TOPIC 5 - HOMEOSTASIS

Explain what is meant by the term ‘homeostasis’

regulation and maintenance of interal conditions; for optimum conditions for cells + enzyme activity

Describe what happens to glucose, protein and urea in the kidneys

• glucose + urea are filtered out of the blood
• protein is not filtered out
• all glucose is reabsorbed
• urea mostly is not reabsorbed -> passes out in the urine

Explain how ADH affects the production and concentration of urine by the kidneys

• increase ADH increased water reabsorption (increase permability to water)
• from kidney tubles
• so increases the conc of urine
• and decreases the volume of urine

Explain why the decrease in body temperature is an advantage to the echidna during hibernation

• loses less energy from its body (since lower temp gradient)
• so its body's energy store lasts longer + more energy available for processes vital for life

Explain how the dilation of blood vessels in the skin can help to decrease body temperature

more blood flower near the skin surface; so more heat energy is lost to the surroundings; cooling the blood which cools the body

Suggest why the athlete was advised to take salt tablets each day

to replace the ions lost in sweat

Suggest two ways to improve the students’ method for measuring human reaction time

same starting position of rule; more precise scale; repeat and calculate mean; eliminate anomalies; convert distance to time; make the student's arm rest on the table

Give ways that coordination by the endocrine system is different from coordination by the nervous system

• endocrine involves hormones via blood
• chemical transmission
• slow 
• longer-lasting

What hormone does the pituitary gland produce?

thyroxine

What hormones does the pancreas produce?

insulin; glucagon

What are the effects of adrenaline on the body?

increase heart rate; increases breathing rate; increases oxygen + glucose delivery to cells; increases respiration/ metabolism; increases sweating

Explain the use of hormones in

• contraception • the treatment of infertility

Explain how the concentration of substance Q in the blood is controlled by negative feedback

• if con of Q too high; hormone A released
• if con of Q too low; hormone B released to bring back to normal/ ideal levels

How does a production of thyroxine cause an increase in body temperature?

increases metabolic rate; so more respiratino -> releases energy

Explain why the lack of FSH in the woman’s blood caused underdeveloped breasts

lack of FSH causes lack of oestrogen; breast development is dependent on oestrogen (and other secondary sexual characteristics)

Give the reason why the student placed both sets of apparatus  with bean sprouts in the dark

to prevent the direction of light affecting the results or affecting the growth

Why use a control in the geotropism experiment?

to compare the result with; to show that gravity caused the results

How does auxin cause roots to grow downward?

uneven distribution of auxin (more on lower side); so upper side grows fasters (turns down)

Give uses of auxin

weed killers; rooting powders (so plants can grow from cuttings); promoting growth in tissue culture

Why do farmers use gibberlin?

to promote flowering; more fruit; bigger fruit

Name the type of response shown by the seedling in experiment if it grows towards the light

phototropism

Why does the temperature of the brain decrease when drinking something cold?

the blood is cooled at the stomach; and the cooled blood flows to the brain

How does the thermoregulatory centre send information to sweat glands in the skin?

via neurones/ nerve impulses

Describe the advantages and disadvantages of having a kidney transplant instead of having dialysis.
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• no need for long, regular hosptial visits
• long-term solution
• flexible lifestyle
• no risk of infection from needles
• no need to control diety
• maintains correct conc of substances in blood
• cheaper long term for NHS

Dis

Which organ monitors body temperature?

brain (thermoregulatory centre)

Which structures in the skin send impulses with info about body temp?

receptors

Describe how the body responds when a decrease in core body temperature is detected

• blood vessel supplying skin constrict (vasoconstriction)
• less blood flow to skin; so less energy is lost to surrounding
• shivering by rapidly muscle contractions
• releasing energy from respiration
• Hairs stand up; to trap air an as insulating layer
  
What is the target organ for insulin?

What is meant by the term ‘reflex action’?

an automatic response/ reaction done unconsciously

The woman moves her hand away rapidly. Describe how the woman’s nervous system coordinates the reflex action

• the receptor in the skin of her hand detects stimulus (temp change)
• electrical impuses pass along neurones
• sensory to relay to motor
• synapse between enurones where chemical (neurotransmitter) crosses the gao
• in the spinal cord/ CNS
• the effector is a muscle - contracts to pull hand away

Describe how hormones control the menstrual cycle

• FSH (pituitary) stimulated maturation of egg
• Oestrogen (ovary) inhibits FSH + stimulates LH production
• LH (from pituitary) stimulate ovulation
• progresterone (ovary) inhibits FSH + LH
• Oestrogen + progresterone maintain the uterus lining

Which gland releases the hormone that controls water loss from the body + which hormone?

Pituitary gland; ADH

How does the pituitary gland + the kidneys reduce water loss?

• higher conc of blood causes more ADH released from PG
• and ADH increases permeability of kidney tubules to water
• so increased water reabsorption back into blood

Explain biological reasons why most doctors think that a kidney transplant is a better method of treatment than dialysis

• changes in concentrations are minimised
  -  so less chance of causing damage to body cells
  -  no repeatedly puncturing skin/ blood not in contact with machine
  -  no less chance of infection, blood clots + no need to take anti-clotting drugs

Explain how the hormones insulin and glucagon control the person’s blood glucose concentration after the meal

• after meal, blood glucose increases
• insulin is secreted
• causes glucose to enter cells + glucose conversion to glycogen
• so blood glucose decreases causing glucagon secretion
• glucagon causes glycogen to be converted to glucose

A person with Type 2 diabetes often has a higher blood insulin concentration than a non-diabetic person - Why?

cells absorb less glucose; so glucose conc remains high in blood; stimulating pancreas to release more insulin

What is the purpose of thickening the lining of the uterus?

to allow implantation of the embryo

How does the contraceptive pill work?

contains hormones to stop eggs maturing

How does a diaphragm work?

Barrier to prevent sperm reaching the egg

How does a spermicidal cream work?

kill sperm

Suggest two ways a person could lower the chance of developing Type 2 diabetes?

lose weight/ maintain a healthy weight; less fat/ carbs in diet; more exercise

Describe how the oral contraceptive pill stops a woman becoming pregnant

inhibits FSH production; prevent egg maturation; prevents ovulation

What hormone are sperm stimulated by?

testosterone (produced in the testes)

What is a hormone?

a chemical messenger; made by an endocrine gland; that affects a specific target organ; and is released into the blood

What two hormones control blood glucose levels?

insulin + glucagon

Marathon runners often drink sports drinks during a race - why?

to replace the water and mineral ions lost in sweat

Where is the adrenal gland located?

on top of each kidney

Evaluate the use of the plastic IUD as a contraceptive compared to the copper IUD

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Suggest how each type of diabetes can be treated

• Type 1 -> not enough/no insulin produced -? treated with insulin injections
• Type 2 - cells don't respond to insulin -> treated with weight loss; drugs; diet + exercise

Suggest why a blood test is more reliable than a urine test

not always glucose in urine; blood tests current immediate result (urine may be hours old)

Hyperthyroidism is caused by an overactive thyroid gland. Suggest what would happen in the body of a person with hyperthyroidism

• Too much thyroxine released into the blood; raises BMR; causes inc in formation of lipids, proteins, glycogen; increase rate of respiration; increase in breakdown of excess proteins

Describe the roles of FSH and LH in the menstrual cycle

FSH causes eggs to mature and stimulate ovaries to produce oestrogen; LH stimulates the egg to be released

Why are fertility drugs given to some women?

to help them get pregnant; to stimulae egg maturation + release; own level of FSH/ LH too low

Which 2 hormones are used in contraceptive pills?

oetrogen; progesterone

Which organ monitors blood glucose levels?

pancrease

What is the effect of insulin?

causes glucose to move into cells

Explain why a transplanted organ may be rejected

• immune system; produces antibodies; attack the foreign antigens on the transplpant organ

How does the lens refract the light more?

by becoming thicker

Which two structures control the shape of the lens?

ciliary muscles + suspensory ligaments

Which two structures control the size of the iris? radial muscles + circular muscles (C contract in bright - Radial contract in dim)

To form a clear image,  what must the light rays entering the eye focus on?

the retina

When seeing a bright light - what is the receptor, coordinator and effector?

retina; brain; muscles

Which part of the brain controls balance when riding a bicycle?

cerebellum

What type of cell carries impulses from the ears to the brain?

neurone

What process occurs in the eye when looking at objects at different distances?

accomodation

Name the common defect of the eye which causes distant objects to appear out of focus? myopia (short-sightedness)

Name the part of the brain that is responsible for making a decision

cerebral cortex

Suggest how the fMRI scanner could help to find out more about the brain damage a person has

• can ask people to do different tasks while taking a scan to see which part of the brain is active/ inactive
• to compare with a person without brain damage
• traditional MRI scanners can't be used if a person can't stay still or is claustrophobic

Describe how the brain receives information about light entering the eye

• cells in the retina sensitive to light; detect the light + impluse passes along the sensory neurone; along the optic nerve to the brain

Explain how the person’s eye could adjust to form a clear image of a nearer object

• ciliary muscles contract; to have a smaller diameter; suspensory ligaments slaken; lens thickens; lens is more convergent; light rays are refracted more to focus image on retina

Explain why a long-sighted person has difficulty seeing near objects clearly

eye-ball is too short; lens can't be thickened enough -> so light focuses/ forms behind retina

Describe how spectacle lenses can correct long-sightedness

convex/ converging lens; light rays refracted inwards more; to focus light rays on retina

Describe a reflex action

• receptor detects stimulus
• sends in electrical signal/ impulse
• neurones conduct impules
• sensory to the spinal cord 
• synapse between neurones where chemical crosses + stimulates impulses in relay neurones
• to motor neurone; effector carries out respons

Example of effectors

muscles (contracting); glands (secreting chemicals)

How do pupils dilate?

dilate in dim light; cause circular muscles in iris relax; and radial muscles contract

Why is a colour change in a computing better than if a human was doing it?

there's no indication before hand when the colour will change (can measure time more precise)

Describe the difference between the function of a receptor and the function of an effector

• receptors detect a stimulus + convert it into an impulse
• eg

What is a synpase?

a junction, gap between neurones

Describe how information passes across a synapse?

as a chemical release from one neurone, pass to the next neurone and stimulates an impulse

Name a sense organ involved in a reflex co-ordinated by the spinal cord

skin

What are some factors, seedlings compete for?

light; water; mineral ions

Which tropism causes the seedling to grow towards light?

Phototropism

Which hormone causes the seedling to grow towards the light?

auxin

What are uses of gibberlin?

to increase fruit size; promote flower production; seed germination

How do seedlings grow towards the light?

one side receives more light; so unequal distribution of auxin, there is more growth on the side away from the lamp (more auxin on the side away from light); bends towards light

What is ethene used for in plants

to help ripen fruits

Why does storing bananas with other fruits cause the other fruits to ripen faster?

ethene is released from bananas

What is Phototropism?

It is a growth response by part of a plant to light

What is geotropism/ gravitropism?

a growth response to gravity

Plan an investigation to show the effect of light from one direction on the growth of plant seedlings

• several seedlings in each batch
• measure the heights of the shoots
• leave some the dark with light from one side
• controls

Explain how phototropism in a plant shoot helps the plant to survive

plants absorbed more light; more PS; produces more glucose

What should you keep constant during the light growth experiment?

the volume of water added to the soil; the temperature

What chemical is used To reduce the time taken for tomatoes to ripen?

ethen