Biology 1

• The process of removal of chemical wastes from the body is called excretion.
• CO2 is eliminated through lungs and extra water is released in the form of sweat.
• Breakdown products of haemoglobin of dead rbcs is called bile pigments.

  The liver cells extract it from the circulation and secrete it into the bile juice poured into the duodenum through bile duct.
• Excretory organs :-

  1. Kidney eliminate nitrogenous wastes from the blood and throw it out from the body in the form of urine.
  2. Sweat is excreted by the sweat glands of the skin.
  3. Lungs excrete CO2 from the body through expired air.
  4. Liver detoxifies ammonia by converting it to urea. Urea is excreted through urine.
• Kidney :-

  1. Two bean shaped organs located in either side of the backside and protected by the last two ribs. A tube, the ureter, arises from the hilum connects behind with the urinary bladder.
  2. The front end of the ureter is expanded into the kidney and is called pelvis. The urine produced in the kidneys collects in the urinary bladder to the outside of the body through urethra
  3. A sphincter guards the opening in the bladder into the urethra and relaxed only at the time of urination (micturition)
• Longitudinal section of kidney :-

  1. outer dark cortex
  2. Inner lighter medulla Medulla is composed of striped substance arranged in several conical pyramids. Apex of each pyramid is called papilla.
• Kidney is composed of an enormous number of minute tabules called nephrons.

  The outer concavity of bowmans capsule lodges a knot like mass of blood capillaries called glomerulus.

  Proximal convoluted tubule (pct, starting convoluted region)

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  Loop of henle (shaped like a hair pin)

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  Distal convoluted tubule (Dct, ending convoluted region)
• Production of urine involves ultrafiltration where blood flows through the glomerulus under great pressure, this filtration is called ultrafiltration.
• The fluid entering the renal tubule is called glomerular filtrate which consists of salts, glucose, water, urea, etc.
• Reabsorption is the process where the glomerular filtrate entering the renal tubule is not urine, it's an extremely dilute solution containing lots of useful minerals.
• The normal concentration of blood is not disturbed during reabsorption, this is called selective absorption.
• Tubular secretion is a process where certain substances are passed into the forming urine, this passage involves activity of cells of tubular walls so it's called tubular secretion.
• Diseases when stuff like these are found in urine :-

  1. Blood cells = haematuria
  2. Glucose= glycosuria
  3. Albumin= Albuminuria
  4. Bile pigment = anemia, hepatitis etc
  5. Increased production of urine = diuresis
• Urine is yellow in colour due to a pigment called urochrome

  Adh full form is antidiuretic hormone
• 1. The kidney while removing wastes from the blood also regulates it's composition. It's called osmoregulation. (Regulation due to osmotic pressure)
  2. If one kidney is damaged or removed for some reason, the other kidney is sufficient for functioning properly. Artificial kidney is a dialysis machine.
• Nervous system includes

  1. Brain
  2. Spinal cord
  3. Sense receptors
  4. Nerves Brain and spinal cord is made up of neurons or nerve cells.
• Structure of neuron:-

  1. Perikaryon or cyton contains a well defined nucleus surrounded by granular cytoplasm.
  2. Centrosome is absent in cyton cuz nerve cells have lost the ability to divide.
  3. Dendrites are branches cytoplasmic projections of the body. They conduct nerve impulses to the cyton.
  4. Axon is surrounded by myelin sheath which is covered by neurolemma.

  The gap in myelin sheath is called node of ranvier.
• There are 2 types of nervous system

  1. Central nervous system (cns) consists of brain, spinal cord, and vertebral column
  2. Peripheral nervous system (pns) consists of nerves that emerge from and enter into the brain and spinal cord. Ex - cranial and spinal nerves
• 1. Cranial nerves emerge from the brain and has 12 pairs.
  2. Spinal nerves emerge from the spinal cord and has 31 pairs.
• PNS consists of 2 types of nervous system:-

  1. Somatic nervous system which conveys information to voluntary muscles.
  2. Automatic nervous system includes pair of chains of ganglia and nerves that controls the involuntary actions of many internal organs.
• Brain is well protected inside the cranium of the skull.

  It is protected by 3 coverings called meninges which continue backwards on the spinal cord.

  Inflammation of meninges is called meningitis.
• 3 layers that protects brain :-

  1. Dura mater (outermost tough membrane)
  2. Arachnoid (thin delicate middle layer giving web like cushion)
  3. Pia mater (innermost highly vascular membrane, richly supplied with blood)
• Cerebrum is divided into two halves called cerebral hemispheres. Each cerebral hemisphere is hollow inside and have two regions called cortex and medulla

  1. Cortex - contains cell bodies of neurons and is greyish in colour so it's called grey matter.
  2. Medulla - is white due to axons so is called white matter.

  Function - cerebrum is a seat of consciousness, intelligence, will power,  voluntary actions etc.
• Location of cerebellum - just at the base and under the large cerebrum.

  Cerebrum has white matter at the centre which appears like a branching tree, in a median section.

  Function - maintaining balance of the body and coordinate muscular activity.
• Location of medulla oblongata - base of the skull

  Function - controls the activities of internal organs
• Three primary regions of brain :-

  1/ forebrain : cerebrum, diencephalon, thalamus (relays pain and pressure impulses to cerebrum), hypothalamus (controls body temperature and pituitary gland)

  2/ mid brain : reflexes involving eyes and ears

  3/ hind brain : cerebellum, pons (carries impulses on hemisphere of cerebellum to the hemisphere and coordinates muscle movements on both sides of the body.)
• Spinal cord has a small central canal in the centre and is the largest nerve of the body.
• Functions of spinal cord - reflexes below the neck, conducts sensory impulses from the skin and muscles to the brain, conducts motor responses from the brain to muscles of the trunk and limbs.
• Reflexes :-

  1. Initiated by some stimulus
  2. Commands originate mostly in spinal cord and autonomic nervous system and few in the brain as well
  3. Involves muscles and glands.
• Voluntary actions -

  1. Initiated by a willing thought
  2. Commands originate in brain
  3. Involves only muscles.