CONTROL CONTR OL AND COORDIDIN ORDI DINATION ATION
COORDINATION IN PLANTS The function of control and coordination in plants is performed by certain chemical substances known as plant hormones or phytohormones. 1AUXINS i) Promote cell division,and growth of root and shoot tips. ii) Control apical dominance. iii)Promote fruit growth and development of seedless fruits. iv) Photoperiodism is controlled by auxins. GIBBERELLINS i) Promote stem elongation ii) Control seed germination and flowering. iii) The maximum amount of gibberellins is found fruits and seeds. CYTOKININS i) Promote cell division ii)They are found in maximum concentration in dividing cells. iii) Promote seed germination iv) Help in breaking seed dormancy v) Delay ageing in leaves and control stomatal opening ABSCISIC ACID i) It is agrowth inhibitor ie its function is opposite to that of auxins,gibberellins and cytokinins ii) It helps in closure of stomata PLANT MOVEMENTS Plants show various movements like twisting ,bending and coiling in response to external stimuli.Bending of a plant in response to a stimulus is called tropism. STIMULUS It is the change in the external or internal environment of an organism that provokes a physiological physiological and and behavioura behaviourall response response in the the organism. organism. 1.TROPIC MOVEMENTS MOVEMENTS The response of an organism in the direction of the stimulus or away from it is known as a tropic movement. a) Phototropism – It is the response of a plant to light. If the plant parts grow towards light source,this is called positive phototropism. If the plant parts grow away from light source it is called negative phototropism. Geotropism – It is the tropic response of plants to gravity. The shoot or the stem tip of aplant shows negative geotropism as it grows away from the pull of gravity. Shoots which are negatively geotropic grow vertically. vertically. This lifts the leaves and flowers above the ground and helps the plant to compete for light and carbon dioxide. Positive geotropism in roots By growing towards gravity,roots penetrate the soil which is their mans of anchorage and their source of water and mineral salts. Lateral roots are not positively geotropic they grow at right angle or slightly downwards from the main root. This diageotropism of lateral roots enables a large volume of soil to be exploited and helps to anchor the plant securely. Hydrotropism –It is the response of plants to water.
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Chemotropism – It is the response of plants to chemical stimuli. 2.NASTIC MOVEMENT Some movements which are triggered by astimulus are not affected by the direction of stimulus.ie the movements are neither towards nor away from the stimulus . These are called nastic movements.Nastic movements are non-directional in nature. An example of a nastic movement is shown by the mimosa plant commonly called touch- me –not. The leaflets of this plant fold in response to astimulus of touch.This type of nastic movement is called thigmonasty or haptonasty.Opening and closing flowers to the intensity of light is called photonasty. COORDINATION IN ANIMALS Nervous system It is the system of conducting tissues that receives the stimulus and transmits to other parts of the body forming anetwork. FUNCTIONS OF THE NERVOUS SYSTEM i)It regulates involuntary actions. ii)It controls and coordinates involuntary muscular activities. iii)It keeps us informed about the outside world through sense organs. iv) It enables us to think reason and remember. v)It controls all the reflex actions in our body ,thus protecting it from harm. Receptor A receptor is a cell which is sensitive to a particular type of stimulus while the part of the body that responds to the stimuli is called an effector. The receptor collects information about changes in the environment of the animal and pass this information to the central nervous system in the form of electrical impulses are analysed and the animal responds to the changes through effector organs such as muscles and glands. These organs receive information through motor neurons and give suitable responses like muscle contraction,relaxation secretions etc. UNIT OF NERVOUS SYSTEM The units which make up the nervous system are called nerve cells or neurons. So ,neurons are the structural and functional unit of nervous system. Neuron is the largest cell in the body. Neuron carry messages in the form of electrical signals called nerve impulses. Neuron is an elongated branched cell having three components – cell body, dendrites and axon. SYNAPSE It is the junction between two adjacent neurons or nerve cells ie between the axon ending of one and the dendrites of the next. Nerve Impulse - It is the information in the form of chemical and electrical signals passing through neurons. These impulses are carried by dendrites towards the cell body. NEUROMUSCULAR JUNCTION It is the point where a muscle fibre comes in contact with a motor neuron carrying nerve impulses from the central nervous system. T he impulses travel from the neuron to the muscle fibre by means of a neurotransmitter in the same way as the transmission of impulses across a synapse between two neurons. Transmission of nerve impulse The information acquired at the end of the dendrite tip of aneuron sets off a chemical reaction which creates an electrical impulse. This impulse travels from the dendrirte to
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the cyton along the axon to its end. At the end of the axon ,the electrical impulse sets off the release of some chemicals ,which cross the synapse and start asimilar electrical impulse in a dendrite of the next neuron. In this way nerve impulse travel in the body. REFLEX ACTION A reflex action is defined as a spontaneous automatic and mechanical response to a stimulus which is controlled by the spinal cord.eg knee jerk, blinking, sneezing, coughing,yawning, hiccups,salivation at the sight of the food. REFLEX ARC The pathway followed by the different sensory and motor nerves in a reflex action is called reflex arc. MECHANISM OF REFLEX ACTION i)Receptor organs like skin perceives the stimulus and activates a sensory nerve impulse. ii) Sensory organs carries message in the form of sensory impulse to the spinal cord. iii) The spinal cord acts as modulator .The neurons of spinal cord transmit the sensory nerve impulse to the effectors like leg muscles which responds by pulling back the organ away from the harmful stimulus. Advantages of reflex action i)It enable the body to give quick responses to harmful stimuli and thus protects our body. ii) It minimizes the overloading of brain. CENTRAL NERVOUS SYSTEM It is made up of 100 billion nerve cells. It is situated in the cranial cavity. It is covered by amembrane known as meninges.The space between the meninges and also the cavities in the brain are filled with afluid called cerebrospinal fluid.This fluid reduces friction,absorbs shockand also lessens the weight by providing buoyancy.It provides CNS with nutrients and hormones. Brain is divisible into three major divisions,forebrain,midbrain,and hind brain. FORE BRAIN – This is the front part of the brain divided into cerebrum,olfactory lobes and diencephalons. Olfactory lobes are the centers of smell in the form of a pair of small bodies. Cerebrum is the largest part of brain. It consist of right and left cerebral hemisphere. The cerebrum is the seat of thinking,reasoning,learning and intelligence. For each type of stimulus there are specific regions which process them.Parietal lobe is for pain,touch,temperature,and conscious association.Occipital lobe for visual reception,temporal lobe for auditory reception. Diencephalon – It posses control centres for hunger,sleep,thirst and body temperature etc. Mid brain – Connects the fore brain to hind- brain . It controls reflex movements of the head ,neck and trunk in response to visual and auditory stimulus. Hind brain – It consist of cerebellum,medulla oblongata and pons. Cerebellum maintains balance,equilibrium and posture. It tunes the body movements by making them smooth,steady and regulated like riding a bicycle walking straight etc. Pons regulate respiration.Medulla oblongata controls reflex actions such as swallowing,sneezing,coughing,vomiting,heart beat and breathing.
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SPINAL CORD It is a cylindrical structure that extends from the medulla oblongata . It is enclosed within the vertebral column and covered by meniges. It conducts sensory and motor impulses to and from the brain.It also controls the reflex actions . PERIPHERAL NERVOUS SYSTEM The communication between the central nervous system and the other parts of the body is facilitated by a special nervous system.It mainly consist of nerves that are of two types. 1.Cranial nerves – These are the ones that arise from different parts of the brain. 2. Spinal nerves – These are 31 pairs arising from each segment of the spinal cord. AUTONOMIC NERVOUS SYSTEM means self governing nervous system. Autonomic nervous system is called visceral nervous system. It lies outside and parallel to CNS. ANS consist of a pair of chain of nerves and ganglia found on both side of the vertebral column. The autonomic nervous system can be classified into sympathetic and parasympathetic nervous system. Autonomous nervous system controls the internal functions of the body ,such as heart beat ,gut movement etc.Sympathetic and parasympathetic systems, work antagonistic to each other eg the sympathetic system speeds heart rate and the parasympathetic system slows it. The Endocrine system There are special chemicals which regulate the physiological processes in animals. They are known as hormones and are secreted by ductless glands, called endocrine glands directly into the blood. Characteristics of hormones They are released directly into the blood or lymph and are carried to the target organ. They are produced as chemical messengers in trace amounts. Hormones are specific in nature ie they act on particular target organ. Their activity can cause widespread effects on the body. Difference between endocrine and exocrine glands Endocrine glands 1. These lack ducts, thus called ductless glands. 2. Secretions are directly passed into the blood stream. 3.The site of action is far away from the gland. 4.Endocrine secretions are called hormones Exocrine glands 1. These have ducts 2.Secretions are discharged into body cavities or ducts. 3.The site of action is just near the gland. 4.Exocrine secretions are called enzymes.
GLAND
POSITION
HORMONE
RESPONSE OF BODY
ABNORMAL FUNCTIONS
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Thyroid
Neck
Thyroxin
Controls basic metabolism and growth rate.
Islets of Langerhans
Pancreas
Insulin
Controls balance of sugar in the blood. Controls response for fight or flight,ie increased heart beat,increased blood sugar,dialates coronary artery,dialates pupil,etc. Controls growth of uterus, secondary sexual characters. Development of secondary sexual characters.
Adrenal gland
Ovary
Testis
Pituitary
Attached to kidneys
Adrenalin
Dorsal abdominal wall In the scrotum
Oestrogen
Beneath the brain
Growth hormones
Testosterone
Deficiency causes dwarfism and mental retardation in childhood.Over production causes increased metabolism. Deficiency results in diabetes mellitus.
Deficiency causes delay of appearance of these changes.
Deficiency causes delay or lack of development of these changes. Controls the growth of Deficiency causes bones and muscles dwarfism and over production causes gigantism.
There are some glands that are both exocrine and endocrine in nature. These glands are called heterocrine glands. Where the exocrine secretion is sent through ducts while endocrine secretions are discharged straight away into the blood. Pancreas secretes pancreatic juice as exocrine secretion helpful in digestion and insulin and glucagons as endocrine secretion that regulate glucose content in the blood. Ovaries produce female gametes called ova and secrete hormones estrogen and progesterone as its endocrine secretion. Testes produce male gametes called sperms and male hormone called testosterone. COMPARISON OF SPINAL REFLEX AND VOLUNTARY ACTION SPINAL REFLEX VOLUNTARY ACTION Stimulus affects external or internal Initiated from the brain at the conscious receptor. level. Spinal cord only involved- not under the Forebrain involved under the control of will. control of will. The impulse travels from the brain down the The impulse travels only up or down the spinal cord. spinal cord. The path of nerve impulse is much longer. The path of nerve impulse is by the The response can be delayed. shortest route. The response is in skeletal muscle only. The response is immediate. The response is in the skeletal or internal Voluntary muscle
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