The endocrine system Flashcards
1
Q
What does the endocrine system consist of?
A
Endocrine cells and tissues
2
Q
What type of cells are endocrine cells?
A
Epithelial glandular cells surrounded by an extensive network of capillaries
3
Q
What is the difference between endocrine and exocrine cell?
A
Endocrine release hormones directly into the blood stream whereas exocrine release secretions into epithelial surfaces via ducts
4
Q
What is the difference between endocrine tissue and endocrine glands?
A
Endocrine tissues may have other functions apart from hormones secretion however endocrine glands exclusively produce hormones
5
Q
Is the endocrine system slower or faster acting that the CNS?
A
Slower
6
Q
What are the two main divisions of hormones?
A
Lipid-soluble and water soluble
7
Q
What kind of hormones are steroid hormones?
A
Lipid-soluble
8
Q
What kind of hormones are thyroid hormones?
A
Lipid-soluble
9
Q
What kind of hormones are amine hormones?
A
Water-soluble
10
Q
What kind of hormones are peptide hormones?
A
Water-soluble
11
Q
What kind of hormones are protein hormones?
A
Water-soluble
12
Q
What can hormones be generally described as?
A
Chemical messengers
13
Q
What mechanism occurs when hormones reach their target cell?
A
They bind to receptors affecting metabolic or chemical reactions inside the cell
14
Q
Where are the receptors for water-soluble hormones found?
A
On the cell membrane
15
Q
Where are the receptors for lipid-soluble hormones found?
A
Inside the cell
16
Q
Do most hormones work under a positive or negative feedback system?
A
Negative
17
Q
What cellular changes do hormones usually produce?
A
MS MS E
Membrane: changes permeability, potential or both by opening or closing ion channels.
Synthesis: of enzymes and other proteins within the cell.
Mitosis: Stimulation
Secretory activity: Induction
Enzymes: Activation or deactivation
18
Q
What macro processes do hormones affect?
A
Growth
Metabolism
Homeostasis
Development
19
Q
What is the hypophysis?
A
The pituitary gland
20
Q
What is the difference in tissue type between the anterior and posterior pituitary glands?
A
The anterior is an upgrowth of epithelial tissue from the pharynx
The posterior is a down growth of nervous tissue from the brain
21
Q
What is the adenohypophesis?
A
The anterior pituitary gland
22
Q
What is the neurohypophesis?
A
The posterior pituitary gland
23
Q
What structures allow the hypothalamus to communicate with the posterior pituitary gland?
A
A network of nerve fibres
24
Q
What blood supply does the anterior pituitary gland have?
A
An indirect arterial supply that has passed via the capillaries of the hypothalamus
25
Why does the blood supply for the anterior pituitary gland come via the hypothalamus?
To allow hormones from the hypothalamus to reach the anterior pituitary gland directly
26
What are tropic hormones?
Hormones that have other endocrine glands as their target
27
Where are most tropic hormones produced?
The anterior pituitary gland
28
What are the anterior pituitary gland hormones?
Growth hormone
Prolactin
Luteinising hormone (LH)
Follicle stimulating hormone (FSH)
Thyroid stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
29
What is growth hormone?
A protein hormone that stimulates the growth of bone and muscle in growing children. It promotes protein synthesis and fat metabolism and acts as an insulin antagonist.
30
What is prolactin?
A protein hormone that is essential for lactation in the female.
31
What is luteinising hormone?
A glycoprotein that stimulates the production of testosterone in the testis, the ovulation and the secretion of oestrogen and progesterone by the ovary.
32
What is Follicle stimulating hormone (FSH)?
A glycoprotein that stimulates the formation of sperm in the testis and the maturation of the ovarian follicles and oestrogen in the ovary.
33
What is Thyroid stimulating hormone (TSH)?
A glycoprotein that stimulates the synthesis and secretion of thyroid hormones T4 and T3.
34
What is Adrenocorticotropic hormone (ACTH)?
An anterior pituitary gland peptide hormone that stimulates the synthesis and secretion of the glucocorticoid and adrenal androgens (sex hormones) by the adrenal cortex
35
What is the function of the posterior pituitary gland?
It stores hormones produced by the hypothalamus
36
What blood supply does the posterior pituitary gland have?
Direct arterial blood supply from the internal carotid (via the inferior hypophyseal artery)
37
What are the posterior pituitary hormones?
Anti diuretic hormone (ADH)
Oxytocin
38
What is Vasopressin or Anti-Diuretic Hormone (ADH) and when is it released?
A short peptide that is secreted by the posterior pituitary in response to elevated plasma osmolarity (high salt or low water content) or decreased blood volume. It increases the permeability of the distal convoluted tubules and collecting ducts to increase water retention and causes arteriole construction increasing peripheral vascular resistance.
39
What is oxytocin?
It stimulates uterine contraction during labour and the contraction of breast ducts during lactation
40
What gives the thyroid gland its colouration?
The thyroid gland is deep red due to large numbers of blood vessels
41
What is the macrostructure of the thyroid gland?
Two lobes connected by the isthmus covered by a fibrous sheet
42
What are the microstructures of the thyroid gland?
The thyroid gland is formed of small spherical sacs called thyroid follicles. The wall of the follicles consist primarily of cuboidal epithelial cells that are surrounded by a basement membrane. Parafolicular cells (C cells) lie inbetween follicles
43
What hormone affects the follicle cells in the thyroid?
Thyroid stimulating hormone (TSH)
44
Where is thyroid stimulating hormone producted and what stimulates it?
It is produced in the hypothalamus under the stimulating effect of the hypothalamic hormone Thyrotropin-Releasing Hormone (TRH)
45
What are the two thyroid hormones?
Thyroxine (T4)
Tri-iodothyronine (T3)
46
How much of T4 and T3 respectively does the thyroid gland produce?
Mainly T4 and small amounts of T3
47
Where is most T3 produced?
Outside the thyroid gland in other tissues such as liver, kidney and muscle
48
Is T3 or T4 more active?
T3 is much more active
49
What are the main functions of T3 and T4?
Regulate growth, development and reproduction
Stimulate metabolic activities (proteins, carbohydrates and fats) Energy production and utilisation
Increase sensitivity of the cardiovascular and nervous system to adrenaline and noradrenaline
50
What are parafollicular cells?
C-cells. Cells in the thyroid gland that lie inbetween the follicles.
51
What is calcitonin?
A thyroid hormone that lowers blood calcium levels by promoting the storage of calcium in bone tissue and inhibiting it's re absorption in the kidneys
52
What are the parathyroid glands?
Two pairs (four in total) of tiny rounded masses of tissue embedded in the posterior surfaces of the thyroid gland.
One superior and one inferior parathyroid gland are attached to the right and left thyroid lobes.
53
What cells do the parathyroid glands contain?
Two types of epithelial cells, the more numerous chief cells which produce Parathyroid Hormones (PTH), and another form of cells which have an unknown function
54
What is the main function of PTH?
To increase blood calcium levels (opposite to the action of calcitonin of the thyroid gland). This is achieved by increasing the calcium absorption from the small intestine and calcium reabsorption from the kidney tubules. It also releases calcium from bones into the blood by stimulating osteoclasts (bone-destroying cells).
55
What is the structure of the adrenal glands?
Adrenal medulla and cortex surrounded by a capsule. Highly vascular
56
What is the internal structure of the adrenal medulla?
Three different zones the outer, middle and inner
57
What does the outer zone of the adrenal medulla produce?
Mineral corticoids
58
What does the middle zone of the adrenal medulla produce?
Glucocorticoids
59
What does the inner zone of the adrenal medulla produce?
Androgens
60
What are androgens?
Sex hormones
61
What is kind of hormone is aldosterone?
Mineralcorticoid steroid hormone
62
What is the action of aldosterone?
It encourages sodium reabsorption, water retention and potassium excretion
63
What levels stimulates aldosterone secretion?
High blood potassium
64
Where is aldosterone synthesised and secreted?
The outer layer of the adrenal cortex, the zona glomerulosa
65
What is the RAAS?
The renin-angiotensin-aldosterone system (RAAS) is a well known regulator of blood pressure (BP) and determinant of target-organ damage. It controls fluid and electrolyte balance through coordinated effects on the heart, blood vessels, and Kidneys.
66
What class of hormones are cortisol, corticosterone and cortisone?
Glucocorticoids
67
What controls the secretion of glucocorticoids (e.g. cortisol) from the adrenal gland?
Adrenocorticotropic hormone (ACTH)
68
What are the main effects of glucocorticoids (cortisone and hydrocortisone)?
Glucose formation
Lipolysis
Stimulating protein catabolism
Promoting sodium and water retention
Suppression of immune responses
Delayed wound healing
69
Where are weak sex hormones secreted?
By the adrenal cortex in both males and females, in small amounts
70
Where does the adrenal cortex originate from?
It is a modified sympathetic ganglion of the ANS, with the same embryonic origin
71
What will an extensive sympathetic stimulation of the adrenal medulla cause?
The release of adrenaline and noradrenaline
72
In what proportion does the adrenal medulla release adrenaline and noradrenaline?
80% adrenaline
20% noradrenaline
73
What is the structure of pancreatic tissue?
Clusters of pancreatic acini with pancreatic islets scattered within. Abundant capillaries serve both types of tissue.
74
What is the distribution of acini and islets in the pancreas?
99% acini, 1% islets
75
What is the endocrine tissue of the pancreas?
Islets
76
What is the exocrine tissue of the pancreas?
Acini
77
What is the function of pancreatic acini?
They produce digestive enzymes that are secreted into the GI tract through the pancreatic duct
78
What types of cells are present in pancreatic islets?
Alpha (A)
Beta (B)
Delta (D)
F
79
What is the function of pancreatic A cells?
Glucagon secretion
80
What is the function of pancreatic B cells?
Insulin secretion
81
What is the function of pancreatic D cells?
Somatostatin secretion
82
What is the function of pancreatic F cells?
Pancreatic polypeptide secretion
83
Where is somatostatin produced?
GI tract
Pancreas
Hypothalamus
CNS
84
What is the function of somatostatin?
Inhibiting the secretion of both insulin and glucagon from the pancreas.
Inhibiting the secretion of of growth hormone (GH) from the anterior pituitary
85
What does insulin enhance?
Oxidation and energy generation
86
What does insulin increase?
Glycogenesis (formation of glycogen)
87
What does insulin accelerate?
Protein synthesis and lipogenesis
88
What does insulin decelerate?
Glycogenolysis and gluconeogenesis
89
How does insulin drop blood glucose?
-Enhancing oxidation and energy generation
-Increasing glycogenesis
-Accelerating protein synthesis
-Accelerating lipogenesis
-Decelerating glycogenolysis
-Decelerating gluconeogenesis
90
What are examples of insulin antagonists?
Glucagon, adrenaline, cortisol and growth hormone all have insulin-antagonist effects
91
How do insulin antagonists counter its effects?
Acting on the liver cells to speed glycogenolysis
Acting on the muscles to speed gluconeogenesis
92
What are the gonads?
Male and female reproductive organs.
Ovaries and testes.
93
What is the function of the gonads?
Gamete and hormone production
94
What steroids do the ovaries produce?
Several steroid hormones including oestrogens and progesterone
95
What is the purpose of female sex hormones?
Regulation of menstrual cycle, maintaining pregnancy, preparing mammary glands for lactation, development and maintenance of secondary sex characteristics
96
What is the main hormone produced in the testes?
Testosterone
97
What is the function of testosterone?
Stimulate descent of testes, regulation of sperm production, development and maintenance of secondary sex characteristics
98
Where is the pineal gland located?
Attached to the third ventricle of the brain at the midline, part of the epithalamus
99
How does the pineal gland develop?
Develops normally until after puberty when it tends to atrophy and my be calcified in later life
100
What is the main hormone of the pineal gland?
Melatonin
101
What are the functions of melatonin?
Not exactly know but believe to be involved in:
Circadian and diurnal rhythm of many tissues
Inhibition of growth and development of sex organs before puberty
102
Does the endocrine system make precise or approximate adjustments?
Precise
103
Which type of hormones have longer half lives and why?
Lipid-soluble as they must be transported by carrier proteins and their receptors lie inside cells.
They must be released from their transport proteins and then diffuse through the cell membrane
104
Why are steroid proteins lipid-soluble and not water-soluble?
They are built around a cholesterol core and uncharged
105
Why are steroid proteins lipid-soluble and not water-soluble?
They are built around a cholesterol core and uncharged
106
Why are thyroid hormones lipid-soluble and not water-soluble?
They contain benzene rings which increase lipid-solubility and iodine atoms which decrease water-solubility
107
Why are amine, peptide and protein hormones water-soluble and not lipid-soluble?
They are charged molecules which attract "spheres of hydration" and allow them to flow through water as a larger and therefore less lipid-soluble structure
108
How does the hypothalamus transport hormones to the posterior pituitary?
Via a bridge of nerve axons called the hypothalamic–hypophyseal tract
109
What stimulates the release of thyrotropin releasing hormone (TRH)?
Insufficient levels of thyroid hormone being available for the brain
110
What do parafollicular cells do?
Produce Calcitonin
111
What are pancreatic islets also known as?
Islets of Langerhans
112
What are glucocorticoids named after?
Their roles in maintaining glucose homeostasis
113
What are mineralcorticoids named after?
Their roles in maintaining electrolyte balance
114
How is calcium homeostasis maintained?
