Regulating homeostasis Flashcards
1
Q
What is an external environment?
A
The environment outside an organism
2
Q
What is an internal environment?
A
The fluid surrounding the cells (in a multicellular organism). It is also called the extracellular fluid
3
Q
What are some examples of extracellular fluid?
A
Tissue fluid, plasma, cerebro-spinal fluid, lymph
4
Q
What is intracellular fluid?
A
The fluid inside the cell (cytosol)
5
Q
What is homeostasis?
A
The ability of an organism to regulate and maintain a stable internal environment (within tolerable limits) in response to internal or external changes
6
Q
What is another word for homeostasis?
A
Dynamic equilibrium
7
Q
Why is being able to regulate an internal environment important?
A
Allows the organism to survive a greater range of conditions
8
Q
What can happen if the internal environment is not adapting?
A
Cellular damage, death
9
Q
What is the process of homestasis?
A
Detection of change from a stimuli by receptors, stimulating a response from effectors
10
Q
What systems control homeostasis in animals?
A
Endocrine and nervous system
11
Q
What systems control homeostasis in plants?
A
Endocrine system
12
Q
How is homeostasis maintained?
A
Feedback loop systems
13
Q
What is the feedback loop mechanism?
A
- A stimulus/initial event effects a key variable from a stable state, creating a signal
- The signal is detected by a receptor
- The signal is transferred to the control centre
- The control centre sends a signal to the effector
- The effector works to respond to the signal
14
Q
What is an osmoconformer?
A
The solute concentration of internal environment is isotonic to external environment
15
Q
What is an example of an osmoconformer?
A
Decorator crab
16
Q
What is a benefit to being an osmoconformer?
A
No energy expended
17
Q
What is a negative to being an osmoconformer?
A
Less tolerable to external changes
18
Q
What is an osmoregulator?
A
Internal solute concentration is able to be controlled
19
Q
What is the benefit to being an osmoregulator?
A
Tolerating fluctations in external environment
20
Q
What is the negative to being an osmoregulator?
A
Energy expended tolerating changes
21
Q
How does a negative feedback system work?
A
They respond to stimuli by reversing the direction of change, to bring back to the original state
22
Q
What is an example of a negative feedback system?
A
Producing perspiration that cools the body by evaporative cooling. This assists to reduce the core temperature of the body thus decreasing the original stimuli
23
Q
What is a positive feedback loop?
A
Response causes an increase in the original stimulus (not a part of homeostasis)
24
Q
Are positive feedback loops mechanisms to maintain homeostasis?
A
No
25
What is an example of a positive feedback loop?
Pressure on the cervix in childbirth releases the hormone oxytocin, stimulating more contractions and greater pressure on the certix. This is then progressing labour
26
What is the stimulus-response model?
1. Stimuli affecting a key variable from a stable signal, causing a signal
2. Detected by a receptor.
3. Signal is transferred to the control centre
4. Control centre sends a message to an effector
5. Effector works to respond to the signal
27
What are receptors?
Substances that detect stimuli and respond by triggering a response to the release of a hormone or initiating signals in the nervous system
28
How many receptor types are there?
4
29
Which receptors are stimulated by chemical change?
Chemoreceptors
30
Examples of what stimulates a chemoreceptor
Respiratory gases, water, glucose
31
Where are chemoreceptors located?
Blood (major arteries), taste buds, nose, lungs, brain
32
What are mechanoreceptors?
a receptor stimulated by mechanical forces or pressure changes. They are stimulated by forces that change the shape of a sensory nerve ending
33
Examples of what stimulates a mechanoreceptor
Sound, vibration, touch, pressure
34
Where are mechanoreceptors located?
Skin, ears, blood vessels, lungs, joints
35
What stimulates a photoreceptor?
Light
36
Where are photoreceptors located?
Eyes
37
Where are thermoreceptors located?
Skin, brain
38
What stimulates thermoreceptors?
Temperature changes
39
What are hormones?
Signalling molecules that are responsible for communication between organs and tissues
40
Where are hormones commonly involved in?
The response arm of the negative feedback loop
41
What are hormones produced by?
Specialised cells. In complex animals, these cells are clumped together in organs called 'endocrine glands'
42
How do hormones exert their effect?
Passing directly through the plasma membrane or interacting with the receptor on the outside of the cell
43
What is the hypothalamus?
The collecting centre, receiving information/stimuli form all parts of the body about inernal condition. It uses this information to control the secretion of homrones by the pituitary glands
44
What is the exception to a body system not regulated by the hypothalamus?
Blood glucose levels, which is monitored by the pancreas
45
Why are hormones highly specific?
Only released with a specific simuli from a specific gland
Only certain receptors can react
46
Where is the pituitary gland located?
Underneath (and connected to) the hypothalamus)
47
What is the role of the pituitary gland?
To secrete hormones that affect target cells or that regulate secretion from other glands
48
What does the anterior gland do?
Produce hormones involved in growth and regulation
49
What does the posterior lobe do?
Stores hormones produced by hypothalamus
50
What is the mode of action of hormones?
Transported to where they are required by circulatory system (animals) or diffusion (signals)
51
How do hormones create an effect?
Act by transmitting signals to target cells, which possess a specific receptor for a specific hormone.
52
How do hormones exert their effect?
By passing through a plasma membrane or interacting with the receptor on the outside of the cell
53
How much energy do hormones require?
Very little -> they are free of charge
54
What is the source of the hormone insulin?
Pancreas - islets of Langerhands B cells
55
What is blood glucose required for?
Cellular respiration
56
Where is glucose stored?
As glycogen in the liver
57
What is the site of action for insulin?
Body cells
58
What does insulin regulate?
Blood sugar levels
59
What is the source of glucagon?
Pancreas - alpha cells
60
What is the site of action for glucagon?
Liver
61
What does glucagon regulate?
Blood sugar levels
62
What happens when blood glucose is high?
Pancreas (specifically Islets of Langerhans) detects it. More insulin is secreted by beta cells. This decreases blood glucose by increasing blood glucose uptake by cells. Alpha cells decrease glucagon production, moving glucose from bloodstream into liver and converting it into glycogen. Fat cells take up more glucose.
63
What happens when blood glucose is low?
Pancreas detects it. Alpha cells secrete more glucagon, which has the effect of converting glycogen back to glucose and releasing it back into the blood stream.
Beta cells produce more insulin, which decreases rate of glucose uptake by liver and body cells
64
How does adrenaline play a role in increasing blood glucose levels?
Its actions on fat, muscle and liver
65
What does antidiuretic hormone (ADH) regulate?
Amount of water intake
66
What is the source of ADH?
Hypothalumus makes it. Pituitary gland secretes it
67
What is the source of Thyroid stimulating hormone (TSH)?
Anterior pituitary
68
What is the site of action for TSH?
Thyroid
69
What does TSH regulate?
Release of thyroxine
70
What is the source of thyroxine?
Thyroid
71
What is the site of action for thyroxine?
Body cells
72
What does thyroxine regulate?
Cellular metabolic rate
73
What does adrenaline regulate?
Fight or flight response
74
What is the site of action for adrenaline?
Heart and muscles
75
What is the source of adrenaline?
Adrenal glands
76
Why is the nervous system faster acting than the endocrine system?
Because nerve action is due to electrical impulses (which travel very quickly), while hormones travel from production site to target cells via bloodstream
77
Why are hormones longer lived than nerve signals?
Because hormones must be metabolised before actions stop + inactivation time can take hours to days, while transmitter signals act for a fraction of a section and then are inactivated
78
What is blood glucose required for in the body?
Main source of energy, required for cellular respiration, stored in the body as glycogen in liver + muscle
79
How is blood glucose regulated?
2 antagonistic hormones (secreted by Islets of Langerhans)
- insulin: beta cells
- glucagon: alpha cells
80
What level is blood glucose meant to be at?
4-6mmol/L in the blood
81
What effect does insulin have?
Increasing the rate of glucose uptake by cells, stimulating the conversion of glucose to glycogen by liver cells, having fat cells take up glucose when insulin is present (makes more fat)
82
What happens when blood glucose is low?
Pancreas detects problem. Pancreas secretes glucagon, targeting liver and muscle cells. Glucagon decreases the rate of glucose uptake by liver cells, as well as a converting the glycogen back to glucose and releasing it into bloodstream. Adrenaline also contributes to raising blood glucose levels with its effect of fat, muscle and the liver
83
What is hyposecretion?
Underproduction of hormones
84
What is hypersecretion?
Overproduction of hormones
85
What types of cancer are linked to diseases of the endocrine system?
Cancers of the endocrine glands
86
What is diabetes characterised by?
Hyperglycaemia (higher than normal blood glucose levels) particularly after a meal. Excretion of glucose in urine
87
What is Type 1 Diabetes?
An autoimmune condition in which the immune system destroys the insulin-producing beta cells in the Islets of Langerhans in the pancreas
88
What is Type 2 Diabetes?
Failure of the muscle and liver cells to respond sufficiently to insulin
89
When looking at a graph of a glucose tolerance test, what are the signs of diabetes?
Higher initial concentration of blood glucose (over 8mmol/L). When glucose is taken in (glucose tolerance test), the blood glucose rises at a much greater rate and takes longer to return to original level
90
What are the diabetes symptoms caused by?
High glucose levels
91
What can high glucose levels lead to?
The kidneys work hard to get rid of excess glucose. This results in increased urine production, glucose in urine, excessive thirst and dehydration, excessive hunger, etc. This can lead to blurred vision and vessel damage
92
How can diabetes be managed?
Glucose intake is balanced with insulin injections and exercise
93
What is the name of regulating temperature?
Thermoregulation
94
What temperature does the thermoregulatory centre regulate in most mammals?
37.5 (+ or - 0.5)
95
What is it called when the internal temperature is too high?
Hyperthermia
96
What happens in hyperthermia?
Enzymes denature
97
What is the name of the state in which the human body is below temperature set point?
Hypothermia
98
What is an example of when the temperature set point can be regulated?
During a fever. Certain chemicals (pyrogens) released by white blood cells raise the set point. This causes the whole body temp. to increase by 2-3C -> kills bacteria, inhibits viruses, explains why you shiver even though hot
99
What is a homeotherm/endotherm?
An animal that controls their own body temperature
100
What is a poikilotherm/ectotherm?
An animal that depends on their external environment from heat supply
101
What is an example of a poikilotherm?
Reptiles
102
What is conduction?
Heat moves from a warm object to an object at a lower temperature
103
What is radiation?
Heat radiated from warm objects and absorbed by cooler objects
104
What is convection?
Currents in air or water move heat from one area to another
105
What is evaporation?
Heat is lost as water evaporates from the surface of a warm object (cools object)
106
Where is the thermoregulatory centre in the body?
Hypothalamus
107
What are the two sets of thermoreceptors that give input to the hypothalamus?
1. Receptors in the hypothalamus monitor the temperature of the blood as it passes through the brain (measures core temperature)
2. Receptors in the skin monitor the skin temperature and neurons transmit information to the hypothalamus
108
Which systems regulate temperature?
Endocrine and nervous
109
What happens when the body temperature falls?
Hypothalamus detects problem. It relays messages via motor neurons to activate skeletal muscles shivering and constrict arterioles to reduce heat loss from skin. Hypothalamus secretes thyrotropin-releasing hormone from neurosecretory cells. TRH signals pit. gland to make TSH. TSH stimualtes thyroid gland to release thyroxine. This causes a metabolism increase, so heat production rises. Furthermore, sweat glands don't secrete fluid
110
What happens when the body temperature rises?
The hypothalamus picks up this signal. It tells the blood vessels to dilate, allowing heat loss. It tells the sweat glands to secrete fluid. It reduces metabolism
111
What are some processes that occur when body temperature lowers?
Blood vessels constrict
Sweat glands do not secrete fluid
Shivering (involuntary contractions) generate heat
112
What are some processes that occur when body temperature rises?
Blood vessels dilate, sweat glands secrete fluid
113
What happens when blood water levels are low?
It is detected by the hypothalamus, which signals the pituitary gland to start or increase ADH production. High ADH signals kidneys to produce a small amount of con. urine
114
What happens when blood water levels are high?
Hypothalamus detects, signalling pituitary gland to stop or decrease ADH production. Low ADH menas a large amount of dilute urine is made.
115
How does seeking shelter reduce heat loss?
Traps heat, extra insulation
116
How does changing body shape reduce heat loss?
Alters SA:V of skin, reducing exposed surface area
117
How does putting on more clothes reduce heat loss?
Insulating layer betweeen body and environment. traps layer of air
118
How does voluntary reduce heat loss?
Metabolic processes, convert stores to energy, increased blood flow to muscles
119
How does vasoconstriction of vessels reduce heat loss?
Amount of blood near exposed surface decreases
120
How does piloerection reduce heat loss?
Constricts of piloerector muscles around hair follicles (goosebumps), which increases insulation of hairs.
121
How does non-shivering thermogenesis reduce heat loss?
Increased cellular activity in brown adipose tissue (tissues warm). Brown fat breaks down for more energy
122
How does shivering thermogenesis reduce heat loss?
Metabolic heat increased
123
How does increasing metabolism reduce heat loss?
Increased metabolism
124
How does sweating increase heat loss?
Evaporation, increased blood flow
125
How does decreasing metabolism increase heat loss?
Less heat is made by processes
126
How does vasodilation of blood vessels increase heat loss?
More blood is sent to extremities
127
How does decreasing activity increase heat loss?
Less heat made by processes. Lower metabolism
128
How does covering body with water increase heat loss?
Water absorbs heat and then evaporates
129
How does changing body shape increase heat loss?
Increased exposed SA, more heat loss
130
How does removing clothing increase heat loss?
More exposed skin so more radiation, skin comes in direct contact with cool surfaces
131
How does moving out of sun into shade increase heat loss?
Decreased sunlight, more convective cooling
132
How does bathing in cool water increase heat loss?
Water absorbs heat
133
What part of the brain overseas the release of hormones?
Hypothalamus
134
Which part of the brain links the endocrine and nervous sytem?
Hypothalamus
