Endocrine Flashcards
(189 cards)
1
Q
What are endocrine glands?
A
Ductless glands that secrete blood borne messengers (secreted directly into blood) to act on target cells located a long distance away
2
Q
What is the key function of the endocrine system?
A
To maintain homeostasis & regulate long-term processes
- Growth, metabolism, development, reproduction
3
Q
What are hormones?
A
Chemical messengers to relay information & instructions to cells (signalling)
4
Q
What are the mechanisms of intercellular communication?
A
- Direct communication
- Paracrine communication
- Autocrine communication
- Endocrine communication
- Synaptic communication
5
Q
Where does transmission occur and what are the chemical mediators for direct communication?
A
Transmission: through gap junctions
Chemical mediators: ions, small solutes, lipid-soluble materials
6
Q
What are the distribution effects of direct communication?
A
Usually limited to adjacent cells of the same type that are interconnected by connexons (protein that forms channels to connect cytoplasm of adj cells)
7
Q
Where does transmission occur and what are the chemical mediators for paracrine communication?
A
Transmission: Through extracellular fluid
Chemical mediators: Paracrines
8
Q
What are the distribution effects of paracrine communication?
A
Primarily limited to a local area
- where paracrine conc. are relatively high
- target cells must have appropriate receptors
9
Q
Where does transmission occur and what are the chemical mediators for autocrine communication?
A
Transmission: Through extracellular fluid
Chemical mediators: Autocrines
10
Q
What are the distribution effects of autocrine communication?
A
Limited to the cell that secretes the hormone
- Secretes chemical messenger that binds to receptor on same cell
- purpose is to dec. prod./secretion of particular chemical
11
Q
Where does transmission occur and what are the chemical mediators for endocrine communication?
A
Transmission: Through the bloodstream
Chemical mediators: Hormones
Same as paracrine communication but dist. travelled is diff (endocrine comm. travels to cells/systems located far away
12
Q
What are the distribution effects of endocrine communication?
A
Target cells are primarily in other tissues & organs and must have appropriate receptors
13
Q
Where does transmission occur and what are the chemical mediators for synaptic communication?
A
Transmission: Across synapses
Chemical mediators: Neurotransmitters
Specifically targets NS = binds to neurons while hormones can bind to a range of diff cells & tissues
14
Q
What are the distribution of effects of synaptic communication?
A
Limited to very specific area
- target cells must have appropriate receptors
15
Q
What are the classes of hormones?
A
Hydrophilic (attracted to water)
Lipophilic (attracted to lipids)
16
Q
What are the hydrophilic hormones?
A
- Peptide hormones (most abundant)
- Catecholamines
- Indoleamines
17
Q
What are peptide hormones derived from?
A
Derived from diverse types of a.a.
- Slower response but longer lasting effect
- e.g. insulin/growth hormone
18
Q
What are catecholamines derived from?
A
A.a. tyrosine
- Faster effect but shorter life
- e.g. dopamine
19
Q
What are indoleamines derived from?
A
a.a. tryptophan
20
Q
Can lipophilic hormones travel freely within bld. circulation?
A
NO!
- Requires carrier protein to help with tpt.
21
Q
What are the lipophilic hormones?
A
Steroid hormones
Thyroid hormones
22
Q
What are steroid hormones derived from?
A
cholesterol
23
Q
What are thyroid hormones derived from?
A
a.a. tyrosine & iodine
24
Q
Difference between functions of steroid hormones & thyroid hormones
A
Steroid hormones = more functions (diverse) = reproduction, metabolism, regulate stress resp
Thyroid hormones = more limited functions = regulating metabolism, growth, development
25
What are tropic hormones?
Tropic hormones target endocrine glands to regulate the activity of specific glands/release of certain hormones from those glands
26
Features of the endocrine system (complexity)
1. One endocrine gland may secrete > 1 hormone (e.g. ant. pituitary)
2. One hormone may be secreted by > 1 endocrine gland (e.g. somatostatin)
3. One hormone may have > 1 target cell = >1 type of action (e.g. vasopressin = aka ADH)
4. One target cell may be influenced by >1 hormone
5. Some have non-endocrine functions
6. Rate of secretion of hormones may vary over time in a cyclic pattern (melatonin)
7. Some may be hormones AND neurotransmitters (noradrenaline)
27
What affects effective plasma concentration?
- Rate of hormone secretion = more availability of hormones in bld circulation
- Rate of metabolic conversion/activation (broken down/converted to other forms)
- Transportation (extent of binding to plasma proteins) = X affect hydrophilic hormones bc can travel in blood
- Rate of removal by excretion/metabolic inactivation
28
What is hormone secretion triggered by?
- Humoral (change in extracellular fluid)
- Hormonal (arrival/removal of hormone)
- Neural stimuli (neurotransmitters)
29
What affects hormone secretion?
- -ve feedback control = "turning off" (output of system counteracts a change in inputs)
- Neuroendocrine reflexes (fight/flight)
- Circadian/Diurnal rhythm (24 oscillation) or Time-based (menstrual)
30
How long do free hormones remain functional?
less than 1 hour
31
How long do thyroid & steroid hormones remain in circulation?
Remain in circulation much longer bc most are "bound" (usually lipophilic hormones)
- Involved long-term changes (e.g. growth/development)
32
How does hormone receptors affect hormone secretion?
- Different receptors for different hormones (specificity)
- One target organ can have multiple hormone receptors (e.g. liver)
- Presence/absence = receptor expression determines hormonal sensitivity (amt of receptors on surface can be controlled = if need more, more receptors will be avail)
33
What alters hormonal response?
Upregulation/downregulation (increasing/decreasing no. of receptors)
Locally-acting -ve feedback loop = desensitization (e.g. insulin hypersecretion = reduced sensitivity over time)
34
Antagonistic hormone interaction
opposite effect = one hormone may lead to the loss of another hormone receptor = binding of one hormone to receptor leads to disappearance of another hormone: suppress
35
Synergistic hormone interaction
Additive effect = encourage binding of 2 or more hormones to same target cells
36
Permissive hormone interaction
One is needed for another to produce effect
- For hormone B to bind to receptor, hormone A has to be present (in adequate amt)
37
Integrative hormone interaction
Different but complementary results
38
What are the types of hormone interaction?
1. Antagonistic
2. Synergistic
3. Permissive
4. Integrative
39
Types of endocrine disorders
1. Hyposecretion
2. Hypersecretion
3. Abnormal target cell responsiveness
40
What is hyposecretion (endocrine disorders)?
Primary or secondary (tropic hormone)
Genetic, dietary, toxins, immunologic, dz, iatrogenic, idiopathic
41
What is hypersecretion (endocrine disorders)?
Tumours, immunologic (antibody), substance abuse
- Receiving wrong info = give impression that need to secrete more
42
What is abnormal target cell responsiveness (endocrine disorders)?
Genetic = e.g. testicular feminization syndrome
- testosterone receptors somehow reduced (even if there is enough hormones, not enough receptors = less availability of hormone receptor)
43
What are the central endocrine glands?
1. Hypothalamus
2. Anterior pituitary (Adenohypophysis)
3. Posterior pituitary (Neurohypophysis)
4. Pineal gland
44
Most anterior pituitary hormones are _________
Most anterior pituitary hormones are tropic
45
What is the role of the hypothalamus?
1. Work with post. pituitary to secrete vasopressin & oxytocin
2. Secrete hypothalamic releasing/inhibiting hormones to act on ANTERIOR pituitary gland
3. Control of sympathetic output = neuroendocrine reflex
- Connects nervous system & endocrine system
46
What are vasopressin (ADH) & oxytocin produced by?
Neurosecretory neurons in hypothalamus
- Made in hypothalamus but secreted by posterior pituitary gland
47
What is the supraoptic nucleus (SON) involved in?
Involved in systemic hormone release
- basically making & secreting
48
What does the paraventricular nucleus (PVN) regulate?
- Regulate how much ADH & oxytocin being secreted
- Regulates how much can be released by SON
49
Where do the axons between the hypothalamus & anterior pituitary terminate?
Axons crosses the pituitary stalk to terminate on capillaries in posterior pituitary
50
What is transported along the axon?
Secretory granules transport the hormones along axon, stored at neuronal terminals
51
Functions of vasopressin (ADH)
- Inc. permeability of distal & collecting tubules to H2O (in nephrons in kidneys)
- Causes vasoconstriction (arterioles throughout body)
Aka "water conserving" hormone
52
Functions of oxytocin
- Stimulates uterine contractions (in uterus)
- Stimulates milk ejection during breast-feeding (mammary glands)
53
What hormones does the anterior pituitary gland produce?
1. Growth hormone (GH)
2. Thyroid stimulating hormone (TSH)
3. Adrenocorticotropic hormone (ACTH)
4. Follicle-stimulating hormone (FSH)
5. Luteinizing hormone (LH)
6. Prolactin (PRL)
54
What type of cell produces the growth hormone (GH)?
Somatotropes
55
What type of cell produces the thyroid stimulating hormone (TSH)?
Thyrotropes
56
What type of cell produces adrenocorticotropic hormone (ACTH)?
Corticotropes
57
What type of cell produces FSH & LH?
Gonadotropes
58
What type of cell produces prolactin?
Lactotropes
59
Function of growth hormone?
Overall body growth
- Acts on liver = stimulates release of IGF-I which acts on bone & soft tissue = growth
- Acts on adipose tissue, muscle, liver (can inc./dec. stimulation) = metabolic actions
60
Function of TSH
Stimulate secretion of thyroid hormone & growth of thyroid gland
- Stimulates the thyroid gland = release of thyroid hormone (T3 & T4) = inc. metabolic rate
61
Function of ACTH
Stimulates secretion of cortisol & growth of adrenal cortex
- Stimulates the Adrenal cortex = release cortisol = metabolic actions, stress response
62
Function of FSH, LH
Regulates gonad function
FSH - gametes production (ova, sperm)
LH - regulate sex hormones' secretion, ovulation, luteinization
LH & FSH stimulates gonads (ovaries in females & testes in males) = sex hormone secretion (estrogen & progesterone in females, testosterone in males) & gamete production (ova in females & sperm in males)
63
Function of PRL?
Lactation
- Prolactin stimulates mammary glands = breast growth & milk secretion
64
What hormones does the hypothalamus produce?
1. Growth hormone releasing hormone (GHRH)
2. Somatostatin (GH-inhibiting hormone) (GHIH)
3. Corticotropin-releasing hormone (CRH)
4. Gonadotropin-releasing hormone (GnRH)
5. Prolactin-releasing peptide (PrRP)
6. Dopamine (PRL-inhibiting hormone (PIH)
65
Actions of growth hormone releasing hormone (GHRH)
Stimulates release of GH (growth hormone)
66
Actions of Thyrotropin-releasing hormone (TRH)
Stimulates release of TSH (Thyroid stimulating hormone), PRL (Prolactin)
67
Action of Corticotropin-releasing hormone (CRH)
Stimulates release of ACTH (Adrenocorticotropic hormone)
68
Action of Somatostatin (GH-inhibiting hormone) (GHIH)
Inhibits release of GH, TSH
Inhibits secretion of insulin & glucagon
Dec. utilization of absorbed nutrients by tissues
69
Action of Gonadotropin-releasing hormone (GnRH)
Stimulates release of FSH & LH
70
Action of Prolactin-releasing peptide (PrRP)
Stimulates release of PRL
71
Action of Dopamine (PRL-inhibiting hormone)
Inhibits release of PRL
72
What does the unique vascular link between the hypothalamus & anterior pituitary gland help with?
Makes communication b/w these 2 structures more efficient
- bc. hormones come from hypothalamus can directly signal & regulate how much hormone is being released from the pituitary gland itself
- More rapid speed of communication faster bc. structurally connected
73
How are hormones transported from hypothalamus to anterior pituitary gland?
1. Hypophysiotropic hormones (releaing hormones & inhibiting hormones) produced by neurosecretory neurons in the hypothalamus enter the hypothalamic capillaries
2. Hypothalamic capillaries rejoin to form the hypothalamic-hypophyseal portal system = a vascular link to anterior pituitary
3. The portal system branches into the capillaries of the anterior pituitary
4. The hypophysiotropic hormones = leave blood across ant. pituitary capillaries = control release of ant. pituitary hormones
5. When stimulated by appropriate hypothalamic releasing hormone, ant. pituitary secretes a given hormone into these capillaries
6. The ant. pituitary capillaries rejoin to form a vein, through which ant. pituitary hormones leave for ultimate distribution throughout the body by systemic circulation
74
How do hormones travel from hypothalamus to target cells?
1. Neural input/hormonal input stimulate/inhibit hypothalamic neurosecretory neuron
2. Hypothalamic neurosecretory neuron secretes hormone 1
3. Hormone 1 travels through the special short portal system to the anterior pituitary gland
4. Stimulates/inhibits anterior pituitary gland to secrete hormone 2
5. Hormone 2 enters systemic circulation
6. Hormone 2 reaches target endocrine gland and secretes hormone 3
7. Hormone 3 travels to target cells = physiological effect
- negative feedback to anterior pituitary (signal to dec. prod of hormone 2 if too much & vice versa)
- negative feedback to hypothalamic neurosecretory neuron (stimulate inhibiting hormone for hormone 2)
75
Pathway of cortisol secretion
1. Hypothalamus secretes hypophysiotropic hormone (CRH)
2. CRH acts on anterior pituitary
3. Anterior pituitary secretes tropic hormone: ACTH
4. ACTH acts on adrenal cortex
5. Adrenal cortex releases cortisol
- cortisol negatively feedbacks anterior pituitary & hypothalamus
76
What does growth depend on?
1. Growth hormone
2. Genes
3. Diet
4. State of health/other env. stressors
5. other hormones (e.g. Thyroid hormone)
77
How does growth hormone affect growth?
- Exerts metabolic effects by binding directly to adipose tissue, skeletal muscles & liver = fat mobilisation
- Indirect effects to aid growth = stimulate IGFs (Insulin growth factor) = hypertrophy (cell size) & hyperplasia (cell numbers)
- Stimulates bone growth = thickness & length
78
What are the factors that influence growth hormone secretion?
Diurnal rhythm, exercise, stress, food
79
What happens with growth hormone deficiency?
Hyposecretion = Dwarfism
80
What happens with growth hormone excess?
Hypersecretion = Gigantism, Acromegaly
81
What stimulates growth hormone secretion?
1. Exercise, stress, dec. bld. glucose, diurnal rhythm + inc. bld a.a., dec. bld. fatty acids, ghrelin stimulates the hypothalamus
2. Stimulates somatostatin (growth hormone-inhibiting hormone, GHIH) or Growth hormone-releasing hormone (GHRH)
3. Stimualtes ant. pituitary somatotrope
4. releases GH
82
What is the effect growth hormone secretion?
Stimulates liver to produce IGF-I = growth-promoting actions:
- inc. protein synthesis (dec. bld a.a.)
- cell division
- bone growth
Metabolic actions unrelated to growth:
- inc. fat breakdown (inc. blood fatty acids)
- Dec. glucose uptake by muscles (inc. bld glucose)
- Inc glucose output by liver (inc. bld. glucose)
83
What hormones (other than GH) are essential for normal growth?
- Thyroid hormone
- Insulin
- Sex steroids (e.g. androgens & estrogen)
84
What is the master biological clock?
Suprachiasmatic nucleus (SCN)
85
Where is the suprachiasmatic nucleus (SCN) located?
In hypothalamus above optic chiasm (where the optic nerve crosses)
86
When does the SCN fire?
Self-induced rhythmic firing = fluctuating levels of clock proteins
- Synchronisation of biological clock w env. cues (e.g. light-dark cycle)
87
What senses daylight/darkness?
Melanopsin
- helps to regulate SCN (Suprachiasmatic nucleus)
88
Pathway to reset circadian rhythms to match light-dark cycle?
1. Melanopsin-containing retina ganglion cells detect light/dark
2. Stimulates the suprachiasmatic nucleus
3. SCN stimulates the pineal gland
4. Pineal gland dec. melatonin in the light or inc. melatonin in the dark
5. Cyclic changes in melatonin
6. Resets circadian rhythms to match light-dark cycle
89
What is the hypophyseal portal system?
Network of blood vessels that connects the hypothalamus to the pituitary gland
90
Where is the thyroid gland located?
Lies inferior to thyroid cartilage of larynx
91
How many lobes does the thyroid gland consist of?
Two lobes
Connected by narrow isthmus
92
How are the major cells that secrete thyroid hormone organised?
Organised into colloid-filled follicles
- Interspersed in the interstitial spaces b/w follicles are C cells (aka parafollicular cell), which secrete calcitonin (lower bld Ca2+)
93
Where is thyroid hormone stored?
On the thyroglobulin molecule = functions more like a carrier protein = bc. thyroid hormone is lipophilic
- Most steps of thyroid hormone synthesis take place on the thyroglobulin molecules within the colloid
94
Difference between Thyroxine (T4) and Triiodothyronine (T3)?
Almost the same functionality =
only diff is how fast they react & potency
95
What is the thyroid gland stimulated by?
Thyroid stimulating hormone secreted by the ant. pituitary gland
96
Where is the thyroid hormone synthesized?
Within the follicles
97
What is the inactive form of Triiodothyronine (T3)?
T4 (thyroxine)
When T3 is needed, T4 will be converted to active T3
98
Percentage of Thyroxine (T4) and Triiodothyronine (T3)
Thyroxine (T4) = 93%
Triiodothyronine (T3) = <7%
99
Which has a higher potency: Triiodothyronine (T3) vs Thyroxine (T4)
T3 more potent than T4
100
Which has a longer shelf life:
Triiodothyronine (T3) vs Thyroxine (T4)
T4 longer half life (inversely proportionate to potency)
101
What happens if there is no thyroid-stimulating hormone (TSH)?
Follicle will be inactive = X synthesize & secrete thyroid hormones
102
Function of thyroid hormones?
Activates genes involved in glycolysis & ATP production
- Results in calorigenic effect = inc. energy consumption & heat generation of cells + resp. for strong, immediate, short-lived inc. in rate of cellular metabolism
103
How many iodine molecules are there in Triiodothyronine (T3) and Thyroxine (T4)?
T3 = 3 iodine molecules
T4 = 4 iodine molecules
104
Steps in the synthesis, storage & secretion of thyroid hormone
1. Thyroglobulin synthesized (ferry thyroid hormone into circulation)
2. Iodide move from blood to colloid
3. Iodide is oxidized by TPO (thyroid peroxidase)
4. Monoiodotyrosine + Di-iodotyrosine = T3
5. Di-iodotyrosine + Di-iodotyrosine = T4
6. Follicular engulf Thyroglobulin-containing colloid
7. Iodide products split from Tg
8. Monoiodotyrosine & Di-iodotyrosine are deiondinated
9. Thyroxine-binding globulin (TBG) binds T3 and T4
105
Thyroid hormones have _____________ onset and _____________ duration of action
Thyroid hormones have slow onset and long duration of action
- bc. lipophilic
106
What are the effects of thyroid hormone?
Thyroid hormones inc. metabolism in almost all cells of the body
- Excessive quantities of thyroid hormone can (occasionally) inc. basal metabolic rate by 60% to 100% above normal
- When X thyroid hormone produced = basal metabolic rate falls to almost one-half of normal
107
What are the physiological functions of the thyroid hormones?
Synthesis of new proteins =
- Many other systems
- Growth (stimulates secretion of growth hormone)
- CNS development (sympathomimetic effect)
- Cardiovascular
- Metabolism
Net result = generalized inc. in functional activity throughout body
108
What are the physiological functions - Cardiovascular - of the thyroid hormones?
- inc. cardiac output
- inc. tissue bld. flow
- inc. heart rate
- inc. heart strength
- inc. resp.
- inc. force of contraction
109
What are the physiological functions - Metabolism - of the thyroid hormones?
- Inc. mitochondria
- Inc. Na+-K+-ATPase
- Inc. O2 consumption
- Inc. glucose absorption
- Inc. Gluconeogenesis
- Inc. Glycogenolysis
- Inc. Lipolysis
- Inc. Protein synthesis
- Inc. Basal Metabolic Rate
110
Pathway of regulation of thyroid secretion
Inc. thyroid hormone in body fluids dec. TSH secretion by ant. pituitary
1. If too much TSH secreted = -ve feedback = signal to anterior loop to dec. secretion of TSH = thyroid gland less stimulated = less thyroid hormone synthesized
2. direct -ve feedback to hypothalamus = dec. thyrotropin-releasing hormone (TRH) = dec. TSH secreted = thyroid hormone X stimulated
111
What are the types of thyroid dysfunction?
1. Hypothyroidism
2. Hyperthyroidism
112
What are the causes of hypothyroidism?
- Primary failure of the thyroid gland
- Secondary to hypothalamic/ant. pituitary failure
- Lack of dietary iodine
113
Primary failure of thyroid gland:
Plasma conc. of relevant hormones &
Presence of goiter
Plasma conc. =
- Dec T3 & T4 (bc. thyroid gland X functioning = dec. thyroid hormone stimulated = stimulate ant loop to prod more TSH =
- Inc. TSH
Goiter present (bc. Inc. TSH leads to goiter)
114
Secondary to hypothalamic/anterior pituitary failure:
Plasma conc. of relevant hormones &
Presence of goiter
Plasma conc. =
- Dec. T3 & T4
- Dec. TRH and/or dec TSH
Goiter not present (bc. thyroid gland not stimulated
115
Lack of dietary iodine:
Plasma conc. of relevant hormones &
Presence of goiter
Plasma conc. =
- Dec. T3 & T4 (bc. building block --> iodine absent)
- Inc. TSH
Goiter present
116
Abnormal presence of thyroid-stimulating immunoglobulin (TSI) (aka Graves' dz)
Plasma conc. of relevant hormones &
Presence of goiter
Plasma conc. =
- Inc. T3 & T4
- dec. TSH (thyroid gland stimulated by TSI --> similar to TSH)
Goiter present
117
Secondary to excess hypothalamic/ant. pituitary secretion
Plasma conc. of relevant hormones &
Presence of goiter
Plasma conc. =
- Inc. T3 & T4
- Inc TRH and/or Inc TSH
Goiter present
118
Hypersecreting thyroid tumour
Plasma conc. of relevant hormones &
Presence of goiter
Plasma conc. =
- Inc. T3 & T4
- Dec. TSH (therefore no goiter)
No goiter
119
What causes the presence of goiter?
Develops when thyroid gland is overstimulated
so no overstimulation = no goiter
120
What is the adrenal glands composed of?
Adrenal cortex
Adrenal medulla
121
What are the three layers of the adrenal cortex?
1. Zona glomerulosa
2. Zone fasciculata
3. Zona reticularis
122
Where is aldosterone secreted from?
Adrenal cortex (zona glomerulosa)
123
Where is cortisol secreted from?
Adrenal cortex (zona fasciculata)
124
Where is adrenal androgens such as Dehydroepiandrosterone (DHEA) secreted from?
Adrenal cortex (zona reticularis)
125
Where is adrenaline/noradrenaline secreted from?
Adrenal medulla
126
Action of aldosterone
- Sodium & Potassium balance
- Blood pressure homeostasis
127
What is the action of cortisol?
- Adaptation to stress
- Metabolic regulation
- Anti-inflammatory effects
128
Action of DHEA
Early development of sex organs
129
Action of adrenaline/noradrenaline
- Reinforces the sympathetic nervous system
- Inc. HR
130
What is cortisol secretion regulated by?
Hypothalamus-pituitary-adrenal cortex axis
131
Pathway for the secretion of cortisol
1. Stress excites hypothalamus
2. Hypothalamus stimulates the anterior pituitary gland
3. ACTH secreted and acts on adrenal cortex
4. Adrenal cortex secretes cortisol
5. Cortisol physiological effects:
- Gluconeogenesis
- Protein mobilization
- Fat mobilization
- Stabilize lysosomes
- If too much cortisol = -ve feedback to ant. pituitary gland & hypothalamus
132
What physiological effects does cortisol have to reduce stress?
- Inc. bld. glucose = by stimulating gluconeogenesis & inhibit glucose uptake
- Inc. bld. a.a. = by stimulating protein degradation
- Inc. bld. fatty acids = by stimulating lipolysis
133
What does the adrenal medulla consist of?
Modified sympathetic postganglionic neurons
134
How do adrenaline (epinephrine) and noradrenaline (norepinephrine) differ?
Adrenaline = relatively non-specific = bind to both alpha & beta receptor types almost equally well
Noradrenaline = binds to mostly alpha receptor but can bind to beta receptors to a certain degree
- Functions similar!
135
When is adrenaline released and what does it reinforce?
Released only on sympathetic stimulation of adrenal medulla
Reinforces the sympathetic NS & exerts metabolic effects
136
Percentage of adrenaline & noradrenaline produced by adrenal medulla?
~75% of adrenaline
<25% of noradrenaline
137
Are adrenaline or noradrenaline produced in greater amounts by neurons?
Mostly noradrenaline
Small amts of adrenaline
138
How are adrenaline/noradrenaline transported when made in adrenal medulla?
Hormone = travel longer dist. to diff parts of the body
139
How are adrenaline/noradrenaline transported when made in neurons?
Neurotransmitter = interact w next neuron (shorter dist)
140
What are some adrenal gland disorders?
- Aldosterone hypersecretion (E.g. Conn's syndrome)
- Cortisol hypersecretion (e.g. Cushing's dz/syndrome)
- Adrenal androgen hypersecretion (e.g. Polycystic ovary syndrome = PCOS)
- Adrenocortical insufficiency (e.g. Addison's dz)
141
What is aldosterone hypersecretion associated with?
- Hypokalemia
- Inc. bld. vol
- Inc. plasma Na+
- Inc. BP
142
Pathway of epinephrine secretion
- Stressor stimulates the hypothalamus
- Hypothalamus stimulates the sympathetic nervous system
- Sympathetic nervous system stimulates the adrenal medulla which increases the secretion of epinephrine
- epinephrine prepares body for "fight/flight", mobilize energy stores & metabolic building blocks for use as needed, stimulates arteriolar smooth muscle to vasoconstrict = dec. bld flow through kidneys
143
What tissues is the pancreas made up of?
- Acini
- Islets of Langerhans
144
Which is the endocrine portion of the pancreas?
Islets of Langerhands
145
Which is the exocrine portion of the pancreas?
Acinar & Duct cells
- Acinar cells secrete digestive enzymes
- Duct cells secrete aqueous NaHCO3 solution
146
Which pancreatic hormones are the most important in regulating fuel metabolism?
Insulin & Glucagon
(secreted by islets of Langerhans)
147
What is human insulin composed of?
Two a.a. chains
- Connected to e/o by disulfide linkages
- When the two a.a. split apart, insulin's functional activity is lost (to be functional = must be connected in the right place)
148
Pathway for insulin secretion
- Food intake causes inc. in blood glucose conc. (major control)
- Stimulates islet beta cells to secrete insulin
- Inc. bld. a.a. conc. & inc. gastrointestinal hormones (incretins) stimulate islet beta cells to secrete insulin too
- Dec. bld. glucose, dec. bld. fatty acids, dec. bld. a.a., inc. protein synthesis, inc fuel storage
149
slide 24
150
What is hyperglycemia?
Abnormally high glucose levels in bld.
151
What is diabetes mellitus characterized by?
High glucose conc. that overwhelms reabsorption capabilities of kidneys
- Glucose appears in urine
- Polyuria = urine vol. becomes excessive
- Type I and II
152
What does an excess of insulin cause?
Brain-starving hypoglycemia
153
When is glucagon secretion increased?
Postabsorptive state (fasting state)
154
Pathway of glucagon secretion
- Dec. blood glucose stimulates alpha cells to release glucagon
- Increase in glucagon
- Inc. bld. glucose to normal
Vice versa for high bld. glucose level
155
What does an elevation in blood glucose levels?
Elevated blood glucose stimulates insulin secretion, but inhibits glucagon secretion
156
Where is somatostatin produced?
- pancreas
- hypothalamus
157
What do the parathyroid glands do?
- Regulate calcium levels in blood
158
Calcium homeostasis is closely associated with ________ homeostasis
Calcium homeostasis is closely associated with phosphate homeostasis
159
Why must plasma Ca2+ be closely regulated?
Prevent changes in neuromuscular excitability
Control of Ca2+ metabolism incl. regulation of Ca2+ homeostasis & Ca2+ balance
160
What raises free plasma Ca2+?
Parathyroid hormone (PTH)
161
What increases & decreases blood calcium levels?
PTH acts to inc. bld Ca2+ levels
Calcitonin acts to dec. bld. Ca2+ levels
162
Bone is continually being deposited by ___________ and it is continually being reabsorbed where ___________ are active
Bone is continually being deposited by osteoblasts and it is continually being reabsorbed where osteoclasts are active
163
What are osteoblasts responsible for?
Synthesis & mineralization of bone
- lead to dec. availability of free Ca2+
164
What do osteoclasts do?
Break down bone tissue
- lead to inc. availability of free Ca2+
165
Where are osteoblasts derived from?
Precursor cells in bone marrow
166
What can affect osteoclast development?
Osteoblasts & their precursor products:
- RANK ligand (RANKL)
- Osteoprotegerin (OPG)
^ these two are proteins = will determine whether it will lead to inc./dec. bone mass
167
Pathway to decrease bone mass
- Osteoblasts & their precursors secrete RANK ligand (RANKL) (& OPG)
- RANKL will bind to macrophages/osteoclasts (RANK receptor)
- Binding triggers: differentiation of macrophages into osteoclasts & suppression of osteosclasts apoptosis
- Both of these ^ increase osteoclast action
- Osteoclast action outpaces osteoblast action (basically, osteoclast break down the bones faster than osteoblast can create)
- dec. bone mass
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Pathway to increase bone mass
- Osteoblasts & their precursors secrete osteoprotegerin (OPG) & RANKL
- RANKL binds to OPG (RANKL bound to OPG not available to bind with RANK)
- Blocks the action of RANK
- Dec. osteoclast action
- Osteoblast action outpaces osteoclast action (basically, osteoblasts make bone faster than osteoclast breakdown)
- inc. bone mass
Basically, limit the RANKL = cannot bind to RANK receptor = osteoclast cannot breakdown bones = osteoblast can work faster than osteoclast breaks down
169
What does mechanical stress favours?
Bone deposition
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What does increased PTH (Parathyroid hormone) do?
Increase osteoclast activity
= Increased blood calcium level
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What does increased calcitonin do?
- Increase osteoblast activity
= Reduced bld. calcium level
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What does PTH (parathyroid hormone) do?
- Raises plasma Ca2+
- promote localized dissolution of bone = release Ca2+ into plasma
- Act on kidneys
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What does activation of vitamin D3 form?
1,25-dihydroxycholecalciferol (calcitrol)
- Activation needs 2 enzymes
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What does vitamin D increase?
Increases Ca2+ absorption in the intestine
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Vitamin D vs PTH
Vitamin D primarily focus on increasing Ca2+ ability by promoting the Ca2+ absorption
PTH = more rapid respondent = if need to inc. Ca2+ = stimulate their release from the bone
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What is the indirect effect of PTH?
Promotes absorption of Ca2+ & PO4^3- (phosphate)
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Pathway to increase plasma PO4^3- (phosphate)?
1. (PTH)
- Plasma Ca2+ will increase (bc of inverse r/s b/w plasma PO4^3- & Ca2+ conc. caused by solubility characteristics of calcium phosphate salt
- Plasma Ca2+ will inhibit parathyroid glands
- Decrease in PTH
- Inc. PO4^3- reabsorption by kidneys = dec. urinary excretion of PO4^3- = inc. plasma PO4^3-
- Dec. Ca2+ reabsorption by kidneys = inc. urinary excretion of Ca2+ = (counteract with inc. Ca2+ absorption in intestine) = no change in plasma Ca2+
2. (kidney)
- Kidneys stimulated to secrete more activated vitamin D
- Inc Ca2+ absorption in intestine = Counteracts with inc. urinary excretion of Ca2+ = no change in plasma Ca2+
- inc. activated vitamin D = inc. PO4^3- absorption in intestine = inc. plasma PO4^3-
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Where is the parathyroid hormone secreted from?
Parathyroid gland
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What is the action of the parathyroid gland?
Increased plasma calcium level
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Where is calcitonin secreted from?
Thyroid gland
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Where is vitamin D (calcitriol) secreted from?
Kidneys (turning vit D to its active form)
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What is the action of parathyroid hormone?
Increased plasma calcium level
183
What is the action of calcitonin?
Reduced plasma calcium level
184
What is the action of vitamin D (aka calcitriol)?
Increased calcium absorption (intestine)
185
What may cause disorders in Ca2+ metabolism to arise?
Abnormal levels of PTH/Vitamin D
186
What is PTH hypersecretion?
Excess PTH secretion = primary/secondary
187
What is PTH hyposecretion?
Deficient PTH secretion = hypoparathyroidism
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What is the major consequence of vitamin D deficiency?
Impaired intestinal absorption of Ca2+
- may lead to rickets (inadequate mineralization of bones)
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What cell secretes somatostatin?
Delta cell
