Integration Of Body Systems

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Integration in Living Organisms

Complex organisms have body systems made of component parts that work together for the whole organism.
Cell-cell communication is required within and between systems in organisms with billions of cells.
Hormones are produced in the endocrine system but can affect other systems, e.g. the reproductive system.
Multicellular organisms show a hierarchy of organisation: cells → tissues → organs → organ systems.
Tissues are groups of specialised cells working together, e.g. epithelial tissue absorbs food in the small intestine.
Organs are made of different tissues, e.g. the heart contains cardiac muscle, blood vessel and connective tissues.
Emergent properties mean the whole organism is greater than the sum of its parts, e.g. a cheetah becomes an effective predator through integration of all body systems.

The central and peripheral nervous systems

The Nervous System

The nervous system consists of the central nervous system (CNS) – brain and spinal cord – and the peripheral nervous system (PNS) – all other nerves.
Information travels as electrical impulses along neurones; a bundle of neurones is a nerve.
The brain is made of billions of interconnected neurones and controls complex conscious and unconscious behaviours.
Cerebral cortex: outer folded layer responsible for intelligence, memory, consciousness and personality.
Cerebellum: coordinates balance, muscle coordination and movement.
Brainstem: relays messages; the medulla controls unconscious activities such as heart rate and breathing.
Pituitary gland produces hormones including FSH and LH; hypothalamus regulates body temperature and controls the pituitary gland.

Diagram of the human nervous system showing the brain, spinal cord and nerves.

The Spinal Cord and Reflex Arc

The spinal cord is part of the CNS and acts as an integration centre for unconscious processes.
White matter contains mainly axons carrying information to and from the brain; grey matter contains neurones and synapses for reflex responses.
A reflex arc is a pathway from receptor to effector without involving conscious brain regions.
In a pain reflex arc, a nocireceptor detects a stimulus (e.g. sharp pin or hot flame).
An impulse travels along a sensory neurone to the spinal cord, synapses with a relay neurone, then a motor neurone carries the impulse to an effector muscle.
The muscle contracts and pulls the hand away; awareness of the reflex occurs after it has been carried out.
Other reflexes include blinking, coughing, pupil reflex and knee reflex, which aid survival.

A reflex arc

Motor Neurones and Muscle Contraction

Motor neurones carry action potentials to muscles, terminating at neuromuscular junctions.
At the neuromuscular junction, an action potential causes calcium ions to enter the neurone, stimulating release of acetylcholine (ACh).
ACh binds to receptors on the sarcolemma, opening ion channels and allowing sodium ions to diffuse in, depolarising the membrane.
The action potential travels down T-tubules, triggering release of calcium ions from the sarcoplasmic reticulum.
Calcium ions bind to troponin, moving tropomyosin and exposing myosin-binding sites on actin.
This initiates the sliding filament model of muscle contraction.

Melatonin and Circadian Rhythms

Circadian rhythms are daily cycles in physiology and behaviour, e.g. sleep, body temperature and hormone secretion.
Melatonin is secreted by the pineal gland in the brain.
Melatonin secretion increases in the evening in response to darkness and decreases at dawn in response to light.
Light is detected by the retina, and signals are transmitted to the pineal gland.
Increasing melatonin levels cause tiredness and promote sleep; decreasing levels prepare the body for waking.
Melatonin contributes to the night-time drop in core body temperature and decreases urine production at night.
Melatonin is still released in constant darkness on a roughly 24-hour cycle, showing light resets the rhythm daily.

Epinephrine and the Fight or Flight Response

Epinephrine (adrenaline) is secreted by the adrenal medulla when stimulated by the sympathetic nervous system during stress, fear or excitement.
It prepares the body for the 'fight or flight' response, causing increased heart rate, dry mouth and sweating.
Epinephrine binds to receptors on the SAN, increasing the frequency of excitations and thus heart rate.
This supplies more blood, oxygen and glucose to muscle cells, increasing aerobic respiration and energy release.
Epinephrine also stimulates the cardiovascular control centre in the medulla oblongata, further speeding up heart rate.
Blood vessels to less important organs (digestive system, skin) constrict, diverting blood to organs involved in fight or flight.
Blood flow to the brain remains constant regardless of stress or relaxation.

The major endocrine glands

Control Mechanisms: Heart Rate and Ventilation

The medulla contains the cardioregulatory centre, with an acceleratory centre and an inhibitory centre connected to the SAN by autonomic nerves.
Acceleratory centre sends impulses via sympathetic neurones; norepinephrine at the SAN increases heart rate.
Inhibitory centre sends impulses via parasympathetic neurones; acetylcholine at the SAN decreases heart rate.
Chemoreceptors detect changes in blood pH, oxygen and carbon dioxide levels; baroreceptors monitor blood pressure.
These receptors are in the aorta and carotid arteries; higher frequency impulses activate the acceleratory centre, lower frequency activate the inhibitory centre.
Ventilation rate is controlled by respiratory centres in the medulla.
Carbon dioxide combines with water to form carbonic acid, which dissociates into H+ and HCO3−, lowering blood pH.
Chemoreceptors in the medulla detect H+ and send more action potentials to diaphragm and intercostal muscles, increasing ventilation – an example of negative feedback.

Control of Peristalsis

Peristalsis is a series of muscle contractions in the walls of the oesophagus or small intestine that push food along.
It is controlled unconsciously by the enteric nervous system (ENS), a web of sensory, relay and motor neurones in the alimentary canal.
The bolus is detected by stretch receptors as the canal distends.
Relay neurones synapse with two motor neurones: one releases excitatory neurotransmitter causing longitudinal muscles to contract behind the bolus.
Circular muscles contract to reduce lumen diameter, preventing food moving backwards.
A second motor neurone releases inhibitory neurotransmitter, causing smooth muscle ahead of the bolus to relax and open the lumen.

Plant Tropisms and Auxin

Tropisms are growth responses to external stimuli such as light, gravity, water and objects.
Positive tropisms are towards a stimulus; negative tropisms are away from a stimulus.
Phototropism: stems grow towards light (positive phototropism) to maximise photosynthesis.
Gravitropism (geotropism): stems grow away from gravity (negative gravitropism); roots grow towards gravity (positive gravitropism).
Auxins are plant hormones that regulate tropisms.
In shoots, auxin stimulates cell elongation; in roots, auxin inhibits cell elongation (slows growth).
Efflux pumps coded by PIN3 genes carry auxins from cell to cell, maintaining an uneven distribution of auxin.
Tropic responses can be studied qualitatively (diagrams) or quantitatively (angle of curvature).

Auxin and phototropism

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1.Which row of the table gives the most accurate summary of the actions of auxins?
Easy
- AIn shoots: cells elongate; In roots: growth inhibited
- BIn shoots: cells grow in number; In roots: growth inhibited
- CIn shoots: cells elongate; In roots: growth promoted
- DIn shoots: cells grow in number; In roots: growth promoted
2.Which row of the table correctly describes examples of unconscious and conscious processes?
Medium
- AConscious control: Detecting taste on the tongue; Unconscious control: Detecting information on balance
- BConscious control: Detecting temperature changes of the skin; Unconscious control: Sensing sound vibrations in the inner ear
- CConscious control: Detecting the water content of the blood; Unconscious control: Sensing pressure changes of the blood
- DConscious control: Sensing sound vibrations in the inner ear; Unconscious control: Detecting taste on the tongue
3.Which statement best describes the action of peristalsis in the alimentary canal?
Medium
- AStriated muscles contract to move the partially digested food in a wave-like movement along the alimentary canal.
- BCircular muscles contract behind the partially digested food and the longitudinal muscles shorten.
- CSkeletal muscle contractions force the food through the alimentary canal with valves preventing backflow.
- DLongitudinal muscles contract behind the partially digested food and the circular muscles shorten.
4.Which statement accurately describes the raising of heart rate by the cardioregulatory centre of the brain?
Medium
- ALow blood pressure, high blood oxygen concentration, and high blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.
- BLow blood pressure, low blood oxygen concentration, and low blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.
- CHigh blood pressure, high blood oxygen concentration, and high blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.
- DHigh blood pressure, low blood oxygen concentration, and low blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.
5.A person is admitted to hospital after suffering a stroke. It was found that the suprachiasmatic nucleus in the hypothalamus of the brain was damaged by the event. This resulted in the pineal gland secreting less melatonin into the bloodstream. Which of the following changes would be observed in the patient?
Medium
- AIncreased thirst and more frequent urination.
- BDisrupted sleep patterns and increased irritability.
- CConstantly feeling cold and weight gain.
- DFatigue and forgetfulness.
6.What would not be considered a function of auxins?
Medium
- AStimulates cell elongation in shoots, leading to an increase in plant height
- BStimulates the development of axillary buds further away from the shoot apical meristem
- CInhibits the development of axillary buds close to the shoot apical meristem
- DInhibits cell elongation in root cells, therefore slowing down root growth
7.Which of the following statements about melatonin are correct? I. Melatonin secretion increases in the evening in response to darkness and decreases at dawn in response to light. II. Increasing melatonin levels stimulate the body, preparing it for waking up and staying awake during the day. III. Melatonin is secreted by the hypothalamus. IV. The night-time drop in core body temperature triggers an increase in melatonin secretion. V. Melatonin levels vary during a 12-hour cycle known as a circadian rhythm.
Hard
- AII, IV and V
- BI, III and IV
- CI only
- DII and V
8.Which of A - D gives the most accurate description of how efflux pumps contribute to plant tropisms?
Hard
- AEfflux pumps pump low-density particles to the top of a horizontal root in order to initiate a positive gravitropism.
- BLight denatures PIN3 proteins which leads to fewer efflux pumps, and hence less cell elongation, on the sunny side of a plant shoot.
- CEfflux pumps are coded for by PIN3 genes and carry auxins from one cell to another in order to maintain an uneven distribution of auxins.
- DEfflux pumps carry auxins away from growing tissues on the removal of a stimulus, in order to maintain an even distribution of auxins.

Soal lainnya

9.Match each region or gland of the brain with its main function.
Medium
- Cerebral cortex
- Cerebellum
- Medulla
- Hypothalamus
- Pituitary gland
- Controls unconscious activities such as heart rate and breathing
- Responsible for higher-order processes such as intelligence, memory and personality
- Produces many hormones including FSH and LH
- Regulates body temperature and produces hormones that control the pituitary gland
- Responsible for balance, muscle coordination and movement
10.Which of the following are correct statements about melatonin? (select all that apply)
Hard
- AMelatonin secretion increases in the evening in response to darkness and decreases at dawn in response to light.
- BMelatonin is secreted by the pineal gland.
- CIncreasing melatonin levels stimulate the body, preparing it for waking up and staying awake during the day.
- DMelatonin is secreted by the hypothalamus.
- EIncreasing melatonin levels lead to feelings of tiredness and promote sleep.
11.Place the events of a pain reflex arc in the correct sequence, starting from the stimulus.
Medium
- A nocireceptor in the skin detects the stimulus
- An afferent (sensory) action potential travels along a sensory neurone to the CNS
- The impulse is passed to a relay neurone in the grey matter of the spinal cord
- The relay neurone synapses with a motor neurone
- A motor neurone carries an impulse to an effector muscle in the hand and the muscle contracts
12.Which of the following correctly describes the pathway by which epinephrine increases heart rate?
Medium
- AEpinephrine binds to receptors on the sinoatrial node (SAN), increasing the frequency of excitations and so raising heart rate.
- BEpinephrine binds to receptors on the medulla, which directly generates the heartbeat.
- CEpinephrine binds to receptors on the atrioventricular node (AVN), which slows the heart rate.
- DEpinephrine binds to receptors on the vagus nerve, which increases the heart rate.
13.Which of the following changes occur in the body during the 'fight or flight' response to epinephrine? (select all that apply)
Medium
- AIncreased heart rate
- BIncreased sweating
- CConstriction of blood vessels to the digestive system and skin
- DIncreased blood flow to the brain
- EDilation of blood vessels to the digestive system
14.The spinal cord is an integration centre for unconscious processes.
Easy
True or false?
15.Which statement best describes how the medulla decreases heart rate?
Medium
- AThe inhibitory centre sends impulses along parasympathetic neurones and acetylcholine is secreted at the synapse with the SAN, reducing the frequency of electrical waves.
- BThe acceleratory centre sends impulses along sympathetic neurones and norepinephrine is secreted at the synapse with the SAN, reducing the frequency of electrical waves.
- CThe inhibitory centre sends impulses along sympathetic neurones and norepinephrine is secreted at the synapse with the SAN, reducing the frequency of electrical waves.
- DThe inhibitory centre sends impulses along parasympathetic neurones and norepinephrine is secreted at the synapse with the SAN, reducing the frequency of electrical waves.
16.Which of the following are functions of the hypothalamus? (select all that apply)
Medium
- ARegulating body temperature
- BOsmoregulation by releasing ADH when blood becomes too concentrated
- CRegulating digestive activity and appetite
- DControlling endocrine functions by causing the pituitary gland to release hormones
- EInitiating voluntary muscle contractions for movement
17.A student grows a seedling in a dark box with a single small hole on one side. After three days the shoot is seen bending towards the hole. Which statement best explains this observation?
Medium
- AAuxin accumulates on the shaded side of the shoot and stimulates greater cell elongation there
- BAuxin accumulates on the lit side of the shoot and stimulates greater cell elongation there
- CAuxin is destroyed by light on the shaded side, so cells there elongate less
- DAuxin moves towards the light and inhibits cell elongation on the lit side
18.A plant is placed on its side in the dark. After several days the shoot is seen growing upwards and the root downwards. Which row correctly identifies the tropic responses shown?
Medium
- AShoot: negative gravitropism; Root: positive gravitropism
- BShoot: positive gravitropism; Root: negative gravitropism
- CShoot: positive phototropism; Root: negative phototropism
- DShoot: negative phototropism; Root: positive gravitropism
19.Which of the following statements about the control of heart rate are correct? (select all that apply)
Hard
- AThe acceleratory centre sends impulses along sympathetic neurones to the SAN
- BNorepinephrine is secreted at the synapse with the SAN to increase heart rate
- CThe inhibitory centre sends impulses along sympathetic neurones to the SAN
- DAcetylcholine is secreted at the synapse with the SAN to decrease heart rate
- EBaroreceptors detect changes in blood pH
20.The medulla oblongata contains both an acceleratory centre and an inhibitory centre that control heart rate.
Easy
True or false?
21.Match each brain region with its main function.
Medium
- Cerebral cortex
- Cerebellum
- Medulla
- Higher-order processes such as intelligence and memory
- Balance, muscle coordination and movement
- Unconscious activities such as heart rate and breathing
22.Place the events of the pain reflex arc in the correct sequence, starting with the stimulus.
Medium
- Pain stimulus detected by nocireceptor in the skin
- Sensory neurone transmits impulse to the spinal cord
- Relay neurone in the grey matter synapses with a motor neurone
- Motor neurone carries impulse to the effector muscle
- Muscle contracts and pulls the hand away
23.A student grows five seedlings in a dark box with a single small hole on one side. After three days, the shoots bend towards the hole. Which statement best explains this result?
Medium
- AAuxin is destroyed by light on the illuminated side, so cells on that side stop elongating and the shoot bends towards the light.
- BAuxin accumulates on the shaded side, causing greater cell elongation there and bending the shoot towards the light.
- CAuxin accumulates on the illuminated side, causing greater cell elongation there and bending the shoot away from the light.
- DAuxin is produced in the shoot tip and moves equally to all sides, so the shoot grows straight up towards the hole.
24.A student wants to investigate gravitropism in seedlings. Which of the following are appropriate experimental methods? (select all that apply)
Medium
- APlace seedling radicles in different positions (facing up, facing down, facing horizontally).
- BMeasure the angle of curvature of the seedlings after a set period.
- CCover the shoot tip with a light-proof cap and observe the direction of growth.
- DAdd a strong acid to the soil to stimulate root growth.
- ERecord qualitative diagrams of seedling growth.
25.Quantitative results from tropism experiments must be processed using mathematical skills before analysis.
Easy
True or false?
26.Match each type of measurement with its correct description.
Medium
- Qualitative measurement
- Quantitative measurement
- Angle of curvature
- Colour change
- Recorded as words or descriptions
- Recorded as numerical data
- A quantitative measurement of tropism
- A qualitative observation
27.Place the steps of an experiment to investigate phototropism in the correct sequence.
Medium
- Grow seedlings in a dark box with a single hole on one side.
- Observe the direction of shoot growth after several days.
- Record whether the shoots bend towards or away from the hole.
- Measure the angle of curvature of each shoot.
28.Which statement best explains the bending of the shoots?
Medium
- AAuxin is produced in the shoot tip and moves away from light, causing greater elongation on the shaded side.
- BAuxin is produced in the shoot tip and moves towards light, causing greater elongation on the illuminated side.
- CLight destroys auxin on the shaded side, causing cells there to elongate more.
- DAuxin is evenly distributed, so the shoot grows straight towards the hole.
29.In an experiment, a student removes the tip of a shoot and places it in a dark box with a single hole on one side. After several days, the shoot does not bend towards the light. What is the best explanation for this result?
Hard
- AThe shoot tip is the site of auxin production, so without it auxin cannot accumulate on the shaded side.
- BThe shoot tip is the site of light detection, so without it the plant cannot sense light direction.
- CRemoving the tip stops all cell elongation, so the shoot cannot grow at all.
- DThe shoot tip produces a hormone that inhibits growth, so removing it prevents bending.
30.Which of the following would be expected if a seedling is placed horizontally in the dark? (select all that apply)
Hard
- AThe shoot grows upwards, away from gravity.
- BThe root grows downwards, towards gravity.
- CThe shoot grows downwards, towards gravity.
- DThe root grows upwards, away from gravity.
- EThe shoot shows positive gravitropism.
31.In an experiment investigating gravitropism, using a clinostat (rotating the seedling) would eliminate the effect of gravity and allow the study of other tropisms.
Medium
True or false?
32.Which row of the table correctly identifies the type of tropism shown by a plant shoot and a plant root in response to gravity?
Medium
- AShoot: positive gravitropism; Root: negative gravitropism
- BShoot: negative gravitropism; Root: positive gravitropism
- CShoot: positive phototropism; Root: negative phototropism
- DShoot: negative phototropism; Root: positive phototropism
33.Which statement best defines a reflex arc?
Medium
- AA pathway that carries impulses from a receptor to an effector without involving conscious regions of the brain.
- BA pathway that carries impulses from a receptor to the brain for conscious processing before a response.
- CA pathway that carries hormones from an endocrine gland to a target organ via the blood.
- DA pathway that carries impulses from the brain to a muscle to initiate voluntary movement.
34.Which of the following is the correct definition of a hormone?
Medium
- AA chemical messenger produced by an endocrine gland and carried by the blood.
- BAn electrical signal that passes along a neurone.
- CA protein that speeds up a chemical reaction.
- DA chemical that is released into a synapse to carry a nerve impulse.
35.Which row of the table correctly matches each brain region with its function?
Medium
- ACerebellum: balance and muscle coordination; Medulla: unconscious activities such as heart rate and breathing
- BCerebellum: intelligence and memory; Medulla: balance and muscle coordination
- CCerebrum: unconscious activities such as heart rate and breathing; Hypothalamus: balance and muscle coordination
- DMedulla: intelligence and memory; Cerebellum: regulation of body temperature
36.Which of the following statements about the nervous system are correct? (select all that apply)
Medium
- AThe central nervous system consists of the brain and spinal cord.
- BThe peripheral nervous system consists of all the nerves in the body.
- CInformation is sent through the nervous system in the form of electrical impulses.
- DA nerve is a single neurone.
- EThe spinal cord cannot process information independently from the brain.
37.Melatonin is secreted by the pituitary gland.
Easy
True or false?
38.Peristalsis in the alimentary canal is controlled by striated muscles.
Easy
True or false?
39.The cerebellum initiates voluntary movement.
Medium
True or false?
40.Match each type of receptor with the stimulus it detects.
Medium
- Photoreceptors
- Chemoreceptors in taste buds
- Thermoreceptors
- Mechanoreceptors in the inner ear
- Osmoreceptors
- Light
- Chemicals in food and drink
- Temperature changes
- Sound vibrations
- Water content of the blood
41.Identify the gland that secretes thyroxin.
Easy
42.Complete the sentence about the transport of carbon dioxide in the blood.
Easy
Around 85% of carbon dioxide is transported in the blood plasma in the form of ____ ions, while around 10% is bound to haemoglobin as ____.
43.A person's breathing rate increased by 38.5% to 18 breaths per minute. Calculate the breathing rate before the increase. Give your answer to the nearest whole number.
Medium
44.Calculate the percentage increase in melatonin concentration between 2 pm and 12 am.
Medium
45.Identify one physiological change that would occur between 2 pm and 3 am in the body of an individual with the melatonin levels shown.
Medium
46.A person's heart rate increased by 25% to 100 beats per minute during exercise. Calculate the heart rate before the increase. Give your answer as a whole number.
Medium
47.During exercise, a person's ventilation rate increased by 50% to 24 breaths per minute. Calculate the ventilation rate before the increase. Give your answer as a whole number.
Medium
48.Complete the sentence about the control of peristalsis.
Medium
Peristalsis is controlled by the ____ nervous system, specifically the enteric nervous system.
49.Name the region of the brain that regulates body temperature and controls the pituitary gland.
Medium
50.Complete the sentence about how hormones reach their target cells.
Easy
Hormones are chemical substances produced by an endocrine gland and carried by the ____, and they only affect cells that have complementary ____ that the hormone can bind to.
51.A person's ventilation rate increased by 38.5% to 18 breaths per minute. Calculate the ventilation rate before the increase. Give your answer to the nearest whole number.
Medium
52.Complete the sentence about how carbon dioxide is transported in the blood.
Medium
Around 85% of carbon dioxide is transported in the blood plasma in the form of ____ ions, while about 10% is bound to haemoglobin as ____.
53.Outline the part played by thyroxin in regulating body temperature.
Medium
54.Outline how peristalsis ensures one-way movement of food through the alimentary canal.
Hard
55.Outline the role of auxin in the shoot response to light.
Hard
56.Explain how epinephrine increases heart rate during the 'fight or flight' response.
Hard
57.Describe the response the tip of a shoot would show if it received light from one side only.
Medium
58.A person's breathing rate increased by 38.5% to 18 breaths per minute. Calculate the breathing rate before the increase. Give your answer to the nearest whole number.
Medium
- A13 breaths per minute
- B15 breaths per minute
- C12 breaths per minute
- D14 breaths per minute
59.Calculate the percentage increase in melatonin concentration between 2 pm and 12 am.
Medium
- A300 %
- B250 %
- C275 %
- D225 %
60.A person's heart rate increased by 25% to 100 beats per minute during exercise. Calculate the heart rate before the increase. Give your answer as a whole number.
Medium
- A88 beats per minute
- B72 beats per minute
- C96 beats per minute
- D80 beats per minute
61.During exercise, a person's ventilation rate increased by 50% to 24 breaths per minute. Calculate the ventilation rate before the increase. Give your answer as a whole number.
Medium
- A15 breaths per minute
- B16 breaths per minute
- C18 breaths per minute
- D17 breaths per minute
62.A person's ventilation rate increased by 38.5% to 18 breaths per minute. Calculate the ventilation rate before the increase. Give your answer to the nearest whole number.
Medium
- A15 breaths per minute
- B12 breaths per minute
- C14 breaths per minute
- D13 breaths per minute

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