Homeostasis

• Brain parts


  • Cerebral Cortex controls consciousness, intelligence, and memory
  • Cerebellum controls movement
  • Medulla controls unconscious actions like breathing and heart rate
• Synapses


  Gaps between 2 neurones where a chemical is released to trigger the impulse in the next neurone
• Investigating brain function and treating brain damage is difficult due to its complexity, delicacy, and lack of full understanding
• Reflex actions are subconscious responses that are automatic
• Reaction time is how long it takes to react to a stimulus and can be measured with a ruler drop test
• Eye parts

  • Retina, Optic Nerve, Sclera, Cornea, Iris, Ciliary Muscles, Suspensory Ligaments
• Homeostasis


  The maintenance of a constant internal environment
• Methods to map out regions of the brain

  1. Electrically stimulating parts of the brain using electrodes

  2. Using MRI scanners to see which part is active during a specific task
• Treatment methods for short and long-sightedness

  • Laser eye surgery, Replacement Lens, Contact Lenses, Spectacle lenses
• Normal Response in the Nervous System

  1. Receptor cells convert a stimulus into an electrical impulse

  2. Electrical impulse travels along a sensory neurone to the CNS

  3. Information is processed and the appropriate response is coordinated

  4. Electrical impulse is sent along a motor neurone to the effectors
• Reflex Arc

  1. Stimulus is detected by receptors

  2. Impulses are sent along the sensory neurone

  3. Impulse skips the CNS and passes to the relay neurone

  4. Impulses are sent along a motor neurone to the effectors
• If body temperature becomes too high

  Sweat is produced, Vasodilation occurs to increase energy transfer
• Human body temperature is 37.5 degrees Celsius
• If body temperature decreases too much

  Sweating stops, Vasoconstriction occurs to reduce heat loss, Hairs stand on end to trap warm air, Skeletal muscles contract rapidly to generate heat from respiration
• Aspects controlled by homeostasis in the human body

  • Blood glucose concentration
  • Body Temperature
  • Water Levels
• Accommodation in the eye

  1. To focus a nearby object: Ciliary muscles contract, suspensory ligaments loosen, lens is thicker and more curved

  2. To focus a distant object: Ciliary muscles relax, suspensory ligaments tighten, lens is thinner
• Regulation of Blood Glucose Levels

  1. If glucose is too high, the pancreas produces insulin

  2. Insulin promotes the uptake of glucose in muscle and liver cells causing glucose from the blood to be used in muscle cells for respiration, and converted into glycogen which is stored in the liver

  3. Blood glucose levels reduce

  4. If glucose levels are too low, the pancreas produces glucagon

  5. Glucagon promotes the conversion of glycogen to glucose in the liver, and so glucose is released into the blood and blood glucose levels rise
• Maintaining Water and Nitrogen Balance in the body

  1. If the water concentration of the blood increases, then cells in the body uptake water

  2. Cells expand when they take up water and may eventually burst

  3. If the water concentration of the blood decreases, then cells in the body lose water

  4. If body cells lose or gain too much water they do not function properly
• Adrenal Gland

  • Secretes adrenaline. Involved in the “fight or flight” response
• Testes


  • Secretes testosterone, involved in sperm production and the development of male secondary sexual characteristics
• Pancreas


  • Secretes insulin and controls blood glucose levels
• Components of the Human Endocrine System

  • Pituitary Gland
  • Pancreas
  • Thyroid
  • Adrenal Gland
  • Ovary
  • Testes
• Thyroid

  • Secretes thyroxine, controls metabolic rate, heart rate and temperature
• Ovary

  • Secretes oestrogen. Is involved in the menstrual cycle and the development of female secondary sexual characteristics
• Type 1 Diabetes
• Effects of decreased body temperature

  1. Sweating stops

  2. Vasoconstriction means blood doesn’t flow so close to the skin, resulting in less heat loss

  3. Hairs stand on end to create an insulating layer, trapping warm air

  4. Skeletal muscles contract rapidly to generate heat from respiration
• Anti-Diuretic Hormone (ADH) function

  1. It is released into the pancreas by the pituitary gland when a receptor in the brain detects that blood is too concentrated

  2. It travels in the blood stream to the kidney tubules

  3. An increased amount of ADH reaching the tubules increases their permeability to water, so more moves out of the tubules back into the blood stream

  4. This results in a smaller volume of more concentrated (yellow) urine and the blood becoming less concentrated as more water moves into it
• Kidney Failure
• Anti-Diuretic Hormone (ADH)
• Type 2 Diabetes
• Waste products filtered by the kidneys

  • Water
  • Ions
  • Urea
• Treatments for Kidney Failure

  • Dialysis: the function of the kidneys is carried out using an artificial membrane
• Pituitary Gland


  • The master gland. Secretes hormones into blood to either have an effect on the body or act on other glands to stimulate them to produce different hormones
• The Kidneys

  • As blood moves through the body the kidneys make urine by filtering out the waste products and selectively reabsorbing useful substances such as glucose, ions and water
• Homeostasis


  The maintenance of a constant internal environment
• Parts of the Brain

  • Cerebral Cortex controls consciousness, intelligence, and memory
  • Cerebellum controls movement
  • Medulla controls unconscious actions like breathing and heart rate
• Reaction time is how long it takes to react to a stimulus and can be measured with a ruler drop test
• Parts of the Eye

  • Retina - layer of light-sensitive cells at the back of the eye
  • Optic Nerve - carries impulses from retina to brain
  • Sclera - white outer layer supporting eye structures
  • Cornea - see-through layer at the front bending and focusing light
  • Iris - muscle controlling pupil size
  • Ciliary Muscles and Suspensory Ligaments - hold and shape the lens
• Accommodation in the Eye

  1. To focus on a nearby object: ciliary muscles contract, suspensory ligaments loosen, lens thickens and refracts more light

  2. To focus on a distant object: ciliary muscles relax, suspensory ligaments tighten, lens thins and refracts less light
• Investigating brain function and treating brain damage is difficult due to its complexity, delicacy, and lack of full understanding