Endocrine System (ch.28): pt.1 Flashcards
1
Q
How do nervous system responses compare to endocrine system responses?
A
Nervous system responses are generally more rapid but briefer, while endocrine system responses usually take longer to be seen and last longer.
2
Q
What is the primary function of the nervous and endocrine systems?
A
The nervous and endocrine systems act together to coordinate all systems of the body.
3
Q
What do the nervous and endocrine systems release?
A
The nervous system releases neurotransmitters; the endocrine system releases hormones.
4
Q
What are hormones?
A
Hormones are molecules released in one part of the body that regulate the activity of cells in another part of the body.
5
Q
How do hormones circulate in the body?
A
Most hormones circulate through the blood and bind to receptors on ‘target cells’.
6
Q
How do neurotransmitters interact with target cells?
A
Neurotransmitters bind to receptors on ‘target’ cells.
7
Q
What are the two kinds of glands in the body?
A
Exocrine glands and endocrine glands.
8
Q
What does ‘exo-‘ mean in exocrine glands?
A
‘Exo-‘ means ‘external’ or ‘outside’.
9
Q
How do exocrine glands secrete their products?
A
They secrete their products into ducts that carry secretions into body cavities, the lumen of an organ, or to the outer surface of the body.
10
Q
Are exocrine glands hormones?
A
No, none of these are hormones.
11
Q
What are some examples of exocrine glands?
A
Examples include sudoriferous (sweat) glands, sebaceous (oil) glands, mucous glands, and digestive glands.
12
Q
What do endocrine glands secrete?
A
Endocrine glands secrete hormones.
13
Q
Do endocrine glands have ducts?
A
No, endocrine glands do not have ducts; they secrete hormones directly into the interstitial fluid.
14
Q
In what amounts are hormones generally required for a response?
A
Hormones are generally required in low amounts for a response.
15
Q
How do hormones reach target cells?
A
Hormones diffuse into the bloodstream through capillaries and are carried to target cells throughout the body.
16
Q
What are some examples of endocrine glands?
A
Endocrine glands include the pituitary, thyroid, parathyroid, adrenal, and pineal glands.
17
Q
What hormones does the hypothalamus produce?
A
The hypothalamus produces hormones like oxytocin and releasing hormones that control the pituitary gland.
18
Q
What is the role of hormones produced by the thymus?
A
The thymus produces hormones that help with immune system development.
19
Q
What hormones does the pancreas produce?
A
The pancreas makes insulin and glucagon to regulate blood sugar.
20
Q
What sex hormones do the ovaries and testes produce?
A
The ovaries and testes produce sex hormones like estrogen, progesterone, and testosterone.
21
Q
What hormone do the kidneys release?
A
The kidneys release erythropoietin (EPO) to stimulate red blood cell production.
22
Q
What hormones are secreted by the stomach and small intestine?
A
The stomach and small intestine secrete hormones like gastrin and cholecystokinin to aid digestion.
23
Q
What hormone does the liver produce?
A
The liver produces hormones like IGF-1, which is important for growth.
24
Q
How does the skin contribute to hormone production?
A
The skin helps produce vitamin D (a hormone) in response to sunlight.
25
What hormone does the heart produce?
The heart produces atrial natriuretic peptide (ANP) to regulate blood pressure.
26
What does adipose tissue secrete?
Adipose tissue (fat) secretes leptin, which signals hunger and energy balance.
27
What hormones does the placenta produce?
The placenta produces hormones to support pregnancy, like hCG.
28
What are the main functions of the endocrine system?
The endocrine system interacts continuously through hormone secretions, controls and coordinates all metabolic activities, and maintains homeostasis in the body.
29
What makes endocrine glands different from other glands?
Endocrine glands are ductless glands that release hormones directly into the bloodstream, allowing their hormones to travel through blood to reach target organs.
30
What are the major endocrine glands and their hormones?
Major glands and hormones include:
- Hypothalamus: ADH (anti-diuretic hormone)
- Pituitary: TSH, FSH, LH, Prolactin, ACTH, GH
- Thyroid: Thyroxin
- Adrenal glands: Aldosterone, Cortisol, Adrenalin
- Pancreas: Insulin, Glucagon
- Ovaries: Estrogen, Progesterone
- Testes: Testosterone.
31
What are target organs in the endocrine system?
Target organs are specific cells that respond to a given hormone. Although hormones travel throughout the body in blood, they only affect certain cells.
32
What is a hormone?
A hormone is an organic chemical substance (usually protein or steroid) secreted by endocrine glands, carried in the bloodstream to target organs, regulates metabolic reactions, can be regulated by feedback mechanisms, and is broken down by enzymes in the body.
33
How do hormones affect target cells?
Hormones travel through the blood but affect only specific target cells that have matching protein receptors.
34
What is an example of a hormone and its specific receptors?
TSH only binds to receptors on thyroid cells, not ovary cells, because ovaries lack TSH receptors.
35
What is down-regulation in hormone receptors?
Down-regulation occurs when a hormone is in excess, leading to a decrease in the number of its receptors and reduced sensitivity.
## Footnote
Example: High LH levels in testes reduce LH receptors.
36
What is up-regulation in hormone receptors?
Up-regulation occurs when a hormone is low, causing an increase in receptors and making the cell more sensitive to the hormone.
37
How many receptors can a cell have for a specific hormone?
A cell can have up to 2000–100,000 receptors for a specific hormone.
38
What happens to hormone receptors in cells?
Hormone receptors in cells are constantly being created (synthesized) and destroyed (broken down).
39
What is the purpose of the balancing act of hormone receptors?
This balancing act ensures that cells respond appropriately to changing hormone levels.
40
What are circulating hormones?
Circulating hormones travel through the blood to reach and affect distant target cells.
41
What are local hormones?
Local hormones work near their source without entering the blood.
42
What are paracrines?
Paracrines are local hormones that affect nearby cells.
43
What are autocrines?
Autocrines are local hormones that affect the same cell that made them.
44
What are lipid-soluble hormones?
Lipid-soluble hormones travel bound to transport proteins in blood.
45
What are examples of lipid-soluble hormones?
Examples include steroid hormones, thyroid hormones (T3 and T4), nitric oxide (NO), and eicosanoids.
46
What are steroid hormones made from?
Steroid hormones are made from cholesterol with unique chemical groups, giving them diverse functions.
47
What are thyroid hormones based on?
Thyroid hormones (T3 and T4) are iodine and tyrosine-based; they are very lipid-soluble.
48
What is nitric oxide (NO)?
Nitric oxide (NO) is a hormone and neurotransmitter, synthesized by nitric oxide synthase.
49
What are eicosanoids derived from?
Eicosanoids are derived from fatty acids and include local hormones like prostaglandins and leukotrienes.
50
What are water-soluble hormones?
Water-soluble hormones circulate freely in blood plasma.
51
What are examples of water-soluble hormones?
Examples include amine hormones, peptide hormones, and protein hormones.
52
What are amine hormones made from?
Amine hormones are made by modifying amino acids (e.g., epinephrine, dopamine, histamine, serotonin, and melatonin).
53
What are peptide hormones?
Peptide hormones are short chains of amino acids (e.g., antidiuretic hormone, oxytocin).
54
What are protein hormones?
Protein hormones are long chains of amino acids (e.g., growth hormone, insulin, thyroid-stimulating hormone). Some are glycoproteins (contain carbohydrates).
55
What is the key difference between lipid-soluble and water-soluble hormones?
Lipid-soluble hormones need transport proteins and act within cells, while water-soluble hormones travel freely and act on cell surfaces.
56
What are lipid-soluble hormones?
Hormones that can easily pass through cell membranes due to their lipid solubility.
57
What are steroid hormones derived from?
Cholesterol.
58
What makes each steroid hormone unique?
The presence of different chemical groups attached at various sites on the four rings at the core of its structure.
59
What are thyroid hormones derived from?
The attachment of iodine to tyrosine.
60
What is Nitric Oxide (NO)?
A hormone and neurotransmitter.
61
What are eicosanoid hormones derived from?
A 20-carbon fatty acid, specifically arachidonic acid.
62
Can you give examples of eicosanoid hormones?
Prostaglandins and leukotrienes.
63
What is the chemical class of aldosterone, cortisol, androgens, calcitriol, testosterone, estrogens, and progesterone?
Steroid hormones.
64
Where are steroid hormones such as aldosterone, cortisol, androgens secreted?
Suprarenal cortex.
65
What is the site of secretion for calcitriol (active form of vitamin D)?
Kidneys.
66
Where is testosterone secreted?
Testes.
67
Where are estrogens and progesterone secreted?
Ovaries.
68
What is the chemical class of T₃ (triiodothyronine) and T₄ (thyroxine)?
Thyroid hormones.
69
Which gland secretes T₃ and T₄ hormones?
Thyroid gland (T thyrocytes).
70
What is the chemical class of nitric oxide (NO), prostaglandins, and leukotrienes?
Gas and eicosanoids.
71
Where is nitric oxide (NO) secreted?
Endothelial cells lining blood vessels.
72
Which cells secrete prostaglandins and leukotrienes?
All cells except red blood cells.
73
What are Amine Hormones?
Made by modifying amino acids (removing CO₂).
## Footnote
Examples include catecholamines (epinephrine, norepinephrine, dopamine from tyrosine), histamine (from histidine), serotonin and melatonin (from tryptophan).
74
What are Peptide and Protein Hormones?
Structure: Chains of amino acids (small or large).
## Footnote
Peptide hormones (small chains) include antidiuretic hormone (ADH) and oxytocin. Protein hormones (large chains) include growth hormone (hGH) and insulin. Glycoprotein hormones (with carbohydrates) include thyroid-stimulating hormone (TSH).
75
What is insulin?
Insulin is a hormone that regulates blood sugar levels.
76
What are the different responses triggered by insulin?
Insulin can trigger the synthesis of new molecules, change cell membrane permeability, stimulate substance transport, alter metabolic rates, and cause muscle contraction.
77
How does insulin change cell membrane permeability?
Insulin can alter how easily substances (like glucose) move into a cell by increasing the number of transport proteins on the cell membrane.
78
What role does insulin play in stimulating substance transport?
Insulin helps move substances (like glucose or amino acids) into or out of the cell efficiently.
79
How does insulin affect metabolic rates?
Insulin may speed up or slow down chemical processes in the cell, like turning glucose into energy.
80
What effect does insulin have on muscle contraction?
In smooth or cardiac muscle cells, hormones like insulin might help coordinate contractions.
81
Why do hormones trigger varied actions?
Hormones can produce different effects based on the type of receptor they bind to, the kind of cell, and the internal pathways the cell uses to respond.
82
What is the takeaway about insulin's role in the body?
The same hormone, like insulin, can have many roles in the body because it triggers different responses in different types of cells.
83
How do lipid-soluble hormones bind to target cells?
Lipid-soluble hormones can easily pass through the cell membrane and bind to receptors located in the cytoplasm or nucleus.
84
What is the process of entering the cell for lipid-soluble hormones?
The hormone travels from the blood vessel, moves through the interstitial fluid, and enters the target cell.
85
What happens when a lipid-soluble hormone binds to its receptor?
The hormone and receptor form a hormone-receptor complex, which interacts with the cell’s DNA to activate specific genes.
86
What is the role of activated genes in lipid-soluble hormone action?
The activated genes direct the production of specific proteins using mRNA and ribosomes.
87
What functions do the proteins synthesized in response to lipid-soluble hormones perform?
The proteins perform functions related to the hormone, such as regulating metabolism or cell growth.
88
What is a key point about lipid-soluble hormones?
Lipid-soluble hormones work directly inside the cell, altering its DNA activity to produce the changes required by the hormone!
89
What happens when a water-soluble hormone binds to a receptor on the target cell's membrane?
It activates a G protein, which in turn activates the enzyme adenylyl cyclase.
90
What does adenylyl cyclase convert ATP into?
cAMP, which acts as a second messenger inside the cell.
91
What is the role of cAMP in the cell?
cAMP carries the signal further inside the cell and activates protein kinases.
92
What do activated protein kinases do?
They add phosphate groups to specific proteins (phosphorylation), changing the proteins' activity.
93
What is the result of phosphorylated proteins?
They trigger multiple physiological responses, like increased metabolism and muscle contraction.
94
How is the signal stopped in the cell?
The enzyme phosphodiesterase breaks down cAMP.
95
Why can't water-soluble hormones enter the cell directly?
They use cAMP as a 'middleman' (second messenger) to produce the desired effects inside the cell.
96
What factors influence how a target cell responds to a hormone?
The hormone’s concentration in the blood, the number of hormone receptors on the target cell, and influences exerted by other hormones.
97
What is the synergistic effect in hormone action?
Some hormones work more effectively when a second hormone is present to assist them, resulting in a combined effect greater than each hormone separately.
## Footnote
Example: Glucagon and epinephrine both increase blood glucose individually, but together their response is greater.
98
What is the antagonistic effect in hormone action?
Some hormones oppose the action of others, causing opposite cellular responses or reducing the number of receptors.
## Footnote
Example: Insulin and glucagon have opposite effects on blood glucose levels.
99
How are hormones secreted?
Hormones are secreted in short bursts when needed.
100
What happens when stimulation increases?
Increased stimulation increases concentration in the blood.
101
What occurs in the absence of stimulation?
Absence of stimulation = level of hormone in blood decreases.
102
What regulates hormone secretion?
Secretion is regulated by signals from the nervous system, chemical changes in the blood, and other hormones.
103
How do signals from the nervous system regulate hormone secretion?
E.g. nerve impulses to adrenal medulla regulate release of epinephrine.
104
How do chemical changes in the blood affect hormone secretion?
E.g. blood calcium levels regulate secretion of parathyroid hormone.
105
How do other hormones influence secretion?
E.g. ACTH from anterior pituitary stimulates secretion of cortisol from the adrenal cortex.
106
What do the hypothalamus and pituitary gland control?
They work together to control other endocrine glands.
107
Where is the hypothalamus located?
It is located below the thalamus of the brain.
108
What is the major function of the hypothalamus?
It is the major link between the nervous and endocrine systems.
109
How many releasing and inhibiting hormones does the hypothalamus produce?
It produces 5 releasing and 2 inhibiting hormones.
110
What do the hormones produced by the hypothalamus affect?
They affect the anterior pituitary.
111
How is the pituitary gland connected to the hypothalamus?
It is connected by the infundibulum.
112
What are the two parts of the pituitary gland?
It is composed of the anterior and posterior lobes.
113
How many types of cells are in the anterior pituitary?
There are 5 types of cells.
114
How many different hormones does the anterior pituitary secrete?
It secretes seven different hormones.
115
What is the function of Growth hormone-releasing hormone?
It stimulates the release of growth hormone from the anterior pituitary.
116
What does Thyrotropin releasing hormone do?
It promotes the secretion of thyroid-stimulating hormone from the anterior pituitary.
117
What is the role of Corticotropin-releasing hormone?
It triggers the release of adrenocorticotropic hormone from the anterior pituitary.
118
What does Prolactin-releasing hormone stimulate?
It stimulates the secretion of prolactin from the anterior pituitary.
119
What is the function of Gonadotropin-releasing hormone?
It stimulates the release of luteinizing hormone and follicle-stimulating hormone from the anterior pituitary.
120
What is Growth hormone-inhibiting hormone?
Also known as somatostatin, it inhibits the release of growth hormone from the anterior pituitary.
121
What does Prolactin-inhibiting hormone do?
Also known as dopamine, it inhibits the secretion of prolactin from the anterior pituitary.
122
What makes up 75% of the weight of the pituitary gland?
The anterior lobe (adenohypophysis) makes up 75% of the weight of the pituitary gland and secretes 7 hormones.
123
What is the posterior lobe of the pituitary gland made of?
The posterior lobe (neurohypophysis) is made of neural tissue and releases two hormones made by the hypothalamus.
124
What does the hypothalamus secrete?
The hypothalamus secretes releasing and inhibiting hormones that control the release of hormones by the pituitary gland.
125
How do hormones reach the pituitary gland?
They reach the pituitary gland via the hypophyseal portal system.
126
What is an advantage of the system between the hypothalamus and the anterior pituitary?
There is direct communication between the hypothalamus and the anterior pituitary.
127
What do neurosecretory cells secrete?
Neurosecretory cells secrete hypothalamic hormones in response to stimulation.
128
How are hypothalamic hormones released?
Vesicles are released from the axon terminal.
129
What happens to the hormones after they are released?
They diffuse into the blood and move through the hypophyseal portal system.
130
What is the role of negative feedback loops in hormone regulation?
The body uses negative feedback loops to regulate hormone secretion and maintain balance.
131
What happens when hormone levels get too high?
The body reduces or stops further hormone production to prevent overproduction.
132
What is an example of a negative feedback loop in hormone regulation?
Regulation of Cortisol.
133
What does CRH stand for?
Corticotropin-Releasing Hormone.
134
Where is CRH released from?
The hypothalamus.
135
What does CRH stimulate?
The anterior pituitary to produce ACTH.
136
What does ACTH stand for?
Adrenocorticotropic Hormone.
137
Where does ACTH travel to?
The adrenal cortex.
138
What does ACTH stimulate the adrenal cortex to produce?
Cortisol.
139
What are the functions of cortisol?
Helps the body respond to stress, regulates metabolism, and maintains homeostasis.
140
What happens when cortisol levels rise too high?
They signal the hypothalamus and anterior pituitary to stop producing CRH and ACTH.
141
Why is the negative feedback loop important?
It ensures that hormones like cortisol are regulated properly.
142
What could happen without proper regulation of cortisol?
Excessive cortisol could harm the body by leading to issues like suppressed immune function or imbalance in blood sugar levels.
143
What controls the secretion of human growth hormone?
It is controlled by two hypothalamic hormones: growth hormone-releasing hormone (GHRH) and growth hormone-inhibiting hormone (GHIH).
144
How does human growth hormone exert its effects?
It exerts its growth-promoting effect indirectly through small protein hormones called insulin-like growth factors (IGFs).
145
What are the effects of insulin-like growth factors (IGFs)?
IGFs cause increases in growth of bone and soft tissues, enhanced lipolysis, and decreased glucose uptake.
146
How do IGFs promote growth in bone and soft tissues?
They promote growth by increasing amino acid uptake and protein synthesis.
147
What is the main function of the posterior pituitary gland?
The posterior pituitary acts as a storage and release center for hormones made in the hypothalamus. It does not produce any hormones itself.
148
Name the two hormones stored and released by the posterior pituitary.
1. Oxytocin (OT) 2. Antidiuretic Hormone (ADH)
149
What is the function of Oxytocin?
Oxytocin helps with uterine contractions during childbirth and milk release during breastfeeding.
150
What is the function of Antidiuretic Hormone (ADH)?
ADH helps the body conserve water by reducing urine production and regulating water balance.
151
What is the hypothalamohypophyseal tract?
It is the collection of axons that extend from neurosecretory cells in the hypothalamus down to the posterior pituitary.
152
Where are the hormones released by the posterior pituitary actually produced?
In the neurosecretory cells of the hypothalamus.
153
How are hormones released from the posterior pituitary?
Through exocytosis, where nerve impulses trigger the release of hormones stored in vesicles at the axon terminals.
154
What type of cells produce the hormones stored in the posterior pituitary?
Neurosecretory cells (specialized nerve cells) in the hypothalamus.
155
What triggers the release of hormones from the posterior pituitary?
Nerve impulses from the hypothalamus trigger the release of hormones stored in vesicles.
156
What is exocytosis in relation to the posterior pituitary?
It is the process where vesicles release their hormone contents into the bloodstream at the axon terminals.
157
Where are posterior pituitary hormones initially produced?
In the neurosecretory bodies (specialized nerve cells) of the hypothalamus.
158
Where are these hormones stored?
In vesicles at the axon terminals in the posterior pituitary.
159
What triggers hormone release from the axon terminals?
Nerve impulses from the hypothalamus trigger exocytosis (release) of the hormones.
160
What is exocytosis?
The process where vesicles release their stored hormones into surrounding blood vessels.
161
What is the path hormones take after being released?
Hormones enter capillaries in the infundibular process → hypophyseal vein → general circulation → target tissues.
162
What are vesicles?
Tiny storage sacs in axon terminals that hold hormones until they're needed for release.
163
What happens after hormones reach their target tissues?
They produce their specific effects (e.g., oxytocin causes uterine contractions, ADH regulates water balance).
164
What is the infundibular process?
A region in the posterior pituitary containing a network of capillaries where hormones enter the bloodstream.
165
What's the purpose of storing hormones in the posterior pituitary?
To ensure hormones are readily available for quick release when needed by the body.
166
How do posterior pituitary hormones travel from where they're made (hypothalamus) to where they're stored (post. pituitary)?
They are transported along axons from the hypothalamus to the posterior pituitary.
167
What triggers the release of oxytocin during childbirth?
Oxytocin is released in response to stretch placed on the cervix during childbirth.
168
What effects does oxytocin have?
Oxytocin affects the uterus and breasts.
169
What regulates the secretion of antidiuretic hormone (ADH)?
ADH secretion varies with blood osmotic pressure.
170
How does ADH affect urine output?
ADH decreases urine output as part of a negative feedback loop.
171
What monitors blood osmotic pressure in relation to ADH?
Osmoreceptors in the hypothalamus monitor blood osmotic pressure.
172
What happens to ADH secretion when blood volume increases?
An increase in blood volume causes a decrease in ADH secretion.
173
What happens to ADH secretion when blood volume decreases?
A decrease in blood volume causes an increase in ADH secretion.
