homeostasis and response Flashcards
(62 cards)
1
Q
what is homeostasis
A
regulating the conditions inside your body and cells to maintain a stable internal environment in response to changes in both internal and external conditions
2
Q
what are automatic control systems
A
- they regulate your internal environment
- these include both nervous and hormonal communication systems
3
Q
examples of automatic control systems
A
- systems that maintain your body temperature
- systems that maintain your blood glucose
- systems that control your water content
4
Q
what is automatic control systems made up of
A
- receptors
- coordination centres
- effectors
5
Q
what is negative feedback
A
your automatic control system uses the mechanism negative feedback when the level of something gets too high or too low, using negative feedback to bring it back to normal
6
Q
what happens when the level of something decreases in the body
A
- receptors detect a stimulus (level is too high)
- the coordination centre the organises a response
- effectors produce a response, which counteracts the change and restores the optimum level - the level decreases
- the effectors will just carry on producing the responses for as long as they are stimulated by the coordination centre.
7
Q
what is a stimulus
A
a change in the environment
8
Q
what happens when the level of something increases
A
- receptors detect a stimulus - level is too low
- the coordination centre receives and processes the information, then organises a response
- effectors produce a response, which counteracts the change and restores the optimum level- the level increases
- the effectors will just carry on producing the responses for as long as they are stimulated by the coordination centre. this might causes the opposite problem by making the level change too much. luckily the receptor detects if the level becomes too different and negative feedback starts again.
9
Q
how single cell organisms respond compared to multicellular organisms
A
- a single celled organism can just respond to its environment, but the cell of multicellular organisms need to communicate with each other first.
- so as multicellular organisms evolved, they developed nervous and hormonal communication systems
10
Q
what does the nervous system do
A
means that humans can react to their surrounding and coordinate their behaviour
11
Q
what does the nervous system consist of
A
- CENTRAL NERVOUS SYSTEM - in animals, this contains the brain and spinal cord. in mammals, the CNS is connected to the body by sensory neurones and motor neurones
- SENSORY NEURONES - the neurones carry information as electrical impulses from the receptors to the CNS
- MOTOR NEURONES - the neurones that carry electrical impulses from the CNS to effectors
- EFFECTORS - all your muscles and glands, which respond to nervous impulses
12
Q
how can receptors and effectors can form parts of complex organs
A
- receptors are cells that detect stimuli
- there are many different types of receptors, eg taste receptors on the tongue or sound receptors in the ears
- receptors can form part of larger, complex organs eg. the retina of the eye is covered in light receptor cells
- effectors can respond to nervous impulses and bring about a change
- muscles and glands are known as effectors - they respond in different ways. muscles contract in response to a nervous impulse, whereas glands secrete hormones
13
Q
how does the CNS coordinate a response
A
it receives information from the receptors and then coordinates a response, the response is carried out by effectors
14
Q
what do neurones do
A
transmit information very quickly to and from the brain
15
Q
what is a synapse + how do they transfer nerve signals
A
they are the connection between two neurones
the nerve signal is transferred by chemicals which diffuse across the gap
these chemicals then set off a new electrical signal in the next neurone
16
Q
which is quicker a reflex or neurones
A
a reflex
17
Q
how do reflexes help prevent injury
A
- reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain - they can reduce the chances of being injured
18
Q
examples of how reflexes prevent injury
A
if you get a shock, your body releases adrenaline automatically
if someone shines a bright light in your eyes, your pupil automatically get smaller so that less light goes into your eyes. this stops them getting damaged
19
Q
how does the reflex arc go through the CNS
A
- the neurones in reflex arcs go through the spinal cord or through the unconscious part of the brain
- when a stimulus is detected by receptors, impulses are sent along a sensory neurones to a relay neurone in the CNS
- when impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. these chemicals causes impulses to be sent along the relay neurone
- when the impulses reach a synapse between the relay neurone and a motor neurone, the same thing happens. chemicals are released and causes the impulse to be sent along the motor neurone.
- the impulses then travel along the motor neurone to the effector
20
Q
what is reaction time
A
the time it takes you to respond to a stimulus
21
Q
what can reaction time be effected by
A
age, gender, drugs
22
Q
how to investigate reaction time + the control variables
A
- persons should sit with their arm resting on the edge of a table
- hold a ruler between the thumb and forefinger. make sure that the zero end of the ruler is level with the thumb and finger
- let go without warning
- reaction time is measures by the number on the ruler when caught
- repeat several times then calculate the mean distance
control variables - same person, same hand, dropped from the same height
23
Q
what is the brain made up of + what does it do
A
- made up of billions of interconnected neurones
- specifically made up of
- cerebral cortex : responsible for
things like consciousness,
intelligence, memory and language - medulla : control unconscious
activities eg. breathing and
heartbeat - cerebellum : muscle coordination
- spinal cord
- cerebral cortex : responsible for
- in charge of complex behaviours
24
Q
what methods to scientist use to study the brain
A
- studying patients with brain damage : if a small part of the brain has been damaged, the effect this has on the patient can tell you a lot about what the damaged part of the brain does
- electrically stimulating the brain : the brain can be stimulated electrically by pushing a tiny electrode into the tissue and giving it a small zap. by observing what stimulating different parts of the brain does, its possible to get an idea of what those parts do
- MRI scans : they produce very detailed pictures of the brain structure so you can see what area of the brain is active
25
the characteristics of the eye and what they do
- sclera : tough supporting wall of the eye
- cornea : is the transparent outer layer found at the front of the eye. it refracts light into the eye
- iris : contains muscles that allow it to control the diameter of the PUPIL (the hole in the middle) and therefore how much light enter the eye
- lens : focuses the light onto the RETINA (contains receptors sensitive to light intensity and colour)
- ciliary muscles and suspensory ligaments : control the shape of the lens
- optic nerve : carries impulses from the receptors on the retina to the brain
26
how does light affect the eyes
- when light receptors in the eye detect a very bright light, a reflex is triggered that makes the pupil smaller. the circular muscles in the iris contract and the radial muscle relax. this reduces the amount of light that can enter the eye
- when there is dim light, the radial muscles contract and the circular muscles relax which makes the pupil wider therefore allowing more light to enter
27
how does the eye focus on object far and close
close : the ciliary muscles contract which relaxes the suspensory ligaments. the lens becomes fat. this increases the amount at which it refracts light
distant : the ciliary muscles relax which allows the suspensory ligaments to pull tight. this makes the lens go thin so it refracts a smaller amount of light
28
long sighted
unable to focus on near objects.
occurs when the lens is the wrong shape and doesn't refract the light enough or the eyeball is too short
the image of near objects are brought into focus behind the retina
you can uses glasses with a convex lens. the lens refracts the light rays so they focus on the retina
hyperopia
29
short sighted
unable to focus on distant objects
occurs when the lens is the wrong shape and refracts light too much or the eyeball is too long
the image of distant objects are brought into focus in front of the retina
use glasses with concave lens so that the light rays focus on the retina
myopia
30
treatment to treat vision defects
contact lenses - sit on the surface of the eye
convenient, lightweight and almost invisible
laser eye surgery - vaporise the tissue changing the shape of the cornea. slimming it down makes it less powerful and can improve short sight. surgery has risks
replacement lens surgery - eye is removed and artificial lens made of clear plastic is inserted
31
what are hormones
chemical molecules released directly into the blood. hormones control things in organs and cells that need constant adjustments
32
where are hormones produced
in glands called endocrine glands
33
what hormones are made in what glands
1. pituitary gland - produce many hormones that regulate body conditions. sometimes called master gland as hormones act on other glands, directing them to release hormones that bring about change
2. ovaries - produce oestrogen
3. testes - produce testosterone
4. thyroid - produces thyroxine which involves regulating things like metabolism rate, heart rate and temperature
5. adrenal gland - produce adrenaline
6. pancreas - produces insulin which regulates blood glucose levels
34
what is the difference between hormones and nerves
nerves - very fast action
act for short time
act on precise area
hormones - slower action
act for long time
act in a general way
35
what are the 2 hormones involved in controlling blood glucose
insulin and glucagon
36
how does normal metabolism work
1. eating foods that contains carbohydrates puts glucose into the blood from the gut
2. normal metabolism removes glucose from blood
3. vigorous exercise removes more glucose
37
what happens to excess glucose
stored as glycogen in the liver and muscles
38
what happens when blood glucose is too high
1. insulin is secreted by the pancreas
2. glucose moved from blood into liver and muscle cells while the insulin also makes liver turn glucose into glycogen
blood glucose reduces
39
what happens when blood glucose is too low
1. glucagon is secreted by pancreas
2. glucagon released into blood by liver while the glucagon also makes liver turn glycogen into glucose
blood glucose increased
40
type 1 diabetes
when the pancreas produces little to no insulin. have to inject insulin
41
type 2 diabetes
a person becomes resistant to their own insulin
being overweight increases risk
control diet
42
reproductive hormones and where they are produced and what they stimulate
testosterone - testes and stimulates sperm production
oestrogen - ovaries and bring physical changes and is involved in the menstrual cycle
43
explain each stage of the menstrual cycle
1. the uterus lining break down for about 4 days
2. the uterus lining builds up again, from day 4 - 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
3. an egg develops and is released from the ovary at day 14 this is called ovulation
4. the wall is then maintained for about 14 days until day 28. if no fertilised egg has landed on the uterus wall by day 28, the spongy lining start to break down and the cycle start again
44
what 4 hormones is the menstrual cycle controlled by and what do they do
FSH - produced in the pituitary gland. causes egg to mature in a structure called a follicle. stimulates the ovary to produce oestrogen
oestrogen - produced in the ovaries. causes the lining of the uterus to grow. stimulates the release of LH and inhibits release of FSH
LH - produces in pituitary gland. stimulates the release of an egg at day 14
progesterone - produced in ovaries by the remains of the follicle after ovulation. maintain the lining of the uterus during 2nd half of the cycle. when the level of progesterone falls, the lining breaks down inhibits the release of LH and FSH
45
hormones that reduce fertility
- oestrogen can be used to prevent the release of an egg
- if taken everyday then the level is always high which inhibit production of FSH
- progesterone also reduces fertility
- stimulates the production of thick mucus to stop sperm reaching the egg
- the pill has both oestrogen and progesterone
- progesterone only pill has less side effects
46
methods on contraception that use hormones
- contraceptive patch - contain oestrogen and progesterone
- implant - progesterone
- injection - progesterone
- IUD - in uterus to kill sperm. releases progesterone and copper IUD prevent sperm surviving in uterus
47
non hormonal contraceptions
(barrier methods)
- condoms
- diaphragm - fits over cervix. has to be used with spermicide
- spermicide - can be used alone but not as effective
48
other ways to avoid pregnancy
- sterilisation - cutting or tying fallopian tubes or sperm duct
- natural methods
- abstinence - not having intercourse
49
hormones that can be used to increase fertility
pros and cons
FSH and LH can be given as a fertility drug to stimulates ovulation
pros - help get pregnant
cons - doesn't always work, expensive, too many eggs = multiple pregnancies
50
IVF
pros and cons
collecting eggs and fertilising them with mans sperm in a lab.
they are then grown into embryos then transferred into a woman's uterus
pros - can give infertile people a child
cons - multiple birth, success rate is low, emotionally stressful, can have physical reaction eg. vomiting, dehydration
51
why are some people against IVF
results in unused embryos which are destroyed ---> some people think this is unethical
52
where is adrenaline released from and when is it released
released by the adrenal glands
adrenaline is released in response to stressful or scary situation - yours brain detects fear or stress and sends nervous impulses to the adrenal glands
get ready for flight or fight by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles
53
how does your body control level of hormones in the blood
negative feedback
54
where is thyroxine released and what does it do
- thyroid gland
- regulates the basal metabolic rate
- it also stimulates protein synthesis for growth and development
- released in response to thyroid stimulation hormone which is released in pituitary gland
55
how does TSH and thyroxine work together
- when the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited.
- this reduces the amount of thyroxine released from the thyroid gland so the level in the blood falls back to normal
56
what is auxin
- plant hormone that controls growth near the tips of shoots and roots
- control growth in response to light - phototropism - and gravity - gravitropism or geotropism
- auxin is produced in the tips and moves backwards to stimulate the cell elongation process which occurs just behind the tips
- if the shoot is removed, no auxin is available and the shoot may stop growing
- extra auxin growth in the shoot inhibits growth in the root
57
what happens when a shoot tip is exposed to light
more auxin accumulates on the side thats in the shade than the side in the light
this makes the cell grow faster on the shaded side so the shoot bends TOWARDS the light
58
what happens when a shoot is growing sideways
gravity produces an unequal distribution of auxin in the tip, more auxin on the lower side
this causes the lower side to grow faster, bending the shoot upwards
in a root, extra auxin inhibits growth meaning the cells on top elongate faster and the root bends downwards
59
how to investigate plant growth responses
1. put 10 seed on a petri dish lined with moist filter paper
2. shine a light onto 1 petri dish from above and the other from different directions
3. leave for a week
60
how is auxin useful
killing weeds
growing from cuttings with rooting powder
growing cells in tissue culture
61
what is gibberellin and how is it used
- stimulates seed germination, stem growth and flowering
- controll dormancy
inducing flowering
growing larger fruit
62
how is ethene used
stimulates ripening of fruit
