Homeostasis and Response Flashcards
1
Q
what is homeostasis?
A
The maintenance of steady conditions. The ability of the body to maintain a constant internal environment
2
Q
why is homeostasis important? give examples
A
it maintains optimal conditions for enzyme action throughout the body, as well as all cell functions e.g. blood glucose concentration,
body temperature,
water levels
3
Q
what 3 things do all control systems include?
A
- cells called receptors, which detect stimuli (changes in the environment)
- coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors.
- effectors, muscles or glands, which bring about responses which restore optimum levels.
4
Q
what is the function of the nervous system?
A
to enable humans to react to their surroundings and to coordinate their behaviour
5
Q
what are the important components of the nervous system?
A
- the central nervous system (CNS) – the brain and spinal cord
- the peripheral nervous system – nerve cells that carry information to or from the CNS
- nerve cells, effectors, receptors
6
Q
how does information pass through the nervous system?
A
- in the form of electrical signals, called nerve impulses
- these nerve impulses pass along cells called neurones (or nerve cells)
- nerves are made up of bundles of neurones (nerve cells)
7
Q
what happens in a reflex action?
A
information follows the pathway of:
1. stimulus
2. receptor
3. sensory neurone
4. relay neurone
5. motor neurone
6. effector
7. response
this is a reflex arc
8
Q
what is a reflex action?
A
Automatic and rapid response to a stimulus.
9
Q
why is a reflex action important?
A
it minimises any damage to the body from potentially harmful conditions, such as touching something hot
10
Q
what does a receptor do?
A
(in the skin) detects a stimulus (e.g. change in temperature)
11
Q
what does a sensory neurone do?
A
send electrical impulses to relay neurone
12
Q
what does a relay neurone do?
A
(located in the spinal cord) they connect sensory neurones to motor neurones
13
Q
what does a motor neurone do?
A
sends electrical impulses to an effector
14
Q
what does an effector do?
A
produces a response (e.g. contracts to move hand away)
15
Q
what does a synapse do?
A
tiny gap at the junction between two nerve cells, which nerve signals must cross by transmitting the elctrical impulse through the release of neurotransmitters
16
Q
how are neurones adapted?
A
- A long fibre (axon) which is insulated by a fatty (myelin) sheath. They are long so they can carry messages up and down the body.
- Tiny branches (dendrons) which branch further as dendrites at each end. These receive incoming impulses from other neurones.
17
Q
what is the function of the brain?
A
controls complex behaviour/ vital functions are coordinated
18
Q
how is the brain structured?
A
- cerebrum/ cerebral cortex- outer layer- cerebral cortex is the outer layer of the outer layer
- cerebellum- circular part under cerebral cortex at the back of the head
- medulla is connected to the spinal cord
19
Q
function of the cerebrum
A
- controls intelligence, personality, conscious thought and high-level functions, such as language and verbal memory
- split into two hemispheres and is highly folded
20
Q
cerebellum function
A
controls balance, co-ordination of movement and muscular activity
21
Q
medulla function
A
controls unconscious activities such as heart rate and breathing rate
22
Q
hypothalamus function
A
the regulating centre for temperature and water balance within the body
23
Q
how have neuroscientists been able to map regions of the brain to particular functions?
A
- studying patients with brain damage
- electrically stimulating different parts of the brain
- using MRI scanning techniques
24
Q
eye function
A
a sense organ containing receptors sensitive to light intensity and colour
25
structure of eye
* cornea- outer layer on pupil/ iris
* iris
* lens- over behind iris
* retina- layer under sclera
* optic nerve- connected to brain
* sclera- outer layer
26
function of cornea
Refracts light - bends it as it enters the eye
27
function of iris
Controls how much light enters the pupil
28
function of lens
Further refracts light to focus it onto the retina
29
function of retina
Contains the light receptors
30
function of optic nerve
Carries impulses between the eye and the brain
31
function of sclera
Tough white outer layer of the eye. It helps protect the eye from injury
32
what is accommodation?
the process of changing the shape of the lens to focus on near or distant objects
33
how is accommodation carried out?
* To focus on a near object – the lens becomes thicker, this allows the light rays to refract (bend) more strongly.
* To focus on a distant object – the lens is pulled thin, this allows the light rays to refract slightly.
34
what is myopia?
* short-sightedness
* can see near objects clearly, but cannot focus properly on distant objects
* eyeball being elongated - so that the distance between the lens and the retina is too great
* the lens being too thick and curved - so that light is focused in front of the retina
35
what is hyperopia?
* long-sightedness
* can see distant objects clearly, but they cannot focus properly on near objects
* the eyeball being too short - so the distance between the lens and retina is too small
* a loss of elasticity in the lens - meaning it cannot become thick enough to focus (which is often age-related)
36
how is myopia treated?
by placing a concave (curves inwards) lens in front of the eye
37
concave lens used for myopia ray diagrams
* without concave lens- two arrows going straight through to the lens but then crossing over and landing in two places on the retina
* with concave lens- two arrows going straight into concave lens, pointing outwards slightly into the lens, then pointing together at the retina
38
how is hyperopia treated?
by putting a convex (curves outwards) lens in front of the eye
39
convex lens used for hyperopia ray diagrams
* without convex lens- two arrows going in straight to the lens, then pointing together but going past the retina
* with convex lens- two arrows go in straight to the convex lens, point together slightly into the lens, point together completely at the retina
40
how is the body's temperature monitored and controlled?
The human body maintains the temperature that
enzymes work best, which is around 37°C. This process is controlled by the thermoregulatory centre, which is contained in the hypothalamus in the brain, and it contains receptors sensitive to the temperature of the blood. The skin also has temperature receptors and sends nervous impulses back to the thermoregulatory centre.
41
what happens when we get too cold?
* Skeletal muscles contract rapidly and we shiver.
* These contractions need energy from respiration, and some of this is released as heat.
* Blood vessels, which lead to the skin capillaries, become narrower - they constrict – which allows less blood to flow through the skin and conserve the core body temperature. This is called vasoconstriction
* nerve impulses are sent to the hair erector muscles which contract. This raises the skin hairs and traps a layer of insulating air next to the skin.
42
what happens in vasoconstriction?
* arterioles get narrower
* blood flow in skin capillaries decreases
* less heat is lost from skin
* heat increases
43
what happens when we get too hot?
* Sweat glands in the skin release more sweat.
* The sweat evaporates, transferring heat energy from the skin to the environment.
* Blood vessels leading to the skin capillaries become wider - they dilate - allowing more blood to flow through the skin, and more heat to be lost to the environment. This is called
vasodilation
* Skin hairs lie flat
44
what happens in vasodilation?
* arterioles get wider
* the blood flow in skin capillaries increases
* more heat is lost from the skin
* heat decreases
45
describe the endocrine system
The endocrine system secretes hormones into the bloodstream from glands throughout the body. to control processes. Hormones produce an effect on specific target organs in the body.
46
what are hormones?
chemical substances produced by endocrine glands that release them into the blood stream and carried to a target organ to produce an effect
47
name the 6 organs in the endocrine system
* pituitary gland
* thyroid gland
* pancreas
* adrenal glands
* ovary
* testis
48
describe the location of the pituitary gland
small circle in the centre/ front of the brain under the cerebrum
49
describe the location of the thyroid gland
just under the neck, around the windpipe thing
50
describe the location of the adrenal glands
just above each kidney
51
describe the location of the pancreas
thin and long (horizontally) and around the kidneys
52
what is the role of ADH?
Controlling the water content of the blood
53
what is the role of adrenaline?
Preparation for 'fight or flight'
54
what is the role of insulin?
Controlling blood glucose levels
55
what does the pancreas do?
regulates blood glucose (sugar) concentration using two main hormones: insulin (lowers blood sugar) and glycogen (increases blood sugar)
56
how does the body respond when blood glucose concentration is too high?
* pancreas produces insulin
* it travels in the blood to the liver
* insulin allows glucose to be absorbed by the liver from the blood
* liver cells convert glucose to glycogen
* blood glucose levels fall
57
how does the body respond when blood glucose concentration is too low?
* pancreas releases glucagon hormone
* it travels in the blood to the liver
* liver converts glycogen to glucose
* glucose released into blood
* blood glucose levels rise
58
what is type 1 diabetes?
disorder in which the pancreas fails to produce enough insulin
59
what is type 2 diabetes?
the person's body cells no longer respond to insulin produced by the pancreas
60
how is type 1 diabetes treated?
injecting insulin to control blood glucose levels
61
how is type 2 diabetes treated?
* carbohydrate controlled diet
* excersise
62
how does glucagon interact with insulin to control blood glucose levels?
the two hormones counterbalance each other to stabilize blood glucose: the pancreas releases more insulin when sugar levels are too high and more glucagon when sugar levels are too low
63
how is water, ions and urea lost from the body?
lost from the skin as they are contained in sweat
64
what are the consequences of losing or gaining too much water for body cells?
* they do not function efficiently
* if the water concentration is too high outside, water enters the cell by
osmosis and they may burst
* if the water concentration is too low outside compared with the inside of the cells, water will leave by osmosis and the cells may shrivel
65
what does protein digestion lead to?
excess amino acids inside the body which are transported to the liver from the small intestine. The liver controls the amino acid concentration in the body, as excess amino acids which need to be excreted are discharged as waste safely.
66
how do kidneys produce urine?
any water and dissolved substances (salts/ions, urea) left over pass into the urine, which collects in the renal pelvis and are removed
67
what effect does ADH have on the kidney tubules?
causes them to become more permeable (substance which allows fluids or gases to pass through it) which allows more water to be reabsorbed back into the blood during selective reabsorption
68
how is the water level in the body controlled by ADH?
it makes the kidney tubules more permeable so more water can leave the kidney tubule to be reabsorbed back into the blood during selective reabsorption
69
how can kidney failure be treated?
by organ transplant or dialysis
70
how can kidney failure be treated by dialysis?
* Unfiltered blood that is high in urea is taken from a blood vessel in the arm
* it's mixed with blood thinners or an anti-coagulant to prevent clotting, and pumped into the dialysis machine
* inside the machine the blood and dialysis fluid are separated by a partially permeable membrane the blood flows in the opposite direction to dialysis fluid, allowing exchange to occur between the two where a concentration gradient exists
* If the patient's blood is too low in ions, they will diffuse from the dialysis fluid into the blood, restoring the ideal level in the blood
* If the patient's blood is too high in ions, the excess ions will diffuse from the blood to the dialysis fluid.
71
what happens in only male puberty?
* voice breaks
* hair grows on face and body
* body gets more muscular
* testes start to produce sperm cells
72
what happens in only female puberty?
* voice deepens gradually
* hips get wider
* breasts develop
* ovaries start to release egg cells - menstruation starts
73
what happens in male AND female puberty?
* pubic hair grows
* underarm hair grows
* sexual organs grow and develop
74
what does FSH do and where is it made?
* Pituitary gland
* Causes an egg to mature in an ovary. Stimulates the ovaries to release oestrogen
75
what does oestrogen do and where is it made?
* Ovaries
* Stops FSH being produced (so that only one egg matures in a cycle). Repairs, thickens and maintains the uterus lining. Stimulates the pituitary gland to release LH.
76
what does LH do and where is it made?
* Pituitary gland
* Triggers ovulation (the release of a mature egg)
77
what does progesterone do and where is it made?
* Ovaries
* Maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.
78
how do hormone levels change during the menstrual cycle?
* Days 1 to 12 – oestrogen gradually increases and peaks approximately on the 12th day.
* Progesterone, LH and FSH stay approximately at the same levels and begin to increase slightly from around day 12.
* FSH and LH patterns are very similar and peak during ovulation at approximately 14 days during this cycle. They drop sharply on day 15 and stay constant until day 28.
* Oestrogen drops during days 13 and 14, and progesterone continues to gradually increase until about day 21, when it slowly begins to decrease again.
* Oestrogen mirrors this shape and also has a second lower peak at about day 21.
79
how do different hormones interact to control the menstrual cycle?
* pituitary gland makes FSH which matures an egg in the ovary
* as it matures, ovary produces oestrogen
* this causes growth and repair of uterus wall lining and stops FSH
* when oestrogen gets high enough, pituitary gland makes a surge in LH cuasing ovulation (egg is released day 14)
* ovary makes progesterone, stopping FSH and LH (negative feedback)
* progesterone maintains uterus lining
80
how can fertility be controlled by hormonal methods of contraception?
* The oral contraceptive, which is known as the pill, contains oestrogen or progesterone.
* These hormones inhibit the production of FSH, and eggs cannot mature.
81
how can fertility be controlled by non-hormonal methods of contraception?
* Physical barrier methods such as condoms and diaphragms, which prevent the sperm reaching an egg
* Intrauterine devices (IUD) also known as a coil, prevent the implantation of an embryo or release of a hormone
* Spermicidal agents which kill or disable sperm
* Abstaining from intercourse when an egg may be in the oviduct
* Surgical methods of male and female sterilisation. An example is a vasectomy, where the sperm ducts are cut and tied.
82
how can hormones be used to treat infertility?
* Some women have difficulty becoming pregnant because they don't produce enough FSH to allow their eggs to mature.
* Fertility drugs contain FSH and LH, which stimulate eggs to mature in the ovary.
* Fertility treatments increase a woman's chance of becoming pregnant, although the treatment may not always work.
83
4 steps of IVF
1. IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs.
2. The eggs are collected from the mother and fertilised by sperm from the father in a dish in the laboratory.
3. The fertilised eggs develop into embryos.
4. At the stage when they are tiny balls of cells one or two embryos are inserted into the mother's uterus (womb)
84
3 advantages of IVF
* It allows people to have babies of their own, who otherwise can't due to a variety of reasons.
* It has a safe track record and has been used since 1978. The embryos can be screened for genetic diseases, which is important for families that already have an affected child. Only unaffected embryos are used.
* Unused eggs can be used for research or donated to other couples.
85
7 disadvantages of IVF
* There are side effects form the drugs used, such as hot flushes and severe headaches.
* There is a possibility of multiple births, which is dangerous for mother and babies.
* Ovarian hyper-stimulation syndrome (OHS), when too many eggs develop in the ovaries.
* It is very emotionally and physically stressful.
* The success rates are not high.
* Ethical concern- concerned that couples may want 'designer babies' with 'desirable' qualities, so may only want certain fertilised eggs
* Ethical concern- embryos that are not used may be destroyed. Some people consider embryos to be new lives and view their destruction as unethical.
86
what is negative feedback?
A mechanism where changes to conditions cause an action to reverse the change, to keep conditions stable.
87
explain the roles of thyroxine as a negative feedback system
* Low thyroxine levels in the bloodstream stimulate the hypothalamus to release TRH and this causes the pituitary to release TSH so the thyroid releases more thyroxine. So blood levels return to normal.
* Normal thyroxine levels in the bloodstream inhibit TRH release from the hypothalamus and this inhibits the release of TSH from the pituitary, so normal blood levels are maintained.
88
3 functions of thyroxine and where it's produced
* stimulates the basal metabolic rate
* controls the speed at which oxygen and food products react to release energy for the body to use
* plays an important role in growth and development
* (made in the thyroid gland)
89
function of adrenaline and where its produced
* produced by the adrenal glands in times of fear or stress
* increases the heart rate
* boosts the delivery of oxygen and glucose to the brain and muscles
* this prepares the body for 'flight or fight'
