Communication, Integration, and Homeostasis Flashcards
What are the 2 key control systems for coordinating body function
Endocrine and nervous
What are the different kinds of signals utilized in the body
Local and long distance, and chemical and electrical
What are the characteristics of intercellular communication
Cell-to-cell, local, utilizes gap junctions (channels from cytoplasm to cytoplasm), and can be juxtacrine, autocrine, or paracrine
What does juxtacrine mean
Secretes alongside, i.e. contact-dependent communication (interaction between membrane molecules on each cell)
What does autocrine mean
Self-secreting, i.e. cell sends a signal back to itself
What does paracrine mean
Secreting nearby, i.e. the cell sends a signal to another nearby cell
What is a hormone
A substance secreted by an endocrine cell into the blood
What is an example of long distance communication via endocrine cells
Hormones
What is a neurocrine
A substance secreted by a hormone
What are the 3 types of neurocrines
Neurohormones (secreted into the blood), neurotransmitters (released onto neighboring cells - paracrine), and neuromodulators (modify the response of cells)
What are excitable cells
Cells that use electrical signals to communicate with other cells in the body (Neurons, endocrine cells, muscle cells)
What are electrical signals
Changes in membrane potential
What is the average membrane potential for a cell
-65 mV
What is membrane potential
Electrical potential difference = Vm = voltage = stored energy (based on charge separation at the membrane, inside relative to outside)
What does membrane potential depend on
Total ion concentrations (each ion’s preference) and selective membrane permeability (number of leakage channels)
What are the two forces ions are subject to
Chemical/diffusional (based on concentration), and electrical (based on ionic charge/valence versus the charge on membrane)
What is electrochemical equilibrium
When the chemical and electrical forces are equal and opposite for an ion species
What is equilibrium potential (Ex)
The electrical force needed to counterbalance the chemical force (What the ion wants the membrane potential to be)
What does E(x) depend on
Concentrations of an ion species across the membrane and the ions charge or valance
What equation can be used to calculate E(x)
Nernst equation
What is E(K)
-90mV
What is E(Na)
+60 mV
What is E(Cl)
-63 mV
What is E(Ca)
+240 mV
What ion is the membrane most permeable to
K
What equation approximates Vm
Vm proportional to pK(Ek) + pNa(ENa) + pCl(ECl)
What equation can be used to calculated Vm
Goldman-Hodgkin-Katz (GHK) Equation
How are concentration gradients maintained over time
Active transporters (Na/K ATPase)
–> If not working, Vm would change very slowly over time
What changes during electrical signaling
Permeability (gated channels), NOT CONCENTRATION (because bulk of ions don’t affect Vm)
What are the 3 kinds of gated channels
Chemically-gated (neurotransmitter, hormone, or phosphate), mechanically-gated, or voltage-gated (because proteins making up channels have polar amino acids)
What is depolarization
Getting more positive
What is hyperpolarization
Getting more negative
What is repolarization
Returning to Vrest
What is a ligand
A chemical used for signaling purposes
What features do receptors exhibit
Specificity, competition, and saturation
What are the 3 kinds of membrane proteins that facilitate signal transduction
Receptor-channel (gated channels), GPCRs, and catalytic receptors
What are the 2 kinds of catalytic receptors
Receptor-enzyme and integrin receptors
What is the fastest membrane protein for signal transduction
Receptor-channels
What is the most common membrane protein for signal transduction
GPCRs
What is signal transduction
Moving information from one side of the membrane to another using membrane proteins (ligand doesn’t cross membrane but binds to receptors)
What is a signal transduction pathway
What happens between a ligand binding to a receptor and the cellular response occuring
What is always the 1st messenger
Ligand
What converts information to another form in a signal transduction pathway
The transducer/receptor
What are examples of cellular responses
Change in Vm, exocytosis of secretory vesicles, altered enzyme activity, movement of motor proteins, and gene activity/protein synthesis
What can receptors activate
Ion channels, protein kinases, phosphatases, or amplifier enzymes
What do protein kinases do
Phosphorylate proteins
What do phosphatases do
Dephosphorylate proteins
What 3 things can 2nd messengers do
Activate gated ion channels, increase intracellular Ca, or alter enzyme activity
What determines a cell’s response to a ligand
Presence/absence of that ligand’s receptor and what type of internal signal pathway that cell has
What are GPCRs
G-protein coupled receptors, membrane-spanning proteins with extracellular binding site, and a cytoplasmic tail linked to a G protein (transducer molecule with three parts)
What are the two most common amplifier enzymes
Adenyl (anedylyl, adenylate) cyclase and phospholipase C
When a G protein is activated what happens
It undergoes a conformational change that makes it swap out GDP for GTP
What are the steps of the cAMP pathway
Ligand (1st messenger) binds to GPCR (transducer), activates G protein, activates adenyl cyclase (amplifier enzyme), creates cAMP (2nd messenger), activates protein kinase A (amplifier enzyme), phosphorylates proteins
What does adenyl cyclase do
Converts ATP into cAMP
What do phosphodiesterases do
Break down cAMP
What stops signal transduction
Inherent GTPase activity (shuts off G protein), phosphodiesterase, and phosphatases
What happens in the phospholipase C system
Ligand binds, g protein activated, PL-C activated, membrane bound DAG is broken into PK-C (protein kinase C) which phosphorylates proteins and IP3 (Inositol triphosphate) which binds to the ER to release stored Ca
What can adrenergic receptors bind to
Epinephrine and norepinephrine
What does catecholamines mean
Similar in structure
What is a difference between epinephrine and norepinephrine
Epinephrine is released as a hormone, while norepinephrine is released as a neurotransmitter or neuromodulator
What is another word for receptor types
Receptor isoforms
What are agonists and antagonists
Exogenous ligands that bind to a receptor to produce the same response or block the endogenous ligand from binding
What is upregulation
Increase in cell response by increasing the number of receptors (endocytosis of receptors)
What is downregulation
Decrease in cell response by decreasing the number of receptors (via exocytosis) or altering how the receptors can bind (via phosphorylation)
What is tonic control
Like a switch, relation is either up or down (increase vs decrease, more or less)
What is antagonistic control
Balance between inputs from systems (like the sympathetic and parasympathetic nervous systems)
Is tonic or antagonistic control faster
Antagonistic
