Chapter 22 Chemical Coordination And Integration
ENDOCRINE GLANDS AND HORMONES
Endocrine glands lack ducts and are hence, called ductless glands. Their secretions are called hormones. Hormones are non-nutritional chemicals which act as intercellular messengers and are produced in trace amounts.
The endocrine system is composed of hypothalamus, pituitary and pineal, thyroid, adrenal, pancreas, parathyroid, thymus and gonads.
The pituitary gland is divided into three major parts:
The pineal gland secretes melatonin which plays a very important role in the regulation of 24 hour rhythms of our body (e.g. rhythms of sleep and state of being awake).
The thyroid gland hormones play an important role in the regulation of the basal metabolic rate, development and maturation of the central neural system, metabolism of carbohydrates, proteins and fats, menstrual cycle.
The thymus gland secretes thymosins which play a major role in the differentiation of T-lymphocytes, which provide cell immunity. Thymosins also increase the production of antibodies to provide humoral immunity.
The adrenal gland is composed of the centrally located adrenal medulla and the outer adrenal cortex. The adrenal medulla secretes epinephrine and norepinephrine. These hormones increase alertness, pupillary dilation, sweating, heartbeat, etc. The adrenal cortex secretes glucocorticoids and mineralocorticoids.
The endocrine pancreas secretes glucagon and insulin. Glucagon stimulates glycogenolysis and gluconeogenesis resulting in hyperglycemia. Insulin stimulates cellular glucose uptake and utilization and glycogenesis resulting in hypoglycemia. Insulin deficiency and/or insulin resistance result in a distance called diabetes mellitus.
The testis secretes androgens, which stimulates the development, maturation and functions of the male accessory sex organs, appearance of the male secondary sex characters, spermatogenesis, male sexual behaviour, etc.
The ovary secretes estrogen and progesterone. Estrogen stimulates growth and development of female accessory sex organs and secondary sex characters. Progesterone plays a major role in the maintenance of pregnancy as well as in mammary gland development and lactation.
The atrial wall of the heart produces atrial natriuretic factor which decreases the blood pressure.
Kidney produces erythropoietin which stimulates erythropoiesis.
The gastrointestinal tract secretes gastrin, secretin, cholecystokinin and gastric inhibitory peptide. These hormones regulate the secretion of digestive juices and help in digestion.
Coordination is the process through which two or more organs interact and complement the functions of one another.
The neural system of all animals is composed of highly specialized cells called neurons which can detect, receive and transmit different kinds of stimuli.
HUMAN NEURAL SYSTEM
The human neural system is divided into two parts:
The brain can be divided into three major parts:
Chapter 20 Locomotion and Movement
The voluntary movements that result in a change of place or location are called locomotion.
TYPES OF MOVEMENTS
Muscle is a specialized tissue of mesodermal origin. They have properties like: excitability, contractility, extensibility and elasticity.
There are three types of muscles present in our body:
Repeated stimulation of muscles leads to fatigue. Muscles are classified as Red and White fibres based primarily on the amount of red coloured myoglobin pigment in them.
Bones and cartilages constitute our skeletal system. The skeletal system is divisible into axial and appendicular. Skull, vertebral column, ribs and sternum constitute the axial skeleton. Limbs bones and girdles form the appendicular skeleton. Three types of joints are formed between bones or between bone and cartilage- fibrous, cartilaginous and synovial. Synovial joints allow considerable movements and therefore, play an important role in locomotion.
Chapter 19 Excretory Products And Their Elimination
Many nitrogen containing substances, ions, CO2, water, etc. that accumulate in the body have to be eliminated. Nature of nitrogenous wastes formed and their excretion vary among animals, mainly depending on the habitat. Ammonia, urea and uric acid are the major nitrogenous wastes excreted.
HUMAN EXCRETORY SYSTEM
In humans, the excretory system consists of one pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
Each kidney has over a million tubular structures called nephrons. Nephron is the functional unit of kidney and has two portions- glomerulus and renal tubule. Glomerulus is a tuft of capillaries formed from arterioles, fine branches of renal artery.
The renal tubule starts with a double walled Bowman’s capsule and is further differentiated into a Proximal Convoluted Tubule (PCT), Henle’s Loop (HL) and Distal Convoluted Tubule (DCT). The DCTs of many nephrons join to a common collecting duct many of which open into the renal pelvis through the medullary pyramids. The Bownam’s capsule encloses the glomerulus to form Malpighian or renal corpuscle.
Urine formation involves three processes i.e. filtration, reabsorption and secretion. Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure. About 1200 mL of blood is filtered by the glomerulus per minute to form 125 mL of filtrate in the Bowman’s Capsule per minute. This is known as the Glomerular Filtration Rate (GFR).
A counter current mechanism operates between the two limbs of the loop of Henle and those of vasa retca (capillary parallel to Henle’s Loop). The filtrate gets concentrated as it moves down the descending limb but is diluted by the ascending limb. Electrolytes and urea are retained in the interstitium by this arrangement. DCT and collecting duct concentrate the filtrate about four times which is an excellent mechanism of conservation of water.
Urine is stored in the urinary bladder till a voluntary signal from CNS carries out its release through urethra.
In addition to this, the skin, lungs and liver also assist in excretion.
CHAPTER 18 BODY FLUIDS AND CIRCULATION
Blood is a special connective tissue consisting of fluid matrix, plasma and formed elements.
Heart has two atria and two ventricles. Cardiac musculature is auto-excitable. Sino-atrial Node (SAN) generates the maximum number of action potentials per minute and therefore sets the pace of activities of the heart. Hence, it is known as the pacemaker. The action potential causes the atria and the ventricles to undergo contraction (systole) followed by their relaxation (diastole). The systole forces the blood out of atria to the ventricles and to the pulmonary artery and the aorta. About 70 mL of blood is pumped out by each ventricle during a cardiac cycle and it is known as the stroke or beat volume.
We have a complete double circulation i.e. two circulatory pathways, namely, pulmonary and systemic are present. The pulmonary circulation starts with the pumping of deoxygenated blood by the right ventricle which is carried out to the lungs where it is oxygenated and returned to the left atrium. The systemic circulation starts with the pumping of oxygenated blood by the left ventricle to the aorta which is carried to all the body tissues and the deoxygenated blood from there is collected by the veins and returned to the right atrium
CHAPTER 17 BREATHING AND EXCHANGE OF GASES
Cells utilize oxygen for metabolism and produce energy along with substances like carbon dioxide. Humans have a well-developed respiratory system comprising of two lungs and associated air passages to perform respiration.
The first step in respiration is breathing by which atmospheric air is taken in and the alveolar air is released out. Exchange of O2 and CO2 between deoxygenated blood and alveoli, transport of these gases throughout the body by blood and tissues and utilization of O2 by the cells are the other steps involved.
Oxygen is transported mainly as oxyhaemoglobin. O2 gets bound to haemoglobin and is easily dissociated in the target tissues.
Respiratory rhythm is maintained by the respiratory centre in the medulla region of the brain. A pneumotaxic centre in the brain and a chemosensitive area in the medulla can alter respiratory mechanism.
Chapter 16 Digestion And Absorption
The digestive system of humans consists of an alimentary canal and associated digestive glands.
The alimentary canal consists of the mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.
The accessory digestive glands include the salivary glands, the liver and the pancreas.
Inside the mouth, the teeth masticate the food, the tongue tastes the food and manipulates it for proper mastication by mixing it with the saliva. Saliva contains a starch digestive enzyme, salivary amylase that digests the starch and converts it into maltose (disaccharide).
The food then passes into the pharynx and enters the oesophagus in the form of bolus. It is further carried down through the oesophagus by peristalsis into the stomach.
In stomach, mainly protein digestion takes place. Simple sugars, alcohol and medicines are also absorbed in the stomach.
The food enters into the duodenum portion of the small intestine and is acted on by the pancreatic juice, bile and finally by the enzymes in the succus entericus, so that the digestion of carbohydrates, proteins and fats is completed. The digested end products are absorbed into the body through the epithelial lining of the intestinal villi.
The undigested food enters into the caecum of the large intestine. Most of the water is absorbed in the large intestine. The undigested food becomes semi-solid in nature and then enters into the rectum, anal canal and is finally ejected through the anus.
CHAPTER 15 PLANT GROWTH AND DEVELOPMENT
Growth can be defined as an irreversible and permanent increase in size of an organ or its parts or even of an individual cell.
PHASES OF GROWTH IN PLANTS
The increased growth per unit time is termed as growth rate.
Plant growth and development are under the control of both intrinsic and extrinsic factors.
Intercellular intrinsic factors are the chemical substances, called plant growth regulators (PGR). There are diverse groups of PGRs in plants, principally belonging to 5 groups: auxins, gibberellins, cytokinins, abscsic acid and ethylene. These PGRs are synthesized in various parts of the plants.
Plant growth and development is also affected by external factors like light, temperature, nutrition, oxygen status, gravity, etc.
Flowering in some plants is induced only when exposed to certain duration of photoperiod. Depending on the nature of photoperiod requirements, the plants are called short day plants, long day plants and day-neutral plants. When plants are exposed to low temperature as to hasten flowering later in life, it is known as vernalization.
CHAPTER 14 RESPIRATION IN PLANTS
Plants do not have any special systems for breathing or gaseous exchange. Stomata and lenticels allow gaseous exchange by diffusion.
The breaking of C-C bonds of complex organic molecules by oxidation cells leading to the release a lot of energy is called cellular respiration. Glucose is the favoured substrate for respiration. Fats and proteins can also be broken down to yield energy.
The initial stage of cellular respiration takes place in the cytoplasm. Each glucose molecule is broken through a series of enzyme catalyzed reactions into two molecules of pyruvic acid. This process is called glycolysis.
Pyruvic acid is transported into the mitochondria where it is converted into acetyl CoA with the release of CO2. Acetyl CoA then enters the tricarboxylic acid pathway or Kreb’s cycle operating in the matrix of the mitochondria.
The respiratory pathway is an amphibolic pathway as it involves both anabolism and catabolism. The respiratory quotient depends upon the type of respiratory substance used during respiration.
CHAPTER 13 PHOTOSYNTHESIS IN HIGHER PLANTS
Green plants make their own food by the process of photosynthesis. During this process, carbon dioxide from the atmosphere is taken in by leaves through stomata and used for making carbohydrates.
Photosynthesis takes place only in the green parts of the plants, mainly the leaves. Within the leaves, the mesophyll cells have a large number of chloroplasts that are responsible for carbon dioxide fixation. Photosynthesis has two states:
The light reaction
In the light reaction, the light energy is absorbed by the pigments present in the antenna, and funneled to special chlorophyll. There are two photosystems: PSI and PSII. The PSI has a 700 nm absorbing chlorophyll while PSII has a 680nm absorbing chlorophyll. After absorbing light, electrons are excited and transferred through the two photosystems and finally to NAD forming NADH.
Carbon Fixation cycle
In the carbon fixation cycle , CO2 is added by the enzyme BuBisCO, to a 5-carbon compound RuBP that is converted to 2 molecules of 3-carbon PGA. This is then converted to sugar by the Calvin cycle, and the RuBP is regenerated. During this process ATP and NADPH synthesized in the light reaction are utilized. RuBisCO also catalyses a wasteful oxygenation reaction- photorespiration.
FACTORS AFFECTING PHOTOSYNTHESIS