Question 1

Which of the following is a plant hormone?

Accepted Answer

Insulin is secreted by Islets of Langerhans of the pancreas and serves to lower the blood glucose level by stimulating the uptake of glucose by cells, specifically muscle cells, liver cells and adipose tissues cells. Thyroxine is a thyroid hormone which targets all tissues and stimulates metabolic rate, growth and development. Oestrogen is the female sex hormone secreted by developing follicles in the ovary. It serves to stimulate the growth of the uterus and the vagina, is necessary for egg maturation as well as for the development of the secondary sex characteristics in females. Thus, options A, B and C are incorrect as these hormones are animal hormones. Cytokinins are the plant growth hormones that regulate the cell division in root and shoot of the plant both in vivo and in-vitro. So, the correct answer is 'Cytokinin'

Question 2

The gap between two neurons is known as:

Accepted Answer

Neuron is the structural and functional unit of nervous system. It consists of dendrites, axon and soma. Dendrites are the small extension of nerve cells that receives signals from sensory receptors or other neurons.The long extension of cell body of nerve cell is called as axon that serves to conduct the nerve impulse away from the cell body. Two neurons are never physically connected to each other and synapse place where two neurons are in close connection to facilitate transmission of information from one neuron to the next one.The extracellular space between two neurons is known as synaptic cleft. Nerve impulse is all or none response of nerve fibres and is defined as wave of change in polarity of neuron membrane, caused by movement of ions across the membrane.So, the correct answer is option B.

Question 3

The brain is responsible for:

Accepted Answer

The fore-brain is responsible for thinking and interpreting sensory information. The hind-brain is responsible for maintaining the posture and balance of the body. Since all the above functions are controlled by the brain, therefore, the correct answer is option D.

Question 4

What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Accepted Answer

Receptors are the cells that detect the changes in chemical and physical conditions of external and internal environment of an animal. Main categories of sensory receptors include mechanoreceptors, thermoreceptors, pain receptors, chemoreceptors and photoreceptors. Stimulation of sensory receptors generates a nerve impulse that travels through the CNS (brain/spinal cord) where integration and interpretation of sensory information take place. This is followed by a relay of motor impulses from CNS to effector organ to generate the response according to the stimulus. If receptors are not working properly, the external stimulus won’t be able to stimulate receptors and no nerve impulse is generated. The result is that the body would not respond to changes in the surroundings.

Question 5

Draw the structure of a neuron and explain its function.

Accepted Answer

Neurons are the fundamental unit of the nervous system. Neurons are also called as nerve cells. The main function of the neurons is to pass the receiving information and send appropriate signals to the rest parts of the body. The signals received are in the form of electrical signals. Neuron comprises of dendrite, axon and cell body. Dendrites receives messages from the surrounding and sends it to the cell body. Cell body consists of nucleus, mitochondria and other organelles. Axon transmits the message away from the cell body and pass it to the the next receiving neuron.

Question 6

How does phototropism occur in plants?

Accepted Answer

The movement of plant or other organism in response to light is called as phototropism. The movement can be either towards the light or away from it. Stem grows in direction of the sunlight (positively phototropic) and roots grows away from it (negatively phototropic). The growth is controlled by plant hormone, auxin. The growth of the side of the shoot is stimulated by the concentration of auxin. Bending of the stem is caused by the unequal growth on the two sides of the shoot. Phototropic movement is generally caused by the increased auxin on the dark side and lesser auxin on the illuminated  side.

Question 7

Which signals will get disrupted in case of a spinal cord injury?

Accepted Answer

Spinal cord serves as means of communication between the brain and peripheral nerves that leave the cord. Injury to spinal cord would hamper passing down the somatic motor impulses (voluntary actions of skeletal muscles) through it to different body parts. Also, owing to its role in a spinal reflex arc, the spinal injury would affect the reflex actions.

Question 8

How does chemical coordination occur in plants?

Accepted Answer

Plant hormones bring about chemical coordination in plants. They are synthesized away from the site of their action and then are diffused there. Different plants hormones are responsible for growth, development and tropic responses. For example, auxin, cytokinins and gibberellins are growth hormones, ethylene is fruit ripening hormone while abscisic acid is growth inhibitory hormone.

Question 9

What is the need for a system of control and coordination in an organism?

Accepted Answer

Nervous system and endocrine system are responsible for control and coordination of complex, multicellular human body with multiple organ systems of complex functioning. Endocrine secretions (hormones) regulate proper growth and development and functioning of different organs. Nervous system enables us to respond to our surroundings and to perform daily activities. It does so by sensing external and internal stimuli followed by a relay of sensory information to CNS (Central Nervous System) for processing and generation of motor output, i.e., involuntary and voluntary actions.

Question 10

How are involuntary actions and reflex actions different from each other?

Accepted Answer

The involuntary actions include the skeletal muscle movement those are under regulation of the autonomic division (ANS) of the peripheral nervous system which consists of motor fibres that relay nerve impulses from CNS (Central Nervous System) to cardiac and smooth muscles and glands, thereby controls the functioning of internal organs, without our conscious control. Reflex action is an automatic, quick and innate response to particular stimuli that is mediated by a reflex arc. A simple reflex arc consists of sensory receptors, afferent neuron, spinal cord, efferent neuron and effector organ. Therefore, involuntary actions are unconscious responses produced by brain while reflex actions do not involve the brain for information processing.

Question 11

Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Accepted Answer

Difference between nervous and hormonal mechanisms: Nervous system Hormonal system1. It consists of central nervous system (CNS) and peripheral nervous system (PNS).1. It consists of endocrine glands.2. A neuron is the structural and functional unit of the nervous system. It consists of dendrites, axon and soma. Dendrites are the small extension of nerve cells that receives signals from sensory receptors or other neurons. The long extension of the cell body of the nerve cell is called as axon that serves to conduct the nerve impulse away from the cell body/soma. 2. The endocrine secretion of glands (hormones) is released directly into the blood to affect the target cells. 3. Nerve impulses are not specific in their actions.3. Hormones exhibit specific effect by affecting only target cells that carry the specific receptors.  4. Neural responses are quick and short lived.4. Hormonal effects are the slow but long term.5. The flow of information is rapid.5. The flow of information is slow.

Question 12

What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Accepted Answer

Movement in sensitive plants   Movement in legs1. Movement in sensitive plants occurs in response to external or internal stimulus and is categorized as tropic or nastic movement; it is an involuntary action.1. Movement in legs is under the regulation of nervous system and is a voluntary response, i.e., conscious response.2. It does not involve any special tissues for the relay of information.2. Leg movement is assisted by complex network of nervous system that includes CNS and PNS3. Movement in the sensitive plant does not involve any specific proteins.3. Contraction and relaxation of leg muscles to bring about leg movement is assisted by specific proteins like actin, myosin etc.

Chapter 7 : Control and Coordination