Endocrine Flashcards
1
Q
What is the endocrine function
A
Mood, Reproduction, Digestion/excretion, intermediary metabolism, growth, puberty
2
Q
What are the symptoms of endocrine dysfunction
A
Growth/retardation, weight gain/ loss, skin pigmentation/dryness/acne/swelling, sexual characteristics
3
Q
How is the nervous system homeostatically regulated?
A
Precise, rapid, finely adjusted, short-term regulation
4
Q
How is the endocrine system endocrine system homeostatically regulated?
A
Slower, more sustain control over long-term processes
5
Q
What are exocrine glands?
A
Empty their secretions into body cavities or onto body surfaces by tubular ducts
6
Q
What are endocrine glands?
A
Ductless glands that release their secretions internally into the bloodstream
7
Q
What are the characteristics of endocrine glands?
A
Paired or unpaired
Organs or scattered cells
One or more cell-types
Cells may secrete one or more hormones
Cells in clumps, cords, or scattered
Cells may have smooth ER or rough ER
Cell may/may not have secretory vesicles
Cells may/may not have lipid droplets
8
Q
What are the glands of the endocrine system?
A
Hypothalamus/pituitary
Pineal gland
Thyroid
Parathyroids
Thymus
Adrenals
Pancreas
Ovaries
Testes
9
Q
What do endocrine glands secrete and where?
A
Chemical messengers into the circulatory system
10
Q
What is paracrine signalling?
A
Target cells in close proximity to the site of release of paracrine substances
11
Q
What is autocrine signalling?
A
Acts on same cell that secreted the substance
12
Q
What is endocrine signalling?
A
Target cells in one or more distant places in the body and released into the bloodstream
13
Q
What is nervous signalling?
A
A neurotransmitter is released into a synapse close to the target site which is either another neuron or an effector cell
14
Q
What is neuroendocrine signalling?
A
Release messenger molecules into the blood
15
Q
What are the characteristics of hormones?
A
Chemical messengers that regulate homeostasis
Have high potency
Act at specific receptors
Act with a latency of response (actions are not immediate)
Have limited storage
Are secreted irregularly
Mostly carried in plasma by binding proteins
Are not an energy source
Are not incorporated into other molecules
16
Q
What are the two main groups of hormones?
A
Steroid
Protein
17
Q
What are steroid hormones?
A
Derived from cholesterol
18
Q
How are steroid hormones made?
A
Cholesterol enters the cell bound to LDL
It moves to the mitochondria where is undergoes the first step in steroid biogenesis
Released by diffusion
19
Q
How are protein hormones made?
A
Made from the translation of messenger RNA
mRNA to pre-hormone to pro-hormone to hormone
Packaged into secretory vesicles and released
20
Q
What are the functions of secretory vesicles?
A
Protect hormones from proteolytic degradation
provide a reservoir in sites of synthesis
Provides a transport mechanism to the site of release
Provides a release mechanism through which the vesicle membrane is incorporated into the plasma membrane
Provide a release mechanism (exocytosis)
Provides for quantal release of consistent hormone amounts
21
Q
What are the two types of hormones in the plasma?
A
Bound and free
22
Q
What are free hormones?
A
Biologically active
23
Q
What are bound hormones?
A
Inactive when bound to a binding protein
24
Q
What are the roles of protein binding of plasma hormones?
A
Increases solubility and concentration, providing a reservoir for target sites
Increases size, protecting hormones from clearance and degradation by the liver and kidney and degradation by plasma enzymes
Inactivates free hormones, providing a buffer against large and sudden changes in hormone concentrations
Dynamically regulated with rate of secretion, rate of degradation, and binding to receptors on target cells
25
How is hormone secretion regulated?
Dynamic regulation occurs in response to feedback from target sites
Negative feedback is common, and inhibits secretion when circulating levels are high and increases secretion when circulating levels are low
Positive feedback is rare, but allows discrete events to be rapidly attained
26
What is the negative feedback pathway?
Endocrine gland releases the hormone, hormone travels in the blood to act at its target site, causes release of a product into the bloodstream, product will cause suppression of the gland, decrease in secretion of the hormone from the gland
27
What is the positive feedback pathway?
Endocrine gland releases hormones, acts on the target cell or tissue, produces a product, product will then feedback on the endocrine gland from which the first hormone was released to stimulate it
28
What is hormone action?
Feedback results from hormone action at target sites
The first requisite for hormonal action is the binding of the hormone to a specific receptor
Only those cells that have receptors respond to particular hormones
29
What is signal amplification?
Signal transduction mechanisms allow for amplification of the response following binding of a hormone to its receptor
30
What are the two types of hormone receptors?
Nuclear
Cytoplasmic
31
What are nuclear receptors?
Steroid and thyroid hormones
Located in the nucleus of the cell
Genomically mediated through protein synthesis
32
What are cytoplasmic receptors?
Involved in intracellular transport for cytosol-insoluble steroids
Reservoir storage and organelle actions for thyroid hormones
33
What is downregulation?
(less receptors)
At high hormone concentrations to prevent over-activity
Decreased receptor synthesis/increased degradation
Internalized membrane receptors
Dislocation of receptor and signal transduction system
34
What is desensitization?
At high hormone concentrations to prevent over-activity
Conformational change in lock structure
35
What is up-regulation?
At low hormone concentration to increase activity
Increased receptor synthesis/decreased degradation
36
What is sensitization?
At low hormone concentrations to increase activity
Conformational change in lock structure
37
What is down-regulation by coated pits?
Allows protein hormones to enter the cell
38
What are the primary ways that endocrine dysfunction occurs?
Primary defect in synthesis = problems endocrine gland
Defect in regulation = problem in hormone action
Defect in hormone action = problem with target tissue
39
What is the hypophysis?
The pituitary gland
40
Where is the pituitary gland?
Ventral part of brain
Below the hypothalamus
41
What are the parts of the pituitary gland?
The anterior and posterior pituitary
42
What is the posterior pituitary?
Down-growth from the brain
Neural tissue
43
What is the anterior pituitary?
Derived from non-neural tissue (Rathke’s pouch)
44
What is the intermediate lobe?
Found between the anterior and posterior pituitary
Lost before birth
45
What are the neural connections between the posterior pituitary and the hypothalamus?
Hormones are produced in the hypothalamus nuclei (paraventricular nuclei and supraoptic nuclei)
The hormones are synthesized in the cell bodies of the nuclei and their long axons pass down the infundibulum and end in the posterior pituitary gland where they are stored
46
What hormones does the posterior pituitary secrete?
ADH/vasopressin
Oxytocin
47
What nuclei makes ADH?
Supraoptic nuclei
48
What nuclei make oxytocin?
Paraventricular nuclei
49
How are protein hormones synthesized in the nerves?
Hormone is produced in the cell body of the neuron, packaged into the golgi, transported along the axont to nerve terminals, stored in nerve terminals until appropriate stimulus comes, hormone moves into blood
50
What is the vasoconstriction action of ADH/Vasopressin?
Contraction of blood vessel smooth muscle
Increases blood pressure
Only occurs at high concentrations
51
What is the anti-diuretic action of ADH/Vasopressin?
Increases permeability of the renal collecting duct bu increasing the number of water channels
Vasoconstriction reduces glomerular filtration rate
Contraction reduces the size of the glomerulosa cells, reducing the surface area for filtration
52
What is the mechanism of action of ADH?
Travels to the kidneys
ADH binds to its receptor on the collecting cells
Binding of ADH to its receptor induces synthesis of a second messenger
Cyclic AMP causes the up-regulation of the aquaporin 2 protein via gene transcription
53
What are factors affecting the secretion of ADH/vasopressin?
Plasma volume
Plasma osmolarity
54
What cells are osmoreceptors?
The cells in the hypothalamus
Respond to changes in osmolarity
Ex: Supraoptic nucleus (SON) and paraventricular (PVN)
55
What receptors sense changes in blood pressure caused by alterations in blood volume?
Baroreceptors
56
What is the main stimuli for ADH release?
Decrease in blood volume or an increase in blood osmolarity
57
What is the effect of dehydration on ADH secretion?
Decreased extracellular fluid volume, decreased blood pressure, decreased stretch of blood vessel walls, baroreceptors decrease rate of firing, increased release of ADH, increased water reabsorption or retention from urine, water excretion decreases, water movement back into the plasma increases blood volume levels
58
What is the effect of water intake on ADH secretion?
Increase the extracellular fluid volume, increase in blood volume, increases blood pressure, stimulates stretch receptors or baroreceptors, baroreceptors cause a decrease in ADH release, permeability of the collecting ducts to water decreases, decreased water reabsorption, increased water excretion
59
What is the relationship between plasma ADH and plasma osmolarity?
Osmolarity of the blood increases with dehydration and decreases with over-hydration
Increase in plasma osmolarity = increase in plasma ADH
60
What is the relationship between plasma ADH and mean arteriole pressure?
Decline in MAP results in ADH release
ADH also causes vasoconstriction to increase blood pressure
61
What else is ADH secretion increased by?
Stress/emotion
Heat
Nicotine
Caffeine
62
What else is ADH decreased by?
Cold
Alcohol
63
Summary of ADH action
Synthesis: SON
Secretion: Posterior pituitary
Actions: Increased water retention and vasoconstriction
Stimuli: Increased osmolarity and decreased blood volume
64
What is a disease caused by low ADH?
Diabetes insipidus
65
What is a disease caused by excess ADH?
Syndrome of inappropriate ADH
Problem with ADH production, feedback failure
66
What is hypothalamic diabetes insipidus?
Problem with ADH production
67
What is nephrogenic diabetes insipidus?
Problem with ADH action
68
What is polyuria?
Production of large amounts of dilute urine
69
What is polydipsia?
Excessive thirst and fluid intake
70
Why is diabetes insipidus bad?
Cannot decrease urine flow even when water deprived
71
What is the treatment for diabetes insipidus?
ADH or other anti-diuretics
72
What is SIADH?
Increased ADH levels and decreased aldosterone levels result in hyponatremia or low blood sodium levels
73
What are the actions of oxytocin?
Uterine myometrium
-parturition
-clamping ruptured blood vessels
-restoration of uterine size
-sperm movement
-cervix movement
Mammary myometrium
-milk let-down
74
What is the effect of oxytocin on parturition?
Positive feedback loop
Weak uterine contractions push pressure of the fetus against the cervix which will strengthen uterine contractions and cause oxytocin secretion from the posterior pituitary
75
What is the effect of oxytocin on milk let-down?
Positive feedback loop
Suckling further increases the release of oxytocin
Also a conditioned response as visual and auditory stimuli from the infant can stimulate milk let-down
76
What are the other functions of oxytocin?
Released during sexual intercourse and stimulates orgasm
Social bonding
77
How is oxytocin secretion regulated?
Tactile stimuli from the nipples or the genital tract increase secretion
Stress decreases secretion
78
Summary of Oxytocin
Synthesis: PVN
Secretion: Posterior pituitary
Actions: increased lactation and uterine motility
Stimuli: genital/uterine/breast stimulation
79
What is the consequence of a deficiency of oxytocin?
Impaired delivery
Impaired lactation
No problems associated with high levels (excess) of oxytocin
80
What is the anterior pituitary?
Produces hormones essential for growth and reproduction
Controlled by the hypothalamus through the blood supply
81
How is the anterior pituitary supplied with blood?
Median eminence-capillary bed receives axons from nuclei in the hypothalamus and gives rise to the hypothalamo-hyposphyseal portal vessels which run into the anterior pituitary
Secretions from the hypothalamus are released into the capillary beds
82
What are the nuclei of the hypothalamus that control the anterior pituitary?
Parvocellular neurons
Magnocellular neurons
83
What are the parvocellular neurons?
Neurons with small cell bodies and short axons that end in the median eminence
Produce neural secretions that are released into the blood vessels
84
What are magnocellular neurons?
Neuroendocrine cells located in the hypothalamus
Synthesize the hormones ADH/vasopressin (PVN and SON)
85
What are anterior pituitary gland hormones?
Secretion regulated by hormones produced by the hypothalamus
Gonadotropins
Growth Hormone
Thyroid stimulating hormone
Prolactin
Adrenocorticotropin
86
What are hypothalamic-releasing hormones?
Neural secretions from the hypothalamus
Gonadotropin releasing hormone
Growth hormone releasing hormone
Thyrotropin releasing hormone
Prolactin-releasing factors
Corticotrophin-releasing hormone
Somatotropin release inhibitory factor
Prolactin inhibitory factors
87
How does the anterior pituitary control secretions with negative feedback?
Hormones released from target endocrine gland will provide negative feedback at the level of the anterior pituitary and at the level of the hypothalamus
Autoregulatory loop
Retrograde flow along the blood vessels
88
What are the effects of growth hormone on muscle?
Increased protein synthesis and decreased glucose uptake
Increased muscle mass
89
What is the effects of growth hormone on the liver?
Increased protein synthesis, gluconeogenesis, and somatomedin production
90
What are the effects of growth hormone on adipose?
Decreased glucose uptake and increase lipolysis
Decreased adiposity
91
What does somatomedin IGF-1 do?
Affects the chondrocytes of bone
Increases collagen synthesis, protein synthesis and cell proliferation
Increased linear growth
92
What does somatomedin IGF-II do?
Affects tissues and organs
Increased protein synthesis, RNA synthesis, DNA synthesis, and cell size and number
Increased tissue growth, increased organ size
93
What are 2 factors regulating growth hormone secretion?
Growth hormone inhibiting hormone and growth hormone releasing hormone
94
What is growth hormone release increased by?
Deep sleep, exercise, stress or reduced blood glucose levels, increased blood amino acids, and decreased blood fatty acids
95
What are the actions of GH on target sites that provide negative feedback?
Somatomedins from the liver inhibit GH release
GH inhibits its own release
GH release is inhibited by the products of lipolysis, glucose
96
What is the 24 hour plasma growth hormone profile of GH?
Diurnal pattern of GH release
Number and amplitude of GH is increased in the dark and increased during sleep
97
How does GH release change in response to blood nutrient levels?
Fasting increased GH release episodes
Frequent meals high in glucose or fatty acids suppress hormone release
Frequent meals high in amino acids increase growth hormone release
98
Summary of Growth Hormone
Synthesis: Somatotrophs
Secretion: Episodic, more during stress/sleep, less during aging, GHRH/SRIF balance
Action: Skeletal/soft tissue growth, hyperglycemia/hyperlipidemia, IGF-1 induction
99
What can a deficiency of growth hormone cause?
Dwarfism in juveniles
Somatopause in adults
100
What is an isolated GH deficiency?
Type 1 dwarfism
Defect in GH production
101
What is Laron-type dwarfism?
Defect in GH action
GH is not deficient, IGF-1 levels are deficient
102
What is the difference between a GH dwarf and a thyroid dwarf?
A GH hormone dwarf has normal body proportions but just shorter in height
Thyroid dwarfs have body proportions younger than their age
103
What is somatopause?
GH deficiency in adults
Increased fat and decreased lean mass
Metabolic disturbances
Impaired immune function (thyroid atrophy)
104
What is acromegaly?
Excess growth hormone production in an adult
105
What are the features of agromegaly?
Prognathism (bulging of jaw)
Hirsutism (unwanted male hair growth in females)
Large acral regions (hands and feet)
Enlarged male breast tissue (gynecomastia)
106
What are the actions of prolactin?
Gonadal modulation
-pro-gonadal when gonadal activity is low
-anti-gonadal when gonadal activity is high
Mammary gland development
Lactation
-milk production
107
What controls prolactin secretion?
Prolactin-releasing factors
Gonadal steroids
Mammary stimulation
108
What are some prolactin-releasing factors?
Thyrotropin-releasing hormone
Oxytocin
109
What are gonadal steroids causing prolactin secretion??
Estrogen/testosterone increase
Progesterone decrease
110
What is mammary stimulation?
111
What is hyperprolactinemia?
112
What are the symptoms of hyperprolactinemia?
113
What is the treatment for hyperprolactinemia?
114
What is hypoprolactinemia?
115
What are the symptoms of hypoprolactinemia?
116
What is pituitary diabetes?
117
What is hypopituitarism?
118
What is panhypopituitarism?
119
What is the hypothalamic-pituitary-thyroid axis?
120
What is thyroid-stimulating hormone?
121
What is a trophic hormone?
122
What is a glycoprotein hormone?
123
What is the thyroid gland?
124
What is thyroglobulin?
125
What are the two thyroid hormones?
126
What is T4?
127
What is the biologically active thyroid hormone?
128
How is thyroid hormone synthesized?
129
What makes T3?
130
What makes T4?
131
Summary of thyroid hormone synthesis
132
What are thyroid hormone-binding proteins?
133
What does thyroid hormone do?
134
What is the effect of thyroid hormone on metabolic rate and heat production? (main effects)
135
What is the effect of thyroid hormone on neural activity?
136
What is the effect of thyroid hormone on intermediary metabolism?
137
What is the effect of thyroid hormone on growth and development?
138
What are the three types of thyroid hormone receptors?
139
What are membrane-bound thyroid hormone receptors?
140
What are cytoplasmic thyroid hormone receptors?
141
What are nuclear thyroid hormone receptors?
142
What are the unique features of the thyroid hormone?
143
What happens when there is excess thyroid hormone?
144
What is primary thyroid dysfunction?
145
What is secondary thyroid dysfunction?
146
What is tertiary thyroid dysfunction?
147
What is Grave’s disease?
148
What are the characteristics of Grave’s disease?
149
What happens when there is a thyroid hormone deficiency?
150
What are some causes of hypothyroidism?
151
What is an endemic goitre?
152
What is Hashimoto’s thyrodiditis?
153
What is cretinism?
154
What is myxedema?
155
What are hypothyroid characteristics?
Dull blank expression, slow mentation ???, Decreased BMR, Bradycardia (slower normal heart rate)
156
What are the adrenal glands?
157
What are steroid hormones of the adrenal cortex?
158
Which of the adrenal cortex hormones provide feedback?
159
What is adrenocorticotropin?
160
How is ACTH released?
161
What does POMC do?
162
What are the zones of the adrenal cortex?
163
What is the glomerular zone?
??? No metabolism (salt/water retention)
164
What is the fascicular zone?
165
What is the reticular zone?
