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• How does oxygen enter and carbon dioxide leave bloodstream?

  • Oxygen diffuses from air into the alveoli into blood in the capillaries.
  • Carbon dioxide diffuses from blood in the capiliaries into the air in the alveoli.
• How are alveoli adapted for gaseous exchange?

  • Large surface area
  • Surrounded by a network of capillaries giving a good blood supply.
  • Rapid blood flow maintains a steep concentration gradient.
  • Thin walls so short diffusion distance
  • Partially permeable membranes enabling diffusion
  • Moist lining for dissolving gases
• How is small intestines adapted for the rapid absorption of food molecules?

  Small intestine covered in villi:

  • Provide large surface area
  • Thin walls consists of a single layer of cells enabling rapid absorption and providing short diffusion distance
  • Partially permeable membrane allowing diffusion
  • Surrounded by network of capillaries giving a good blood supply.
  • Rapid blood flow
• Circulatory system

  Network of organs and vessels that enables flow of blood and transport of oxygen, carbon dioxide , nutrients and other molecules around the body.
• What are the three parts of the circulatory system?

  • Blood, blood vessels and the heart
• What is the order of blood around the body?

  Body tissues-->Vena Cava-->Right Atrium-->Right ventricle-->pulmonary artery-->LUNGS-->Pulmonary veins-->left atrium-->Left ventricle-->Aorta-->body tissues
• Describe the journey of blood throughout the body?

  Deoxygenated blood enters right atrium via vena cava. Blood flows into right ventricle which pumps blood to lungs via pulmonary artery. The blood binds with oxygen and creates oxygenated blood which returns to the heart, entering the left atrium via pulmonary vein. Blood flows into left ventricle which pumps blood to the rest of the body via aorta.
• What is the flow of blood throughout the body?

  • Heart-->artery-->capillaries-->veins-->heart
• Explain how and why the walls of the ventricles differ in thickness?

  The wall of the left ventricle is thicker than the wall of the right ventricle. This is because the left ventricle needs to generate greater pressure than the right ventricle because it pumps blood all over the body. Whereas, the right ventricle pumps blood to to the lungs.
• What is the function of capillaries?

  • Exchange substances (nutrients and oxygen)
  • Taking away waste products such as CO2
  • Single cell thick+ permeable
  • Cross-sectional area is huge
  • Lower blood pressure
• What is the function of veins?

  • Carries blood to the heart
  • Has the biggest lumen
  • Low blood pressure
  • small layer of elastic fibres + smooth muscle doesn't need to be strong
  • Contain valves which prevent backflow
• What is the function of arteries?

  • Carry blood away from the heart
  • Blood is pumped at high pressures
  • Strong and elastic
  • Thick muscle and narrow lumen
• Describe three ways in which red blood cells are adapted to carry oxygen?

  • Red blood cells have a large surface area to volume ratio for absorbing oxygen.
  • They don't have a nucleus, which allows more room for carrying oxygen.
  • They're small and flexible so they can easily pass through tiny capillaries.
• Function of cardiac muscle

  Contracts to pump blood around body
• Function of coronary arteries

  Supply heart muscle with oxygen and nutrients
• How is cardiac muscle adapted to function?

  Contains many mitochondria to product ATP for muscle contraction
• What is plasma?

  • Pale yellow liquid portion of blood.
  • Transports: Water, Digested food products like glucose, CO2, Urea , Hormones, antibodies.
• How is plasma adapted to its function?

  Plasma consists of mainly water. This acts as a solvent enabling transport of materials around the body.
• Neurone

  Nerve cells adapted to quickly transmit nerve impulses.
• Function of sensory neurone

  Carries impulses from receptor to the CNS
• Functions of motor neurone

  Carries impulses from the CNS to the effector
• Describe how CNS coordinates response to stimulus

  • Stimulus
  • Sensory receptor detects stimulus
  • Sensory receptors sends impulses along sensory neurone to the CNS.
  • CNS coordinates response
  • CNS sends information to effector along motor neurone
  • Effector produces a response to the stimuli response
• Describe how neurone are adapted for the transmission of the nerve impulses

  • Long axon carries impulse rapidly away from the cell body and enables transmission over long distances.
  • Myelin sheath ( Electrically insulating layer) surrounds axon and increases speed of impulses.
  • Dendrites ( Extensions from the cell body) provide a large surface area to receive impulses
• Synapse

  Small gap between neurones across which a nerve impulse is transmitted via neurotransmitters
• How are nerve impulses transmitted across a synapse?

  • Nerve impulse reaches presynaptic neurone
  • This triggers release of neurotransmitters
  • Neurotransmitters diffuse across the synapse
  • They bind to receptors on the postsynaptic neurone
  • Stimulates an impulse in the postsynaptic neurone
• reflex

  • automatic response to a stimulus by the body
  • involuntary - does not involve conscious part of the brain
• describe reflex arc

  stimulus --> sensory receptor --> sensory neurone --> relay neurone --> motor neurone --> effector --> response
• endocrine system

  Network of glands that produce and secrete hormones into the bloodstream
• Compare endocrine and nervous system (4)


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• Adrenaline

  Hormone produced by the adrenal glands that's involved in the fight or flight response.
• Describe how adrenaline increases respiration at muscle tissues?

  • Secreted by adrenal glands
  • Travels in the blood to the liver
  • Binds to specific receptors on cells in the liver
  • Causes livers to break down glycogen stores releasing glucose in the bloodstream
  • Increased heart rate causes greater blood flow to muscle.
  • Cells receive more oxygen and glucose for respiration
• Describe how adrenaline increases heart rate

  • Secreted by adrenal glands
  • Travels in the blood to the heart
  • Binds to specific receptors on cells in the heart
  • Causes heart muscle to contract more forcefully and frequently.
  • Heart rate increases
• What is the function of thyroxine?

  • Thyroxine is a hormone released by the thyroid (found in the neck). It regulates metabolism which is the speed at which chemical reactions in the body occur. It is important for growth and protein synthesis.
  • Thyroxine is released in response to thyroid stimulating hormone (TSH) which is released from the pituitary gland.
• Describe how negative feedback system controls blood thyroxine levels.

  • If blood thyroxine levels increase above a set point, TSH secretion is inhibited. Less thyroxine is produced by the thyroid gland. Thyroxine levels return to normal.
  • If blood thyroxine levels decrease below a set point, TSH secretion is increased. More thyroxine is produced by the thyroid clans. Thyroxine levels return to normal.
• What is homeostasis?

  Maintaining a constant internal environment.
• What does the body need to stay steady?

  • Blood glucose concentration
  • Water content
  • Body temperature
• What is the function of FSH?

  • Released by the pituitary gland.
  • Causes a follicle (an egg) to mature in one of the ovaries.
  • Stimulates oestrogen production.
• What is the function of oestrogen?

  • Released by ovaries
  • Causes lining of uterus to thicken and grow.
• What is the function of LH?

  • Also known as luteinising hormone.
  • Released by pituitary gland.
  • An LH surge stimulates ovulation at day 14- the follicle ruptures and the egg is released.
• Explain the stages of the menstrual cycle?

  • Stage 1- Day 1, is when menstruation starts.
  • Stage 2- The uterus lining is repaired.
  • Stage 3- An egg develops and is released from the ovary at day 14.
  • Stage 4- The lining is maintained.