cell biology and tissues

• Nucleus


  • An organelle found in eukaryotic cells
  • The 'brain to the cell'
  • Largest structure in the cell
  • Surrounded by the nuclear membrane, two layers and like the cell membrane is selectively permeable
  • The protoplasm within the nucleus is called nucleoplasm
  • Inside the nucleus is found the genetic material, consisting principally od deoxyribonucleic acid (DNA)
• Chromatin


  When the cell is not reproducing, the genetic material is a threadlike mass
• Chromosomes


  Before cell division, the chromatin shortens and coils into rod-shaped bodies
• Nucleosome


  The basic structural unit of a chromosome - composed of DNA and proteins
• DNA


  Has 2 primary functions - genetic blueprint to ensure next generation of cells in identical to existing ones, and provides the plans for synthesis of protein by the cell
• Genes


  All this information is stored in the genes
• Nucleoli


  Small spherical bodies inside the nucleus responsible for the production of ribosomes and ribosomal ribonucleic acid (rRNA)
• Endoplasmic reticulum (Rough and Smooth)


  • Forms channels called cisternae which divides the cytoplasm into compartments
  • Primary function is the transport of proteins
• Golgi apparatus

  • Membranous tubes and elongated sacs – actually flattened cisternae stacked together
  • Concentrates and packages some of the substances that are made in the cell
• Mitochondria


  • Power houses of the cell – intense metabolic activity
  • Produces ATP by converting the chemical energy contained in molecules of food
  • Three membranes. Inner membrane- folds to increase surface area available for chemical reactions
• Ribosome


  Translates MRNA (the information from DNA) into proteins
• Lysosomes


  • Breaks down macromolecules within the cell due to the enzymes contained within the cell
• Cell Membrane


  • Regulates water, nutrients and waste products
  • Bilayer of phospholipid molecules
  • Fatty molecules with hydrophilic head and hydrophobic tails
• Plasma Membrane Proteins (PMP)


  Integral or Peripheral PMP for transportation of materials in and out of the cell
• Cytoplasm


  • Chemically cytoplasm is 75-90% water plus solid compounds
  • Breaks down raw materials from external environment and converts them into usable energy by decomposition reactions
  • New substances are synthesised for the use by the cell
  • Various chemicals are packaged for transport to other parts of the cell or to other cells in the body
  • Within the cytoplasm, various chemicals facilitate the excretion of waste materials
• Cytoskeleton

  • Provides support and shape to a cell
  • Helps the structures within the cell change shape and move
• Endocytosis


  The intake of extracellular fluid and particulate material ranging in size from macromolecules to whole cells
• Exocytosis


  The bulk transport of materials out of the cells
• Osmosis


  Water travels through a selectively permeable membrane so that concentrations of solutes are equal on both sides of the membrane
• Diffusion


  Most common form of passive transport in which a substance of higher concentration moves to an area of lower concentration. This process is essential for respiration. The gaseous exchange between oxygen and carbon dioxide
• Eukaryotic Cells


  • Cell Membrane
  • Nucleus (chromatin)
  • Cytoplasm
• Mitosis

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Meiosis


  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I

  5. Prophase II

  6. Metaphase II

  7. Anaphase II

  8. Telophase II
• Types of Cells


  • Epithelial
  • Connective
  • Muscle
  • Nervous
• Epithelial Tissue


  • Epithelium is a lining cell type
  • This lining can be internal (endothelium) or external (epithelial)
  • Also makes up endocrine and exocrine glands
  • Simple – one layer thick (alveoli)
  • Stratified – multiple layer thick (oesphagus)
  • Epithelium is avascular and required nutrient transport
  • Epithelial cells
  • Basement membrane
  • Collagen
• Connective Tissue


  • Connective tissue supports, connects and separates
  • Has three primary components: Cells, Ground substance, Fibres
  • Fibrous connective tissue is strong and provides support and shock absorption (i.e. dermis, ligaments and tendons)
  • Some connective tissue contains no fibres, for example blood and adipose tissue. The matrix would consist of plasma (blood) and fat (adipose)
  • The 'matrix'
• Smooth Muscle Tissue


  • Innervated by autonomic nervous system
  • Can be sympathetic (excitatory), parasympathetic (inhibitory) or both
  • Depolarisation occurs upon excitatory mechanisms, hyperpolarisation occurs upon inhibitory mechanisms
  • Neurotransmitter released along varicosities (swellings) along the muscle, having a wide diffusion area
• Skeletal vs Cardiac Muscle Tissue

  • Arranged in parallel cellular units
  • Numerous nuclei
  • Less mitochondria (for ATP production)
  • Reduced number of T-tubules
  • Intercalated discs improving cellular connection
  • Single nucleus
  • More mitochondria (25-33% of cell volume) for aerobic respiration
  • Increased number of T-tubules for improved access to action potential ions (sodium and potassium)
• Neuron


  • Typical example of a motor neuron
  • Motor sending action potentials to cardiac or skeletal muscle for example
  • Action potentials can also be sent to glands (made of smooth muscle)
  • AP passes from dendrite and soma, through the axon to axon terminal and synapse
  • Neurons have negative resting potential
  • Greater concentrations of K+ inside the cell
  • Greater concentrations of Na+ outside the cell
• Action Potentials

  1. Depolarisation is caused by opening of Na+ gates opening

  2. This rapid influx causes the extracellular fluid to depolarise and intracellular fluid to become positively charged

  3. Na+ will be passed back out of the cell, with K+ influx to bring to equilibrium or repolarisation

  4. Neuron should reach resting membrane potential again after a brief period of hyperpolarisation
• Glial Cells


  • Greek word Glia – meaning glue in English
  • Glial cells do not pass electrical impulses
  • They have a protective role within the central and peripheral nervous system
  • Support the development of myelin sheath, important for insulation of action potentials