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Coordination & control


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Coordination & control

  1. 1. Coordination & Control
  2. 2. Organisms detect and respond to changes called stimuli in the internal and external environment. The environment includes living or biotic as well as non- living or abiotic factors. They include factors such as pressure, pain, light, sound, temperature and chemicals These changes are detected by specialised sensory receptors. Sensory receptors respond to the intensity, location and duration of a stimulus
  3. 3. Receptors can be classified into the following categories  Mechanoreceptors: that detect pressure and touch  Chemoreceptors: that detect chemicals  Photoreceptors: that detect light  Thermo receptors: that detect heat and cold  Pain receptors: that detect pain
  4. 4. Temperature The human core body temperature operates at an optimum 37 (0C) The environmental or ambient temperature at which a human can live comfortably is a range of 10 – 40 (0C). Any lower or higher requires humans to wear special clothing or change their environment. Hypothermia (extreme cold) cause heat loss leading to the slowing down of the bodies metabolism leading to frostbite and possibly death.
  5. 5. Hyperthermia (extreme heat / humidity) can lead to metabolic breakdown as enzymes denature above 42 (0C) leading to structural protein breakdown. Thermo receptors detect these changes and send messages to the CNS to either maintain heat in the body through “shivering” or to lose heat via “sweating”
  6. 6. Structure of the skin
  7. 7. Light Light passes through the lens and is focused on a special layer of photoreceptors in the retina. These messages are carried through the optic nerve to the brain where shape and colour is formed. Two types of receptors Rods: detect shape and movement Cones: detect colour
  8. 8. Structure of the eye
  9. 9. Sound Sound is captured by the pinna, the external flap of cartilage. These sound waves are transmitted towards the eardrum or tympanic membrane. The waves are then vibrated by the small ear bones (hammer, anvil, stirrup) or ossicles through to the cochlea and then via the sensory or auditory nerve to the brain. The volume is measured in decibels The sense of balance is maintained by the “semi-circular canals” within the inner ear.
  10. 10. The structure of the human ear
  11. 11. Chemicals The presence of chemicals are detected by chemoreceptors. Olfactory receptors detect smell Taste is detected by taste buds on the tongue which can differentiate between  salty  sweet  sour  bitter
  12. 12. In each case stimuli from the environment which is detected by the sensory nerves and relayed by the CNS enables one of two responses Involuntary or automatic response Voluntary or conscious response
  13. 13. Nervous System The nervous system is composed of a system of nerve cells which allow the transmission of electro-chemical messages. Each nerve cell consists of a cell body which contains the nucleus, a number of extensions called dendrites which receive information which then passes the information along the axon which is covered in a myelin sheath. These impulses can travel up to 100 metres per second.
  14. 14. Transmission of a nerve impulse
  15. 15. The nervous system is composed of two parts. The CNS or central nervous system which is composed of the brain and spinal cord The PNS or peripheral nervous system which is made up of the sensory and motor neurons. Information or stimuli from the environment are detected by the sense organs and travel via sensory nerves to the CNS where a voluntary or involuntary signal is sent via the motor neuron to an effector where a response will occur
  16. 16. A stimulus – response pathway
  17. 17. Reflex - arc A reflex-arc is a rapid automatic or involuntary response which bypasses the brain. Examples include - Knee jerk response - Blinking of the eye - Swallowing In many cases the reflex – arc protects the body from harm. It can be harmed by drugs such as alcohol.
  18. 18. Reflex - arc
  19. 19. Stimulus – response model Homeostasis (steady state)is the maintenance of an optimum internal environment despite external changes. This is achieved by the stimulus - response model and negative feedback mechanisms. Stimulus Receptor Transmission Effector Response Negative Feedback Negative feedback reverses or inhibits the stimulus
  20. 20. Hormone System Hormones are chemical messengers produced by endocrine glands in small amounts which regulate growth and reproduction. Hormones are either  Steroids derived from cholesterol which are lipid soluble and can directly effect receptor molecules within a cell  Proteins derived from amino acids which cannot pass through cell membrane but instead attach to “hormone receptor cells” outside a cell
  21. 21. Comparing Nervous and Hormonal Systems
  22. 22. Endocrine glands of the human body
  23. 23. Homeostasis – Temperature Regulation Negative Feedback Mechanism
  24. 24. Mechanisms which conserve heat  Erection of hairs (goose bumps) which trap layer of air close to the body Vasoconstriction – restriction of blood flow from the skin to the core Increased production of hormones adrenalin and thyroxine which increases rate of metabolism Involuntary shivering producing heat Voluntary actions such as rubbing hands together or jumping around
  25. 25. Capillary blood flow
  26. 26. Mechanisms which remove heat Animals have flattened hair or feathers which prevent trapping of air Vasodilation – blood is redirected from the core to the skin Sweat glands release sweat which evaporates cooling the body down. In some animals this done via the tongue (panting) Metabolic rate is reduced (seasonal)
  27. 27. Exchange of materials It is vital that materials are exchanged between the internal and external environment. The following organs contain special structures to maximise the exchange, Kidney: nephron Lungs: alveoli Intestine: villi Exchange surfaces are  thin: to decrease the distance that materials need to diffuse across  moist: to keep cells alive and provide a layer for substances like oxygen to dissolve in prior to diffusion  large surface area: to provide a larger area over which diffusion can occur
  28. 28. Role of blood and lymph capillaries Arteries carry blood away from the heart and veins carry blood back to the heart Capillaries link arteries and veins. They are very thin allowing for the exchange of material and removal of wastes. Lymph capillaries drain excess fluid which has “leaked” from surrounding tissues into the lymphatic system and return the excess fluid back to the circulatory system near the heart.
  29. 29. Blood and Lymph vessels
  30. 30. The Human Lymph System
  31. 31. The Kidney The structural and functional unit of the kidney is the nephron. The nephron maximises the surface area for exchange. One nephron consists of - Bowmans capsule - Glomerulus - Long thin tubule Nephrons have a rich blood supply, thin and moist conditions
  32. 32. Nephrons in the Kidney
  33. 33. 20 % of the blood is diverted to kidney via the renal artery Filtration Blood enters the glomerulus – a “ball” of capillaries and under considerable pressure into the Bowmans capsule via a semi-permeable membrane, separating molecules according to size. Larger molecules such as rbc and proteins are not filtered but continue along capillaries which surround the nephron. The remaining 20% of blood plasma becomes filtrate. This will include glucose, water and urea
  34. 34. Reabsorption As the filtrate passes along the proximal tubule, Loop of Henle and distal tubule, certain substances which are useful i.e. water and glucose are actively reabsorbed. Rate of reabsorption can be affected by hormones such as Anti-Diuretic Hormone (ADH) which controls water reabsorption. Alcohol decreases rate of ADH therefore increasing rate of urine production
  35. 35. Chemicals such as drugs and poisons are excreted from the capillaries into the tubule. About 99% of water is reabsorbed meaning urine becomes very concentrated 150 litres of blood passes through kidney each day with 148.5 reabsorbed leaving about 1.5 litres of urine to be excreted.
  36. 36. Lungs The structural and functional unit of the lung is the alveoli. They provide the gas exchange surface area in which oxygen and carbon dioxide are exchanged between blood and the air Alveoli provide: - A large surface area - A thin membrane ( 1 cell thick) - A moist layer to assist with diffusion
  37. 37. Normal composition of air is approximately Oxygen 20 % Nitrogen 80 % Other gases (CO2) < than 1 % Blood returning to lungs contains between 12 & 15 % dissolved Oxygen 80 % Nitrogen 3-4 % CO2
  38. 38. Alveoli in the lungs
  39. 39. Inspiration Diaphragm contracts and pulls down Intercostal muscles contract pulling ribs upwards and outwards Increase in volume of chest cavity and decrease in pressure Air is then forced into lungs by greater air pressure outside of the body
  40. 40. Expiration Diaphragm, ribs and intercostal muscles relax Decrease in volume of chest cavity and increase in pressure Air passively leaves lungs due to the change in air pressure. During exercise air can be expelled forcibly by abdominal muscles
  41. 41. Gas Exchange Gas exchange occurs across the alveolar membrane in the following manner: O2 from alveolus blood capillaries CO2 from the blood capillaries alveolus O2 and CO2 move across the alveolar membrane by diffusion. Rate of diffusion is affected by:  concentration gradient of gases Rate of blood flow Rate / depth of breathing
  42. 42. O2 is attached to haemoglobin inside rbc’s forming oxyhaemoglobin. CO2 is transported in the main as bicarbonate ions dissolved in the plasma and some attached to haemoglobin The build up of CO2 is the stimulus for the “respiratory centre” to breathe more rapidly and deeply.
  43. 43. Lung function impairment Asthma Bronchioles constrict reducing volume and rate of breathing. Emphysema Reduced area of alveolar membrane which limits diffusion. Pneumonia Accumulation of fluids reduces effective volume and rate of diffusion. Carbon monoxide poisoning Up to 200 x more attracted to haemoglobin than oxygen reducing its availability leading to loss of consciousness
  44. 44. Small Intestine -Villi Villi are finger like projections from the wall of the small intestine that assist in the absorption of soluble materials from the intestine into the bloodstream. Villi provide a Thin Moist membrane Large surface area Rich blood supply
  45. 45. Villi in the small intestine
  46. 46. Micro villi in the small intestine
  47. 47. Structural features of villi Lacteal in the core of each villus (part of lymphatic system) Epithelial cells surrounding villus are covered in microvilli increasing surface area Rich capillary network
  48. 48. Nutrients are absorbed from the small intestine by both active and passive processes Passive Glucose, amino acids, nucleotides and ions are moved via diffusion into the blood capillaries in the villi Active Active transport will move substances against a concentration gradient Products of fat digestion are absorbed then moved by exocytosis out of the cells into the lacteal