3A- Chemicals of life

• Cells are the basic structural units of all forms of life
• Cells


  • They are specialized for different functions which are typical of the nervous system
  • You can see them under a microscope
• Types of cells involved in behaviour


  • Neurons, glial cells (in brain) --> neurons= main type of cell in brain
  • Receptor cells (in sensory organs, ex. eye) --> are not in brain but in sensor organs, ex: photoreceptors pick info from light
  • Ganglion cells (neurons clustered together in peripheral nervous system) --> located away from brain, transfer sensory message away from brain
• Typical structure of animal cell(don't rly need to remember these)


  • Organelles (specialized structures inside the cell)
  • Nucleus containing the DNA (with the majority of genes)
  • Cytoplasm
  • Cell membrane- maintains structure + shape
• Brain is made of neurons (and glial cells)
• Neuron has similar structures as other animal cells, but also differences

  • neurons- highly specialized cells for transmission of electrical signals
  • has dendrites around the cell body

  • cell body/soma --> surround nucleus + contain organelles (mitochondria, nucleus, etc..)
  • axon --> long tail of neuron
  • myelin sheath wrapped around axon
  • axon terminals containing synapses that pass on action potential
• From DNA to proteins

  1. Transcription (from DNA to RNA)

  2. Translation (from RNA to protein)- occurs outside of nucleus in cytoplasm
• What are proteins?

  • Large, complex molecules that do most of the work in cells; proteins are also coiled
  • Proteins can be enzymes (make biochemical reactions happen)
  • Proteins can be messengers (chemical communication across the body; ex: hormones)
  • Proteins can be structural components (e.g. membrane channels, receptors for neurotransmitters, histones, capture other proteins floating in extracellular space)
• Cytoplasm vs extracellular space: fats are in all cells


  • cell membrane made up of double layer of fats (phospholipid bilayer) --> creates separation between inside and outside of cell
  • Water solution inside (intracellular space) and outside (extracellular space) the cell
  • Separated by a double layer of lipids (fats)
• Ions- possess an electric charge


  • Created when you dissolve salts in watery solutions
  • They are the same chemical elements but in a different form
  • The structure of the atom changes and becomes charged negatively or positively depending on their characteristics (ex: NaCl --> Na+ Cl-; sodium loses 1 electron and chlorine gains 1 electron)
• Neuronal membrane


  • Keeps ions either outside or inside the cell
  • Different concentration of different ions between intra- and extra-cellular space (charged particles stay either in or out; K, Cl, Na)
  • Resulting in a different charge (more negative inside and more positive outside)
  • Ion channels are proteins scattered in the cell membrane that allow passage of ions --> They can open/close.
• Electricityof the neurons


  • Neurons are electrically charged
  • They generate electrical currents by changing the imbalances of ions between the intra- and extracellular space
  • As negative and positive charged elements attract each other, the ions move when allowed to go through the cell membrane and by moving they generate electrical impulses
• Axons

  • Myelin (a fatty substance that does not have the channels/pores for ions) insulates the axon and makes the electrical impulse travel faster
  • Nodes of Ranvier are the gaps between the myelin- impulse jumps from node to node
• Synapses


  • At the end of the axon (can be long as in a nerve), the electrical message needs to be transferred to another cell (another neuron, a muscle cell or a hormone-producing organ)
  • at the end of axon- synapses (end of axon of one neuron + beginning of dendrite of another neuron)
  • info is transmitted from the pre-synaptic neuron to the post-synaptic neuron via the synaptic gap
  • Neurotransmitters (small molecules related to proteins): Acetylcholine, serotonin, glutamate, dopamine, GABA
  • Proteins on cell membrane (or nucleus), act as receptors and ion channels
• Brains are made mostly of neurons
• Neurons, as most other cells in the body, have DNA that codes for proteins
• Genes are located on the DNA
• Neurons are highly specialised cells for the transmission of electrical signals
• Chemical imbalances in ions around the neurons define their electrical activity
• Specific proteins give neurons their functions of sending/receiving electrical signals to/from other neurons and to other tissues in the body
• Nucleus

  • contains DNA (double helix coiled together to form chromosomes- 23 pairs)
  • genes located on chromosomes
  • gene= a length of DNA that contains the info for constructing a particular protein; 1 gene= 1 protein