chapter 5

• Vascular plants


  Plants that contain vascular tissue, which consist of cells joined into tubes that are specialised in transporting nutrients and water around the plants
• Plant tissues


  • Roots
  • Stem
  • Leaves
• Plant organs


  • Each organ is specialised for a specific function, therefore each organ has specialised cells to help carry out its function
• Leaf structure


  Where most of the photosynthesis of a plant occurs
• Leaf functions


  • Gas exchange with the environment
  • Defence against predators (herbivores such as insects)
  • Capturing sunlight for photosynthesis
  • Releasing heat
  • Water loss from the leaf to the environment via evaporation
• Key features of the leaf


  • Waxy cuticle to prevent water loss from the leaf
  • Stomata to regulate gas exchange and water loss
  • Palisade mesophyll are the site of photosynthesis and maximise absorption of light
  • Spongy mesophyll where most gas exchange takes place
  • Vascular bundles contain xylem and phloem
• Stem structure


  • Main functions include ensuring the plant is in the right position for photosynthesis to occur, elevate the plant so seeds can be dispersed by wind or pollinators, and in some cases photosynthesis
• Key features of the stem


  • Vascular bundles
  • Epidermis - controls gas exchange and waterproofs it
• Root structure


  • Main functions include anchoring the vascular plant to the soil, absorbing nutrients and minerals from the soil, absorbing water from the soil, and storing carbohydrates and other substances
• Digestive system


  Permits food to be digested, absorbed and excreted
• Main functions of the digestive system


  • Digestion - breaking down food so the body is able to absorb it
  • Absorption of nutrients - process where substances pass from the digestive tract into the blood stream where they can circulate around the body
  • Elimination of solid food waste - all remaining food that could not be digested and absorbed pass into the large intestine as waste, then eliminated from the body via the anus
• Structure of the digestive system


  • Mouth and salivary glands
  • Oesophagus
  • Stomach
  • Small intestine (duodenum, jejunum, ileum)
  • Large intestine
• Accessory organs of the digestive system


  • Liver
  • Gallbladder
  • Pancreas
• Pancreas


  Produces enzymes that are released into the small intestine via the duodenum, including amylase (breaks down carbohydrates), trypsin (breaks down proteins), and lipase (breaks down lipids). Also secretes hormones insulin and glucagon which regulate blood sugar level, and releases alkaline compounds to neutralise stomach acids.
• Liver


  Takes the raw materials absorbed by the small intestine and uses them to make key chemicals. Main roles include detoxification, storage, metabolism, bile production, and haemoglobin breakdown.
• Gallbladder


  Stores and concentrates bile produced in the liver, and then secretes it into the small intestine via the bile duct.
• Excretory system


  Helps to maintain water balance as well as excrete nitrogen and other toxic waste products from the body to the external environment.
• Main functions of the excretory system


  • Remove nitrogenous waste
  • Remove excess water to maintain water balance in cells and tissues
• Kidneys


  Function by filtering blood and removing waste materials and toxic substances, as well as providing water balance.
• Key components of the kidney

  • Renal artery - carries blood from the heart to the kidney
  • Renal vein - carries blood from the kidney to the heart
  • Renal cortex - contains the glomerulus, proximal and distal convoluted tubules
  • Renal medulla - contains the loop of Henle and collecting tubule
  • Renal pelvis - functions as a pathway for the urine before it moves to the bladder
  • Ureter - carries the urine from the renal pelvis to the bladder
• Nephron


  Key component of the kidney, with roles including filtering blood and removing toxic and waste products, as well as reabsorbing nutrients. Each kidney contains 1 million nephrons.
• Components of the nephron


  • Glomerulus - a ball of capillaries where the blood arrives to be filtered
  • Bowman's capsule - surrounds the glomerulus, where the filtrate is formed
  • Proximal tube - absorbs water, sodium and glucose back into the blood
  • Loop of Henle - long tube where reabsorption of water and salt takes place
  • Distal tubule - further reabsorption of sodium and water
  • Collecting tubule - more water and salt is absorbed, concentrating the filtrate into urine
• Endocrine system


  A system made up of glands responsible for making and secreting hormones, which work to regulate bodily functions and maintain homeostasis.
• Main functions of the endocrine system


  • Receive signals from the nervous system
  • Release hormones into the blood stream
  • Control and maintain processes like osmoregulation, blood glucose levels, metabolism, adrenaline response, sexual development, growth and development, emotions
• Structure of the endocrine system


  • Hypothalamus
  • Pituitary gland
  • Thyroid gland
  • Adrenal gland
  • Pancreas
  • Ovaries/Testes
• Hormones


  Chemical messengers released by cells of endocrine glands that travel in the blood stream to target cells to stimulate a response. Involved in negative feedback to maintain homeostasis.
• Types of hormones


  • Peptides
  • Proteins
  • Steroids
• Common human hormones


  • Anti-diuretic hormone (ADH)
  • Thyroid stimulating hormone (TSH)
  • Thyroxine
  • Adrenaline
  • Glucagon
  • Insulin
  • Oestrogen
  • Testosterone
• Steroid hormone signal transduction


  Steroid hormones are hydrophobic and lipid soluble, so they can diffuse through the cell membrane and bind to receptors inside the cell.
• Protein and peptide hormone signal transduction


  Protein and peptide hormones are hydrophilic and not lipid soluble, so they cannot diffuse through the cell membrane. Instead, they bind to receptors on the surface of the cell membrane.
• Homeostasis


  Allows the body's internal environment to remain relatively constant despite internal and external environmental factors.
• Homeostatic processes


  • Blood glucose levels
  • Temperature
  • Water balance
• Stimulus response model


  Allows the body to respond appropriately to internal or external changes in its environment. When a stimulus is detected, a bodily response is initiated to return the body back to homeostasis.
• Feedback loops


  Regulate the physiological systems. Processes where outputs influence inputs, creating continuous cycles of assessment and adjustment, essential for learning and improvement.
• Negative feedback


  Feedback loops that decrease the magnitude of a process in response to the feedback from the end product.
• Negative feedback examples


  • Blood-glucose levels
  • Thermoregulation (temperature regulation)
  • Osmoregulation (water balance)
• Positive feedback


  Feedback loops that increase the magnitude of a process in response to its end product.
• Positive feedback example


  • Stretching of the cervix during childbirth causes the release of oxytocin and uterine contractions, which then cause further stretching, oxytocin release and additional contractions.
• Vascular plants


  Plants that contain vascular tissue, which consists of cells joined into tubes that are specialised in transporting nutrients and water around the plants
• Plant tissues


  • Roots
  • Stem
  • Leaves