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[ gcse ] biology > B5: Homeostasis and response > Flashcards

B5: Homeostasis and response Flashcards

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1
Q

what is homeostasis?

A
  • the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme and cellular function.
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2
Q

Give 3 examples of conditions maintained by homeostasis in the body

A

• Blood glucose concentration
• Body temperature
• Water levels

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3
Q

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

A

Nervous and chemical

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4
Q

What three 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

Receptors detect changes in the environment (stimuli).

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6
Q

What is the function of an effector?

A

Effectors (muscles or glands) bring about responses to stimuli.

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7
Q

What is the function of a coordination centre?

A
  • obtain and process information from receptors.
  • Eg brain and spinal cord
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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 is converted into an electrical impulse by the receptors.
• The electrical impulse passes along sensory neurones to the central nervous system (CNS).
• The 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

Describe the sequence of events on the way the nervous system works

A

Stimulus— receptor— coordinator— effector—response

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11
Q

Define a ‘reflex action’

A
  • an automatic and rapid response
  • which does not involve any conscious input from the brain
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12
Q

Why are reflex actions important ?

A
  • Reflex actions aid survival by preventing harm to the body
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13
Q

Describe how a reflex action occurs via a reflex arc (4 marks)

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

Describe the knee jerk reflex (4)

A
  • receptor detects pain and sends electrical impulses along the sensory neurone
  • electrical impulses then move to the relay neurone in the spinal cord
  • the electrical impulses are then transmitted from relay neurone to the motor neurone
  • motor neurone sends impulses to the effector ( the muscle )
  • muscle contracts
  • so knee jerks away from pain
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15
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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16
Q

What is the function of the cerebral cortex. And where is it found

A
  • the outer layer of the brain which is divided into two hemispheres.
  • Is responsible for higher-order processes such as intelligence, memory, consciousness and personality
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17
Q

What is the function of the cerebellum and where is it found

A
  • this is underneath the cerebral cortex
  • is responsible for balance, muscle coordination and movement
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18
Q

What is the function of the medulla and where is it found ?

A

This region controls unconscious activities such as heart rate and breathing

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19
Q

Give 4 reasons why the investigation and treating of the brain difficult

A
  • the brain is a complex and delicate organ
  • the brain is easily damaged
  • certain membranes prevent drugs from reaching the brain
  • the exact function of each part of the brai is not known
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20
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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21
Q

delte

A

card pls

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22
Q

How can we study patients with brain damage?

A
  • observing the changes in an individual following damage on a certai area of the brain
  • this can provide information on the role this area has
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23
Q

How can we use electrical stimulation to map out the regions of the brain?

A
  • Tiny electrodes can be pushed into different parts of the brain
  • tiny jolts of electricity stimulate these regions and the mental or physical changes in the individual effects can be observed.
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24
Q

How can we use MRI scanning techniques?

A
  • to create an image of the brain.
  • it can be used to show which part of the brain is affected by a tumour, or which part is active during a specific task.
  • the scanners can detect changes in blood flow
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25
Q

evaluate the benefits and 2 risks of procedures carried out on the brain and nervous system

A

Risk:
- high level of risk due to the complexity of the brain
- If surgery is undergone more permanent damage or side-effects may be created, which could affect the patients’ quality of life.
Benefits
- improves quality of life and patient health
- treats disorders of some kind

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26
Q

What stimuli are the receptors of the eye sensitive to?

A

Light intensity and colour

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27
Q

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

A
  • accommodation ( focusing on near or distant objects)
  • adaptation to dim light
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28
Q

Describe the structure and function of the retina

A
  • the 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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29
Q

Describe the structure and the function of the optic nerve

A
  • the optic nerve connects the eye and the brain
  • it carries impulses to the brain so that an image can be visualised
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30
Q

Describe the structure and function of the sclera

A
  • the scelta is the tough white outer layer of the eye which protects its internal structures
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31
Q

Describe the structure and function of the cornea

A
  • the cornea is the curved transparent layer at the front of the eye
  • it lets light into the eye and refracts it
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32
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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33
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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34
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 - makes pupil smaller to avoid retinal damage
Dim light: circular muscles relax and radial muscles contract- makes pupil larger so more light can enter the eye

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35
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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36
Q

How does the eye focus on distant objects?

A

Ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner - light rays are refracted weakly

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37
Q

How can myopia be treated?

A

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

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38
Q

What is hyperopia?

A
  • long-sightedness
  • occurs when the lens of the eye is too flat or short. As a result , light is focused behind the retina so images appear out of focus.
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39
Q

How can hyperopia be treated?

A
  • treated using glasses with a convex lens , which brings the light rays together so they can be focused on the retina.
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40
Q

What are two 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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41
Q

What is laser eye surgery and how does it treat myopia and hyperopia

A
  • the use of lasers to fix visual defects in adults
  • to treat myopia, lasers reduce the thickness of the cornea so light is refracted less strongly.
  • to treat hyperopia, lasers alter the curvature of the cornea so light is refracted correctly
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42
Q

How can replacement lenses be used to treat visual defects?

A

A replacement lens can either be implanted into the eye along with the natural lens

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43
Q

Give three risks of lens replacement

A
  • retinal damage
  • cataracts
  • infections
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44
Q

Where is body temperature controlled in the body?

A
  • the thermoregulatory centre in the hypothalamus of the brain
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45
Q

How is temperature monitored by the body?

A
  • thermoregulatory centre has receptors sensitive to blood temperature
  • skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre
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46
Q

What physiological changes occur when the body temperature is too high.

A

Vasodilation- blood vessels near the surface of the skin dilate - more heat is radiated away as more blood flows closer to the surface of the skin
Sweating- sweat evaporates from skin surface resulting in increased heat energy transfer away from the body

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47
Q

What physiological changes occur when the body temperature is too low?

A

Vasoconstriction- blood vessels near the surface of the skin constrict so less heat is radiated away
Shivering- respiration allows muscles to contract as it is an exothermic reaction so heat energy is released
Sweating stops

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48
Q

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

A

The endocrine system

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49
Q

What is a hormone ?

A
  • A hormone is a chemical messenger secreted by a gland.
  • It travels in the blood to a target organ , where it causes a response
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50
Q

What type of organ secretes hormones?

A

Glands

51
Q

Which gland controls many other glands in the body?

A

The pituitary gland

52
Q

Why is the pituitary gland considered a ‘master gland’

A

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

53
Q

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

A
  • secretes human growth hormone. Controls 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
54
Q

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

A

Secretes the hormone thyroxine - controls basal metabolic rate , heart rate and body temperature

55
Q

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

A

controls blood glucose concentration

56
Q

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

A

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

57
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

58
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 male secondary sexual characteristics

59
Q

Which organ monitors and controls blood glucose concentration?

A

The pancreas

60
Q

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

A
  • The pancreas secretes the hormone insulin.
  • insulin binds to receptors on the liver and muscles , causing excess glucose to be converted into glycogen and stored
61
Q

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

A
  • The pancreas secretes the hormone glucagon.
  • Glucagon binds to liver cells, causing glycogen to be converted into glucose and released into the blood.
62
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.
63
Q

What is type 1 diabetes ?

A
  • an auto immune 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.
64
Q

Give three ways Type 1 diabetes can be treated.

A
  • insulin injections before meals - allows glucose to be converted into glycogen
  • limiting carbohydrate intake
  • using pancreas and pancreatic cell transplants
65
Q

What is type 2 diabetes?

A
  • a disorder in which the body’s cells stop responding to insulin , leading to an uncontrolled blood glucose concentration .
  • It’s onset is linked with increasing age and obesity
66
Q

Give 4 ways type 2 diabetes can be treated

A
  • following a carefully- controlled diet
  • doing regular exercise
  • losing weight
  • use of drugs which increase insulin production and effectiveness
67
Q

define osmosis

A

The movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane

68
Q

In what ways is water lost from the body?

A
  • During exhalation via the lungs
  • sweating
  • urine ( some reabsorbed in the kidney)
69
Q

In what ways are ions lost from the body

A
  • sweating
  • urine ( some reabsorbed in the kidney)
70
Q

How are excess amino acids excreted from the body?

A
  • excess amino acids are delaminated 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
71
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 via urea
  • selectively reabsorbed useful molecules eg glucose, water, ions
72
Q

What does the hormone ‘ ADH’ stand for

A

Anti-diuretic hormone

73
Q

Where is ADH secreted in the body?

A

The pituitary gland of the brain

74
Q

How does ADH affect the reabsorption of water in the kidneys

A
  • When the blood is too concentrated, the pituitary gland secretes more ADH
  • ADH travels in the bloodstream to the kidney making kidney tubule more permeable to water
  • more water is reabsorbed in the kidneys, resulting in a smaller volume of more concentrated urine.
75
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
- cell damage due to uncontrolled balance of ions

76
Q

Give the 2 main ways of treating kidney failure?

A
  • dialysis
  • transplant
77
Q

What is kidney dialysis?

A
  • use of a specialist machine to carry out the function of kidneys.
  • the persons blood flows through a partially permeable membrane surrounded by dialysis fluid
  • the fluid has the same concentration of dissolved ions and glucose as healthy blood
  • only waste substances eg urea will diffuse across barrier from blood
78
Q

What is the main male reproductive hormone and their function

A
  • testosterone
  • produces by the testes
  • which controls sperm production
79
Q

What is the main female reproductive hormone?

A
  • Oestrogen,
  • produced in the ovaries
80
Q

What is the menstrual cycle?

A
  • monthly cycle of physiological changes that occur in females , involving menstruation and ovulation
81
Q

Describe the events of the menstrual cycle

A
  • uterus lining thickens and eggs begin to mature in the ovaries
  • a egg is released from one of the ovaries( ovulation )
  • uterus lining remains thick
  • if egg is fertilised , pregnancy may occur .
  • If not both the egg and the uterus lining are shed during menstruation
82
Q

What is ovulation?

A
  • release of a mature egg from the ovaries, which occurs approximately every 28 days
83
Q

Name the 4 main hormones involved in the menstrual cycle

A
  • oestrogen
  • progesterone
  • follicle-stimulating hormone (FSH)
  • luteinizing hormone (LH)
84
Q

what is the role of FSH in the menstrual cycle?

A

.- controls the maturation of eggs within the ovaries ( inside a follicle )
- triggers the production of oestrogen in the ovaries

85
Q

what is the role of oestrogen in the menstrual cycle?

A
  • produced by the ovaries and released due to the action of FSH
  • it causes the regrowth and repair of the uterus lining
  • it triggers the production of LH and restricts the release of more FSH
86
Q

what is the role of LH in the menstrual cycle

A
  • LH is produced in the pituitary gland as a result of oestrogen. it triggers ovulation
87
Q

what is the role of progesterone in the menstrual cycle?

A
  • it is secreted from the follicle of the ovary. it sustains the uterus lining and inhibits FSH and LH
88
Q

What is contraception?

A

contraception refers to any method of preventing pregnancy

89
Q

what are the two types of oral contraceptives ? And a pro and con

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

adv:
- highly effective if taken correctly
disadvantage:
- must be taken every day and side effects

90
Q

Give four ways 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
91
Q

what is the contraceptive patch and an adv and disadv

A
  • contains progesterone
  • it is a patch that is placed onto the skin for 7 days at a time
    adv
    : more convenient then taking a pill
    con :
  • lasts only 7 days
92
Q

what is the contraceptive implant?

A
  • a small rod inserted under the skin which continuously releases the hormone progesterone
  • lasts for 3 years

adv :
- more convenient
- lasts for a long period of time
disadv:
- side effects such as blood clots

93
Q

what is the contraceptive injection?

A

an injection containing the hormone progesterone - lasts for approximately 3 months

94
Q

what is the IUS?

A
  • intrauterine system
  • a small plastic device that is inserted into the uterus .
  • it releases progesterone which thickens cervical mucus and prevents uterine lining from thickening
95
Q

what is the IUD?

A
  • a small copper-containing device inserted into the uterus which prevents the implantation of embryos
96
Q

what is a spermicide and give a disadvantage ?

A
  • a chemical that kills or immobilises sperm cells - however they are not effective and work better when combined with barrier methods.
97
Q

Define a barrier method of contraception?

A
  • a physical separation between the sperm and the egg
98
Q

Give and describe a barrier method of contraception

A

condoms: thin sheath worn on the penis or the inside of the vagina - protects against STIs but may tear/break
diaphragms: a thin cap placed over the cervix - prevent entry of sperm

99
Q

what surgical methods of contraception are available ?

A

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

100
Q

define abstinence

A
  • practice of not having sex which also avoids pregnancy
  • some people abstain from sex around the time of ovulation - this is known as the rhythm method, but is quite unreliable
101
Q

how do fertility drugs increase the chance of pregnancy?

A
  • many contain FSH which stimulates oestrogen production and the maturation of eggs in the ovary
  • they also contain LH which triggers ovulation
102
Q

What is IVF?

A
  • in vitro fertilisation is a type of fertility treatment
  • mother is given FSH and LH stimulates maturation of eggs and ovulation
  • eggs are fertilised using sperm in a laboratory where they develop into embryos
  • 1 or 2 embryos are inserted into a mother’s womb
103
Q

give 2 advantages of fertility treatment?

A
  • allows infertile couples to have children
  • can store a woman’s egg for later
104
Q

give 4 disadvantages of fertility treatment

A
  • it can be a very expensive process
  • it has a low success rate - especially for older couples
  • increases chance of multiple pregnancies - dangerous for mother and babies
  • side effects of fertility drugs
105
Q

what is negative feedback?

A
  • a type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level
106
Q

how is this 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
107
Q

define adrenaline

A

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

108
Q

give 5 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
  • blood diverted away from digestive system to muscles
  • increased mental awareness
109
Q

what is a tropism

A
  • the response of a plant to a specific stimulus
110
Q

what is a phototropism?

A
  • the response of a plant’s shoot or root to light
111
Q

what is gravitropism?

A
  • the response of a plant’s shoot or root to gravity
112
Q

what is auxin?

A
  • 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
113
Q

how do plants 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
114
Q

how do plants shoots show negative gravitropism

A
  • in a horizontal shoot, auxin accumulates in the lower side due to gravity
  • cells on the lower side of shoot grow more , causing the shoot to bend away from direction of gravity
  • as a result, more light is usually available for photosynthesis
115
Q

how do plant roots show positive gravitropism

A
  • in a horizontal root, auxin accumulates in the lower side, causing cells to grow less
  • the root bends in the direction of gravity
  • as a result, more water and nutrients are available to the plant roots.
116
Q

what are gibberellins?

A
  • a type of plant hormone involved in seed germination
117
Q

what is ethene?

A
  • a type of plant hormone involved in cell division and ripening of fruit
118
Q

what are the three 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
119
Q

what are the uses of ethene?

A
  • control of food ripening in the food industry
  • allows fruit to be ripened just before they are sold
120
Q

give three uses of giberellins?

A
  • termination of seed dormancy
  • promotion of flowering
  • increase of fruit size
121
Q

what is a kidney transplant ?

A
  • the diseased kidney is replaced with a healthy kidney from a donor
122
Q

Compare the use of dialysis and kidney transplant

A

dialysis :
- no shortage of dialysis machines
- requires frequent treatments and controlled diets
- expensive in long term
transplant
- shortage of kidney donors
- allows patient to lead normal life
- only expensive initially
- have to take anti rejection drugs

123
Q

compare how auxin works in roots and shoots

A

roots:
auxin inhibits cell growth
shoots:
auxin stimulates cell growth

[ gcse ] biology (10 decks)

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