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Biology > Homeostasis & Response > Flashcards

Homeostasis & Response Flashcards

1
Q

What is homeostasis?

A

maintenance of a constant internal environment in order to maintain optimum conditions for enzyme function

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2
Q

Give examples of conditions maintained by homeostasis in the body

A
  • body temperature
  • blood glucose concentration
  • water levels
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3
Q

What 2 types of responses are used in body control systems?

A

nervous & chemical

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4
Q

What 3 components do all control systems have?

A
  • receptors
  • coordination centres
  • effectors
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5
Q

What is the function of a receptor?

A

detect changes in the environment

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6
Q

What is the function of a coordination centre?

A

obtain and process information

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7
Q

What is the function of an effector?

A

effectors (muscles or glands) bring about responses to stimuli

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8
Q

What is the function of the nervous system?

A

allows the body to react to its surroundings and coordinate an appropriate response

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9
Q

How does a stimulus lead to a response being carried out by the body?

A
  • stimulus converted to electrical impulse by receptors
  • electrical impulse passes along sensory neurones to CNS
  • CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response
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10
Q

What sequence of events describes how the nervous system works?

A

stimulus –> receptor –> coordinator –> effector –> response

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11
Q

What is a reflex action?

A

automatic and rapid response which doesn’t involve any conscious input from the brain

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12
Q

Why are reflex actions important?

A

aid survival by preventing harm to the body

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13
Q

Describe how a reflex action occurs via a reflex arc

A
  • stimuli detected by a receptor
  • electrical impulse passes along a sensory neurone to the spinal cord (CNS)
  • at a synapse betw. a sensory and relay neurones, a chemical diffuses across the gap ad stimulates a new impulse which passes along the relay neurone
  • same process occurs at a synapse between a relay and motor neurone
  • at effector, an appropriate response s carried out
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14
Q

What is the difference between a reflex pathway and a conscious pathway?

A

within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain
in a conscious pathway, the coordination centre is in the conscious part of the brain

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15
Q

What is the function of the cerebral cortex?

A

controls consciousness, intelligence, memory and language

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16
Q

What is the function of the cerebellum?

A

controls muscular coordination

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17
Q

What is the function of the medulla?

A

controls unconscious activities (like breathing, heart rate)

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18
Q

Why is investigation and treatment of the brain difficult?

A
  • brain is a complex and delicate organ
  • brain is easily damaged and destroyed
  • certain membranes prevent drugs from reaching the brain
  • the exact function of each part of the brain is not known
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19
Q

What methods are used by scientists to determine brain function?

A
  • studying patients with brain damage
  • electrical stimulation of the brain
  • MRI scans
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20
Q

What stimuli are the receptors of the eye sensitive to?

A

light intensity, colour

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21
Q

What are the 2 main functions of structures found within the eye?

A
  • focusing on near or distant objects - accommodation
  • adaptation to dim light
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22
Q

Describe the structure and function of the retina

A
  • retina is a light-sensitive layer found at the back of the eye
  • light stimulates the retinal cells, resulting in impulses being sent to the brain
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23
Q

Describe the structure and function of the optic nerve

A
  • optic nerve connects the eye and brain
  • carries impulses to the brain so an image can be visualised
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24
Q

Describe the structure and function of the sclera

A

the sclera is the tough outer layer of the eye which protects its internal structures

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25
Q

Describe the structure and function of the cornea

A
  • the cornea is the curved transparent layer at the front of the eye
  • lets the light into the eye and allows light to be focused onto the retina
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26
Q

Describe the structure and function of the iris

A

the iris is a muscle which controls the size of the pupil by contracting or relaxing, this allows the eye to adjust to bright and dim lighting

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27
Q

Describe the structure and function of the ciliary muscles and suspensory ligaments

A

the ciliary muscles and suspensory ligaments hold the lens in place and control its shape

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28
Q

Describe how the iris alters the size of the pupil in both bright and dim light

A

bright light - circular muscles contract and radial muscles relax, making pupil smaller to avoid retinal damage
dim light - circular muscles relax and radial muscles contract, making pupil larger so more light can enter the eye

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29
Q

What is accommodation?

A

alteration of the lens’ shape in order to focus on near or distant objects

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30
Q

How does the eye focus on a nearby object?

A
  • ciliary muscles contract
  • suspensory ligaments loosen
  • lens becomes thicker and more curved - light rays are refracted strongly
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31
Q

How does the eye focus on a far away object?

A
  • ciliary muscles relax
  • suspensory ligaments tighten
  • lens becomes thinner - light rays are refracted weakly
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32
Q

What is myopia?

A

short-sightedness; lens f the eye is too curved, so light is focused in front of the retina, making images appear blurry

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33
Q

How can myopia be treated?

A

glasses with a concave lens, which spreads out light rays so they can be focused on the retina

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34
Q

What is hyperopia?

A

long-sightedness; lens of the eye is too flat, light focuses behind the retina so images appear out of focus

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35
Q

How can hyperopia be treated?

A

glasses with a convex lens, bringing the light rays together so they can be focuses on the retina

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36
Q

What are the 2 types of contact lenses?

A
  • hard; rigid material, last a long time, must be kept sterile
  • soft; flexible material, last for a shorter time, more comfortable
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37
Q

What is laser eye surgery?
How is it used to treat myopia and hyperopia?

A

use of lasers to fix visual defects in adults
to treat myopia:
- lasers reduce thickness of cornea so light is refracted less strongly
to treat hyperopia:
- lasers alter curvature of the cornea so light is refracted correctly

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38
Q

How can replacement lenses be used to treat visual defects?

A

replacement lens can be implanted into eye (along with natural lens) or could replace the natural lens altogether.

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39
Q

What are the risks of lens replacement?

A

risks of lens replacement include retinal damage, cataracts and infections

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40
Q

Where is body temperature controlled in the body?

A

thermoregulatory centre in the hypothalamus of the brain

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41
Q

How is temperature monitored by the body?

A
  • thermoreg. centre has receptors sensitive to blood temperature
  • skin has receptors sensitive to skin temperature - sends impulses to thermoreg. centre
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42
Q

What physiological changes occur when body temp is too high?

A
  • vasodilation; blood vessels near the surface of the skin dilate, more heat is radiated away
  • sweating; evaporation of water rakes away heat energy from surface of the skin
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43
Q

What physiological changes occur when body temp is too low?

A
  • vasoconstriction; blood vessels near the surface of the skin constrict, less heat radiated away
  • shivering; respiration allows muscles to contract. is an endothermic process, so heat energy is released
  • sweating stops
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44
Q

Give the name of the body’s coordination system which involves hormones

A

endocrine system

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45
Q

What is a hormone?

A

chemical messenger secreted by a gland, travels in the blood to a target organ, where it causes a response

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46
Q

What type of organ secretes hormones?

A

glands

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47
Q

Which gland controls many other glands in the body?

A

pituitary gland

48
Q

Why is the pituitary gland considered a ‘master gland’?

A

secretes a wide range of hormones, some of which may stimulate other endocrine glands

49
Q

What is the role of the pituitary gland in the endocrine system? (4)

A
  • secretes human growth hormone - controls human growth
  • stimulates the thyroid gland
  • stimulates ovulation and the production of oestrogen in the ovaries
  • stimulates the production of sperm and testosterone in the testes
50
Q

What is the role of the thyroid gland in the endocrine system?

A

secrets the hormone thyroxine - controls metabolism, heart rate and body temperature

51
Q

What is the role of the pancreas in the endocrine system?

A

secretes the hormone insulin - controls blood glucose levels

52
Q

What is the role of the adrenal gland in the endocrine system?

A

secretes adrenaline - controls the body’s ‘fight or flight’ response

53
Q

What is the role of the ovaries in the endocrine system?

A

secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics

54
Q

What is the role of the testes in the endocrine system?

A

secrete testosterone, which coordinates the production of sperm and the development of secondary sexual characteristics

55
Q

Which organ monitors and controls blood glucose concentration

A

pancreas

56
Q

How does the pancreas respond when blood glucose levels are too high?

A

pancreas secretes the hormone insulin, insulin binds to receptors on the liver and muscles, causing excess glucose to be converted into glycogen and stored

57
Q

How is blood glucose concentration controlled using a negative feedback loop?

A
  • when the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas
  • the action of either hormone (insulin or glucagon) helps bring back the concentration to the correct level
58
Q

What is type 1 diabetes?

A

autoimmune disorder in which the pancreas does not produce sufficient insulin to control the blood glucose concentration. as a result, blood glucose levels are often very high, leading to excessive urination, tiredness and weight loss

59
Q

How can type 1 diabetes be treated?

A
  • insulin injections before meals - allows glucose to be converted into glycogen
  • limiting carbohydrate intake
  • attempts using pancreas and pancreatic cell transplants; investigations into genetic engineering of pancreatic cells
60
Q

What is type 2 diabetes?

A

disorder in which the body’s cells stop responding to insulin, leading to an uncontrolled blood glucose concentration. its onset is linked with increasing age and obesity

61
Q

How can type 2 diabetes be treated?

A
  • following a carefully-controlled diet
  • doing regular exercise
  • losing weight
  • use of drugs which increase insulin production and effectiveness
62
Q

What is osmosis?

A

movement if water from a dilute solution to a concentrated solution through a partially permeable membrane

63
Q

In what ways is water lost from the body?

A
  • during exhalation via the lungs
  • sweating
  • urine (some reabsorbed in the kindey)
64
Q

In what ways are ions lost from the body?

A
  • sweating
  • urine (some reabsorbed in the kidney)
65
Q

How are excess amino acids excreted from the body?

A
  • excess amino acids are deaminated in the liver to form ammonia
  • ammonia is toxic, therefore it is converted into urea
  • urea is excreted from the body via sweat and urine
66
Q

How do the kidneys maintain the balance of water and other substances in the body?

A
  • filter blood in order to remove waste products (e.g. urea)
  • selectively reabsorb useful molecules (e.g. glucose, water, ions)
67
Q

What is the full name of the hormone ADH?

A

anti-diuretic hormone

68
Q

Where is ADH secreted in the body?

A

pituitary gland of the brain

69
Q

How does ADH affect the reabsorption of water in the kidneys?

A
  • when blood is too concentrated, the pituitary gland secretes more ADH
  • ADH travels in the bloodstream to the kidney and increases the permeablity of kidney tubles to water
  • more water is reabsorbed in the kidneys, resulting in a smaller volume of more concentrated urine
70
Q

Why is kidney failure dangerous?

A

unable to filter the blood properly, leading to:
- a build-up of toxic molecules (eg. urea) in the body
- an uncontrolled ion and water balance and cells being damaged as a result of osmosis

71
Q

What are the two main ways of treating kidney failure?

A
  • dialysis
  • transplant
72
Q

What is kidney dialysis?

A

use of a specialist machine to carry out the function of kidneys. dialysis fluid contains the same concentration of glucose and ions as healthy blood. as a result, only excess and waste molecules are lost from the blood, and glucose and ions remain

73
Q

What is the function of reproductive hormones during puberty?

A

males: cause the development of secondary sexual characteristics
females: cause the development of secondary sexual characteristics and the maturation of eggs

74
Q

What is the main male reproductive hormone?

A

testosterone, produced by the testes and controls sperm production

75
Q

What is the main female reproductive hormone?

A

oestrogen, produced by the ovaries and is involved in the menstrual cycle

76
Q

What is the menstrual cycle?

A

monthly cycle of physiological changes that occur in females, involving the shedding of the uterus lining (menstruation) and ovulation

77
Q

Describe the events of the menstrual cycle

A
  • uterus lining thickens and eggs begin to mature in the ovaries
  • an egg is released from one of the ovaries (ovulation) - uterus lining remains thick
  • if egg is fertilised, pregancy may occur. if not, both egg and uterus lining are shed during menstruation
78
Q

What is ovulation?

A

release of a mature egg from the ovaries, which occurs approximately every 28 days

79
Q

Name the 4 main hormones involved in the menstrual cycle

A
  • oestrogen
  • FSH (follicle stimulating hormone)
  • progesterone
  • LH (lutenising hormone)
80
Q

What is the role of FSH in the menstrual cycle?

A

secreted by the pituitary gland. it controls the maturation of eggs within the ovaries (inside a follicle) and triggers the production of oestrogen by the ovaries

81
Q

What is the role of oestrogen in the menstrual cycle?

A

produced by the ovaries and release due to the action of FSH - it causes the regrowth of the uterus lining
it triggers the production of LH and restricts the release of more FSH

82
Q

What is the role of LH in the menstrual cycle?

A

LH is produced in the pituitary gland as a result of oestrogen, its release triggers ovulation

83
Q

What is the role of progesterone in the menstrual cycle?

A

secreted from the follicle of the ovary, it sustains the uterus lining and inhibits FSH and LH

84
Q

What is contracepton?

A

any method of preventing pregnancy

85
Q

What are the 2 types of oral contraceptives?

A
  • combined contraceptive pill (contains oestrogen and progesterone)
  • mini pill (contains only progesterone)
86
Q

How does the contraceptive pill prevent pregnancy?

A
  • inhibits FSH - eggs do not mature
  • prevents the development of the uterus lining - eggs cannot implant
  • increases the thickness of cervical mucus - immobilises sperm cells
87
Q

What is the contraceptive patch?

A
  • contains both oestrogen and progesterone
  • patch is placed onto the skin for 7 days at a time
88
Q

What is the contraceptive implant?

A

a small rod inserted uder the skin which continuously releases the hormone progesterone - lasts for 3 years

89
Q

What is the contraceptive injection?

A

injection containing the hormone progesterone - lasts for approximately 3 months

90
Q

What is the IUS?

A

intrauterine system - small plastic devce inserted into the uterus, releases progesterone which thickens cervical mucus and prevents the build-up of the uterine lining

91
Q

What is the IUD?

A

intrauterine device - small copper-containing device inserted into the uterus, which prevents the implantation of embryos

92
Q

What is a spermicide?

A

chemical that kills or immobilises sperm cells - however, they are not very effective, and work better when combined with barrier methods

93
Q

What is a barrier method of contraception?

A

physical separation between sperm and egg
- condoms - thin sheath worn on the penis or inside the vagina - protects against STIs but may tear/break
- diaphragms - thin cap placed over the cervix - prevents entry of sperm

94
Q

What surgical methods of contraception are available?

A

sterilisation - in males, sperm ducts are tied (vasectomy) and in females, the oviducts are tied

95
Q

What is abstinence?

A

practice of not having sex, which also avoids pregnancy
some people abstain from sex around the time of sex (rhythm method), quite unreliable

96
Q

How do fertility drugs increase the chance of pregnancy?

A

many fertility drugs contain FSH - stimulates estrogen production and the maturation of eggs in the ovary, also contain LH - triggers ovulation

97
Q

What is IVF?

A

in vitro fertilisation is a type of ferility treatement
- mother is given FSH and LH - stimulates maturation of eggs and ovulation
- eggs are fetilised using sperm in a laboratory - develop into embryos
- 1/2 embryos are inserted into the mother’s womb

98
Q

What are the advantages of fertility treatment?

A
  • allows infertile couples to have children
  • can store a woman’s eggs for later
99
Q

What are the disadvantages of fertility treatment?

A
  • can be a very expensive process
  • has a low success rate - especially for older couples
  • increases chance of multiple pregnancies - dangerous for mother and babies
  • side effects of fertility drugs
100
Q

What is negative feedback?

A

type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level

101
Q

What is thyroxine?

A

a hormone released by the thyroid gland, its release is triggered by the thyroid stimulating hormone (TSH), thyroxine controls the body’s metabolic rate, growth and development

102
Q

How is the release of thyroxine controlled by negative feedback?

A
  • levels of blood thyroxine falls - detected by receptors in the brain
  • pituitary gland releases more TSH
  • more thyroxine produced and released by the thyroid gland
  • blood thyroxine level returns to normal
103
Q

What is adrenaline?

A

hormone secreted by the adrenal gland in times of stress, is responsible for the ‘fight or flight’ response

104
Q

What are the effects of adrenaline?

A
  • increase in heart and breathing rate - delivers oxygen and glucose to the body
  • stored glycogen converted to glucose
  • dilation of pupils
  • increased mental awareness
  • blood diverted way from digestive system to muscles
105
Q

What is a tropism?

A

response of a plant to a specific stimulus

106
Q

What is phototropism?

A

response of a plant’s root or shoot to light

107
Q

What is gravitropism?

A

response of a plant’s shoot or root to gravity

108
Q

What is auxin?

A

hormone which controls the growth of a plant’s shoots and roots, when auxin is unevenly distributed in a growing plant, the rate of growth will also be unequal

109
Q

How do plant shoots show positive phototropism?

A
  • one side of the shoot is in the light, causing auxin to move to the shaded side
  • at the shaded side, the cells are stimulated to grow - the shoot bends towards the light
  • as a result, photosynthesis can occur at a faster rate
110
Q

How do plant shoots show negative gravitropism?

A
  • in a horizontal shoot, auxin accumulates in the lower side due to gravity
  • cells on the lower side of a shoot grow more, causing the shoot to bend away from the direction of gravity
  • as a result, more light is usually available for photosynthesis
111
Q

How do plant shoots show positive gravitropism?

A
  • in a horizontal root, auxin accumulates in the lower side, causing cells to grow less
  • root bends in the direction of gravity
  • as a result, more water and nutrients are available to the plant roots
112
Q

What are gibberellins?

A

type of plant hormone involved in seed germination

113
Q

What is ethene?

A

type of plant hormone involved in cell division and ripening

114
Q

What are the uses of auxins?

A
  • weedkillers - auxin causes cells to grow at a rapid rate, causing plant death
  • rooting powder - auxin causes new plant to grow very quickly
  • tissue culture - auxin promotes growth of roots and shoots
115
Q

What is tissue culture?

A

the use of auxin to promote growth of roots and shoots

116
Q

What are the uses of ethene?

A

control food ripening in the food industry - allows fruit to be ripened just before they are sold

117
Q

What are the uses of gibberellins?

A
  • termination of seed dormancy
  • promotion of flowering
  • increase of fruit size

Biology (7 decks)

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