Anatomy exam 1 part2 Flashcards
Describe autocrine, paracrine, and endocrine signaling
The main difference between the different categories of signaling is the distance that the signal travels through the organism to reach the target cell. … Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell.
Endocrine : distant target cells, hormone secretion into blood by endocrine gland
Paracrine signaling: adjacent target cell
Autocrine: target sites on same cell
Describe the Trimeric G proteins, GPCR (G Protein coupled receptors) including the role of GTPase activity in self-limitation (inactivation)
- G protein coupled receptor
- Bound receptor activates G protein
- adrenergic Receptors
- Muscarinic AChR
- mGlutamate receptors
- Dopamine Receptors
- GABAB Receptors
- Most 5-HT receptors
G s, i, q, y
Heterotrimeric GTP-binding protein
Heterotrimeric G proteins are the molecular switches that turn on intracellular signalling cascades in response to the activation of G-protein-coupled receptors (GPCRs) by extracellular stimuli.
G protein-coupled receptors (GPCRs),
seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein–linked receptors (GPLR)
Major second messengers in signal transduction
cAMP: activates protein kinase A
cGMP: activates protein kinase G (PKG) and open cation channels in rod cells
DAG: activates protein kinase (PKC)
IP3: opens Ca2+ channels in endoplasmic reticulum
Describe the reaction catalyzed by adenylyl cyclase, guanylyl cyclase, and cyclic nucleotide phosphodiesterase (Reactants and products)
Enzymes that catalyze the formation and inactivation of the second messenger, cAMP
ATP–> adenylyl cyclase—> cAMP—>cyclic nucleotide phosphodiesterase–> AMP
Describe the signaling through adrenergic beta receptors including cAMP and PKA
norepinephrine neutrotransmitter enters the recptor and goes through G protein Gs and effector protein (adenylyl cyclase), second messengers cAMP, later effectors (protein kinase A), target action (increase protein phosphorylation).
Effector pathway of metabotropic glutamate receptor
Describe the signaling through Gq, PLC pathways including the roles of PIP2, DAG, IP3, IP3 receptor, Ca release and PKC activation
neurotransmitter : glutamate
receptor : mGluR
G protein: Gq
Effector protein phospholiase C
Second messengers diacyglycerol IP3
later effectors: Protein kinase C and Ca2+ release
target action increase protein phosphorylation and activate calcium-binding protein
Describe the role of calmodulin
§Calmodulin is a major calcium binding protein
- Binds 4 calcium ions per molecule
- High affinity for target enzymes
- Calcium-Calmodulin Dependent Protein Kinase (CaMKII, CaMKIV)
- Phosphodiesterase (PDE)
- Adenylyl Cyclase (AC)
- Protein Phosphatase 2B (PP2B = calcineurin)
name the second messengers
- cyclic nucleotides (e.g., cAMP and cGMP)
- inositol trisphosphate (IP3) and diacylglycerol (DAG)
- calcium ions (Ca2+)
Calcium as Second Messenger
source:
plasma membrane: voltage gated Ca2+ channels various ligand gated channels
Endoplasmic reticulum: IP3 receptors ryanodine receptors
Itracellular targets
Calmodulin protein kinasees protein phosphatases, ion channel, synaptotagmin, Ca2+
Removal
plama membrane: Na+/Ca2+ exchanger
Endoplamic ret: Ca+pump
mitochondria
List and describe the major second messengers
Regulation of cellular proteins by phosphorylation
Describe protein kinases and phosphatases
receptors are activated/deactivated by phosphorylation and dephosphorylation events, by means of kinases and phosphatases
Protein kinases and phosphatases are enzymes catalysing the transfer of phosphate between their substrates. A protein kinase catalyses the transfer of -phosphate from ATP (or GTP) to its protein substrates while a protein phosphatase catalyses the transfer of the phosphate from a phosphoprotein to a water molecule.
Describe steroid hormone signaling
Nuclear Receptors: Glucocorticoids
- Glucocorticoid hormone receptors
- Located in the cytoplasm
- Bind to soluble glucocorticoids - Binding of glucocorticoids causes receptor to translocate to the nucleus
- Bound receptor is a transcription factor, binds to recognition site on DNA
- Activates transcription and gene expression
general scheme of the ANS pathways (Two synapse chains)
Efferent Pathways
ANS pathway is a two-neuron chain
1.Preganglionic neuron (in CNS) has a thin, lightly myelinated preganglionic axon
2.Ganglionic neuron in autonomic ganglion has an unmyelinated postganglionic axon that extends to the effector organ
Describe the effects caused by SNS and PNS
- Describe the effects caused by SNS and PNS
Role of the Sympathetic Division
- Mobilizes the body during activity; is the “fight-or-flight” system
- Promotes adjustments during exercise, or when threatened
- Blood flow is shunted to skeletal muscles and heart
- Bronchioles dilate
- Liver releases glucose
- Describe the effects caused by SNS and PNS
Role of the Parasympathetic Division
- Promotes maintenance activities and conserves body energy
- Its activity is illustrated in a person who relaxes, reading, after a meal (rest and digest)
- Blood pressure, heart rate, and respiratory rates are low
- Gastrointestinal tract activity is high
- Pupils are constricted and lenses are accommodated for close vision
Autonomic Sympathetic and Parasympathetic Pathways
Sympathetic pathways use
Acetylcholine and norepinephrine —> ACh–> nicotinic receptor–> autonomic ganglion –>norepinephrine–> agrenergic receptor –> target tissue
Parasympathetic pathway use
acetylcholine–> ACh—> nicotinic receptor–> autonomic ganglion—>ACh—> Muscurinic receptor
Cholinergic fibers release the neurotransmitter
ACh
- All ANS preganglionic axons
- All parasympathetic postganglionic axons
Adrenergic fibers release the neurotransmitter
norepinephrine
- Most sympathetic postganglionic axons
- Exceptions: sympathetic postganglionic fibers secrete ACh at sweat glands and some blood vessels in skeletal muscles
Receptors for Neurotransmitters
- Cholinergic receptors for ACh
- Adrenergic receptors for NE
Nicotinic vs muscarinic receptors
Nicotinic receptors are responsive to the agonist nicotine, while muscarinic receptors are responsive to muscarine. The two receptors differ in function as ionotropic ligand-gated and G-protein coupled receptors, respectively.Sep 6, 2020
Pregangionic Transmission and Parasympathetic Postganglionic Transmission
Muscarinic receptors
- G protein-coupled
- At least five subtypes
- M1,M3, and M5 appear to couple to the same Gq proteins and signal through DAG/IP3 pathways.
- M2 and M4 couple through Gi/o proteins and signal through cAMPpathways.
- Describe the cell signaling through muscarinic M1 receptors
M1,M3, and M5 couple to the same Gq proteins and signal through DAG/IP3 pathways.
M2 and M4 couple through Gi/o proteins and signal through cAMP pathways.
Parasympathetic Physiological Actions
§Constricts pupils and bronchioles
§Slows heart
§Stimulates
- Digestion
- Insulin release
- Urination
Erections
The Adrenal Medulla
Adrenal cortex is a true endocrine gland
Adrenal medulla is a modified sympathetic ganglion.
preganglionic sympatheic neuron to ACh
chromafin cell is modified postganglionic sympathetic neuron
epinephrine is neurohormone that enters blood to target tissues
epinephrine at B2 receptor
norepinephrine at B1 receptor
Adrenergic Receptors include
Two types
- Alpha (a) (subtypes a1, a2)
- Beta (b) (subtypes b1, b2 , b3)
-Effects of E/NE depend on which subclass of receptor predominates on the target organ
Autonomic Control Centers in the Brain
- Hypothalamus
•Water balance, temperature, and hunger
- Pons
•Respiration
- Medulla
- Respiration
- Cardiac
- Vomiting
- Swallowing
- Define dual innervations
- Most visceral organs have dual innervation
- Dynamic antagonism allows for precise control of visceral activity
- Sympathetic division increases heart and respiratory rates, and inhibits digestion and elimination
- Parasympathetic division decreases heart and respiratory rates, and allows for digestion and the discarding of wastes
- Describe the brain structures that regulate ANS
§Hypothalamus —main integrative center of ANS activity
§Subconscious cerebral input via limbic lobe connections influences hypothalamic function
§Other controls come from the cerebral cortex, the reticular formation, and the spinal cord
- Define antagonistic and cooperative actions of SNS and PNS and give some examples
-Most internal organs are under antagonistic control
- One autonomic branch is excitatory and the other branch is inhibitory
- Example:
- Effector organ: heart
- Parasympathetic response: slows rate
- Sympathetic response: increases rate and force of contraction
- Define antagonistic and cooperative actions of SNS and PNS and give some examples
-Some organs are under cooperative control
- Salivation and sexual activity
- Example:
- Saliva: salivation is stimulated by both sympathetic (mucous part) and parasympathetic branches (watery part)
- Sexual activity: parasympathetic branch stimulates erection and sympathetic is important for ejaculation
Summary: Somatic and Autonomic Nervous
