Slide set 3- Endocrine system Flashcards
(94 cards)
1
Q
What is the difference between electrical and chemical signal?
A
Electrical: involve change in membrane potential (typical nervous system)
Chemical: are molecules secreted into extracellular fluid, responsible for most communication within the body (typical in endocrine)
2
Q
Describe the 4 basic methods for cell-to-cell communication.
A
- GAP JUNCTIONS: allows direct cytoplasmic transfer of electrical and chemical signals between adjacent cells
- CONTACT-DEPENDENT SIGNAL: occurs when surface molecules of one cell bind to surface molecules of other cell
- CHEMICALS THAT DIFFUSE: through the extracellular fluid to act on cell close by
- LONG-DISTANCE COMMUNICATION: uses a combination of chemical signals transported by the blood
3
Q
What are the characteristics of gap junctions? (5)
A
- Simplest form of cell-to-cell communication
- Direct transfer of electrical and chemical signals
- Creates cytoplasmic bridges between adjacent cells
- Forms from the union of membrane-spanning proteins called CONNEXINS
- The ONLY means by which electrical signals can pass directly from cell to cell
4
Q
What are characteristics of contact dependant signals? (3)
A
- Requires that surface molecules on one cell membrane bind to a membrane protein of another
- Occurs in immune system and during growth and development
- Includes CELL-ADHESION MOLECULES (CAMs)
5
Q
What is the difference between paracrine and autocrine signals?
A
PARACRINE signals: secreted by one cell and diffuse to ADJACENT cells
AUTOCRINE signals: act on the SAME CELL that secreted them
6
Q
What are characteristics of long-distance communication?
A
- Hormones are secreted by endocrine glands or cells into the blood. Only target cells with receptors for the hormone will respond to the signal.
- Use also of NEUROTRANSMITTERS
7
Q
What are neurotransmitters?
A
- Neurotransmitters are chemicals secreted by neurons that diffuse across a small gap to the target cell. Neurons use ELECTRICAL SIGNAL as well.
- Neurotransmitters have a RAPID EFFECT
8
Q
What are neurohormones?
A
- Chemicals released by neurons into the blood for action at distant targets.
- Hormones produced by brain structures that act at distant targets
9
Q
What are cytokines?
A
- Are synthesized and secreted by all nucleated cells (not produced by specialized cells)
- May act as both local and long-distance signals => act on on a BROADER SPECTRUM ot target cells than hormones
- Control CELL DEVELOPMENT, DIFFERENTIATION, and IMMUNE RESPONSES
- Made on demand (are not stored)
- ex: cytokines are especially used in tissue healing. Cytokines will be released to attract the right cells to the area in order to repair it.
10
Q
What are the 4 features shared by all signal pathways? (4)
A
- The signal molecule (ligand, can be cytokine, hormone, para or autocrine signal) brings info to the target cell.
- Ligand-receptor binding activates the receptor
- The receptor activates one or more intracellular signal molecules
- The last signal molecule initiates SYNTHESIS of target PROTS or MODIFIES existing proteins to CREATE A RESPONSE
11
Q
True or false
Receptor prots are only located on the cell membrane
A
FALSE
Receptor prots are located inside the cell or on the cell membrane.
12
Q
On what does the location of ligand/receptor binding depend?
A
On whether the signal molecule is lipophilic or hydrophilic
13
Q
Where will a LIPOPHILIC signal molecule bind, and what will happen?
A
Since it is lipophilic, it can diffuse through the phospholipid bilayer, and bind to CYTOPLASMIC or NUCLEAR RECEPTORS.
- This kind of receptor activation often turns on or off a gene
- RELATIVELY SLOW
14
Q
Where will a LIPOPHOBIC signal molecule bind, and what will happen?
A
- Lipophobic signal molecules cannot diffuse through plasma membrane
- Will bind to EXTRACELLULAR receptors (on plasma membrane)
- Causes cascade of event to occur
- VERY RAPID
15
Q
If the response of a chemical signal is related to change in gene activity, it will than be ______ (slower, faster)
A
Slower.
16
Q
True or false, some lipophobic signal molecules also bind to cell membrane receptors in addition to intracellular receptors.
A
TRUE
17
Q
Which ligand/receptor binding will create a faster response ? (membrane receptor binding or cytoplasmic/nuclear receptor binding)
A
Membrane receptor binding will create a faster response.
18
Q
What is a biological signal transduction?
A
Converts CEHMICAL SIGNAL into CELLULAR RESPONSES
19
Q
What can a second messenger do? (3)
A
- Alter the gating of ion channels
- INCREASE intracellular CALCIUM ( which bind to prots to change their function)
- Change ENZYME ACTIVITY, especially prot KINASES and PROTEIN PHOSPHATASES
20
Q
Go see signal pathway of tyrosine kinase (slide 20)
A
go
21
Q
What are characteristics of GPCR?
A
- GPCR are large complex family of membrane-spanning prots that CROSS the phospholipid bilayer 7 TIMES
- Cytoplasmic tail linked to G protein, a three-part transducer molecule
22
Q
What happens when a G protein is activated?
A
When they are activated, G prots can:
- Open ion channels in the membrane
- Alter enzyme activity on the cytoplasmic side of the membrane
23
Q
What are the steps in GPCR signaling? (5)
A
- Signal molecule binds to G prot-linked receptor, which activates G prot
- G protein turns on adenylyl cyclase, an amplifier enzyme
- Adenylyl cyclase converts ATP to cyclic AMP
- cAMP activates protein kinase A
- Protein kinase A phosphorylates other proteins, leading ultimately to cellular response
24
Q
Go check phospholipase C and Receptor channel on slide 23-24
A
Go
25
What is the difference between agonist and antagonist ligand/receptor binding?
- Agonist will also activate the receptor on which a reference ligand can bind
- Antagonist will block receptor activity
26
What are some differences between nervous and endocrine system?
NERVOUS SYSTEM:
- Each nerve cell terminates on a specific target cell -> wired specific transmission to a target
- Neurotransmitters are RAPID and SHORT LIVED
- Neurons can ONLY STIMULATE MUSCLES and GLANDS across a synapse
ENDOCRINE SYSTEM:
- Wireless
- Glands are not linked with target cells
- Endocrine chemical messengers are secreted into the blood and delivered to distant target sites => ACCESS MOST TISSUES AND CELLS
- Effect of hormones is SLOWER and LONGER lasting
27
What is the difference in specificity between neural and endocrine communication?
- Specificity of neural communication depends on ANATOMICAL RELATIONSHIP between nerve cell and target cells
- Unlike the endocrine system, specificity is not totally reliant on the MESSAGE and cell having CORRECT RECEPTOR
- Which muscle moves depends on WHICH NEURON RELEASES OF Ach, as all motor neurons have Ach receptors
28
What is the main differences between endocrine and exocrine?
ENDOCRINE:
- "Ductless glands"
- Made of glandular epithelium whose cells MANUFACTURE and SECRETE hormones
- Secrete HORMONES
EXOCRINE:
- Product is excreted OUTSIDE
- Often has a DUCT
- Secrete products
29
True or false,
A few endocrine glands are mande of neurosecretory tissue
TRUE
Modified neurons that secrete CHEMICAL MESSENGER that diffuse into BLOOD STREAM rather than across a synapse
ex: Adrenal gland
30
What gland is the master gland in endocrine system? What is the role of this gland?
Hypothalamus
- Receives input and acts accordingly
- Controls release of anterior pituitary hormones through releasing and inhibiting factors
31
What happens if we don't have any iodine in our diet?
No thyroid hormone. Iodine is a major component of thyroid hormone (thyroxine hormone =>T4).
32
What happens if iodine deficiency ? (childhood, adulthood...)
Child: Children will have PHYSICAL GROWTH and development problems, and brain development can also be severely impaired => CRETINISM
Adult: Thyroid gland can be considerably enlarged=> goitre
33
What is Grave's disease?
- Most common form of hyperthyroidism
- An immune system protein mimics TSH (autoimmune)
- Also treated with radioactive iodine to destroy thyroid cells
34
What are the 2 hormone classifications based on structure?
Whether a hormone is HYDROPHILIC or LIPOPHILIC.
HYDROPHILIC hormones : most are PEPTIDE or PROTS hormone => Insulin, or catecholamines (adrenal hormrones -> epinephrine)
LIPOPHILIC hormones: include THYROID HORMONES AND STEROIDS
- All steroids are derived from cholesterol (CORTISOL and SEX HORMONES)
- Thyroid hormone is an exception as it is an IODINATED TYROSINE (aa) DERIVATE
35
What are the 3 hormone classifications based on function?
TROPIC HORMONES: target other endocrine glands and stimulate their growth abd secretion of other hormones (ACTH targets the adrenal cortex)
SEX HORMONES: target REPRODUCTIVE TISSUES
ANABOLIC HORMONES: stimulates anabolism (to build) in taret cells ( Testosterone stimulates protein synthesis and build up of cellular tissue, especially in muscle)
* Insulin is considered anabolic hormone
36
What do the hormone solubility properties determine?
1. The way the hormone is TRANSPORTED in the blood
2. The mechanism by which the hormone exerts its EFFECT-SIGNALING
3. The means by which the hormone is processed by the endocrine cell
37
How are hydrophilic vs lipophilic hormones transported?
Hydrophilic: dissolved in the plasma
Lipophilic: Bound reversibly to plasma proteins
38
On which receptors do hydrophilic vs lipophilic hormones bind?
Hydrophilic: bind to receptors on the SURFACE of the target cells.
Lipophilic : pass through target cell membrane and bind to RECEPTORS INSIDE the target cell
39
How do you call the hydrophilic peptide hormone precursor, and how is it made and stored?
PREPROHORMONE
- Made on ribosomes of the ER.
- Converted to PROHORMONE in Golgi, and finally activated in Golgi too .
- Golgi concentrates these hormones into SECRETORY VESICLES
- These hormones are released from endocrine cells by EXOCYTOSIS
40
What is the common precursor for all steroid hormones?
Cholesterol
| - All have four ring steroid nucleus at their core
41
True or false
| Steroid hormones can be stored
False
Only cholesterol (precursor) can be stored
42
True or false
| Thyroid hormones can be stored
TRue!
| Stored until secreted
43
What are the 4 first steps of hormone synthesis?
1. Messenger RNA on the ribosomes binds a.a into a peptide chain called a PREPROHORMONE.
2. Enzymes in the ER chop off the signal sequence creating an INACTIVE PROHORMONE.
3. The prohormone passes from ER to Golgi complex
4. Secretory vesicles containing enzymes and prohormone bud off the golgi. The enzymes chip the prohormone into one or more active peptides + additional peptide fragments
44
Name exemples of steroid hormones
```
Cortisol (adrenal)
Aldosterone (adrenal)
Estrogen ( ovary and testis)
Progesterone (ovary-CL)
Testosterone (testis-Leydig cells)
```
45
What is a glycoprotein hormone, and name and exemple
Protein hormone with carbohydrate groups atached to a.a. chain
hCG (human chorionic hormone=> pregnancy recognition)
46
What are characteristics of non-steroid hormones (structure...)
- Are synthesized from a.a
PROTEIN hormones: long, folded chains of a.a. (insulin)
GLYCOPROTEIN hormones: Protein hormones with carbohydrates attached to a.a. chain
PEPTIDE hormones: smaller than protein hormones, short chain of a.a. (Oxytocin, ADH)
A.A. DERIVATES hormones: each is derived from a single a.a. molecule
47
What is a peptide hormone and give exemples
smaller than protein hormones, short chain of a.a.
```
Oxytocin
Antidiuretic hormone (ADH)
```
48
How are amine hormones synthesized? give exemple
Synthesized by modifying a single molecule of tyrosine, produced by neurosecretory cells and by neurons
- Epinephrine and norepinephrine (adrenal medulla)
- a.a. derivates produced by thyroid gland => synthesized by adding iodine to tyrosine
49
What are the general principles of hormone action?
- Hormone signal a cell by binding to specific receptor (lock-and-key mechanism)
- Different hormone-receptor interactions produce different regulatory changes within the target cell through chemical reactions
- INACTIVATION of an ENZYME
- Initiation of GENE TRANSCRIPTION
50
Name the 3 combined hormone actions
- Synergism
- Permissiveness
- Antagonism
51
Describe SYNERGISM of combined action of hormones
Combinations of hormones acting together have a greater effect on a target cell than the sum of the effects that each would have if acting alone
- Ex: FSH and estrogen act on granulosa cells...
52
Describe permissiveness of hormones (context of combined action of hormones )
When a small amount of one hormone permits or enables a second one to have its full effects on a target cell
- ex...
53
Describe antagonism of hormones ( context of combined action of hormones)
One hormone produces the opposite effects of another homrone
- ex: parathyroid hormone (increase blood Ca 2+ ) and calcitonin (thyroid cecrease blood Ca2+)
54
Give an exemple on how it is important that hormones
Exemple of INSULIN
Insulin secretion happens when blood glucose is high following a meal
- As long as insulin is present, glucose is taken up by the cells
- Extend actions of insulin would deprive the brain of glucose (cause brain damage... brain cells are insulin independant => if too much insulin, glucose will be stored in wrong cells (skeletal muscle..) and no more glucose for brain
- Insulin (and other hormones) are regulated by terminating hormones activities
- Hormones have HALF-LIVES and are degraded into inactive metabolites in the liver which are then excreted
55
True or false
| Because transcription and protein synthesis takes time, responses to steroid hormones are often slow
TRUE
56
What is the mobile-receptor model? (steroid hormone action)
Hormone passes into nucleus, where it binds to mobile receptor and activates a certain gene sequence to begin transcription of mRNA. newly formed mRNA molecules move into the cytosol, associate with ribosomes, and begin synthesizing protein molecules that produce the effects of the hormone
57
How do steroid hormone regulate cells?
By regulating production of certain critical proteins
58
True or false
The concentration of steroid hormone present doesn't affect the magnitude of cell's response
FALSE
It does influence magnitude of response
59
On what does sensitivity of target cell depend?
Depends in part on number of receptors that cell has
60
What is up- and down-regulation of a hormone?
up: increased number of hormone receptors increases sensitivity
Down: decreased number of hormone receptors decreases sensitivity
61
What are the mechanisms of hormone actions of hydrophilic-protein and peptide hormones? In what is it different of steroid hormones?
Hydrophilic hormones use the second messenger mechanism :
- A non-steroid hormone molecule acts as a "first-messenger"
- EFFECTS of the hormone are AMPLIFIED by cascade of reactions => due to this cascade, the effects can be disproportionately great when compared to the amount of hormone present
- The second messenger mechanism operates MUCH MORE QUICKLY than the steroid mechanism
62
What receptor and pathway does oxytocin uses?
G prot...
IP3 signaling pathway
GO LEARN IT
63
How are hormones normally regulated?
- Usually by negative feedback => simplest mechanism (used with thyroid hormones => anterior pituitary gland, see slide 61)
- Can also be regulated by another endocrine gland secretion (estrogen from ovary feeds back to Pit to regulate FSH)
64
Aller voir slide 62 et la recopier
Go
65
What are the 2 parts of the anterior pituitary gland?
- Pars anterior
| - Pars intermedia
66
Describe the anterior pituitary gland (physically)
Tissue composed of irregular clumps of SECRETORY CELLS supported by fine CONNECTIVE TISSUE fibers and surrounded by a rich VASCULAR NETWORK
67
What are the 5 functional types of secretory cells in the adenohypophysis (anterior pituitary)? What do they secrete?
1. Somatotrophs=> secrete GH
2. Corticotrophs=> secrete ACTH
3. Thyrotrophs => secrete TSH
4. Lactotrophs=> secrete prolactin
5. Gonadotrophs => Secrete FSH and LH
68
True or false
GH stimulates only glucose metabolism
False
GH also stimulates LIPID metabolism
- Accelerates mobilization of lipids from cells and speeds up lipid catabolism. Thes essentially SHIFTS a cell use of nutrients FROM GLUCOSE to LIPID catabolism
69
What effect on blood sugar does GH have?
Has a HYPERGLYCEMIC effect
70
How does GH promote growth?
GH , produced by SOMATOTROPHS, promotes growth by stimulating the LIVER to produce growth factors which in turn ACCELERATE A.A. TRANSPORT into cells
- Promotes growth of BONE , MUSCLE, and OTHER TISSUES by accelerating a.a. transport into the cells- all process involve PROTEIN ANABOLISM
71
What are the 3 ways of how GH affects metabolism?
- Promotes protein anabolism
- Promotes lipid mobilization and catabolization
- Indirectly INHIBITS GLUCOSE METABOLSIM metabolism by shifting energy use to LIPID CATABOLISM
- Indirectly INCREASE BLOOD GLUCOSE
72
What is the effect of prolaction (PRL) ?
During pregnancy, PRL promotes development of breast, anticipating milk secretion, after baby is born, PRL stimulates the mother's mammary glands to produce milk.
73
What is a tropic hormone?
Hormone that has stimulating effect on OTHER ENDOCRINE GLANDS and tend to stimulate synthesis and secretion of the target hormone
74
What are the 4 principal tropic hormones produced and secreted by the basophils of the PARS ANTERIOR?
1. Thyroid stimulating hormone (TSH)
2. Adrenocorticotropic hormone (ACTH)
3. Follicle-stimulating hormone (FSH)
4. Luteinizing hormone (LH)
75
What is the effect of TSH?
Promotes and maintains GROWHT and DEVELOPMENT OF THYROID, also causes thyroid to SECRETE its hormones T3 and T4 (thyroid regulates metabolism )
76
What is the effect of ACTH?
promotes and maintains normal growth and development of CORTEX of ADRENAL GLAND. Also stimulates adrenal cortex to secrete os of its hormones CORTISOL and ALDOSTERONE
77
What is the effect of FSH?
Acts on ovary where it stimulates primary GRAFFIAN FOLLICLES to grow toward maturity. Also stimulates FOLLICLE cells to SECRETE ESTROGENS
In male, FSH stimulates development of SEMINIFEROUS TUBULES OF TESTES , and maintains SPERMATOGENESIS. Acts on SERTOLI CELLS
78
What is the effect of LH?
In FEMALE, stimulates formation and activity of CORPUS LUTEUM of OVARY. Corpus luteum secretes progesterone and estrogens when stimulated by LH. LH also supports FSH in STIMULATING MATURATION OF FOLLICLES.
In MALE , stimulates INTERSTITIAL CELLS (LEYDIG cells) in TESTES to develop and secrete TESTOSTERONE
79
Why are LH and FSH gonadotropins?
Because they stimulate growth and maintenance of gonads.
80
Aller lire slide 75
Go
81
What substance inhibits GH?
Somatostatin
82
What happens to FSH levels at menopause?
They rise
83
How do hypothalamic regulatory hormones reach the anterior pituitary gland?
By a vascular link
- Capillary to capillary connection => the HYPOTHALMIC-HYPOPHYSEAL PORTAL SYSTEM. Blood in this system carries hypothalamic signals to the anterior pituitary
84
How are neurosecretory cells positioned?
Neurosecretory cells have their bodies directly in the hypothalamus, and their axon terminals in the posterior pituitary
85
How can hormone pathologies occur?
- Hormone excess
- Hormone deficiency
- Abnormal responsiveness of target tissues
86
What is the normal cortisol action?
- Protein breakdown
- Glucose formation
- Lipolysis
- Anti-inflammatory effects
- Depression of immune responses
87
What happens when hypersecretion of cortisol? What can be the causes?
Hypersecretion exaggerate's a hormone effects
Causes: Can be numerous causes... Benign tumours (adenomas), cancerous tumours of endocrine glands , or also disease (cuhsing's disease=> hypersecretion of cortisol)
88
What are the symptoms of excessive secretion of cortisol?
- Breakdown of muscle prots and redistribution of body fat, resulting in spindly arms and legs accompanied by a rounded "moon face", pendulous abdomen, flushed appearance
89
What are the normal actions of thyroid hormones?
- Increase in metabolic rate: stimulates the use of oxygen to produce ATP
- Calorigenic effect: simulates synthesis of additional sodium-potassium ATPase (uses extra ATP)
- Stimulates PROTEIN SYNTHESIS and increase use of glucose and fatty acids for ATP production
- Enhance actions of CATECHOLAMINES
- Accelerate body growth
90
What are the symptoms of thyroid hormone deficiency? What can be the causes?
- Swelling of facial tissues (puffiness), slow heart rate, low body temperature, sensitivity to col, dry hair and skin
Causes: Iodine deficiency, stress, congenital (rare)
91
What is an exemple of abnormal responsiveness of target tissue?
Type 2 diabetes mellitus (loss of tissue sensitivity to insulin) => 90% of diabetes
92
What is the normal insulin action?
- Accelerate facilitated diffusion of glucose into cells
- Speed conversion of glucose into glycogen
- Increase uptake of a.a. and increase protein synthesis
- Speed synthesis of F.A. (lipogenesis)
- Slows glycogenolysis
- Slows gluconeogenesis
93
What is the cause of type 2 diabetes mellitus ? What are the symptoms?
Cause: Obesity
Symptoms: High blood glucose, weight loss, excessive thirst, frequent urination
94
What is the difference between type 2 and type 1 diabetes?
Type 1: no insulin produced
Type 2: insulin has no effect... insensibility to insulin, so sugar is not taken up by cells
