Physiology Flashcards
1
Q
What is an autocrine signal
A
Chemical signal that acts on the same cell
2
Q
What is an intracrine signal
A
Chemical signal that acts within the same cell
3
Q
List the types of hormone receptors
A
G-protein coupled receptors
Receptor Tyrosine Kinase (RTK) Families
Nuclear recpetors - class 1, 2 and hybrid
4
Q
List the main endocrine organs/glands in the body
A
Hypothalamus Pituitary gland 4x parathyroid glands Thyroid gland 2x adrenal glands Pancreas 2x ovaries 2x testes
5
Q
What does the endocrine system consist of
A
Ductless endocrine glands
Secretions occur from individual cells or groups that are organised into glands
6
Q
How do hormones travel around the body
A
Released into the extracellular fluid which then enter the circulation and travel to target site
7
Q
How does the endocrine system achieve specificity of signalling
A
Chemically distinct hormones
Specific receptors for each hormone
Distinct distribution of receptors across cells
8
Q
Endocrine signals are more enduring than nerves - true or false
A
True
They last a lot longer
9
Q
What are the 4 different chemical classes of hormones
A
Modified amino acids
Steroids
Peptides
Proteins
10
Q
Give examples of modified amino acid hormones
A
Adrenaline
Thyroid hormone
11
Q
Where do modified amino acids come from
A
Tyrosine
Tyramine
12
Q
Where do steroid hormones derive from
A
Cholesterol
13
Q
Give examples of steroid hormones
A
Cortisol
Progesterone
Testosterone
14
Q
Where do peptide hormones derive from
A
Larger precursor proteins
Cleaved into smaller units
15
Q
Give examples of peptide hormones
A
ACTH
ADH
16
Q
Give examples of protein hormones
A
Insulin
17
Q
What is a paracrine signal
A
Cell generates signalling molecules that act upon immediately adjacent cells – travels a short distance
18
Q
What is an endocrine signal
A
signalling molecule is released into extracellular fluid, enters the bloodstream and then travels through the bloodstream to reach it’s target cells
19
Q
Hormones act at very high concentrations - true or false
A
False
Very low concentrations
Very potent with sensitive receptors
20
Q
How can the hormone signal be amplified
A
Hormone binds to it’s receptor and triggers secondary pathways - amplifies
Initiates reliable biological response
21
Q
What causes variation in the length of action of a hormone
A
The different ways that they are inactivated
22
Q
Describe the complementary action of hormones
A
Several hormones can contribute to complex physiological functions
E.g. adrenaline, cortisol and glucagon all work for short term exercise
23
Q
Describe the antagonistic action of hormones
A
Some can work in opposing ways but in a balance
e.g. insulin and glucagon
24
Q
Describe how amine hormones are synthesised and stored etc.
A
Pre-synthesised by enzymes
Stored in vesicles
When Ca enters the cell (response to stimuli) its triggers release by exocytosis
25
Describe how peptide and protein hormones are synthesised and stored etc.
Presynthesised in series of proteolytic steps to mature hormone
Stored in vesicles/granules Released when Ca enters the cell in response to stimuli
26
Describe how steroid hormones are synthesised and stored etc.
Synthesized and secreted on demand
| Stimuli increases cell uptake of cholesterol and rate of conversion to intermediate
27
What is the common intermediate for all steroid hormones
pregnenolone
28
How are steroid hormones transported in the blood
Hydrophobic so travel bound to plasma proteins
29
Describe the functions of carrier proteins
Increase amount transported in blood
Provide a reservoir of hormone
Extend half-life of the hormone in the circulation
30
List 3 important specific carrier proteins
Cortisol-binding globulin (CBG) – binds cortisol
Thyroxine-binding globulin (TBG) – binds thyroxine
Sex steroid-binding globulin (SSBG) – binds mainly testosterone and oestradiol
31
List important general carrier proteins
Albumin - binds many steroids and thyroxine
Transthyretin - binds thyroxine and some steroids
32
How do carrier proteins act as buffers
If there is a surge of steroid release the globulins in the plasma mop up the excess by binding
This maintains the equilibrium
33
How do steroid hormones cross the capillary wall
Can only cross when free in the plasma
| There is an equilibrium between free and bound steroid so when some crosses wall, more is released from proteins
34
What is the primary determinant of plasma concentration
Rate of secretion
35
How is plasma concentration of a hormone maintained
Negative feedback mechanisms
| Keeps it at a set level
36
Describe the diurnal (circadian rhythm)
Secretion rates of hormones fluctuate throughout the day
37
How can hormones be excreted
Metabolism locally
By the liver
Excretion by the kidney
38
Which receptors are on the cell surface
G-protein coupled
| Receptor kinases
39
Which receptors are intracellular
Nuclear receptors
40
What binds to G protein coupled receptors
Amines and some proteins/peptides
41
What binds to receptor kinases
Some proteins/peptides
42
What binds to class 1 nuclear receptors
Many steroids hormones
43
What binds to class 2 nuclear receptors
Mostly lipids
44
What binds to hybrid nuclear receptors
Thyroid hormone
45
What do Gs proteins and receptors do
Increase activity of adenyl cyclase - more cAMP produced
46
What do Gi proteins and receptors do
Decrease activity of adenyl cyclase - less cAMP produced
47
What do Gq proteins and receptors do
Increase activity of phospholipase C
48
How do receptor kinases work
When the hormone binds there is a change in the receptor that allows phosphorylation of receptor itself on tyrosine residues
This allows the secondary pathway to start
49
How do class 1 nuclear receptors work
Hormones enter the cell and bind to intercellular receptor
This causes receptor to dissociate from inhibitory heat shock protein
The steroid:receptor can now enter the nucleus and exert its action
Binds to DNA response elements and results in changes in gene transcription
50
Describe the structure of the thyroid gland
Left and right lobes connected by isthmus
| Isthmus may be absent
51
What does the thyroid gland secrete
Thyroxine - T4
Tri-iodothyronine - T3
Calcitonin
52
Where are the parathyroid glands located
2 behind each lobe of the thyroid gland
| 4 small glands in total
53
What do the parathyroid glands secrete
Parathyroid hormone
54
What physiological process can cause the thyroid to enlarge
Pregnancy
| Menstruation
55
What is the innervation of the thyroid gland
Autonomic
Parasympathetic from vagus nerve
Sympathetic from superior, middle and inferior ganglia of sympathetic trunk
56
What is the arterial supply to the thyroid gland
Superior and inferior thyroid arteries - branch from external carotid
57
What is the venous drainage from the thyroid gland
Superior and middle thyroid veins - drain into internal jugular
Inferior thyroid vein - drains into brachiocephalic
58
Describe the cellular structure of the thyroid gland
Made up of follicles which store the hormones
Follicular cells surround a central colloid
Also get occasional parafollicular C cells that produce calcitonin
59
Drugs to reduce thyroid hormone production have instant effects - true or false
FALSE
| Takes around 3 weeks to start working due to stores of hormones in the follicles
60
Which element is required to make thyroid hormones
Iodine
| Absorbed into follicle via iodine transporters
61
Describe the synthesis of thyroid hormones
Iodine is taken up by follicular cells
Enters the colloid of the follicle where thyroglobulin is stored
Attaches to tyrosine residues on the thyroglobulin's to produce MIT or DIT
There is coupling of MIT and DIT to form T3 or DIT and DIT to form T4
Stored in colloid until required
62
How do drugs for hyperthyroidism such as carbimazole work
Inhibit the attachment of iodine to the thyroglobulin to prevent hormone synthesis
63
Which thyroid hormone is the major biologically active one
T3
| Other enzymes will convert T4 to T3 by removing an iodine to make it more active
64
Which thyroid hormone is secreted in the greatest amount
T4
| Makes up 90% of hormone secreted
65
How do thyroid hormones travel in the blood
Hydrophobic so most travel bound to plasma proteins
| Small amount is unbound – biologically active as available to tissue
66
How do you convert T4 to T3
Remove an iodine
| This makes it active
67
List the plasma proteins that thyroid hormones can bind to
Thyroxine binding globulin - TBG
Thyroxine binding prealbumin - TBPA
Albumin
68
What can cause an increase in TBG
Pregnancy
Pill - oestrogen sources
Hepatitis (A & chronic)
Heroin
69
What can cause a decrease in TBG
```
Androgens
Large dose of glucocorticoids
Cushing's
Severe systemic illness
Chronic liver disease
```
70
What are the action of thyroid hormone
Target almost every tissue in the body
Can alter gene transcription etc
Has big effect on:
metabolism, growth, reproduction and behaviour
71
What effect do thyroid hormones have on metabolic rate
Increase basal metabolic rate
Increase number and size of mitochondria
Increase oxygen use and ATP hydrolysis
Works with GH to control metabolism
72
What effect do thyroid hormones have on thermogenesis
Increase it
73
What effect do thyroid hormones have on carb metabolism
Increase blood glucose by stimulating glycogenolysis and gluconeogenesis
Increase uptake of glucose
74
What effect do thyroid hormones have on lipid metabolism
They mobilise fat from tissue - increase free fatty acids
| Increase fatty acid oxidation
75
What effect do thyroid hormones have on protein metabolism
Increase protein synthesis
76
What effect do thyroid hormones have on growth
Growth hormone releasing hormone needs them to be produced and secreted
GH needs them for activity
77
Are thyroid hormones needed for normal CNS activity
YES
| The 2 extremes will cause abnormal CNS symptoms
78
How do thyroid hormones affect adrenaline action
Increase the response to nor-adrenaline by increasing the number of receptors
This affects force and rate of the heart
79
How is the release of thyroid hormones regulated
TRH from hypothalmus is needed to stimulate release of TSH from pituitary
TSH stimulates release of T3 and T4 from thyroid
T3 and T4 exert negative feedback control of TRH and TSH if their levels get too high
80
How can low temperatures affect the release of thyroid hormone
In kids, cold temps stimulates TRH release which goes on to cause TSH and then T3/4 release
81
How can stress affect release of thyroid hormones
It inhibits TRH and TSH release
82
How does the circadian rhythm affect thyroid hormones
thyroid hormones highest late at night, lowest am
83
Which enzymes can convert T4 to T3
Deiodinase enzymes
Type 1, 2 & 3
Can remove iodine to activate or inactivate depending on the number and position taken from
84
Where is T1 deiodinase enzyme found
Liver and Kidney
| safety enzyme – allows you to still produce active T3 hormone in the liver
85
Where is T2 deiodinase enzyme found
Heart, skeletal muscle, CNS, fat, Thyroid and pituitary
| most important as it activates T4-T3 in most tissues
86
Where is T3 deiodinase enzyme found
In foetal tissue and placenta and brain
87
What can lead to deficiency in thyroid hormones
Primary failure – may be associated
with enlarged thyroid
Secondary to TRH or TSH (no goitre)
Lack of iodine in diet
88
What are the symptoms of an underactive thyroid
```
Reduced BMR
Slow pulse rate
Fatigue, lethargy, slow response times and mental sluggishness
Cold-intolerance
Tendency to put on weight easily
```
89
What are the symptoms of an overactive thyroid
```
Increased BMR
Very fast pulse rate
Increased nervousness and excessively emotional
insomnia
Sweating and heat intolerance
Tendency to lose weight easily
Frequent bowel movements
Fine, brittle hair
Tremor
Changes in menstrual pattern
```
90
What is the most common cause of hyperthyroidism
Grave's disease
| Autoimmune disease where TSI acts like TSH
91
Describe how G protein coupled receptors work
The receptor is made up of a 7 transmembrane domain
When ligand binds there is a conformational change which activates the associated G protein
This goes on to generate secondary messengers by acting on effectors
92
What is the major determinant of hormone concentration
rate of secretion
| Impacted by feedback loops
93
which hormones should be tested at 9am and why
Cortisol
Testosterone
This is when they usually peak during the day
94
What kind of test is required for GH
Dynamic testing
| It is secreted randomly in pulses throughout the day so you cannot tell if you've got an accurate level on random test
95
Where is prolactin secreted from
The lactotroph cells of the anterior pituitary
96
Where are most male androgens produced
Testes
97
Where are most female androgens produced
Adrenal cortex
98
Describe the synthesis of steroid hormone
All come from cholesterol
Go through a complex series of enzyme reactions to form final products: testosterone, aldosterone and cortisol
Defects in these enzymes can lead to sex related issues, slat wasting or low cortisol
99
Describe the phases of the menstrual cycle
Follicular phase - first 14 days (variable)
Starts with period and then follicles develop and release oestrogen
Ends with ovulation around day 14
Luteal phase also lasts 14 days and progesterone starts to rise (falls if no fertilisation)
100
What hormone is released by the ovum
oestrodiol
101
What hormone is released by the corpus luteum
progesterone
102
What hormone is released by the placenta
hPL - Human Placental Lactogen
Progesterone
Oestrogens
103
What hormone is picked up on pregnancy tests
HCG
| released after implantation
104
What type of cells make up the anterior pituitary
Acidophils - somatotrophs (GH) and mammotrophs (PRL)
Basophils - corticotrophs (ACTH), thyrotrophs (TSH) and gonadotrophs (FSH/LH)
Chromophobes
105
What type of cells make up the posterior pituitary
non-myelinated axons of neurosecretory neurons
106
Where are the adrenal glands found
Sit superior and medial to upper pole of kidneys
| Bilateral
107
What are the adrenal glands composed of
An outer cortex and a central medulla
| Central medulla made up of neuroendocrine cells
108
Which pituitary hormones have a direct action on organs
ADH
Oxytocin
Growth Hormone
Prolactin
109
What is the function of GnRH
gonadotrophin releasing hormone
| released from the hypothalamus and stimulates the release of LH and RSH from the anterior pituitary
110
What are the functions of LH and FSH
Luteinising hormone and follicle stimulating hormone
Released from anterior pituitary
Act on testes/ovaries and cause the release of sex hormones testosterone/oestrogen and progesterone
111
What effect does testosterone have when it is released from the testes
increased muscle and bone mass
Increased libido
Increased penile length
Impacts hair follicles - causes growth
112
What effect do oestrogen and progesterone have when they are released from the ovaries
Increased bone and fat mass
Develops the vagina
Impacts heart and liver
113
Where is cortisol released from
The adrenal glands
114
What is the function of cortisol
Most important stress hormone - without it you die
regulates blood sugar - increases plasma glucose
increases fat in the body - increase lipolysis
helps defend against infection
helps us respond to stress
increases responsiveness of adrenoreceptors
Stops us going into shock
Accelerates osteoporosis
115
What is the function of ACTH
released from anterior pituitary
| Acts on the adrenal glands to stimulate cortisol production
116
What is the function of CRH
Corticotropin-releasing hormone
| Released from hypothalamus and acts on the anterior pituitary to stimulate ACTH release
117
What is the function of TRH
thyrotrophin releasing hormone
| Released from hypothalamus and acts on the anterior pituitary to stimulate TSH release
118
What is the function of TSH
thyroid stimulating hormone
| Released from anterior pituitary and acts on the thyroid gland to stimulate thyroxine release
119
What is the function of GHRH
growth hormone releasing hormone
released from hypothalamus
Stimulates the anterior pituitary to release growth hormone
120
What is the function of dopamine
Released from the hypothalamus
| Inhibits the production of prolactin in the anterior pituitary
121
What is the function of ADH
Released from hypothalamus and then stored in the posterior pituitary
Released when needed to act on kidneys to cause water retention
122
What is the function of OXT
Oxytocin
Released from hypothalamus and then stored in the posterior pituitary
Released when needed to act on smooth muscle of ductus deferens, prostate or uterine smooth muscle and mammary glands
123
Which hormone does GH stimulate the release of
IGF-1
| insulin-like growth factor 1
124
What hormones are secreted from the zona reticularis of the adrenal gland
Androgens
| DHEA
125
What hormones are secreted from the zona fasciculata of the adrenal gland
Cortisol
Cortisone
Corticosterone
126
What hormones are secreted from the medulla of the adrenal gland
Adrenaline
| Nor-adrenaline
127
when are steroid hormones synthesized
When the cells producing them respond to a stimuli
| They aren't stored within cells
128
What is the function of aldosterone
Release is stimulated by angiotensin II
It increase NaCl retention and reabsorption in the kidney
This also leads to water retention due to osmosis - increased blood volume and pressure
Helps regulate extracellular volume
129
What impact does cortisol have on CO
By increasing responsiveness of adrenoreceptors it increases CO
This also increases BP
130
What hormones are secreted from the glomerulosa of the adrenal gland
Mineralocorticoids - aldosterone
131
What are the sources of androgens
In females the only source is the adrenal glands
| In males the majority is produced in the testes but also some from adrenal glands
132
How is are the production of cortisol and androgens regulated
regulated by hormones produced by hypothalamus and anterior pituitary gland
133
How is the production of aldosterone regulated
The renin-angiotensin system and plasma potassium levels
134
What are the 6 classes of steroid receptor
```
Glucocorticoid
Mineralocorticoid
Progestin
Oestrogen
Androgen
Vitamin D
```
135
Where are mineralocorticoid receptors found
Kidneys - majority
Salivary glands
Gut
Sweat glands
136
Which mineral adds strength to bone
Calcium phosphate
137
What is the function of parathyroid hormone
Sense calcium levels within the body via calcium sensing receptors
Regulates serum calcium and serum phosphate
Activates vitamin D
138
Where is secreted from calcitonin
It is a polypeptide secreted from parafollicular cells within the parafollicular C cells in the thyroid gland
139
How is vitamin D activated in the body
Taken in via diet and sunlight
Activated by enzymes in the liver and kidneys - hydroxylated in both
The version released from the kidneys is the active one
140
List functions of calcium in the body
Bone strength
Excitability of smooth and cardiac muscle
Secretion of peptide and hormones
Excitability of neuromuscular junctions in skeletal muscle
Role in blood clotting
141
What stimulates parathyroid hormone release
Hypocalcaemia
142
Describe the action of parathyroid hormone
Increases osteoclastic activity - resorption of bone allows calcium in it to be released
In the kidney and gut it increases calcium reabsorption and increases excretion of phosphate
Have role in production and activation of vitamin D
143
What is the role of calcitonin
Secreted in extreme cases of hypercalcaemia
It acts to decrease serum calcium
Opposite to PTH
144
How does calcitonin work
It inhibits osteoclasts - decreases bone reabsorption
| Decreases absorption in the intestine and the kidneys
145
what is the difference between endocrine and exocrine
endocrine glands secrete hormones directly into the blood
| exocrine glands secrete hormones into a network of ducts
146
Which hypothalamic hormones are classed as releasing ones
```
Growth hormone releasing hormone
Prolactin releasing hormone
Thyrotropin releasing hormone
Corticotrophin releasing hormone
Gonadotrophin releasing hormone
```
147
Which hypothalamic hormones are classed as inhibiting ones
Somatostatin - inhibits release of GH
| Dopamine - inhibits release of prolactin
148
Which hypothalamic hormones are peptides
All except dopamine which is an amine
149
Describe the action of GH
Increases gluconeogenesis - increased blood glucose
Releases more insulin growth factors
Decreases glucose uptake in the muscle cells and increased it in the brain
Increases rate of lipolysis
Increases protein synthesis
150
What is meant by negative feedback in relation to hormones
Product hormones often feedback on the endocrine organs further up the pathway to suppress production
Keeps the levels at normal levels
151
How does magnesium affect PTH function
Magnesium helps PTH work - allows it to be released and act effectively
Therefore you should always check Mg as well as calcium
