Chapter 2 - Hormones Flashcards
- Endocrine System - Hypothalamus and Pituitary Gland - Other Endocrine Glands
1
Q
What is the function of Endocrine Glands?
A
To secrete hormones
2
Q
What are some examples of Endocrine Glands?
A
- Pineal Gland
- Hypothalamus
- Pituitary Gland
-Thyroid Gland - Parathyroid gland (usually four)
- Thymus
- Adrenal glands (two)
- Kidneys (two)
- Pancreas
- Ovaries (two) in females
- Uterus in females
- Testes (two) in males
3
Q
What are the two types of Glands in the body?
A
- Exocrine Glands
- Endocrine Glands
4
Q
Where do exocrine glands secrete hormones and where do the hormones go?
A
Secrete into a duct that carries the secretion to the body surface or to one of the body cavities.
5
Q
Where do endocrine glands secrete hormones and where do the hormones go?
A
Secretes hormones into the extracellular fluid that surrounds the cells that make up the gland.
The secretion then usually passes into the capillaries’ to be transported by the blood
6
Q
What are some examples of exocrine glands?
A
Sweat glands, mucous glands, salivary glands and the glands of the alimentary canal
7
Q
What is the difference between exocrine and endocrine glands?
A
Exocrine glands secrete hormones into a duct which transports the hormones, whereas endocrine glands secrete hoemones into the extracellular fluid and the hormones are transported in the capillaries via the blood.
8
Q
What are hormones?
A
Hormones are chemicals, secreted by endocrine glands, that are transported throughout the body in the blood.
9
Q
What do hormones do?
A
They change the functions of the cells by changing the type, activity or quantities of proteins produced.
10
Q
Are hormones enzymes?
A
They ARE NOT enzymes; however, in many cases hormones exert their influence by changing the activity of enzymes or their concentrations.
11
Q
What are the three ways hormones are able to change the functioning of a cell?
A
- Activate certain genes in the nucleus so that a particular enzyme or structural protein is produced
- Change the shape or structure of an enzyme so that is turned ‘on’ and ‘off’
- Change the rate of production of an enzyme or structural protein by changing the rate of transcription or translation during protein production
12
Q
What are hormones able to affect?
A
- All the cells of the body
- Only particular groups of cells, target cells
- Only particular organs, target organs
13
Q
What are the three types of hormones?
A
- Steroid
- Protein
- Amine
14
Q
Describe the process steroid hormones undergo once they are released
A
- Once they are released into the blood, the hormones bind to transport proteins, enabling them to travel in the bloodstream.
- When they reach the target cells, the steroid hormones separate from the transport proteins and diffuse across the cell membrane.
- Inside the cell they work by combining with a receptor protein in the cytoplasm or nucleus.
- The hormone-receptor complex activates the genes controlling the formation of particular proteins. It does this by binding to the promoter section of a certain gene, stimulating (or inhibiting) transcription and, therefore, protein synthesis
15
Q
How long does it take for steroid hormones to take effect and how long does the effect last for?
A
They are slow to have an effect, but the effect is long lasting
16
Q
What type of molecules are steroid hormones?
A
They are all lipid-soluble, meaning they DO NOT dissolve in water and are ABLE to diffuse across the cell membrane
17
Q
What are some examples of steroid hormones?
A
- Oestrogen
- Progesterone
- Cortisol
- Aldosterone
18
Q
Describe the process protein and amine hormones undergo once they are released
A
- Once they are released into the blood, the hormones bind to transport proteins, enabling them to travel in the bloodstream.
- Once they reach the target cell, they attach to receptors proteins in the membrane of the target cell
- The combination of the hormone with the receptor causes a secondary messenger substance to diffuse through the cell and activate particular enzymes
19
Q
How long does it take for protein and amine hormones to take effect and how long does the effect last for?
A
They are quick to cause a response, but the effect is short lasting
20
Q
What type of molecules are protein and amine hormones?
A
They are all water-soluble, meaning they DO dissolve in water and are UNABLE to diffuse across the cell membrane
21
Q
What are some examples of protein and amine hormones?
A
- The hormone insulin binds to a receptor protein and this leads to an increase in glucose absorption by the cell
- Prolactin (PRL)
- Growth Hormone (GH)
22
Q
What is meant by the idea that receptor proteins are specific?
A
Each type of receptor will bind with only one specific molecule
23
Q
What analogy can be used to descrube the interaction between the receptor and a molecule?
A
The lock and key analogy
The lock, the receptor protein, will only work with the correct key, the binding molecule.
24
Q
What is meant by the term, “saturation” in regards to receptor proteins and molecules?
A
There are a limited number of receptor proteins in the membrane of each cell.
When each receptor is bound to a molecule, there can be no further increase in the rate of the cells activity.
25
Provide an example of 'saturation'.
When each insulin receptor in the cell membrane is bound to insulin, the cells rate of glucose cannot increase and further, even if the amount of insulin increases. This means that saturation can occur; once all the receptor molecules are occupied by hormone molecules, the addition of more hormones does not produce any greater effect
26
Why is there variation in the sensitivites of cells to hormones and other substances
Because different cells have different types and number of receptor proteins.
27
How many molecules of an enzyme does one hormone molecule cause to be manufactured or activated?
Thousands of molecules, a very small stimulus can producet. a very large effec
28
What happens once a hormone has produced the required effect?
Hormone clearance must occur and the hormone needs to be turned off. This is done by breaking down the hormone molecules
29
Where are the hormones broken down?
Some hormones are broken down in the target cells
Most are broken down in the liver and the kidneys
30
How are the degraded hormones excreted?
The degraded hormones are then excreted in either the bile or the urine.
31
What happens if not enough or to many hormones are secreted by an endocrine gland?
Any over secretion or under secretion of a hormone will cause the body to function abnormally
32
Why is it important to control the amount of hormones being secreted?
To maintain homeostasis
33
How are hormone secretions generally regulated?
By negative feedback systems whereby the response produced by the secretion of the hormone is the opposite of teh stimulus that caused the secretion
34
What would happen if hormone clearances were unable to occur?
If hormone clearance didn’t occur, the hormone would not be able to turn off meaning the target cells would be continuously stimulated to respond, resultiing in an imbalance or positive feedback.
35
What systems does the Hypothalamus have roles in?
The Endocrine and The Nervous System
36
What are the functions of the Hypothalamus?
Regulate many of the basic functions of the human body
Examples; Body temperature, water balance, heart rate, increasing or decreasing the secretions of other glands
37
How does the Hypothalamus carry out its functions?
The hypothalamus secretes releasing factors, which stimulate the secretions of a hormone or inhibiting factors, which slow down the secretion of a hormone. The factors travel through blood vessels to the anterior lobe of the pituitary gland, affecting the secretion of its hormones.
Other hormones are produced by the hypothalamus and pass along the nerve fibres to the posterior lobe of the pituitary gland where they are then released.
38
Where is the Hypothalamus located?
At the base of the brain, below the thalamus and above the pituitary gland
39
How large is the Hypothalamus?
The size of an almond
40
What is the Pituitary Gland also called?
Hypophysis
41
Why is the Pituitary Gland not a true endocrine gland?
It does not manufacture and produce hormones of its own
42
What is the function of the Pituitary Gland?
Stores and releases hormones
43
What two lobes make up the Pituitary Gland?
Posterior and Anterior
44
Where is the Anterior Lobe located?
The FRONT of the Pituitary Gland
45
Where is the Posterior Lobe located?
The REAR of the Pituitary Gland
46
How is the Anterior Lobe connected to the Hypothalamus?
By a complex network of blood vessels lying in the infundibulum
47
How is the Posterior Lobe connected to the Hypothalamus?
By nerve fibres that come from nerve cell bodies in the hypothalamus and pass through the infundibulum
48
Where is the Pituitary Gland located?
Under the Hypothalamus
It is joined to the hypothalamus by a stalk called the infundibulum.
49
How large is the Pituitary Gland?
Not much bigger than a large pea, about 13mm in diameter.
50
What is another name for the Anterior Lobe?
Adenohypophysis
51
What is the function of the Anterior Lobe?
Releases a number of hormones that regulate a range of bodily activities.
Secretions are controlled by releasing and inhibiting factors secreted by the hypothalamus
52
What hormones are released from the Anterior Lobe?
Follicle Stimulating Hormone (FSH)
Luteinising Hormone (LH)
Growth Hormone (GH) or Somatotropin
Thyroid-stimulating Hormone (TSH) or Thyrotropin
Adrenocorticotropin Hormone (ACTH) or Adrenocorticotropin
Prolactin (PRL) or Lactogenic Hormone
53
What is Follicle Stimulating Hormone (FSH) target organ and function?
TARGET ORGAN:
Females: ovaries
Males: testes
FUNCTION:
Females: Stimulates development of the follicles that contain eggs in the ovary
Males: Stimulates the production and maturation of sperm in the testes
54
What is Luteinising Hormone (LH) target organ and function?
TARGET ORGAN:
Females: ovaries
Males: testes
FUNCTION:
Females: Causes ovulation to occur and forms the corpus luteum after ovulation
Males: Stimulates the interstitial cells in the testes to secrete male sex hormones
55
What is Growth Hormone (GH) or Somatotropin target organ and function?
TARGET ORGAN:
All body cells
FUNCTION:
Stimulates body growth, particularly growth of the skeleton. It increases the rate at which amino acids are taken up by cells and built into proteins. GH is secreted throughout life as it helps to maintain the size of organs once maturity is released
56
What is Thyroid-stimulating Hormone (TSH) or Thyrotropin target organ and function?
TARGET ORGAN:
Thyroid
FUNCTION:
Stimulates production and release of hormones from the thyroid gland
57
What is Adrenocorticotropin Hormone (ACTH) or Adrenocorticotropin target organ and function?
TARGET ORGAN:
Adrenal Cortex
FUNCTION:
Controls production and release of some of the hormones from the cortex of the adrenal glands
58
What is Prolactin (PRL) or Lactogenic Hormone target organ and function?
TARGET ORGAN:
Mammary Glands
FUNCTION:
Works with other hormones to initiate and maintain milk production in females
59
What is another name for the Posterior Lobe?
Neurohypophysis
60
What is the function of the Posterior Lobe?
Releases the hormones oxytocin and antidiuretic hormone (does not manufacture them, only stores them. Both are produced in special nerve cells in the hypothalamus).
The release of the hormones into the bloodstream is triggered by nerve impulses initiated by the hypothalamus and conducted along the cell extensions that pass through the infundibulum to the posterior lobe.
61
What hormones are released from the Posterior Lobe?
Oxytocin (OT)
Antidiuretic Hormone (ADH) or Vasopressin
62
What is Oxytocin (OT) target organ and function?
TARGET ORGAN:
Uterus or Mammary Glands
FUNCTION:
Stimulates the contraction of the muscles in the uterus. It is released in large qualities during labour.
It also stimulates the contraction of the cells in the mammary glands, resulting in the release of milk during breastfeeding
63
What is Oxytocin (OT) target organ and function?
TARGET ORGAN:
Uterus or Mammary Glands
FUNCTION:
Stimulates the contraction of the muscles in the uterus. It is released in large qualities during labour.
It also stimulates the contraction of the cells in the mammary glands, resulting in the release of milk during breastfeeding
64
What is Antidiuretic Hormone (ADH) or Vasopressin target organ and function?
TARGET ORGAN:
Kidneys
FUNCTION:
Causes the kidneys to remove water from urine that is forming. The water is returned to the bloodstream. In this way, ADH helps to retain fluid within the body. At high concentrations it can also cause constrictions of small arteries, the arterioles
65
Compare and contrast the Anterior and Posterior Lobes of the Pituitary Gland.
Compare: They are both part of the pituitary gland and are connected to the hypothalamus
Contrast: The posterior lobe only releases hormones it does not produce them whereas the anterior lobe produces and releases hormones
66
Where is the Pineal Gland located?
Found deep inside the brain
67
What is the size of the Pineal gland?
In children it is about the size of a pea. After puberty it gradually decreases in size.
68
What is the function of the Pineal Gland?
It secretes the hormone melatonin, which is involved in the regulation of sleep patterns. The production of melatonin by the pineal gland is stimulated by darkness and inhibited by light.
69
Where is the thyroid gland located?
In the neck, just below the larynx. It consists of two lobes that lie on either side of the trachea and are joined by a narrow piece of tissue that lies across the front of the trachea.
70
What is the structure of the thyroid gland?
It consists of two lobes that lie on either side of the trachea and are joined by a narrow piece of tissue that lies across the front of the trachea.
71
What is the function of the thyroid gland?
The follicular cells in the thyroid gland secrete two hormones in response to thyroid stimulating hormone: Thyroxine (T4) and Triiodothyronine (T3)
It also plays a role in regulating the levels of calcium and phosphate in the blood through the release of calcitonin by C-cells.
72
Explain the difference between T3 and T4
The structure of both T3 and T4 is based on two molecules of the amino acid, tyrosine.
T3 has three iodine atoms attached whilst T4 has four iodine atoms attached
T4 is much less active than T3 but lasts longer
Approximately 80% of the hormones produced by the thyroid are T3 and 20% are T4.
Once released enzymes convert T4 into T3.
Thyroxine controls body metabolism by regulating reactions in which complex molecules are broken down to release energy and other reactions in which complex molecules are synthesised from simple ones. The overall effect of T3 is to bring about the release of energy and because some of the energy released is in the form of heat to maintain body temperature.
73
How does calcitonin regulate the levels of calcium in the blood?
When the concentration of calcium in the blood increases, the thyroid gland releases calcitonin, which reduces the reabsorption of calcium by the kidneys and the breakdown of bone.
If the concentration of phosphate in the blood becomes too high, calcitonin acts to move phosphate into bone and reduces its reabsorption by the kidneys
These actions allow calcium and phosphate concentrations to decrease.
74
Where is the Parathyroid located?
In the rear surface of the lobes of the thyroid gland.
75
How many parathyroids does the human body have?
There are usually four but some people have more.
76
What is the size of a parathyroid gland?
Each is about the size of a small pea.
77
What is the function of a parathyroid gland?
Secretes parathyroid hormone (PTH or parathormone), which increases calcium levels in the blood and phosphate excretion in the urine.
78
Where is the Thymus located?
In the chest just above the heart and just behind the sternum
79
Does the size of the Thymus change after puberty?
Like the pineal gland, the thymus is largest in infants and children and begins to shrink at puberty
80
What is the function of the Thymus?
Secretes a group of hormones called thymosin's, these hormones influence the maturation of disease fighting cells called T-lymphocytes.
81
What are the two Adrenal Glands?
Adrenal medulla (inner) and adrenal cortex (outer)
82
Why are the two Adrenall Glands seperate Endocrine Glands?
Due to their difference in structure and function.
83
Where are the Adrenal Glands located?
One gland is immediately above each kidney
84
What is the function of the Adrenal Medulla?
Produce the hormones adrenaline and noradrenaline.
85
What is the effect of Adrenaline?
Adrenaline, also called epinephrine, has an effect similar to that of the sympathetic division of the autonomic nervous system, Adrenaline helps the body prepare for reaction to a threatening situation (fight-or-flight response).
86
What is the effect of Noradrenaline?
Noradrenaline, also called norepinephrine, has effects similar to those of adrenaline, in particular, it increases the rate and force of the heartbeat
87
What is the function of the Adrenal Cortex?
To produce more than twenty corticosteroids, the two main ones are Aldosterone and Cortisol.
88
What is the effect of Aldosterone?
Acts on the kidney to reduce the amount of sodium and increase the amount of potassium in the urine
89
What is the effect of Cortisol?
Cortisol, with related hormones promotes normal metabolism, helping the body to withstand stress and repair damaged tissues
90
Is a Pancreas an endocrine or an exocrine gland?
Both
91
Where is the Pancreas located?
Lies just below the stomach and alongside the duodenum
92
What is the size of the Pancreas?
Soft organ approximately 15cm long
93
What is the function of the Pancreas as an Exocrine gland?
To secrete digestive enzymes into the small intestines through the pancreatic duct
94
What is the function of the Pancreas as an Endocrine gland?
It is made up of clusters of specialised cells called islets of Langerhans (also called pancreatic islets). These cells secrete two important hormones; Insulin and Glucagon
95
What is Insulin secreted by and what is its effect?
SECRETED BY: The beta cells of the islets of Langerhans
FUNCTION: Reduces the amount of glucose in the blood (reduces blood sugar levels) by promoting the uptake of glucose from the blood by the cells of the body
In the liver, insulin causes the conversion of glucose to glycogen (in skeletal muscles) and fat (in fat storage tissue)
The level of secretion of insulin by the pancreas is determines by the amount of glucose in the blood and is controlled through a negative feedback system
96
What is Glucagon secreted by and what is its effect?
SECRETED BY: The alpha cells of the islets of Langerhans
FUNCTION: Act in the opposite way to insulin
Increases the blood glucose level, mainly by promoting the breakdown of glycogen to glucose in the liver.
Glucagon also stimulates the breakdown of fat in the liver and in fat storage tissues.
97
What are considered to be Gonads?
The testes and the ovaries
98
99
Where are the Gonads located?
Male and female reproductive systems
100
What is the function of the Gonads?
Have a role in the production of sperm and eggs
They are endocrine glands due to their production of the hormones; Androgens, Oestorgens and Progesterone.
101
What are Androgens responsible for and where are they produced?
EXAMPLE: testosterone
RESPONSIBLE FOR: The development and maintenance of the male sex characteristics
PRODUCED BY: The testes. Females also produce them in their ovaries but at much lower level
102
What are Oestrogen and Progesterone responsible for and where are they produced?
RESPONSIBLE FOR: Stimulating the development and maintenance of the female sex characteristics. Together with the gonadotropic hormones of the pituitary, they also regulate the menstrual cycle and are involved in changes that occur during pregnancy
PRODUCED BY: The ovaries
103
What are some examples of other Endocrine Tissues?
The STOMACH and SMALL INTESTINES both secrete hormones that coordinate the exocrine glands of the digestive system
The KIDNEYS secrete hormones, including erythropoietin (EPO) - a hormone that stimulate the production of red blood cells by the bone marrow
The HEART secretes a hormone that helps reduce blood pressure
The PLACENTA secretes a number of hormones during pregnancy that help maintain the pregnancy, stimulate the development of the foetus and stimulate the mothers mammary glands
104
What is Thyroxine and Triiodothyronine produced by and what are the target cells/glands?
PRODUCED BY: Thyroid
TARGET: Most Body Cells
105
What is Calcitonin produced by and what are the target cells/glands?
PRODUCED BY: Thyroid
TARGET: Bones and Kidneys
106
What is the Parathyroid Hormone produced by and what are the target cells/glands?
PRODUCED BY: Parathyroid
TARGET: Bones and Kidneys
107
What is Thymosins produced by and what are the target cells/glands?
PRODUCED BY: Thymus
TARGET: T-Lymphocytes
108
What is Aldosterone (Corticosteroid) produced by and what are the target cells/glands?
PRODUCED BY: Adrenal Cortex
TARGET: Kidneys
109
What is Cortisol (Corticosteroid) produced by and what are the target cells/glands?
PRODUCED BY: Adrenal Cortex
TARGET: Most Body Cells
110
What is Adrenaline and Noradrenaline produced by and what are the target cells/glands?
PRODUCED BY: Adrenal Medulla
TARGET: Most body tissues
111
What is Insulin produced by and what are the target cells/glands?
PRODUCED BY: Pancreas
TARGET: Most body cells
112
What is Glucagon produced by and what are the target cells/glands?
PRODUCED BY: Pancreas
TARGET: Liver and fat storage tissues
113
What is Androgens (e.g. testosterone) produced by and what are the target cells/glands?
PRODUCED BY: Testes
TARGET: Many Tissues
114
What is Oestrogens produced by and what are the target cells/glands?
PRODUCED BY: Ovaries
TARGET: Many tissues
115
What is Progesterone produced by and what are the target cells/glands?
PRODUCED BY: Ovaries
TARGET: Uterus and Mammary Glands
116
What is the main effects of Thyroxine and Triiodothyronine?
Increases metabolic rate and therefore oxygen consumption and heat production
117
What is the main effects of Calcitonin?
Decreases calcium and phosphate levels in the blood
118
What is the main effects of Parathyroid Hormone?
Increases levels of calcium in the blood
119
What is the main effects of Thymosins?
Stimulates development and maturation of T-lymphocytes
120
What is the main effects of Aldosterone (Corticosteroid)?
Increases reabsorption of sodium ions and excretion of potassium ions
121
What is the main effects of Cortisol (Corticosteroid)?
Promotes normal metabolism; helps the body deal with stress promotes repair of damaged tissues
122
What is the main effects of Adrenaline and Noradrenaline?
Prepares the body for fight-or-flight responses, reinforces the effects of the sympathetic nervous system
123
What is the main effects of Insulin?
Stimulate the uptake of glucose; lowers the blood glucose level
124
What is the main effects of Glucagon?
Stimulates the breakdown of glycogen and fat; increases blood glucose levels
125
What is the main effects of Androgens (e.g. testosterone)?
Stimulates sperm production, growth of skeleton and muscle and development of male sexual characteristics
126
What is the main effects of Oestrogens?
Stimulates development of female sexual characteristics and regulates the menstrual cycle
127
What is the main effects of Progesterone?
Regulates the menstrual cycle and pregnancy; prepares mammary glands for milk secretion
128
Why do people with hyperthyroidism (overactive thyroid) experience weight loss?
Hyperthyroidism is the over-secretion of thyroxine from the thyroid gland. Higher levels ofthyroxine will result in a higher body metabolism, which uses glucose, glycogen stores and adipose tissue.
As such, a person will not store excess glucose as fats, and will use up any stores they may have.
129
Explain how Insulin and Glucagon are able to keep blood glucose at the correct level
Insulin is secreted when blood glucose levels are elevated, and acts to bring glucose levels down towithin tolerance limits. Glucagon acts to raise blood glucose levels, so after a period of fasting glucagon will be released to bring blood glucose levels up into the tolerance limits.
130
Explain why oestrogen and progesterone are called the female hormones when they exist in both males
and females.
Progesterone in males acts to counteract the effect of oestrogen. Progesterone is seen as a
precursor to the production of testosterone.
Oestrogen in males has a beneficial effect ton bone metabolism, preventing the appearance of osteoporosis. At a cardiovascular level, oestrogen in males has been found to increase the good cholesterol. Oestrogen is produced by the adrenal glands and the testes in males.
131
Explain how the body is able to maintain a consistent level of calcium in the blood.
Calcium levels are maintained in the blood stream under the influence of parathormone (released from the parathyroid glands) to act on the bones, intestine and kidneys to increase calcium levels.
Calcitonin (released by the thyroid gland) acts to lower calcium levels in the blood stream by reducing the level of reabsorption at the kidneys.
