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Define homeostasis Regulation of internal conditions of a cell / organism (in response to internal / external changes) To maintain optimum conditions for function

Why is homeostasis important To maintain optimum conditions for enzyme action and all cell functions

Give 3 examples of conditions regulated in the human body Blood glucose levels Body tempurature Water level

Describe an automatic control system Receptor cells eg. temperature receptor Detect a stimulus (a change in environment)Coordination centre eg. brain, spinal cord, pancreas Receive & process information from receptorsEffectors - muscles or glands ● Bring about responses to restore optimum levels

What does the nervous system enable organisms to do React to changes in their surroundings Coordinate their behaviour

What is the CNS Central nervous system (CNS) - brain & spinal cord (billions of interconnected neurones)

Describe how information passes along neurones (nerve cells) As electrical impulses

What is a synapse? Small gap between 2 neurones

Describe how information pass across a synapse When electrical impulse reaches end of neurone 1, a chemical is releasedChemical diffuses across synapseChemical attaches to neurone 2, triggering another electrical impulse

Describe the steps involved in a nervous system response to a stimulus Receptor - Detects a stimulus intiating an electrical impulseSensory neurone - Passes information from receptors → CNS as electrical impulsesCNS - Coordinates response of effectorsMotor neurone - Passes information from CNS to the effectors as an electical impulseEffectors - Muscles contract or glands secrete hormones Between neurones, information passes across a synapse as a chemicals

What is a reflex action and why are they important? Automatic and rapid response ○ As doesn’t involve conscious part of the brainImportance - protective; help minimise damage to body

Describe how a reflex action occurs via a reflex arc Receptor - Detects stimulus, initiates an impulseSensory neurone - Passes info from receptors → CNS as impulseRelay neurone - In spinal cord passes impulses from sensory to the motor neuroneMotor neurone - Passes information from CNS to effectors as impulsesEffectors - Muscles contract or glands secrete hormones Between neurones, information passes across a synapse as a chemicals

What does the brain control The brain controls complex behaviour It is made of billions of interconnected neurones.

Cerebral cortex Consciousness, intelligence, memory and language

Cerebellum Muscle coordination, movement and balance

Medulla Regulates unconscious activities eg. heartbeat and breathing

Describe methods used by neuroscientists to map regions of the brain to particular functions Studying patients with brain damage - Observe symptoms / changes in behaviour → indicate function of damaged regionElectrically stimulating different parts of the brain - Observe effects on behaviour in live patients → indicate function of stimulated regionUsing MRI scanning techniques - Observe which parts most active during different activities → indicate region linked to activity

Explain the difficulties of investigating brain function and treating brain damage and disease Brain is very delicate → surgery may cause unintended damage to another areaBrain is very complex → difficult to work out exactly which parts carry out specific functions

What is the eye As sense organ that contains receptor cells sensitive to light and colour

Retina Contains receptors sensitive to light intensity/colour → send impulses to optic nerve

Optic nerve Made of many neurones → carries electrical impulses from retina to brain

Sclera white outer layer → protect eye

Cornea Transparent and curved layer at front of eye → refracts light into the eye

Lens Flexible + transparent biconvex disc → focuses light onto retina

Iris Ring of muscle → controls pupil (hole) diameter so how much light enters eye

Ciliary muscle Muscles connected to lens → contract to change lens shape

Suspensory ligament Connect lens to ciliary muscles → help control lens shape

Explain the response to dim light Pupil dilates (increases in diameter)In the iris:Radial muscles contractCircular muscles relaxEffect: More light enters the eye for better vision in low-light conditions

Explain the response to bright light Pupil constricts (decreases in diameter)In the iris:Circular muscles contractRadial muscles relaxEffect: Less light enters the eye to protect the retina from excessive light

What is accommodation Changing shape of lens to focus on near or distant objects

Explain how the eye focuses on a near object Ciliary muscles contract (so smaller diameter)Suspensory ligaments loosen Lens thickens (becomes more curved)Lens becomes more convergent / refracts light rays moreLight rays focus on the retina

Explain how the eye focuses on a distant object Ciliary muscles relax (so larger diameter)Suspensory ligaments pull tightLens is pulled thinLens is less convergent / refracts light rays lessLight rays focus on the retina

What is myopia Short sightedness

Cause and correction of myopia Cause:Rays of light from distant objects focus in front of the retinaEyeball too long / lens too thick Correction:Concave lenses (thinner in the middle)Light rays diverge/bend outwards moreSo light rays focus on the retina

What is hyperopia Long-Sightedness

Cause and correction for hyperopia Cause:Rays of light from near objects focus behind the retinaEyeball too short / lens too thin Correction:Convex lenses (thicker in the middle)Light rays refracted/bend inwards moreSo light rays focus on the retina

Describe new technologies to treat eye defects Hard (longer lasting) and soft (more comfortable, disposable) contact lensesLaser eye surgery - changes cornea shapeReplacement lenses in eye

What monitors and controls body temperature? Thermoregulatory centre in the brain

How is temperature monitored by the body? Thermoregulatory centre contains receptors sensitive to temperature of blood (flowing through brain)Skin contains temperature receptors and sends nervous impulses to thermoregulatory centre

Explain the changes that occur when body temperature is too high Blood vessels supplying skin dilate (vasodilation) → more blood flow to skin (capillaries) → more heat / energy lost → cools blood which cools bodySweat produced from sweat glands → evaporates, causing coolingEffect: Energy transfers from skin to the environment, lowering body temperature

Explain the changes that occur when body temperature is too low Blood vessels supplying skin constrict (vasoconstriction) → less blood flows through skin → less heat lostSkeletal muscles contract (and relax) rapidly (shivering) → more respiration, more energy releasedSweatings stops → less evaporation and cooling Effect: Reduces heat loss and increases heat production, raising body temperature

What is the endocrine system? A system of (endocrine) glands which secrete hormones directly into the bloodstream

What is a hormone Chemical messenger secreted by a gland Travels in blood to a target organ where it produces an effect

Pituitary Many eg. FSH / LH Thyroid Thyroxine Adrenal Adrenaline Pancreas Insulin / glucagon Ovaries Oestrogen / progesterone Testes Testosterone

Why is the pituitary gland referred to as the ‘master gland’? Secretes several hormones into blood (in response to body conditions) which Act on other glands to stimulate release of other hormones to bring about effects

Describe how coordination by the endocrine system is different from coordination by the nervous system Endocrine system effects are slower but longer-lasting than nervous systemEndocrine system uses hormones in blood, nervous system uses electrical impulses in neurons

What organ monitors and controls blood glucose concentration? The pancreas

Explain how the pancreas responds when blood glucose conc. is too high Pancreas secretes the hormone insulinInsulin causes glucose to diffuse from blood to liver and muscle cellsWhere excess glucose is converted into glycogen for storageSoblood glucose concentraction decreases

Explain how the pancreas responds when blood glucose conc. is too low Pancreas secretes the hormone glucagon Glucagon triggers breakdown of glycogen into glucose in liver cellsGlucose diffuses into bloodSo blood glucose concentration increases

How is blood glucose conc. controlled using negative feedback? When blood glucose conc. rises or falls below optimum, a hormone is secreted by the pancreas Action of either hormone returns conc. to optimum / normal

What is Type 1 diabetes and how is it normally treated? Pancreas fails to produce sufficient insulin → uncontrolled high blood glucoseTreatment - insulin injections

What is Type 2 diabetes and how is it normally treated? Pancreas produces insulin but body cells no longer respond to it → uncontrolled high blood glucoseTreatment - carbohydrate-controlled diet, regular exercise regime (as glucose used in respiration)

Risk factor for type 2 diabetes Obesity

Explain why water and ions need to be balanced in the body If body fluid too concentrated (ie. low water content) → cells lose too much water by osmosis → shrinkIf body fluid too dilute (ie. high water content) → cells gain too much water by osmosis → swell / burst

How are water, ions and urea lost from the body? Water via the lungs during exhalation - no controlWater, ions and urea from skin in sweat - no controlExcess water, ions and urea are removed via the kidneys in urine - controlled

What causes excess amino acids in the body and how are these excreted (removed) safely? Digestion of proteins (made up of amino acids) in dietExcess amino acids deaminated in liver to form ammoniaAmmonia is toxic so immediately converted to ureaUrea excreted from body via urine (filtered by kidneys)

Describe how a healthy kidney produces urine Filtration of blood (entering kidney tubules) - Water, glucose, ions, urea pass through filter into kidney tubules - Proteins / blood cells too large to pass through (remain in blood)Selective reabsorption (back into blood) - All glucose, some ions / water, no urea reabsorbed (urea released in urine)

Describe how the water level in the body is controlled Higher concentration of blood (low water level) causes ADH (hormone) release from pituitary glandADH increases permeability of kidney tubules to waterSo more water reabsorbed (back into blood by osmosis)So smaller volume of more concentrated urine producedControlled by negative feedback - pituitary gland stops releasing ADH when blood becomes more dilute, leading to a higher volume of more dilute urine

Explain the consequences of kidney failure Toxic / waste substances build up eg. urea → poisonous Incorrect water balance / ion concentration → cells damaged by osmosis

What are the two main ways of treating kidney failure? Kidney dialysis and kidney transplant (from donor)

Describe the basic principles of dialysis Blood passes over partially permeable membrane (separating dialysis fluid) Dialysis fluid contains same conc. of glucose / ions as healthy blood, but no urea - So all urea, some ions / water, no proteins are filtered out of blood

Advantages of kidney transplant No need for regular / long hospital visits or is a long-term solutionFlexible lifestyle, such as can go on holidaysNo risk of infection from frequent needles / treatmentLess / no need to control dietMaintains correct concentration of substances in blood / body (toxic substances build up between dialysis sessions)Cheaper long term for NHS / hospital

Disadvantages of kidney transplant May be rejectedHave to keep taking immunosuppressant drugsSuitable donor may not be availableRisk from surgery (e.g. anaesthesia or infection)Recovery from surgery will take a long timeDoes not last forever (therefore further surgery needed)

What happens during puberty? Reproductive hormones cause secondary sexual characteristic to develop In females eggs begin to mature and one is released every 28 days

What is ovulation It is when egg is released every 28 days

FSH Source: Pituitary glandFunction:Stimulates maturation of an egg in ovary (first days)Stimulates oestrogen production

Oestrogen Source: OvariesFunction:Causes thickening of uterus lining (first half)Inhibits FSH productionStimulates LH production

LH (Luteinising Hormone) Source: Pituitary glandFunction:In high levels, stimulates ovulation (release of mature egg) (day 14)Stimulates progesterone production (empty egg follicle)

Progesterone Source: OvariesFunction:Maintains uterus lining (second half)Inhibits FSH and LH production

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Explain how fertility drugs increase chance of pregnancy Contain FSH → stimulate egg maturationContain LH → stimulate release of mature eggs (ovulation)More eggs released → increased chance of fertilisation

Explain how fertility drugs increase chnace of pregnancy Contains FSH which stimulates egg maturation Contains LH which stimulates release of mature eggs More eggs are released thereefore an increased change of fertilisation

Explain how IVF increases chance of pregnancy Mother is given FSH & LH to stimulate maturation of several eggs Eggs are collected from the motherEggs are then fertilised by sperm from father in laboratory Fertilised eggs develop into embryosWhen they are tiny balls of cells , 1 or 3 embryos are inserted into the mothers uterus

What has allowed IVF to develop Development of microscopy techniques

Describe the issues with IVF treatment It is very emotionally and physically draining Success rates are not that highCan lead to multiple birth which is a risk to babies and the motherGenetic testing can be misuesd in choosing characteristics of offsprings

Advantages of IVF Fertility treatments can give a couple the chance to have a baby of their own, which is a big positive

Explain the role of adrenaline in negative feedback It is produced by the adrenal glands in times of fear and stressIt increases heart rate + breathing rate + glycogen break down in the riverTo boost delivery of oxygen and glucose to the brain and muscles So more energy can be released via respiration To prepare the body for ‘fight or flight’To prepare the body for ‘fight or flight’

Describe the role of the hormone thyroxine in the body It is released from the thyroid glandStimulates BMR Plays an important role in growth and development

What is BMR Basal metabolic rate Speed at which chemical reactions in the body occur, at rest, eg. respiration, formation of glycogen, lipids and proteins

Describe what happens in negative feedback Receptor cells detect level are too low or too highEffectors respond to counteract change Levels are restored to normal

Describe how thyroxine is controlled by negative feedback when it is lower than normal Pituitary gland scretes more TSHStimulating thyroid to realese more thyroxine So levels in blood rise to normal

Describe how thyroxine is controlled by negative feedback when it is higher than normal Thyroine inhibits secretion of TSH from pituitary glandLess thryoxine release from thryoid glandLevels in blood decrease back to normal

• This process ensures that the body's metabolism remains balanced and efficient, allowing for the proper functioning of physiological processes.