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Chapter 5
Chemical Messengers
Question | Answer |
---|---|
Long distance communication centers of the body: | Nervous system and Endocrine system. |
What is the Nervous System made up of? | Neurons and supporting cells. |
T/F: A particular neuron can span a long distance? | True |
How does the Nervous System communicate signals? | Transmit signals down the length of their axon; turns into chemical signal at the axon terminals. |
T/F: Fast communication but is over quickly too? | True |
Endocrine System relies on ___________ ___________ to deliver hormones. | Circulatory System |
T/F: Endocrine System has direct contact with its' target. | False, relies on hormones. |
What is the Endocrine System able to offer that Nervous System does not? | SLOW acting, but able to offer prolonged communication which is important for coordination homeostasis (metabolism, cell growth) and for specialized processes like reproduction and lactation. |
Direct communication | Gap Junctions - connexin: plasma proteins that come together to form channels. |
Indirection communication | Chemical Messengers |
What is the general method of communication? | via Chemical Messengers |
T/F: Ligand is a chemical messenger? | True |
What does the ligand do? | Ligand binds to its receptor on target cells. |
What happens when the Ligand binds to the receptor? | It causes signal transduction. |
Signal Transduction | causes physiological response: |
What are types of physiological response of signal transduction? | a. induces changes w/n proteins already existing inside of the cell. b. induces the cell to make new protein (transcription/translation) |
Distance B/W ligand released and target cell determines action: | Autocrine, paracrine, and endocrine. |
Autocrine | Fast-acting, short-lived. |
How does Autocrine regulate its own cellular activity (usually inhibitory; short negative feedback loop): | by secreting ligand into ISF; diffuses back to self. |
Paracrine | Fast-acting, short-lived. |
T/F: Paracrine regulates neighboring cellular activity? | True |
How does Paracrine regulate neighboring cellular activity? | by secreting ligand into ISF; diffuses into neighbor cells. |
What is an example of Paracrine in action? | Delta cells of the pancreas modulate the production of glucagon and insulin through somatostatin. |
Define Somatostatin | Growth hormone- inhibiting hormone; regulates Endocrine system... |
Alpa cells secretes | glucagon. |
Beta cells secretes | insulin. |
Delta cells secretes | somatostatin. |
Endocrine | Longer time to action, Longer half life. |
How does Endocrine regulate a distant target? | by releasing a hormone into the bloodstream. |
Lipophilic/hydrophobic | Can easily cross membrane. |
Where are the receptors for lipophilic/hydrophobic located? | Intracellularly (cytosol or nucleus), |
Lipophobic/hydrophilic | Cannot cross the plasma membrane without assistance. |
Where are the receptors for lipophobic/hydrophilic located? | Plasma membrane. |
Define Half-Life: | Time it takes for half of the ligand in the plasma to be degraded. |
T/F: Half-Life measure of ligand lifespan in the brain? | False, measures of ligand lifespan in the body. |
What is the Half-Life of autocrine and paracrine ligands? | Short. |
What is the Half-Life of endocrine hormones? | Longer. |
T/F: Time to degradation depends on how the ligand is transported? | True |
Which ligand does not require carriers? | Lipophobic/hydrophilic |
Which ligand use carrier proteins? | Lipophilic/hydrophobic |
Why does lipoPHILIC/hydroPHOBIC use carrier proteins? | Protect them from degradation (prolong their half-life), allow them to travel in ISF and plasma, Ligand must separate from its carrier to be active. |
Active ligand amounts to... | "free" |
Type of carriers: | 1. specific: only shuttle a specific ligand or class of ligands. 2. general: carry a variety of ligands. a. albumin |
What are the 5 chemical classes of ligands? | 1. Amino Acids, 2. Amines, 3. Protein/peptides, 4. Steroids, 5. Eicosanoids. |
Amino Acids... ACT AS, Synthesized inside, Stored in: | Neurotransmitters, Neurons, stored in vesicles until needed; released by exocytosis. |
Where are the receptors located in amino acids? | Plasma membrane; lipophobic |
Examples of Amino Acids? | Gluatmate, Aspartate, Glycine, and GABA (gamma-aminobutyric acid). |
Amines... Derived from, Synthesized in, Stored in: | AA, Cytosol (created by enzymatic reactions), stored in vesicles until needed; released by exocytosis. |
T/F: Amines are lipophobic? | True, except the thyroid hormones. |
Examples of Amines? | Catecholamines: norepinephrine (Neurotransmitter), epinephrine (hormone), dopamine (N), serotonin (N), thyroid hormones, histamine (paracrine). |
Peptides are | huge class of ligands: hormones, neurotransmitters, cytokines. |
Peptides are... Synthesized, Stored in, Classified by: | Classical translation (rough ER and ribosomes), stored in vesicles until needed; released by exocytosis, and are classified by size. |
T:F: Peptides are lipophilic? | False, it is lipophobic. |
Steroid... Derived from, Synthesized on, Stored in: | Cholesterol; series of enzymatic reactions converts cholesterol into desired steroid. Synthesized on demand and immediately released. CAN'T BE STORED inside cell; when made, they diffuse out of cell. |
Steroids | lipophilic; nuclear receptors. |
Eicosanoids | Paracrines secreted by many different cell types. |
Eicsanoids... Synthesized, Stored in: | On demand and immediately released. CAN'T be stored inside cell. |
Examples of Eicosanoids | Prostaglandins, leukotrienes. |
T/F: Eicosanoids are lipophilic. | True |
Steroid Action 1: | Steroid diffuses through cell and binds to its receptor in the nucleus (nuclear receptor) = hormone-receptor complex (HR). |
Steroid Action 2: | The HR binds to DNA to drive transcription of a particular gene. |
Steroid Action 2a: | HR binds to hormone response element (HRE). |
Steroid Action 2b: | HRE is located at the starting sequence of the desired gene. |
Steroid Action 3: | Transcription proceed-->mRNA; mRNA travels into cytosol. |
Steroid Action 4: | Translation process. |
Eicosanoid 1: | Eicosanoid binds to its receptor in the cytosol= HR |
Eicosanoid 2: | HR diffuses into nucleus. |
Eicosanoid 3: | The HR binds to DNA to drive transcription of a particular gene. |
Eicosanoid 3a: | HR binds to hormone response element (HRE). |
Eicosanoid 3b: | HRE is located at the starting sequence of the desired gene. |
Eicosanoid 4: | Transcription proceeds--> mRNA; mRNA travels into cytosol. |
Eicosanoid 5: | Translation process. |
HR | Hormone-receptor complex |
HRE | Hormone-response element |
What are the types of receptors on the plasma membrane? | Channel- linked receptor, enzyme-linked receptor, and G protein-linked receptor. |
Which are the fast receptors? | Channel-linked and enzyme-linked. |
Which one is a slow receptor? | G protein-linked. |
What can FAST ligand-gated channels do? | When it binds to R, opens channel. R and channel are same protein. ONLY OPEN a channel. Immediate response but the channel will open ONLY BRIEFLY. |
What can SLOW ligand-gated channels do? | G-protein-linked R. R and channel are separate proteins, but are linked by another protein (G protein). OPEN AND CLOSE a channel. Slower response but the channel can remain regulated for a LONG PERIOD OF TIME. |
Ions enter through a channel, physiological responses: | Contraction, secretion, change the electrical properties of the cell (alters the electrical potential), ion can act as a 2nd messenger. |
What is a 2nd messenger? | an intracellular messenger that is produced by a ligand (1st messenger) binding to its receptor. |
Tyrosin Kinase System | Insulin uses this signaling system to trigger the increase of GLUCOSE transporters to the plasma membranes of cells throughout body and increases anabolic processes w/n liver, SKM, and fat cells. |
TKA 1: | Ligand (insulin) binds to its receptor. |
TKA 2: | The receptor undergoes a conformational change and becomes an activated enzyme (tyrosine kinase). |
TKA 3: | The enzyme phosphorylates proteins-->physiological response. |
Calcium-Camodulin System 1: | Ligand binds to its receptor. |
Calcium-Camodulin System 2: | The receptor udnergoes a conformational change and becomes a calcium channel. |
Calcium-Camodulin System 3: | CA++ flows into the cell. |
Calcium-Camodulin System 4: | Working as a second messenger, it binds to Calmodulin creating a CA-Calmodulin complex. |
Calcium-Camodulin System 5: | This complex activate Protein kinase (an enzyme). |
Calcium-Camodulin System 6: | The enzyme phosphorylates proteins-->physiological response. |
This system can trigger muscle contraction, and can affect metabolism and transport. | Calcium-calmodulin system. |
G protein signaling cascades 1: | Ligand will bind to its receptor (causing a change of shape in G protein will become loose, dissociates-->then back to normal.) |
G protein signaling cascades 2: | causes the conversion of GDP-->GTP (alpha subunit dissociates.) |
G protein signaling cascades 3: | Activate G protein alpha subunit will dissociates and bind to target protein (a channel or enzyme) (activates enzymes, go inside cell, and activates 2nd messenger.) |
G protein signaling cascades 4: | The channel or enzyme is now activated. (Tell more enzymes) |
G protein signaling cascades 5: | Phosphorylate proteins-->physiological response. (Increased #s of whatever protein it wants) |
cAMP (cyclic monophosphate) 2nd messenger system: | LH, FSH, TSH, Glucagon, PTH, calcitonin, ADH, ACTH etc. all use this signaling cascade to cause their physiological response. |
cAMP 1: | The ligand binds to its receptor, activating the G protein. |
cAMP 2: | The alpha subunit binds and activates adenylate cyclase. |
cAMP 3: | Adenylate cyclase converts ATP to cAMP. |
cAMP 4: | Acting as a 2nd messenger, activates protein kinase A (PKA) |
cAMP 5: | Causes the phosphorylation of proteins-->physiological response. |