism.

A growth movement ofa plant part in response to an external stimulus in which the direction of stimulus determines the direction of response is called tropism. Example – The bending of plant stem towards light is an example of positive phototropism.

The electrical impulses generated in the nerve cells will reach only those cells that are connected by nervous tissue, not each and every cell in the animal body. Therefore multicellular organisms require another means of communication between cells, namely, chemical communication.

A reflex action is a rapid, automatic response to a stimulus. It does not involve any thinking. For example, we close our eyes immediately when the bright light is focused. Walking, on the other hand, is a voluntary action. It is under our conscious control.

1. Reflex action.
2. Impulses from various body parts will not conducted to brain.
3. Message from brain will not be conducted to various organs.

CNS – Central nervous system.

1. Cerebrum.
2. Spinal cord.

The five types of tropisms are: Phototropism, Geotropism, Chemotropism, Hydrotropism and Thigmotropism. The various types of tropic movements help the plants to survive. Example even if a seed is planted upside down, its root will grow downwards into earth because it is positively geotropic.

Difference between involuntary and reflex actions is as follows:

Involuntary actions	Reflex actions
It is a set of muscles movement over which we do not have control. Such actions are controlled by brain. For example-contraction of muscle of our digestive tract, beating of heart etc.	It is rapid, spontaneous and involuntary activity that is produced in response to a stimulus. It is controlled by spinal cord. Example-removal of hand with jerk when someone touches a hot object.

Iodine is necessary for the thyroid gland to make thyroxin hormone. In case, iodine is absent in our diet, there is a possibility of Goitre. Iodised common salt contains proper content of iodine. To avoid deficiency of iodine, iodised salt is recommended.

1.  

1. Sensory neuron.
2. Spinal cord (CNS).
3. Mortor neuron.
4. Effector (muscle in arm)

2. Name — Reflex arc.

Direction:

1. Receptor (hand) to spinal cord through sensory neuron,
2. Sensory neuron to motor neuron through Spinal cord to effector through motor neuron.

The thinking part of our brain is the forebrain. It has separate areas that are specialized for hearing, smelling, sight, taste, touch, etc. The forebrain also has regions that collect information or impulses from the various receptors. When the smell of an incense stick reaches us, our forebrain detects it. Then, the forebrain interprets it by putting it together with the information received from other receptors and also with the information already stored in the brain.

The movement of plant part in response to gravity is called geotropism. Example – Roots grow towards gravity.

		Source Gland	Major Effect
a.	Parathormone	Parathyroid gland	Controls the amount of calcium in blood.
b.	Progesterone	Ovary	Thickens the utering lining and inhivits FSH and LH.

1. The function of the nervous system is to coordinate the activities of our body.
2. It helps all other systems of our body to work together.
3. It receives information from the surroundings, processes it, interprets it and then responds accordingly.