biology

• Homeostasis


  The regulation of conditions inside the body to maintain a stable internal environment in response to changes in both internal and external conditions
• Cells in the body need certain conditions to function properly, such as not being too hot or too cold, not being too acidic or too alkaline, and having a good supply of glucose and water
• The body regulates everything and makes sure that everything is kept around the right levels
• Temperature and glucose levels do fluctuate, but only within small bounds
• The body can maintain its internal environment even if changes are taking place outside of itself, for example, when walking out in the snow or running in the Sahara desert
• Automatic control systems


  • They can recognize when there's a change from optimal conditions and then send a signal to reverse that change so that the levels go back to normal
  • They have three main components: receptors, coordination centers, and effectors
• Receptors


  Detect a change, such as a rise in temperature
• Coordination centers


  Interpret the change and decide what needs to be done about it, such as the brain or spinal cord
• Effectors


  Carry out the change, such as muscles that contract or glands that release hormones
• The nervous and endocrine systems are used to send signals between the different components of the automatic control systems
• Nervous system


  Sends fast and precise electrical impulses through nerves, allowing for quick responses
• Endocrine system


  Relies on hormones, which are small chemicals released into the bloodstream and affect certain cells with the right receptors, but is generally slower, longer-lasting, and more generalized than the nervous system
• Negative feedback


  The mechanism by which the automatic control systems work, where they decrease a level that is too high or increase a level that is too low to return it to normal
• Negative feedback mechanism


  1. Receptors detect a change

  2. Coordination centers interpret the change and decide what to do

  3. Effectors carry out the response to return the level to normal
• The nucleus is the control centre of the cell, containing genetic material (DNA) that controls all activities within the cell.
• Mitochondria are responsible for producing energy through aerobic respiration.
• The cytoplasm contains organelles such as mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, cytoskeleton, and chloroplasts.
• Mitochondria produce energy from glucose molecules using aerobic respiration.
• Ribosomes synthesize proteins according to instructions provided by DNA.
• Ribosomes synthesize proteins using information from DNA.
• Lysosomes contain enzymes that break down waste products inside the cell.
• Circulatory system in fish


  Deoxygenated blood is pumped from the heart to the gills where it collects oxygen and becomes oxygenated, the oxygenated blood then passes straight from the gills to the organs where the oxygen diffuses out of the blood and into the body cells, the blood now returns to the heart
• Problem with single circulatory system in fish


  The blood loses a lot of pressure as it passes through the gills before reaching the organs, this means the blood travels to the organs relatively slowly so it cannot deliver a great deal of oxygen
• Circulatory system in humans


  Deoxygenated blood is pumped from the heart to the lungs where it collects oxygen, this oxygenated blood then returns to the heart, the heart now pumps the oxygenated blood to the organs where the blood transfers its oxygen to the body cells, the blood now returns back to the heart
• Benefit of double circulatory system in humans


  Because the blood passes through the heart twice, it can travel rapidly to the body cells delivering the oxygen that the cells need
• Heart


  • An organ consisting mainly of muscle tissue
  • The job of the heart is to pump blood around the body
• Heart chambers


  4 chambers - left atrium, right atrium, left ventricle, right ventricle
• Valves


  Separate the atria from the ventricles
• Blood vessels entering/leaving the heart

  • Vena cava (brings in oxygenated blood from the body)
  • Pulmonary artery (blood passes from the heart to the lungs)
  • Pulmonary vein (oxygenated blood passes from the lungs to the heart)
  • Aorta (blood is pumped from the heart to the body)
• Pattern of blood flow through the heart


  1. Blood enters the left and right atria

  2. Atria contract, forcing blood into the ventricles

  3. Ventricles contract, forcing blood out of the heart

  4. Valves prevent backflow into the atria
• Left ventricle


  • Has a thicker muscular wall than the right ventricle, as it pumps blood around the entire body and needs to provide greater force
• Coronary arteries


  Branch out of the aorta and spread into the heart muscle, their purpose is to supply oxygen to the muscle cells of the heart
• Pacemaker


  A group of cells found in the right atrium that control the natural resting heart rate
• Artificial pacemaker


  A small electrical device implanted by doctors to correct irregularities in the heart rate when the natural pacemaker stops working correctly
• Chloroplasts convert light into chemical energy during photosynthesis.
• Vacuoles store water, nutrients, and wastes within plant cells.
• Cytoskeleton provides support and structure to the cell.
• Ribosomes synthesize proteins using information from DNA.
• The chlorophyll molecule absorbs light energy from sunlight.
• Light energy absorbed by chlorophyll is used to split water molecules into hydrogen and oxygen atoms.