Control And Coordination- Class X

Chapter-7 Control and Coordination A system of control and coordination is essential in living organisms sothat the different body parts can function as a single unit to maintain homeostasis as well as respond to various stimuli. (Human homeostasis refers to the body's ability to regulate physiologically its inner environment to ensure its stability in response to fluctuations in the outside environment and the weather. Homeo=same and stasis=standing still) To carry out a simple function such as picking up an object from the ground there has to be coordination of the eyes, hands, legs and the vertebral column. The eyes have to focus on the object, the hands have to pick it up and grasp it, the legs have to bend and so does the back bone (vertebral column). All these actions have to 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. In animals, the nervous system, hormonal system and muscular system are responsible for control and coordination. Neurons are specialized cells of the nervous system. They use electrical and chemical signals for transferring information. They specialise in conducting information. Nerve cell or neuron is the fundamental unit of the

nervous system. Stimulus: a stimulus is a detectable change in the internal or external environment. Response: A reaction of an organism to a specific stimulus. Receptors: Receptors are specialized tips of the nerve fibres that collect the information to be conducted by the nerves. They are usually present in the sense organs. For e.g. Gustatory receptors help us to detect taste and olfactory receptors help us to detect smell. Reflex action: It is an involuntary and nearly instantaneous response to a stimulus. Nerve Impulse: The information passing through a neuron in the form of electrical and chemical signals is known as a Nerve Impulse. How is information conducted through neurons? The information is acquired at the end of dendritic tip of the neuron that are present in the sense organs / receptors. This sets of a chemical reaction in the at the dendrites generating an electrical impulse.The electrical impulse then travels from the dendritic tip to cyton and then to the axon of that neuron. When it reaches the nerve endings certain chemicals are released in response to the electrical impulse. These chemicals cross the gap or synapse and start a

similar electrical impulse in a dendrite of the next neuron. A similar synapse finally allows the delivery of such impulse from neurons to other cells such as muscles or glands. What is reflex action? Explain with an example. Define reflex arc. A. It is an accurate, unconscious, involuntary and instantaneous response to a stimulus. e.g.: Hand is withdrawn when it accidentally touches a hot object. The pathway taken by a stimulus to travel from receptor organ to effector organ is known as reflex arc. Schematic pathway: STIMULUS  RECEPTOR ORGAN  (sensory neuron)  SPINAL CORD  (motor neuron)  EFFECTOR ORGAN  RESPONSE Advantages of Reflex Action: 1) enables the body to give quick responses to harmful stimuli, thus protecting the body. 2) Minimises overloading of brain. 3) Efficient way of functioning in the absence of true thought processes. Types of nerves: A nerve is formed by the union of several nerve fibres. Nerve fibres are axons and they are enveloped by a covering made of lipid. Based on the property of nerve fibres, the nerves are classified into several types. Sensory Nerve: it is formed by the union of sensory nerve fibres. It carries sensory impulses from the receptors to brain or spinal cord. Motor Nerve: It is formed by the union of motor nerve fibres.It carries motor impulses from brain or spinal cord to different parts of the body.

What’s the role of control and coordination in an organism? A. Multicellular organisms consists of a number of components i.e. organs or tissues, each specialised to perform a particular function. Most activities need simultaneous and sequential functioning of number of organs e.g. feeding- 1. Eyes locate food. 2. Nose smells it. 3. Hands pick up food 4. Mouth opens to receive food 5. Teeth and muscle masticates food. 6. Saliva moistens the food. 7. Tongue perceives taste and pushes crushed food. All these work is possible through a system of control and coordination. What is a synapse? What happens at a synapse between two neurons? A Synapse is a gap between two neurons. At the end of the axon the electrical impulse sets off the release of some chemicals. These chemicals cross the gap or synapse and start a similar electrical impulse in a dendrite of the next neuron. What is the role of the brain in reflex action? Reflex actions take place without the conscious involvement of the brain. Quick responses are given through the governing centre i.e. spinal cord but the information is also sent to the brain. How are the brain and spinal cord protected? The brain is protected by the bony box – Cranium of the skull. The spinal cord is protected by the vertebral column. In addition to this, the brain and spinal cord are surrounded by membranes (meninges) which form a fluid filled area around the brain. This fluid is known as cerebrospinal fluid. This provides further shock absorption. How do animal muscles move?(How does nervous tissue cause action) The movements of muscle tissues are brought about by the contraction and relaxation of the contractile proteins in response to nerve impulses. When a nerve impulse reaches the muscle, at the cellular level, the electrical impulse causes the release of some chemicals at the neuro-muscular junction. In response to this chemical signal the muscle cells move by changing their shape so that they shorten. Muscle cells have special contractile proteins that change both their shape and arrangement in the cell in response to nervous electrical impulses. When this happens, a new arrangement of the proteins gives the muscle a shorter form causing movement of muscles. Parts of Nervous System: Central Nervous System: Consists of Brain and Spinal cord In animals, all life activities are under the control of the brain. Spinal cord controls the reflex actions and conducts messages between different parts of the body and brain. Peripheral Nervous System: Consists of nerves arising from the brain (Cranial nerves) and Nerves arising from the spinal cord (spinal nerves).It assists in transmitting information between central nervous system and rest of the body. Autonomous Nervous System: (Parasympathetic and sympathetic system)

Involuntary activities like breathing and beating of the heart take place by the coordinated efforts of the medulla oblongata and autonomous nervous system. Parts of Brain Cerebrum Forebrain

Midbrain Hindbrain

Has sensory areas, motor areas and areas of association. Centre of consciousness, thought, imagination, memory,analytical thinking. Awareness of vision, hearing, smell, taste, touch, heat etc. Control of voluntary actions. Hypothalamus Maintains homeostasis by regulating the body temperature, water level etc. Centre of thirst, hunger etc. Controls the secretion of pituitary hormones. Helps to maintain the normal constitution of blood. They contain the endings of the olfactory nerves (the first pair of cranial nerves) Olfactory and are concerned with the sense of smell. Lobes Acts as the coordinating centre between forebrain and hindbrain; also controls certain involuntary movements Responsible for precision and fine control of voluntary movements as well as Cerebellum maintaining posture and equilibrium of the body

Pons

Functions as the centre through which impulses travel to and from the cerebellum, spinal cord and other parts of the brain. Also regulates respiration

Medulla oblongata

Contains vital centres for controlling blood pressure, respiration, swallowing, salivation, vomiting, sneezing and coughing.

Types of movement by our body: Voluntary actions like walking, writing etc. Involuntary actions like beating of the heart and breathing Reflex actions

Mostly governed by the fore brain Controlled by mid brain and hind brain Controlled by spinal cord.

Coordination in Plants: Plants lack nervous and muscular system. Plants respond to stimuli by showing 2 types of movements – growth independent and growth dependent. Growth independent movements are usually quicker than growth dependent ones, and involve the use of electrochemical signals by the plant. To achieve this movement, the plant cells change shape by altering their water content.Eg. drooping of leaves of a touch-me-not plant when it is touched. Q-What happens when the leaves of a touch-me-not plant are touched? A-When the leaves of a touch-me-not plant are touched, the plant uses electrical-chemical means to convey this information from cell to cell. Plant cells at the leaf base change their shape by changing the amount of water in them. This results in folding and drooping of leaves. Growth dependent movements or tropic movements are slow, occurring either towards or away from the stimulus. The movement of plants in the direction of stimulus is known as 'tropism'. Tropic movements are shown in response to environmental factors such as light, gravity, water and chemicals. Plant roots are positively geotropic and negatively phototropic whereas plant shoots are usually negatively geotropic and positively phototropic. Pollen tubes show chemotropism by growing towards the ovules. Conduction of Information by electro-chemical means in Plants and Animals In Plants In Animals No specialised tissue for conduction of information Specialised tissue for conduction of information Cells change their shape by changing the amount of Cells change their shape due to the presence of water in them specialised proteins Movements due to growth: 1. Growth of tendrils: When a tendril comes in contact with a support, then the part of the tendril away from the support grows more rapidly than the part of the tendril that is in contact with the object, thus the tendril circles around the object and appears to cling to it. 2. Phototropism: Directional movement of a plant/plant part in response to light, for example: shoots show positive phototropism. 3. Geotropism: Directional movement of a plant/plant part in response to gravity, for example: roots show positive geotropism. 4. Chemotropism: Directional movement of a plant/plant part in response to chemicals, for example- growth of the pollen tube towards the ovule. 5. Hydrotropism: Movement of a part of a plant in response to water, for example: roots Plant hormones or phytohormones: These are chemical substances produced naturally by plants; they are capable of being translocated and regulate one or more physiological processes when present in low concentrations. Hormone Function Auxins They are released in response to light, promote cell elongation, also promote the development of seedless fruits. Gibberellins Growth of stem, seed germination, flowering. Cytokinins Cell division (in fruits and seeds) , breaking of seed dormancy Abscisic Acid Inhibits growth, promotes wilting of leaves. Ethylene Promotes fruit ripening processes. How is the movement of the leaves of the sensitive plant different from the movement of a shoot towards light? Leaves of the sensitive plant move very quickly in response to touch. There is no growth involved in this movement. The directional movement of shoot towards light is slow and is caused by growth. If it is prevented from growth, it will not show the movement. In the movement of the leaves of sensitive plant, the stimulus is touch. In phototropism, the stimulus is light. Also, in sensitive plant, the movement is caused by the sudden loss of water from the swellings at the base of leaves. In phototropism the bending is caused by unequal growth on two sides of the shoot.

Hormones in Animals: The hormones in animals are produced by the endocrine glands, and they too play an important role in control and coordination. Hormones are chemical substances that control and coordinate activities of living organisms and also their growth. The term hormone was introduced by Bayliss and Starling. Animal hormones do not bring about directional growth depending on environmental cues, but promote controlled growth in various areas to maintain the body design. The various endocrine glands in humans are hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid glands, thymus, pancreas, adrenal glands, ovary (in female) and testis (in males). Features and functions of hormones: 1. 2. 3. 4. 5.

They are secreted by the endocrine glands and are called ‘chemical messengers’. They are poured directly into blood stream as endocrine glands have no ducts of their own (ductless glands). They usually have their effect at sites different from the sites where they are made. They act on specific areas called target organs. Hormones coordinate body activities and growth They are released in minute quantities.

Hormone

Endocrine Gland

Growth Hormone Thyroxin

Pituitary Thyroid Gland

Adrenaline

Adrenal gland

Insulin Testosterone

Pancreas Testis

Oestrogen

Ovary

Function

Deficiency may cause

Regulates growth and development of body Controls carbohydrate, protein and fat metabolism Prepares the body to deal with emergency situations Regulates blood sugar levels Causes development of sexual organs and secondary sexual characteristics in males Causes development of sexual organs and secondary sexual characteristics in females

Dwarfism Goitre _ Diabetes _ _

How does our body respond to emergency situations like fight? In case of flight or fight reaction to an emergency situation, Adrenal glands  release adrenaline into blood i.The heart begins to beat faster resulting in supply of more oxygen to the muscles. ii. The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles. iii. The breathing rate increases because of the contraction of the diaphragm and the rib muscles. iv. All these responses together enable the body to be ready to deal with the situation.

Why are some patients of diabetes treated by giving injections of insulin? Insulin produced by the pancreas regulates the level of blood sugar glucose inthe blood. When a person’s pancreas does not produce enough insulin, blood sugar level rises, a disease called diabetes. Such diabetic patients are given injections of insulin so that the sugar level in the blood can be controlled.

Why is the use of iodized salt advisable? Iodine is important for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrates, proteins and fat metabolism in the body so as to provide the best balance for growth. If iodine is deficient in the diet, thyroxin cannot be produced and the thyroid gland at the neck swells, a condition called goiter. Use of iodized table-salt can provide the required amount of iodine in the diet.

Hormone regulation is mostly done by feedback mechanism. A good example of negative feedback is the hormone insulin. Insulin is a hormone that is made by the pancreas. Insulin is released by the pancreas when you eat glucose (a kind of sugar). The glucose goes from your stomach to the blood. The amount of glucose in the blood goes up. The pancreas sees this high glucose level. It makes insulin and releases it into the blood. Then the insulin goes through the whole body and tells cells to take glucose out of the blood. When cells take up glucose from the blood this makes the glucose level go down. The pancreas sees this and stops making insulin. When the pancreas stops sending this message (insulin), the cells in the body stop taking extra glucose out of the blood.So the negative feedback works to keep the blood glucose level normal. If glucose is high, the pancreas makes insulin. The insulin causes the glucose to fall. Then this lower level of glucose tells the pancreas to stop making insulin.

Difference between nervous and endocrine system: Nervous system Mode of communication Electrical impulses Speed of communication Very quick Can reach Only cells connected by nervous system Continuity Cannot continuously transmit impulses

Endocrine system Chemical compounds Slow All cells of the body Can act steadily and persistently