Endocrine system Flashcards
1
Q
What makes up the endocrine system?
A
All of the body’s different endocrine glands, tissues, and hormones
2
Q
What is the role of the endocrine system?
A
To regulate many biological processes in the body
3
Q
How do hormones work?
A
- secreted from endocrine gland
- carried in blood to target cells where it binds to specific receptor for that hormone on membrane or in cell
- causes change in activity of cell
4
Q
How many amino acids in a peptide hormone?
A
typically less than 50
5
Q
How many amino acids are in a polypeptide hormone?
A
Typically more than 50
6
Q
What are key features of protein/peptide hormones?
A
- water soluble
- non-lipid
- cannot cross phospholipid bilayer of target cells so must bind to receptor on its surface
7
Q
What happens after a protein/peptide hormone has bound to the target cell?
A
Triggers a series of messengers inside the cell which coordinates a response in the cell to switch genes on/off to affect the cell’s activity
8
Q
What are the key features of steroid hormones?
A
- lipid soluble
- synthesised from cholesterol
9
Q
How do steroid hormones work?
A
- diffuse through target cell membrane
- form receptor-hormone complex with a receptor in the cytoplasm
- complex moves into nucleus and binds to DNA which activates genes
10
Q
What are amine hormones synthesised from?
A
amino acids tryptophan and tyrosine
11
Q
What processes are amine hormones involved in?
A
stress response, metabolism
12
Q
How are endocrine glands stimulated?
A
- hormonal - another hormone binds to the cell
- humoral - fluctuation in ion/nutrient in blood
- neural - nerve from brain directly stimulates gland
13
Q
What are the major endocrine glands?
A
1, hypothalamus
2. pineal gland
3. pituitary gland
4. thyroid gland
5. parathyroid gland
6. adrenal glands
7. islet of Langerhans in pancreas
8. ovary
9. testes
14
Q
What is the hypothalamus?
A
A region of the brain located directly above the brainstem which is responsible for most endocrine control in body
15
Q
Where is the pituitary gland?
A
In the pituitary fossa of the skull connected to the hypothalamus by the infundibulum
16
Q
What does the pituitary gland do?
A
Releases several important hormones but is under the control of the hypothalamus
17
Q
What is the pituitary gland known as?
A
master endocrine gland
18
Q
What are the lobes of the pituitary gland?
A
- anterior pituitary (adenohypophysis)
- posterior pituitary (neurohypophesis)
19
Q
How is the posterior pituitary formed?
A
- from neural (brain) tissue
- in embryonic development, a bundle of nerves extend from the hypothalamus to form and outgrowth -> posterior pituitary
20
Q
What does the posterior pituitary do?
A
- stores hormones produced by hypothalamus (oxytocin and ADH)
- releases these hormones when signalled by hypothalamus into the bloodstream
- regulated directly by hypothalamus
21
Q
How is the anterior pituitary gland formed?
A
- In embryonic development
- Derived from tissues in roof of mouth which bud off, migrate to, and integrate with the hypothalamus
22
Q
What does the anterior pituitary do?
A
- hypothalamic neurons secrete hormones into anterior pituitary
- act on relevant groups of cells to inhibit or stimulate them
- produces hormones which act on various locations in the body
23
Q
What hormones does the anterior pituitary produce?
A
- Thyroid stimulating hormone (TSH)
- Growth hormone (GH)
- Adrenocorticotrophic hormone (ACTH)
- Follicle stimulating hormone (FSH)
- Luteinising hormone (LH)
- Prolactin
24
Q
What does thyroid stimulating hormone (TSH) do?
A
Stimulates thyroid to produce thyroid hormone
25
What does adrenocorticotrophic hormone (ACTH) do?
stimulates the adrenal cortex to secrete its hormones
26
What does follicle stimulating hormone (FSH) do?
regulates functions of gonads (ovaries and testes)
27
What does luteinising hormone (LH) do?
regulates functions of gonads (ovaries and testes)
28
What does prolactin do?
stimulates milk production in mammary gland
29
Where is the thyroid gland?
In neck region at C6-8 and T1 vertebrae
30
What are the features of the thyroid gland?
1. butterfly shaped with 2 lobes
2. lobes joined by isthimus
3. each lobe 5cm by 3cm
4. highly vascularised
5. most cells are cuboidal epithelial (follicular cells)
6. c-cells are inbetween these which are imp for regulating calcium levels
31
What are the functions of the thyroid gland?
1. produce thyroid hormone (TH)
2. produce calcitonin hormone
32
What does thyroid hormone (TH) do?
controls metabolism of glucose to form heat and energy so controls basal metabolic rate
33
What does calcitonin hormone do?
is secreted from c-cells when blood calcium is too high, and lowers it
34
How is thyroid hormone released?
1. hypothalamus stimulates pituitary with TRH
2. pituitary releases TSH
3. TSH stimulates release of TH when binds to thyroid
35
What are the variations of thyroid hormone?
1. Thyroxine (T4) - 4 atoms of iodine, amine, more abundant but less potent
2. Tri-iodothyronine (T3) - 3 atoms of iodine
36
How do T3 and T4 affect the body?
1. increase metabolic rate and heat production
2. regulate metabolism of carbs, proteins, fats
3. essential for normal growth and development
4. needed for healthy brain function
37
How does thyroid hormone level fluctuate throughout the day?
1. highest after waking up to start body metabolism and energy production for the day
2. decline in afternoon and evening
38
How is thyroid hormone regulated?
1. TH level detected by hypothalamus
2. Inhibits TRH from hypothalamus, which inhibits TSH
3. Anterior pituitary also senses elevation and reduces release
4. Fluctuations are tied to circadian rhythms
39
What is hyperthyroidism?
Overactive thyroid gland resulting in overproduction of T4 and T3
40
What can hyperthyroidism be caused by?
1. Graves disease - an autoimmune disease
2. Excessive iodine intake
3. Certain medications
41
What are the effects of hyperthyroidism?
1. Increased basal metabolic rate
2. Weight loss
3. Increased appetite
4. Anxiety and restlessness
5. High heart rate, palpitations, atrial fibrillation
6. Increased respiratory rate
7. Warm sweaty skin
42
What are the effects of hypothyroidism?
1. decreased metabolic rate
2. weight gain
3. depression
4. lethargy
5. fluid retention
6. dry, cold skin
7. slow heart rate
43
How can hyperthyroidism affect speech?
1. high pitched tremulous voice
2. uneven intonation
3. vocal fatigue
4. swelling of thyroid can compress trachea and cause dysphagia
44
How can hypothyroidism affect speech?
1. retarded laryngeal development and muscle atrophy -> weak voice
2. oedema in vocal tract -> incomplete closure of larynx in phonation and poor articulation from swelling in tongue and lips
3. swelling of thyroid can compress trachea and cause dysphagia
45
How does calcitonin work?
Inhibits activity of osteoclasts (which break down bone) so lowers blood calcium
46
What are the parathyroid glands?
Two glands on each of the posterior thyroid lobes which secrete parathyroid hormone
47
What does parathyroid hormone do?
1. released when there is low calcium
2. stimulates osteoclasts
3. stimulates kidneys to reabsorb calcium back into blood
4. increases active vitamin D levels
48
What causes excess parathyroid hormone production?
tumours in the gland
49
What will excess parathyroid hormone production cause?
1. high calcium levels in blood
2. low calcium in bones
3. weak bones
50
What is low parathyroid hormone production caused by?
1. removal or damage to gland in surgery
2. developmental disorder affecting pharyngeal arches
51
What are the effects of low parathyroid hormone?
1. hypocalcaemia
2. tetanic muscle spasms
3. tetany of laryngeal and respiratory muscles -> asphyxia
4. potentially fatal
52
What is growth hormone?
A large protein hormone which stimulates growth and division of cells in bone and skeletal muscle
53
How does growth hormone work?
1. stimulates liver to produce insulin-like growth factor
2. IGF stimulates protein synthesis for growth and repair
3. growth hormone promotes breakdown of fats
54
When is growth hormone release highest?
When sleeping
55
What can cause excess growth hormone?
Usually a benign pituitary tumour that secretes excessive growth hormone
56
What are the effects of excess growth hormone?
1. in childhood - excessive growth in height and body size in development (gigantism)
2. in adults - enlarged facial features, hands, feet, thick oily skin, skin tags, excessive sweating (acromegaly)
57
What causes growth hormone deficiency?
Cause often unknown, may be genetic mutations, brain tumours, infections
58
What are the effects of growth hormone deficiency?
1. in childhood - stunted growth, delayed development of secondary sexual characteristics, shorter stature
2. in adults - reduced muscle mass, increased body fat, decreased bone density
59
How can agromegaly affect speech?
Can lead to enlarged tongue, vocal cords and dental changes which may affect speech clarity and articulation
60
Where are the adrenal glands?
On top of kidney and enclosed within renal fascia
61
What are the parts of the adrenal gland?
1. adrenal cortex
2. adrenal medulla
62
What are the adrenal functions?
1. involved is stress response - emotional states, disease, surgery, trauma, sleep deprivation
2. involved in blood pressure regulation
3. secrete small amounts of sex hormones
63
What happens when the anterior pituitary releases adrenocorticotrophic (ACTH) hormone?
1. hypothalamus simultaneously releases corticotrophin releasing hormone (CRH) in stress
2. ACTH travels in blood to adrenal cortex
3. stimulates secretion of glucocorticoids
64
What are the main glucocorticoids?
1. cortisol
2. corticosterone
65
What do glucocorticoids do?
1. increase blood glucose levels
2. inhibit action of insulin
3. increase protein and lipid availability
66
What is the Hypothalamic-Pituitary-Axis?
A negative feedback loop by which when cortisol (stress hormone) levels rise, Corticotrophin Releasing Hormone (CRH) is inhibited, which reduces release of Adrenocorticotrophic Hormone (ACTH)
67
What is aldosterone?
A mineralcorticoid hormone released from adrenal cortex
68
How is the release of aldosterone stimulated?
Kidneys release angiotensin II when there is low blood pressure which stimulates its productions
69
What does aldosterone do?
1. stimulate nephrons to increase reuptake of sodium into filtrate of blood
2. cause secretion of potassium from blood into nephron
3. this all causes water to follow the sodium passively by osmosis to increase blood volume and pressure
70
What does the adrenal medulla develop from?
nervous tissue in the embryo - is part of the sympathetic nervous system
71
What hormones does the adrenal medulla release?
1. adrenaline
2. noradrenaline
amine hormones both known as catecholamines
72
What is the function of adrenaline?
1. Released quickly by neural control of hypothalamus
2. Release short burst of ATP to mobilise muscle
3. Increase cardiac activity and muscle glucose levels
73
What is the function of noradrenaline?
1. increase blood pressure
2. neurotransmitter in CNS
74
What is Addison disease
1. auto-immune disease affecting adrenal cortex
2. hypo-secretion of cortisol
3. causes increase in ACTH production
4. causes abnormal skin pigmentation, fatigue, weight loss, low blood pressure
75
What is Cushing's syndrome?
1. high cortisol
2. often due to steroid medication or pituitary gland adenoma
3. increased appetite and weight gain
4. increased blood pressure and fluid retention
76
How can testosterone affect speech?
can increase size of thyroid cartilage in larynx -> more prominent adams apple, elongated vocal folds -> lower pitch
77
What does FSH do in females?
Stimulates oestrogen secretion from ovary, and maturation of follicle in menstrual cycle
78
What does LH do in females?
Promotes ovulation and secretion of progesterone from ovary
79
What does FSH do in males?
regulates sperm maturation in testes
80
What does LH do in males?
stimulates testes to secrete testosterone
81
What does testosterone do?
Promotes growth and maturation of reproductive organs and continued sperm production throughout life
82
What does oxytocin do?
Stimulates powerful muscular contractions of uterus in labour, and milk ejection in breastfeeding
Acts as a positive feedback mechanism
83
What does antidiuretic hormone (ADH) do?
1. inhibits urine production by making the kidneys reabsorb more water
2. large amounts constrict arterioles sol increase blood pressure
84
What hormones are produced by the islet of langerhans?
insulin and glucagon
85
What does insulin do?
Binds to muscle and liver cells to make them take up glucose from blood and store it as glycogen
86
What does glucagon do?
Binds to the liver cells causing them to break down glycogen to glucose when blood glucose is low
