Q 1 – Define ‘reflex action’
It is an automatic, spontaneous and an immediate involuntary response to a stimulus controlled usually by the spinal cord. e.g. knee jerk movement.
Q 2 – Name the largest cell in the human body.
Nerve cell (Neuron).
Q 3 – Give an example of plant hormone that promotes growth.
Auxin
Q 4 – What are plant hormones?
The chemical substances produced in plants which help in the growth and development of plant, its tissues and other plants.
Q 5 – Name the part of neuron
(а) where information is acquired.
(b) through which information travels an electrical impulse.
(a) Dendrite
(b) Axon
Q 6 – Name two tissues that provide control and coordination in multicellular animals.
Muscular tissues and nervous tissue.
Q 7 – Name the hormone, the secretion of which is responsible for dramatic changes in appearance in girls and boys when they approach 10-12 years of age.
Testosterone is released from testes in males, estrogen is released from ovaries in females.
Q 8 – Name the hormone that helps in regulating the level of sugar in our blood. Name the glands that secrete it.
Insulin hormone is secreted by the pancreas.
Q 9 – Name a plant hormone that inhibits growth. Write its one more function
Abscisic acid inhibits growth in plants. It also causes closure of stomata during water stress.
Q 10 – A potted plant is made to lie horizontally on the ground. Which part of the plant will show:
(i) Positive geotropism
(ii) Negative geotropism
(i) Roots will shows positive geotropism.
(ii) Shoots will show negative geotropism.
Q 11 – Name a plant hormone which promotes growth in plants.
Auxin is a plant hormone that promotes growth and cell elongation in plants.
Q 12 – State one function each of pons and cerebellum.
Pons: Regulates rate of respiration
Cerebellum: Maintains equilibrium of the body during walking, jumping, etc.
Q 13 – Name a gaseous plant hormone. Give its role.
Ethylene is a gaseous hormone. It regulates fruit ripening.
Q 14 – How many spinal and cranial nerves are present in human body?
Spinal nerves = 31 pairs
Cranial nerves = 12 pairs
Q 15 – What are meninges?
The three membranes which cover the brain to protect it are called meninges.
Q 16 – How do we detect smell of hot spicy food from a distance?.
We have olfactory receptors in our nose which detect the smell of hot spicy food. This information is transmitted by nerve impulse to olfactory lobes of forebrain which interpret the information
Q 17 – Why do tendrils coil around hard objects or support?
The tendrils coil around hard objects or support due to a stimulus of touch (thigmotropism) which causes less growth on the side in contact with support than the side which is away from it. This unequal growth of two sides of tendril makes it coil around the support.
Q 18 – Name the hormones reponsible for regulation.
(i) Metabolism of carbohydrates, fats and proteins
(ii) Balance of calcium and phosphate
(iii) Blood pressure
(iv) Water and electrolyte balance.
(i) Thyroxin
(ii) Parathyroid hormone
(iii) Adrenaline
(iv) Vasopressin
Q 19 – How are the brain and spinal cord protected from mechanical shock?
Brain is present in a bony box called cranium (skull), spinal cord is protected by vertebral column. The cerebrospinal fluid present around the brain and spinal cord protect it from mechanical shock.
Q 20 – What is an association neuron?
Association neurons are present in cortex part of spinal cord between the sensory neuron and motor neuron. It helps to interconnect the signals between the sensory neuron and motor neuron by forming synapse with axon of sensory neuron and dendrite of motor neuron.
Q 21 – Which functions are regulated by the forebrain?
The thinking part of the brain is forebrain which controls
- Movement of voluntary muscles.
- Hearing, smell, sight, hunger, thirst, pain, etc. by its association areas.
- It also stores information and controls intelligence.
Q 22 – Explain how a squirrel responds a dangerous situation with help of its hormonal system.
When a squirrel perceives a dangerous situation, adrenaline hormone is released in its blood which increases its heart beat and blood supply to tissues. This provides energy to its cells and tissues at a faster rate and enables it to run away from emergency situation.
Q 23 – How are sensory neurons different from motor neurons?
Sensory neuorons take information from receptors and transmit the impulses towards central nervous system. Motor neurons carry message from control nervous system to the muscle, gland or an organ to enable it to respond.
Q 24 – How are receptors different from effectors?
Receptors are cells, tissues or organs which receive the information in form of stimulus. For example, photoreception, gustatory receptors, etc. Effectors are muscles, glands tissues or cells which respond according to the information received through motor neuron from the central nervous system.
Q 25 – Define peripheral nervous system. What are its components?
The nerves that directly arise from the central nervous system and contact different parts of our body to help their involuntary controls. Spinal nerves and cranial nerves are components of peripheral nervous system.
Q 26 – Lable the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in the given figure.
(a) Sensory neuron
(b) Spinal cord (part of CNS)
(c) Motor neuron
(d) Effector (Muscle)
Q 27 – Name the plant hormones responsible for the following:
(a) elongation of cells
(b) growth of stem
(c) promotion of cell division
(d) falling of senescent leaves
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Abscissic acid
Q 28 – Label the endocrine glands in figure given below.
(a) Pineal Gland
(b) Pituitary Gland
(c) Thyroid
(d) Thymus
Q 29 – Label the parts of a neuron in figure given below.
(a) Dendrite
(b) Cell Body
(c) Axon
(d) Nerve ending
Q 30 – Match the terms of Column (A) with those of Column (B)
(a) (iii)
(b) (iv)
(c) (i)
(d) (ii)
Q 31 – What are nastic and curvature movements? Give one example of each.
The non-directional responses to stimuli are called nastic movements e.g., drooping of leaves of touch-me-not plant. Curvature movement are the movement of plant parts towards or away from stimulus e.g., bending of shoot towards light.
Q 32 – How does feedback mechanism regulate the hormone action? Explain with the help of an example.
The presence or absence of a particular hormone can regulate its further formation with the help of a regulatory mechanism called feedback mechanism.
Example: Hypothalamus regulates thyroxin levels in blood by secreting thyroid stimulating hormone (TSH). If the thyroxine levels increases then hypothalamus stop secreting TSH in order to reduce the production of thyroxine from thyroid gland.
Low levels of thyroxin in blood again switches on the release of TSH from hypothalamus to increase levels of thyroxin in blood.
Q 33 – What are the different types of neurons and their functions in the human body?
There are mainly three types of neurons:
- Sensory neuron: They transmit information from receptors towards the central nervous system.
- Motor neuron: They transmit information from the central nervous system to effectors like muscles or glands.
- Relay neuron: It serves as a link between the sensory and the motor neurons in the brain or spinal cord.
Q 34 – What are the limitations to the use of electrical impulse?
The limitations to electrical impulse are
- Only those cells used that are connected by nervous tissue, while other tissues do not receive the information directly.
- It takes some times to reset the mechanism of generation of new electrical impulse once an electrical impulse had been generated.
Q 35 – What is ‘hydrotropism’? Describe an experiment to demonstrate ‘hydrotropism’
Hydrotropism’ is the directional growth of a plant part in response to water. For example: roots show hydrotropism as they grow towards water in the soil and are positively hydrotropic
An experiment to demonstrate hydrotropism is as follows:
- A porous pot filled with water is taken and inserted in a tub filled with dry sand.
- A freshly germinated pea seedling is sowed in the sand.
- As water is not available in sand, the root growing will bend towards the porous pot
filled with water. - A hydrotropic curvature of the root is observed as it grows towards water.
- This bending of root shows the movement in response towards water.
Q 36 – What is a tropic movement? Explain with an example.
The directional movements caused in plants due to an external stimuli are called tropic movements.
Example: During phototropism, the shoot bends towards light and show positive phototropism while the roots bend away from light to show negative phototropism.
Q 37 – What will happen if intake of iodine in our diet is low?
Iodine helps in the synthesis of thyroxin hormone from thyroid gland. Thyroxin hormone is necessary for carbohydrate, proteins and fat metabolism. Deficiency caused due to low level of iodine in diet might result is a disease called goitre in the person.
Q 38 – Answer the following:
(a) Which hormone is responsible for the changes noticed in females at puberty?
(b) Dwarfism results due to deficiency of which hormone?
(c) Blood sugar level rises due to deficiency of which hormone?
(d) Iodine is necessary for the synthesis of which hormone?
(a) Oestrogen
(b) Growth hormone
(c) Insulin
(d) Thyroxin
Q 39 – Answer the following:
(a) Name the endocrine gland associated with brain.
(b) Which gland secretes digestive enzymes as well as hormones?
(c) Name the endocrine gland associated with kidneys.
(d) Which endocrine gland is present in males but not in females?
(a) Pituitary
(b) Pancreas
(c) Adrenal gland
(d) Testes
Q 40 – Differentiate between tropic and nastic movements in plants.
Tropic Movements:
- There is directional growth of a plant or part of a plant in response to an external stimulus i.e., direction of stimulus controls direction of growth.
- The effect is more or less permanent.
- It is easily observed in stems and roots of plants.
- It occurs due to unequal growth on the two sides of a stem or root.
- For example, bending of root towards gravity and bending of shoot towards light.
Nastic Movements:
- The growth or movement is independent of the direction of stimulus.
- The effect is temporary and reversible.
- It occurs in specialised parts and organs of plants like leaves and petals of flowers.
- It usually involves alterations in cell volumes.
- For example, folding on leaflets of touch-me-not plant on touching them.
Q 41 – Mention one function for each of these hormones:
(a) Thyroxin
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone
(a) Thyroxin: It regulates carbohydrates, fat and protein metabolism.
(b) Insulin: It regulates blood sugar level.
(c) Adrenaline: It increases heart beat rate and supply of blood to various organs.
(d) Growth hormones: It regulates growth and development of an organism.
(e) Testosterone: It controls the bodily features, secondary sexual characters in males during puberty.
Q 42 – How does chemical coordination take place in animals?
Hormones secreted by the endocrine glands are directly poured into the blood stream as they are ductless glands. Blood carries these hormones to specific target tissue or organ where they act and trigger a particular biochemical or physiological activity in response to the stimulus received.
Q 43 – Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse?
The information received by the dendrites of neurons present at receptors is transferred in form of electrical impulse to the cell body, axon and the nerve endings at the ends of axon. At the axonal ends, chemicals are released between junction of two neurons called synapse. The chemical diffuses towards the dendrite of the next neuron where it generates an electrical impulse again. So, the electrical signals change to chemical signals and again to electrical signals for the next neuron.
Since the chemicals Eire released at the axonal ends and absent at dendrite end, the signal travels from axonal end to dendritic end of another neuron but not the reverse i.e., the flow of electrical impulse is unidirectional only.
Q 44 – While most of our actions are coordinated by the brain, still some of our actions need to be coordinated by the spinal cord. Why?
Brain is the thinking part which coordinates the various activities and processes in human beings. But, some actions which need to be quick, automatic and involuntary, do not involve any thinking processes.
So, such immediate responses are coordinated by the spinal cord and are called reflex actions.
Q 45 – The movements shown by the leaves of ‘touch me not’ plant on touching are different from the movement shown by seedling. Elaborate.
The opening and closing of the leaves of the ‘touch me not plant’ is a result of water change in amount of water in the plant cells, which is not dependent on growth. But, the movement of the seedling is a growth-dependent movement because it will not show any movement if it is prevented from growth.
Q 46 – The level of hormones should be well balanced in human beings in order to maintain the normal functioning of the human body. Explain this statement with two examples.
The level of hormones should be balanced in human beings because a deficiency or excess secretion of some hormones can have adverse effects on the human body. For example,
- A deficiency in the secretion of insulin from the pancreas increases the blood sugar level and causes diabetes.
- A deficiency in the secretion of growth hormone causes dwarfism whereas it excess secretion causes gigantism.
Q 47 – Chemical coordination plays a vital role in the activities of plants. Elaborate.
Coordination in human beings is carried out both by the nervous as well as the hormonal system. But, coordination in plants is dependent on the chemicals called as hormones. The hormone auxin and gibberellins help in the growth of the stem. Cytokinins help in cell division. Abscisic acid inhibits growth. Auxin is also involved in the bending of plants towards light.
Q 48 – The response of the body due to reflex actions is faster than those carried out by secretion of adrenaline in emergency situations. Why?
The reflex actions are the result of chemical-electrical impulses which are faster as they move through the nerve cell from one point to another, whereas, hormones are first released in the blood and they have to travel to the target site to bring about the response, which takes more time than reflex actions.
Q 49 – Villagers living in a hilly area were facing a problem that a lot of children in the village were developing swollen necks. The priest of the village told that it was due to the acts of the villagers who had annoyed their Goddess and they needed to offer sacrifice for getting rid of this problem. Dr. Kamal visited the village and properly listened to the problem of the villagers and advised them to use iodised salt instead of normal salt in their food. Villagers agreed to Dr. Kamal’s advice and within a few months the problem was overcome to a large extent.
(a) What was the cause of the swollen neck of children in the village?
(b) What values are shown by Dr. Kamal?
(c) Why was use of iodised salt advised to villagers by Dr. Kamal?
(a) The swollen neck is a disease called goitre. Goitre occurs due to deficiency of thyroxine hormone.
(b) Scientific aptitude, patience, problem solving ability and helpful nature.
(c) The use of iodised salt was advised because Iodine helps in production of thyroxine hormone which helps to prevent goitre.
Q 50 – Akhilesh saw a plant in his school garden which closed its leaves on touching. He observed the plant very closely for a long time. In the recess, he saw that some students were trying to pluck the plant from the pot. He went to them and advised them not to pluck the plant as it was their school’s property. He also told them about the importance of the plants and the peculiar behavior of the said plant. In this way, he was able to convince the students to not harm the plant.
(a) Why did the leaves of the plant close on touching?
(b) How is this response of plant different from reflex action in animals?
(c) What values are shown by Akhilesh?
(a) The leaves of the sensitive plants like Touch-me-not close on touching as they lose the turgor pressure in cells which causes drooping of its leaves/leaflets.
(b) Movement in Sensitive Plant:
- The response is produced due to the change in amount of water in the plant cells.
- No nerve or specialised tissue involved in the conduction of information.
Reflex action:
- An automatic, immediate, involuntary response of an organism.
- It is controlled by the spinal cord.
(c) Environment friendly, responsible, leadership, analytical thinking.