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Veterinary Nursing VN07 > The endocrine system > Flashcards

The endocrine system Flashcards

1
Q

What is the endocrine system?

A

A system within the body responsible for maintaining the homeostatic balance. It releases hormones to tell certain parts of the body how to react to changing internal and external conditions. A single hormone may have effects on multiple tissues or organs, and may be long acting.

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2
Q

Define AUTOCRINE

A

Relating to a hormone that influences the original cell that produced it. An example is secretin in the small intestine

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3
Q

What is homeostatic balance?

A

The self regulating process by which biological systems maintain stability whilst adjusting to optimal conditions

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4
Q

Define ENDOCRINE

A

Relating to a hormone that is transported in the blood stream to the target organ e.g. ACTH or insulin

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5
Q

Define EXOCRINE

A

Relating to a hormone that is released through a duct. The substances do not need to travel via the blood stream e.g. sebaceous glands, lacrimal glands, and sudoriferous glands

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6
Q

Define PARACRINE

A

Relating to a hormone that influences local cells e.g. the neurotransmitters of the nervous system, dopamine and acetylcholine

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7
Q

Define a HORMONE

A

A chemical transmitter (a signalling molecule) produced by cells f the body and transported via the blood stream to the cells and organs on which it has a specific regulatory effect

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8
Q

What are hormones made of?

A

They are a form of protein, and are made from amino acid derivatives, fatty acids, and steroids

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9
Q

Describe an endocrine gland

A

They secrete their hormones straight into the bloodstream, and are ductless

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10
Q

What are examples of the endocrine glands?

A

The pituitary gland, the thyroid gland, the parathyroid glands, the pancreas, the ovaries, the testes, the adrenal glands and the pineal gland

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11
Q

What is the role of the pineal gland?

A

It releases melatonin, which can affect mood in darker months. It helps to set circadian rhythm, manage the length of day and the seasons of the animal. It informs breeding decisions via this

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12
Q

What is the pituitary gland?

A

‘The master gland’ - as it influences so many other endocrine glands. It is a small, round body, roughly bean sized, connected to the hypothalamus in the brain by a stalk. It has two lobes, the anterior and posterior, and send out signals to other glands to produce their own hormones

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13
Q

What is the pituitary gland also known as?

A

The hypophysis

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14
Q

What is the anterior pituitary gland?

A

Also called the adenohypophysis. The lobe of the pituitary gland that sits cranially - it originates from the roof of the mouth but loses its connection during embryological development. It produces 7 hormones.

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15
Q

What is the anterior pituitary gland also known as?

A

Adenohypophysis

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16
Q

What is the posterior pituitary gland?

A

Also called the neurohypophysis. It sits caudally - it originates from the hypothalamus of the forebrain and retains its connection with the brain. It secretes two hormones that are produced in the hypothalamus

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17
Q

What is the posterior pituitary gland also known as?

A

The neurohypophysis

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18
Q

What is the hypothalamic hypophyseal portal system?

A

A network of capillary blood vessels that lead from the hypothalamus to the anterior lobe of the pituitary gland. The hypothalamus uses this system to secrete substances called releasing factors which influences the action of the anterior pituitary gland

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19
Q

What hormones are produced by the anterior pituitary gland?

A

There are 7 in total:
- somatotrophic (growth) hormone
- thyroid stimulating hormone
- adrenocorticotropic hormone
- follicle stimulating hormone
- luteinizing hormone
- prolactin
- interstitial cell stimulating hormone

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20
Q

What is somatotrophic hormone?

A

Also called growth hormone, it is produced by the anterior pituitary gland. It does not have a target gland or organ. It controls growth of bones, muscles and the amount of energy required for newly growing animals.

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21
Q

What is the result of a lack of STH?

A

Pituitary dwarfism, which results in a lack of growth. May be hereditary, or may be a result of a tumour or similar on the pituitary gland

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22
Q

What is the result of excess STH?

A

A condition called acromegaly - results in enlarged bones in the face, feet and hands

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23
Q

What is thyroid stimulating hormone?

A

Produced by the anterior pituitary gland. Stimulates the thyroid to produce two different hormones: T3 (tri-iodothyronine) and T4 (thyroxin)

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24
Q

What is adrenocorticotrophic hormone?

A

Produced by the anterior pituitary gland. It stimulates the adrenal cortex to release hormones

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25
What is follicle stimulating hormone?
Produced in the anterior pituitary gland. It stimulates the ovaries to develop into a follicle, containing an egg (ova)
26
What is luteinizing hormone?
Produced by the anterior pituitary gland. It affects the follicles of the ovaries - helps them to 'ripen and rupture'. It also helps with ovulation
27
What is prolactin?
A hormone produced by the anterior pituitary gland. Helps during gestation and maintaining pregnancy. It helps mammary development and milk production, however milk cannot be released without the presence of oxytocin
28
What combination of hormones must be present to allow the production and let down of milk in a pregnant animal?
Prolactin will help with mammary development and milk production but the milk cannot be released without oxytocin
29
What is interstitial cell stimulating hormone?
Produced by the anterior pituitary gland. It is the male equivalent to LH. It stimulates the cells of Leydig to release testosterone from the testes
30
Describe the posterior pituitary gland
The caudal aspect of the pituitary gland. It lacks glandular tissue and does not produce its own hormones, only storing and releasing the ones that are produced by the hypothalamus
31
What two hormones are released by the posterior pituitary gland?
Oxytocin and anti-diuretic hormone (ADH)
32
What is oxytocin?
A hormone released from the posterior pituitary gland that enables the let down of milk, and encourages uterine contraction. Also affects maternal bonding and nurturing behaviour
33
What is anti-diuretic hormone?
A hormone released from the posterior pituitary gland that regulates the reabsorption of water from the distal tubule and the collecting ducts in the nephron in the kidney. It also causes contraction of the smooth muscle of the blood vessels, causing an increase in BP
34
What is an ADH deficiency?
Also called diabetes insipidus - it is a decreased reabsorption of water in the kidneys. Therefore a large volume of urine is produced and the animal cannot concentrate its urine. Water must be replaced sufficiently or the animal will become dehydrated and die
35
What is ADH also known as?
Vasopressin - this is because of its ability to contract the smooth muscle of blood vessels to raise BP
36
Describe the thyroid gland
It is a gland made up of two lobes that wrap around and sit either side of the trachea. It contains follicular and parafollicular cells which each produce their own hormones. Under secretion of the thyroid gland results in hypothyroidism; over secretion of the thyroid gland results in hyperthyroidism
37
What are follicular cells?
Cells within the thyroid gland which produce T3 and T4.
38
What is produced by follicular cells?
T4 (thyroxin) and T3 (tri-iodothyronine), both hormones
39
What is the role of iodine in relation to the endocrine system?
It is an important raw material in the production of thyroxin (T4) and adequate amounts are essential in the diet of both cats and dogs
40
What are parafollicular cells?
Also called c-cells. They are found in the thyroid gland and produce thyrocalcitonin
41
What is thyrocalcitonin?
A protein hormone which is produced by the c-cells (parafollicular cells) of the thyroid, It has the opposite effect of parathyroid hormone, and lowers the levels of calcium in the blood, and increases the deposition of calcium and phosphate into bone. Without the presence of calcium, the hormone goes crazy
42
What is produced by parafollicular cells?
Thyrocalcitonin - a protein hormone that lowers the levels of calcium in the blood, increasing deposition of calcium and phosphate into bone. It acts as the opposite to parathormone
43
What are the effects of T4 and T3?
Together they: - stimulate metabolic rate - stimulate heart rate - increase blood pressure - increase the activity of the nervous system
44
What is T4?
Thyroxin - produced by the thyroid gland, and works with T3 (tri-iod to control various functions within the body
45
What is T3?
Tri-iodothyronine - a hormone produced by the thyroid gland. It works with T4 (thyroxin) to control various functions within the body
46
What is metabolic rate?
The rate at which metabolism occurs in a living organism
47
How does the negative feedback system of the thyroid work?
External factors such as environmental temperature stimulate the hypothalamus, which causes the anterior pituitary gland to release TSH, which stimulates the thyroid to release T4 and T3 into the blood stream. These increase the metabolic rate which raises the animal’s temperature. This increase in T4 and T3 inhibits the anterior pituitary gland’s production of TSH and the releasing factors produced by the hypothalamus.
48
What species is hypothyroidism most common in?
Dogs
49
What species is hyperthyroidism most common in?
Cats
50
What are the parathyroid glands?
Pea sized glands that sit within the thyroid tissue. They produce parathormone, and their secretary activity is controlled directly by the levels of calcium ions in the blood stream
51
What is produced by the parathyroid glands?
Parathormone, also know as parathyroid hormone. It is produced in response to low levels of blood calcium levels.
52
What are the actions of parathormone?
Involved in the regulation of phosphorus and calcium
53
What is another name for parathormone?
Parathyroid hormone
54
What can happen if there is not enough calcium in circulation, in relation to the parathyroid gland?
The parathyroid will seek calcium from other sources within the body and start to strip calcium deposits, such as from bone, which can result in osteoporosis
55
What is osteoporosis?
Brittle bone disease - the bones lack calcium, are weaker, and are more susceptible to fractures
56
What are the adrenal glands?
A pair of structures that sit near the upper poles of the kidney. Also known as the suprarenal glands. The cortex within them produces a range of steroid hormones, and also androgens, the sex hormones
57
What is the make up of the adrenal glands?
There is an outer cortex, which is controlled by ACTH, and an inner medulla, which is controlled by the sympathetic nervous system, meaning it is involuntary
58
What is the adrenal cortex?
A part of an adrenal gland. It is an essential part of life, and is divided into three zones/layers: the zona glomerulosa, the zona fasciculata, and the zona reticularis
59
What are the three layers of the adrenal cortex?
The zona glomerulosa (the outermost layer) The zona fasciculata (the middle layer) The zona reticularis (the inner layer)
60
What are the three categories of hormones produced by the adrenal cortex?
Glucocorticoids, mineralocorticoids, androgens
61
What is the role of glucocorticoids?
Involved in the promotion of gluconeogenesis, which can be linked to DM. Also involved in wound repair and haling inhibition. Can also be used to reduce inflammation, and for skin issues such as dermatitis or pruritis. Can give the animal increased resistance to stress but dampen down the immune system
62
What is gluconeogenesis?
The breakdown of protein and the resynthesis of the breakdown products into glucose. Glucocorticoids produced by the adrenal cortex play a vital role in this process.
63
What are some examples of glucocorticoids?
Cortisol and cortisone
64
What is the result of an oversecretion of glucocorticoids?
Cushing's disease (hyperadrenocorticism)
65
What are some clinical signs of Cushings disease?
Muscle atrophy, ascites, alopecia, PU/PD
66
What is the effect of an undersecretion of glucocorticoids?
Addisons disease - hypoadrenocorticism
67
What are some of the clinical signs of Addison's disease?
Vomiting, diarrhoea, bradycardia, lethargy and potentially collapse
68
What is the role of mineralocorticoids?
The main one is aldosterone, which controls the levels of electrolytes in plasma. It also stimulates the retention of water and sodium by the kidney tubules, and promotes the excretion of potassium. It also controlled BP by stimulating the cells in the kidneys to create renin when BP is low
69
What is an example of a mineralocorticoid?
Aldoesterone
70
What is the process of the kidneys raising BP?
Renin is secreted from the kidneys - Renin activates angiotensinogen, which converts to angiotensin 1, then angiotensin 2, which is a vasoconstrictor, which raises blood pressure
71
What is the role of androgens?
They are the adrenal sex steroids - they are thought to control sex drive in both males and females
72
What is the adrenal medulla, and what is its role?
A part of the adrenal gland, it is a group of modified nerve cells which secret adrenaline and noradrenaline. Both are neurotransmitters and catecholamines, alongside dopamine.
73
What is noradrenaline?
The main neurotransmitter, that helps the body respond to stress
74
What is adrenaline?
The main hormone secreted by the adrenal medulla; it stimulates the fight or flight response
75
What is the pancreas?
A v-shaped organ found in the anterior abdomen alongside the stomach and duodenum. It has both endocrine and exocrine functions. It produces 3 different types of hormones
76
What are the Islets of Langerhans?
Found in the pancreas - they are cell clusters that are made up of three different types of cells, which in turn produce three different hormones
77
What are the three types of cells that exist within the pancreas?
Alpha cells - they produce glucagon Beta cells - they produce insulin Delta cells - they produce somatostatin
78
What are alpha cells and what do they produce?
They are cells found within the pancreas that produce glucagon, which increases blood glucose
79
What are beta cells and what do they produce?
They are found within the pancreas and produce insulin, which decreases blood glucose
80
What are delta cells and what do they produce?
They are found within the pancreas and produce somatostatin, which helps with the body's balance and homeostatic mechanism. It also helps to prevent the overproduction of insulin
81
What are the gonads?
The ovaries in females, and the testes in males
82
Describe the testes
The gonad in the male. They produce testosterone from Leydig cells (interstitial cells) and oestrogens from Sertoli cells
83
What hormones are produced by the testes?
Testosterone, from the Leydig cells (interstitial cells) Oestrogens from the Sertoli cells
84
What are Leydig cells?
Cells within the testes that are responsible for the production of testosterone. Also called interstitial cells
85
What is the role of testosterone?
It stimulates the development of male characteristics and maturation of the sperm producing tubules
86
What are Sertoli cells?
Cells within the testes which are responsible for the production of oestrogens
87
What is the role of oestrogens within the testes?
To develop and nourish sperm
88
What is the effect of a Sertoli cell tumour and where would it be found?
Would be found within the testes, and causes feminisation of the male
89
What hormones are produced by the ovaries?
Oestrogen, progesterone and relaxin
90
What is the role of oestrogen?
In females, it prepares the genital tract and genitalia for mating and receiving conceptus. It is released in the ovary. In males it is released from the testes to help nourish sperm
91
Where is oestrogen released from?
The ovarian follicles in the ovary, specifically called the Graafian follicles, into the blood
92
What is the role of progesterone?
Maintains pregnancy and affects the uterus and mammary glands. It is released from the ovary
93
What is the role of relaxin?
It is released from the ovary in late pregnancy, and is stimulated by the foetus. Causes ligaments around the pelvis to relax during parturition. If released too early in pregnancy it can cause muscle and joint pain
94
What is parturition?
The act of giving birth
95
What is gastrin and what is its role?
A hormone that is produced by the lining of the stomach - it stimulates the release of gastric juices from the gastric glands to begin digestion
96
What is secretin and what is its role?
A hormone produced by the mucosa of the small intestine. It stimulates the secretion of intestinal and pancreatic juices to continue the process of digestion
97
What is erythropoietin and what is its role?
A hormone produced by the kidneys that stimulates bone marrow to produce erythrocytes. Also called erythropoietic stimulating factor
98
What is cholecystokinin and what is its role?
A hormone that is secreted by the cells of the duodenum. Its secretion is stimulated by the introduction of hydrochloric acid, amino acids or fatty acids into the stomach or duodenum. It stimulates the gallbladder to contract and release stored bile into the intestine as well as stimulating the secretion of pancreatic juice. It may induce satiety as well
99
What is chorionic gonadotrophin and what is its role?
A hormone produced by the placenta. It prevents disintegration of the corpora lutea, thereby maintaining progesterone production that is critical for pregnancy. It has a positive feed back system, one of the only ones in the body
100
What are some examples of hormones that are not secreted by endocrine glands?
Chorionic gonadotropin, cholecystokinin, erythropoietin, secretin, and gastrin

Veterinary Nursing VN07 (13 decks)

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