Ch 6 pt 1
What are three ways in which cytokines differ from hormones? Chapter 6, p 177, Cytokines May Act as Both Local and Long Distance Signals, right column, paragraph 3
(1) cytokines are not produced by specialized cells but hormones are, (2) cytokines act on a broader range of targets than hormones do and (3) cytokines and hormones have different signaling pathways
How do cells communicate with each other? (Mechanistic approach) Chapter 6, Cell-To-Cell-Communication, page 166, right column, paragraph 2, lines 2
(Local Communication) 1. Gap junctions - direct cytoplasmic connections between adjacent cells 2. Contact-dependent signals - require interaction between membrane molecules on two cells 3. Autocrine (act on same cell) and Paracrine (serceted by one and act on another) signals - chemicals diffuse through extracellular fluid to act on cells close by (Long-Distance Communication) 4. Uses combination of chem. and elec. signals carried by nerve cells and chem. sig. transported throughout the body (nervous and endocrine systems)
What are the basic steps of any signal pathway? (Mechanistic, Chapter 6, Signal Pathways, pg. 169, left column, fig. 6.2)
1) A signal molecule (ligand) binds to a membrane receptor protein. 2) The binding of the ligand+membrane receptor protein activates the receptor. 3) The receptor then activates the intracellular signal molecules. 4) The last signal molecule creates a cellular response by either modifying existing proteins or initiating the synthesis of new proteins.
What are the three major components of a response loop? (Teleological Approach), Chapter 5, pg. 183, right column, under Long-Distance Pathways Maintain Homeostasis, paragraph 2, lines 1-2
1) Input 2) Integration 3) Output
What are the different kinds of roles that calcium plays as a intracellular messenger? (Calcium is an important intracellular signal, column 2, line 9, page 178)
1. Calcium binds to calmodulin, resulting in altered enzyme or transporter activity or the gating of ion channels. 2. binds to other regulatory proteins and alters movement. 3. Binds to regulatory proteins to trigger exocytosis of secretory vesicles. 4. Binds to ion channels to alter their gated state.
What is the difference between lipophilic signal molecules and lipophobic signal molecules? (Receptor proteins are located inside the cell or on the cell membrane, column 2, line 8, page 169)
1. Lipophilic signal molecules are able to enter cells through simple diffusion. They bind to cytosolic receptors or nuclear receptors. Activation of these receptors turns on a gene, which leads to the production of new mRNA strands. The mRNA strand is then translated into a new protein. This response is relatively slow. 2. Lipophobic signal molecules use simple diffusion to enter cells freely. They bind to receptor proteins on the cell membrane. They produce very rapid responses.
What are Cannon's Postulates? (Teleological) Chapter 6 Communication, Integration, and Homeostasis, Cannon's Postulates Describe Regulated Variables and Control Systems, page 183, left column, numbering
1. The nervous system has a role in preserving the "fitness" of the internal environment 2. Some systems of the body are under tonic control 3. Some systems of the body are under antagonistic control 4. One chemical signal can have different effects in different tissues
Cells do not respond to every chemical signal that reaches them. What is the process by which a cell decides if they want to respond and how they respond? (Ch 6, pg 178, paragraphs 2,4)
A cell can only respond to a chemical signal only if the cell has the receptor protein for that signal. If it has a receptor, generally, 1. the signal ligand (1st messenger) binds to a membrane protein receptor. 2. the ligand-receptor binding activates the receptor, and 3. it in turn activates signal molecules intracellularly. 4. the pathway initiates the making or modification of target proteins to create a response.
Why do some cells respond to a chemical signal while others do not? (Teleological)
A cell can only respond to a particular chemical signal if the cell has the appropriate receptor protein to bind that signal. When the ligand binds to the protein receptor, the receptor is activated, which the turns on more intracellular signal molecules, and ultimately a response is created through the modification of existing proteins, or synthesis of new proteins. p.169 Left column.
How can a signaling pathway be modulated with the use of antidepressant drugs? (Mechanistic Approach) Chapter 6, Cells Must Be Able to Terminate Signal Pathways, page 182, left column, paragraph 2, lines 1-9
A class of antidepressant drugs (e.g. selective serotonin reuptake inhibitors-SSRIs) can extend the active life of a neurotransmitter (e.g. serotonin) by slowing its removal from the extracellular fluid. Through this mechanism, antidepressant drugs interfere with normal physiological processes of neurotransmitter removal/degradation.
What is the difference between an agonist and antagonist? (Mechanistic approach) Chapter 6, Agonists and antagonists, page 180, right column, first paragraph, 5-8th line
A competing ligand that binds and elicits a response is known as an agonist of the primary ligand. Competing ligands that bind and block receptor activity are called antagonists of the primary ligand
What is a neuroendocrine pathway? (Pg. 188, paragraph 5, sentence 2).
A hybrid of the neural and endocrine reflexes. In a neuroendocrine pathway, a neuron creates an electrical signal, but the chemical released by the neuron is a neurohormone that goes into the blood for general distribution.
Why are signals amplified in communication? (Teleological approach), Ch 6, Signal Pathways, page 171, right column, 7th paragraph, lines 4-6
A ligand combines with its receptor, this turns on an amplifier enzyme. The enzyme activates more molecules, which then activate even more molecules. This way on messenger ligand can reach multiple molecules at once.
What is the difference between neurotransmitters, neuromodulators and neurohormones? (Pg. 168, paragraph 6)
A neurotransmitter is a neurocrine molecule that has a rapid-onset effect. a Neuromodulaotr acts more slowly as an autocrine or paracrine signal. And a neurohormone diffuses into the blood for body-wide distribution.
What is the difference between a paracrine signal and an autocrine signal? Chapter 6, Local communication uses paracrine and autocrine signals, page 168, left column, first paragraph, 2-7th line
A paracrine signal is a chemical that acts on cells in the immediate vicinity of the cell that secreted the signal. A chemical signal that acts on the cell that secreted it is called an autocrine signal. In some cases, a molecule may act as both an autocrine and a paracrine signal
How do cells respond to chemical signals? (Mechanistic) Chapter 6 Communication, Integration, and Homeostasis, Signal Pathways, page 169, left column, third paragraph and numbering
A response is initiated if the signal molecule binds to the receptor protein. The signal molecule binds to membrane receptor proteins. That activates intracellular signal molecules which alter target proteins to create a response.
When does signaling cascade start?
A signaling cascade starts when a stimulus converts inactive molecule A to an active form. Active A then converts inactive molecule B into active B active molecule B in turn converts inactive molecule C into active C, and so on, until at the final step a substrate in converted into a product. Pg. 171, Section: Membrane Proteins Facilitate Signal Transduction, column 2, lines: 35-38.
Why is a chemical able to cause different responses in different tissues even though it binds to the same ligand? (Teleological Approach, Ch. 6, Pg. 180, Right Column, Paragraph 5, lines 1-7)
A single chemical is able to trigger different responses in different cells because ligand simple activates a signal cascade inside the cell which can vary. The ligand doesn't matter often in terms of the target response.
How is a threshold related to a sensor? (Mechanistic approach) Page 185, Paragraph 8
A threshold is the minimum stimulus needed to set the reflex response in motion. If a stimulus is below the threshold, no response loop is intimated.
How do cells adjust to responses? (Mechanistic approach) Chapter 6, Up- and Down-Regulation Enable Cells to Modulate Responses, page 181, right column, paragraphs 3-6, lines 3.2-4.2, 6.1-6.2
Abnormal high concentrations for sustained period of time: Down-regulation decreases receptor number by having he cell physically removes receptors from the membrane through endocytosis. Desensitization can also occur in which a chemical modulator is bound to the receptor protein. Abnormal low concentrations of ligand: Up-regulation increases the number of receptors by the target cell inserting more receptors into its membrane.
How is a reflex response set into motion? (Mechanistic approach), Ch 6, Homeostatic Reflex Pathways, page 185, right column, 5th paragraph, line 1-3
All sensors have a threshold which is a minimum stimulus that needs to be breached before a response can be initiated.
How is an external stimulus converted into a physiological response? (Mechanistic Approach) Chapter 6, Long-Distance Pathways Maintain Homeostasis, page 185, left column, paragraph 1-2, lines 1-18
An external stimulus is sensed by a sensor/sensor receptor (continually monitors its environment for a change in a regulated variable) which then sends an input signal to the integrating center. The integrating center compares the input signal with the desired value of that variable (set point) and sends an output signal to a target/effector to stimulate a response.
How is arachidonic acid involved in asthma and inflammation? (Mechanistic) pg 189, paragraph 4, figure 6.12
Arachidonic acid can be converted leukotrienes, which is involved in asthma, as well as prostaglandins and thromboxanes, which are involved in inflammation.
Why is the principle of competing agonists important for the design of drugs that are longer-acting and more resistant to degradation? Telelogical Approach, Page 204, Right column, Agonists and Antagonists, Paragraph 2, Lines 1-4
B/c agonists will also activate the same receptors as the endogenous ligand but can be designed to last longer in the body than the endogenous ligand.
Why is the range of paracrine signals restricted to adjacent cells? (Teleological, Chapter 6 Communication, Integration, and Homeostasis, Signal Pathways, page 168, left column, paragraph 2, lines 2-3)
Because distance is a limiting factor for diffusion
Why are gap junctions considered the simplest form of cell-to-cell communication? Chapter 6, Gap Junctions Create Cytoplasmic Bridges, 1st paragraph, lines 1-9
Because it's a direct transfer of electrical and chemical signals through protein channels that create cytoplasmic bridges between adjacent cells. Other forms of junctions are more complex.
Why do certain cells respond to a chemical signal while others ignore it? Chapter 6, Signal Pathways, paragraphs 2-3, lines 1-16
Because not all cells have the appropriate protein receptors that can receive and respond to the signal.
Why is receptor-ligand binding affected by the fact that receptors are proteins? (Teleological approach) Chapter 6, Receptors Exhibit Saturation, Specificity, and Competition, page 180, right column, paragraph 1, line 1
Because receptors are proteins, receptor-ligand binding exhibits the general protein-binding characteristics of all proteins - including specificity, competition, and saturation. Multiple ligands with similar structures can bind to the same receptor, creating competition for the receptor.
How do receptor-channels initiate the most rapid intracellular responses of all receptors? (Mechanistic). Chapter 6, Signal Pathways, page 172, right column, paragraph 1, 3rd-8th lines
Binding of extracellular ligands opens or closes the channel gate, altering the cell's permeability to an ion. Changing ion concentration changes the membrane potential of the cell, creating an electrical signal that affects voltage-sensitive proteins.
How are agonist and antagonist related in function to each other? Chapter 6, Agonist and Antagonists, 1st paragraph, lines 1-8
Both of these things compete with the actual ligand by binding to the receptor. Agonist elicits an actual response, while antagonists' sole purpose is to block the response of the primary ligand.
How do lipophilic signal molecules enter cells? (Mechanistic, Chapter 6 Communication, Integration, and Homeostasis, Signal Pathways, page 169, right column, third paragraph, lines 1-2)
By simple diffusion through the phospholipid bilayer of the cell membrane
How do scientists visualize Ca2+ signals in cells? Mechanistic approach, Page 203, Bottom Biotechnology Box, Calcium Signals glow in the dark
By using chemicals that releases light that can be measured by electronic detection systems. Some examples include aequorin, fura, Oregon green, BAPTA
What is name of the receptor in cell-to-cell signaling?
Cell adhesion molecules (CAMs) act as receptors in cell-to cell signaling. They are linked to the cytoskeleton or to intracellular enzymes, and through these linkages, CAMs transfer signals in both directions across cell membranes. Pg. 168, Section: Contact-Dependent Signals Require Cell-to-Cell Contact, column 1, lines: 4-8
How can cells bring their response back to normal? (Mechanistic approach), Ch 6, Modulation of Signal Pathways, page 181, right column, 3rd and 4th paragraph, line 5-6 & 1-5
Cells can either do down-regulation or desensitization of the receptors for the signal. Down-regulation decreases the number of receptors by removing them from the membrane.
How does down-regulation occur to cause a decrease in receptor number? (mechanistic) Chapter 6, page 181, Up- and Down-Regulation Enable Cells to Modulate Responses, right column, paragraph 4, lines 1-7
Cells can physically remove the receptors from their membranes via endocytosis. Another way is to decrease cell response through desensitization by binding a chemical modulator to the receptor protein.
Why do only certain signals illicit responses from specific cells and not others? (Teleological approach) Chapter 6, Signal Pathways, page 169, left column, paragraph 2, lines 2-3
Cells have specific receptor proteins that only react to certain signals. A cell only responds to a signal if it has the correct receptor protein to bind to that receptor. If target cell has receptor, binding of signal molecule initiates a response.
How do the two types of sensory receptors involved in neural reflexes in the body differ? (Mechanistic Approach), pg. 185, under Sensors, right column, paragraph 3, lines 1-6
Central receptors are located in the brain or are closely linked to the brain. Peripheral receptors are elsewhere in the body and include skin receptors and internal receptors.
What is the function of chemical signals? (Mechanistic approach) Chapter 6, Cell-to-cell communication, page 166, right column, second paragraph, 4-8th line
Chemical signals are responsible for most communication within the body. Chemical signals act as ligands that bind to proteins to initiate a response. Protein binding of chemical signals obeys the general rules for protein interactions
Why are competing agonists used by pharmacologists? (Teleological) pg 190, paragraph 6, lines 1-3, 6-8
Companies can design drugs that bind to the same receptors as the naturally occurring molecules, but are protected from degradation.
Why are cytokines different from hormones? Telological Approach, Page 192, right column, Cytokines may act as both local and long-distance signals, Paragraph 3, Lines 1-9
Cytokines = produced and secreted by any nucleated cell VS hormones = produced by specialized epithelial cells. Cytokines = made on demand. VS hormones = made in advance and stored in endocrine cell until secreted. Signal pathways for cytokines usually different from hormones ** But the distinction is often blurry
What are some ways cytokines differ from classic hormones? (Mechanistic) Chapter 6, page 168, Cytokines May Act as Both Local and Long-Distance Signals, right column, 3rd paragraph, lines 4-7
Cytokines are not produced by specialized epithelial cells the way hormones are. Cytokines are made on demand while protein or peptide hormones are made in advance and stored in endocrine cells until needed. The signal pathways for cytokines are usually different from those for hormones.
How can multiple ligands bind to one recpetor? Give an example (Modulation of signal pathways, column 1, line 11)
Different ligand molecules with similar structures may be able to bind to the same receptor. Epinephrine and Norepinephrine use Adrenergic receptors. Adrenergic receptors only bind to the above and not other molecules, demonstrating their specificity
How does signal amplification work? (Membrane proteins facilitate signal transduction, column 2, line 41, page 171)
During signal amplification, one signal molecule is turned into multiple second messenger molecules. It all starts when the first messenger binds to its receptor. This turns on an amplifier enzyme, which activates several molecules, which then activate several other molecules as the cascade continues. Amplification allows a small amount of ligand to create a giant effect.
What is the common point of the different types of signal transduction? How does this effect the cell? (mech) 177, Fig 6.10
Each method of signal transduction leads to altered proteins. When these proteins are altered, they cause a cellular response, which can effect motor proteins, enzyme activity, membrane receptors and transporters, and gene activity and protein synthesis.
How do the specificities of the neural reflex and endocrine reflex differ? (Mechanistic) Chapter 6, page 188, Table 6.2
Each neuron terminates on only a single target cell in a neural reflex, but most cells of the body are exposed to a hormone in an endocrine reflex
Compare and contrast eicosanoids and sphingolipids. (mech) 180, left, paragraph 3, lines 1-5
Eicosanoid and sphingolipids are both lipid signal molecules that combine with G protein coupled receptors in the membranes of the target cells. Eicosanoids are are derived from arachidonic acid which is a 20-carbon fatty acid. Sphingolipids are composed of sphingosine and help regulate inflammation, cell adhesion and migration, and cell growth and death. Eicosanoids are involved in growth, CNS messengers, hormones, and inflammation.
How do electrical and chemical signals differ? (Mechanistic approach) Page 166, Paragraph 3
Electrical signals are changes in a cell's membrane potential and chemical signals are molecules secreted by cells into the extracellular fluid. The cells that respond to electrical or chemical signals are called target cells, or targets for short.
What is the difference between chemical and electrical signals? (Teleological) Chapter 6 Communication, Integration, and Homeostasis, Cell-to-Cell, page 166, left column, second paragraph, lines 6-8
Electrical signals are changes in a cell's membrane potential, while chemical signals are molecules secreted by cells into the extracellular fluid
How are electrical signals and chemical signals different? (Mechanistic approach) Chapter 6, Cell-to-Cell Communication, page 166, left column, third paragraph, 6-9th line
Electrical signals are changes in a cell's membrane potential. Chemical signals are molecules that cells secrete into the extracellular fluid (ECF).
How do endocrine reflexes initiate their pathways if they are not associated with the nervous system? (Mechanistic). Chapter 6, Homeostatic Reflex Pathways, page 185, right column, 9th paragraph, 3rd-4th lines
Endocrine cells are able to both be sensors and integrating centers for the reflex, removing the need to utilize the nervous system for them.
How do the nervous and endocrine systems code for stimulus intensity? (mechanistic approach, chapter 6, coding for stimulus intensity, page 189, left column, paragraph 1, line 5-9)
For the nervous system, in response to an increase in stimulus intensity, the frequency of signaling through the afferent neuron increases. In the endocrine system, the amount of released hormones are increased.
How do GPCRs conduct signals? (Mechanistic)
G protein-coupled receptors (GPCRs) are a large family of membrane-spanning proteins that cross the phospholipid bilayer seven times. The cytoplasmic tail of the receptor protein is linked to a three-part membrane transducer molecule, the G protein. G proteins bind guanosine nucleotides, and inactive G proteins are bound to GDP. Exchanging the GDP for GTP activates the G protein, which then either open an ion channel in the membrane or alter enzyme activity on the cytoplasmic side of the membrane. G proteins linked to amplifier enzymes make up the bulk of all known signal transduction mechanisms. p.174 right column top.
How are G proteins activated? (Mechanistic Approach) Chapter 6, Most Signal Transduction Uses G-Proteins, Page 198, right column, 2nd paragraph, lines 2-8.
G proteins are inactive when bound to GDP and are activated when the GDP is exchanged for GTP. When they are activated, they either open an ion channel in the membrane or alter enzyme activity on the cytoplasmic side of the membrane.
How do G proteins work? (mech) 174, right, paragraph 2, lines 2-7
G proteins work with G protein-coupled receptors. These proteins are bound to GDP and when GDP is exchanged for GTP, the G protein is activated. Upon activation, they can either open ion channels or alter the activity of enzymes on the inner membrane of the cell.
What is the only way that electrical signals can pass directly from cell to cell? (mechanistic). Chapter 6, Cell to Cell Communication, page 166, right column, paragraph 5, 4th-6th lines
Gap junctions are required in order for cells to directly pass electrical signals to each other.
Why are gases considered local signals and what is an example of a has acting as a signal molecule? (Teleological Approach), pg. 178, left column, under Gases Are Ephemeral Signal Molecules, paragraph 1, lines 1-5
Gases are considered local signals because they are short acting paracrine/autocrine signal molecules that act close to where they are produced. Ex: Nitric Oxide
How does histamine work? (Mechanistic approach) Chapter 6, Cell-to-Cell Communication, page 177, left column, paragraph 2, lines 4-12
Histamine is a paracrine molecule that is released from damaged cells. It acts as a paracrine signal, diffusing to capillaries in the immediate area of the injury and making them more permeable to white blood cells and antibodies in the plasma. It also causes fluid to leave the blood vessels and collect in the interstitial space, which leads to swelling around the location of injury.
How does histamine act as a paracrine signal and cause wheals (red, raised area formed after skin is scratched with sharp object) to form? Mechanistic Approach. Pg 192, Left column, Local Communication Uses Paracrine and Autocrine Signals, Paragraph 2, Last 9 lines.
Histamine is released from damaged cells after you are scratched by sharp object > histamine acts as paracrine signal by diffusing into nearby capillaries and making them more permeable to fluid, antibodies, and WBCs > fluid leaks out of blood vessels and collects in interstitial space which causes swelling around the area of injury
How does histamine utilize paracrine signalingl? (mechanistic). Chapter 6, Cell to Cell Communication, page 168, left column, paragraph 3, 5th-11th lines
Histamine is released from damaged cells and is locally diffused through capillaries causing the area of injury to be more permeable to white blood cells and antibodies.
Why are hormones much slower than neural reflexes? (Teleological Approach) Chapter 6, Control Systems Vary in Their Speed and Specificity, page 212, right column, 2nd paragraph, lines 1-6.
Hormone distribution through the body, diffusion from capillary to receptors, and onset of action are all slower than neural reflexes.
Why are neural reflexes much faster than hormonal reflexes? (Teleological Approach, Ch. 6, Pg. 188, Right column, 2nd paragraph, lines 1-6)
Hormones are slower because they have to travel through the circulatory system and go through diffusion through capillaries which is much slower than the extremely fast neural signals. Neural signals can travel as fast as 120m/sec.
How do hormones and neural reflexes differ in respect to time? (mech) Why does this matter? 188, right, paragraphs 1 (lines 1-3) and 2 (lines 1-5) 189, left, paragraph 2, lines 1-4.
Hormones take a much longer time than neural reflexes. Neurons carry the electrical, neural signals much faster (120 m/s). Hormones move through the circulatory system and diffuse through the capillaries to the respective target tissues/cells. Even at the target, it can take minutes or hours before the cellular response can be seen. Endocrine reflexes take longer to be initiated but they also last longer. While the neural signals are quick to be transmitted, their responses are often very quick as well. The speed at which the signal is received corresponds to the duration and purpose of the signal.
What type of ligands bind to G protein- coupled receptors? ch6 pg174
Hormones, growth factors, olfactory molecules, visual pigments, and neurotransmitters.
What type of ligands bind to G protein- coupled receptors?
Hormones, growth factors, olfactory molecules, visual pigments, and neurotransmitters. Pg. 174, Section: Most Signal Transduction Uses G Proteins, column 2, lines 6-8.
How is inositol triphosphate related to calcium? (Mechanistic Approach), pg. 176, left column, paragraph 2, lines 1-6
IP3 is a water-soluble messenger molecule that leaves the membrane and enters the cytoplasm where is binds to a calcium channel on the ER. IP3 binding opens the Ca2+ channel and allows Ca2+ to diffuse out of the ER into the cytosol.
Why does blood clotting show the importance of integrin receptors? (Teleological) Chapter 6, page 176, Integrin receptors transfer Information from the Extracellular Matrix, right column, 3rd paragraph, lines 2-5
In conditions where individuals have platelets that lack integrin receptors, blood clotting is defective
How do protein kinases play a role in signal transduction? (mechanistic approach, chapter 6, membrane proteins facilitate signal transduction, column 2, paragraph 4, line 5-8)
In many signal transduction, after an extracellular signal molecule binds to and activates a membrane receptor, protein kinases become activated. Since protein kinases are enzymes that transfer a phosphate group from ATP to a protein, this phosphorylation of a protein can change a protein's configuration and thus create a response that alter cellular processes.
Why are integrins important? (Teleological approach) Chapter 6, Signal Pathways, page 176, right column, sixth paragraph, 1-3th line
Integrins are membrane-spanning proteins, and they mediate blood clotting, wound repair, cell adhesion and recognition in the immune response, and cell movement during development.
Why is intracellular calcium increased by second messenger molecules? (Teleological approach) Ch 6, pg180
Intracellular calcium is increased because calcium binding to proteins changes their function, which creates a cellular response.
Why is intracellular calcium increased by second messenger molecules? (Teleological approach) Chapter 6, Signal Pathways, page 180, right column, paragraph 3, lines 4-6
Intracellular calcium is increased because calcium binding to proteins changes their function, which creates a cellular response.
What role does troponin serve in the human body? (Mechanistic) Chapter 6, page 178, Calcium Is an Important Intracellular Signal, left column, 1st paragraph, lines 3-4
It is a regulatory protein that calcium binds to in order to initiate muscle contraction in a skeletal muscle cell
Why do pharamaceutical companies develop drugs that block leukotriene synthesis or action? (teleological) Chapter 6, page 179, Some Lipids Are Important Paracrine Signals, left column, fourth paragraph, lines 6-12
Leukotrienes are secreted by white blood cells and play a large role in asthma, which is a lung condition in which the smooth muscle of the airways constricts and makes it difficult to breathe. Drugs that block leukotriene synthesis or action could be useful for individuals with asthma.
Why does a single ligand have different effects in different tissues? (Teleological Approach) Chapter 6, One Ligand May Have Multiple Receptors, page 205, left column, 1st paragraph, lines 6-8.
Ligands bind to different receptor isoforms in different tissues.
What is the difference between lipophobic and lipophilic signal molecules when it comes to the cell membrane? And what do they do once they enter? (Ch 6 pg 178 paragraph 2,3 on right; pg 179 paragraph 1)
Lipophilic molecules can diffuse the membrane because of the phospholipid bilayer's polar outsides. They turn on gene and direct the nucleus to make mRNA. Lipophobic signal molecules remain in the ECF because they can't diffuse and bind to membrane receptor proteins.
What difference is there in where a lipophilic signal molecule versus a lipophobic signal molecule binds to its receptor? (Teleological, Chapter 6, Signal Pathways, pg. 169, right column, lines 10-12, 22-25)
Lipophilic signal molecules enter cells by simple diffusion through the phospholipid bilayer of the cell membrane and bind to cytosolic receptors or nuclear receptors. Lipophobic signal molecules cannot enter cells by simple diffusion and must remain in the ECF and bind to receptor proteins on the cell membrane.
How does local communication work? (Mechanistic Approach, Ch. 6, Pg. 166, Right Column, Paragraph 4, lines 1-9)
Local communication occurs when the gap junction between two cells creates a connection between connexins, a membrane spanning protein, on two adjacent cells. The connexins form a connexon, a protein channel that can transfer chemical and electrical signals. The two cells act as a single cell called a synctium.
How are paracrine and autocrine signals related? (Teleological) Chapter 6 Communication, Integration, and Homeostasis, Local Communication Uses Paracrine and Autocrine Signals, page 168, left column, first paragraph, lines 1-7, second paragraph lines 1-2
Local communication takes place through paracrine and autocrine signaling molecules reaching the target cells by diffusing through the interstitial fluid. A paracrine signal is a chemical that acts on cells in the immediate vicinity of the cell that secreted the signal. An autocrine signal is a chemical signal that acts on the cell that secreted it.
How does local communication occur? (Mechanistic approach) Page 168, Paragraph 2
Local communication takes place through paracrine and autocrine signaling. Paracrine signal is a chemical that acts on cells in the immediate vicinity of the cel that secreted the signal. A chemical signal that acts on the cell that secreted it is called an autocrine signal.
What are the four categories of modified proteins that control cell responses? (Chapter 6 Communication, Integration, and Homeostasis, Signal Pathways, page 176, right column, fourth paragraph, lines 1-4)
Metabolic enzymes, motor proteins for muscle contraction and cytoskeletal movement, proteins that regulate gene activity and protein synthesis, and membrane transport and receptor proteins
Why are modified estrogens in birth control pills considered agonists? How do they work to prevent pregnancy? (Ch 6 pg 190 paragraph 3,4 on right)
Modified estrogens in birth control are agonists because they are ligands that activates the receptor and elicits a response, and because they are synthetic, they are longer-actings and more resistant to breakdown than ligands produced by the body.
Why are hormones an example of long distance communication? (Teleological approach) Page 168, paragraph 5
Most long distance communication occurs through the nervous and endocrine systems. The endocrine system uses hormones, chemical signals that are secreted into the blood and distributed all over the body by the circulation. Only cells with receptors for the hormone are target cells and therefor communicated.
Which two gases are known to activate gaunylyl cyclase and cGMP? (Pg. 178, paragraph 6, sentence 2).
NO (nitric oxide) and CO (carbon monoxide)
Why did researchers decide to design NSAIDS that specifically target COX2? Telelogical Approach. Page 204, Left column, Some lipids are important paracrine signals, All of First full paragraph
NSAIDS block the activity of COX enzymes , thus preventing inflammation, but usage of nonspecific NSAIDS may lead to bleeding in stomach There are two isoforms of COX (COX1 and COX2). COX2 was the enzyme that produces inflammatory prostaglandins, so by targeting COX2, they hoped to focus more on preventing inflammation and thus reduce the negative widespread side effects of nonspecific COX inhibition.
Why is neural control specific but endocrine control more general? (Teleological approach) Chapter 6, Homeostatic Reflex Pathways, page 197, right column, paragraph 1, lines 1-4; paragraph 2, lines 1-7
Neural control is specific because each neuron has a specific target cell to which it sends its message. Endocrine control is more general because the chemical messenger is released into the blood and can go to every cell in the body.
Give the definition of a neurocrine molecule and explain the differences between the three different neurocrine molecules- neurotransmitters, neuromodulators, and neurohormones. (Teleological, Chapter 6, Signal Pathways, pg. 168, right column, lines 1-4)
Neurocrine molecules are chemicals secreted by neurons. A neurotransmitter is a neurocrine molecule that diffuses from the neuron across extracellular space to a target cell and has a rapid-onset effect. Neuromodulators are neurocrine molecules that act more slowly as autocrine or paracrine signals. Neurohormones are neurocrine molecules that diffuse into blood for body-wide distribution.
Why is nitric oxide in the body? (Teleological). Chapter 6, Novel Signal Molecules, page 178, left column, 2nd paragraph, 1st-5th lines
Nitric oxide is a gaseous molecule, and like other soluble gases, is used in short-acting paracrine/autocrine signaling.
Can the internal signal for the cat to pounce on the mouse been transmitted by a paracrine signal? (teleological)
No, a paracrine signal is conducted through chemicals that acts on cells in the immediate vicinity of the cell that secreted the signal, which would not be a sufficient area to coordinate the whole organism response necessary to pounce. The internal signal must have been long-distance communication, likely electrical through neurons. P. 168 Left column.
How do ligand-gated ion channels work? (Mechanistic Approach, Ch.6, Pg. 172, Right Column, Paragraph 1, lines 3-9)
Once a receptor channel protein is activated by an extracellular ligand, a channel gate opens and closes which thereby changes the cell's permeability to ions. This changes the cell's membrane potential which can alter voltage-sensitive proteins within the cell.
How does the body use the simple endocrine reflex pathway to respond to changes in blood glucose level? (mechanistic) Chapter 6, page 189, Complex Reflex Control Pathways Have Several Integrating Centers, right column, paragraph 2, lines 1-10
Pancreatic beta cells monitor blood glucose concentrations by using ATP production in the cell as a measure of glucose availability. When blood glucose levels increase, intracellular ATP production exceeds the threshold and beta cells respond by secreting insulin into the blood. All the target cells in the body with insulin receptors respond to it and initiate processes that take glucose out of the blood.
How do NSAIDs help prevent inflammation? (Mechanistic Approach) Chapter 6, Some Lipids Are Important Paracrine Signals, Page 204, left column, 2nd paragraph, lines 1-3.
Prostaglandins are involved in inflammatory response. Therefore, NSAIDs help prevent inflammation by inhibiting COX enzymes and decreasing prostaglandin synthesis.
How do protein kinases differ from protein phosphatases? (Mechanistic)
Protein kinases are enzymes that transfer a phosphate group from ATP to a protein, while phosphatases remove a phosphate group from the protein of interest. p.171 Right column
How does the input signal in a reflex vary? (Mechanistic approach) Chapter 6, Homeostatic Reflex Pathways, page 186, left column, first paragraph, 1-6th line
Reflex input signals vary depending on the type of reflex. For example, the input signals in a neural pathway are electrical and chemical information transmitted by sensory neurons. Endocrine reflexes, on the other hand, have no input pathway because the stimulus acts directly on the cell, which acts as an integrating center and sensor.
Why is it important that many drugs are now being designed to be specific for only one receptor isoform? (Teleological approach) Chapter 6, Modulation of Signal Pathways, page 190, left column, paragraph 1, lines 1-13
Responses made in the body are not based on the ligand that activates the receptors but rather the receptor isoform and its signal transduction pathway. By being specific for a particular receptor isoform, the drug can have a specialization of response.
Why do selective serotonin reuptake inhibitors (SSRIs) have the potential to help treat depression? (tele) 182, left, paragraph 2, lines 4-9
Selective serotonin reuptake inhibitors inhibit the neurotransmitter, serotonin, from being removed from the extracellular fluid. This can help patients with depression because serotonin levels will be extended for a longer period of time. This can be useful because serotonin can also help maintain mood.
Describe the process and function of signal amplification. (Mechanistic+Teleological, Chapter 6, Signal Pathways, pg. 173, Fig 6.6)
Signal amplification allows for a small amount of signal-such as one ligand-to have a large effect and be multiplied into many intracellular molecules. In signal amplification, the ligand binds to the membrane receptor. Then, the receptor-ligand complex activates an amplifier enzyme. The amplifier enzyme activates several molecules beginning a cascade of producing great amplification of the ligand.
List the steps in a reflex pathway. ch6, pg 185
Stimulus, Sensor, Input Signal, Integrating Center, Output Signal, target, Response.
List the steps in a reflex pathway.
Stimulus, Sensor, Input Signal, Integrating Center, Output Signal, target, Response. Pg. 185, Section: Long-Distance Pathways Maintain Homeostasis, column 2, Figure: 6.16
What is the function of the GPC adenylyl cyclase-cAMP system? (Teleological, Chapter 6, Signal Pathways, pg. 174, right column, lines 27-40)
The GPC adenylyl cyclase-cAMP system is the signal transduction system for many protein hormones. In the system, adenylyl cyclase is the amplifier enzyme that converts ATP to the second messenger cyclic AMP. cAMP then activates protein kinase A which phosporylates other intracellular proteins as part of the signal cascade.
Why do some cells respond to a chemical signal while other cells ignore it? (Teleological approach) Page 169, Paragraph 2
The answer lies in the target cell's receptor proteins. A cell can respond to a particular chemical signal only if the cell has the appropriate receptor protein to bind that signal.
How do integrating centers respond to two or more conflicting signals coming in from different sources? (Mechanistic approach) Chapter 6, Homeostatic Reflex Pathways, page 196, left column, paragraph 6, lines 4-8
The center evaluates each signal on the basis of its strength and importance. Then, it comes up with an appropriate response that integrates information from all contributing receptors.
How does the nervous system use electrical signals to send information throughout the body? (mechanistic) Chapter 6, page 188, Control Systems Vary in Their Speed and Specificity, left column, paragraph 4, lines 1-7
The electrical signals travel through neurons by releasing chemical signals called neurotransmitters, which diffuse across the small gap between the neuron and its target to send the signal.
How does long-distance communication take place via the endocrine system? (Long-Distance Communication May be electrical or chemical, column 1, line 1, page 168)
The endocrine system is able to communicate with the rest of the body through the use of hormones. Hormones are chemical signals that are secreted into the blood and distributed all over the body by circulation. Hormones act on target cells with specific receptors for those hormones.
What is the role of hormones in the endocrine system?(mechanistic approach, chapter 6, left column, long distance communication may be electrical or chemical, page 168, paragraph 1, line 1-6)
The endocrine system releases hormones, which are chemical signals that are secreted into the blood and distributed all over the body by circulation, for the communications between cells.
How are leukotrienes produced? (Mechanistic, Chapter 6 Communication, Integration, and Homeostasis, Novel Signal Molecules, page 179, left column, fifth paragraph, lines 1-2.)
The enzyme lipoxygenase acts on arachidonic acid
How is the G protein coupled receptor involved in cell signaling? (Mechanistic) pg 179, figure 6.3 c.
The extracellular signaling molecules will bind to the membrane receptor. This then causes a cellular effect, such as opening an ion channel, or changes the enzyme activity.
Why can a particular ligand cause a response A in cell type 1 but also a response B in cell type 2? In other words, why does one signaling molecule cause different behavioral responses in different cell types? (Teleological Approach) Chapter 6, One Ligand May Have Multiple Receptors, page 180, right column, paragraph 5, lines 1-5
The ligand is not the primary determinant of cellular response; most often, target cell response depends on its receptor or associated intracellular pathways, not as much on the ligand. A particular ligand can stimulate multiple intracellular pathways in one cell relative to another cell, and therefore, cause a unique cellular response.
What is a physiological example of a tonically controlled system? (Pg. 183, paragraph 3, sentence 1-3).
The minute-to-minute regulation of blood vessel diameter by the nervous system. The amount of neurotransmitter determines the blood vessel's response: the more neurotransmitter, the greater the input of the nervous system that causes a decrease in vessel diameter.
According to Cannon's postulates, how does the nervous system play a role in maintaining the conditions of the internal environment vital for normal function? (mechanistic approach, chapter 6, Cannon's postulates describe regulated variables and control systems, left column, page 183, paragraph 2, line 4-8)
The nervous system coordinates and integrates blood volume, blood osmolarity, blood pressure, and body temperature, among other regulated variables.
Why do we need the reflexes of the nervous system to be so quick? (Teleological approach) Chapter 6, Homeostatic Reflex Pathways, page 188, right column, ninth paragraph, 1-12th line
The reason is that chemical signals are too slow to travel all the way from our brain to the farthest parts of our body, like our feet. In the presence of a predator, we need a signal fast enough to tell us to escape, and a chemical signal would take a long time to travel all the way to our feet.
Why do some adrenergic receptors prefer epinephrine vs norepinephrine? (Teleological Approach, Ch. 6, Pg. 180, Right Column, Paragraph 2, lines 1-5)
The reason some adrenergic receptors prefer one over the other is that adrenergic receptors come in two isoforms (alpha and beta) with alpha preferring norepinephrine and beta preferring epinephrine.
What is the order of the response loop? What would happen if the input signal sent an efferent instead of an afferent signal? (Ch 6 pg 194, 195, figure 6.16, paragraph 1 on left)
The response loop goes as such: stimulus=> sensor => input signal => integrating center => output signal => target => response. If the input signal sent out an efferent response, the signal would go back to the sensor without first going to the integrating center, and thus would disrupt the feedback loop.
What are some features that all signal pathways share? Chapter 6, Signal pathways, page 169, left column, third paragraph, 4-12th line
The signal molecule is a ligand that binds to a protein receptor. The ligand is also known as a first messenger because it brings information to the target cell. Ligand-receptor binding activates the receptor. The receptor in turn activates one or more intracellular signal molecules. The last signal molecule in the pathway creates a response by modifying existing proteins or initiating the synthesis of new proteins
How do paracrine and autocrine signal molecules reach their target? (Mechanistic approach), Ch 6, Cell-to-Cell Communication, page 168, left column, 3rd paragraph, line 1-2
The signal molecules reach their target through diffusion, and since distance is limiting the effective range is only local.
What are gap junctions and how do they form? (Mechanistic approach) Chapter 6, Gap junctions create cytoplasmic bridges, page 166, right column, first paragraph, 1-9th line
The simplest form of cell-to-cell communication is the direct transfer of electrical and chemical signals through gap junctions, protein channels that create cytoplasmic bridges between adjacent cells. A gap junction forms from the union of membrane-spanning proteins, called connexins, on two adjacent cells. The united connexins create a protein channel that can open and close. When the channel is open, the connected cells function like a single cell that contains multiple nuclei
What is the stimulus, sensor, integrating center, output signal, target, and response in the insulin pathway?
The stimulus is the increase in blood glucose levels, which is sensed by beta cells of the pancreas. The signal is integrated in the beta cells, which output an insulin signal by secreting it into the blood, and any cells in the body which responds to beta cells are targeted. The final response is the cellular uptake and use of glucose. p.192
Name at least three different types of local communication that cells engage in? (ch 6 pg 176 Figure 6.1 parts a,b,c) And what purpose to these have in the body?
The three different types of local communication are gap junctions, contact-dependent signals and autocrine and paracrine signals. They are there to enhance cell-to-cell communication locally to maintain homeostasis and coordinate function by chemical and electrical signaling.
How can receptor activity be terminated in the cell? (Mechanistic Approach), pg. 182, left column, under Cells Must Be Able to Terminate Signal Pathways, paragraphs 2 and 3, lines 1-8 and lines 1-2
There are 3 main ways. 1) The extracellular ligand can be degraded by enzymes in the extracellular space.. 2) Other chemical messengers (especially neurotransmitters) can be removed from the extracellular fluid. 3) Endocytosis can occur of the receptor-ligand complex.
Why is calcium important? (Teleological) Chapter 6 Communication, Integration, and Homeostasis, Calcium Is an Important Intracellular Signal, page 177-178, right and left columns, numbering
There are many events that are calcium-dependent. Calcium alters (1) enzyme or transporter activity or the gating of ion channels and (2) movement of contractile or cytoskeletal proteins. It also (3) triggers exocytosis of secretory vesicles, (4) alters gating state of ion channels, and (5) initiates development of the embryo
How does signal amplification occur in G protein coupled receptors? (Mechanistic) pg 182, figure 6.6 c
There are many steps involved in the signal transduction of G protein coupled receptors, so there are many steps that can cause amplification. Adenylyl cyclase can cause amplication, as can the Protein Kinase A.
How does signal amplification occur in G protein coupled receptors? (Mechanistic) ch6, pg 182
There are many steps that can cause amplification. Adenylyl cyclase can cause amplication, as can the Protein Kinase A.
How does gap junction selectivity vary from tissue to tissue? (Mechanistic Approach) Chapter 6, Gap Junctions Create Cytoplasmic Bridges, Page 190, right column, 6th paragraph, lines 1-4.
There are more than 20 different isoforms of connexins that combine in different ways to form gap junctions. This difference
How does the alpha epinephrine receptor different from the beta epinephrine receptor? (Mechanistic) pg 19
They are found in different places. Alpha receptors are in the intestine, while beta receptors are in skeletal muscles.
How does the alpha epinephrine receptor differ from the beta epinephrine receptor? (Mechanistic) pg 190, Figure 6.13
They are found in different places. Alpha receptors are in the intestine, while beta receptors are in skeletal muscles. When epinephrine binds to the alpha receptor, the vessels contract, while when it binds to the beta receptor, the vessels dilate.
How did G proteins obtain their name? Chapter 6, Most Signal Transduction Uses G Protein, 2nd paragraph, lines 1-8
They bind guanosine nucleotides. So when they're inactively, they are bound to guanosine diphosphate, and in order to activate the g protein, it has to be attached to a guanosine triphosphate
What are the roles of selective serotonin reuptake inhibitor (SSRI) drugs? (Mechanistic) Chapter 6, page 182, Cells Must Be Able to Terminate Signal Pathways, left column, 2nd paragraph, lines 7-10
They extend the active life of the neurotransmitter serotonin by slowing its removal from the extracellular fluid
Why is secretion into the extracellular compartment not efficient?
This is not a very specific way for these signals to find their targets because substances that diffuse through interstitial fluid or that travel through the blood come in contact with many cells. Pg. 169, Section: Signal Pathway, column 1, lines: 3-5
How do gap junctions form? (mechanistic) Chapter 6, page 166, Gap Junctions Create Cytoplasmic Bridges, right column, paragraph 1, lines 4-9
Two membrane-spanning proteins called connexins on the two adjacent cells unite to create a protein channel, called the connexon, which can open and close. When the channel is open, all the united cells act as a single cell with multiple nuclei, called a syncytium.
How are cytokines different from classic hormones?(Mechanistic approach) Chapter 6, Cell-to-Cell Communication, page 168, right column, tenth paragraph, 1-7th line
Unlike classic hormones, specialized epithelial cells do not make cytokines. At some point in its lifetime, any nucleated cell can secrete cytokines. Cytokines are not made in advance and stored like classic hormones, and the signaling pathway for cytokines usually differ from those for classic hormones.
What are two important functions of activated G proteins in signal transduction? (mechanistic approach, chapter 6, Most Signal Transduction uses G proteins, page 174, right column, paragraph 2, line 5-8)
When G proteins are activated, they can either open an ion channel in the membrane or alter enzyme activity on the cytoplasmic side of the membrane.
Why is the activation of receptor-channels the most rapid intracellular response of all receptors? (Teleological approach), Ch 6, Signal Pathways, page 172, right column, 1st paragraph, lines 4-6
When a ligand binds to the receptor protein, the channel gate opens or closes immediately. This allows for the permeability of ions to enter or leave.
Why are the relationships between an antagonist ligand and a receptor and an agonist ligand and a receptor different? (Teleological, Chapter 6 Communication, Integration, and Homeostasis, Modulation of Signal Pathways, page 180, right column, paragraph 3, lines 1-8)
When a receptor combines with an agonist of the primary ligand, the receptor is activated, causing a response. When a receptor combines with an antagonist of the primary ligand, the receptor is blocked from responding.
How is an intracellular Ca2+ signal created within a cell upon ligand binding of a G protein-coupled receptor? (Mechanistic Approach) Chapter 6, G Protein-Coupled Receptors Also Use Lipid-Derived Second Messengers, page 174, right column, paragraph 6, lines 1-6
When a signaling molecule binds a G protein-coupled receptor, it activates a G protein. This G protein stimulates an phospholipase C, which converts a phosphatidylinositol bisphosphate into two lipid-derived second messenger molecules: diacylglycerol and inositol trisphosphate (IP3). IP3 diffuses into the cytoplasm and releases Ca2+ from the endoplasmic reticulum, creating a Ca2+ signal.
How does the acetylcholine-gated monovalent cation channel of skeletal muscle lead to muscle contraction? (pg. 172, paragraph 4 sentence 2-5).
When acetylcholine attaches to the channel, the channel protein is activated and Na+ flows into the cell and K+ flows out of the cell along their electrochemical gradient. The sodium gradient is stronger and the net entry of positively charged Na+ depolarizes the cell. This cascade of intracellular events results in muscle contraction.
How do receptor-channels create an electrical signal? (Mechanistic approach) Chapter 6, The Most Rapid Signal Pathways Change Ion Flow through Channels, page 172, right column, paragraph 1, line 2
When extracellular ligand binds to receptor-channel protein, a channel gate opens/closes, altering cell's permeability to an ion. Increasing/decreasing ion permeability changes cell's membrane potential which creates an electric signal that alters voltage-sensitive proteins.
Why do humans require the speedy reflexes of neurons? (Teleological Approach) Chapter 6, Speed, page 188, right column, paragraph 3, lines 2-12
When humans visualize an object, a signal moves from the eyes to the brain down to some periphery if some response is required. Due to the significant separation of these organs in the human body, it could potentially take minutes for such a signal to process if the signal is not quick enough. Because our nervous system dictates a lot of mechanical response, it must utilize speedy reflexes to perform the required responses in a situation.
How does the secretion of the hormone insulin change in response to changes in the blood glucose levels? Chapter 6, Complex Reflex Control Pathways Have Several Integrating Centers, 4th paragraph, lines 3-8
When intracellular ATP increases above a threshold, it is a sign that there is an excess amount of glucose. The pancreatic beta cells monitors the ATP levels, and when it increases past the threshold, more insulin is released, which initiates the process of removing glucose out of the blood.
Why do cells only respond to some signals? (teleological approach) Chapter 6, p 178, Signal Pathways, left column, paragraph 2
a cell can only respond to a chemical signal if it has a receptor for that signal
How do two cells function as a syncytium? Chapter 6, p 175, Gap Junctions Create Cytoplasmic Bridges, right column, paragraph 3
by forming a gap junction that is open
How do paracrine and autocrine signals reach their targets? (mechanistic approach) Chapter 6, p 177, Paracrine and Autocrine Signals Carry Out Local Communication, left column, paragraph 3
by traveling through the interstitial fluid
How do lipophobic molecules enter the cell? (mechanistic approach) Chapter 6, p 179, Receptor Proteins are Located Inside the Cell or on the Cell Membrane, left column, paragraph 1
they bind to receptors on the extracellular side of the membrane
