B5 - Homeostasis and Response Flashcards
(194 cards)
1
Q
What is homeostasis?
A
The body maintaining a stable environment for optimum conditions for enzyme and cellular functions.
2
Q
What 3 conditions are maintained by homeostasis?
A
Water content.
Body temperature.
Blood glucose levels.
3
Q
Why are control systems needed?
A
To ensure conditions in your body remain stable even when the external environment changes.
4
Q
What 3 things are needed in control systems?
A
Receptor
Co-ordination center
Effector
5
Q
What organ helps to control body temperature?
A
The liver controls metabolic reactions so the amount of heat energy transferred to the environment is controlled.
6
Q
What is negative feedback?
A
Opposing the change.
7
Q
What is positive feedback?
A
Acts to amplify or encourage the change e.g. when a mother breastfeeds her child, the more milk she produces.
8
Q
Why is feedback important in control systems?
A
To make adjustments and maintain optimum conditions in an organism.
9
Q
What is the temperature regulation center in the brain called?
A
Hypothalamus.
10
Q
What are the body’s responses to an increase in temperature?
A
Sweating - evaporation of water takes away heat energy from the surface of the skin.
Vasodilation meaning more heat is radiated away.
11
Q
What are the body’s responses to a decrease in temperature?
A
Muscles contract rapidly - respiration allows muscles to contract. Respiration is an exothermic process so energy released raises body temperature.
Vasoconstriction - less heat radiated away.
Sweating stops.
12
Q
What is thermoregulation?
A
The control of body temperature.
13
Q
What temperature do enzymes work best at?
A
37 degrees celcius.
14
Q
What is CNS?
A
Central Nervous System.
15
Q
What are neurones?
A
Cells that transmit electrical impulses around the nervous system.
16
Q
Which neurons carry electrical impulses from the receptors to the CNS?
A
Sensory neurons.
17
Q
Which neurons carry electrical impulses from the CNS to the effectors?
A
Motor neurons.
18
Q
What is a relay neuron?
A
Sends information from one neuron to another.
19
Q
What is another term for neurons?
A
Nerve cells.
20
Q
What 3 things make up the nervous system?
A
Brain, spinal cord, neurons.
21
Q
What does the CNS consist of?
A
Brains and the spinal cord.
22
Q
What does the peripheral nervous system consist of?
A
Neurons.
23
Q
What are receptors?
A
Groups of specialised cells that detect changes in the environment, called stimuli, and turn them into electrical impulses.
24
Q
Where are receptors often located?
A
In the sense organs - skin, eye and ear.
25
What are effectors?
Produce a response.
26
What is a coordination center?
Obtain information from the receptors.
27
What is the name of the microscopic gap between neurons?
Synapses.
28
How are electrical impulses transmitted?
A chemical (a neurotransmitter) diffuses across the synapse to stimulate a second neurone.
29
Define a reflex action?
A rapid, automatic response to a stimulus.
30
Give 4 examples of reflexes performed by the human body and why this reflex is important.
Blink reflex - prevents the eye from getting damaged.
Knee reflex - walking / running.
Ankle reflex - walking / running.
Pupil reflex - prevents damage from bright light.
31
What is an advantage of the spinal cord being a coordination center?
Reactions are quicker as shorter pathway between sensory neurons and spinal cord.
32
What are the steps of a response being carried out by the body caused by a stimulus?
1. The receptors convert the stimulus into an electrical impulse.
2. This electrical impulse travels along sensory neurons to the CNS.
3. The CNS coordinates a response.
4. An electrical impulse is sent along motor neurons to the effector which carries out the response.
33
What is the difference between a reflex pathway and a conscious pathway?
Within a reflex pathway, the co-ordination center is a relay neuron found in the spinal cord or unconscious part of the brain.
Within a conscious pathway, the co-ordination center is in the conscious part of the brain.
34
What is the order of events in the reflex arc?
Stimulus -> receptors -> sensory neuron -> relay neuron -> motor neuron -> effector -> response
35
What is accomodation?
The alteration of the lens' shape in order to focus on near or distant objects.
36
What are the two main functions of all the structures found within the eye?
Focusing on near or distant objects.
Adapting to light.
37
What is the function of the retina?
Where light is focused.
Contains photoreceptive cells which detect colour and light intensity.
38
What is the function of the pupil?
The hole that allows light to enter the eye.
39
What is the function of the optic nerve?
Carries electrical impulses from the eye to the brain.
40
What is the function of the sclera?
The tough supporting wall of the eye.
41
What is the function of the cornea?
Transparent outer layer found at the front of the eye. Refracts light into the eye.
42
What is the function of the lens?
Focuses light onto the retina.
43
What is the function of the ciliary muscles?
Muscles connected to the lens by the suspensory ligaments.
Control the shape of the lens.
44
What is the function of the suspensory ligaments?
Connect the ciliary muscles to the lens and holds the lens in place.
Control the shape of the lens.
45
What happens to the ciliary muscles and suspensory ligaments when the object is near?
Ciliary muscles contract.
Suspensory ligaments slacken.
46
What is the shape of the lens when an object is near?
Curved, fat.
47
What is the muscles tension on the lens when an object is near?
Low.
48
What is the effect on the refraction of the light when the object is near?
Refracts light more.
49
What happens to the ciliary muscles and suspensory ligaments when the object is far?
Ciliary muscle relaxes.
Ligaments pull on lens.
50
What is the shape of the lens when an object is far away?
Flat, thin.
51
What is the muscle tension on the lens when an object is far?
High.
52
What is the effect on the refraction of the light when the object is far?
Refracts light less.
53
What is the action of the circular and radial muscles in dim light? (the iris)
Circular muscles relax.
Radial muscles contract.
54
What is the action of the circular and radial muscles in bright light? (the iris)
Circular muscles contract.
Radial muscles relax.
55
Why is the constriction of the pupil important?
It avoids retinal damage.
56
Why is the dilation of the pupil important?
Allows more light to enter the eye.
57
What is myopia?
Short-sightedness. Usually occurs when lens is too curved and as a result light is focused in front of the retina.
58
How can myopia be treated?
Use of a concave lens, which spreads out light rays so they can be focused on the retina.
59
What is hyperopia?
Long-sightedness. Occurs when the lens is too flat and light is not refracted enough so light is focused behind the retina.
60
How can hyperopia be treated?
With a convex lens. Which brings the light rays together so they can be focused on the retina.
61
What are the two types of contact lens?
Hard - rigid material, long-lasting, must be kept sterile.
Soft - flexible material, lasts a shorter amount of time, more comfortable.
62
What is laser eye surgery?
Use of lasers to fix visual defects in adults.
63
What is done in laser eye surgery to treat myopia?
Lasers reduce the thickness of the cornea so light is refracted less strongly.
64
What is done in laser eye surgery to treat hyperopia?
Alters the curvature of the cornea so light is refracted more strongly.
65
What are the two different methods of using a replacement lenses to fix visual defects?
A replacement lens can either be implanted into the eye along with the natural lens.
Or replace the lens altogether.
66
What are the risks of lens replacement?
Retinal damage, cataracts and infection.
67
How is temperature monitored by the body?
Thermoregulatory center has receptors sensitive to blood temperature.
Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory center.
68
What is a tropism?
The response of a plant to a specific stimulus.
69
What is phototropism?
Response of a plants shoot or root to light.
70
What is gravitropism?
Response of a plants shoot or root to gravity.
71
What is auxin?
A hormone which controls the growth of a plant's shoot and roots. When auxin is unevenly distributed in a growing plant the rate of growth will be unequal.
72
What happens when an auxin is unevenly distributed in a growing plant?
The rate of growth will be unequal.
73
How do plant shoots show positive phototropism?
One side of the shoot is in the light, causing auxin to move to the shaded side. Cells are stimulated to grow at the shaded side. The shoot bends towards the light.
74
How do plants show negative gravitropism?
Auxin accumulates in the lower side due to gravity.
Cells on the lower side grow more, causing the shoot to bend away from the direction of gravity.
75
How do plant roots show positive gravitropism?
Auxin accumulates in the lower side causing cells to grow less. The root bends in the direction of gravity.
76
How do plants benefit from positive gravitropism?
More water and nutrients are available to plant roots.
77
How do plants benefit from positive phototropism?
Photosynthesis occurs at a faster rate.
78
What are gibberellins?
A type of plant hormone involved in seed germination.
79
What is ethene?
A type of plant hormone involved in cell division and ripening.
80
What are 3 uses of auxins?
- Weed killers - cause cells to grow at a rapid rate causing it to die.
- Rooting powder - causes new plants to grow very quickly.
- Tissue culture - promotes growth of roots and shoots.
81
State the use of ethene.
Control of food ripening in the food industry - allows them to be ripened just before they are sold.
82
3 uses of gibberellins.
- Termination of seed dormancy
- Promotion of flowering
- Increase of fruit size
83
How is temperature monitored by the body?
Thermoregulatory center has receptors sensitive to blood temperature.
Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory center.
84
Why are reflex actions important?
Aid survival by preventing harm to the body.
85
What is the function of the cerebral cortex?
Controls consciousness, intelligence, memory and language.
86
What is the function of the cerebellum?
Controls muscular co-ordination.
87
What is the function of the medulla?
Controls unconscious activities e.g. breathing and heart rate.
88
Why is investigation and treatment of the brain difficult (4)?
- Brain is complex and delicate.
- Brain is easily damaged.
- Certain membranes prevent drugs from reaching the brain.
- The exact function of each part of the brain is not know so surgery is difficult.
89
What 3 methods are used by scientists to determine brain function?
Studying patients with brain damage.
Electrical stimulation of the brain.
MRI scans.
90
What stimuli are the receptors of the eye sensitive to?
Light intensity and colour.
91
What is the function of the nervous system?
Allows the body to react to it's surroundings and coordinate an appropriate response.
92
What is the function of the iris?
Muscles that controls the size of the pupil by contracting or relaxing. Allowing the eye to adjust to bright and dim lighting.
93
What 2 types of responses are used in body control systems?
Nervous and chemical.
94
What 2 things can the hypothalamus control?
Body temperature.
Water levels in the blood.
95
What is the function of the pituitary gland?
Produces many different chemicals (hormones) which help control body systems.
96
What is the brain stem?
The primitive part and controls basic functions that keep you alive.
97
Is the cerebral cortex found in every animals brain?
No, only found in highly intelligent animals.
98
What are insulin and glucagon?
Hormones produced by the pancreas that regulate glucose levels in the blood.
99
What is the difference in structure between glucose and glycogen?
Glucose is a simple sugar which is a monomer, glycogen is a polymer of glucose and is a storage molecule found in animals.
100
What response does the pancreas perform when blood glucose is too high?
Pancreas secretes insulin into the blood, insulin binds to liver and muscle cells, causing excess glucose to be converted into glycogen and stored.
101
What response does the pancreas perform when blood glucose is too low?
Glucagon is secreted into the blood.
Glucagon binds to liver cells.
Causing glycogen to be converted into glucose and released into the blood.
102
What is the effect on the liver and muscles when glucose levels are too high?
Glucose in the blood moves into the liver and muscles, where it is converted into glycogen for storage.
103
What is the effect on the liver and muscles when glucose levels are too low?
Glucose is not converted into glycogen by the liver and muscles.
The liver converts glycogen into glucose.
104
Why is glucose converted into glycogen?
Glucose would cause lots of water to travel into the cells which could result in them dying however glycogen doesn't effect osmosis.
105
How does type 1 diabetes occur?
When the body doesn't produce insulin or enough insulin.
106
How does type 1 diabetes effect your physical appearance?
No stores of glycogen - meaning you are underweight.
107
How is type 1 diabetes treated?
Insulin injections before meals.
Limiting carbohydrate intake.
Pancreas and pancreatic cell transplants.
108
What 2 factors effect how much insulin a person with type 1 should take?
1. How much they have eaten - more insulin needs to be injected.
2. How much they have exercised - less insulin needed to be injected (as muscles take in more glucose when exercising).
109
What is type 2 diabetes?
When the body cells stop responding to insulin, so the cells won't take glucose in from the blood stream, leading to an uncontrolled glucose concentration.
110
Why does type 1 diabetes lead to weight loss?
The lack of a sufficient supply of insulin prevents glucose from going into cells to release energy therefore the body starts using fat and muscle stores instead.
111
What are the factors that could cause type 2 diabetes?
Age and obesity.
112
How is type 2 treated?
- losing weight
- exercising more
- controlled diet
- drugs which increase insulin effectiveness
113
Why is blood glucose concentration part of the negative feedback loop?
The action of the secreted hormone will bring blood glucose levels back to a normal concentration. Opposes the change.
114
What are 4 symptoms of type 1?
Frequent urination
Thirst
Tiredness
Weight loss
115
What age group is type 1 diagnosed at?
Childhood - teenagers
116
What age range does type 2 usually become diagnosed?
Over 40
117
What do MRI scans enable scientists to do?
To link the loss of a certain function with a particular region of the brain.
118
Where are amino acids broken down?
Liver
119
Why is a decrease in body temperature beneficial to animals during hibernation?
Loses less energy.
Body energy store lasts longer.
120
Why does an animal have a higher body temperature when it is active?
Activity requires energy from respiration.
Respiration releases heat which increases body temperature.
121
Why does the dilation of blood vessels in the skin decrease body temperature?
More blood flow near the surface of the skin.
More heat is lost.
Cools blood which cools the body.
122
What is the name of the coordination system involving hormones?
Endocrine system
123
What type of organ secretes hormones?
Glands
124
What gland controls many other glands in the body?
Pituitary gland
125
Why is the pituitary gland referred to as the master gland?
Secretes a wide range of hormones, some of which stimulate other endocrine glands.
126
4 roles of pituitary gland.
Secretes:
- growth hormones
Stimulates:
- thyroid gland
- ovulation and oestrogen
- production of sperm and testosterone
127
What is the role of the thyroid gland?
Secretes hormone thyroxine - controls metabolism, heart rate and temperature.
128
What is the role of the pancreas?
Secretes insulin - controls blood glucose levels.
129
What is the role of the adrenal gland?
Secretes adrenaline - fight or flight response.
130
What is the role of the ovaries?
Secretes oestrogen - which co-ordinates the menstrual cycle and controls female sexual characteristics.
131
What is the role of the testes?
Secretes testosterone - coordinates sperm and male characteristics.
132
Where is ADH secreted?
Pituitary gland.
133
In what ways is water lost from the body?
Sweating
Urine (some reabsorbed by kidney)
Exhalation
134
In what ways are ions lost from the body?
Sweating
Urine (some reabsorbed by kidney)
135
How are excess amino acids excreted from the body?
Deaminated in liver to form ammonia.
Ammonia converted into urea
Urea excreted via sweat and urine.
136
How do kidneys maintain the balance of water and other substances in the body?
Filter blood to remove urea.
Reabsorb useful molecules e.g. glucose ions water.
137
What does ADH control?
The water content of blood.
138
How does the body respond to too little water in blood?
Releases more ADH.
More water absorbed by kidneys.
Less water lost in urine.
Blood water level returns to normal.
139
How does the body respond to too much water in blood?
Releases less ADH.
Less water absorbed by kidneys.
More water lost in urine.
Blood water level returns to normal.
140
What are the effects of adrenaline?
Increase in heart and breathing rate.
Dilation of pupils
Glycogen converted to glucose.
Blood diverted to muscles.
141
What is thyroxine’s releases stimulated by?
TSH - thyroxine stimulating hormone released by pituitary gland.
142
Why is kidney failure dangerous?
Unable to filter blood properly leads to:
Build up of toxic chemicals - urea
An uncontrolled ion and water balance
143
State 2 ways of treating kidney failure.
Dialysis
Transplant
144
What is the function of reproductive hormones during puberty?
Males - sexual characteristics
Females - sexual characteristics and maturation of eggs.
145
Main male reproductive hormone.
Testosterone
146
Main female reproductive hormone.
Oestrogen
147
Describe events of menstrual cycle.
Uterus lining thickens and eggs mature in ovaries
An egg is released, lining remains thick
If egg is fertilised pregnancy may occur, if not both egg and uterus lining are shed during mensturation.
148
What is ovulation?
Release of a mature egg from the ovaries - every 28 days
149
Name 4 main hormones in the menstrual cycle.
Oestrogen
Progesterone
FSH
LH
150
What is the role of FSH?
Secreted by pituitary gland.
Controls the maturation of eggs.
Triggers the production of oestrogen.
151
What is the role of oestrogen?
Causes regrowth of uterus lining.
Triggers production of LH.
Stops release of more FSH.
152
What is the role of LH?
Triggers ovulation.
153
What is the role of progesterone?
Secreted from follicle of ovary.
Sustains uterus lining and inhibits FSH and LH.
154
What is adrenaline?
Hormone secreted in the adrenal gland in times of stress.
155
How is the release of thyroxine controlled by negative feedback?
Receptors detect low levels in the blood.
Pituitary gland releases more TSH.
More thyroxine produced by Thyroid gland.
Blood thyroxine returns to normal.
156
Name 4 hormones released in the menstrual cycle.
FSH (follicle stimulating hormone)
LH (luteinizing hormone)
Oestrogen
Progesterone
157
What gland is FSH and LH released from?
Pituitary gland.
158
What gland is oestrogen and progesterone released from?
Ovaries
159
What is the function of FSH?
Causes egg cell to mature in ovaries. Stimulates ovaries to release oestrogen.
160
What is the function of LH?
Causes mature egg cell to be released. Stimulates release of progesterone.
161
What is the function of progesterone?
Maintains the uterus lining.
162
What is the function of oestrogen?
Causes uterus lining to thicken. Inhibits FSH and promotes LH.
163
What does the pill contain?
Oestrogen and/or progesterone.
164
How does the pill prevent pregnancy?
Prevents egg cell maturing and being released.
165
What are the cons of the pill?
Doesn’t protect against STD’s.
Increased risk of breast cancer.
Headaches and nausea.
166
What is a intrauterine device?
T-shaped device inserted into uterus.
167
How does a intrauterine device prevent pregnancy?
Kills sperm
Prevents implantation of a fertilised egg cell.
168
What does the plastic version of a intrauterine device do?
Release progesterone.
169
What is the only contraceptive method that protects against STD’s?
Condoms
170
What are the cons of condoms?
Can let semen through if damaged.
171
What are diaphragms?
Prevents sperm passing through the cervix.
172
What do diaphragms have to be used with?
Spermicide
173
What does surgical contraception involve?
Cutting or tying the fallopian tubes or sperm ducts.
174
What are the cons of tying the fallopian tubes or sperm ducts?
Chance they will re-join naturally.
Doesn’t prevent against STD’s.
175
How long is the menstrual cycle?
Around 28 days.
176
When is a woman most fertile?
Around ovulation (day14). Fertilisation must take place in the fallopian tube.
177
What is ovulation?
When an egg cell is released from the ovaries.
178
What is a natural contraceptive method?
Avoiding intercourse when the egg may be in the fallopian tubes. (rhythm method)
179
What are the cons of the rhythm method?
Unreliable.
Doesn’t protect against STD’s.
180
What can women take when they have low levels of hormones?
FSH and LH to stimulate ovulation.
181
What are the pros of taking hormones to stimulate ovulation?
Help people get pregnant.
Non-invasive in tablet form.
182
What are the cons of taking hormones to stimulate ovulation?
Doesn’t always work - might need to be repeated - expensive.
Too many eggs released results in multiple pregnancies.
183
Which system are your kidney’s part of?
Excretory system / urinary system
184
What is the function of the kidneys?
Control water balance.
Remove toxic substances.
Control balance of salts.
185
Where is ADH secreted?
Pituitary gland.
186
What does ADH actually do to the kidney tubules that allows it to absorb more water?
It increases the permeability of the tubules.
187
What is kidney dialysis?
Use of specialist machinery to carry out function of the kidneys.
188
What does dialysis fluid contain?
Same concentration of ions and glucose as the blood, so only waste molecules are lost from the blood through osmosis.
189
What is urea?
A waste product.
Made in liver through deamination.
190
Why is water regulation important?
Cells could swell and burst if water levels are too high.
Shrink if water levels are too low.
191
Explain how filtration in the kidneys work.
Tubules absorb anything small e.g. water, glucose, amino acids, and urea.
Doesn’t absorb large molecules.
192
What is selective reabsorbtion?
When all of glucose, some water (and useful molecules) are aborsbed back into blood)
193
What is the hypothalamus job in water regulation?
Detects water levels in blood stream.
194
What type of system regulates water content levels?
Negative feedback system
