Unit 2

• Mitosis


  One of the processes of cell duplication, where one cell and all of its properties divide into two genetically identical diploid daughter cells
• Mitosis


  1. Interphase

  2. Prophase

  3. Metaphase

  4. Anaphase

  5. Telophase

  6. Cytokinesis
• Diploid cells


  Cells with 2 sets of chromosomes, and almost all cells are diploid apart from gametes/sex cells which are haploid
• Interphase


  Subcellular parts of a cell (mitochondria, chromosomes, etc) in the nucleus are duplicated
• Prophase


  The membrane of the nucleus begins to break down and spindle fibres appear on either side of the cell
• Metaphase


  The nucleus has fully broken down and the chromosome copies line up on either side of the cell along the spindle fibres
• Anaphase


  The chromosome copies are then separated and move to either side of the cell along the spindle fibres
• Telophase


  A membrane begins to form around each pair of chromosomes on either side of the cell to form nuclei
• Cytokinesis


  The cell surface then forms a membrane between the two halves and separates it, causing the one cell to now become two genetically identical daughter cells
• Cancer


  When a cell begins to divide uncontrollably as a result of a change in the cell, which over time can create lumps of cells called tumours which damage the body and result in death if not able to be treated
• Growth


  An increase in size as a result of increase in number of cells, which would be as a result of mitosis
• Growth in animals


  • Cell division and then cell differentiation/specialisation, where cells change their shape and parts according to their functions in the body
• Growth in plants


  • Cell division, differentiation and then elongation at the meristems, where the cells in a plant continually increase in length throughout their lives
• Asexual reproduction


  When an organism produces genetically identical offspring also known as clones without the requirement of a partner, meaning asexual reproduction relies on mitosis
• Percentile charts


  Used to monitor growth of new-born babies for the first 12 months of life to compare their growth rates alongside the rest of the new-born population and place them on a percentile
• Stem cells


  Cells which divide continuously and can differentiate into specialised cells. They are initially undifferentiated.
• Embryonic stem cells (ESCs)


  • The stem cells in an embryo, formed after the female egg cell is fertilised with the male sperm cell. ESCs can differentiate into any type of specialised cell.
• Adult stem cells


  • Limited specialised cells which can only differentiate to specific cells which are in the surrounding tissues, only for replacing damaged cells.
• ESCs could possibly be cultured or extracted from embryos (which is seen as unethical as you would have to kill the embryo) to treat many diseases which damage and destroy cells. However, ESCs could continue to divide inside a new body and lead to cancer, as well as the body seeing the foreign ESCs as a threat and be killed off by the immune system, called rejection.
• The brain


  Made up of millions of nerve cells/neurons which run through the entire body to send signals and information up and down
• 3 main parts of the brain

  • Cerebral cortex
  • Cerebellum
  • Medulla oblongata
• Cerebral cortex


  At the front, separated into 2 cerebral hemispheres controlling the body. The left hemisphere controls the right side of the body while the right hemisphere controls the left side. It is responsible for controlling most of our senses, language, memory, behaviour and consciousness.
• Cerebellum


  At the bottom of the brain, also separated into two halves, each controlling balance and posture, as well as fine tuning muscle activity and making movements smoother.
• Medulla oblongata


  Connects the spinal cord to the brain and controls heart rate, breathing and reflexes such as sneezing, swallowing and vomiting.
• Spinal cord


  A large bundle of nerves which carry information across the body to the brain.
• CT scans


  Show shape and structures of the brain by moving an X-ray beam around the head. Detectors on the opposite side measure the absorption of X-rays by the brain to create a clear image which is easily observable.
• PET scans


  Show brain activity and what parts of the brain are working during certain activities. It is done by injecting radioactive glucose into the patient. Glucose is used in cellular respiration for energy, so the part of the brain which is more active takes in the glucose. The radioactive atoms in the glucose cause gamma rays to be emitted which scanners can detect and the more radiation from one area of the brain, the higher the activity is there for a certain task.
• Brain and spinal cord damage

  Can cause paralysis (loss of use or feeling in parts of the body) and there is very little that can be done to cure this.
• Brain tumours


  Caused by cancer in the brain. This lump of cells can cause parts of the brain to not function as it is being obstructed. Tumours can be killed using radiotherapy (focusing high energy X-ray beams to kill the cells) and chemotherapy (injecting drugs to kill the tumour directly). However, they can harm the body as well, and chemotherapy could be ineffective due to the blood-brain barrier which only allows certain substances to get from the blood into the brain.
• Central Nervous System (CNS)

  Made up of the brain, spinal cord and neurons which allow the body to send information around in the form of electrical impulses.
• Neurotransmission


  Receptor cells in the sensory organs detect a stimulus, which travels to the brain through neurotransmission along the nerves for the brain to formulate a response. Neurons meet each other at synapses which are tiny gaps and when an impulse reaches the synapses, a chemical substance called a neurotransmitter is released and detected by the next neuron and repeats along the CNS.
• Types of neurons


  • Sensory neuron
  • Motor neuron
  • Relay neuron
• Sensory neuron


  Carries impulses to and from the receptor cells and brain. Impulses enter the neuron by the dendrites, travel along the dendron, through the axon and out to the next neuron by the axon terminals. They are surrounded by a layer called the myelin sheath which allows the impulse to travel along one neuron and prevent it from jumping to others, as well as insulating it to maintain speed of transmission.
• Motor neuron


  Carries impulses towards effectors (after the brain creates a response to a stimulus, it sends it to an effector to carry out that response).
• Relay neuron


  Found in the spinal cord, link up the motor and sensory neurons, as well as play an integral part in the reflex arc.
• Reflexes


  Actions which are taken by the body without having to think about it. It may be used to avoid harm, or it may be a natural bodily function (sneezing/swallowing). Reflexes do not need to be thought about so the impulses bypass the route to the brain.
• Reflex arc


  Impulse travels along the sensory neuron, onto the relay neuron at the spinal cord and then to the motor neuron to the effector to carry out what must be done to prevent harm to the body.
• The eyes


  Sense organs which allow for sight. Two types of receptor cells called rods (which detect light intensity) and cones (which detect colour of light) are found in the eye in a layer called the retina.
• Pupil


  The dark area in the centre of the eye. The iris controls the amount of light entering the eye. Constricting the pupil (make it smaller) allows less light through, while dilating it (making it bigger) allows more light through.
• Cornea


  Refracts light rays to bring them together to focus on the retina in order to create a clear image.