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Human Endocrine Systems Flashcards

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1
Q

Exocrine Glands

A

Both the salivary glands and sweat glands are known as Exocrine Glands because they have ducts. These ducts carry their secretions to where they are needed.

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2
Q

Endocrine Glands

A

Some glands produce secretions which have to be transported for use far away from the gland itself. Glands such as these pour their secretions directly into the blood. These glands, which do not have ducts, are called endocrine glands. These secretions of the endocrine glands are called hormones.

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3
Q

Thyroid Glands and Adrenal Glands

A

The thyroid gland, in the neck region, secretes the hormone thyroxin into the blood.

The adrenal gland, found above the kidney, secretes the hormone adrenalin into the blood.

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4
Q

Pancreas

A

When the pancreas secretes pancreatic juice, which is carried to the duodenum by means of the pancreatic duct, it functions as an exocrine gland.

When special tissues inside the pancreas (called the islets of Langerhans) secrete the hormones insulin or glucagon, directly into the blood, it functions as an endocrine glands.

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5
Q

Hormones

A

Hormones are organic chemical messengers which are mostly proteins in nature.

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6
Q

Properties of Hormones

A

They do not ac independently but form an integrated system bringing about co-ordination and homeostasis through specific effects on organs.
They control a wide variety of functions, including growth and reproduction.
Hormones are secreted in small amounts directly into the blood, which transports them to the organs they stimulate. These organs are called target organs.

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7
Q

Some important Endocrine Glands

A

The Endocrine System is made up of many glands that are located in various parts of the body.

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8
Q

The Hypothalamus

A

The Hypothalamus is found on the underside of the brain. It produces the anti-diuretic (ADH). This hormone is stored in, and released from, the pituitary gland. In this way, the hypothalamus plays an important role in linking the nervous system with the endocrine system.

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9
Q

ADH secretion on a Hot Day

A

ADH is secreted in large amounts, increasing the permeability of the walls of the distal convoluted tubule and collecting tubule.
More water leaves the tubules and enters the medulla oblongata from where it is reabsorbed by blood capillaries.
In this way excessive water loss from the blood is prevented.

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10
Q

ADH secretion on a Cold Day

A

ADH secretion is decreased, thus decreasing the permeability of the walls of the distal convoluted tubule and collecting tubule.
Less water leaves the tubule and the water that remains in the tubule is lost in the form of dilute urine.
In this way excess water is lost from the body.

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11
Q

The Pituitary Gland/ Hypophysis

A

The Pituitary Gland/Hypophysis is a small (pea-sized) gland situated in a bony cavity at the base of the brain. It is attached to the hypothalamus of the brain.

The pituitary gland is made up of two lobes, the anterior lobe and the posterior lobe. Both lobes produce many important hormones. Some of these hormones control other endocrine glands. The pituitary gland is therefore sometimes called the “master gland”.

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12
Q

Hormones produced by the pituitary gland

A

Growth Hormone
Thyroid Stimulating Hormone (TSH)
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH) in females
Prolactin

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13
Q

Growth Hormone

A

This hormone is essential for the growth and development of the skeleton and muscles and thus the body as a whole.

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14
Q

Effects of Over-secretion/ Under-secretion of the Growth Hormone in childhood.

A

If too much of this hormone is secreted (Over-secretion) in childhood then the muscles and bones will grow very much faster than normal. The child will grow into a ‘giant’. This condition is called gigantism.

If too little of this hormone is secreted (Under-secretion) during childhood, then the bones and muscles will grow very slowly and the child will develop into a very small adult. This condition is called dwarfism. The mental development of such dwarfs is not affected.

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15
Q

Effects of Over-secretion/Under-secretion of the Growth Hormone during adulthood.

A

Over-secretion of the growth hormone during adulthood, results in the bones of the hands ad legs (especially the fingers and toes) and the face (especially the chin), becoming enlarged. This condition is known as acromegaly.

Under secretion of the growth hormone during childhood has little or no effect on the body.

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16
Q

Thyroid Stimulating Hormone (TSH)

A

The thyroid stimulating hormone (TSH) stimulates the thyroid gland to secrete the hormone thyroxin. Increased production and release of TSH into the blood will therefore lead to an increased in thyroxin production and vice versa.

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17
Q

Follicle Stimulating Hormone (FSH)

A

In females, this hormone controls the production of ova (eggs) in the Graafian Follicle of the ovary. FSH reaches its highest concentration at the time of ovulation. FSH is also produced in males where it controls the development of sperms.

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18
Q

Luteinizing Hormone (LH) in females

A

Luteinizing Hormone has three basic functions as follows:
Controls the release of the egg from the follicle during ovulation.
Causes the Graafian Follicle to become the corpus luteum after ovulation.
Stimulates the Graafian Follicles to produce oestrogen.

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19
Q

Prolactin

A

This hormone stimulates the production of milk by the mother. This process of milk production is called lactation.

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20
Q

The Thyroid Gland

A

The thyroid gland is an H-shaped land consisting of two lobes, on either side of the trachea just below the larynx.

When the pituitary gland secretes Thyroid Simulating Hormone (TSH), the thyroid gland is stimulated tp secrete thyroxin.

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21
Q

Functions of Thyroxin:

A

It regulates the metabolic rate. For example, when more energy is required, thyroxin increases the rate of oxidation of glucose in the cells.
It affects the growth and functioning of the heart and nervous system.

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22
Q

Iodine

A

Iodine is essential for the production of thyroxin. We obtain this iodine from the food we eat and from the water we drink. When we do not take in sufficient iodine, our thyroid glands enlarge to form a swelling referred to as goitre.

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23
Q

Under Secretion of Thyroxin

A

Sometimes, the thyroid gland produces insufficient amount of thyroxin. This Under-secretion of thyroxin is called hypothyroidism. The main symptom of under secretion of thyroxin is a low metabolic rate.

24
Q

Low Metabolic Rates in children

A

In children, this low metabolic rate causes slow skeletal development (so that the child becomes a dwarf) and a slow mental development. In addition, the skin becomes thick and dry and the tongue enlarges and sticks out of the mouth. This condition is called cretinism.

25
Q

Low Metabolic Rate in adults

A

Once a person has already grown into and adult, a low metabolic rate as a result of hyperthyroidism cannot slow down skeletal or mental growth. It does, however, n addition, the skin becomes thick and dry and the person’s mass may increase. This condition is called myxoedema.

26
Q

Over Secretion of Thyroxin

A

Sometimes the Thyroid Gland produces too much thyroxin. This over-secretion of thyroxin is called hyperthyroidism.

27
Q

Symptoms of Over-Secretion of Thyroxin

A

An increased metabolic rate, which in turn leads to hyperactivity and nervous tension.
The development of a different type of goitre which results in protrusion (sticking-out) of the eyes.

28
Q

The Adrenal Glands

A

The adrenal gland is a pair of small glands one on top of each kidney. Like the kidney, each adrenal gland is made up of an adrenal cortex and an adrenal medulla. The adrenal cortex secretes the hormone aldosterone and the adrenal medulla secretes the hormone adrenalin.

29
Q

Functions of Aldosterone

A

Regulates the amount of salt in the blood
Works with ADH to bring about water balance.

30
Q

Shortage of sodium in the blood

A

When there is an shortage of sodium in the blood, the adrenal cortex secretes more aldosterone and more sodium is reabsorbed by the capillaries around the distal and collecting tubules. Less sodium ions are excreted in the urine.

31
Q

Excess of sodium in the blood

A

When there is an excess of sodium ions in the blood, aldosterone secretion decreases and les sodium is reabsorbed by the capillaries around the distal and collecting tubules. This allows more sodium to be lost in the urine.

32
Q

Over-secretion of aldosterone

A

Over-Secretion of aldosterone causes too much salt to be retained by the blood. This is turn causes lots of water to be retained by the various tissues. These tissues begin to swell, causing a condition called oedema.

33
Q

Adrenalin

A

The medulla of the adrenal gland secretes the hormone adrenalin. Adrenalin prepares the body to meet emergencies, whenever danger threatens.

34
Q

Flight or Fight

A

We need to think clearly and our muscles need additional strength for quick and forceful action. This means that extra energy needs to be supplied to our brain and muscles of the skeletal system and this must be done quickly.
The metabolic rate in our brain and in our skeletal muscles must increase so that they get more energy very quickly. For the metabolic rate to increase we need: More Glucose, More Oxygen, More Thyroxin.
The thyroid gland needs to secrete more thyroxin.
The heart needs to beat faster to supply more oxygen and glucose quickly to the brain and skeletal muscles. However, before this can happen the following must take place: Glucose needs to be converted to Glycogen in the liver and the breathing rate needs to increase so that we can get more oxygen.

35
Q

Functions of Adrenalin

A

Increases the rate and depth of breathing so that more oxygen is obtained quickly.
Causes the liver to convert more glycogen to glucose which is then released into bloodstream.
Increases the rate of the heart beat and the blood pressure so that blood (with oxygen, glucose and thyroxin) can be carried quickly to the skeletal muscles and brain.
Causes the blood vessels of the muscles, heart and brain to dilate so that more blood can be taken to these parts.
Causes the blood vessels of the digestive system and skin to constrict so that less blood is sent to these parts and more blood becomes available for the heart, brain and skeletal muscles.
Increases the metabolic rate of cells in the brain and skeletal muscles so that more energy is released for muscular activity and clear thought.
Increases the tone of the skeletal muscles so that they can function more effectively.

36
Q

Insulin

A

The hormone insulin is mainly responsible for lowering the glucose level of the blood, whenever the glucose level is to high. Insulin reduces the blood glucose level in the following ways:
Promotes the absorption of glucose into cells, for use in cellular respiration.
Stimulates the liver and muscles to convert glucose to glycogen, for storage in the liver and muscles.

37
Q

Shortage of insulin

A

In some persons, there is a shortage of the hormone insulin, because of disease or damage to the cells of the islets of Langerhans. In some other cases, the quality of the insulin produced is very poor. Both types of people do not have the ability to reduce their blood glucose levels when it becomes to high. We say that they suffer from diabetes mellitus.

38
Q

Symptoms of Diabetes Mellitus

A

Abnormally high blood glucose levels.
Excretion of glucose in the urine (the kidney tries to reduce the glucose level by getting rid of some glucose with the urine).

39
Q

Glucagon

A

The hormone glucagon has the opposite effect to insulin. When the blood sugar is low and in emergency situations, it increases the blood glucose level by converting stored glycogen from the liver or muscles, into glucose.

40
Q

The Ovaries

A

The pituitary gland secretes the follicle stimulating hormone (FSH) and the Luteinizing Hormone (LH). FSH in turn causes the Graafian Follicle to secrete the hormone oestrogen. Later, after ovulation (when the ovum is shed) the Graafian Follicle becomes the Corpus Luteum. The Corpus Luteum secretes the hormone progesterone.

41
Q

Oestrogen

A

Oestrogen is a hormone that is released throughout the lifetime of a female.

42
Q

Functions of Oestrogen

A

Responsible for development of girls into sexually matured individuals. This involves the development of secondary sexual characteristics in girls such as the development of breasts and a widening of the pelvic girdle.
Starts the preparation of the uterus for pregnancy by making it thicker, more vascular and more glandular.

43
Q

Progesterone

A

The Corpus Luteum produces progesterone which is responsible for the following:
Ensuring that the uterus wall is fully developed to allow for the implantation of the fertilized egg into the wall of the uterus.
Ensuring that the uterus wall is maintained in that state during the entire period of pregnancy.
Inhibits the production of FSH by the pituitary gland so that no further eggs are produced during pregnancy.

44
Q

The Testes

A

A pair of oval testes lies in a bag-like scrotum outside the abdominal cavity. Numerous, coiled seminiferous tubules occur inside each testes.

45
Q

Testosterone

A

Special interstitial cells in the walls of the seminiferous tubules secrete the hormone testosterone. Testosterone is responsible for the development of boys into sexually matured individuals. This involves the development of secondary sexual characteristics in boys such as a muscular physique and hair on the chest.

46
Q

Feedback Mechanisms

A

Most living organisms are capable of homeostasis. In other words, they are able to keep their internal environment more or less constant, irrespective of changes in the external environment. Homeostasis is brought about by negative feedback mechanisms.

47
Q

The basic Principle of Negative Feedback (Too High)

A

When the hormone level in the blood is too high, this is reported back to the endocrine gland. The endocrine gland then reduces the production of the hormone. The hormone level of the blood comes back to normal.

48
Q

The Basic Principle of Negative Feedback (Too Low)

A

When the hormone level in the blood becomes too low, the process is reversed. In other words, the message is fed-back to he endocrine gland and the endocrine gland then increases the production of the hormone. The hormone level of the blood returns to normal once again.

49
Q

Negative Feedback

A

When the levels of hormone is too high, the endocrine gland reduces its production and when it is too low, the production is increased. In other words, the endocrine gland works in the opposite or “negative” direction to the level of the hormone. That is why it is called ‘negative’ feedback.

50
Q

Negative Feedback: Control of Thyroxin Levels

A

When controlling the level of Thyroxin in our blood, both the pituitary and thyroid glands are involved. The pituitary glands is very sensitive to the amount of thyroxin in the blood.

When the thyroxin levels of the blood is too high, the pituitary gland secretes little TSH. Little or no thyroxin is secreted and the thyroxin level is thus reduced to normal limits.

51
Q

Negative Feedback: Control of Blood Sugar Levels

A

Two hormones, insulin and glucagon, secreted by the islets of Langerhans in the pancreas, control the concentration of the glucose level of the blood.

52
Q

When the blood sugar level is higher than normal

A

When the blood sugar level is higher than normal, the hormone insulin is secreted. Insulin reduces the blood sugar level in two ways:
It increases the rate at which glucose is absorbed by the cells, especially the cells of the liver and muscles.
It stimulates the conversion of glucose into glycogen and fat in the liver and muscles.

53
Q

When the blood sugar level if lower than normal

A

When the blood sugar level is lower than normal, the hormone glucagon is secreted. Glucagon increases the blood sugar level by stimulating the conversion of glycogen to glucose for release into the bloodstream.

54
Q

Type 1 Diabetes

A

Type 1 diabetes occurs when the pancreas stop producing insulin. It usually starts in young people under the age of 30. People who have type 1 diabetes must inject insulin to survive.

55
Q

Type 2 Diabetes

A

Type 2 diabetes is caused when the insulin, which the pancreas produces, is either not enough or does not work properly. Most type 2’s are over 40. They are usually overweight and do not exercise. Type 2 diabetes may be treated successfully without medication. Tablets may be prescribed to help improve control, however, many type 2 patients will eventually use insulin.

56
Q

Symptoms of Diabetes

A

Glucose in the urine
Extreme thirst
Nausea/Vomiting
Blurred vision
Frequent urination
Fatigue/ Lethargy/ Faintness
Weight loss
Non-healing of wounds.

57
Q

Treatment

A

Exercise
Eating a diet suitable for diabetic person
Using prescribed medication/ drugs for management of diabetes mellitus

Biology (42 decks)

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