revision pack topic 5 – homeostasis and response · 2020-03-17 · hormonal coordination in...

Revision Pack Topic 5 – Homeostasis and Response

Homeostasis and response R/A/G Homeostasis Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

Homeostasis maintains optimal conditions for enzyme action and all cell functions. In the human body, these include control of: • blood glucose concentration • body temperature • water levels. These automatic control systems may involve nervous responses or chemical responses. All control systems include: • cells called receptors, which detect stimuli (changes in the environment) • coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors • effectors, muscles or glands, which bring about responses which restore optimum levels.

The human nervous system Structure and function Explain how the structure of the nervous system is adapted to its functions. The nervous system enables humans to react to their surroundings and to coordinate their behaviour. Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS is the brain and spinal cord. The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.

Reflex actions are automatic and rapid; they do not involve the conscious part of the brain. A reflex arc consisting of the sensory, relay and motor neurones controls the response of the body when exposed to a stimulus.

Required practical activity 7: plan and carry out an investigation into the effect of a factor on human reaction time.

Hormonal coordination in humans Human endocrine system The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream. The blood carries the hormone to a target organ where it produces an effect. Compared to the nervous system the effects are slower but act for longer.

The pituitary gland in the brain is a ‘master gland’ which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects.

Identify the position of the following on a diagram of the human body:


• pituitary gland • pancreas • thyroid • adrenal gland • ovary • testes. Control of blood glucose concentration Blood glucose concentration is monitored and controlled by the pancreas. If the blood glucose concentration is too high, the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage. Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.

Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.

In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas. A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes.

If the blood glucose concentration is too low, the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.

Hormones in human reproduction During puberty reproductive hormones cause secondary sex characteristics to develop. Oestrogen is the main female reproductive hormone produced in the ovary. At puberty eggs begin to mature and one is released approximately every 28 days. This is called ovulation. Several hormones are involved in the menstrual cycle of a woman. • Follicle stimulating hormone (FSH) causes maturation of an egg in the ovary. • Luteinising hormone (LH) stimulates the release of the egg. • Oestrogen and progesterone are involved in maintaining the uterus lining.

Testosterone is the main male reproductive hormone produced by the testes and it stimulates sperm production.

Explain the interactions of FSH, oestrogen, LH and progesterone, in the control of the menstrual cycle.

Contraception Fertility can be controlled by a variety of hormonal and non-hormonal methods of contraception. These include: • oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature


• injection, implant or skin patch of slow release progesterone to inhibit the maturation and release of eggs for a number of months or years • barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg • intrauterine devices which prevent the implantation of an embryo or release a hormone • spermicidal agents which kill or disable sperm • abstaining from intercourse when an egg may be in the oviduct • surgical methods of male and female sterilisation.The use of hormones to treat infertility Explain the use of hormones in modern reproductive technologies to treat infertility. This includes giving FSH and LH in a ‘fertility drug’ to a woman. She may then become pregnant in the normal way.

In Vitro Fertilisation (IVF) treatment. • IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs. • The eggs are collected from the mother and fertilised by sperm from the father in the laboratory. • The fertilised eggs develop into embryos. • At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).

Although fertility treatment gives a woman the chance to have a baby of her own: • it is very emotionally and physically stressful • the success rates are not high • it can lead to multiple births which are a risk to both the babies and the mother.

Negative feedback Adrenaline is produced by the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.

Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development.

Thyroxine levels are controlled by negative feedback.


Homeostasis

Define what is meant by the term homeostasis

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State the 3 different conditions inside the body which are controlled by homeostasis

1. ……………………………………………………………

2. ……………………………………………………………

3. …………………………………………………………….

What do all control systems include?

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Hormones and the endocrine system:

What are hormones?

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Where are hormones produced?

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What is a target organ?

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Label the diagram below and identify the hormones produced by each gland.

What is the name of the gland below?

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Describe what the gland secretes and the effect it has on the body.

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Control of blood glucose concentration.

Blood Glucose Regulation

Name the two hormones which control blood glucose levels:

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Complete the table about how the body responds to different blood glucose levels

Blood glucose level

How does pancreas respond?

What happens in the liver?

As a result what happens to blood glucose level?

Too High

Too Low

What is the difference between glucose and glycogen?


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Describe and explain the shape of this graph

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Diabetes:

Complete the table below to show the difference between the two types of diabetes.

Type of Diabetes Causes Symptoms Treatment

Type 1

0

5

10

15

20 40 60 80 100 120 140 160 180 200

Blood Glucose Levels

Minutes After Eating

Blood Glucose Levels


Type 2

The human nervous system

What is the job of a nerve cell?

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Label the diagram of the nerve cell below.

Complete the table below using the diagram to identify the features of a nerve cell which

allow it to carry out its function.

Cell Part Function


What is a neurone?

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What is the difference between a sensory, relay and motor neurone?

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Reflexes

Label the diagram below and complete the flowchart below.


Draw a flowchart for the example below using the above template.

1) A person sitting on a pin

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Required Practical: Investigating the effect of caffeine on human reaction time.

Write a method to investigate the above statement. Include in your answer the IV and DV and any controls taken. Explain how you will ensure your results are valid. .................................................................................................................................................................

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Hormones in human reproduction

Label the female reproductive system:

How long is a woman’s menstrual cycle?

What is menstruation?

What controls the menstrual cycle?

Hormones involved in the menstrual cycle:

Name Role Gland Effector gland


Why is the menstrual cycle an example of a negative feedback system?

Complete the table to summarise the effects further:

Effect FSH LH Progesterone Oestrogen Stimulates oestrogen production Inhibits FSH production Causes uterus lining to thicken Causes a follicle to mature Stimulates LH surge Stimulates ovulation Maintains uterus lining

What is the advantage of maintaining a high level of progesterone during pregnancy?

The use of hormones to treat infertility

What is fertility?


Fertility Treatments

Describe the process of IVF to treat fertility:

1.

2.

3.

4.

Summarise and evaluate alternative fertility treatments:

Fertility Treatment Description: Advantages: Disadvantages:

Surrogacy

Egg donation

Artificial insemination

Ovary transplants

Hormones


Homeostasis and Response Exam Questions

Q1.This question is about the nervous system.

(a) Describe the function of receptors in the skin.

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........................................................................................................................(2)

(b) A response is caused when information in the nervous system reaches an effector.

(i) There are two different types of effector.

Complete the table to show:

• the two different types of effector

• the response each type of effector makes.

(4)

(ii) Some effectors help to control body temperature.

Give one reason why it is important to control body temperature.

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........................................................................................................ (1)(Total 7 marks)

Q2. It is important that the concentration of glucose (sugar) in the blood is controlled.

(a) (i) Which hormone controls the concentration of glucose in the blood?

...............................................................................................................(1)

(ii) Which organ produces this hormone?

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(b) The concentration of glucose in the blood of two people, A and B, was measured every half an hour.

One hour after the start, both people drank a solution containing 50 g of glucose.

The graph shows the result.


(i) By how much did the blood glucose concentration in person B rise after drinking the glucose drink?

.................................................. mg per 100 cm3 of blood (1)

(ii) A doctor suggests that person A has diabetes.

Give two pieces of evidence from the graph to support this suggestion.

1 ............................................................................................................

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2 ............................................................................................................

...............................................................................................................(2)


(iii) Give one reason for the fall in blood glucose concentration in person B, shown in the graph.

.....................................................................................................(1)(Total 6 marks)

Q3. Insulin controls blood glucose concentration.

(a) The rate at which blood glucose concentration changes is affected by the food eaten.

In an experiment a person who does not have diabetes ate two slices of white bread. The change in her blood glucose concentration was recorded over the next 120 minutes. The experiment was repeated; first with two slices of brown bread and then with two slices of wholemeal bread.

The graph shows the results of the three experiments.

(i) Which type of bread would be most suitable for a person with diabetes?

Type of bread .......................................................................................

Give two reasons for your answer.

1 ........................................................................................................................

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2 ........................................................................................................................

...........................................................................................................................(2)

(ii) Explain, as fully as you can, the reasons for the changes in blood glucose concentration


when the person ate the brown bread.

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(b) Pancreatic-cell transplantation is a new treatment for diabetes. Insulin-making cells are taken from up to three dead donors. The cells are kept alive before being injected into the diabetic in a small operation. The cells soon begin to make insulin.

In one recent study 58 % of recipients of pancreatic-cell transplants no longer needed insulin injections.

Give the advantages and disadvantages of the new treatment for diabetes compared with using insulin injections.

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....................................................................................................................(3)(Total 9 marks)

Q4.The diagram shows the structures involved in the knee-jerk reflex. When the person is hit at point P, the lower leg is suddenly raised.


(a) Name the structures labelled A, B and C.

A ....................................................................................................................

B ....................................................................................................................

C .................................................................................................................... (3)

(b) How is information passed across a synapse?

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........................................................................................................................ (1)

(c) What is the effector in this response?

........................................................................................................................ (1)

(Total 5 marks)

Revision Pack Topic 5 – Homeostasis and Response Q5.The diagram shows the position of two glands, A and B, in a woman.

(a) (i) Name glands A and B.

A ......................................................................

B ...................................................................... (2)

(ii) Gland A produces the hormone Follicle Stimulating Hormone (FSH).

FSH controls changes in gland B.

How does FSH move from gland A to gland B?

............................................................................................................... (1)

(b) (i) A woman is not able to become pregnant. The woman does not produce mature eggs. The woman

decides to have In Vitro Fertilisation (IVF) treatment.

Which two hormones will help the woman produce and release mature eggs?

Tick ( ) one box.

FSH and Luteinising Hormone (LH)

FSH and oestrogen


Luteinising Hormone (LH) and oestrogen (1)

(ii) Giving these hormones to the woman helps her to produce several mature eggs. Doctors collect the mature eggs from the woman in an operation.

Describe how the mature eggs are used in IVF treatment so that the woman may become pregnant.

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(iii) IVF clinics have been set a target to reduce multiple births.

At least 76% of IVF treatments should result in single babies and a maximum of 24% of treatments should result in multiple births.

Suggest one reason why the clinics have been set this target to reduce multiple births.

...............................................................................................................

............................................................................................................... (1)


(c) Two clinics, R and S, used IVF treatment on women in 2007. Doctors at each clinic used the results of the treatments to predict the success rate of treatments in 2008.

The table shows the information.

Total number of IVF treatments in 2007

Number of IVF treatments resulting in pregnancy in 2007

Predicted percentage success

rate in 2008

Clinic R 1004 200 18–23

Clinic S 98 20 3–56

(i) Compare the success rates of the two clinics in 2007.

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............................................................................................................... (1)

(ii) The range of the predicted success rate in 2008 for clinic R is much smaller than the range of the predicted success rate for clinic S.

Suggest why.

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............................................................................................................... (2)

(Total 11 marks)


Mark Scheme

M1.(a) detect changes in surroundings or detect stimuli

allow any named stimulus for skin 1

convert information to impulse

allow send impulse to sensory neurones / brain 1

(b) (i)

muscle contract(ion)

gland release / secrete / produce chemical / hormone / enzyme

1 mark for each effector

1 mark for each response

response must match type of effector (if given)

ignore examples

ignore relax(ation) / movement for contraction

do not allow expansion for muscles 4

(ii) any one from:

• (maintain temperature at which) enzymes work best • so chemical reactions are fast(est) • prevent damage to cells / enzymes

allow prevent enzymes being denatured (by temperature being too high)

1 [7]


M2. (a) (i) insulin

accept glucagon (correct spelling only) 1

(ii) pancreas

accept phonetic spelling

allow pancrease 1

(b) (i) 11(.0)

accept in range 10.5-11 (.0) 1

(ii) any two from:

ignore numbers unless comparative

• high(er) concentration (of blood glucose) (anywhere / any time)

accept 115 not 88

139 not 99

• large(r) increase (in concentration after the drink)

accept increase by 24 not 11 / their b(i)

• fast(er) / steep(er) rise

accept it takes 3 hours not 1 ¼ hours to get back to original level

accept it takes a long time to get back to normal

• slow(er) fall 2

(iii) any one from:

• insulin present / produced

accept glucagon not produced

• (used in) respiration


allow exercise

• taken into cells

allow converted to glycogen

allow taken into liver (cells) / muscle (cells)

allow produce / make energy 1

[6]

M3. (a) (i) (wholemeal bread) any two from:

lower maximum / peak / less change 1

slower rise / change

ignore references to rate of fall or first to peak

need to take less insulin / less likely to hyper

no mark for identifying the type of bread but max 1 mark if not identified

1

(ii) any four from:

• amylase / carbohydrase

• starch to sugar

allow starch to glucose

• (sugar) absorbed / diffused / passes into blood

• correct reference to pancreas

allow once only as rise or fall

• insulin produced

• glucose (from blood) into cells / tissue / organ or named tissue / organ

allow glucose to glycogen

• glucose used in respiration / for energy

max 3 for explaining rise max 3 for explaining fall

4

(b) any three from:


advantages (compared to insulin injections):

• (may be) permanent / cure

• no / less need for self monitoring

• no / less need for insulin / injections

ignore reference to cost

• no / less need for dietary control

disadvantages (compared to insulin injections):

• low success rate

• (may) still need insulin / dietary control

• operation hazards

• risk of infection from donor

• rejection / need for drugs to prevent rejection

max 2 if only advantages or only disadvantages discussed can give converse if clear that it relates to insulin injections

3 [9]

M4.(a) A sensory (neurone)

ignore nerve 1

B motor (neurone)

ignore nerve 1

C spinal cord / central nervous system / white matter

accept grey matter 1

(b) by chemical / substance

allow transmitter 1


(c) muscle

allow extensor

ignore muscle names 1

[5]

M5

(a) (i) A – pituitary

allow hypothalamus 1

B – ovary / ovaries 1

(ii) in blood (stream)

accept in plasma

ignore dissolved 1

(b) (i) FSH and Luteinising Hormone (LH) 1

(ii) fertilised OR reference to sperm

1

form embryos / ball of cells or cell division 1

(embryo) inserted into mother’s womb / uterus

allow (fertilised egg) is inserted into mother’s womb / uterus 1


(iii) any one from:

• multiple births lead to low birth weight

• multiple births cause possible harm to mother / fetus / embryo / baby / miscarriages

allow premature

ignore reference to cost / ethics / population 1

(c) (i) any one from:

• almost identical

allow S (slightly) more successful

• both approximately 20% 1

(ii) larger numbers (in clinic R) (in 2007)

allow only 98 (in S) (compared to 1004 (in R)) 1

results likely to be more repeatable (in 2008)

allow more reliable

do not accept more reproducible / accurate / precise 1

[11]

revision pack topic 5 – homeostasis and response · 2020-03-17 · hormonal coordination in...

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