Homeostasis and Response Flashcards
1
Q
Why do organisms need to respond to stimuli (changes in environment)?
A
In order to survive
2
Q
Why don’t single-called organisms have nervous and hormonal communication systems whereas multicellular organism do?
A
Can just respond to its environment - cells of multicellular organisms need to communicate with each other first
3
Q
What does the nervous system enable humans to do?
A
React to their surroundings and to coordinate their behaviour
4
Q
What does Central Nervous System (CNS) consist of in vertebrates?
A
Brain and spinal cord only
5
Q
In mammals, how is the CNS connected to the body?
A
By sensory neurones and motor neurones
6
Q
What are sensory neurones?
A
Neurones carry information as electrical impulses from receptors to CNS
7
Q
What are motor neurones?
A
Neurones that carry electrical impulses from CNS to effectors
8
Q
What are effectors?
A
All muscles and glands which respond to nervous impulses
9
Q
What is a synapse?
A
Connection between two neurones
10
Q
Explain how synapses connect neurones
A
- Nerve signal is transferred by chemicals which diffuse across gap
- These chemicals set off new electrical signal in next neurone
11
Q
What are receptors?
A
Cells that detect stimuli
12
Q
What do reflexes help to prevent?
A
Injury
13
Q
What are reflexes?
A
Rapid, automatic responses to certain stimuli that don’t involve conscious part of brain
14
Q
What is a reflex arc?
A
Passage of information in a reflex (from receptor to effector)
15
Q
Name the stages of a reflex arc
A
Stimulus → Receptor → Sensory Neurone → Central Nervous System → Motor Neurone → Effector → Response
16
Q
Where do neurones in a reflex arc go through?
A
Spinal cord or through unconscious part of brain
17
Q
When a stimulus (e.g. Painful bee sting) is detected by receptors, what happens?
A
Impulses are sent along a sensory neurone to CNS
18
Q
Why are reflexes quicker than normal responses?
A
Because you don’t have to think
19
Q
How do muscles respond to a nervous impulse?
A
Muscles contract
20
Q
How do glands respond to a nervous impulse?
A
Glands secrete hormones
21
Q
Why do conditions inside body need to be kept steady, even when external environment changes?
A
Because cells need right conditions in order to function properly including right conditions for enzyme action
22
Q
What is homeostasis?
A
Maintaining a stable internal environment, in response to
changes both internal and external conditions
23
Q
What do your automatic control systems use to keep the internal environment stable?
A
Uses a mechanism called negative feedback
24
Q
How does negative feedback work?
A
When the level of something (e.g. Water or temperature) gets too high or too low, your body uses negative
feedback to bring it back to normal
25
What are receptors in the eyes sensitive to?
Light
26
What are receptors in the ears sensitive to?
Sound and changes in position (enables us to keep our balance)
27
What are receptors in the tongue and nose sensitive to?
Chemicals (enables us to taste and smell)
28
What are receptors in the skin sensitive to? (4 things)
Touch, pressure, pain and temperature changes
29
What are receptors in the brain sensitive to?
Blood temperature and concentration of water in blood
30
What are receptors in the pancreas sensitive to?
Concentration of glucose in blood
31
What does the coordination centres include?
Brain, spiral cord and pancreas
32
Name 4 internal conditions that are controlled
1. Temperature
2. Water content of body
3. Ion content of body
4. Blood glucose levels
33
What are hormones?
Chemical molecules released directly into the blood
34
Hormones only affect...
particular cells in particular organs (target organs)
35
What do hormones control?
Things in organs and cells that need constant adjustment
36
Where are hormones produced and secreted from?
Endocrine glands
37
What makes up our endocrine system?
Glands
38
What does the pituitary gland do?
1. Produces many hormones that regulate the body
2. 'Master gland' - these hormones produced act on other glands, directing them to release hormones (that bring about change)
39
What does the adrenal gland do?
Produces adrenaline (which is used to prepare body for 'fight or flight')
40
Name 5 differences between nerves and hormones
Nerves:
1. Very FAST action
2. Act for a very SHORT TIME
3. Act on a very PRECISE AREA
4. Transported through NEURONES
5. ELECTRICAL messenger
Hormones:
1. SLOWER action
2. Act for a LONG TIME
3. Act in a more GENERAL way
4. Transported through BLOODSTREAM
5. CHEMICAL messenger
41
If response is really quick, what is it likely to be?
Nervous
42
If response lasts for a long time, what is it likely to be?
Hormonal
43
Why must the inside of the body kept around 37°C?
Optimum temperature for enzymes
44
What does the body have to balance (temperature wise)?
Balance amount of energy gained (e.g. Through respiration) and lost to keep core body temperature constant
45
What controls and monitors the body temperature?
Thermoregulatory centre in brain
46
What does the thermoregulatory centre contain?
Contains receptors that are sensitive to temperature of blood flowing through brain
47
Where does the thermoregulatory centre also receive impulses from?
Temperature receptors in skin, giving information about skin temperature
48
What do antagonistic effectors do?
Oppose each other's actions
49
Give an example of how antagonistic effectors work
Some effectors work antagonistically e.g. One effector heats and another cools = work at same time to achieve a very precise temperature
50
Why antagonistic effectors are used?
This mechanism allows a more sensitive response
51
What happens when you're too hot?
1. Hairs lie flat
2. Sweat is produced by sweat glands
3. Vasodilation
52
What is vasodilation?
Heat is lost by radiation from the skin
53
Explain how vasodilation works?
1. Blood vessels supplying skin dilate so more blood flows close to surface of skin
2. This helps transfer energy from skin to environment
54
Why is sweat is produced by sweat glands, when you're hot?
1. Heat energy is used to evaporate sweat from skin
| 2. This transfers energy to the environment
55
What happens when you're too cold?
1. Hairs stand up to (erect)
2. Vasoconstriction
3. You shiver
56
Why does your hairs erect when you're cold?
To trap insulating layer of air
57
What is vasoconstriction?
Reduced heat loss by radiation from the skin
58
Explain how vasoconstriction works
1. Blood vessels supplying skin capillaries constrict (become narrower) to close off the skin's blood supply (blood is away from surface)
2. Reducing the transfer of heat energy from skin to environment
59
When you're cold why do you shiver?
Your muscles contract automatically as this needs respiration, which transfers some heat energy (by product) to warm the body
60
What are goosebumps the result of?
Your hairs standing up
61
What happens to people when they get frostbite?
Blood supply to fingers and toes is cut off to reduce amount of energy lost (this kills cells and they go black)
62
What removes glucose from the blood normally?
1. Normal metabolism of cells
| 2. Exercise
63
What monitors and controls the blood glucose levels?
Pancreas
64
When blood glucose level is too high, what is released?
Insulin
65
When you sweat more water is lost, therefore what do you have to do to balance this loss?
More fluid has to be taken in through drink or food
66
What does insulin do?
1. Causes excess glucose to be converted to glycogen (move from blood and into cells)
2. Causes cells to take in glucose
67
Where is excess glucose stored as and where?
As glycogen in muscles and liver
68
How is excess glucose stored when the stores in the muscles and liver are full?
It's stored as lipid
69
What is secreted when blood glucose level is too low?
Glucagon
70
What does glucagon do?
1. Causes liver to convert stored glycogen back to glucose
| 2. Glucose is returned to the blood (& blood glucose level rises)
71
What is type 1 diabetes?
Is where the pancreas produces little or no insulin
72
Why is type 1 diabetes dangerous?
A person's blood glucose level can rise to a level that can kill them
73
What do people with type 1 diabetes need?
Insulin therapy - usually involves serval injections of insulin through the day (most likely at mealtimes)
74
Why does insulin therapy do?
Makes sure glucose is removed from blood quickly onces food has been digested = stopping the level getting too high
75
Why is insulin therapy used?
Because it's a very effective treatment
76
What does the amount of insulin that needs to be injected into a diabetic (type 1) person depend on?
Depends on person's diet and how active they are
77
What should people with type 1 diabetes do?
Limit intake of food rich in simple carbohydrates and take regular exercise = helps remove excess glucose from blood
78
What is type 2 diabetes?
Is where a person becomes resistant to their own insulin
79
What can type 2 diabetes cause?
Can cause person's blood sugar level to rise to a dangerous level
80
What can increase your chance of having type 2 diabetes?
Obesity
81
How can type 2 diabetes can be controlled?
By eating a carbohydrate-controlled diet and getting regular exercise + drugs that help cells respond to insulin
82
How is excess water removed?
Via the kidneys in the urine
83
What do kidneys make and how?
Make urine by taking waste products out of blood
84
What is filtration (kidneys)?
Substances are filtered out of blood as it passed through the kidneys
85
What is selective reabsorption (kidneys)?
Useful substances (glucose, some ions and right amount of water) are absorbed back into bloodstream as they're needed by the body
86
How is water reabsorbed (in kidneys)?
By osmosis
87
How is glucose and ions reabsorbed (in kidneys)?
Active transport
88
What is ultrafiltration?
Due to high pressure, all small molecules are forced out of capillaries into kidneys
89
What are nephrons?
Tubes in kidney
90
What is osmoregulation?
Reabsorption of water
91
Proteins (and amino acids that they are broken down into) can't be...
stored by body
92
What is deamination?
When excess amino acids are converted into fats and carbohydrates which can be stored
93
Where does deamination occur?
In the liver
94
What is a waste product of deamination?
Ammonia
95
What and where is ammonia converted into and why?
Ammonia is toxic so it's converted to urea in liver
96
Where is urea in the liver taken to and why?
Transported to kidneys where it's filtered out of blood and excreted from body in urine
97
Where is urea also lost?
From skin in sweat
98
Where do we lose water from?
From skin in sweat and from lungs when breathing out
99
How is the amount of water in our body balanced?
By amount we consume and amount removed by the kidneys in urine
100
How do ions get into our bloodstream?
Ions are taken into body as food and then absorbed into the blood
101
What happens if the ion (or water) content of body is wrong?
1. Could upset balance between ions and water
2. Means too much or little water is drawn into cells by osmosis
3. Having wrong amount of water can damage cells or mean they don't work as well as normal
102
How are some ions lost?
In sweat
103
How is the balance of ions in body maintained by?
The kidneys
104
How does the the kidneys maintain the balance of ions in body?
Right amount of ions is reabsorbed into blood after filtration and rest is removed from body in urine
105
What is the concentration of urine is controlled by?
An anti-diuretic hormone (ADH)
106
What releases ADH?
The pituitary gland
107
Where is ADH released into?
The bloodstream
108
What monitors the water content of blood?
The brain
109
If you are dehydrated, what happens?
1. ADH secreted into blood
2. Kidneys reabsorb more water
3. Less urine with is more concentrated
110
If you are hydrated, what happens?
1. Less ADH secreted into blood
2. Less water is reabsorbed in kidneys
3. More urine that's more dilute
111
How is the production of ADH controlled?
By a negative feedback mechanism
112
Name 3 things that occur in the liver
1. Excess animo acids deaminated to form ammonia = converted into urea for excretion
2. Poisonous substances detoxified and breakdown products are excreted in urine via kidneys
3. Old blood cells are broken down and iron is stored
113
Name 5 things healthy kidneys do
1. Blood is filtered
2. All glucose is reabsorbed
3. Dissolved ions needed by body are reabsorbed
4. As much water as body needs is reabsorbed
5. Urea, excess ions and water are released as urine
114
What do diuretic drugs do?
Remove excess water in body
115
Why are diuretic drugs used?
So boxers, jockeys and weight lifters can drop a weight-class/lose weight quickly
116
If your kidneys don't work properly, what happens?
1. Waste substances build up in blood and you lose your ability to control levels of ions and waters in body
2. Eventually, results in death
117
How can people with kidney failure be treated?
1. With dialysis treatment
| 2. Have a kidney transplant
118
Why does dialysis have to be done regularly?
To keep concentrations of dissolved substances in blood at normals levels, and to remove waste substances
119
In dialysis machine, where does a person's blood flow?
Between partially permeable membranes surrounded by dialysis fluid
120
What does dialysis fluid contain?
Has same concentration of dissolved ions and glucose as healthy blood
121
Why does dialysis fluid contain the same concentration of dissolved ions and glucose as healthy blood?
So useful dissolved ions and glucose won't be lost from
| blood during dialysis + only waste substances (e.g. Urea) and excess ions and water diffuse across barrier
122
How many dialysis session do patients with kidney failure have to have per week?
3
123
How long is each dialysis session roughly?
3-4 hours
124
What can dialysis cause? (harm-wise to body)
May cause blood clots, infections and/or collapsed veins
125
Being on a dialysis machine is _____ for NHS to run
Expensive
126
Why is dialysis mainly used?
To buy patient with kidney failure valuable time until donor organ is found
127
What is the only cure for kidney failure?
Having a kidney transplant
128
Who are healthy kidneys usually transplanted from?
People who have died suddenly
129
You could only use a dead person's organs if the person has what?
A donor card or if they're on organ donor register
130
Besides dead people, where else can kidneys be transplanted from?
From people who are still alive (as we have 2 of them)
131
What is the risk with a donor kidney?
Donor kidney can be rejected by patient's immune system
132
How can we prevent a donor kidney being rejected?
By treating a patient with drugs to prevent it (but it can still happen)
133
Why might a donor kidney be rejected?
Recipient's antibodies may attack the antigens on the donor organ as they don't recognise them
134
Why should people have transplants instead of dialysis? (name 2 reasons)
1. Transplants are cheaper (in long run) than dialysis
| 2. Puts an end to hours patients have to spend on dialysis
135
What is the downside of kidney transplants (excluding rejection)?
There are long waiting lists for kidneys
136
What detects an increase in CO2 and where does this signal go?
Receptors to brain (CNS)
137
What is the response to an increase in CO2?
Trigger muscles in heart to contract
