P2-Topic 5-Homeostasis Flashcards
(108 cards)
1
Q
what is homeostasis 2
A
the maintenance of a
constant internal environment
to maintain optimum conditions for enzyme and cellular function
2
Q
3 examples of condition ,maintained by homeostasis in the body
A
blood glucose concentration
body temperature
water levels
3
Q
what type of automatic control responses are used in the body 2
A
nervous
chemical
4
Q
what three things do all control systems have
A
receptors
coordination centers
effectors
5
Q
what is the function of a receptor?
A
cells that detect changes in the
environment (stimuli).
6
Q
What is the function of a coordination center? 2
A
(brain,spinal cord,pancreas)
receive and process information from receptors
7
Q
What is the function of an effector? 2
A
(muscles or glands)
bring about
responses to stimuli
8
Q
What is the function of the nervous system?
A
enables humans to react to their surroundings and to coordinate their behaviour
9
Q
How does a stimulus lead to a response being carried
out by the body? 4
A
Stimulus is converted into an electrical impulse by the receptors
electrical impulse passes along sensory neurones to the central nervous system (CNS).
CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the
effector, which carries out the response.
(muscles contracting, gland secreting hormones)
10
Q
What sequence of events describes how
the nervous system works 5
A
stimulus receptor coordinator effector response
11
Q
What is a reflex action? 2
A
automatic and rapid
response that does not involve any
conscious input from the brain
12
Q
Why are reflex actions important? 1
A
Reflex actions aid survival by preventing
harm to the body
13
Q
Describe how a reflex action occurs via a reflex arc
5
A
stimulus detected by a receptor
electrical impulse passes along a sensory neurone to the spinal cord (part in CNS).
At a synapse between a sensory neurone and a relay neurone, a
chemical diffuses across the gap and stimulates a new impulse which
passes along the relay neurone
same process happens at a synapse between a relay neurone and a
motor neurone.
the effector, carries out an appropriate response
14
Q
What is the difference between a reflex pathway and a
conscious pathway?
A
reflex pathway, the coordination centre
is a relay neurone found in the spinal
cord/unconscious parts of the brain.
conscious pathway, the coordination centre is in the conscious part of the brain
15
Q
examples of reflex arcs 2
A
pupils getting smaller to avoid damage from bright lights,
moving your hand from a hot surface to prevent damage.
16
Q
what are synapses and role 4
A
gaps between two neurons.
impulse reaches the end of the first neuron, a chemical is released into
the synapse.
chemical diffuses across the synapse.
When the chemical reaches the second neuron, it triggers the impulse to begin
again in the next neuron.
17
Q
where is the cerebral cortex? and function 4
A
emotions, language, memories and conscious thought.
folded(squishy) outer layer of the brain
18
Q
What is the function of the cerebellum?2
A
-back
controls muscular
coordination
19
Q
What is the function of the medulla? 3
A
at the top of the spinal cord.
unconscious things
heartbeat, breathing and swallowing.
20
Q
Why is the investigation and treatment of the brain difficult? 3
A
complex and delicate organ
easily damaged and destroyed
Drugs given to treat diseases cannot always reach the brain because of the membranes that surround it
The exact function of each part of the brain is not known
21
Q
What methods are used by scientists to determine
brain function?
A
Studying symptoms of patients with brain damage
Electrical stimulation of the brain
MRI scans
22
Q
What stimuli are the receptors of the eye sensitive to? 2
A
Light intensity
colour of light
23
Q
What are the two main functions of structures in the eye?
A
Focusing on near or distant objects -
accommodation.
Adaptation to dim light.
24
Q
Describe the structure and function of the
retina 2
A
receptors that are sensitive to light intensity and colour of light.
25
Describe the structure and function of the
| optic nerve 2
squiggle, vein bit at the bottom
carries impulses from receptors in the retina to the brain.
26
Describe the structure and function of
| the sclera 2
tough outer layer of the eye
supports and protects the eye.
27
Describe the structure and function of
| the cornea 2
transparent layer at the front of the eye.
| refract (bend) light rays as they enter the eye.
28
Describe the structure and function of
| the iris 1
controls the size of
the pupil by contracting or
relaxing.
allows the
eye to adjust to bright and
dim lighting
29
Describe the structure and function of the ciliary
| muscles and suspensory ligaments
control the shape of the lens to focus the light.
30
Describe how the iris alters the size of the pupil
| in both bright and dim light 3
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.
31
What is accommodation? 1
process of changing the shape of the lens to focus on near or distant objects.
32
How does the eye focus on a nearby object? 3
ciliary muscles contract
suspensory ligaments loosen
Lens becomes thicker and more curved -
light rays are refracted strongly.
33
How does the eye focus on a far away object? 3
Ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner - light rays are
refracted weakly
34
What is myopia and treated? ? 3
short-sightedness, lens is too curved, so distant objects appear blurry.
glasses with a concave lens,to spread out light rays to be focused on the retina
35
What is hyperopia and treated?
long-sightedness- lens is too flat, so it cannot refract light enough
glasses with a convex lense, brings the light rays together so they can be focused on the retina
36
What are the two types of contact lenses?
| 2
Hard - rigid material, last a long time, must be kept
sterile.
Soft - flexible material, last for a shorter time, more
comfortable.
37
What is laser eye surgery? 2
lasers can be used to reduce the thickness of the cornea (so it refracts light less) to treat myopia
change its curvature (so it
refracts light more strongly) to treat hyperopia
38
How can replacement lenses be used to
| treat visual defects 3
Hyperopia can be treated by replacing the lens with an artificial one made of clear plastic (or adding the plastic on top of the natural
lens).
risks: damage to retina or cataracts developing
39
What are the risks of lens replacement?
Risks of lens replacement include retinal
| damage, cataracts and infections
40
Where is body temperature controlled in the body?
controlled by the thermoregulatory centre in the hypothalamus
of the brain.
41
How is temperature monitored by the body?
| 2
Thermoregulatory centre has receptors that monitor the temperature of the blood
receptors in the skin that send impulses to the thermoregulatory centre
42
What physiological changes occur when the body
temperature is too high?
3
Vasodilation - blood vessels near the surface of the skin dilate - more heat is radiated away
Sweating - evaporation of water takes away heat energy from the surface of the skin.
43
What physiological changes occur when the
| body temperature is too low? 4
Vasoconstriction - blood vessels near the surface of the skin constrict - less heat radiated away.
Shivering - respiration allows muscles to contract.
exothermic process, so heat energy is released.
Sweating stops
44
What is the menstrual cycle?2
monthly cycle of physical changes in females
shedding of the uterus lining (menstruation) and ovulation
45
Describe the events of the menstrual cycle 3
-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 the egg is fertilised, pregnancy may occur. If not,
both the egg and the uterus lining are shed during
menstruation
46
What is ovulation?
release of a mature egg from
| the ovaries, approximately every 28 days
47
Name the four main hormones involved in the menstrual cycle
● Oestrogen
● Progesterone
● Follicle stimulating hormone (FSH)
● Luteinising hormone (LH)
48
What is the role of FSH in the menstrual cycle? 2
secreted by the pituitary gland
causes an egg to mature in an ovary.
49
What is the role of oestrogen in the
| menstrual cycle? 2
produced by the ovaries and released due to the action of FSH
causes the lining of the uterus to thicken
50
What is the role of LH in the menstrual cycle?2
produced in the pituitary gland as a
result of oestrogen
(ovulation) makes the ovary release the egg into the oviduct (fallopian tube)
51
What is the role of progesterone in the
| menstrual cycle? 2
produced by ovaries
maintains the lining of the uterus and keeps it intact.
52
what happens if the egg isn't fertilised
progesterone levels fall.
causing the uterus to shed its lining= period
menstrual cycle repeats roughly every 28 days.
53
what does oestrogen do during the menstrual cycle 3
stops the pituitary gland from releasing FSH so eggs don't mature.
causes the pituitary gland to release LH. causes ovulation.
Ovulation then causes the ovaries to release more progesteron
54
what does progesterone do during the menstrual cycle 2
maintains the lining of the uterus.
helps oestrogen to stop the production of more FSH and LH.
55
What are oral contraceptives and how it prevents pregnancy?2
contains oestrogen and/or progesterone
hormones
stop FSH production so that no eggs mature
56
What are other types (4) of hormonal contraception and hhow do they prevent pregancy
Injections, implants, skin patches and some intrauterine devices (IUDs
slowly release progesterone to prevent eggs maturing or being released
57
what are non-hormonal (barrier) methods and how do they prevent pregnancy
3
Condoms and diaphragms physically prevent sperm from reaching the egg.
Spermicides are chemicals that damage or kill sperm to prevent pregnancy.
Surgical sterilisation prevents pregnancy by cutting the sperm ducts in men or the oviducts in women
58
what are some disadvantages of some contraceptives 5
whether or not they protect against sexually transmitted infections (STIs
how reliable and effective the contraceptive is
forget about taking an oral contraceptive or putting on a condom, or you do it incorrectly, they won't work
Surgical sterilisation is irreversible
side effects.
catholic churches says unethical except natural methods
59
how are hormones used to increase the chance of fertility 2
fertility drugs contain FSH - which
stimulates oestrogen production and the
maturation of eggs in the ovary.
They also contain LH which triggers ovulation
60
What is IVF and the stages? 3
- Mother is given FSH and LH - stimulates maturation of eggs and ovulation.
- Eggs fertilised using sperm in a laboratory to develop into embryos.
● 1 or 2 embryos are inserted into the mother’s womb
61
What are the advantages of fertility treatment?
● Allows infertile couples to have children of their own
| ● Can store a woman’s eggs for later
62
What are the disadvantages of fertility treatment?
• it is very emotionally and physically stressful
• the success rates are not high
• it can lead to multiple births which are at risk to both the babies and the mother
-very expensive
63
Give the name of the body’s coordination
| system which involves hormones
The endocrine system
64
What is a hormone?3
chemical messenger
secreted by a gland.
travels in the blood to a target organ, to cause a response
65
What type of organ secretes hormones?
Glands
66
Why is the pituitary gland considered a
| ‘master gland’?2
-controls many other glands in the
body
-secretes a wide range of hormones,
some of which may stimulate other
endocrine glands
67
What is the role of the pituitary gland in the endocrine
| system?4
● 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.
68
What is the role of the thyroid gland in the
| endocrine system?
Secretes the hormone thyroxine - controls
metabolism, heart rate and body
temperature.
69
What is the role of the pancreas in the
| endocrine system?
Secretes the hormone insulin - controls
| blood glucose levels.
70
What is the role of the adrenal gland in the endocrine system?
Secretes adrenaline - controls the body’s
| ‘fight or flight’ response
71
What is the role of the testes aand ovaries in the endocrine system?
Secrete oestrogen, coordinates themenstrual cycle and the development of female secondary sexual characteristics.
Secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics.
72
Which organ monitors and controls blood glucose concentration?
The pancreas
73
explain how insulin controls blood glucose (sugar) levels in the body if it is too high.3
pancreas produces the hormone insulin
causes glucose to move from the blood into the cells.
In liver and muscle cells excess glucose is converted to glycogen for storage.by receptors on liver
74
How does the pancreas respond when blood glucose levels are too low 3
The pancreas secretes the hormone
glucagon.
Glucagon binds to liver cells,
causing glycogen to be converted into
glucose and released into the blood
75
How is blood glucose concentration controlled using a negative feedback loop? (higher only) 2
When 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.
76
What is Type 1 diabetes?
an autoimmune disorder
the pancreas does not produce sufficient
insulin to control the blood glucose concentration.
so blood glucose levels are often very
high, leading to excessive urination, tiredness and weight loss
77
How can Type 1 diabetes be treated?2
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.
78
What is Type 2 diabetes?2
the body cells no longer respond to insulin produced by the pancreas.
linked with increasing age and obesity
79
How can Type 2 diabetes be treated? 4
```
Following a carefully-controlled diet
● Doing regular exercise
● Losing weight
● Use of drugs which increase insulin
production and effectiveness
```
80
What is osmosis?
movement of water from a
dilute solution to a concentrated solution
through a partially permeable membrane
81
ways water is lost from the body?3
● During exhalation via the lungs
● Sweating
● Urine (some reabsorbed in the kidney)
82
In what ways are ions lost from the body?
| 2
Sweating
| ● Urine (some reabsorbed in the kidney)
83
How are excess amino acids excreted from the body?4
The liver converts excess amino acids into ammonia.
Excess amino acids are deaminated in the liver to form ammonia.
Ammonia is toxic, so converted into urea
Urea is excreted from the body via sweat and urine
84
How do the kidneys maintain the balance of water and other substances in the body? 2
● Filter blood in order to remove waste
products eg. urea.
● Selectively reabsorb useful molecules eg.glucose, water, ions.
85
What is the full name of the hormone ADH?
Anti-diuretic hormone
86
Where is ADH secreted in the body?
The pituitary gland of the brain
87
How does ADH affect the reabsorption of water in the kidneys?
● When the blood is too concentrated, the pituitary gland secretes more ADH.
● ADH travels in the bloodstream to the kidney and increases the permeability of kidney tubules to water.
● More water is reabsorbed in the kidneys so a smaller volume of more concentrated urine.
88
Why is kidney failure dangerous? (biology only) 3
kidneys may be 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.
89
What are the two main ways of treating kidney failure?
● Dialysis
| ● Transplant
90
What is kidney dialysis? 3
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 acroos a partially permeable membrane
91
Advantages and disadvantages of kidney dialysis 3
+no shortage of diialysis machines
- requires frequent treatments and a controlled diet
- expensive in the long run
92
Advantages and disadvantages of kidney transplants 4
+allow paitentss to live a normal life
+onlyexpensive initially
- shortage of kidney donars
- paitents have to take anti-rejection drugs for rest of life
93
What is negative feedback? 2
type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level.
94
What is thyroxine? 2
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
95
How is the release of thyroxine controlled by
| negative feedback? 4
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.
96
What is adrenaline?
hormone secreted by the adrenal gland in times of stress
responsible for the ‘fight or flight response’.
97
What are the effects of adrenaline?
● 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 away from digestive system to muscles
98
What is phototropism and gravitropism 30
p-growth in response to light
g- growth in response to gravity (geotrophism)
all done by shoot or root
99
What is a tropism?
A tropism is the response of a plant to a specific stimulus
100
What is auxin? 3
plant hormone
controls the growth of a plant’s shoots and roots
can increase or decrease the growth rates of roots and shoots.
101
How do plant shoots show positive phototropism? 4
.When a shoot grows, auxin builds up on the shaded side of the shoot.
● the shaded side grows faster
the shoot bends towards the light.
photosynthesis can occur at a faster rate
102
How do plant shoots show negative gravitropism?4
horizontal shoot, auxin gathers on the lower side due to gravity.
● Cells on the lower side of shoot grow more
shoot bends away from the direction of gravity.
● more light available for photosynthesis
103
How do plant roots show positive gravitropism?4
horizontal root, auxin builds up on the lower side
causing cells to grow less.
root bends in the direction of gravity
more water and nutrients are available to the plant roots
104
What are gibberellins?
Gibberellins are a type of plant hormone
| involved in seed germination.
105
What is ethene?
Ethene is a type of plant hormone
| involved in cell division and ripening.
106
What are the uses of auxins?3
● 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..
107
What are the uses of ethene?
to control ripening of fruit during
| storage and transport.
108
What are the uses of gibberellins?
● Termination of seed dormancy
● Promotion of flowering
● Increase of fruit size
