Biology Exam: Control and Coordination - Global Indian International School PDF

Kuala Lumpur, Malaysia SEMESTER I NAME: _______________________ REF: 2024-25/ SCI /STD 10/ HO 06 CLASS: _______________ SUBJECT: Biology DATE: Topic:...

Kuala Lumpur, Malaysia SEMESTER I NAME: _______________________ REF: 2024-25/ SCI /STD 10/ HO 06 CLASS: _______________ SUBJECT: Biology DATE: Topic: Control and Coordination As the complexity of the individuals, plants or animals increases the different cells and organs become separated from each other by greater distance. Thus, it becomes necessary to have a system by which the different parts of the organisms can function as a single unit. This is possible only if the different parts can coordinate with each other and carry out a particular function. To carry out a simple function such as picking up an object from the ground there must be coordination of the eyes, hands, legs and the vertebral column. The eyes must focus on the object, the hands have to pick it up and grasp it, the legs must bend and so does the backbone (vertebral column). All these actions must be coordinated in such a manner that they follow a particular sequence, and the action is completed. A similar mechanism is also needed for internal functions of the body. The changes in the environment to which the organisms respond and react are called stimuli. The response of organisms to a stimulus is usually in the form of some movement of their body part. Both plants and animals react (or respond) to various stimuli around them. At the same time, the internal conditions of the body should be maintained constant. This is called homeostasis. Homeostasis is derived from 'homeo' meaning same and 'stasis' meaning standing still. The internal conditions of the body are maintained at a constant by controlling the physiology of the organism. Just as in animals, plants also must control and coordinate their various functions. COORDINATION IN PLANTS: Unlike animals, plants do not have a nervous system. Plants use chemical substances called plant hormones or phytohormones for control and coordination. These hormones control one or other aspect of the growth of the plant. The growth of a plant can be divided into three stages: Cell division, cell enlargement and cell differentiation. These three stages of plant growth as well Page 1 of 22 Copyright © Global Indian International School  as promotion of dormancy, breaking of dormancy, stomata control, falling of leaves, fruit growth, ripening of fruits, and ageing in plants are controlled by the various plant hormones. There are four major types of plant hormones: 1. Auxins 2. Gibberellins 3. Cytokinins 4. Abscisic acid 5. Ethylene gas Auxins, gibberellins and cytokinins are the plant hormones which promote growth of plants. Whereas abscisic acid is a plant hormone which inhibits (or prevents) the growth. Auxins: This hormone promotes cell enlargement and cell differentiation in plants. Promotes fruit growth. Responsible for Phototropic and Geotropic movement in plants. Auxin is made at the tips of stems and roots. Auxin moves away from light, and towards gravity. Auxin has opposite effect on the growth of stems and roots. It speeds up growth in stem but it slows down growth in roots. Synthetic auxins like indole -3- acetic acid, 2,4 – D, are applied in agriculture and horticulture. Gibberellins: Promote cell enlargement and cell differentiation in the presence of auxins. Helps mainly in stem elongation, breaking dormancy in seeds and buds and promoting germination. They also promote growth in fruits. Gibberellic acid (GA3) is sprayed on grape vines to induce parthenocarpy (Development of seedless grapes). Cytokinins: They promote cell division in plants. Help to break the dormancy of seeds and buds. They also delay ageing of leaves. Cytokinins promote the opening of stomata and promote fruit growth. Abscisic acid: This hormone mainly functions as a growth inhibitor. It promotes the dormancy in seeds and buds. It helps in closing of stomata. ABA is known to promote wilting and falling of leaves. It also causes the detachment of flowers and fruits from the plants. Ethylene gas is a plant hormone that plays a vital role in stimulating ripening of fruits. If we keep raw fruits with a ripe one, the ethylene gas released by ripe fruit will fasten the ripening of the raw fruits around it. When Calcium carbide meets water, it produces Page 2 of 22 Copyright © Global Indian International School acetylene gas. Acetylene gas helps ripening of fruits like ethylene gas. Calcium carbide is used by fruit vendors to ripen fruits quickly. Plant Movements Movements in plants can be divided into two main types, viz. tropic movement and nastic movement. Geotropic Movement: The growth in a plant part in response to gravity is called geotropic movement. Roots usually show positive geotropic movement, i.e. they grow in the direction of gravity. Stems usually show negative geotropic movement. Phototropic Movement: The growth in a plant part in response to light is called phototropic movement. Stems usually show positive phototropic movement, while roots usually show negative phototropic movement. If a plant is kept in a container in which no sunlight reaches and a hole in the container allows some sunlight; the stem finally grows in the direction of the sunlight. This happens because of a higher rate of cell division in the part of stem which is away from the sunlight. As a result, the stem bends towards the light. The heightened rate of cell division is attained by increased secretion of the plant hormone auxin in the part which is away from sunlight. Hydrotropic Movement: When roots grow in the soil, they usually grow towards the nearest source of water. This is a positive hydrotrophic movement. Page 3 of 22 Copyright © Global Indian International School Thigmotropic Movement: The growth in a plant part in response to touch is called thigmotropic movement. Such movements are seen in the tendrils of climbers. The tendril grows in a way so that it can coil around a support. The differential rate of cell division in different parts of the tendril happens due to the action of auxin.. Chemotropic Movement: The movement of a plant part in response to chemical stimulus is. If the plant part shows movement (or growth) towards the chemical, it is called positive chemotropism. However, if the plant part shows movement (or growth) away from the chemical, then it is called negative chemotropism. The growth of pollen tubes towards the ovule during the process of fertilization in a flower is an example of positive chemotropism. In this case the pollen tube grows towards the sugary substance secreted by the ripe stigma of carpel in the flower. NASTIC MOVEMENT The movements which do not depend on the direction in which the stimulus acts are called nastic movement. Page 4 of 22 Copyright © Global Indian International School Seismonastic / Thigmonastic Movements: These movements are brought about by mechanical stimuli such as contact with a foreign body, fast wind and rain drops etc. For example; when someone touches the leaves of Mimosa pudica, the leaves droop. The drooping is independent of the direction from which the leaves are touched. Such movements usually happen because of changing water balance in the cells. When leaves of mimosa are touched, the cells in the leaves lose water and become flaccid; resulting in drooping of leaves., Biophytum sensitivum and Neptunia, etc show similar nastic movements. Photonastic Movements: These movements are induced by fluctuations in the intensity of light. Such movements are exhibited by flowers of several plants. Many flowers open with the increasing illumination of the day and close with the decrease in light intensity. Flowers of Cestrum nocturnum, Moon flower open at night, and close with the dawn of the day. Flowers of Dandelion bloom in the morning and close when night falls. Thermonastic Movements: Such movements are brought about by changes in temperature. Many of the flower movements are thermonastic for example, Mirabilis jalapa starts blooming late afternoon or evening in response to a temperature drop and closes by mid-morning. The blooming of tulip flowers as the temperature rises is another example of thermonastic movement. Nyctinastic Movements: These movements are commonly called ‘sleeping movements’. Stimuli is light and temperature. These movements are induced by alternation of day and night. The leaves of some plants like clover and oxalis (leguminous plants), growing approximately horizontal during the day, begin to droop and close toward evening and do not rise again until the next morning. CONTROL and COORDINATION in ANIMALS: In animals, the nervous system and hormonal system called endocrine system are responsible for control and coordination. The Nervous System The nervous system is composed of specialized tissues, called nervous tissue. The nerve cell or neuron is the functional unit of the nervous system. It is the nervous system which is mainly responsible for control and coordination in complex animals. Page 5 of 22 Copyright © Global Indian International School Receptors: Receptors are the specialized tips of the nerve fibres that collect the information to be conducted by the nerves. Receptors are in the sense organs of the animals. These are classified as follows: Phono-receptors: These are present in inner ear. Functions: The main functions are hearing and balance of the body. Photo-receptors: These are present in the eye. Function: These are responsible for visual stimulus. Thermo-receptors: These are present in skin. Functions: These receptors are responsible for pain, touch and heat stimuli. Olfactory-receptors: These are present in nose. Functions: These receptors receive smell. Gustatory-receptors: These are present in the tongue. Functions: These helps in taste detection. All the receptors in the sense organs receive stimuli from the surrounding environment and send the message conveyed by them to spinal cord and brain in the form of electrical impulses through sensory nerves. An effector is a part of the body which can respond to a stimulus according to the instructions sent from the nervous system (spinal cord and brain). The effectors are mainly the muscles and glands of our body. HUMAN NERVOUS SYSTEM Neuron Neuron is the structural and functional unit of the nervous system. Each neuron has three main parts: dendrites, cyton/soma/cell body and axon. Dendrites receive impulses from other neurons. Cyton/soma processes the impulse. Axon transmits the impulse, either to another neuron or to muscles/glands, etc. Axon may be myelinated or non-myelinated. The impulse transmission is faster in myelinated neurons. Page 6 of 22 Copyright © Global Indian International School  STRUCTURE OF A NEURON Types of neuron Sensory neuron: These neurons receive signals from a sense organ. Motor neuron: These neurons send signals to a muscle or a gland. Association or relay neuron: These neurons relay the signals between sensory neuron and motor neuron. Synapse: The point contact between the terminal branches of axon of one neuron with the dendrite of another neuron is called synapse. Page 7 of 22 Copyright © Global Indian International School Neuromuscular Junction (NMJ): NMJ is the point where a muscle fibre meets a motor neuron carrying nerve impulse from the central nervous system. Transmission of nerve impulse: Nerve impulses travel in the following manner from one neutron to the next : Dendrites → cell body → axon → nerve endings at the tip of axon → synapse → dendrite of next neuron. Chemical released from axon tip of one neuron, cross the synapse or neuromuscular junction to reach the next cell. Acetylcholine is one such neurotransmitter. The Organs of the Human Nervous System 1. Central Nervous System: The central nervous system is composed of the brain and the spinal cord. The brain controls all the functions in the human body. The spinal cord works as the relay channel for signals between the brain and the peripheral nervous system. 2. Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and spinal nerves. There are 12 pairs of cranial nerves. The cranial nerves Page 8 of 22 Copyright © Global Indian International School come out of the brain and go to the organs in the head region. There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are below the head region. Visceral nerves connect internal organs of the body to spinal cord and some directly to brain. 3. Autonomous Nervous System: The autonomous nervous system is composed of a chain of nerve ganglion which runs along the spinal cord. It controls all the involuntary actions in the human body. The autonomous nervous system can be divided into two parts: Sympathetic nervous system. Parasympathetic nervous system. Sympathetic Nervous System: The SNS controls our ‘fight or flight’ response. If we find ourselves in a dangerous situation, it is the SNS that prepares us to save ourselves by either fighting the threat or running away from it. When confronted with a potential threat, the SNS directs energy away from non-essential functions (like the digestive system) and towards functions that are essential to survival. First, the hormone adrenaline is released from the adrenal gland. As adrenaline flows through your bloodstream, it causes several physiological changes in the body that prepare it to fight or flee. Heart rate and blood pressure are both increased. This boosts the flow of oxygenated blood to the muscles, which contract, ready for action. At the same time, the bronchial tubes dilate, increasing airflow in and out of the lungs and sending extra oxygen to the brain to improve alertness. The pupils also dilate, which allows more light to enter your eyes so you can see your surroundings more clearly. All these responses happen quickly and involuntarily, allowing you to react rapidly to the perceived threat. For example, if you see a car speeding towards you, you may leap out of the way before you have even fully registered what is happening, thanks to the actions of the SNS. Key Effects of the Sympathetic Nervous System Adrenaline is released Heart rate increases Blood pressure increases Bronchial tubes dilate Page 9 of 22 Copyright © Global Indian International School  Glycogen is converted to glucose at an increased rate Pupils dilate Muscles contract Saliva production decreases Mucus production decreases Urine Secretion decreases Activity in the stomach decreases Motility of the large and small intestine decreases Parasympathetic Nervous System: This part of the autonomous nervous system slows down the activity of an organ and thus has a calming effect. During sleep, the breathing rate slows down and so does the heart rate. This is facilitated by the parasympathetic nervous system. It can be said that the parasympathetic nervous system helps in the conservation of energy. It keeps your heart rate and blood pressure steady while stimulating activities related to digestion and sexual function. These include the production of saliva, tears, urinination, digestion, defecation, and sexual arousal. Key Effects of the Parasympathetic Nervous System Saliva production increases Mucus production increases Motility of the large and small intestines increases Activity in the stomach increases Urine secretion increases Bronchial muscles contract Pupils are constricted Heart rate is decreased Page 10 of 22 Copyright © Global Indian International School Human Brain: Human brain is a highly complex organ, which is mainly composed of nervous tissue. The tissues are highly folded to accommodate a large surface area in less space. The brain is covered by a three-layered system of membranes, called meninges. Cerebrospinal fluid is filled between the meninges. The CSF cushion the brain against mechanical shocks. Furthermore, the human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain. Page 11 of 22 Copyright © Global Indian International School Parts of Human Brain: Fore-brain: It is composed of the olfactory lobes, cerebrum and diencephalon. Mid-brain: It is composed of the hypothalamus. Hind-brain: It is composed of the cerebellum, pons, medulla oblongata. Some main structures of the human brain are explained below: Fore brain: Olfactory lobes: Concerned with sense of smell. Cerebrum: The cerebrum is the largest part in the human brain. It is divided into two cerebral hemispheres, the right and left hemispheres. The 2 hemispheres are held by band of nerve fibres called Corpus callosum that transmits messages from one side to other. Each hemisphere controls the opposite side of the body. Cerebral hemisphere is hollow from inside and their walls have 2 regions. Outer cortex (grey coloured cell bodies) and inner medulla (axons of neurons- white matter). Each hemisphere consists of 4 lobes. Frontal (reasoning, planning, speech, movement, emotions, problem solving) Parietal (movement, orientation and recognition), Occipital (visual processing) and Temporal lobe (auditory perception, memory, speech). Functions of cerebrum The cerebrum controls voluntary motor actions. It is the site of sensory perceptions, like tactile and auditory perceptions. It is the seat of learning and memory. Diencephalon: Lies between cerebrum and mid brain. It is the link between the nervous system and the endocrine system. The diencephalon receives signals from the nerves and interprets the signals and then the pituitary gland responds by secreting hormones. Consists of 2 parts. Thalamus: Relay centre for pain, pressure. Hypothalamus: The hypothalamus lies at the base of the cerebrum. It controls sleep and wake cycle (circadian rhythm) of the body. It also controls the urges for eating and drinking. Controls body temperature, pituitary gland and blood pressure. Page 12 of 22 Copyright © Global Indian International School Mid-brain Connects fore brain with hind brain. The midbrain is a portion of the brainstem, positioned above the pons, at the very top of the brainstem, directly underneath the cerebellum. This is one of the most important components of the central nervous system (CNS), as all neuronal transmissions that pass through the body, throughout the peripheral nervous system (PNS) to the CNS are relayed to at some point – to and/or from the brain – pass through the midbrain. Function of Mid brain It enables your brain to integrate sensory information from your eyes and ears with your muscle movements, thereby enabling your body to use this information to make fine adjustments to your movements. Hind-brain It is the region of the brain formed by the pons, medulla oblongata (also known as just the medulla), and the cerebellum. Together, these three structures govern our autonomic, or 'automated' body systems, controlling everything from our heart, breathing, and sleep patterns to our bladder function, sense of equilibrium, and fine motor control. Pons: It relays impulses between the lower cerebellum and spinal cord, and higher parts of the brain like the cerebrum and midbrain, also regulates respiration. Medulla: Medulla forms the brain stem, along with the pons. It lies at the base of the brain and continues into the spinal cord. The medulla controls various involuntary functions, like heart beat respiration, etc. It controls involuntary actions. Example: Blood pressure, salivation, vomiting. Cerebellum: The cerebellum is positioned right behind the brainstem and midbrain, Below the cerebral lobes. It is sometimes referred to as the "little brain" because it looks like a miniature version of the cerebrum. It coordinates the motor functions. When you are riding your bicycle, the perfect coordination between your pedalling and steering control is achieved by the cerebellum. It controls posture and balance. It controls the precision of voluntary action. Page 13 of 22 Copyright © Global Indian International School Spinal cord: The spinal cord is a part of the central nervous system. It is a long pipe-like structure arising from the medulla oblongata, part of the brain consisting of a collection of nerve fibres, running through the vertebral column of the backbone. It is segmented with a pair of roots (dorsal and ventral roots) consisting of nerve fibres joining to form the spinal nerves. Cross-section of spinal cord displays grey matter shaped like a butterfly surrounded by a white matter. Grey matter consists of the central canal at the centre and is filled with a fluid called CSF (Cerebrospinal fluid). The white matter consists of a collection of axons permitting communication between different layers of CNS. Function of Spinal Cord Forms a connecting link between the brain and the PNS Provides structural support and builds a body posture Facilitates flexible movements Myelin present in the white matter acts as an electrical insulation Communicates messages from the brain to different parts of the body Coordinates reflexes Receives sensory information from receptors and sends towards the brain for processing. Reflex Action: Reflex action is a special case of involuntary movement. When a voluntary organ is in the vicinity of sudden danger, it is immediately pulled away from the danger to save itself. For example, when your hand touches a very hot electric iron, you move away your hand in a jerk. All of this happens in a flash and your hand is saved from the imminent injury. This is an example of reflex action. Reflex Arc: The path through which nerve signals involved in a reflex action travel, is called the reflex arc. The following flow chart shows the flow of signal in a reflex arc. Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle) The receptor is the organ which comes in the danger zone. The sensory neurons pick signals from the receptor and send them to the relay neuron. The relay neuron is Page 14 of 22 Copyright © Global Indian International School present in the spinal cord. The spinal cord sends signals to the effector via the motor neuron. The effector comes in action, moves the receptor away from the danger. The reflex arc passes at the level of the spinal cord and the signals involved in reflex action do not travel up to the brain. This is important because sending signals to the brain would take more time. Although every action is ultimately controlled by the brain, the reflex action is mainly controlled at the level of spinal cord. Protection of brain and spinal cord Brain is protected by a fluid filled balloon which acts as shocks absorber and enclosed in cranium (Brain box) Spinal cord is enclosed in vertebral column. Muscular Movements and Nervous Control: Muscle tissues have special filaments, called actin and myosin. When a muscle receives a nerve signal, a series of events is triggered in the muscle. Calcium ions enter the muscle cells. It results in actin and myosin filaments sliding towards each other and that is how a muscle contracts. Contraction in a muscle brings movement in the related organ. Page 15 of 22 Copyright © Global Indian International School Endocrine System: The endocrine system is composed of several endocrine glands. A ductless gland is called endocrine gland. Endocrine gland secretes its product directly into the bloodstream. Hormones are produced in the endocrine glands. Hormones are mainly composed of protein. They are special messengers that control many body functions, including hunger, body temperature, mood, growth and development, metabolism, reproductive processes etc. Hormones assist the nervous system in control and co-ordination. Nerves do not react to every nook and corner of the body and hence hormones are needed to affect control and coordination in those parts. Moreover, unlike nervous control, hormonal control is somewhat slower. Hormones: These are the chemical messengers secreted in very small amounts by specialised tissues called ductless glands or Endocrine glands directly into the blood stream. Through the blood, these hormones in animals reach their target site to stimulate or inhibit specific physiological processes. They act on target tissues/organs usually away from their source. The target cell has on its surface or cytoplasm, a specific protein molecule called receptor. The receptor can recognise and pick out the specific hormone capable of acting in cell. There are around 20 major hormones in animals that are released by the endocrine glands into the blood, playing a major role in many of the physiological processes happening in the body. The hormone levels in the body can be influenced by several factors like stress infection, minerals in the blood etc. Gland: A cell, a tissue or an organ which secretes useful chemical compounds required for particular function. Page 16 of 22 Copyright © Global Indian International School Types of Glands Endocrine Glands: A ductless gland that secretes hormones directly into the bloodstream. For example: Pituitary, Thyroid, Adrenal, Parathyroid etc. Exocrine Glands: An exocrine gland is one that secretes either directly or by ducts onto a surface. For example, salivary glands release saliva through ducts into the mouth to moisten food and begin the digestion process. Tear, sweat, gastric gland, liver etc. Heterocrine Glands: Glands that have both endocrine and exocrine glands are called heterocrine or composite glands. For example: The endocrine part of the pancreas is formed of Islets of Langerhans, which has Alpha cells that secrete glucagon, while the beta cells secrete insulin. Pancreas as an exocrine gland, secretes pancreatic juice that is involved in digestion of food. Gonads are heterocrine in nature. The exocrine part of the testis and the ovaries produce gametes while the endocrine part secretes hormones. Hypothalamus Hypothalamus is a minute region, almost the size of an almond, present at the centre of the human brain, near the pituitary gland. This region forms an important link between the nervous system, via the pituitary gland. Following are the important functions of the hypothalamus: Its main function is maintaining the body’s internal balance- homeostasis. Page 17 of 22 Copyright © Global Indian International School  It also connects the endocrine and the nervous system. Controls the release of 8 major hormones by the pituitary gland. Hypothalamus stimulates or inhibits many of the body’s activities to maintain homeostasis, such as regulating body temperature, controls sleep, appetite and body weight, heart rate and blood pressure, etc. It controls circadian rhythm of the body. Controls sexual behaviour and reproduction. Pituitary gland It is a pea-sized gland located at the base of the brain. It is the master gland as it controls the secretions of all the other endocrine glands. It also secretes Growth Hormone (GH). Under-secretion of GH causes Dwarfism and over-secretion causes Gigantism in children and ‘Acromegaly’ in adults. Some of the other hormones released by this gland are Thyroid stimulating hormone, MSL(Melanocyte Stimulating hormone), LH (Luteinizing hormone), FSH (Follicle stimulating hormone) etc. Thyroid gland It is a butterfly-shaped gland located in the throat. It secretes the hormone ‘Thyroxine’ which regulates the metabolism of the body. It also plays a role in the bone growth, development of the brain and nervous system in children. Iodine is required to synthesize thyroxine in the body. In the case of iodine deficiency, under-secretion of thyroxine leads to goitre in adults. It causes enlargement of thyroid gland leading to swollen neck. Children suffer from Cretenism. There is complete stoppage of mental and physical growth of the child. Page 18 of 22 Copyright © Global Indian International School Parathyroid gland This gland releases parathormone which helps in regulating the calcium and phosphorus levels in the bone. Pineal gland This produces melatonin hormone that regulates the sleep patterns. Pancreas It is a leaf-like gland present behind the stomach in the abdomen. It is an endocrine as well an exocrine gland. As an endocrine gland, it manufactures two hormones – Insulin and glucagon. Both these hormones act antagonistically and regulate the sugar level in the blood. As an exocrine gland, it secretes enzymes to break down the proteins, lipids, carbohydrates and nucleic acids in food. An insufficient amount of insulin from the pancreas leads to diabetes. Adrenal gland Occurs in pairs above each kidney. It decreases in size with age. Secretes the hormone adrenaline or epinephrine which helps in flight and fight response. Also secretes noradrenaline, many mineralocorticoids and glucocorticoids are released by this gland. Cortisol is a hormone, which has anti-inflammatory properties and aids the immune system. The adrenal gland also helps to regulate metabolism and blood pressure through various other hormones. Epinephrine: Also called adrenaline, this hormone rapidly responds to stress by increasing the heart rate, breathing rate, cardiac muscle contractions, blood pressure and raising blood glucose levels in the blood, accelerate the breakdown of glucose in skeletal muscles and stored fats in adipose tissue. Page 19 of 22 Copyright © Global Indian International School  Norepinephrine: Also called noradrenaline, this hormone works with epinephrine in reacting to stress. Its primary function is to mobilize the body and brain for action. Release of both epinephrine and norepinephrine is stimulated directly by neural impulses from the sympathetic nervous system. Thymus Thymus gland is positioned between the two lungs behind your breastbone (sternum). Thymosin is the hormone secreted by this gland. Plays an important role in our immune system. After puberty, thymus gland slowly starts to decrease in size and is replaced by fat. Gonads Gonads are the gamete-producing organs – testes in males and ovaries in females. The testes produce the male hormone testosterone and the ovaries produce the female hormones oestrogen and progesterone. Testosterone and oestrogen help in producing gametes and are responsible for the sexual characteristics of males and females respectively. Progesterone is the pregnancy hormone. Feedback Mechanism in Hormones Hormones should be secreted in precise quantities because both excess or deficiency of hormones has a harmful effect on the body. The timing and amount of hormone released by various glands by Feedback mechanism is in built in our body. For example: When we eat a carbohydrate rich meal, the sugar level of the blood rises. It is detected by the cells of pancreas, which respond by producing and secreting more insulin into the blood. In this way, blood glucose level is brought back to normal. The increase in the blood sugar level stimulates the secretion of insulin so that the sugar level is maintained. If the blood sugar level falls below normal, then it stimulates the secretion of glucagon. The glucagon stimulates the breakdown of glycogen to glucose, and thus, the normal sugar level is maintained. Page 20 of 22 Copyright © Global Indian International School  FEEDBACK CONTROL OF BLOOD GLUCOSE LEVEL. Questions for Practice 1. What are hormones? 2. What is a target organ? 3. Define gland. 4. What are endocrine glands? Give example. 5. What are exocrine glands? Give examples. 6. Write the functions of adrenal gland. 7. Why is the hormone secreted by adrenal gland called as emergency hormone? 8. What are the functions of thyroid gland. 9. What are the functions of pituitary gland? 10. Name the hormones secreted by pancreas. 11. Name the disease caused by the deficiency of iodine. 12. Name the male and female sex hormone. Page 21 of 22 Copyright © Global Indian International School 13. Name the diseases caused by improper release of Growth hormone by the Pituitary gland. 14. What are the different types of nerves found in human body? Mention the functions of each. 15. Write the effects of sympathetic and parasympathetic nervous system on the following: a. Heart b. Blood Vessels c. Bronchi d. Eyes e. Gastric Bladder 16. If the parasympathetic nervous system causes constriction of pupil what will be the effect of sympathetic nervous system. 17. What are the four main parts of the fore brain? Give the function of each part. 18. What are the three parts of the mid brain and their functions? 19. Which part of the human brain is responsible for: Intelligence and Memory, Adjustment movement and Posture, Smell? 20. Give the role of Frontal lobe, temporal, lobe and medulla oblongata. 21. Name the different lobes found in the fore brain and give their functions. 22. Differentiate between (i)tropic and nastic movements. (ii)axon and dendrites (iii)cerebrum and cerebellum. 23. How does the nervous tissue cause action? 24. What are Phytohormones? Give examples 25. Which organ secretes hormone when the blood sugar rises? Name a digestive enzyme released by this organ. 26. What will happen when plant is exposed to unidirectional light? 27. What is reflex arc? 28. What is synapse? 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