Homeostasis

• homeostasis is the maintenance of a state of dynamic equilibrium in the body, dispite changes in the internal conditions
• changes in the body are detected by receptors and sends messages to effectors, usually muscles and glands
• feedback systems can be hormones, nerve impulses and separate mechanisms
• positive feedback system works as: brain stimulates pituitary to release oxytoxin, then makes uterus contract harder pushing baby against cervix, baby stretches cervix and sends impulse to brain
• afferent pathways carry impulses into CNS
• efferent pathways carry nerve impulses away from CNS to effectors
• if theres high pH in the body, youll have twitching, vomiting and need isotonic sodium chloride solution
• high pH in the body is called alkalosis
• if theres low pH in the body you get tremors, headahces and need to infuse bicarbonates before it leads to death
• low pH in the body is called acidosis
• if you have high temperature then you become drowsy and have slurred speech. you need to be hydrated and cooled quickly before you die
• high temperature of the body is also known as hyperthermia
• if you have a low temperature then you feel drowsy and have a weak pulse. you need warm drinks and blankets before you die
• low temperature of the body is also known as hypothermia
• high water in the body means you have confusion and seizures so you should stop drinking before you die
• high water in the body is called hyponatremia
• low water in the body means youll have rapid breathing and fainting. you need clear fluids before you die
• low water in the body is also known as dehydration
• chemical control is produced in endocrine glands and releases hormones into the blood
• exocrine glands produce chemicals and release them along small tubes or ducts
• exocrine glands produce secretions of the guts
• the pituitary gland produces secretions that affect the activity of other endocrine glands
• the thyroid gland uses iodine from food to regulate the way the body uses energy
• the parathyroid gland produces hormones that help control amount of calcium. its located behind the thyroid
• the pancreas is a digestive exocrine gland and excretes an enzyme to breakdown protein, lipids and nucleic acid
• the adrenal glad produces adrenaline, steroids and cortisol
• the ovaries produce ova, secrets oestrogen vital for reproduction and fertility
• the testes secrete testosterone for the development of male characteristics
• the hypothalamus controls activity of all the other glands, monitors blood sensory cells
• the posterior pituitary gland stores hormones for releasing later
• the anterior pituitary gland inhibits the release of hormones
• auxins are produced in young shoots and suppresses lateral growth
• auxins are synthesised in meristem cells, diffused away from the tip, bind to receptor sites, activate hydrogen ions to pump into cel membrane, then destroyed by enzymes
• gibberelins are growth regulators that stimulate growth and production of fruit
• after a seed absorbs water and wells, it secretes giberellins that diffuse to aleurone layer, then produces amylase to break down things for food then startsto germinate
• cytokinins are growth regulators that promote cell division and combined with ethene is responsible for fruit
• synergistic means work together. auxin and gibberellins work together to encourage elongation of the stem
• antagonistic means work against. auxin supresses cytokinins and want lateral growth
• apical dominance is when one lead shoot grows bigger and faster than the other as its inhibited
• abscission is the shedding of leaves after the formation of abscission zone across the stem