topic 5 - homeostasis & response Flashcards
1
Q
what is homeostasis?
A
the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
2
Q
what conditions are maintained by homeostasis in the body?
A
- blood glucose concentration
- body temperature
- water levels
3
Q
what two types of responses are used in body control systems?
A
- nervous responses
- chemical responses
4
Q
what do all automatic control systems include?
A
- receptor cells - these detect stimuli
- coordination centres - these receive and process information from receptors
- effectors, muscles or glands, which bring about responses which restore optimum levels
5
Q
what is stimulus?
A
change in environment
6
Q
what are three examples of coordination centres in the human body?
A
- brain
- spinal cord
- pancreas
7
Q
what is the function of the nervous system?
A
the nervous system enables humans to react to their surroundings and coordinate their behaviour
8
Q
how does a stimulus lead to a response being carried out by the body?
A
- receptors detect a stimulus and send electrical impulses down neurones to the central nervous system
- the central nervous system (co-ordination centre) now sends electrical impulses down other neurones to effectors and the effectors bring about a response
9
Q
what are effectors?
A
- effectors are usually a muscle which contracts
- or a gland which secretes a hormone
10
Q
what are effectors?
A
- effectors are usually a muscle which contracts
- or a gland which secretes a hormone
11
Q
what are reflex actions?
A
reflex actions are automatic and rapid reactions; they do not involve the conscious part of the brain
12
Q
why are reflex actions important?
A
reflex actions aid survival by preventing harm to the body
13
Q
how does a reflex action occur via a reflex arc
A
- a receptor detects the stimulus
- an electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
- at the end of the sensory neurone, there is a junction called the synapse.
- at the synapse, a chemical is released.
- this chemical now diffuses across to a relay neurone in the CNS where it triggers an electrical impulse
- the electrical impulse now passes across the relay neurone and reaches another synapse
- once again a chemical is released
- this chemical triggers an electrical impulse in a motor neurone
- the electrical impulse now passes down the motor neurone to an effector
14
Q
how can we investigate the effect of a factor on human reaction time?
A
- person 1 sits on a stool with a good upright posture
- person 1 then places the forearm of their dominant arm across the table
- now person 2 holds a ruler vertically - the 0cm mark should be between person 1’s thumb and first finger
- person 2 then tells person 1 to prepare to catch the ruler
- person 2 now drops the ruler at a random time
- person 1 has to catch the ruler with their thumb and first finger as quickly as possible when it drops
- person 2 now records the measurement on the ruler that is level with the top of person 1’s thumb
- the test is then repeated several times and a mean is calculated
- from these experiments, we convert results to a reaction time which can be done using a conversion table
- at the end the people switch places
15
Q
what is the independent variable of required practical 7?
A
- the person having their reaction time tested
16
Q
what is the dependent variable of required practical 7?
A
- the reaction time
17
Q
what are the control variables of required practical 7?
A
- the starting distance between the thumb and the first finger should be kept constant
- the ruler at the top of the thumb should always be measured
- the conditions of the room should be kept the same, eg. lighting and level of background noise
18
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
19
Q
what is the brain?
A
a protected organ inside the skull that form different regions
20
Q
what is the function of the cerebral cortex?
A
controls consciousness, intelligence, memory + language
21
Q
what is the function of the cerebellum?
A
- controls muscular activity, balance and movement
22
Q
what is the spinal cord?
A
- a long, thin structure made up of nervous tissue, connected to the medulla
23
Q
what is the function of the medulla?
A
- controls unconscious activities e.g. heartbeat, movement of the gut, breathing
24
Q
what is the function of the pituitary gland?
A
- produces hormones and receives electrical impulses from the brain via the hypothalamus
25
what is the function of the hypothalamus?
- regulates body temperature and releases hormones
26
how do scientists find out the functions of different parts of the brain?
- studying patients with brain damage
- electrically stimulating parts of the brain using MRI
27
why is the investigation and treatment of the brain difficult?
- the brain is a complex and delicate organ
- the 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
28
what is created to produce an image using MRI?
a magnetic field
29
what is an advantage of using MRI to investigate the brain?
creates a detailed and a clear scan of the brain
30
what is the disadvantage of using MRI to investigate the brain?
noisy/little space
31
what is inserted into the brain to electrically stimulate it?
electrodes
32
how can scientists use electrical stimulation to determine the function of the brain?
- they can stimulate different parts of the brain and what effect this has
33
what is the definition of the eye?
a sense organ containing receptors sensitive to light intensity and colour
34
what is the function of the ciliary muscle/suspensory ligament?
to hold the lens in position and change its length
35
how is the iris adapted for its function?
contracts and relaxes to control size of the pupil - in dim light the pupil gets bigger to allow as much light as possible into the eye
36
how is the cornea adapted for its function?
refracts light - bends as light enters
37
how is the lens adapted for its function?
focuses the light rays as the light passes through
38
how is the retina adapted for its function?
- contains the light sensitive cells, where the light is focused
39
how is the sclera adapted for its function?
- tough white outer layer of the eye, to prevent damage
- has a transparent area at the front to allow light through the lens
40
how is the optic nerve adapted for its function?
- the optic nerve contains sensory neurons that carry electrical impulses in the brain
41
how does the brain receive information about the eye recieving light?
- retina is sensitive to light as it contains light receptor cells that are sensitive to light
- the impulse cells passes along the optic nerve which pass along the optic neuron
42
what is the iris reflex?
depending on the intensity of surrounding light, the iris makes an adjustment to ensure that the retina receives the correct amount of light
43
what happens to the eye in dim light?
- circular muscles relax
- radial muscles contract
- pupils dilate
- increasing amount of light entering
44
what happens to the eye in bright light?
- circular muscles contract
- radial muscles relax
- pupils constricts
- reduces amount of light entering
45
what is accommodation?
the ability of focusing on near or distant objects by changing the shape of the lens in the eye
46
how does the eye focus on near objects?
- the ciliary muscles contract
- loosening the suspensory ligaments
- which thickens and curves the lens
- light rays are strongly refracted onto the retina
47
how does the eye focus on far objects?
- the ciliary muscles relax
- pulling the suspensory ligaments tightly
- the lens is then pulled thin
- and only slightly refracts light rays.
48
what is myopia?
- myopia (short-sightedness) usually occurs when the lens of the eye is too curved
- as a result, light is focused in front of the retina so images appear blurry
49
how can myopia be treated?
- this can be corrected using a concave lens so light focuses correctly on the lens
50
what is hyperopia?
- hyperopia (long-sightedness) usualy occurs when the lens of the eye is too flat/thin or if the eyeball is too short
- as a result, light is focused behind the retina so images appear out of focus
51
how can hyperopia be treated?
- can be treated wearing thicker glasses with a convex lens
- this refocuses the rays onto the retina
52
what are treatments for vision defects?
- contact lenses
- laser eye surgery
- replacement lens surgery
53
what are the two 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
54
what is laser eye surgery?
- 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 that the light is refracted correctly
55
what is the normal human body temperature?
37°C
56
what monitors and controls body temperature?
- the brain
57
where is our body temperature regulated?
thermoregulatory centre
58
what is negative feedback?
- the temperature of the body is kept constant due to a negative feedback system
- when the level of something in the body is too high/low, we use a negative feedback mechanism to counteract the change
59
what are responses that reduce the body temperature?
- sweat produced by sweat glands
- vasolidation
60
how does the body react to maintain its core temperature after a race?
- temperature receptors in the skin send impulses to the thermoregulatory centre
- thermoregulatory centre in the brain sends impulses to lower the body temperature
- more sweat produced from the sweat glands which cools skin's surface by evaporation
- blood vessels leading to capillaries dilate
- more blood flows nearer the surface of the skin
- so more energy is transferred to the surroundings by radiation
61
what are responses that increase body temperatures?
- no sweat produced
- shivering - muscles contract
- vasoconstriction
62
how does shivering increase body temperature?
- muscles contract
- this requires respiration
- respiration releases energy as heat which increases body temperature
63
how does vasoconstriction increase body temperature?
- blood vessels supplying the skin narrow/constrict
- less blood flow to surface of skin
- less heat lost by radiation
64
what is the name of the body's coordination system which involves hormones?
the endocrine system
65
what is the endocrine system?
- the endocrine system is composed of glands which secrete hormones directly into the bloodstream
- the blood carries the hormone to a target organ which produces an effect
66
what is the difference between the endocrine system and the nervous system?
- the nervous system uses electrical impulses which travel down neurones
- however the endocrine system uses hormones which are chemicals and are carried in the bloodstream
- whereas signalling in the nervous system is extremely fast, the endocrine tends to produce a much slow effect
67
what type of organ secretes hormones?
glands
68
what is the function of the pancreas?
- the pancreas releases hormones
- these are involved in controlling the concentration of glucose in the blood
69
what is the function of the ovaries and testes?
- the ovaries and testes release hormones involved in puberty and in reproduction
70
what is the function of the thyroid gland?
- the thyroid gland produces hormones which are involved in growth and in regulating the body's basal metabolic rate
71
what is the function of the adrenal glands?
- the adrenal glands release the hormone adrenaline which is produced in times of fear or stress
72
what is the function of the adrenal glands?
- the adrenal glands release the hormone adrenaline which is produced in times of fear or stress
73
where are the pituitary glands located?
- the pituitary gland is located in the brain
74
which gland controls many other glands in the body?
the pituitary gland
75
why is the pituitary gland considered a "master gland'?
- the pituitary gland secretes a wide range of hormones, some of which may stimulate other endocrine glands
76
what is blood glucose concentration monitored and controlled by?
the pancreas
77
what happens if the blood glucose concentration is too high?
- the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells.
- in liver and muscle cells excess glucose is converted to glycogen for storage
- because excess glucose is being stored, the concentration of glucose in the blood returns to its normal level
78
why is glucose needed by every cell?
- to release energy by respiration
79
what happens when the blood glucose concentration is too low?
- the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood
80
what is diabetes?
a condition that affects your ability to control your blood sugar level
81
what is type 1 diabetes?
- type one diabetes is where the pancreas produces little or no insulin
- this means a person's blood glucose level can rise to a level that can kill them
- people with type 1 diabetes must take insulin therapy which involves several injections of insulin throughout the day
- As well as insulin therapy, people with type 1 diabetes need to think about limiting the intake of food rich in simple carbohydrates and taking regular exercise
82
what is type 2 diabetes?
- type 2 diabetes is where a person becomes resistant to their own insulin
- this can also cause a person's blood sugar level to rise to a dangerous level
- type 2 diabetes can be controlled by eating a carbohydrate-controlled diet and getting regular exercise
83
what is a risk factor of type 2 diabetes?
obesity
84
what are the three ways humans lose water?
- water leaves the body via the lungs during exhalation
- water, ions and urea are lost from the skin in sweat
- urine (some reabsorbed in the kidney)
85
how does the body control how much water leaves the body through urination?
- if the blood is too dilute, the kidneys remove the excess water
- as well as excess water, urea and excess ions are also removed in urine
86
how do the kidneys remove the waste product urea?
- blood enters the kidney through an artery and this blood contains the waste product urea
- the kidney removes this urea as well as excess ions and excess water
- these leave the kidney as urine and this is stored in the bladder
- blood now leaves the kidney through a vein. The blood now contains no urea
87
how do the kidneys adjust the level of molecules in the blood?
- the blood passes through the capillaries. Here small molecules are filtered out of the blood -> these include urea, irons and water, as well as glucose
- now, all of the glucose, some of the ions and some of the water is reabsorbed back into the blood - this is called selective reabsorption
- urea, excess ions and excess water are released as urine
88
how do the kidneys adjust the level of molecules in the blood?
- the blood passes through the capillaries. Here small molecules are filtered out of the blood -> these include urea, irons and water, as well as glucose
- now, all of the glucose, some of the ions and some of the water is reabsorbed back into the blood - this is called selective reabsorption
- urea, excess ions and excess water are released as urine
89
where is urea made?
in the liver
90
how does the body react to excess amino acids?
- so the liver breaks down the excess amino acids and produces the chemical ammonia
- this process is called deamination
- ammonia is a very toxic chemical so the liver immediately converts it to urea
- the urea can be then safely excreted by the kidneys
91
what happens when the level of water in the blood is low?
- the blood becomes too concentrated, then the pituitary gland releases the hormone ADH into the bloodstream
- ADH travels into the kidneys and it causes the kidney tubules to become more permeable to water (more water can now pass out of the kidney tubules)
- this means that more water is reabsorbed from the tubules back into the blood
- because of this, less water is produced and the amount of water in the blood rises back to its normal level
- As the level of water in the blood returns to normal, the pituitary gland stops releasing ADH
- this is called negative feedback cycle
92
what happens when the level of water in the blood is high?
- if the blood is too dilute, the pituitary gland stops releasing ADH
- this means that the kidneys reabsorb less water into the blood
- now, more urine is produced and the concentration of water in the blood returns back to normal
93
what are two treatments for people with kidney failure?
- dialysis treatment
- kidney transplant
94
why is kidney failure dangerous?
- when a patient has kidney failure, their blood will contain a higher concentration of water, ions and urea than it should
95
how does a dialysis machine work?
- in kidney dialysis, the patient's blood passes over a partially permeable membrane
- this allows urea, ions and water through but it will not allow larger molecules such as proteins to pass through
- blood cells are also too large to pass through the membrane
96
what are the limitations of dialysis?
- requires rigid diet
- the skin is repeatedly punctured which can lead to infections and blood clots
97
what are limitations of having a kidney transplant?
- risk of rejection
- immunosuppressant drugs needed, which reduce the productions of antibodies, can lead to other diseases
98
why might a transplanted kidney be rejected?
- the immune system produces antibodies which attack the antigens on the transplanted kidney
99
how can we reduce the rejection of a transplanted kidney?
- taking immunosuppressant drugs
- tissue typing - the donor has a similar tissue type to the patient
100
what is the function of reproductive hormones during puberty
reproductive hormones during puberty cause the development of sexual characteristics
101
what is the main female reproductive hormone?
- Oestrogen is the main female reproductive hormone produced in the ovary
- At puberty eggs begin to mature and one is released approximately every 28 days. This is called ovulation
102
what is the main male reproductive hormone?
- Testosterone is the main male reproductive hormone produced by the testes and it stimulates sperm production
103
what occurs during the menstrual cycle?
- every 28 days, ovulation takes place
104
what occurs during the menstrual cycle?
- every 28 days, ovulation takes place
105
what occurs during the menstrual cycle?
- every 28 days, ovulation takes place (the ovary releases an egg)
- in preparation for this, the uterus lining becomes thick and spongy
- the egg makes its way down to the uterus
- if the sperm is present, then the egg can be fertilised and develop into a baby
- if the egg does not get fertilised then both the egg and the uterus lining are released
- we call this a period
106
what is the function of FSH?
- Follicle-stimulating hormone (FSH) causes an egg to mature in the ovary
107
what is the function of LH?
- Luteinising hormone (LH) causes this egg to be released, in other words, ovulation
108
what is the function of Oestrogen and progesterone?
- oestrogen and progesterone are involved in maintaining the uterus lining, incase the egg is fertilised and implants
109
what are the stages of the menstrual cycle involving the four hormones?
- in the first stage, follicle-stimulating hormone (FSH) is released by the pituitary gland
- FSH travels in the blood to ovaries where it causes an egg to mature
- at the same time, FSH triggers the ovaries to make oestrogen
- oestrogen causes the lining of the uterus to become thick
- oestrogen also stops the pituitary gland from releasing any more FSH
- the pituitary gland now releases LH
- LH triggers ovulation - the mature egg is released
- once the ovary has released its egg, the ovary now produces the hormone progesterone
- progesterone stops the pituitary gland from releasing FSH and LH
- that is to prevent any more eggs from maturing or being released
- progesterone keeps the lining of the uterus thick in case a fertilised egg implants
- if fertilisation does not take place, then the level of progesterone falls
- the uterus lining and the egg are now released and the woman has a period
110
what are the two types of oral contraceptives?
- combined contraceptive pill
- mini pill
111
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
112
what are the advantages and disadvantages of the contraceptive pill?
- it is highly effective if it is taken correctly
- however, it must be taken every day - if a woman forgets to take it, then there is a risk of pregnancy
- sometimes there are side effects such as increased risk of breast cancer or blood clots
113
what is the contraceptive patch?
- contains both oestrogen and progesterone
- it is a patch that is placed onto the skin for 7 days at a time
114
what is the contraceptive implant?
a small rod inserted under the skin which continuously releases the hormone progesterone - lasts for 3 years
115
what is the contraceptive injection?
an injection containing the hormone progesterone - lasts for approx 3 months
116
what is a barrier method of contraception?
- a barrier method of contraception involved a physical separation between the sperm and the egg. They include:
- condoms
- diaphragms
117
how do fertility drugs increase the chance of pregnancy?
- many fertility drugs contain FSH - which stimulates oestrogen production and maturation of eggs in the ovary
- they also contain LH which triggers ovulation
118
what is IVF?
- type of fertility treatment where mother is given FSH and LH - stimulates maturation of eggs and ovulation
- eggs are fertilised using sperm in a laboratory - develop into embryos
- 1 or 2 embryos are inserted into the mother's womb
119
what are the advantages of fertility treatment?
- allows infertile couples to have children
- can store a woman's eggs for later
120
what are the disadvantages of fertility treatment?
- it can be a very expensive process
- a low success rate
- side effects of fertility drugs
121
where are the adrenal glands located?
at the top of the kidneys
122
what are the effects of adrenaline?
- one of the effects of adrenaline is to increase the heart rate. Because the heart is beating faster, more oxygen and glucose are delivered in the blood to the brain and muscles
- both oxygen and glucose are needed for aerobic respiration. This prepares the body to either fight or run away. Scientists call this fight or flight
123
what are the effects of thyroxine?
- firstly, thyroxine stimulates the body's basal metabolic rate
- thyroxine makes the body's chemical reactions take place at a faster rate
- thyroxine plays an important role in the growth and in development
- the level of thyroxine inn the blood is controlled by negative feedback
124
what is metabolism?
the sum of all the reactions in a cell or the body
125
what are the types of stimuli that plants respond to?
- light (phototropism)
- water (hydrotropism)
- gravity (geotropism)
126
what is "tropism"?
response of a plant to stimuli
127
what controls growth in plants in response to stimuli?
the hormone auxin
128
where is auxin produced?
in the tips of the roots and shoots
129
how does auxin move through the plant?
by diffusion
130
what happens to the growth of a shoot when light was shone from one side?
- auxins are produced at the tip of the shoot
- the side of the shoot facing the light receives more light
- there will be an unequal distribution of auxin as the auxin will diffuse to the shaded side of the shoot
- more auxin will be found on the shaded side of the plant
- auxin causes the cells on the shaded side to grow more bending the shoot towards the light
131
why does the root bend towards gravity?
- the root bends towards gravity because auxins are produced in the tip but move toward the lower side of the root due to gravity
- in the root, auxin slows down growth and there are more auxins on the lower side, so the lower side grows slower than the top side, causing it to bend downwards
132
what is positive gravitropism?
- when auxin moves to the lower side of a root causing an unequal distribution of auxin
- as auxin inhibits growth in roots, the cells in the upper side of the roots will grow faster/ elongate
133
what is negative gravitropism?
- when auxins will gather on the lower side of the shoot causing an unequal distribution of auxin
- as auxin stimulates growth in shoots, the cells on the lower side will elongate/ grow faster
134
why is it useful for a young root to grow towards gravity?
- to anchor the plant
- to take in water
- to take in more minerals or ions
135
when investigating plant response to light, what are the control, dependent and independent variables?
control = volume of water added, temperature, number of seedlings in each pot, type of seedlings
independent = light intensity
dependent = height of seedling growth
136
how can you measure the height of a curved seedling?
- using a flexible ruler
- using a piece of string and measuring the length of the string
137
what are 3 commercial uses of auxin?
- weed killer
- rooting powders to grow cuttings
- promoting growth in tissue culture
138
what are gibberellins involved in?
seed germination
139
what hormone helps ripen fruit?
ethene
140
what are three commercial uses of gibberellins?
- promotes flowering
- increases size of fruit
- ends seed dormancy so seeds germinate
