Endocrine system Flashcards
1
Q
How does endocrine transmission occur
A
Chemical secreted
Low concentration
By a cell or group of cells
Sent to all parts of body
Via blood stream
Hormone acts only in cells with correct membrane receptor protein (target cells)
2
Q
What are the properties of hormonal communitcation
A
Many cells in different parts of body
Coordinated, body-wide actions
Slow to act
Effect persists
3
Q
What are the endocrine glands in the body
A
Hypothalamus
Pituitary
Thyroid
Parathyroid
Pancreas (Islets)
Adrenal (supra-renal)
GI tract endocrine cells
Gonads (ovaries and testes)
Placenta
Pineal gland
Thymus
4
Q
How can hormones be classified
A
Steroids
Non-steroids
-Amino acid derivatives
-Peptides
-Glycoproteins
5
Q
What are some steroid hormones
A
Based on cholesterol ring structure
-Cortisol
-Aldosterone
-Testosterone
-Oestrogen
-Progesterone
6
Q
What are some non-steroid amino acid derivative hormones
A
Amines
-Adrenaline (epinephrine)
-Noradrenaline (norepinephrine)
-Melatonin
Iodinated amino acids
-Triiodothyronine
-Tetraiodothyronine (thyroxine)
7
Q
What are some non-steroid short chain peptide hormones
A
Antidiuretic hormone
Oxytocin
Melanocyte stimulating hormone
Somatostatin
8
Q
What are some non-steroid long chain peptide proteins
A
Growth hormone
Prolactin
Parathyroid hormone
Calcitonin
9
Q
Where is the pre-prohormone converted to prohormone
A
Endoplasmic reticulum
10
Q
Where is prohormone packaged
A
Golgi apparatus
11
Q
What is prohormone converted to
A
Active hormone
12
Q
What secretes active hormone
A
Vesicles
13
Q
What are glycoproteins
A
Protein with attached carbohydrate groups to amino acids
14
Q
What are some non-steroid glycoprotein hormones
A
Follicle stimulating hormone
Luteinizing hormone
Thyroid stimulating hormone
Chorionic gonadotrophin
15
Q
What hormone-like substances have a local (paracrine) effect
A
Prostagrandins
Leucotrienes
Thromboxanes
16
Q
What are the functions of local effect hormones
A
Blood flow regulation
Haemostasis
Mucosal protection (stomach)
Inflammation
17
Q
What are common second messengers
A
cAMP and Ca2+
18
Q
Where are hormones metabolised
A
Liver
19
Q
What is hypersecretion
A
Excess secretion
20
Q
What is hyposecretion
A
Decreased secretion
21
Q
What is upregulation
A
More receptors
22
Q
What is downregulation
A
Fewer receptors over time
23
Q
What occurs during hyperfunction
A
Excess production & secretion
Upregulation of receptors
Failure to metabolise hormone
24
Q
What occurs during hypofunction
A
Decreased production & secretion
Downregulation of receptors
Receptors non functioning
25
Can prohormone produce response
Yes - much less of a response
26
Why do we have prohormone and the hormone if they can both produce a response
Prohormone produces a much lesser response allowing the hormone to be stored in concentrations which would otherwise be dangerous in the full hormone
i.e. Insulin would be too dangerous to store in high conc as if it was released unnecessarily this could be fatal to the person
27
What are the sections of the pituitary gland
Anterior pituitary
Posterior pituitary
Infundibulum
28
What does the hypothalamus control
Thermoregulation
Hormone secretion
-Primary hormones
-Trophic hormones
Circadian rhythms
Motivation
-Thirst, feeding, sexual behaviour
Emotions
29
What causes hormones secretion from the anterior pituitary
Releasing hormones are produced in the hypothalamus which pass to the anterior pituitary via hypothalamic-pituitary portal vessels and trigger secretion of hormones from the AP
30
How do hormones in the hypothalamus pass to the PP
Nerve axons
31
What are some hypothalamic hormones
Corticotropin releasing hormone (CRH)
Gonadotrophin releasing hormone (GRH)
Thyrotropin releasing hormone (TRH)
Growth hormone releasing hormone (GHRH)
Somatostatin (SS) (GH inhibiting hormone)
Prolactin releasing hormone (PLRH)
Dopamine (DA) (also PLIH)
32
What anterior pituitary hormones would you expect to find
Adrenocorticotropic hormone (ACTH)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Thyroid stimulating hormone (TSH)
Growth hormone (GH)
Prolactin (PL)
33
How many hormones are involved in creating an action to resolve a stimulus
3
hypothalamus - 1
Anterior pituitary gland - 2
Target organ - 3
34
How will the body react to 'stressors'
Hypothalamus- Corticotropin RH
AP - ACTH
Adrenal cortex - Cortisol
35
What controls the release of FSH and LH
Gonadotrophins
36
What hormons stimulates testosterone production and ovulation production of oestrogen & progesterone
LH - luteinising hormone
37
What does FSH stimulate
Sperm production and ovum maturation, oestrogen production
38
What does thyrotrophins release
Thyrotropin
Thyroid stimulating hormone
Thyroid hormones
39
What are somatotrophins
Growth hormones RH and IH both released from hypothalamus which lead to the release of growth hormone at the APG
40
What does the release of prolatin stimulate
Breast development and milk production
41
How is Prolactin released
Prolatin RH is produced in the hypothalamus leading to the release of Prolactin in the APG
42
What hormones are released in the PP
Antidiuretic hormone (ADH)
Oxytocin
43
Where asre ADH and oxytocin produced initially
These are produced by neurons in the hypothalamus and pass along the axons to the posterior part of the pituitary
44
Which nucleus produces ADH
Paraventricular
45
Where is oxytocin produced
Supraoptic nucleus
46
What are the steps to releasing ADH
Stimulus
Hypothalamus - ADH axonal transport
PPG - ADH in plasma
Kidney - Water reabsorbed in collecting ducts
47
What stimulus lead to release of oxytocin
Infant suckling and strech of uterus
48
What action does the release of oxytocin into plasma promote when stimulated by the stretch of uterus
Contraction of uterus
49
What does infant suckling encourage when oxytocin is released
Milk ejection
50
What are some endocrine glands
Thyroid gland
Parathyroid glands
Pancreas (Islets of Langerhans)
Adrenal (suprarenal) glands
Gonads:
-ovaries
-testes
Placenta
51
What hormones does the thyroid gland produce
Thyroid hormones T3, T4
Calcitonin
52
What produces calcitonin
C cells
53
What are the actions of T3 and T4
Increase metabolic rate of all cells
Determines basal metabolic rate
Essential for normal fetal and childhood growth
Permissive effect on action of adrenaline by upregulating adrenoreceptors
54
What is the name of T4
tetra-iodo-thyronine (‘thyroxine’)
55
What causes disorders of thyroid hormones
Undersecretion
-Hypothyroidism
-Cretinism, Myxoedema
Oversecretion:
-Hyperthyroidism
-Grave’s disease
56
What are the symptoms of simple goitre
Thyroid swelling associated with iodine deficiency
Low levels of thyroxine result in increased secretion of TSH
Iodide added to salt
57
What hormones do islets of langerhans produce
Insulin
Glucagon
Somatostatin
58
When is insulin released
In response to raised [blood glucose], [amino acid], glucose-dependent insulinotropic peptide, vagus nerve
59
What does insulin promote the formation of
Glycogen
triglycerides
Facilitates protein synthesis
60
Where does insulin facilitate glucose entry into
Muscle cells, adipocytes
61
What factors inhibit insulin secretion
Adrenaline
Sympathetic nerves
somatostatin
62
What factors promote insulin secretion
Increase Blood glucose
Increase Blood amino acids
Glucose-dependent, insulinotropic peptide
Vagus nerve activity
63
When is glucagon released
Released in response to low blood glucose concentration
acts to raise blood glucose
64
What are the actions of glucagon
Glycogenolysis in liver,
Gluconeogenesis in liver,
Lipolysis and ketone synthesis
65
What inhibits glucagon secretion
Insulin
Somatostatin
66
What promotes insulin secretion
increased Blood glucose
Increased Blood amino acids
Cholecystokinin
Autonomic nerve activity
67
What are the clinical features of diabetes
Polyuria (increased urine production)
Polydipsia (increased fluid intake; thirst)
Glycosuria (glucose in urine)
Diabetic neuropathy
Skin and oral diseases, incl. periodontitis, xerostomia
68
What is diabetes
Elevated blood glucose concentration
Decreased glucose uptake by cells
Metabolic changes
Gluconeogenesis; lipolysis
Two basic types
69
What is type 1 diabetes
Insulin-dependent
decreased Insulin secretion
Destruction of beta-cells
Autoimmune?
10% of cases
“Early” onset
Insulin injections and diet
70
What is type 2 diabetes
Insulin-independent
Insulin levels “normal”
Decreased target cell responsiveness to insulin
Related to overweight
“Late” onset
Diet, oral hypoglycaemic agents
71
What hormones does the adrenal glands secrete
Cortex hormones (‘corticosteroids’)
-aldosterone
-cortisol
-androgens
Medulla
Modified sympathetic ganglion
-adrenaline (epinephrine)
72
What is cortisol
Glucocorticoid hormone
Produced by cells of zona fasciculata of adrenal cortex
Controlled by ACTH from Ant pituitary
Actions:
-Metabolic effects
-Permissive effects
-Anti-inflammatory, immunosuppressant
73
What is aldosterone
Mineralocorticoid
Produced by cells of zona glomerulosa
Release controlled by the renin-angiotensin system
74
What are the actions of aldosterone
promotes reabsorption of Na+ and H2O in kidney (DCT)
Increases excretion of H+, K+
75
What is the Renin-angiotensin-aldosterone system
Renin from the juxta-glomerular apparatus is used toconvert angiotensinogen to angiotensin 1 which is then converted to angiotensin 2 with angiotensin converting enzyme which moves to the adrenal cortex and increases the aldosterone released in turn increasing the Na+ reabsorption in cortical collecting ducts
76
What are androgens
Gonadocorticoids from zona fasciculata and reticularis of adrenal cortex
The main hormones are androgens, which contribute to growth and 2o sexual characteristics in boys and girls
Pubertal growth spurt
77
What does excess glucocorticoid cause
Cushing's syndrome
-fat pads
-pendulous abdomen
-moon face
-thin skin
-poor wound healing
-poor muscle development
-striae
-bruisability with echymoses
78
What may excess androgens cause
Adreno-genital syndrome
-Heavy arms and legs
-Hirsutism
-Androgenic flush
-Small breasts
-Baldness, receeding hairline
-Enlarged clitoris
-Male escutcheon
79
What is the adrenal medulla
This is a modified sympathetic ganglion
Controlled by pre-ganglionic sympathetic nerves
The cells mostly produce adrenaline
Adrenaline release augments the action of the sympathetic nervous system
80
What does adrenal insufficiency cause
Addison’s disease
Decreased adrenal function and reduced levels of adrenal hormones:
-Glucocorticoids
-Mineralocorticoids
Very serious condition
81
How do we lose and gain water
Gains
Water ingested (food and drinks)
Water formed in metabolism
Losses
Excretion: urine, faeces
Evaporation: sweat, in expired air
82
How much water approx do we lose via each process
Losses (ml/day)
Urine (1500)
Faeces (100)
Evaporative sweat, breathing (800)
Total = (2400)
83
What is the only factor of water balance under homeostatic control
Urinary secretion
84
What are the sections of a nephron
Glomerulus
Proximal convuluted tubule
Distal convuluted tubule
Loop of henle
Collecting duct
85
What is the conc of renal blood flow
1200ml/min
86
What is the function of the glomerulus
Filtration of plasma 120ml/min
87
What are the variing filtration pressures within the glomerulus
Pressures vary along length of glomerular capillary from afferent arteriole - efferent arteriole)
Capillary hydrostatic (blood) pressure 45-50mmHg
Plasma protein oncotic pressure 25-35mmHg
Capsular pressure 10mmHg
Net filtration pressure 10-15mmHg
88
What occurs in the proximal convoluted tubule
Obligatory reabsorption of 60 – 70% of the glomerular filtrate
Ions, small organic molecules are reabsorbed
Secretion of H+ (acid-base balance)
Active transport; facilitated diffusion
Relatively little control over what is reabsorbed
89
What determines the conc of urine
The active transport pumps in the ascending limb of loop of henle
90
What corrrelates wih the length of the loop of hele
Ability to conc urine
91
Why do we have a loop of henle
Important for conc of urine
Some net reabsorption of fluid (10% of GFR)
92
What occurs in the distal convoluted tubule
Reabsorption of water, Na+, Cl–, Ca2+
Secretion of H+, K+
93
What hormones control the activity in the DCT
Aldosterone
Atrial natriuretic hormone
ADH (in most distal parts)
Parathyroid hormone
94
What is metabollic acidosis
When acids build up in the body fluids (too many H+ ions)
95
What is the purpose of the collecting ducts
Water reabsorption, under the influence of ADH
ADH provides membrane channels for water reabsorption
Water moves along osmotic gradients created by the counter current exchange mechanism
96
What is responsible for regulating water and electrolytes
Antidiuretic hormone (ADH)
Renin-angiotensin-aldosterone
Atrial Natriuretic Hormone (ANH,ANF,ANP)
97
What is another name for Vasopressin
ADH
98
How does ADH control water reabsorption
Acts on distal convoluted tubules (distal end) and collecting ducts to increase water permeability
By insertion of aquaporin channels
Water moves passively along osmotic gradient between tubule lumen and interstitial fluid
99
What is octapressin
Also known as viniopressin which is an analogue of vasopressin which acts as a vasoconstrictor
Used in conjunction with Citanest
100
What stimulates ADH secretion
Decreased plasma volume
Decreased baroreceptor distension
OR
Increased plasmaosmolarity
Increased osmoreceptor activation
RESULTING IN:
Increased ADH release
Increased water permeability
101
Why is it names vaso-press-in
Vasoconstrictor - decreases size of lumens
102
How is ADH secretion increased
Decreased ECF volume (low pressure receptors in atria and great vein
Increased ECF osmolarity (Osmoreceptors in hypothalamus)
103
What happens to ADH as plasma osmolarity increases
Increases
104
What happens to ADH levels when blood volume or pressure increases
Decreases
105
What ions are present in ICF and ECF and what are they called
Electrolytes
Na+, K+, H+, Ca2+
106
What controls the levels of electrolytes
Homeostasis, much of which operates through the kidneys which determine secretion volumes
107
What hormones are responsible for Na+ levels
Renin-angiotensin-aldosterone system
-Promotes reabsorption of Na+ (and water) in DCT; exchange for K+, H+
-Angiotensin is a potent vasoconstrictor
Atrial Natriuretic Hormone
-Increases excretion of Na+ (and water)
-Opposite effects to aldosterone
108
Why do we need K+ and how is it regulated
Cell membrane potentials depend on ECF [K+]
Small changes in [K+]ECF can have big effects on nerve/muscle function
K+ is regulated by aldosterone; Na+ is swapped for K+ or H+
109
What can hypo and hyper ADH secretion result in
Hypo-secretion:
-Diabetes insipidus
-Large volumes of insipid (tasteless) urine (cf. diabetes mellitus)
Hyper-secretion:
-Syndrome of inappropriate ADH (SIADH)
-Excess ADH water retention
110
What are the effects of K+ on nerve function
Increasing ECF [K+] - depolarisation
Depolarisation causes axons to fire AP
But the MP does not return to ‘resting’ levels
Result is that axon remains in an extended ‘refractory period’
K salts are used in toothpastes to desensitise ‘hypersensitive dentine’
111
Does sensodine toothpaste actually reduce sensitivity
Exposure of dentinal tubules poses threat when brushing, causing production of tertiary dentine reducing sensitivity in teeth
Toothpaste actually has little effect on the reduction of sensitivity
112
How does K+ ions reduce sensitivity
K+ ions diffuse from paste along tubules
Raise [K+] at inner end of tubule
Nerves depolarised;
Na+ channels inactivated; prolonged refractory period
Problem: K+ build-up does not persist
113
How does a decrease in plasma volume increase renin secretion
Decreased plasma volume
Increased sympathetic nerve activity
Decreased renal blood flow - greater flow rate (decreased Na+ in tubular fluid), macula densa
Decreased stretch of J-G baroreceptors
Juxta-glomerular apparatus
Increased renin secretion
