Chapter 6: Communication, Integration, and Homeostasis Flashcards
what are the two types of physiological signals for cell to cell communication?
- electrical
* chemical
what are the methods of cell to cell communication?
- local communication
2. long distance communication
what does local communication consist of?
- gap junctions
- contact-dependent signals
- paracrine signals
what does long distance communication consist of?
- passing along neurons
* chemical messengers transported through the blood
- cytoplasmic link between adjacent cells
- involve connexin proteins
- can function in synchronizing communication
gap junctions
where are gap junctions found?
- heart muscle
- smooth muscle
- some glands
- some neurons in -the brain
- A surface molecule on one cell binds a membrane protein on another.
- cell adhesion molecules (CAM’s)
- Play a role in the immune system as well as growth and development
contact-dependent signals
Chemicals that communicate with neighboring cells (must be close enough that once secreted into ECF it can reach the target cell by simple diffusion
paracrine signals
what are paracrine examples?
- Eicosanoids lipid derived signal molecules
- Cytokines peptides function in coordinating the body’s defense against infections
what do autocrine signals act on?
act on the cell that secreted it
what are hormones secreted by?
endocrine system
chemicals secreted into the interstitial fluid, where they diffuse into the blood and are distributed all over the body
hormones
which cells can respond to hormones?
Only cells possessing receptors specific for the hormone can respond (target cells)
this system is a combination of chemical and electrical signals
nervous system
how do the chemical and electrical signals of the nervous system work?
- Electrical signals travel down neurons
- Chemical signals secreted by neurons are neurocrine molecules
diffuse across narrow space to target cell (rapid onset effect)
neurotransmitter
signal acts as a paracrine signal
neuromodulator
chemicals
released by neurons into the blood
for action at distant targets
neurohormone
what do signal pathways include?
- ligand (1st messenger) binding receptor protein
- receptor activation
- activation of intracellular signal molecules
- response of cell by protein modification or synthesis
transmit their signals by binding to target cell receptors located either on the plasma membrane, in the cytosol, or in the nucleus.
chemical messengers
what is the location of binding dependent on?
- dependent on the properties of the molecule
- lipophilic molecules
- lipophobic molecules
receptors are cytosolic or nuclear (slower response)
lipophilic molecules
receptors on the cell membrane (rapid response)
lipophobic molecules
what does intracellular signal receptors involve?
- receptor in cytosol
- receptor in nucleus
- lipophilic signal molecules
- diffuse through cell membrane
- bind to cytosolic or nuclear receptor
- triggers slower responses related to changes in gene activity
lipophilic signal molecules
what does cell membrane receptors involve?
- extracellular signal molecule binds to cell membrane receptor
- binding triggers rapid cellular responses
occurs when extracellular signal molecules activate receptors that alter intracellular molecules to create a response
signal transduction
what are the steps of signal transduction?
- first messenger binds receptor
- Activated receptor turns on associated protein which starts intracellular cascade of secondary messengers
- Second messenger molecules
- The last second messenger acts on the intracellular target to create a response
what proteins do activated receptors turn on?
- activated protein kinases
- amplifier enzymes that create intracellular second messengers
what do second messenger molecules do?
- open and close ion channels
- increase intracellular calcium
- change enzyme activity (kinases & phosphatases)
what do signal transduction pathways form?
a cascade
occurs when the receptor-ligand complex activates an amplifier enzyme
signal amplification
allows a small amount of
signal to have a large effect
signal amplification
what are some second messengers?
- cAMP
- cGMP
- IP3
- DAG
- ca2+
what are the nucleotide second messengers?
- cAMP
- cGMP
what are the lipid derived second messengers?
- IP3
- DAG
what is the ion second messenger?
Ca2+
- activates protein kinases (PKA)
- binds to ion channels
- phosphorylates proteins
- alters channel opening
- made from ATP
cAMP
- made from GTP
- activates protein kinases (PKG)
- phosphorylates proteins
cGMP
- made from membrane phospholipids
- releases Ca2+ from intracellular stores
- alters enzyme activity
IP3
- made from membrane phospholipids
- activates protein kinase C
- phosphorylates proteins
DAG
- binds to calmodulin & other proteins
- alters enzyme activity; exocytosis, muscle contraction, cytoskeleton movement, channel opening
Ca2+
what are the four major types of membrane receptors?
- receptor channels (ligand gated)
- G protein coupled receptors
- receptor enzymes
- integrin receptor
which membrane receptors are catalytic receptors?
- receptor-enzyme
- integrin receptor
Ligand binding
opens or closes
the channel
receptor channel
Ligand binding to a G protein–
coupled receptor opens an ion
channel or alters enzyme activity
G protein–coupled receptor
Ligand binding to a
receptor-enzyme activates
an intracellular enzyme
Receptor-enzyme
Ligand binding to integrin
receptors alters enzymes
or the cytoskeleton
integrin-receptor
initiate the most rapid intracellular responses.
receptor channels
what are the kind of receptor-channels?
- simple ligand-gated ion channels
- non-receptor linked ion channels
- voltage gated channels
- mechanically gated channels
- non-receptor linked ion channels
open and close due to membrane potential
Voltage-gated channels
open with pressure or stretch of membrane
mechanically gated channels
Large membrane protein with a transducer molecule (G protein) attached to the cytoplasmic tail
G protein-coupled receptors (GPCRs)
what are the ligands that bind with GPCRs?
- neurotransmitters
- hormones
- growth factors
- olfactory molecules
- visual pigments
what happens when GPCRs bind guanosine nuecleotides?
- inactive when GDP bound
- active when GTP bound
opens ion channels
active G protein
what alters the enzyme activity of the cytoplasmic side of the cell?
- GPCR-cAMP
- GPCR-phospholipase C
receptor region on ECF side and enzyme region ICF side of the same protein
receptor-enzymes
what can the enzyme portion be of receptor-enzymes?
- kinases (tyrosine kinase)
- guanylyl cyclase
the amplifier enzyme that produces cyclic GMP from GTP
guanylyl cyclase
where is the enzyme portion of receptor enzymes?
on the intracellular side
What is an example of a receptor enzyme on the intracellular side?
JAK kinase
what is the process of receptor enzymes?
- signal molecule binds to surface receptor
- tyrosine kinase o cytoplasmic side
- phosphorylated protein
- membrane spanning proteins
- transfer information into the cell
integrin (cell-matrix junction) receptors
what can integrins do on the extracellular side of the cell?
these proteins can bind to proteins of the extracellular matrix or to ligand (ex. antibodies)
what can integrins do inside the cell?
activate enzymes or can change the organization of the cytoskeleton
what are integrin receptors involved in?
- wound repair
- cell adhesion
- blood clotting
- cell movement during development
what does the magnitude of a target cell’s response depend on?
- the affinity of the receptor for the messenger
- the number of receptors
- the messenger’s concentration
what does specificity of receptors allow for?
generally allows bind by only one messenger or a class of messengers
what is an example of the specificity of receptors?
- *Norepinephrine and epinephrine are both specific for adrenergic receptors)
- α isoform higher affinity for norepinephrine
- β isoform higher affinity for epinephrine
ligands that bind to receptors and produce a biological response
agonist
- ligands that bind to receptors but do not produce a response
- blocks receptor activity
antagonist
- an opioid agonist used in pain treatment
- binds to opioid receptors in spinal cord and brain to block pain
morphine
an opioid antagonist that binds opioid receptors with more than 10 times the affinity of morphine, reversing the effects on users
naloxone
a decrease in the number of receptors, when cells are exposed to high messenger concentrations for prolonged period
down-regulation
how is down regulation achieved?
- remove through endocytosis
- Desensitize through binding of chemical modulator
- drug tolerance
an increase in the number of receptors compared to “normal” conditions, when cells are exposed to low messenger concentrations for prolonged period
up-regulation
what can go wrong with signal transduction?
- genetically inherited abnormal receptors
- toxins affecting signal pathways
- shortens half life of receptpr
- results in congenital diabetes insipidus
vasopressin receptor (X-linked defect)
- blocks enzyme activity of G proteins
- cell keeps making cAMP
- results in ions being secreted into lumen of intestine, causing massive diarrhea
cholera toxin
- father of american physiology
* described properties of homeostatic control systems
walter cannon
what did walter mention say about homeostatic control systems?
- nervous regulation of internal environment
- tonic control
- antagonistic control
- one chemical signal can have different effects in different tissues
what does nervous regulation of internal environment regulate?
- regulates parameters
- blood volume
- blood osmolarity
- blood pressure
- body temperature
- the degree to which something is turned on or off, like volume on a radio
- the signal is always present but changes in intensity
tonic control
*factors that have opposing effects
*Insulin (decreases), glucagon (increases)
*uses different signals to
send a parameter in opposite directions
antagonistic control
as we see with paracrine and autocrine signals are isolated changes in tissues and cells
local control
what are the reflex pathways?
- local control
- long distance control
uses complicated reflex control pathways and uses both nervous and endocrine systems
long distance control
- is a stimulus (carbon dioxide concentration, blood pressure, light)
- sensor have a threshold stimulus to set response in motion
- afferent signal
input
what are the different input signals?
- If neural input signal is electrical and chemical transmitted by a sensory neuron.
- If endocrine there is no input pathway and the stimulus acts directly on the endocrine cell
what are the two categories of receptors?
- cell membrane or intracellular receptor proteins
- sensors: specialized cells or structures that convert various stimuli into electrical signals
what are the two categories of sensors/specialized cells?
- central receptors
- peripheral receptors
comparison of signal to set point
integration center
where is the neural reflexes integration center?
in the CNS
where is the endocrine reflexes integration center?
endocrine cell
- efferent signal
- electrical and/or chemical
- travels to target (effector) tissue or cell
output
What are some neural targets?
muscle, exocrine and endocrine glands, adipose tissue
What are some endocrine targets?
cells with the appropriate receptor for the hormone
what are the types of responses?
- cellular response
- tissue or organ response
- systemic response
smooth muscle contraction after excited by neurotransmitter
cellular response
decreases blood flow through blood vesse
tissue or organ response
increase blood pressure
systemic response
what make up physiological reflex pathways?
nervous and endocrine systems
how do the nervous and endocrine systems work together?
work as a continuum rather than as discrete control systems
what is the specificity of a neural reflex?
each neuron terminates on a single target cell or on a limited number of adjacent target cells
what is the nature of the signal of a neural reflex?
electrical signal that passes through neuron, then chemical neurotransmitters that carry the signal from cell to cell
what is the speed of a neural reflex?
very rapid
what is the duration of action of a neural reflex?
usually very shot; responses of longer duration are mediated by neuromodulators
what is the coding for stimulus intensity of a neural reflex?
each signal is identical in strength; stimulus intensity is correlated with increased frequency of signaling
what is the specificity for endocrine reflexes?
- most cells of the body are exposed to a hormone
* the response depends on which cells have receptors for the hormone
what is the nature of the signal for endocrine reflexes?
chemical signals secreted in the blood for distribution throughout the body
what is the speed on the endocrine reflex?
distribution of the signal and onset of action are much slower than in neural responses
what is the duration of action for endocrine reflexes?
responses usually last longer than neural responses
what is the coding for stimulus intensity for endocrine reflexes?
stimulus intensity is correlated with amount of hormone secreted
hormones get secreted by endocrine glands into the bloodstream and……..
travel to all cells but elicit responses only in cells with specific receptors for that hormone
an increase in receptor number on the surface of a cell membrane…….
makes the cell more sensitive to the signal molecules
which of the following is the correct sequence for G protein coupled signal transduction?
ligand –> GPCR –> G protein –> adenylyl cyclase –> protein kinase –> tissue response
ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) that prevents inflammation by inhibiting…….
cyclooxygenase (COX)
Norepinephrine and epinephrine both have specificity for alpha adrenergic receptors but norepinephrine has a higher affinity for the receptor. Epinephrine is there _______ of norepinephrine
an agonist and a competitor
