Homeostasis & Response Flashcards
(117 cards)
1
Q
What is homeostasis?
A
maintenance of a constant internal environment in order to maintain optimum conditions for enzyme function
2
Q
Give examples of conditions maintained by homeostasis in the body
A
- body temperature
- blood glucose concentration
- water levels
3
Q
What 2 types of responses are used in body control systems?
A
nervous & chemical
4
Q
What 3 components do all control systems have?
A
- receptors
- coordination centres
- effectors
5
Q
What is the function of a receptor?
A
detect changes in the environment
6
Q
What is the function of a coordination centre?
A
obtain and process information
7
Q
What is the function of an effector?
A
effectors (muscles or glands) bring about responses to stimuli
8
Q
What is the function of the nervous system?
A
allows the body to react to its surroundings and coordinate an appropriate response
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
10
Q
What sequence of events describes how the nervous system works?
A
stimulus –> receptor –> coordinator –> effector –> response
11
Q
What is a reflex action?
A
automatic and rapid response which doesn’t involve any conscious input from the brain
12
Q
Why are reflex actions important?
A
aid survival by preventing harm to the body
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
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
15
Q
What is the function of the cerebral cortex?
A
controls consciousness, intelligence, memory and language
16
Q
What is the function of the cerebellum?
A
controls muscular coordination
17
Q
What is the function of the medulla?
A
controls unconscious activities (like breathing, heart rate)
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
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
20
Q
What stimuli are the receptors of the eye sensitive to?
A
light intensity, colour
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
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
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
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
25
Describe the structure and function of the cornea
- 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
26
Describe the structure and function of the iris
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
27
Describe the structure and function of the ciliary muscles and suspensory ligaments
the ciliary muscles and suspensory ligaments hold the lens in place and control its shape
28
Describe how the iris alters the size of the pupil in both bright and dim light
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
29
What is accommodation?
alteration of the lens' shape in order to focus on near or distant objects
30
How does the eye focus on a nearby object?
- ciliary muscles contract
- suspensory ligaments loosen
- lens becomes thicker and more curved - light rays are refracted strongly
31
How does the eye focus on a far away object?
- ciliary muscles relax
- suspensory ligaments tighten
- lens becomes thinner - light rays are refracted weakly
32
What is myopia?
short-sightedness; lens f the eye is too curved, so light is focused in front of the retina, making images appear blurry
33
How can myopia be treated?
glasses with a concave lens, which spreads out light rays so they can be focused on the retina
34
What is hyperopia?
long-sightedness; lens of the eye is too flat, light focuses behind the retina so images appear out of focus
35
How can hyperopia be treated?
glasses with a convex lens, bringing the light rays together so they can be focuses on the retina
36
What are the 2 types of contact lenses?
- 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?
How is it used to treat myopia and hyperopia?
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
38
How can replacement lenses be used to treat visual defects?
replacement lens can be implanted into eye (along with natural lens) or could replace the natural lens altogether.
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?
thermoregulatory centre in the hypothalamus of the brain
41
How is temperature monitored by the body?
- thermoreg. centre has receptors sensitive to blood temperature
- skin has receptors sensitive to skin temperature - sends impulses to thermoreg. centre
42
What physiological changes occur when body temp is too high?
- 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
43
What physiological changes occur when body temp is too low?
- 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
44
Give the name of the body's coordination system which involves hormones
endocrine system
45
What is a hormone?
chemical messenger secreted by a gland, travels in the blood to a target organ, where it causes a response
46
What type of organ secretes hormones?
glands
47
Which gland controls many other glands in the body?
pituitary gland
48
Why is the pituitary gland considered a 'master gland'?
secretes a wide range of hormones, some of which may stimulate other endocrine glands
49
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
50
What is the role of the thyroid gland in the endocrine system?
secrets the hormone thyroxine - controls metabolism, heart rate and body temperature
51
What is the role of the pancreas in the endocrine system?
secretes the hormone insulin - controls blood glucose levels
52
What is the role of the adrenal gland in the endocrine system?
secretes adrenaline - controls the body's 'fight or flight' response
53
What is the role of the ovaries in the endocrine system?
secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics
54
What is the role of the testes in the endocrine system?
secrete testosterone, which coordinates the production of sperm and the development of secondary sexual characteristics
55
Which organ monitors and controls blood glucose concentration
pancreas
56
How does the pancreas respond when blood glucose levels are too high?
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
How is blood glucose concentration controlled using a negative feedback loop?
- 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
What is type 1 diabetes?
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
How can type 1 diabetes be treated?
- 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
What is type 2 diabetes?
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
How can type 2 diabetes be treated?
- following a carefully-controlled diet
- doing regular exercise
- losing weight
- use of drugs which increase insulin production and effectiveness
62
What is osmosis?
movement if water from a dilute solution to a concentrated solution through a partially permeable membrane
63
In what ways is water lost from the body?
- during exhalation via the lungs
- sweating
- urine (some reabsorbed in the kindey)
64
In what ways are ions lost from the body?
- sweating
- urine (some reabsorbed in the kidney)
65
How are excess amino acids excreted from the body?
- 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
How do the kidneys maintain the balance of water and other substances in the body?
- filter blood in order to remove waste products (e.g. urea)
- selectively reabsorb useful molecules (e.g. glucose, water, ions)
67
What is the full name of the hormone ADH?
anti-diuretic hormone
68
Where is ADH secreted in the body?
pituitary gland of the brain
69
How does ADH affect the reabsorption of water in the kidneys?
- 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
Why is kidney failure dangerous?
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
What are the two main ways of treating kidney failure?
- dialysis
- transplant
72
What is kidney dialysis?
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
What is the function of reproductive hormones during puberty?
males: cause the development of secondary sexual characteristics
females: cause the development of secondary sexual characteristics and the maturation of eggs
74
What is the main male reproductive hormone?
testosterone, produced by the testes and controls sperm production
75
What is the main female reproductive hormone?
oestrogen, produced by the ovaries and is involved in the menstrual cycle
76
What is the menstrual cycle?
monthly cycle of physiological changes that occur in females, involving the shedding of the uterus lining (menstruation) and ovulation
77
Describe the events of the menstrual cycle
- 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
What is ovulation?
release of a mature egg from the ovaries, which occurs approximately every 28 days
79
Name the 4 main hormones involved in the menstrual cycle
- oestrogen
- FSH (follicle stimulating hormone)
- progesterone
- LH (lutenising hormone)
80
What is the role of FSH in the menstrual cycle?
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
What is the role of oestrogen in the menstrual cycle?
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
What is the role of LH in the menstrual cycle?
LH is produced in the pituitary gland as a result of oestrogen, its release triggers ovulation
83
What is the role of progesterone in the menstrual cycle?
secreted from the follicle of the ovary, it sustains the uterus lining and inhibits FSH and LH
84
What is contracepton?
any method of preventing pregnancy
85
What are the 2 types of oral contraceptives?
- combined contraceptive pill (contains oestrogen and progesterone)
- mini pill (contains only progesterone)
86
How does the contraceptive pill prevent pregnancy?
- 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
What is the contraceptive patch?
- contains both oestrogen and progesterone
- patch is placed onto the skin for 7 days at a time
88
What is the contraceptive implant?
a small rod inserted uder the skin which continuously releases the hormone progesterone - lasts for 3 years
89
What is the contraceptive injection?
injection containing the hormone progesterone - lasts for approximately 3 months
90
What is the IUS?
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
What is the IUD?
intrauterine device - small copper-containing device inserted into the uterus, which prevents the implantation of embryos
92
What is a spermicide?
chemical that kills or immobilises sperm cells - however, they are not very effective, and work better when combined with barrier methods
93
What is a barrier method of contraception?
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
What surgical methods of contraception are available?
sterilisation - in males, sperm ducts are tied (vasectomy) and in females, the oviducts are tied
95
What is abstinence?
practice of not having sex, which also avoids pregnancy
some people abstain from sex around the time of sex (rhythm method), quite unreliable
96
How do fertility drugs increase the chance of pregnancy?
many fertility drugs contain FSH - stimulates estrogen production and the maturation of eggs in the ovary, also contain LH - triggers ovulation
97
What is IVF?
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
What are the advantages of fertility treatment?
- allows infertile couples to have children
- can store a woman's eggs for later
99
What are the disadvantages of fertility treatment?
- 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
What is negative feedback?
type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level
101
What is thyroxine?
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
How is the release of thyroxine controlled by negative feedback?
- 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
What is adrenaline?
hormone secreted by the adrenal gland in times of stress, is responsible for the 'fight or flight' response
104
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 way from digestive system to muscles
105
What is a tropism?
response of a plant to a specific stimulus
106
What is phototropism?
response of a plant's root or shoot to light
107
What is gravitropism?
response of a plant's shoot or root to gravity
108
What is auxin?
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
How do plant shoots show positive phototropism?
- 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
How do plant shoots show negative gravitropism?
- 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
How do plant shoots show positive gravitropism?
- 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
What are gibberellins?
type of plant hormone involved in seed germination
113
What is ethene?
type of plant hormone involved in cell division and ripening
114
What are the uses of auxins?
- 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
What is tissue culture?
the use of auxin to promote growth of roots and shoots
116
What are the uses of ethene?
control food ripening in the food industry - allows fruit to be ripened just before they are sold
117
What are the uses of gibberellins?
- termination of seed dormancy
- promotion of flowering
- increase of fruit size
