Homeostasis and Response
- Created by: benitaxx
- Created on: 18-02-18 17:21
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- Homeostasis and Response
- Homeostasis and body temperature
- Homeostasis
- The maintenance of a constant internal enviroment
- Body temperature
- Blood glucose concnetration
- Water and Ion levels
- Keeps conditions constant for enzyme action and cell functions
- The maintenance of a constant internal enviroment
- Control centres
- Have cells called receptors that detect change in enviroment
- This mechanism is called negative feedback
- Co-ordination centers which receive and process info from receptors
- This mechanism is called negative feedback
- Receptors which bring levels back to optimum
- Have cells called receptors that detect change in enviroment
- Body temperature
- Human body temperature should be kept around 37 degrees
- This is the optimum temperature for enzymes
- The thermoregulatory system in the brain:
- Monitors and controls body temp
- Has receptors that monitor temp of blood flowing through brain
- Receives information from temperature receptors i the skin
- If body temperature gets too low
- Blood vessels narrow
- Vasoconstriction
- Sweating stoops
- Skeletal muscles contract and relax quickly transferring more heat to blood
- Shivering
- Blood vessels narrow
- Human body temperature should be kept around 37 degrees
- Homeostasis
- The nervous system and the eye
- The nervous system
- Enables humas to react to their surroundings and coordiante better
- How it works:
- Pain stimulus is detected by receptors
- Impulses pass along sensory neuron to CNS
- Impulse passes through relay neuron
- Motor neuron carries impulse to effector
- Effector responds by drawing limb away from source of pain
- Motor neuron carries impulse to effector
- Central nervous system- brain and spinal cord
- Impulse passes through relay neuron
- Impulses pass along sensory neuron to CNS
- Pain stimulus is detected by receptors
- Brain and the eye
- The brain controls complex behavior and has 3 main regions
- Cerebral cortex- responsible for consciousness, language, memory and intelligence
- Cerebellum-Coordinates movement and balance
- Medulla- controls automatic actions such as heartbeat and breathing
- The eye is an organ and in it:
- Retina-contains receptor cells sensitive to light
- Optic nerve carries impulses from retina to brain
- Sclera forms a tough outer layer with front region called cornea
- Iris controls size of pupil and amount of light hitting retina
- Ciliary muscles and sensory ligaments change shape of lense to focus light on retina
- The brain controls complex behavior and has 3 main regions
- Accomodation
- The process of changing the shape of the lense to focus on a near or distant object
- To focus on a near object:
- Ciliary muscles contract
- Suspensory ligaments loosen
- To focus on a far object
- Ciliary muscles relax
- Suspensory ligaments pulled tight
- Lens is pulled thin and only slightly refracts light rays
- Required practical
- Drop a ruler and see how fast you can catch it. Record results by looking at the number your fingers land on
- The further the ruler travels, the slower the reaction time of the participant
- Defects of the eye
- Myopia (short sighted)
- Can generally be treated with glasses
- New technologies include laser surgery and contact lenses
- Can generally be treated with glasses
- Hyperopia (long sighted)
- Can generally be treated with glasses
- New technologies include laser surgery and contact lenses
- Can generally be treated with glasses
- Myopia (short sighted)
- The nervous system
- Hormones and Homeostasis
- The endocrine system
- Made up of glands that secrete hormones back into bloodstream
- Hormones are chemical messengers carried in the blood, to an organ where they produce an effect
- The effect of hormones are slower and act for longer than the nervous system
- The pituitary gland in the brain is the master gland
- Secretes several hormones in response to body conditions
- Adrenaline
- Produced in adrenal glands in times of fear
- Prepares for 'fight or flight'
- Increases heart rate., increasing the delivery of oxygen and glucose to orgnas and muscles
- Thyroxine
- Produced in thyroid gland
- Increases metabolic rate
- Controls growth and development in young animals
- Controlled by negative feedback
- Made up of glands that secrete hormones back into bloodstream
- Control of blood glucose
- Blood glucose concentration is monitored and controlled by pancreas
- If blood glucose is too high:
- Pancreas releases more insulin
- Insulin caused glucose to be from blood into cells
- In liver and muscle cells excess glucose is converted into glycogen for storage
- Pancreas releases more insulin
- If blood glucose is too low:
- Pancreas releases glucagon
- Stimulates glycogen to be converted into glucose
- Pancreas releases glucagon
- Water Balance
- The control of water levels in the body is an example of negative feedback
- Water leaves the body through lungs when breathing, sweat through skin and in urine
- The balance of water and ions is regulated by the kidneys who also excrete urea, produced by the liver from breakdown of proteins
- Kidneys produce urine by:
- Filtering blood
- Selective absorption of useful substances e.g. glucose
- Takes place in millions of tiny tubes called tubules
- Leaves urea, excess water and ions to form urine
- Takes place in millions of tiny tubes called tubules
- Selective absorption of useful substances e.g. glucose
- Selective absorption of useful substances e.g. glucose
- Leaves urea, excess water and ions to form urine
- Leaves urea, excess water and ions to form urine
- Filtering blood
- If kidneys fail a transplant can be offered
- Patient has to be on anti rejection drugs for rest of life
- Until transplant is available, a patient may be offered dialysis
- A machine that does the kidneys fuction
- Is very time consuming as it must happen 3 times a week for up to 8 hours
- Digestion of food proteins results in excess amino acids
- In liver, amino acids converted to ammonia- deamination
- Ammonia is toxic so is quickly converted into urea
- In liver, amino acids converted to ammonia- deamination
- Kidneys produce urine by:
- Water level in the body is controlled by a hormone ADH
- Released by pituitary gland when blood concentration is too high
- Passes in blood, to kidney tubles where it causes more water to be absorbed by blood
- The endocrine system
- Hormones and reproduction
- Sex hormones
- Oestrogen (found in the ovaries) is the main female sex hormone
- Testosterone (produced in the testes) is the main male sex hormone
- Control of the menstrual cycle
- Follicle stimulating hormone (FSH)
- secreted by pituitary gland
- matures eggs
- Stimulates ovaries to produce oestregen
- Oestregen
- Inhibits FSH release
- Stimulates LH release
- Makes lining of uterus regrow after menstruation
- Luteinising hormone (LH)
- Secreted by pituitary gland
- Stimulates ovulation
- Progesterone
- Secreted by empty follicle in ovaries
- Maintains lining of uterus
- Inhibits FSH and LH release
- Follicle stimulating hormone (FSH)
- Reducing fertility
- Hormonal methods
- Oral contraceptives that contain Oestrogen and progesterone
- Inhibits FSH release so no eggs are released
- Injection, implant or skin patch
- To slow release progesterone to stop release of eggs
- Oral contraceptives that contain Oestrogen and progesterone
- Non-hormonal methods
- Spermicidal creams
- Kill sperm
- Not having intercourse during ovulation
- surgical methods
- Contraception
- intrauterine devices
- stop embryos implanting into uterus
- Spermicidal creams
- Hormonal methods
- Increasing fertility
- FSH and LH can be given in a drug to stimulate release of egg
- In Vitro fertilisation (IVF) involves:
- Giving woman FSH and LH to stimulate growth of may eggs
- Collecting eggs
- Fertilising eggs from fathers sperm
- Inserting 1 or 2 embryo's into the uterus
- Fertilising eggs from fathers sperm
- Collecting eggs
- Giving woman FSH and LH to stimulate growth of may eggs
- Problems with IVF
- Emotionally and physically stressfull
- Success rates are not high
- Can lead to multiple births-high risk
- Sex hormones
- Plant hormones
- Functions of plant hormones
- roots and shoots growing towards or away from a stimulus
- Ripening of fruits
- Tropism
- When a pant grows in a particular direction
- Controlled by a group of plant hormones called auxins
- Phototrphism
- response to light
- More light reaches one side of shoot
- More auxin sent down shaded side of root
- Cells on shaded side elongate more
- The shoot grows towards light
- Cells on shaded side elongate more
- More auxin sent down shaded side of root
- Gravitropism
- Response to gravity
- Auxin moves to one side of root
- Growth becomes inhibitted
- Root grows downwards
- Growth becomes inhibitted
- Required practical
- Plant 10 cress seeds in each plastic container with a hole in one side. Place in even lighting and leave for several days
- Look at what directions the roots and shoots grow in
- Uses of plant auxins
- weed killers
- Makes weeds grow so quick they exhaust food supply
- Rooting powers
- Promoting growth in tissue culture
- weed killers
- Ethene
- Gas and plant hormone
- Controls ripening fruits
- Gibberellines
- Increase fruit size
- Initiate germination
- Promote flowering
- Functions of plant hormones
- Homeostasis and body temperature
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