Endocrine System Flashcards
1
Q
What is homeostasis?
A
The presence of a stable internal environment.
2
Q
What can happen if homeostasis is not maintained?
A
It can lead to illness and even death
3
Q
What is negative feedback and what is its purpose?
A
When an effector activated by the control system opposes, or negates, the original stimulus ie. it reduces the change until the stimulus is removed or it directly inhibits further release.
It tends to minimise change, keeping variation in key body systems within limits compatible with our long term survival.
4
Q
What is positive feedback?
A
When an initial stimulus produces a response that exaggerates or enhances the change in the original conditions, rather than opposing it ie. there is an amplification of a change until a desired outcome is achieved
5
Q
Describe how homeostasis in maintained
A
A change in these controlled variables is detected by a control centre and it signals effectors (organs or tissues). The effector responds to these signals by (usually) opposing the stimulus. These effects could be localised or the whole body.
6
Q
What is the difference between a set point and a normal range?
A
The set point is the point where the body wants to be (eg. an internal temp of 37.5 degrees).
But the body never stays at this one point; it oscillate above and below this point. This is how we get the normal range.
7
Q
Homeostatic control is not
A
precise
it maintains a normal range rather than an absolute value
8
Q
What is the population reference range?
A
The population reference range is based on the width of individual normal ranges within a population, covering most of the people in a population and most of their normal ranges
9
Q
How do individual normal ranges and population reference ranges differ?
A
The population reference range tends to be wider than normal fluctuations within an individual. Some people can still exhibit symptoms of disorder even though they are inside the population range because they are outside their own normal range.
10
Q
Most individuals will have a set point that is
A
within the population reference range
11
Q
Some people can still exhibit symptoms of disorder even though they are inside the population range because
A
they are outside their own normal range
12
Q
Compare the neural and endocrine control systems
A
- Synaptic:
- action potentials in axons and neurotransmitter release at the synapse
- targeting achieved by one neuron synapsing onto another to get that signal going where we want
- fastest transmission speed to minimise response delays between signals and receptors
- good for brief responses
- Endocrine:
- hormones released into the blood
- targeting by presence of specific receptors on target cells
- relatively slow but long lasting action
- good for widespread and sustained responses
13
Q
What does the endocrine system consist of?
A
endocrine gland cells that secrete hormones which are carried into the bloodstream to the target cells upon which they act on.
14
Q
What are hormones?
A
chemical messengers that allow one cell type to communicate with another cell type without the use of neurons
15
Q
What are the main endocrine glands? (6)
A
- hypothalamus
- pituitary gland
- thyroid gland
- adrenal glands
- pancreas (pancreatic islets)
- parathyroid glands
16
Q
What is the role of the hypothalamus?
A
It links the nervous system to the endocrine system and controls the secretion of many endocrine glands
17
Q
What are some physiological variables that are maintained homeostatically through hormones?
A
- blood sugar concentration
- growth and repair
- basal metabolic rate (how much energy our body uses)
- blood calcium concentration
18
Q
What is a true hormone?
A
Chemical messengers produced in one location and transported via the bloodstream to a second location (target cell) where they cause a response in the cell
19
Q
What are three mechanisms of cellular communication?
A
paracrine communication
autocrine communication
endocrine communication
20
Q
Describe paracrine communication
A
A cell releases things (paracrines) into the extracellular fluid. Actions of paracrines are limited to nearby the releasing cells
21
Q
Describe autocrine communication
A
A cell releases things into the EC fluid (autocrines). They only act upon the cell that secreted them.
22
Q
Describe endocrine communication
A
It is through the bloodstream and the chemical signals are hormones. These target cells for the hormones are often in very distant tissues and organs from the cell that released the hormone
23
Q
What is a receptor?
A
A protein that can be in the plasma membrane or inside the cell that allows a hormone to target that cell
24
Q
What is a target cell?
A
A cell that the hormone acts upon to create a response
25
What are the two types of hormones?
water-soluble hormones
| lipid-soluble hormones
26
Describe water-soluble hormones and give two examples
they can not cross the plasma membrane because they are water soluble
the receptors are located in the plasma membrane
eg. peptides and catecholamines
27
Describe lipid-soluble hormones and give two examples
they can diffuse across the cell membrane into the target cell
the receptors are located in the cytoplasm or nucleus
eg. steroid and thyroid hormones
28
Describe water-soluble hormone receptor activation
- water soluble hormone binds to the receptor surface (which is on the plasma membrane)
- this allows the activation of the intracellular protein G-protein
- this causes one of three responses: adenylyl cylase is activated or inhibited, or intracellular Ca2+ ions
- these cause a SECOND MESSENGER production or reduction (eg. an increase or decrease of cAMP, or increase in Ca2+ acting as second messenger)
- cAMP and Ca2+ cause downstream proteins and pathways to be activated or deactivated
29
Describe lipid-soluble hormone receptor activation
- the lipid-soluble hormone dissociates from a carrier protein
- the hormone diffuses across the cell membrane to reach receptors
- the hormone binds to intracellular receptors (in the cytoplasm or nucleus)
- the hormone-receptor complex acts as a specific transcription factor (ie. it moves onto DNA and binds to a particular region of the DNA)
- this causes a target gene to be activated
- mRNA is generated. It moves out of the nucleus into the cytoplasm
- a new protein is generated by the translation on mRNA
- the new protein mediates cell specific responses
30
How does the chemical classification of water-soluble and lipid soluble hormones differ?
water-soluble:
- peptides (most abundant)
- catecholamines
lipid-soluble:
- steroids
- thyroid hormones
31
How does the storage of water-soluble and lipid soluble hormones differ?
water-soluble:
- stored until they are required (released by exocytosis)
lipid-soluble:
- steroids made from cholesterol as required (not stored)
- thyroid hormones are made in thyroid cells and stored until required
32
How does the transport of water-soluble and lipid soluble hormones differ?
water-soluble:
- dissolved into the blood
lipid-soluble:
- bound to a carrier protein
33
How do the receptors of water-soluble and lipid soluble hormones differ?
water-soluble:
- on the cell surface
lipid-soluble:
- intracellular receptors in cytoplasm or nucleus
34
How does the mechanism of action of water-soluble and lipid soluble hormones differ?
water-soluble:
- through second messengers
lipid-soluble:
- by altering gene transcription and causing the formation of new proteins
35
How does the speed of response of water-soluble and lipid soluble hormones differ?
water-soluble:
- milliseconds to minutes
lipid-soluble:
- hours to days
36
What does the amount of hormone in the blood depend on?
- rate of human secretion
| - rate of removal from blood
37
The removal of hormones from the blood is controlled by
enzymes in the blood or in target cells
38
The goal of a hormone is to
maintain homeostasis
39
Secretion is usually controlled by a
negative feedback loop
40
Describe the exocrine gland of the pancreas
- 99% of the organ's volume
- cells of pancreatic acini secrete digestive enzymes
- secrete alkaline, enzyme rich fluid that reaches the lumen of the intestinal tract through one or more pancreatic ducts
41
Describe the endocrine gland of the pancreas
- about 1% of the organ's volume
- consists of pancreatic islets
- contain β cells and α cells
42
What do β cells secrete?
insulin
43
What do α cells secrete?
glucagon
44
What can happen if homeostasis is not maintained and blood glucose concentration gets too high for too long?
Diabetes
45
What can happen if homeostasis is not maintained and blood glucose concentration gets too low for too long?
Hypoglycaemia
46
What is the only source of energy that the brain uses?
glucose
47
What are the two metabolic states?
fed state
| fasting state
48
What happens during the fed state?
- cellular uptake of nutrients
- anabolic metabolism (making molecules)
- synthesis of glycogen, protein and fat
- glucose is moved from our bloodstream into a storage system which we can then access later when we are in the fasting state
49
What is the fed state?
a metabolic state when we have just eaten
50
What is the fasting state?
after long periods of not eating
51
What happens during the fasting state?
- mobilisation of nutrients
- catabolic metabolism (breaking down molecules)
- breakdown of glycogen, protein and fat
52
Insulin and glucagon try and maintain a blood concentration between
70-110 mgdL-1
53
Describe how the body maintains homeostasis after an increase in blood concentration
- the β cells secrete insulin into the bloodstream
- insulin travels to target cells
- decrease in blood glucose concentration
54
What role do the β cells have in releasing insulin
as both the sensor and control centre
55
What are the target cells for insulin?
Muscle and adipose cells
| liver cells
56
Insulin being released to reduce the blood glucose concentration is an example of:
negative feedback control because by decreasing the blood glucose concentration, we remove the stimulus (an increased blood sugar concentration) and so now without that stimulus, the β cells are going to stop secreting insulin
57
Insulin is a _______-________ _________ hormone and the target cells have _________ receptors
water-soluble
peptide
membrane
58
What effect does insulin have on muscle cells?
- increase in net glucose uptake
- increase in amino acid uptake
- uses amino acids and glucose to make proteins
- converts glucose to glycogen
59
What effect does insulin have on adipose cells?
- increase in net glucose uptake
| - fat synthesis
60
What effect does insulin have on liver cells?
- prevents further production of glucose in the liver (stops glycogen --> glucose)
- increase in net glucose uptake
- glycogen and fat synthesis
61
What are 5 effects of insulin on the target cells?
1. increased rate of glucose transport into target cells
2. increased rate of glucose use and ATP generation
3. increased conversion of glucose to glycogen
4. increased amino acid absorption and protein synthesis
5. increased triglyceride (fat) synthesis in adipose tissue
62
Describe how the body maintains homeostasis after a decrease in blood concentration
- the α cells secrete glucagon
- glucagon travels to the target cells
- increase in blood glucose concentration and blood ketone concentration
63
What role do the α cells have in releasing glucagon?
the sensor and the control centre
64
What are the target cells for glucagon?
liver cells
65
Glucagon being released to increase the blood glucose concentration is an example of:
Negative feedback loop because by increasing the blood glucose concentration, we remove the stimulus (a decreased blood sugar concentration) and so now without that stimulus, the α cells are going to stop secreting glucagon
66
Glucagon is a _______-________ _________ hormone and the target cells have _________ receptors
water-soluble
peptide
membrane
67
What effect does glucagon have on liver cells?
- increased breakdown of glycogen to glucose
- increased glucose synthesis
- increased ketone synthesis
68
What is the breakdown of glucose called?
Glycogenolysis
69
What is glycogenolysis?
The breakdown of glucose
70
What is glucose synthesis called?
Gluconeogenesis
71
What is gluconeogenesis?
Glucose synthesis
72
What are the two distinct parts of the pituitary gland?
- anterior lobe
| - posterior lobe
73
Where is the pituitary gland located?
at the base of the hypothalamus, attached through the narrow infundibulum
74
What does the hypothalamus control?
the secretion of pituitary hormones (when activated by neural input, the hypothalamus stimulates the pituitary gland to secrete hormones)
75
How does the hypothalamus communicate with the posterior pituitary?
- hypothalamus connected to PP by neurons
| - the cell bodies in the hypothalamus and the axon terminate in the posterior lobe
76
Where are posterior pituitary hormones made?
in the hypothalamus
77
Describe the release of hormones from the posterior pituitary gland
- PP hormones are made in the hypothalamus in the cell body of the axons
- the hormones travel down the axon and are stored at the axons terminals until required
- the hypothalamus uses neural communication with the posterior lobe to release hormones into the blood (an increase or decrease in the frequency of action potentials leads to a change in hormone release)
78
What are the peptide hormones that are released from the posterior pituitary gland?
- antidiuretic hormone (ADH)
| - oxytocin (OXT)
79
What does ADH do?
stimulates the kidneys to absorb water (the kidneys conserve water when the body dehydrates)
80
What does oxytocin do?
- stimulates the contraction of uterine muscles during childbirth
- stimulates milk release in breastfeeding
81
The hormones released by the posterior pituitary gland are _______ hormones and are stored _______ ________
peptide
| until required
82
Describe the release of hormones from the anterior pituitary gland
- a neural input (stimulus) conducted down a short axon in the hypothalamus causes the release of releasing hormones from the hypothalamus
- this is released into the portal veins which carries the the hormone into the AP
- the hormone binds to receptors on specific cells types and a specific peptide hormone is secreted from the AP into the bloodstream
83
What are some peptide hormones released from the anterior pituitary gland?
Prolactin and growth hormone
84
Describe the feedback regulation of the anterior pituitary gland
- the hypothalamus secretes a releasing hormones
- the releasing hormones stimulate the release of a peptide hormone from the anterior pituitary hormone
- the peptide hormone causes the release of another hormone which causes an effect (releases another hormone)
- the hormone released by the target organ heads back to the hypothalamus and anterior pituitary to stop further release of the releasing hormones and pituitary hormone
- the peptide hormone also feeds back to the hypothalamus to stop release (and can also sometimes cause further release of itself)
85
When are growth hormone concentrations are highest? (in a day)
During the night
86
When are growth hormone concentrations are highest? (in a lifetime)
- higher in children than adults and they peak in puberty
| - secretion declines with ageing
87
Describe the release of the growth hormone from the anterior pituitary gland
- the hypothalamus has growth hormone releasing hormone (GH-RH)
- the GH-RH travels into the portal veins into the anterior pituitary gland which releases the growth hormone
- this travels to the muscle and fat cells which have direct effects and to the liver cells
- the liver releases Somatomedin C (IGF-1) which have indirect effects
88
What does the Somatomedin C (IGF-1) do?
It feedbacks to the hypothalamus and inhibits further release of GH-RH. It also feedbacks to somatostatin neurons which release GH-IH. The signal goes through the portal veins to reduce the release of GH (negative feedback)
89
What are some direct effects of the growth hormone on muscle cells?
Stimulates protein synthesis and inhibits cellular uptake of glucose
90
What is protein synthesis important for?
Growth
91
What are some direct effects of the growth hormone on liver cells?
stimulates glucose synthesis
92
What are some direct effects of the growth hormone on fat cells?
increases triglyceride breakdown in adipose tissue so that they can be used by other parts of the body for energy
93
What are some indirect effects of the growth hormone?
It promotes the growth of bones, muscle and other tissue by causing release of Somatomedin C which promotes cell division
94
How does the hypothalamus communicate with the anterior pituitary gland?
using releasing and inhibiting hormones via the portal veins
95
What are some indirect growth (long-term) effects of growth hormone?
- stimulates the growth of bones and muscles by stimulating cell division via insulin-like growth factor (IGF1)
96
What is cell division called?
mitogenesis
97
What are some direct growth (long-term) effects of growth hormone?
stimulates protein synthesis in muscles
98
What are some direct metabolic (short-term) effects of growth hormone?
- increases blood glucose by stimulating glucose synthesis (in the liver) and inhibiting cellular uptake of glucose
- increasing triglyceride breakdown and free fatty acid mobilisation in adipose tissue
99
Where is the thyroid gland?
just below the larynx on the anterior and lateral surfaces of the trachea
100
What are the hormones made and secreted from the thyroid gland?
- thyroid hormone
| - calcitonin
101
What is the thyroid hormone essential for?
optimal metabolic activity
102
What is calcitonin essential for?
calcium homeostasis
103
Describe the structure of the thyroid gland
- it is composed of small spherical sacs called follicle
- each follicle is surrounded by follicular cells and this is the site of thyroid hormone synthesis
- the clear cells (C cells) are where calcitonin is made
104
What are follicular cells?
simple cuboidal cells where the thyroid hormone is synthesised
105
Describe thyroid hormone synthesis:
- Iodine enters the follicular cell from the blood
- it travels into the follicle cavity (follicle) in vesicles containing thyroglobulin (TGB)
- the iodine reacts with tyrosine in the TGB molecules (this takes place in the follicle cavity)
- iodised TGB moves into the follicular cells
- thyroid hormones detach from TGB as needed (T3 and T4)
- T3 and T4 travel bound to a carrier protein (TBG) to target cells
106
What does TGB stand for?
thyroglobulin
107
What does TBG stand for?
carrier protein thyroid-binding globulin
108
What is T3?
the active form of the thyroid hormone which has 3 iodines attached
109
What is T4?
the inactive form of the thyroid hormone which has 4 iodines attached
110
How is a target cell activated by the thyroid hormone?
- T3 is carried to the target cell bound to TBG
- it detaches from TBG and enters the target cell
- T3 binds to the T3 receptor in the nucleus
- specific genes are activated to transcribe mRNA
- mRNA translation occurs in the cytoplasm and specific proteins are synthesised
111
Thyroid hormones are made ______ _______ and stored _______ __________
in advance
| until required
112
What is an example of a protein synthesised due to the thyroid hormone?
Na+/K+ ion pumps
113
What is the response time of the target cells due to the thyroid hormone?
45 mins to days
114
Due to the thyroid hormone, we can get an increase in genes being expressed from DNA in both the _______ and the ________
mitochondria
| nucleus
115
How is the release of the thyroid hormone controlled?
- after an external or internal stimulus lead to CNS input to hypothalamus
- the hypothalamus secretes TRH into the portal veins between the hypothalamus and the anterior pituitary gland
- the anterior pituitary gland secretes TSH
- this travels around the body until it reaches the thyroid gland
- the thyroid gland releases TH (T3 and T4) into the blood
- T3 has effects around the body
- T3 and T4 also inhibit the the further release TSH and TRH
116
What is TRH?
thyrotropin-releasing hormone and it is secreted by the hypothalamus
117
What is TSH?
thyroid-stimulating hormone which is released by the anterior pituitary gland
118
What is TH and what are some examples?
Thyroid hormones T3 and T4 released by the thyroid gland
119
What are some of the effects of T3 around the body?
It increases basal metabolic rate by increasing the synthesis and activity of the Na+,K+ pump
120
What are some other effects of thyroid hormones in the body?
- stimulates growth (foetus and early childhood)
| - promotes normal alertness and reflexes in the nervous system
121
What is the basal metabolic rate?
The body's rate of expenditure under basal conditions
122
What are basal conditions?
- awake
- at physical and mental rest
- lying down
- no muscle movement
- at a comfortable temperature
- fasted (12-18 hr)
123
How does the thyroid hormone affect metabolism?
- increases body heat production by increasing oxygen consumption and ATP hydrolysis
- Stimulates fatty acid oxidation (usage of storage fat) in many tissues
- increases proteolysis from muscle
- stimulates carbohydrate metabolism (usage of stored glucose) and enhances insulin-dependent entry of glucose into cells which increases gluconeogenesis and glycogenolysis
124
What is proteolysis?
Protein breakdown
125
In the presence of insulin and TH, cells tend to take up even more of the ______ ______ and increases the production of ________ and increases the breakdown of ______
blood glucose
glucose
glycogen
126
TH does not cause a significant increase in blood glucose because
There is a balance between the increase in production of glucose and the uptake/usage by cells
127
Where does calcium come from?
- in our diet
- some is absorbed into our intestines, some is removed in the faeces
- of that absorbed into our intestines, some is absorbed into the plasma, some is filtered into the kidneys and some is deposited into the bones by osteoblasts
- of that filtered into the kidneys, some is reabsorbed into the plasma and some is lost as urine
- of that deposited in our bone, some of it remains and some of it is reabsorbed into the plasma by osteoclasts
128
What is calcium important for?
contraction of muscles and release of neurotransmitters
129
What is the body's major store of calcium?
bone
130
Normally, a balance exists between the _______ _____-_________ of bone and the ________ of bone
constant build-up
| breakdown
131
What are the three hormones involved in calcium regulation?
Parathyroid hormone (PTH)
Calcitriol
Calcitonin
132
Where are the parathyroid glands?
Little bean-like structures on the posterior aspect of the thyroid gland
133
What does the parathyroid glands do?
secrete PTH
134
How is blood calcium concentration maintained?
eg. for a decrease in blood Ca2+ concentration:
- this is detected by the parathyroid gland
- it secretes the PTH which affects the kidneys, the bones and the intestines
- this causes an increase in Ca2+ concentration so it is a negative feedback control
135
How does PTH affect the kidneys?
- there is increased Ca2+ reabsorption into the plasma
| - this decreases the urinary excretion of calcium
136
How does PTH affect the bone?
- there is an increase in bone breakdown
| - this increases the release of Ca2+ into the blood (resorption)
137
How does PTH affect the intestines?
- PTH encourages the conversion of vitamin D to calcitriol
- Calcitriol travels in the blood to the intestines
- this increases the increase of Ca2+ absorption from food
138
How does the conversion of Vitamin D to calcitriol affect the bone breakdown, kidney Ca2+ reabsorption and its own conversion?
The conversion of vitamin D to calcitriol further increases the breakdown of bone and the reabsorption of Ca2+ from the kidneys.
Once we reach a certain level of vitamin D conversion to calcitriol, it stops further conversion
139
Where are the adrenal glands located?
superior to each kidney
140
What is are the adrenal glands made of?
Two separate glands
141
What are the two glands that make up the adrenal glands called?
Adrenal cortex
| Adrenal medulla
142
Describe the adrenal cortex
- 3 layers
| - secretes steroid hormones
143
What does the outer layer of the adrenal cortex secrete?
aldosterone to help maintain sodium homeostasis
144
What does the middle layer of the adrenal cortex secrete?
cortisol
145
What does the inner layer of the adrenal cortex secrete?
androgens which have a minor reproductive role
146
Describe the adrenal medulla
- part of the sympathetic nervous system
| - secretes adrenaline
147
Describe the response to stress in terms of the release of noradrenaline (norepinephrine) and adrenaline
NORADRENALINE:
- an action potential is propagated along the axon of a sympathetic preganglionic neuron starting in the hypothalamus in response to stress
- there is a synapse onto a sympathetic post-ganglionic neuron at the sympathetic chain ganglia
- there is a release of noradrenaline (norepinephrine -NE) at the target or effector cell
ADRENALINE:
- an internal or external stimulates a stress response which is assessed in the hypothalamus
- the hypothalamus propagates an action potential along a sympathetic preganglionic neuron
- when the action potential reaches the adrenal medulla, ACh is released
- this stimulates the adrenal medulla to secrete adrenaline (80%) and noradrenaline (20%) into the bloodstream
- this travels in the blood to target cells
148
Describe adrenaline
- water-soluble or lipid-soluble?
- what derivative is it?
- what sort of receptor does it have?
- how does it amplify cellular response
- does it acts fast or slow?
- water-soluble hormone
- amino acid derivative
- has a cell membrane receptor
- uses a second messenger system to amplify cellular response
- acts fasts
149
What effect does adrenaline have in response to stress?
In the skeletal muscle and liver cells?
In fat cells?
Other effects?
Makes fuel more readily available for the cells.
In skeletal muscle and liver cells:
- increased breakdown of glycogen to glucose
In fat cells:
- increased breakdown of fat to fatty acids
Other effects:
- systems not crucial for short term survival are shut down
150
What are the target cells of adrenaline?
skeletal muscle
liver
fat
151
Adrenaline and norepinephrine secretion is stimulated by
sympathetic preganglionic fibres during sympathetic activation
152
What happens if the concentration of Ca2+ in plasma gets too high?
- amount released?
- bone?
- kidneys?
- Vit D?
- there is a decrease in the release of PTH
- decrease in the breakdown of bone
- decrease in the reabsorption of Ca2+ from the kidneys
- reduces conversion of Vit D to calcitriol
153
What does calcitonin do?
If the plasma Ca2+ concentration gets way too high, calcitonin will be administered to immediately stop bone breakdown
154
What is cortisol?
Steroid hormone that is released in everyday life but can also be released in response to stress and non-stress stimuli
155
Describe the action of cortisol at a target cell
- how is it carried in the blood?
- how does it get into the cell?
explain the process (ie. is it a lipid-soluble or water soluble hormone)
- cortisol is carried in blood bound to a carrier protein
- it travels to the target cell and passes through the cell membrane
- it binds to a receptor in the cytoplasm
- the receptor complex travels into the nucleus of the cell
- cortisol binds to DNA to activate genes to initiate RNA transcription
- the RNA codes for a protein which has an effect in other cells
156
What is the protein that carries cortisol to the target cell?
cortico-steroid binding globulin
157
Describe the process to secrete cortisol from the time of input to the time of cortisol carried in the blood
- due to a non-stress neural input, the hypothalamus secretes CRH
- the CRH travels in the portal veins to the anterior pituitary glands
- this causes the AP to secrete ACTH
- ACTH travels in the bloodstream to the adrenal cortex
- the adrenal cortex secretes cortisol
158
What are non-stress neural inputs?
Everyday day-night rhythms when we have low blood glucose concentration
159
What does CRH stand for and what does it do?
It stands for corticotropin releasing hormone and it is released from the hypothalamus in response to a non-stress neural input (or in response to stress)
160
What does ACTH stand for and what does it do?
It stands for adrenocorticotropin hormone and it travels to the adrenal cortex to stimulate the release of cortisol
161
What cells does cortisol have an effect on?
- muscle
- fat
- liver
162
What effect does cortisol have on muscle cells?
- increase protein breakdown to utilise amino acids
| - decrease of glucose uptake
163
What effect does cortisol have on fat cells?
- increases fat breakdown
- releases lipids
- decrease of glucose uptake
164
What effect does cortisol have on liver cells?
increase in gluconeogenesis
165
Overall, cortisol has what sort of effect on its target cells?
it has metabolic effects and it affects the use of fuel
166
Apart from the effects on muscle, liver and fat cells, cortisol has what other effects?
- it can help one cope with stress
- it can suppress the immune system in the long term
- it is essential for maintaining normal blood pressure
- it also inhibits the further release of ACTH and CRH
167
How does cortisol affect the immune system?
Cortisol decreases white blood cells so the number of antibodies decreases.
It increases inflammatory response. When we have an internal injury, we will be able to see this as redness or swelling but cortisol stops this response
168
The secretion of cortisol under non-stress situations is an example of
negative feedback
169
When is the secretion of cortisol the highest?
upon waking up
170
What are some effects of cortisol in response to stress? (6)
1. increasing blood glucose levels
2. increasing fat, protein and carbohydrate metabolism to maintain blood glucose
3. promoting anti-inflammatory actions (reducing inflammation)
4. increasing blood pressure
5. increasing heart and blood vessel tone and contraction
6. activation of the CNS
171
How can we have problems with hormone signalling?
we can have problems with the hormone levels or problems with the hormone receptors
172
What is meant by "problems with hormone levels"?
Too much hormone is secreted or not enough is secreted
173
What is is called when too much hormone is secreted?
Hypersecretion
174
What is is called when not enough hormone is secreted?
Hyposecretion
175
What can cause the problems with hormone signalling?
- autoimmunity
- genetic mutation
- tumors
- other
176
What is meant by "problems with hormone receptors"?
There is too much response by the target cell to the hormone or not enough
177
What is is called when there is too much response to a hormone?
Hypersensitive
178
What is is called when there is not enough response to a hormone?
Hyposensitive
179
What is meant by autoimmunity causing problems with hormone signalling?
There is a destruction of the receptors leading to a hyposensitive response
180
What is meant by genetic mutation causing problems with hormone signalling?
mutations can cause gain or loss of function
181
What is meant by tumors causing problems with hormone signalling?
excess tissue usually leads to excess hormone release, but it can sometimes prevent release
182
How can tumors both increase and decrease the hormone release?
INCREASE:
There is excess thyroid tissue which may be also be increasing the release of a hormone but because it is a tumorous tissue, it may not be under the same regulatory control as the normal thyroid tissue.
DECREASE/PREVENTION:
The excess tissue may push onto other glands which decreases the secretion from those glands. For example, If you get a tumor in your thyroid gland, you may get a hypersecretion of one of the hormones released from the thyroid gland but a reduction of release from the parathyroid gland as the thyroid gland becomes pressed against the parathyroid
183
Give an example of a disease due to the reduction in cortisol
Addison's disease
184
What caused a reduction in cortisol levels that can lead to Addison's disease?
Hyposecretion due to autoimmunity and other factors
185
Describe Addison's disease including the symptoms
- there is lowered secretion of both cortisol and aldosterone
- a low cortisol level increases the release of ACTH (to try and increase cortisol levels)
- there is a build up of ACTH in the body
- excess ACTH stimulates melanin synthesis causing a darkening to the skin
- other symptoms include low blood pressure and weakness
186
Give an example of a disease due to the increase in cortisol
Cushing's disease
187
What caused an increase in cortisol levels that can lead to Cushing's disease?
Hypersecretion due to tumors and other factors
188
Describe Cushing's disease including the symptoms
- there is an increase in the secretion of cortisol
Symptoms:
- buffalo hump (deposition of fat on the upper back)
- moon face (rounded face)
- breaking down fat but it is not being utilised so there is a redistribution of fat
- high blood pressure
- weakness/muscle wasting
189
What are some examples of stress?
mental stress (like taking an exam)
famine
overpopulation (fighting for resources)
natural disasters
190
Outline the body's response to stress
- stress activates the hypothalamus
- hypothalamus organises a response and activates the
adrenal glands, sympathetic nervous system, posterior lobe of the pituitary gland
- the body responds
191
What are the three phases of stress?
1. alarm phase
2. resistance phase
3. exhaustion phase
192
Describe the alarm phase
- "fight or flight"
- the adrenal medulla secretes adrenaline and norepinephrine
- there is general sympathetic activation
- these cause some immediate short term responses to a crisis
193
What are some immediate short term responses to a crisis in the alarm phase? (8)
1. increased mental alertness
2. increased energy use by all the cells
3. mobilisation of glycogen and lipid reserves to form glucose
4. changes in circulation away from areas that don't need it
5. reduction in digestive activity and urine production
6. increased sweat gland secretion
7. increased heart rate (and force of contraction) and respiratory rate
8. changes in pupil diameter because we want increased awareness of surroundings
194
Describe what happens to the heart during the resistance phase
- cardiovascular disease and hypertension are linked to prolonged stress
- the cardiovascular tissue is activated by adrenaline which means the heart will be working harder because it is contracting with more force as well as more often
- it this happens for too often for too long, it might cause damage to the tissue
195
Describe what happens to the muscles during the resistance phase
- pain and various minor muscular twitches
| - nervous tics are more noticeable under stress
196
Describe what happens to the skin during the resistance phase
- problems such as eczema and psoriasis
197
Describe the exhaustion phase
When you experience a significant amount of stress for a really long amount of time
You run out of stores of energy - the heart is worked too hard for too long so may get a heart attack. Aldosterone is key because imbalance of ions in the body so there is less K+ ion fluid which is key to heart malfunction
198
Describe an integrated stress response
- a stress stimulates is notified by the hypothalamus
1.
- the hypothalamus secretes CRH which travels to the anterior pituitary gland
- the AP secretes ACTH which travels in the blood to the adrenal cortex
- the adrenal cortex synthesises and secretes cortisol
- cortisol causes an increase in blood glucose (by gluconeogenesis) and an increase in blood pressure
2.
- from the hypothalamus, action potentials travel down the sympathetic preganglionic fibres and synapse in the adrenal medulla
- the adrenal medulla secretes adrenaline
- this causes an increase in blood glucose level (by glycogenolysis), increased heart rate and blood pressure
3.
- from the hypothalamus, action potentials travel down neural connections and synapse at the posterior pituitary gland
- the PP secretes ADH
- there is a decrease in water excretion, an increase in blood volume and pressure
199
Give examples of diseases due to the increase and decrease in growth hormone
when too much GH is released - gigantism
| when not enough GH is released - dwarfism
200
Give an example of what can happen because of hyposecretion of thyroid hormone in babies?
Infantile hypothyroidism
201
Describe hypothyroidism
- low metabolic rate
- cold intolerant
- growth is retarded
- brain development is inhibited
- caused by lack of iodine in the mother's diet
202
Give an example of what can happen because of hyposecretion of thyroid hormone in adults?
Iodine deficiency disorder (eg. simple goitre)
203
Describe iodine deficiency disorder
- the thyroid gland is unable to make enough thyroid hormone (TH)
- this leads to TRH and TSH secretion increase to try and increase TH levels
- overstimulation of thyroid gland
- excess TSH stimulates growth of the thyroid gland
204
Give an example of hypersecretion of the thyroid hormone caused by autoimmunity
Grave's disease
