Homeostasis and response Flashcards
(109 cards)
1
Q
What is homeostasis needed for ?
A
- enzyme action
- all cell functions
2
Q
What does homeostasis control in the human body?
A
- blood glucose concentration
- body temperature
- water levels
3
Q
What are nervous and hormonal communication involved in?
A
The automatic control systems, which detect changes and respond to them
4
Q
What do all control systems have?
A
- receptors
- coordination centres
- effectors
5
Q
What does the nervous system allow us to do?
A
- react to our surroundings
- coordinate actions in response to stimuli
6
Q
Describe structure of nervous system and what occurs
A
- receptor cells convert a stimulus into an electrical impulse
- electrical impulse travels along cells called SENSORY NEURONS to the CNS
- Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along MOTOR NEURONES to effectors
- the effectors carry out the RESPONSE ( muscles contracting/ glands secreting hormones)
7
Q
Why are reflexes important?
A
Prevent individual from getting hurt as information travels down a pathway called a reflex arc, allowing vital responses to take place quickly
8
Q
How is a reflex arc pathway different from the usual response to stimuli?
A
The impulse does not pass through the conscious part of the brain
9
Q
Describe the reflex arc
A
- stimulus detected by receptors
- impulses sent along a sensory neuron
- in the CNS the impulse passes to a relay neuron
- impulses are sent along motor neuron
- impulse reaches an effector resulting in the appropriate response ( pupils getting smaller)
10
Q
Describe what occurs when the impulses reaches the end of the first neurone
A
- a chemical is released into the synapse
- chemical diffuses across the synapse
- when chemical reaches the second neurone, it triggers the impulse to begin again in the next neurone
11
Q
Describe synaptic transmission
A
- incoming electrical impulse causes neurotransmitters to move to the membrane
- neurotransmitter is released into synapse
- neurotransmitter binds to SPECIFIC receptors on the membrane of the next neurone
- electrical impulse continues to effector
12
Q
What is reaction time and how can’t it be measured?
A
- how long it takes you to respond to a stimulus
- can be measured with the ruler drop test
13
Q
Name the 3 components of the brain and describe them
A
Cerebral cortex - controls consciousness, intelligence, memory and language, it is the outer part of the brain
Cerebellum- controls fine movement of muscles, rounded structure towards the bottom/ back of the brain
Medulla- controls unconscious actions ( breathing, heart rate ), found in the brain stem in the front of the cerebellum
14
Q
Why is investigating brain function and treating brain damage/disease difficult?
A
- is complex and delicate
- is easily damaged
- drugs given to treat diseases cannot always reach the brain because of the membranes that surround it
- is not fully understood which part of the brain does what
15
Q
Name methods for studying the brain and describe them
A
- studying patients with BRAIN DAMAGE - observing the changes in an individual following damage on a certain area of the brain, can provide information on the function this area has
- ELECTRICAL STIMULATION- use electrical currents to stimulate different parts of the brain to learn functions of specific neurones as the stimulation may result in a mental or physical change
- MRI - magnetic resonance imaging scanner can be used to create an image on the brain which can show which part of the brain is affects by a tumour or which part is active during a specific task
16
Q
Function of retina
A
Layer of light sensitive cells found at the back of the eye.
When light hits this, the cells are stimulated. Impulses are sent to the brain, which interprets the information to create an image
17
Q
Optic nerve function
A
A nerve that leaves the eye and leads to the brain
Carries the impulses from the retina to the brain to create and image
18
Q
Sclera function
A
White outer layer which supports structures inside the eye
Is strong to prevent damage it the eye
19
Q
Cornea function
A
The see-through layer at the front of the eye
It allows light through and the curved surface bends and focuses light onto the retina
20
Q
Function of iris
A
Muscles that surround the pupil
They contract or relax to alter the size of the pupil
21
Q
Function of ciliary muscles and sensory ligaments
A
Hold the lens in place
They control its shape
22
Q
Describe what happens to the iris in bright light
A
The circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damage to retina
23
Q
Describe what happens to the iris in bright light
A
The circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damaging to retina
24
Q
Describe what happens to the iris in dim light
A
The circular muscles relax and the radial muscles contract to make the pupil larger- so more light can enter to create a better image
25
Define accommodation
The process of changing the shape of the lens to focus on near or distant objects
26
What happens when focussing on a near object
The ciliary muscles contract
The suspensory ligaments loosen
The lens is then thicker and more curved
Meaning light rays are refracted more/strongly
27
What happens when focussing on a distant object
The ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner- meaning light rays are only slightly refracted
28
When do eye defects occur and name 2 common ones
Occurs when light can’t focus on the retina
Myopia (short sightedness) the lens is too curved so distant objects appear blurry
Hyperopia (long sightedness) the lens is too flat so it can’t refract light enough
29
Name treatments for eye defects
Spectacle lenses (glasses) - concave lenses to spread out the light to treat myopia and convex lenses to bring the rays together to treat hyperopia
Contact lenses- work the same as glasses but allow activities (sport) to be carried out
Laser eye surgery- lasers can be used to either reduce the thickness of the cornea (so it refracts light less) to treat myopia or change its curvature (so it refracts light more strongly) to treat hyperopia
Replacement lens- hyperopia can be treated by replacing the lens with an artificial one made of clear plastic. The risk include damage to retina or cataracts developing
30
What is thermoregulation
The process that allows your body to maintain its core internal temperature (37degrees)
31
What is the thermoregulatory centre and what does it do?
Monitors and controls body temperature and is found in the brain
-has receptors that monitor the temp of the blood
-has receptors in the skin that send impulses to the thermoregulatory centre
32
How do our bodies respond when our bodies are too hot?
-sweat glands produce sweat because evaporation of water from sweat takes heat away from body
-blood vessels dilate (vasodilation) as more blood flows closer to the surface of skin, allowing heat to escape
-hairs lie flat so body is able to loose heat
33
How do our bodies respond when our bodies are too cold?
-sweating stops, so heat energy is not lost
-shivering - skeletal muscles contract rapidly to generate heat from respiration
-hairs stand on end to create an insulating layer, trapping warm air
-blood vessels constrict (vasoconstriction) meaning less heat radiated from skins surface, less heat lost
34
What is the role of the endocrine system?
Sends hormones (chemical messengers) around the body
When they reach a target tissue they produce a response
Is made up of glands which secrete hormones directly into bloodstream
35
Function of pituitary gland
The master gland
Secretes hormones into the blood to either have an effect on the body or to act on other glands to stimulate them to produce different hormones
36
What is the function of pancreas?
Secretes insulin
Controls blood glucose levels
37
Function of thyroid
Secretes thyroxine
Controls metabolic rate, heart rate and temp
38
What is the function of adrenal gland?
Secretes adrenaline
Involved in the flight or fight response
39
What is the function of ovaries
Secretes oestrogen
Involved in the menstrual cycle and the development of female secondary sexual characteristics
40
What is the function of testes
Secretes testosterone
Involved in production of sperm and the development of male secondary sexual characteristics
41
What is a difference between the nervous and endocrine systems
Endocrine in much slower but it lasts for longer
42
Why does the concentration of glucose in blood need to be kept within a certain limit
As glucose is needed by cells for respiration- controlled by pancreas
43
What increases glucose levels in blood?
Eating foods that contain carbohydrates
44
What happens if blood glucose levels are too high?
The pancreas releases insulin into blood
Insulin causes cells and tissues to absorb glucose which will be used for respiration
Excess glucose is converted to glycogen by liver
Blood sugar level returns to normal
45
What causes blood glucose to decrease
Rigorous activity as it uses glucose for respiration meaning there is less in blood
46
What happens when blood glucose levels are too low
Pancreas releases the hormone glucagon
Glucagon binds to the liver cells causing glycogen to be broken down into glucose
Glucose is released into blood, increasing blood glucose concentration, so it returns back to normal
47
What is type 1 diabetes and what causes it
When pancreas can’t produce enough insulin
Usually starts in young children or teenagers
Cause could be a genetic element
48
What are the symptoms of type 1 diabetes
Blood glucose can rise to a fatal amount
Glucose is excreted with urine and lots of urine is produced leaving individual thirsty
Lack of energy
Weight loss
49
What are the treatments for type 1 diabetes?
Insulin injections at meal times which results in glucose being taken up from bloodstream
Advised to limit the intake of simple carbohydrates which contain lots of glucose
Doctors are attempting to cure diabetes with pancreas and pancreatic cell transplants and genetically engineering pancreatic cells from mice to make insulin
50
What is type 2 diabetes and what is a risk factor/cause?
When the body cells no longer respond to insulin
Risk factor/cause- obesity and lack of exercise
51
What is a symptom of type 2 diabetes?
Blood glucose levels can rise to a fatal amount
52
What are the treatments for type 2 diabetes?
Reducing number of simple carbohydrates in diet
Losing weight
Increasing exercise
Also drugs to make insulin more effective on body cells, help the pancreas make more insulin or reduce amount of insulin absorbed in gut
53
What happens if body cells lose or gain too much water by osmosis
They don’t function properly
54
What is the function of the kidneys?
Maintains the balance of water and other substances in body by removing toxic urea from the body in urine
As urine is produced constantly the bladder must store it
55
How do kidneys make urine?
By filtering out the waste products
And selectively reabsorbing useful substances- all glucose, some ions and some water
56
What happens when there is too much water in blood ?
The hypothalamus detects too much water in blood
Pituitary gland secretes ADH into blood
It travels in the bloodstream to the kidney tubules
The tubules (walls of kidney) become less permeable to water
So less water returns to blood via bloodstream
More water is lost in urine (less concentration)
Water levels return back to normal (negative feedback loop)
57
What will happen to the volume of urine produced when ADH is secreted?
Causes more water to be reabsorbed back into blood via osmosis
Low volume of concentrated urine produced
58
Define kidney failure
When your kidneys stop working
Meaning waste products build up which can be harmful to the body, eventually resulting in death
59
Explain a different way water can leave the body
Can leave the body at the lungs as a result of exhalation or from the skin in sweat
Depending on the concentration of water in the blood, a certain amount of water is lost in urine
60
Explain how ions are taken in and leave the body
Taken in via food
If ion concentration is incorrect then too little or too much water may enter body cells. This is because the water potential of the blood would be altered
They are least in sweat
In kidneys, certain amounts of ions are reabsorbed into blood after it has been filtered to ensure the concentration in blood is maintained
61
How does urea leave the body
Amino acids are the products of the digestion of proteins
Amino acids are deaminated (removal of an amino acid group from an amino acid) in the liver to form ammonia. As ammonia is toxic it’s converted to urea for safe excretion
Is lost in sweat
In the kidneys, it’s filtered out of blood
62
What does anti-diuretic hormone (ADH) control?
Controls the amount of water reabsorbed by kidneys/loss of water as urine
63
What is diuretic?
Chemical that increases urination
64
Where is ADH released and when?
Released into the pancreas by the pituitary gland when a receptor in the brain detects that blood is too concentrated
65
Explain how the structure of the kidneys helps carry out its function
Kidney contains millions of filtering units called nephrons
Each nephron is made of a tubule and is responsible for cleaning the blood by removing urea and excess water and minerals
All of the blood in the body passes through your kidney once every 5 mins
66
Describe what a nephron does in the kidney
-Blood enters under high pressure
-Filtration- small molecules (glucose,water,mineral ions, urea) are forced out of blood into tubules
-Larger molecules (red blood cells,larger proteins) remain in bloodstream
-the filtered liquid passes through the tubule
- selective reabsorption- useful substances are absorbed back into blood
- remaining liquid forms urine
- urine travels to the bladder for storage
67
Describe the 2 functions for kidney failure
Dialysis- when the function of the kidneys it carried out using an artificial membrane
-Blood moves between partially permeable membranes surrounded by dialysis fluid
-Useful ions and glucose are not lost from blood but urea, excess ions and water diffuse across the membrane
-has to be done 3 times a week, the process takes 4 hours
-acts as an artificial kidney and keeps patient alive whilst waiting for a transplant
Disadvantage- Can cause blood clots, takes a lot of time, have to follow strict diet, build up of waste products between sessions can make u feel ill
Kidney transplant - providing individual with healthy kidney, only cure
Transplanted from people who died suddenly, or from people still alive
Don’t need to visit hospital as regularly and is cheaper than dialysis
Disadvantage- can be rejected from body as a result of immune system recognising the antigens in donor organ as foreign ( reduced by immunosuppressant drugs)
Person can be left vulnerable to other diseases
Transplanted kidneys don’t last forever
68
What happens during puberty?
Reproductive hormones begin to be released
These cause secondary sexual characteristics to develop in men and women
69
What primary sex characteristics are u born with?
Females- ovaries
Male- testes
70
Describe the sex hormones in men and women
Male- testosterone, produced in testes, stimulates the production of sperm
Female- oestrogen, produced in ovaries, produces physical changes and is involved in menstrual cycle
71
What happens to females during puberty?
Eggs being to mature
One is released from ovaries approximately every 28 days- this is called ovulation
72
State the role of female sex organs
Fallopian tube/oviduct- egg travels
Ovaries- eggs mature
Uterus/ womb- foetus develops
Cervix - entrance to the uterus
73
Define menstrual cycle
The regular natural changes that occurs in the uterus and ovaries that make pregnancy possible
74
Define what occurs during menstrual cycle
Begins with the lining of uterus breaking down, women has her period
They layer then builds up again until ovulation (day 14) occurs - an egg is released from the ovary and moves to the uterus via fallopian tube
If a fertilised egg hasn’t been embedded in the lining after 28 days, it begins to break down and cycle continues
75
Name and describe the main hormones involved in menstrual cycle
Follicle stimulating hormone (FSH) - causes the maturation of an egg in the ovary. Produced in pituitary gland and stimulates the ovaries to produce oestrogen
Oestrogen- causes the lining of uterus to grow again. Produced in ovaries, secreted as a result of FSH.stimulates the production of LH and inhibits the secretion of more FSH
Lutenising hormone (LH) - produced in pituitary gland as a result of hormone oestrogen. Its release results in ovulation
Progesterone- produced in ovaries and secreted from egg follicle, maintains lining of uterus and supports pregnancy of egg is fertilised. Inhibits release of FSH and LH
76
Describe hormonal methods of contraception
The contraceptive patch - taken regularly or bodies own hormones will be released, leading to egg maturing
Mixed pill contains oestrogen and progesterone
Means oestrogen levels are constantly high, inhibiting FSH so no eggs mature
Lining stops developing and mucus in cervix becomes thick so sperm can’t move through
Side effects- mood swings, depression, high blood pressure
Progesterone only pill- has less side effects in comparison to mixed pill
The contraceptive patch- contain oestrogen and progesterone
Is small and stuck on skin
Lasts for 1 week
The contraceptive implant- releases a continuous amount of progesterone
Prevents ovaries from releasing egg, thickens mucus so sperm can’t swim and stops fertilised eggs from embedding in uterus
Lasts for 3 years
The contraceptive injection- made up of progesterone
Same effect as implant
Lasts for 2/3 months
The plastic intrauterine device (iud) - releases progesterone
Same effect as implant
T-shaped, inserted into uterus
77
Decline non hormonal methods of contraception
Chemical methods involve spermicides. These kill or disable sperm but are only 70% effective
Barrier methods include condoms and diaphragms
Condoms prevent individual from contracting sexually transmitted diseases but can tear
Diaphragm is a plastic cup which is positioned over cervix, used with spermicides
Copper intrauterine device works by killing sperm in uterus and stopping any fertilised embryos from implanting in uterus lining
Surgical methods of male and female sterilisation involve cutting and tying the fallopian tubes or sperm ducts
Lasts forever
Abstaining from intercourse ensures egg isn’t fertilised
Others may only abstain during ovulation
78
Positive and negatives of contraceptive methods
+
Pill is easy to use
Condoms have no side effects
IUD are very effective and last up to 5 years
Implant can last up to 3 years
Spermicides are readily available
Barriers can also prevent spread of diseases
-
IUD can cause period problems and infections
Surgery is permanent
Spermicides are not thought to be very effective
Condoms can become easily damaged
Pill has side effects
Discomfort on implantation
79
Describe process of IVF
Mother is given FSH and LH to stimulate the maturation of several eggs
Eggs are collected from the mother and fertilised by sperm from father
The fertilised egg develops into embryos
When eggs are tiny balls of cells one or 2 embryos are inserted into mother’s uterus
Spare embryos can be frozen for future attempts or donated to their couples
Sometimes they are destroyed
80
What are the positives and negatives of IVF
+
Provided a way for an infertile couple to have a child
-
Physically stressful, woman may have reactions to hormones
Emotionally stressful- may not work
Can lead to multiple births
Can be expensive if process needs repeating
81
What is negative feedback
Initiating corrective mechanisms whenever the internal environment deviates from its normal or acceptable level
82
Explain what a negative feedback does
Maintains a steady state
Reverses any changes
83
Give examples of negative feedback
Insulin and glucagon
Sex hormones
Osmoregulation
Thermoregulation
84
What does thyroxine do?
Regulated metabolic rate
Also important in growth and development e.g brain development in children
85
How is thyroxine released
By the thyroid gland
It uses iodine from your diet to produce thyroxine
Its release is stimulated by the thyroid stimulating hormone
86
What is metabolism?
Sum of all the chemical reactions in body
87
What are the levels of thyroxine controlled by?
Negative feedback
88
What happens when thyroxine levels are too low?
Sensors in Brian detect decreased thyroxine levels
Pituitary gland releases thyroid stimulating hormone
Stimulates the thyroid to secrete thyroxine
Thyroxine levels rise
89
What happens when thyroxine levels are too low?
Sensors in Brian detect decreased thyroxine levels
Pituitary gland releases thyroid stimulating hormone
Stimulates the thyroid to secrete thyroxine
Thyroxine levels rise
90
What happens if thyroxine levels are too high?
Sensors in brain detect
Inhibits release of TSH
Thyroid gland secretes less thyroxine
Thyroxine levels fall
91
Where and when is adrenaline produced?
In times of fear, stress, anger or excitement
From adrenal glands
Involves no negative feedback loop
92
What are the effects of adrenaline?
Increased heart and breathing rate to deliver more oxygen and glucose to brain and muscles for respiration
Glycogen stored in liver is converted to glucose for respiration
Pupils dilate to let more light in
Blood flow to muscles increases
Blood flow to digestive system decreases
93
What detects thermoregulation
Hypothalamus
94
What would happen to our body without thermoregulation?
Hyperthermia (too cold)
Hypothermia (too hot)
95
What would happen to our body without thermoregulation?
Hyperthermia (too cold)
Hypothermia (too hot)
96
Why do plants need hormones?
To coordinate and control growth
They are needed for tropisms eg phototropism - response to light
97
How do hormones produce the appropriate response?
Hormones move from the place they are made to where they are needed in order to produce appropriate response
E.g gravitropism - response to gravity
Hydrotropism- response to water
98
What do plants need to respond to?
Light intensity and direction
Gravity (direction of root and shoot)
Water
99
What are auxins and what do they do
Specific growth hormones
They coordinate responses and control growth
These responses are known as tropisms to directional growth response causing movement of part of an organism
100
What are positive and negative tropisms
Positive- growth towards stimuli
Negative - growth away from stimuli
101
Describe phototropism in plants
Stem and leaves are positively phototrobic (grow towards light)
Contain chloroplasts which maximise photosynthesis
Roots are negatively phototrobic
102
Describe gravitropism in plants
Roots are positively gravitrobic as they grow with gravity to absorb more mineral ions and anchor plant
103
Describe hydrotropism in plants
Roots are positively hydrotrobic - grow towards water to absorb it
104
How do auxins work/ cell elongation?
Plants grow towards light
The auxins are evenly distributed so the shoot grows up
The plant is exposed to light on one side causing auxins to move to shaded side
Shoot bends towards light so only that side elongates
Plant receives more light, meaning photosynthesis can occur faster
Once light falls equally on all side of shoot, auxins distribute evenly again
105
How can u investigate the effect of light or gravity on newly germinated seedlings
By varying conditions
Placing in cardboard box and shining light from one side
Attaching a Petri dish containing seedlings to a wall
106
Describe 2 other plant hormones
Gibberellins - important to stimulate seed germination
Ethene - involved in cell division and ripening of fruits
107
Where and why are plant hormones used
Used to alter plant growth
Used in areas such as agriculture and horticulture to increase yield, obtain desirable chemicals and to lower costs
108
Define what auxins are used for
As weed killers- many weeds are broad-leaved
Weed killers containing auxin have been synthesised so they only affect broad leaved plants
Increased amount of auxin causes cells to grow too rapidly resulting in weed dying
As rooting powders- plants with desirable features are cloned to make more plants with the same feature
One way to clone is to take a cutting from original plant
Rooting powder containing auxins is applied to it and is placed in ground
Roots grow and the new plant begins to grow very quickly
To promote growth in tissue culture - another way to clone a plant is to use tissue culture
Cells form the plant are taken and placed in a growth medium containing nutrients
Hormones such as auxins are added
Cells begin to form roots and shoots
109
What are gibberellins used for?
Ending seed dormancy- in brewing industry, the germination rate of barley seeds is increased to make malt
Promoting flowering - allows it to flower in any conditions with bigger flowers
Increasing fruit size- seedless fruit is generally smaller so sprayed with givberellins to increase size
