Intercellular Communication and Principal of Endocrinology Flashcards
1
Q
Communication of cells with each other is essential for..
A
- coordinating their diverse activities
- maintain homeostasis
- growth of cell
- development of the body as a whole
2
Q
Types of cell communication
A
intracellular and intercellular
3
Q
Intracellular control of cellular function
A
communication within cells of the body e.g. synthesis of NTs needs communication between RER,SER, ribosome,etc.
4
Q
Intercellular (extra-) control of cellular function
A
communication between the cells of the body e.g. release of ACTH during stress causes release of cortisol
5
Q
Types of intercellular (extra-) communication
A
direct and indirect
6
Q
Direct intercellular
A
gap junction
- cells are in close vicinity
7
Q
Indirect intercellular
A
involve 4 types of chemical messengers: paracrine, NT secretion, hormonal secretion, neurohormone secretion
- cells are far apart
- involve ECF
8
Q
Direct intercellular communication: gap junctions
A
- intimate way of communication
- achieved through “signalling molecules” on the surface of a cell
- possesses identifying ‘markers’ on cell membranes
- does not involve ECF
- e.g. phagocytes recognize and destroy bacteria and invaders
- e.g. antibodies “marked” bacteria as foreigners to destroy them
9
Q
Paracrine
A
- local chemical messenger exerts their effects on neighbouring cells in an immediate environment
- chemical messengers use simple diffusion and act at a short distance
- do not gain entry into the blood
- e.g. histamine release causes vasodilation of the neighbouring blood vessel
10
Q
Neurotransmitters
A
- short-range chemical messengers
- diffuse across narrow space to act locally on adjoining target cell (another neuron, muscle or ligand)
11
Q
Hormones
A
- long-range chemical messengers
- secreted into blood by endocrine glands in response to an appropriate signal
- exert effect on target cells some distance away from release site
- e.g. GH only binds to muscles and bones in the body
12
Q
Neurohormones
A
- hormones are released into the blood by neurosecretory neurons
- distributed through the blood to distant target cells e.g. ADH (vasopressin- released when suffering dehydration) and oxytocin (helps bonding in newborns and mom)
13
Q
Signal transduction
A
- the combination of extracellular chemical messenger with its membrane receptors triggers a sequence of intracellular events for particular cellular activities (i.e. transport, secretion, metabolism and contraction)
- converting one chemical signal to another using energy
14
Q
Chemical messenger’s action on target cell
A
endocrine cells –> first (extracellular) chemical messenger –> blood –> target cell –> receptors –> respond by closing/opening specific channels in the membrane and releasing second messengers like cAMP, Ca2+-PIP2 and cGMP
15
Q
First messenger
A
- extracellular chemical messenger binds to receptors
- open/close the specific channels to regulate the movement of a particular ion in and out of the cell OR transfer extracellular chemical messenger to the second messenger
16
Q
Second messenger
A
triggers a preprogrammed series of the biochemical events within the cell (located inside the target tissue)
17
Q
Mechanism of action of hydrophilic hormones via activation of the cyclic AMP second-messenger system
A
- binding of extra-cellular messenger to receptor activates a G protein, the alpha subunit of which shuttles to and activates adenylyl cyclase
- adenylyl cyclase converts ATP to cAMP
- cAMP activates protein kinase A
- protein kinase A phosphorylates inactive target protein, activating it
- active target protein brings about desired response
18
Q
Functions of cAMP
A
- modification of heart rate
- formation of female sex hormones in the ovaries
- breakdown of stored glucose in the liver
- reception of a sweet taste by a taste bud
- conservation of water during urine formation
19
Q
Activation of the calcium second-messenger system by an extracellular messenger
A
- binding of extracellular messenger to receptor activates a G protein, the alpha subunit of which shuttles to and activates phospholipase C
- Phospholipase C converts PIP2 to IP3 and DAG
3a. IP3 mobilizes intracellular Ca2+
3b. DAG activates protein kinase C
4a. Ca2+ activates calmodulin
4b. Protein kinase C phosphorylates inactive target protein, activating it
5a. Ca2+- calmodulin complex activates Ca2+- calmodulin-dependent protein kinase (CaM kinase)
5b. active target protein brings about desired response
6a. CaM kinase phosphorylates inactive target protein, activating it
7a. active target protein brings about desired response
20
Q
cGMP (cyclic guanosine monophosphate)
A
in a few cells, cyclic GMP serves as a second messenger in a system analogous to the cAMP system e.g. the signal transduction pathway involved in vision
21
Q
The functions of the endocrine glands (hormones)
A
- regulate metabolism, water and electrolyte balance by acting on the kidneys e.g. aldosterone
- induce adaptive changes to help the body cope with stressful situations e.g. cortisol
- promote growth and development e.g. GH
- control reproduction e.g. FSH and LH
- regulate blood cell production e.g. erythropoietin
- endocrine and ANS control and regulate both circulation, digestion and absorption of food in GI e.g. gastrin, CCK
22
Q
the plasma concentration of free, biologically active hormone, which can interact with its target cells to produce a physiological response, depends on…
A
- the hormone’s rate of secretion by the endocrine gland
- its rate of metabolic activation
- its extent of binding to plasma proteins (lipophilic hormones)
- its rate of metabolic inactivation and excretion
23
Q
POMC (pre-pro melanocortin) when cleaved produces active hormones:
__, ___ and ___ which target the ___, ___ and ___ respectively, and that will cause the release of __, __ ___, __ ___
A
POMC (pre-pro melanocortin) when cleaved produces active hormones:
ACTH, MSH and beta-endorphin which target the adrenal gland, melanocytes and analgesic respectively, and that will cause the release of cortisol, skin color, pain relief
24
Q
Steroid hormones
A
- includes hormones secreted by the adrenal cortex, gonads and placenta
- are derivatives of cholesterol
- these hormones do not store in cells once formed and are released in blood immediately via lipid soluble plasma membrane
- these hormones undergo interconversion in blood or in other organs e.g. progesterone becomes cortisol
25
Amines/catecholamines
- derived from the amino acid tyrosine
- include the hormones secreted by the thyroid and adrenal medulla
- enzymes synthesizing these hormones are not located in cell organelles
- both amines are stored in the cell until their secretion
26
Solubility: peptides
hydrophilic
27
Structure: peptides
chains of specific amino acids
28
Synthesis: peptides
in rough endoplasmic reticulum, packaged in Golgi complex
29
Storage: peptides
large amounts in secretory granules
30
Secretion: peptides
exocytosis of granules
31
Transport in blood: peptides
as free hormone
32
Receptor site: peptides
surface of target cell
33
Mechanism of action: peptides
channel changes or activation of second-messenger system to alter activity of target proteins that produce the effect
34
Hormones of this type: peptides
majority of hormones
35
Solubility: catecholamines
hydrophilic
36
Structure: catecholamines
tyrosine derivative
37
Synthesis: catecholamines
in cytosol
38
Storage: catecholamines
in chromaffin granules
39
Secretion: catecholamines
exocytosis of granules
40
Transport in blood: catecholamines
half bound to plasma proteins
41
Receptor site: catecholamines
surface of target cell
42
Mechanism of action: catecholamines
Activation of second-messenger system to alter activity of target proteins that produce the effect
43
Hormones of this type: catecholamines
only hormones from the adrenal medulla
44
Solubility: thyroid hormone
lipophilic
45
Structure: thyroid hormone
iodinate tyrosine derivative
46
Synthesis: thyroid hormone
in colloid, an inland extracellular site
47
Storage: thyroid hormone
in colloid
48
Secretion: thyroid hormone
endocytosis of colloid
49
Transport in blood: thyroid hormone
mostly bound to plasma proteins
50
Receptor site: thyroid hormone
inside target cell
51
Mechanism of action: thyroid hormone
activation of specific genes to make new proteins that produce the effect
52
Hormones of this type: thyroid hormone
only hormones from the thyroid follicular cells
53
Hormones can influence the activity of another hormone at a given target cell in 3 ways...
1. permissiveness
2. synergism
3. antagonism
54
Permissiveness
- one hormone must be present in adequate amounts for the full exertion of another hormone's effect
- one hormone enhances the responsiveness of another hormone to the target gland
- e.g. thyroid hormone increases receptor for epinephrine's target cells (cardiac muscle cells)
55
Synergism
- the actions of more than one hormone are complementary and their combined effect is greater than the sum of their separate effects
- e.g. synergistic effects of FSH and testosterone on testes are required to maintain sperm production
56
Antagonism
- one hormone causes the loss of another hormone's receptor, reducing the effectiveness of the second hormone
- e.g. progesterone inhibits the action of estrogen (reducing the receptors) on uterine muscles to prevent miscarriage during pregnancy
57
How cortisol is produced and its functions
Stress and diurnal rhythm (light and dark cycle) --> hypothalamus --> CRH (corticotropin-releasing hormone) --> anterior pituitary --> ACTH (adrenocorticotropic hormone) --> adrenal cortex --> cortisol --> 1. increases blood glucose by gluconeogenesis, 2. increases amino acid, 3. blood fatty acids
58
Hormones released by anterior pituitary
ACTH, TSH, GH, PRL, LH and FSH
59
Hormones released by posterior pituitary
Vasopressin/ADH, Oxytocin
60
Target cells of ACTH
zona fasciculata and zona reticularis of adrenal cortex
61
Major functions of ACTH
stimulates cortisol secretion
62
Target cells of TSH
thyroid follicular cells
63
Major functions of TSH
stimulate T3 and T4 secretion
64
Target cell of GH
bone, soft tissues
65
Major functions of GH
essential but not solely responsible for growth, stimulates growth of bones and soft tissues, metabolic effects include protein anabolism, fat mobilization and glucose conservation
66
Target cell of FSH
females: ovarian follicles
males: seminiferous tubules in testes
67
Major functions of FSH
females: promotes follicular growth and development, stimulates estrogen secretion
males: stimulates sperm production
68
Target cell of LH
females: ovarian follicle and corpus luteum
males: interstitial cells of Leydig in testes
69
Major functions of LH
females: stimulates ovulation, corpus luteum development and estrogen and progesterone secretion
males: stimulates testosterone secretion
70
Target cell of PRL (prolactin)
mammary glands
71
Major functions of PRL (prolactin)
promotes breast development, stimulates milk secretion
72
Target cell of Oxytocin
uterus and mammary glands (breasts)
73
Major functions of oxytocin
uterus= increases contractility
mammary glands (breasts)= causes milk ejection
74
Target cell of vasopressin
kidney tubules and arterioles
75
Major functions of vasopressin
kidney tubules= increases water reabsorption
arterioles= produces vasoconstriction
76
hypothalamus controls the release of __ ___, the secretion of each is stimulated or inhibited by more than seven ___ ___
hypothalamus controls the release of pituitary hormones, the secretion of each is stimulated or inhibited by more than seven hypophysiotropic hormones
77
Major hypophysiotropic hormones
thyrotropin-releasing hormone (TRH), corticotropin-releasing hormone (CRH), gonadotropin-releasing hormone (GnRH), growth hormone-releasing hormone (GHRH), growth hormone inhibiting hormone (GHIH), prolactin-releasing hormone (PRH) and prolactin-inhibiting hormone (PIH)
78
Thyrotropin-releasing hormone (TRH)
stimulates release of TSH and prolactin
79
Corticotropin-releasing hormone (CRH)
stimulates release of ACTH
80
Gonadotropin-releasing hormone (GnRH)
stimulates release of FSH and LH
81
Growth hormone-releasing hormone (GHRH)
stimulates release of growth hormone
82
Growth hormone-inhibiting hormone (GHIH)
inhibits release of growth hormone
83
Prolactin-releasing hormone
stimulates release of prolactin
84
prolactin-inhibiting hormone
inhibits release of prolactin
85
Long-loop feedback
Hormones from peripheral endocrine glands inhibit the release of hypothalamic and pituitary hormones
86
Short-loop feedback
Pituitary hormones inhibit the release of hypothalamic hormones
87
Which of the following statements correctly describes endocrine glands?
a. they produce hormones into the ducts
b. they act locally on nearby tissues
c. they can all pass through the plasma membrane
d. they are all controlled by the nervous system
B
88
Which of the following statements correctly describes hormones?
a. they are all of similar chemical composition
b. they combine with specific receptors on the target cell's surface or inside the target cell
c. they are secreted at a constant rate
d. they all act by activating adenylate cyclase, which transforms ATP into cyclic AMP
B
89
Which of these statements does NOT apply to peptide hormones?
a. they include adrenal cortex hormones
b. insulin is an example of this type of hormone
c. they are stored within secretory granules
d. they are secreted from endocrine glands
A
90
Which of the following statements correctly describes tropic hormones?
a. they are produced by the posterior pituitary
b. they are secreted only by the hypothalamus
c. they primarily regulate hormone secretion by certain other endocrine glands
d. they all have non-tropic functions too
C
90
Which class of hormones is synthesized by the endoplasmic reticulum- Golgi complex mechanism?
a. peptides
b. catecholamines
c. steroids
d. thyroid hormones
A
90
Which of these hormones is NOT a tropic hormone?
a. ACTH
b. ADH
c. ICSH
d. LH
B
* ICSH= LH (Interstitial cell-stimulating
hormone) because it targets the interstitial cells of Leydig in testes
91
Which class of hormones is released by exocytosis upon appropriate stimulation?
a. peptides
b. thyroxins
c. steroids
d. insulins
A
92
The transport of lipid-soluble hormones in the blood is accomplished by which of the following mechanisms?
a. loose binding with iodine
b. specific binding to some plasma proteins
c. binding to HDLs
d. binding to glycolipids
B
93
Which of the following statements is correct with respect to steroids?
a. they are hydrophilic
b. they are derived from cholesterol
c. they initiate synthesis of the second messenger within the target cells
d. epinephrine is an example of a steroid
B
94
Which class of hormones acts by means of a second-messenger system?
a. proteins
b. catecholamines
c. steroids
d. thyroid hormones
B
95
Which of the following substances is the most common second messenger used by hydrophilic hormones?
a. calcium
b. cyclic AMP
c. chromatin
d. messenger RNA
B
96
Estrogens, testosterone, cortisol and aldosterone are derivatives of which molecular precursor?
a. DHEA
b. cholesterol
c. UDP-glucose
d. epinephrine
B
97
Which of the following happens in the second-messenger step?
a. a small amount of one hormone (the second messenger) is required to release another
b. a tropic hormone (the first messenger) stimulates secretion of another hormone (the second messenger)
c. the hormone first binds to a specific surface receptor, whereupon the hormone- receptor complex moves into the cell to combine with a specific intracellular receptor
d. a hormone (the first messenger) binds to surface receptor, activating adenylyl cyclase, which catalyzes cAMP formation
D
98
Which of the following can influence the effective plasma concentration of a hormone?
a. the hormone's rate of binding to receptors on target tissues
b. the hormone's extent of binding to plasma proteins
c. the hormone's rate of metabolic activity
d. the hormone's rate of secretion
D
99
Which of the following statements applies to TSH?
a. a buildup of the thyroid hormone stimulates its production by negative feedback
b. it is secreted by the thyroid gland
c. it is stored in the posterior pituitary
d. it stimulates the thyroid gland
D
100
Which of the following statements correctly describes control of hormone secretion?
a. normally the effective plasma concentration of a hormone is regulated by the rate of its synthesis
b. in order to maintain homeostasis, the rate of hormone secretion remains constant
c. all hormones are regulated with negative feedback controls
d. neuroendocrine reflexes produce a sudden increase in hormone secretion in response to a specific, usually external, stimulus
D
101
Which of the following statements refers to permissiveness of hormones?
a. hormones permit cellular processes to occur
b. hormones permit their target organs to function at the optimal rate
c. In some instances, an adequate amount of one hormone must be present for the full exertion of another hormone's effect
d. through numerous neuroendocrine relationships, the nervous system allows the endocrine system to function
C
102
Which of these hormones is a neurohormone?
a. vasopressin
b. thyroid hormone
c. growth hormone
d. cortisol
A
103
Which of the following hormones is released from the hypothalamus?
a. CRH
b. TSH
c. FS
d. LH
CRH
104
Which of the following statements correctly describes the anterior pituitary?
a. it is also known as the neurohypophysis
b. it is composed primarily of nervous tissue
c. it primarily secretes tropic hormones
d. it secretes vasopressin
C
105
Which of the following statements correctly describes hypophysiotropic hormones?
a. each hypophysiotropic hormone influences only one anterior pituitary hormone
b. all hypophysiotropic hormones stimulate the release of anterior pituitary hormones
c. hypophysiotropic hormones are also produced outside the hypothalamus, where they serve different functions
d. hypophysiotropic hormones are secreted into the general circulation
C
106
Which of these activities happens in a short-loop, negative-feedback, control system?
a. the anterior pituitary hormone feeds back to the hypothalamus, suppressing releasing hormone
b. the target gland's hormone feeds back to the anterior pituitary, suppressing the tropic hormone
c. the target gland's hormone does not feed back to any other gland
d. the anterior pituitary hormone feeds back to the posterior pituitary gland, stimulating the inhibiting hormone
A
107
Which of these statements represents long-loop, negative feedback in the CRH-ACTH-cortisol system?
a. cortisol inhibits CRH secretion
b. CRH inhibits ACTH secretion
c. ACTH inhibits CRH
d. ACTH inhibits cortisol secretion
A
108
T/F
The same chemical messenger may be either a hormone or a neurotransmitter depending on its source and mode of delivery to the target tissue
True
109
T/F
A single endocrine gland may produce many hormones
True
110
T/F
Neurohormones are hormones that specifically modify neural activity
False
111
T/F
specialization of target-cell receptors explains the specificity of hormonal action
True
112
T/F
the nervous system exerts considerable control over the endocrine system, but hormones have no influence over the nervous system
False
113
T/F
peptide hormones are often produced as prohormones
True
114
T/F
the hormones influence adjustments that require duration rather than speed, whereas the rapid coordinations of the body are controlled by the nervous sytem
True
115
T/F
All hormones are first formed as preprohormones then are pruned into active hormones
False
116
T/F
One target cell receptor may bind with more than one type of hormone
True
117
T/F
Cholesterol is a common precursor for polypeptide hormones
False
118
T/F
Endocrine responses occur more slowly and last longer than neural responses
True
119
T/F
Peptide hormones cause changes in solute permeability or alter intracellular protein activity at their targets
True
120
T/F
All hormones are synthesized by the ER-Golgi complex system
False
121
T/F
Negative-feedback control tends to maintain hormone levels at a relatively constant set point, whereas neuroendocrine reflexes usually produce a sudden increase in hormone secretion in response to a specific stimulus
True
122
T/F
Permissiveness refers to the conversion of inactive enzymes into active enzymes by hormones, thus permitting the enzymes to perform their function
False
123
T/F
An anterior pituitary gland produces inhibiting and stimulating signals that affect the hypothalamus
False
124
T/F
The posterior pituitary secretes LH
False
125
The ____ hormones are derived from tyrosine
catecholamines
126
Steroid hormones are derived from ____
cholesterol
127
___ are long-range chemical mediators secreted by endocrine glands into the blood, which carries them to distant target organs
Hormone
128
The specific site upon which a hormone exerts its effect is referred to as a ___ cell
target
129
Antidiuretic hormone is also called ___
ADH/Vasopressin
130
With ___, one hormone must be present in adequate amounts for the full exertion of another hormone's effect
Permissiveness
131
___ from the anterior pituitary stimulates cortisol secretion
ACTH
132
This releasing hormone, called ___ ultimately causes secretion of adrenocorticosteroids
CRH
133
FSH and LH are collectively called ___ because they control secretion of sex hormones
gonadotropins
134
The posterior pituitary secretes ___ and ___
oxytocin and vasopressin
135
The primary means of eliminating hormones and their metabolites from the blood is ____
excretion in the urine
