Homeostasis and response Flashcards
(83 cards)
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 does homeostasis control
A
- Blood glucose concentration
- Body temperature
- Water levels
3
Q
Five things that co ordinate a response
A
Stimulus
Receptor
Coordinator
Effector
Response
4
Q
What are the various structures in a reflex arc, in order
A
Stimuli - Receptor - Sensory neurone - Relay neurone - motor neurone - effector
5
Q
Why are reflex actions useful
A
They are automatic and rapid, they don’t involve the conscious part of the brain
6
Q
Plan an investigation into the effect of a factor on human reaction time (6 marks)
A
- Person A holds out their hand with a gap between their thumb and first finger
- Person B holds the ruler with the zero at the top of the person A’s thumb
- Person b drops the ruler at a random time, and person A must catch it
- The number level with the top of person A’s thumb is recorded, repeat 10 times and calculate a mean
- Swap places and repeat
- Convert ruler measurements into reaction time
7
Q
What does the cerebral cortex do
A
Controls consciousness, intelligence, memory and language; it is the outer part of the brain
8
Q
What does the cerebellum do
A
Controls fine movement of muscles, and balance. Its a rounded structure at the back of the brain
9
Q
What does the medulla do
A
Controls unconscious actions such as breathing and heart rate, found in the brain stem in front of cerebellum
10
Q
Why is investigating the brain difficult
A
- It is easily damaged
- It’s complex and difficult
- Drugs may not reach the brain because of the membranes that surround it
11
Q
How can neuroscientists map out the brain (3 ways)
A
- Study patients with brain damage, damaged area corresponds to what part of body it controls
- Electrically stimulate different parts of the brain with electrode, may result in physical or mental change
- Use MRI to create image of brain, showing what part is affected by a tumour, or which part is active during specific action
12
Q
What are the eyes functions
A
- Accommodation to focus on near or distant objects
- Adaptation to dim light
13
Q
What is the 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 make an image
14
Q
What is the optic nerve
A
A nerve that leaves the eye and leads to the brain
Carries impulses from retina to brain to create an image.
15
Q
What is the sclera
A
The strong, white outer layer which supports the structures inside the eye
16
Q
What is the cornea
A
The see-through layer at the front of the eye. It allows light through and curved surface bends most of the light
17
Q
What is the iris
A
The muscles that surround the pupil
18
Q
What do the suspensory ligaments and ciliary muscles do
A
Hold the lens in place and control its shape
19
Q
What happens to the iris in bright light
A
Radial muscles relax
Circular muscles contract
Making the pupil smaller
20
Q
What happens to the iris in dim light
A
Circular muscles relax
Radial muscles contract
Making the pupil dilated
21
Q
The process of accommodation on a near object
A
- Ciliary muscles contract
- Suspensory ligaments relax
- Lens is thicker and more curved, refracting light more
22
Q
The process of accommodation on a distant object
A
- Ciliary muscles relax
- Suspensory ligaments contract
- The lens is thinner so less light is refracted
23
Q
What is myopia
A
Short sightedness
When light cannot focus on the retina as the lens is too curved.
So distant objects appear blurry
24
Q
What is hyperopia
A
Long sightedness
- Light cannot focus on the retina as the lens is too flat, so cannot refract light enough
- So close objects appear blurry
25
What are the 4 treatments to hyper and myopia
- Spectacle lenses
- Contact lenses
- Laser eye surgery
- Replacement lens
26
What does the thermoregulatory centre do
Monitors and controls body temperature
27
Where are the receptors for the thermoregulatory centre
- In the skin
- Receptors that measure temp of the blood
28
Changes body makes when temp is too high
- Vasodilation, more blood closer to the surface so more energy is transferred from the body
- Sweating, heat evaporates from skin so more energy is transferred from the body
29
Changes body makes when temp is too low
- Sweating stops
- Skeletal muscles contract rapidly to generate heat from respiration
- Hairs stand on end to create insulating layer of warm air
- Vasoconstriction means blood does not flow close to the surface, so less heat is lost
30
What is the pituitary gland
- Master gland
- Secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate them to produce different hormones
31
What does the pancreas do
- Secretes insulin
- Controls blood glucose levels
32
What does the thyroid do
- Secretes thyroxine
- Controls metabolic rate, heart rate and temperature
33
What does the adrenal gland do
- Secretes adrenaline
- Involved in 'fight or flight' response
34
What do the ovaries do
- Secretes oestrogen
- Involved in the menstrual cycle and the development of female sexual characteristics
35
What do the testes do
- Secretes testosterone
- Involved in production of sperm and development of male sexual characteristics
36
Where does the blood transport hormones
To a target organ or tissue where it has an effect
37
Why does the concentration of glucose need to be maintained
Needs to be kept within a certain limit because glucose is needed by cells for respiration
It is controlled by the pancreas
38
What hormone does the pancreas produce if glucose levels are too high
Insulin
39
How does insulin work
Binds to cells in target organs (muscles and liver) causing
1- Glucose to move from the blood into muscle cells for respiration
2 - Excess glucose to be converted into glycogen which is stored in the liver
40
What hormone is produced by the pancreas if blood glucose levels decreases
Glucagon
41
How does glucagon work
Binds to liver cells causing glycogen to be broken down into glucose
Glucose is released into the blood increasing the blood glucose concentration
42
What is type 1 diabetes
When the pancreas can't produce enough insulin.
43
How is type 1 diabetes treated
With insulin injections at meal times, which results in glucose being taken up from the blood stream
Limit intake of simple carbs which contain lots of glucose
44
What is type 2 diabetes
When the body cells no longer respond to insulin
45
How to treat type 2 diabetes
Reduce number of simple carbs you intake,
Lose weight
Increase exercise
Also drugs to make insulin more effective
46
What happens if concentration of water in the bloodstream increases
- Cells take up water through osmosis as there's a concentration gradient.
- They expand and then eventually burst
47
What happens if concentration of water in the bloodstream decreases
- Cells lose water to the bloodstream by osmosis as there is a concentration gradient
48
What happens if body cells gain or lose to much water by osmosis
They do not function properly
49
Waste products that are processed at the kidney
- Water (selectively reabsorbed)
- Urea (all filtered out)
- Ions (selectively reabsorbed)
50
What is ADH
- Anti diuretic hormone, involved in the control of the loss of water as urine
- Released by pituitary gland
51
How does ADH work
- Travels via bloodstream to the kidney tubules
- An increased amount of ADH reaching the tubules increases their permeability to water, so more water is selectively reabsorbed
- Resulting in more concentrated urine
- So more water goes back into the bloodstream
52
Why is ADH a negative feedback loop
If the concentration of the blood increases/decreases, more/less ADH is secreted to reverse this change
53
Two ways to treat people with kidney failure
- Dialysis
- Transplant
54
Problems of dialysis
Possibility of blood clots
Takes up lots of time
Have to follow a strict diet
Build up of waste products between makes you feel ill
55
What method of treating kidney failure is cheaper
Transplant
56
Problems of transplant
Chance of rejection
Left vulnerable to disease
Do not last forever
57
How can risk of rejection be decreased
Immunosuppressant drugs
58
What is the main male reproductive hormone, what does it do.
Testosterone
Produced by testes
Stimulates sperm production
59
What is the main female reproductive hormone, what does it do.
Oestrogen
Produced in ovaries
Involved in menstrual cycle
60
Order of events in the menstrual cycle
The uterus lining breaks down, woman has period
The layer builds up until ovulation (day 14), an egg is released from the ovary, to uterus through fallopian tube
If a fertilised egg has not been embedded in the lining after 28 days, it breaks down and cycle continues
61
What does FSH do
- Stimulates maturation of an egg in the ovary within a follicle
- Produced in pituitary gland
- Stimulates ovaries to produce oestrogen
62
What does oestrogen do
Produced in the ovaries
Secreted because of FSH
Stimulates production of LH, and inhibits the production of more FSH
63
What does Luteinising Hormone do
Produced in pituitary gland
Produced as a result of oestrogen
Its release results in ovulation
64
What does progesterone do
Produced in ovaries and secreted from the egg follicle
Maintains uterus lining and supports a pregnancy if the egg is fertilised
Inhibits release of FSH and LH
65
What are the hormonal methods of contraception
- The pill
- Patch
- Implant
- Injection
- Plastic intrauterine device
66
What hormones does the contraceptive patch contain
Oestrogen and progesterone
67
What hormones does the contraceptive implant contain
Continuous supply of progesterone
68
What hormone does the contraceptive injection contain
Progesterone
69
What hormone does the IUD release
Progesterone
70
What are the non hormonal methods of contraception
- Barrier methods
- Copper IUD kills sperm
- Removing fallopian tubes or sperm duct
- Abstaining
71
How is IVF carried out
Mother is given FSH and LH to encourage the maturation in eggs
These are extracted and fertilised in lab using sperm
The fertilised eggs develop into embryos and then one or two are inserted in the uterus
72
What does thyroxine do
Regulates metabolic rate (how quickly reactions occur)
Meaning its important in growth and development
73
Where is thyroxine released and how is it stimulates
Released by thyroid gland
Stimulated by thyroid stimulating hormone
74
Describe positive phototropism
When plants grow towards the light source
- Plant is exposed to light on one side
- Auxin moves to shaded side
- Auxin stimulates cells to grow more here
- Meaning the shoot bends towards the light
- The plant receives more light so photosynthesis can occur at a faster rate
75
Explain negative geotropism in shoots
Plants grow away from gravity
- If a plant is horizontal
- Auxin moves to lower side
- The cells of the shoot grow more on the side with most auxin so it stimulates cells to grow here
- The shoot will bend and grow away from the ground
76
Why is negative geotropism beneficial for most shoots
- Light levels are likely to be higher further away from the ground
77
Explain positive geotropism in the roots
- Auxin moves to lower side
- Cells of the root grow more on the side with less auxin, so it stimulates cells to grow on the upper side
- The root will bend and grow downwards
78
Explain positive geotropism in the roots
- Auxin moves to lower side
- Cells of the root grow more on the side with less auxin, so it stimulates cells to grow on the upper side
- The root will bend and grow downwards
79
Why is positive geotropism beneficial in roots
Increased levels of water and nutrients lower down
It provides stability for the plant
80
Why are gibberellins important
To stimulate seed germination
81
Why is ethene important
For cell division, and ripening of fruits
82
Why would scientists use auxin
Weed killers
Rooting powders
Promote growth in tissue culture
83
Why would scientists use gibberellins
Ending seed dormancy
Promoting flowering
Increasing fruit size
