Homeostasis

• Homeostasis is the regulation of a constant internal environment to ensure optimum conditions for metabolism and changes in response to internal and external fluctuations
• In humans, homeostasis regulates blood glucose levels, body temperature, CO₂ levels, and water levels
• Homeostasis is maintained by automatic control systems coordinated by the nervous system or endocrine system
• A synapse is the gap where the ends of two neurons meet
• Information is transmitted across the synapse by chemical neurotransmitters
• Neurotransmitter chemicals are released into the synapse when an electrical impulse arrives at the terminal of the first neuron
• Nerve impulse is created in the second neuron when a complimentary chemical binds to receptor sites
• A reflex arc begins with a stimulus detected by receptor cells
• The impulse is transmitted along a sensory neuron towards the central nervous system (CNS)
• The CNS coordinates a response through relay neurons, which can be conscious or subconscious
• The response is sent along a motor neuron to effector cells
• The nervous system allows a fast, short-lived response to stimuli
• Information is received by a receptor, passed along neurons as an electrical impulse, and results in a response
• Parts of a typical neuron include the axon, myelin sheath, dendrites, and cell body
• Hormones are chemical messengers transported in the bloodstream to activate a response
• Hormones act on target cells and affect only certain cells
• The pituitary gland acts as a master gland, controlling the release of hormones from other glands
• Type 1 diabetes is due to the pancreas not producing enough insulin
• Type 1 diabetes is treated with insulin injections
• Type 2 diabetes is when effector cells do not respond to pancreatic hormones
• Type 2 diabetes can be managed through lifestyle choices like diet and exercise
• Oestrogen is the main reproductive hormone in females, produced in the ovaries
• Oestrogen stimulates ovulation, releasing an egg every 28 days on average
• Testosterone is the main reproductive hormone in males, produced in the testes
• Contraceptive methods include hormonal and non-hormonal options
• Hormonal methods inhibit FSH or release progesterone to prevent pregnancy
• Non-hormonal methods create physical barriers to prevent sperm from reaching the egg
• Adrenaline is produced by the adrenal glands in response to stress or fear
• Adrenaline increases heart rate, breathing rate, and widens blood vessels for a 'flight or fight' response
• Thyroxine is produced by the thyroid gland and controls metabolism by regulating energy release
• Negative feedback regulates the level of thyroxine in the body
• FSH and LH can be given as fertility drugs to help women become pregnant naturally
• In Vitro Fertilisation (IVF) involves stimulating ovaries, collecting eggs, fertilizing them in the lab, and implanting embryos for pregnancy
• Fertility treatments involve inserting one or two embryos into the woman's uterus for implantation
• If successful, the pregnancy progresses as normal
• Fertility treatments offer couples the chance to have their own baby
• Fertility treatments are often stressful and emotional with low success rates
• Underlying causes of infertility are not usually treated
• Fertility treatments can increase the chance of multiple births (twins, triplets, or more), posing risks to both the mother and unborn babies
• Required practical activity 7 involves investigating the effect of a factor on human reaction time