Set 3 (Part I) Flashcards
1
Q
What are electrical signals?
A
- Involve changes in membrane potential
- Mostly seen in nervous system
2
Q
What are chemical signals?
A
- Molecules secreted by cells into EF
- Responsible for most communication within the body
- Mostly seen in endocrine system
3
Q
What are the four basic methods of cell-to-cell communication?
A
- Gap junctions
- Contact-dependent signals
- Chemicals that diffuse through EF
- Long-distance communication
4
Q
What do gap junctions allow?
A
Direct cytoplasmic transfer of electrical and chemical signals between adjacent cells
5
Q
When do contact-dependent signals occur?
A
When surface molecules on one cell membrane bind to surface molecules on another
6
Q
What do chemicals that diffuse through EF act on?
A
Cells that are close by
7
Q
What does long-distance communication use?
A
- Uses a combination of chemical signals transported by the blood
- Relies on the presence or absence of a receptor
8
Q
What is the simplest form of cell-to-cell communication?
A
Gap junctions
- Direct transfer of electrical and chemical signals by creating cytoplasmic bridges
9
Q
What forms a union of membrane-spanning proteins? What are they called?
A
- Gap junctions
- Connexins
10
Q
When open ions, amino acids, ATP, cAMP diffuse directly from one cytoplasm of one cell to the cytoplasm of the next, this is called _________.
A
gap junction
11
Q
What can’t pass through gap junctions?
A
Larger molecules
12
Q
What is the only means by which electrical signals can pass directly?
A
Gap junctions
13
Q
What does contact-dependent signaling require?
A
Requires that surface molecules on one cell membrane bind to a membrane protein of another
14
Q
Where do contact-dependent signals occur?
A
Occurs in the immune system and during growth/development
15
Q
Which cell-to-cell communication includes cell-adhesion molecules?
A
Contact-dependent signaling
16
Q
In what direction do CAMs and integrins transfer signals?
A
In both directions
17
Q
What are paracrine and autocrine signals?
A
Chemical signals
18
Q
Define autocrine signals.
A
- Chemical signal
- Act on the same cell that secreted them
19
Q
Define paracrine signals.
A
- Chemical signal
- Secreted by one cell and diffuse to adjacent cells
20
Q
What is responsible for long-distance communication?
A
- Hormones secreted by endocrine glands or cells into the blood
- Target cells with receptors
21
Q
What are neurotransmitters?
A
Chemicals secreted by neurons that diffuse across a small gap to the target cell
22
Q
What two types of signaling do neurons use
A
- Electrical (action potential)
- Chemical (neurotransmitter)
23
Q
What are neurohormones?
A
Chemicals released by neurons into the blood for action at distant targets
24
Q
What kind of signals may cytokines carry-out?
A
- Local
- Long-distance
25
What are cytokines synthesized by? What aren't they synthesized by?
- Synthesized and secreted by all nucleated cells
| - Not produced by specialized cells
26
What do cytokines control?
- Cell development
- Differentiation
- Immune responses
27
How do cytokines differ from hormones?
- Cytokines act on a broader spectrum of target cells than hormones
- Cytokines are made on demand (not stored)
28
Explain the four steps of signal pathways utilized by paracrine/autocrine molecules and hormones.
1. Signal molecule binds to receptor protein
2. Receptor protein activates intracellular signal molecules
3. Intracellular signal molecules alter target proteins
4. Target proteins create a response
29
Where are receptor proteins located?
- Inside the cell
| - On the cell membrane
30
What is the location of ligand/receptor binding dependent on?
Whether a signal molecule is lipophilic or hydrophilic
31
Where can lipophilic signal molecules diffuse?
- Through the phospholipid bilayer
| - Binding to cytoplasmic or nuclear receptors
32
Where do lipophobic signal molecules bind?
- Cannot diffuse through plasma membrane
| - Bind to extracellular receptors (on membrane)
33
Differentiate the outcomes of lipophilic and lipophobic signal molecules.
- Lipophilic: receptor activation often turns on or off a gene; relatively slow
- Lipophobic: causes a cascade of events to occur; very rapid
34
Where can lipophilic molecules bind?
- To the membrane
| - Intracellular receptors
35
What three consequences may secondary messengers cause?
1. Alter gating of ion channels
2. Increase intracellular calcium (which bind to proteins to change their function)
3. Change enzyme activity, especially of protein kinases and protein phosphatases
36
Explain the mechanism of the insulin receptor involving a tyrosine kinase.
1. Insulin binds to receptor on the surface.
2. Activation of tyrosine kinase on the cytoplasmic side
3. TK transfers a phosphate group from ATP to a tyrosine of a protein
37
What do most signal transductions use?
G proteins
38
What are G proteins?
- Bind nucleotide guanosine
| - Large and complex family of membrane-spanning proteins that cross the bilayer 7 times
39
What happens when G proteins are activated?
- Open ion channels in the membrane
| - Alter enzyme activity on the cytoplasmic side of the membrane
40
Explain the mechanism of the GPCR Adenylyl-Cyclase-cAMP signal transduction pathway.
1. Ligand binds to G protein receptor
2. G protein turns on adenylyl cyclase
3. Adenylyl cyclase converts ATP to cAMP
4. cAMP activates PKA
5. PKA phosphoryaltes other proteins
41
Explain the mechanism of the GPCR Phospholipase C system.
1. Ligand binds to G protein
2. G protein activates phospholipase C (PL-C)
3. PL-C converts membrane phospholipids into diacylglycerl (membrane) and IP3 (cytoplasm)
4. DAG activates protein kinase C
5. IP3 causes release of Ca2+ from organelles
42
Explain the mechanism of a receptor ion channel.
1. Receptor-channels open or close in response to signal binding
2. Some channels are linked to G proteins
3. Other respond to intracellular second messengers
43
Which signal pathway initiates the most rapid response?
Receptor ion channel
44
How does calcium enter the cell?
- Voltage gated calcium channels
| - Ligand or mechanically gated
45
What is an agonist?
An agonist activates a receptor
46
What is an antagonist?
Blocks receptor activity
47
Which two systems function to achieve and maintain homeostasis?
- Nervous (fast-acting)
| - Endocrine (slow-acting)
48
When the nervous and endocrine systems work together, they are referred to as the ______________.
neuroendocrine sytem
49
What are the differences between the nervous and endocrine systems in terms of anatomy?
- Nervous: each nerve cell terminates on a specific target cell
- Endocrine: endocrine glands are not linked with their target cell (wireless); the messengers are secreted into blood
50
Differentiate the nervous and endocrine systems in terms of what they can affect.
- Nervous: rapid, short-lived
| - Endocrine: slow, long-lasting
51
Differentiate the nervous and endocrine systems in terms of what they stimulate.
- Endocrine: can access most tissues and cells
| - Neurons: only stimulate muscles and glands across a synapse
52
What is neural specificity due to?
- Anatomic proximity between the nerve cell and target tissues
- Which muscle moves depends on which neuron releases acetylcholine as all motor neurons have Ach receptors
53
Differentiate endocrine and exocrine glands.
- Endocrine: secretes hormones in interstitial space and gets picked up by blood
- Exocrine: secretes products that end up outside of the body, passes through a duct
54
Describe the function of the endocrine glands that are made of neurosecretory tissue. Give an example.
- Modified neurons that secrete chemical messengers that diffuse in the bloodstream rather than across a synapse
- Adrenal medulla
55
What is the function of the hypothalamus?
- Master gland
- Receives input and acts accordingly
- Controls the release of anterior pituitary hormones through releasing and inhibiting factors
56
What does the hypothalamus control?
Anterior pituitary
57
What seven products are secreted by the anterior pituitary?
1. TSH
2. ACTH
3. GH
4. FSH
5. LH
6. PRL
7. MSH
58
What is the function of thyroid-stimulating hormone (TSH)?
- Stimulates thyroid cells to produce T4 and T3
- Brain development
- Metabolism
- Reproduction
59
What is the function of adrenocorticotropic hormone (ACTH)?
Stimulates cortisol secretion from adrenal cortex
60
What is the function of growth hormone (GH)?
Growth and metabolic effects
61
What is the function of follicle-stimulating hormone (FSH)?
- Acts on gonads
- Women: growth of follicles
- Males: androgen-binding expression by Sertoli cells (spermatogenesis)
62
What is the function of luteinizing hormone (LH)?
- FSH triggers the production of estrogen
- Rise in estrogen decreases FSH, and increases LH
- LH causes the egg to be released from the ovary (ovulation)
- In males: testosterone production
63
What is the function of prolactin (PRL)?
Milk synthesis from mammary glands
64
What is the function of melanocyte-stimulating hormone?
- Melanocytes give skin its pigment
| - Only active during development and pregnancy
65
What are the two hormones released by the posterior pituitary?
- Vasopressin (antidiuretic hormone)
| - Oxytocin
66
What is oxytocin responsible for?
- Milk let down
| - Uterine contractions
67
What does the pineal gland produce? What is it responsible for?
- Melatonin
| - Controls biological (circadian) rhythm
68
What does the thyroid gland secrete? What are their overall functions?
- T3
- T4
- Calcitonin
- Controls how quickly the body burns energy and makes proteins (metabolism regulator)
69
What is the function of calcitonin?
Secreted if blood calcium is high; makes the system utilize calcium for bone production
70
What does the adrenal cortex secrete?
- Mineralocorticoids
| - Aldosterone, corticosteroids, androgens
71
What is the function of aldosterone? What is it secreted by?
- Acts on the kidney to cause conservation of sodium and overall retention of water
- Adrenal cortex
72
What is the function of corticosteroids? What is it secreted by?
- Increases BP and blood sugar
| - Reduces immune responses (anti-inflammatory)
73
What does the adrenal medulla secrete? What is their function?
- Epinephrine and norepinephrine
| - Stress adaptation
74
What does the pancreas secrete? What is their function?
- Insulin, glucagon, somatostatin
| - Nutrient levels and utilization
75
What do the gonads secrete?
- Testes: testosterone
| - Ovaries: estrogen and progesterone
76
What is T4?
- Thyroxine
| - Tetraiodothyronine
77
What is T3?
Triiodothyronine
78
Explain the onset of goiter.
- Results from iodine deficiency, which is essential in the production of the thyroid hormones
- The thyroid gland panics during deficiency and starts producing more cells (hyperplasia), which results in a big mass on the neck
79
What are the consequences of children with thyroid hormone deficiency?
- Physical growth and development problems
| - Brain development can be severely impaired (cretinism)
80
What is the most common form of hyperthyroidism?
Grave's disease
81
What is Grave's disease?
- An immune system protein mimics thyroid stimulating hormone (autoimmune)
- Immunoglobulins are binding to the thyroid gland, which is perpetually stimulated
- Results in hyperthyroidism, and sometimes in an enlarged tumor
82
What are the signs and symptoms of Grave's disease?
- Sweating
- Headache
- Weight loss
- Nausea and diarrhea
- Irritability
- Muscle weakness
- Sleeping problems
- Fast heartbeat
- Goiter (sometimes)
83
How is Grave's disease treated?
Radioactive iodine to destroy thyroid cells
84
What are hydrophilic hormones? Give examples.
- Water soluble (usually peptide or protein hormones)
| - Insulin, epinephrine
85
What are lipophilic hormones? What do they include?
- High lipid solubility, poorly soluble in water
| - Thyroid hormones and steroids
86
What are steroids?
All steroids are derived from cholesterol
87
What are thyroid hormones made of?
Iodinated tyrosine (AA) derivative
88
What are tropic hormones?
Targets other endocrine glands and stimulate their growth/secretion of other hormones
89
What do sex hormones target?
Reproductive tissues
90
What do anabolic hormones do?
- Stimulate anabolism (to build) in target cells
| - Ex: testosterone stimulates protein synthesis and build up of cellular tissue
91
What do the solubility properties of a hormone 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
92
How are hydrophilic hormones transported in the blood?
Dissolved in the plasma
93
How are lipophilic hormones transported in the blood?
- Bound reversibly to plasma proteins
| - Hormones are released by these proteins when they actively signal target cells
94
How do hormones generally produce their effects?
- Altering intracellular proteins (signal transduction)
- Hydrophilic hormones: receptors on surface
- Lipophilic: hormones pass through cell membranes
95
What are the precursors of hydrophilic peptide hormones?
Preprohormones
96
How are preprohormones made?
- Made on ribosomes in the ER
- Converted to prohormones in the Golgi, and then to active hormones
- Golgi concentrates the hormone into secretory vesicles
- Released by exocytosis
97
What is the precursor to lipophilic hormones?
Cholesterol for steroid hormones (exception is thyroid hormone)
98
How are steroid hormones made from cholesterol?
- Enzymatic steps modify cholesterol into a different hormone
- Only the precursor (cholesterol) is stored
99
How are lipophilic hormones stored?
- They are NOT stored
| - Metabolized by the liver or excreted in urine
100
Which lipophilic hormone is stored?
Thyroid amine hormones
101
How are steroid hormones similar in terms of structure?
They all have a four-ring steroid nucleus at their core
102
How can lipid-soluble hormones initiate gene transcription?
- Bind to nuclear receptor, which usually has a zinc finger DNA binding domain
- Bind at the hormone response elements (HRE)
103
Which steroid hormones are synthesized in the adrenal cortex? Which is synthesized in the ovary?
- Adrenal cortex: aldosterone, cortisol
| - Ovary: estrogen
104
What are non-steroid hormones synthesized from?
- Synthesized from amino acids
| - Protein hormones or glycoprotein hormones
105
Human chorionic hormone-pregnancy recognition (hCG) hormone is an example of what?
Glycoprotein hormone
106
Oxytocin and ADH are examples of what?
Peptide hormones
107
How are amine hormones synthesized? What are they produced by?
- Synthesized by modifying a single molecule of tyrosine
| - Produced by neurosecretory cells and by neurons, or the thyroid gland
108
Epinephrine, norepinephrine, T3 and T4 hormones are examples of what?
Amine hormones (from tyrosine)
109
How do hormones signal a cell?
- Binding to the target cell's specific receptors (lock and key)
- Different hormone-receptor interactions produce different regulatory changes
110
What different regulatory changes can a hormone produce?
- Inactivation of an enzyme
| - Initiation of gene transcription
111
What is synergism?
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
112
FSH and estrogen acting on granulosa cells is an example of what?
Synergism
113
What is permissiveness?
When a small amount of one hormone permits, or enables, a second one to have its full effects on a target cell
114
What is antagonism?
One hormone produces the opposite effects of another hormone
115
Parathyroid hormone and calcitonin are an example of what?
Antagonism
116
Hormone actions must be ________.
terminated
117
How are hormone actions terminated?
Hormones have a half-life and are degraded into inactive metabolites in the liver, which are then excreted
118
What are the effects of extended actions of insulin?
- Deprives the brain of glucose
- Neurons are insulin independent, but muscle and fat are dependent
- The glucose would go to muscle/fat, and the brain would be deprived
119
Describe the mobile-receptor model.
1. Hormone passes in the nucleus, where it binds to a mobile receptor and activates a certain gene sequence
2. Transcription of mRNA, which moves to the cytosol and associates with ribosomes
3. Synthesis of protein molecules that produce the effect of the hormone
120
How do steroid hormones regulate cells? What determines the magnitude of a target cell's response?
- Regulating production of certain critical proteins
| - The amount of steroid hormone present
121
Why are responses to steroid hormones slow?
Because transcription and protein synthesis take time
122
What does target cell sensitivity depend on?
- In part, on the number of receptors that the cell has
| - Receptors are constantly being broken down and replaced
123
Differentiate up-regulation and down-regulation.
- Up-regulation: increased number of hormone receptors; increases sensitivity
- Down-regulation: decreased number of hormone receptors
124
How does the secondary messenger mechanism differ from steroid hormone effects?
1. Effects of the hormone are amplified by the cascade of reactions
2. Second messenger mechanism operates much more quickly than the steroid
125
How do non-steroid hormones usually operate?
Second messenger mechanism, in which the non-steroid hormone acts as the first messenger
126
Describe the mechanism of action of non-steroid hormones.
1. Non-steroid hormone binds to the receptor.
2. Activation of a G, protein
3. Alpha subunit shuttles and activates adenylyl cyclase
4. Adenylyl cyclase converts ATP to cAMP
5. cAMP acts as a secondary messenger and activates PKA, which phosphorylates proteins
127
What are the four categories of membrane receptors?
- Receptor-channel
- Receptor-enzyme
- G protein coupled-receptor
- Integrin receptor
128
What activity do receptor-enzymes have?
- Tyrosine kinase
| - Guanylyl cyclase
129
What is the amplifyer enzyme in GPCR-cAMP?
Adenylyl cyclase
130
What receptor transfers information from the extracellular matrix?
Integrins
131
What do the most rapid signal pathways change? What does that create?
- Change ion flow through channels
| - Creates an electrical signal that alters voltage-sensitive proteins
132
What is the difference between a first messenger and a second messenger?
- First messengers are extracellular
| - Second messengers are intracellular
133
Where is most intracellular calcium stored?
In the endoplasmic reticulum
134
Which gas is known to relax blood vessels?
Nitric oxide (NO)
135
How can one chemical have opposite effects if a different tissue?
Receptors, like other proteins, may come as families of related isoforms
136
What are two methods to down-regulate cell receptors?
- Endocytosis
| - Desensitization
137
How can cells terminate signal pathways?
- Ligand can be degraded by enzymes in the EC
- Transport of ligand into neighboring cells
- Endocytosis of the receptor-ligand complex
138
What are the three ways hormones act on their target cells?
1. Controlling rates of enzymatic reactions
2. Controlling transport of ions of molecules across membranes
3. Controlling gene expression and synthesis of proteins
139
Name the membrane transport process by which glucose moves from the extracellular fluid into cells.
Facilitated diffusion (GLUT transporter)
140
Where are prohormones contained? In what compartment of the cell? When are they released?
- Contained in secretory vesicles
- In the cytoplasm
- Release their contents by calcium-dependent exocytosis
141
Which cellular organelles do cells that secrete steroid hormones possess?
Lots of smooth ER
142
Where are most steroid hormones made?
- Adrenal cortex
| - Gonads
143
Do peptide or steroid hormones have an extended half-life?
Steroid hormones since they are bound to carrier proteins, which protect them
144
The steroid hormone aldosterone has a short half-life for a steroid hormone—only about 20 minutes. What would you predict about the degree to which aldosterone is bound to blood proteins?
The short half-life suggests that aldosterone is not bound to plasma proteins as much as other steroid hormones are.
145
Is it possible for steroid hormones to cause non-genomic effects?
Yes, in recent years, steroid hormones have been discovered to contain membrane receptors linked to signal transduction pathways
146
Which amino acids create hormones?
Tyrosine or tryptophan
147
What is melatonin derived from?
Tryptophan
148
What are the catecholamines?
- Epinephrine
- Norepinephrine
- Dopamine
149
What do catecholamines behave like?
Neurohormones that behave like peptide hormones
150
What is the sensor in the simplest endocrine reflexes?
- The endocrine cell (directly sense a stimulus, and respond by secreting its hormone)
- Response usually serves as a negative feedback
151
Which two endocrine structures are incorporated into the anatomy of the brain?
- Pineal gland
| - Pituitary gland
152
What are the three major groups of neurohormones? What are they secreted by?
1. Catecholamines (adrenal medulla)
2. Hypothalamic neurohormones (posterior pituitary)
3. Hypothalamic neurohormones that control hormone release from the anterior pituitary
153
Which pituitary gland is a true endocrine gland? Which is an extension of the neural tissue of the brain?
- Anterior pituitary: true endocrine
| - Posterior pituitary: extension of neural tissue
154
Which gland secretes mainly trophic hormones? Which hormone is the exception?
- Anterior pituitary
| - Except prolactin
155
What is the function of the hypothalamic-hypophyseal portal system?
Delivering hypothalamic releasing and inhibiting hormones from the hypothalamus to the anterior pituitary
156
What is the advantage of hormones secreted into a portal system?
A much smaller amount of hormone can be secreted to elicit a given level of response
157
How are feedback loops different in the hypothalamic-pituitary pathway?
- Involve three integrating centers: hypothalamus, anterior pituitary and the endocrine target tissue
- Instead of the response acting as the negative feedback signal, the hormones themselves are the feedback signal
- The downstream hormones usually feed back to suppress the hormone(s) that controlled its secretion
158
Differentiate long-loop feedback and short-loop feedback.
- Long-loop feedback: the last hormone in a pathway feeds back to suppress secretion of its trophic hormones
- Short-loop feedback: pituitary hormones feed back to decrease hormone secretion by the hypothalamus
159
What is functional antagonism?
Two hormones having opposing physiological actions
