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Topic 6 4 6doc


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  • 1. Pavina, Brittany, EmmelynTopic 6.4: Gas ExchangeVentilation Movement of air into and out of the lungs during inspiration and expiration. The diaphragm and ribcage help conduct this movement. Breathing in brings in oxygen and breathing out removes carbon dioxide. Alveoli increases surface area for gas exchange. That is why it is more efficient. Mechanics of VentilationInspiration: Expiration:External intercostals muscles contract Internal intercostals muscles contractDiaphragm contracts (drops) Diaphragm relaxes (rises)Abdominal muscles relax Abdominal muscles contractChest volume increases Chest volume decreasesPressure in lungs decreases Pressure in lungs increasesAir enters Air is pushed out
  • 2. Pavina, Brittany, EmmelynTopic 6.5: Nerves, Hormones, and HomeostasisNervous system Central nervous system consists of the brain and spinal cord. The peripheral nervous system are all the other nervous throughout the body The nervous system is composed of neuron. Resting potential: electoral potential across the cell membrane that is not conducting an impulse. It is maintain by active transport. Outside of the cell is more positive and inside in more negative. Action Potential: The depolarization and repolarization of the electrical potential across a cell membrane as a nerve impulse passes along a neuron. Synaptic transmission: 1. Nerve impulse reaches terminal end of pre-synaptic neuron 2. . Depolarization causes calcium channels to open and calcium ions rush in. 3. Calcium ions cause synaptic vesicles to move to membrane and fuse. 4. Neurotransmitter in the vesicles are released and moved across the synaptic gap. 5. The neurotransmitter binds with post-synaptic receptors. 6. Sodium channels open causing sodium ions to enter which leads to depolarization. 7. Neurotransmitters are broken down and move back to the pre-synaptic neuron.
  • 3. Pavina, Brittany, Emmelyn Homoeostasis monitors levels of variables and makes corrections by negative feedback and mechanisms. Example: Thermoregulation Thermoregulation controlled by hypothalamusToo Cold Too HotArterioles constrict Arterioles dilateSweat glands close Sweat glands openHairs stand up, trap layer of air Hairs lie flat, no boundary levelMuscles spasm (Shivering) RESULT: Blood CoolsRESULT: Blood Warms Blood glucose is maintained through the actions of the pancreas and liver When blood glucose is high: -Beta cells in the pancreas secrete insulin  liver and fat converts glucose to glycogen When blood glucose is low: -Alpha cells in the pancreas secrete glucagon  liver converts glycogen to glucose
  • 4. Pavina, Brittany, EmmelynTopic 6.6: Reproduction Gametes – cells that fuse in fertilization during sexual reproduction Functions of Testosterone: pre-natal development of male genitalia, secondary sexual characteristics in puberty, sex drive and aggression Menstrual Cycle Hormones (controlled by endocrine system) o FSH: stimulates egg development o LH: matures egg and causes release (ovulation) o Estrogen: develops endometrium (uterus lining) o Progesterone: maintains endometrium; negative feedback on FSH and LH o HCG: pregnancy hormone – keeps estrogen and progesterone high o Oxytocin: birth hormone – contractions of uterus In-Vitro Fertilisation (IVF) 1. FSH and LH given to stimulate multiple egg releases 2. Eggs are collected 3. Eggs are fertilized with father’s sperm in a dish and incubated 4. Fertilized blastocytes are selected and developed into embryos 5. Up to 3 can be selected for implantation – hopefully one will “take” 6. After bedrest and about a month, woman takes pregnancy test. If positive: pregnancy continues. If not, woman can wait a few months to try again Arguments for IVF Arguments against IVF The right to have children Playing god? Improved medical tech makes it safer than The risk of multiple pregnancies before Some governments cover costs on NHS Expensive Hope is given to those who can’t conceive High emotional costs if it fails naturally Termination of excess embryos count as Unused embryos can be used for later murder? (dontated or as stem cells)
  • 5. Pavina, Brittany, Emmelyn