Cells tissues and homeostasis

• Cells


  Smallest functional unit in the body
• Cells


  • Can be grouped together to form tissues: muscle, blood, bone
  • Can be grouped together to form organs: heart, liver, stomach
• What do cells do?

  • Utilise glucose, water and oxygen to make energy (ATP)
  • Synthesise new substances: proteins, peptides, sugars, fats, DNA, RNA
  • Produce specialised substances
  • Secrete specialised substances
  • Differentiate to perform specialised tasks
  • Undergo movement
  • Grow and divide – pass on genetic material
• Cell Membrane


  • Protection
  • Regulation
  • Communication
  • Identity
• Transport Across the membrane

  • Passive transport
  • Diffusion
  • Facilitated diffusion
  • Osmosis
  • Active Transport
  • Sodium-potassium pump
  • Pinocytosis/Phagocytosis
• Organelles


  These are the component parts of each cell. Each has highly specialized structure to carry out very specific functions.
• Cell Specialisation


  Structure of cells becomes very specialized and linked to their function
• Main types of tissue

  • Epithelial (covering/ lining/ secreting)
  • Connective (protects/support)
  • Muscle (movement)
  • Nervous (control)
• Epithelial tissue


  • Covers and lines the body
  • Protects undelaying structures from dehydration and chemical and mechanical damage
  • Some epithelial tissues secrete and absorb substances
• Epithelial tissue


  • Mucous secreted from in the lining of respiratory tract
  • Enzymes secreted from the lining of the small intestines but also absorbs nutrients from food
• Connective tissue


  • Cells very tightly packed with minimal space between them
  • Cell usually lie on an inert (inactive) basement membrane
  • Can be in single layer (simple) or several layers (stratified)
• Connective tissue


  • Most common tissue in the body
  • Cells are separated from each other compared to the cells in epithelial tissue
  • Large amount of fluid present between the cells called Matrix
  • Protein fibres present in the matrix which may be semi solid or dense and rigid
  • Supporting network on which cells attach
  • Binding and structural support
  • Protection
  • Transport
  • Insulation
• Cells found in Connective Tissue

  • Fibroblasts - most common connective tissue cell, large, manufacture collagen and elastic fibres which provide structural support to throughout the body
  • Fat Cells (adipocytes) - adipose tissue
  • Macrophages - part of immune system, phagocytotic
  • Leukocytes - White blood cells to defend against infection
  • Mast Cells - Play a major role in release of histamine in response to external invaders
• Adipose tissue


  • Skin, heart, kidneys
  • Protects, energy reserve, reduces heat loss
• Loose connective Tissue


  • Randomly arranged protein fibres
  • Different types of cells
  • In and around most body structures
  • Strength ,elasticity, support
• Fibrous Connective tissue


  • Regularly arranged protein fibres (in rows)
  • Forms tendons & ligaments
  • Strong, withstands pulling
• Cartilage


  • Protein fibres, gel like ground substance, chondrocyte cells
  • Ends of long bones, nose, larynx, trachea, bronchi
  • Allows movement
• Muscle Tissue


  • Excitable cells – neurons
  • Non-excitable cells – glial cells
• Homeostasis


  The internal environment of the human body must be kept constant or within a narrow range
• What is maintained in homeostasis

  • Temperature
  • Water and electrolyte
  • pH
  • Blood Glucose levels
  • Blood and tissue oxygen and carbon dioxide levels
  • Blood pressure
• Physiological processes that maintain homeostasis are efficient and robust
• If change is excessive or rapid the homeostatic functions may fail
• Negative Feedback


  Body Temperature Regualron Example Removed
• Negative Feedback


  1. Stimulus

  2. Detector/Sensor

  3. Control

  4. Effector

  5. Response