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66 Cards in this Set

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gap junctions
chemical messengers
All cell in the body use ____ ________ and ________ _________ to communicate with one another
connexins
Gap junctions link adjacent cells and are formed by plasma membrane proteins called _________.
connexons
Connexins form __________.
connexons
These ________ form channels that allow ions and small molecules to pass directly fro one cell to another.
couples
The movement of ions through gap junctions electrically _______ the cells, such the electrical signals in one cell are directly transmitted to the neighboring cells.
gap junctions
___ _______ are also found in some glands and btwn some neurons in the brain and retina, where they function in communication.
metabolically
The movement of small molecules through gap junctions __________ couples the cells, such that one cll can provide necessary nutrients to reach certain bone cells.
Paracrines
Autocrines
Cytokines
Neurotransmitters
Hormones
Neurohormones
What are the 6 functional classifications of chemical messengers?
Paracrines
Have local (tissue) effects only.

Ex. histamines
Autocrines
Local effect on the SAME cell that secretes it.
Cytokines
Most commonly released by WBCs as part of the immune response to pathogens

Usually act locally on other WBCs, but may travel via the bloodstream to distant targets.

It's recruting other WBCs to attack pathogens

become sensitized to pathogens
Neurotransmitters
released by neurons at their axons

Act locally on another neuron.
Hormones
released by endocrine gland cells into the bloodstream, carried to target cells.
Neurohormones
Messengers released by neurosecretory cells at their axons. Carried by the BLOODSTREAM to target cell.

Target cells are NOT neurons.
If they are lipophilic or lipophobic.
How are chemical messengers classified? (2)
Lipophilic
May be lipid soluble

Receptors usually inside the target cell.
lipophobic
May be water soluble

Receptors usually part of the cell membrane.
AA
Amines
Peptides
Steroids
Eicosanoids
What are the 5 chemical classifications of messengers?
Amino Acids
Act as a messenger in the ner. sys.

Lipophobic
Ex. neurotransmitters
Amines
derived from amino acids
Lipophobic
Ex. dopamine, seratonin, NE are neurotransmitters.
Ex. E and NE are hormones.
Peptides
multiple AAs bonded together. Length of chain is variable (2-100)

Lipophobic
Ex. many neurotransmitters, hormones, all cytokines.
Steroids
derived from cholesterol
Lipophilic
Eicosanoids
derived from fatty acids
Lipophilic
Act as paracrine messengers
Signal transduction mechanisms
Mechanisms that allow a messenger molecule to act on target cells to change their function.
Messenger binds to receptors on or in the target cell. The receptors then change the activity of enzymes in the cells, changing cell function.
Properties of receptors
1. show specificity - react only with certain molecules
2. Many types of receptors on or in 1 cell.
3. The more interactions btwn messengers and receptors the greater the effect.
messenger concentration
# of receptors present (they change)
receptor affinity (how strong)
Interactions effected by :
(3)
intercellular receptor function
Messenger must be lipophilic
STEROIDS or EICOSANOIDS
Effects on target cells are slow, but it lasts a long time.
They control protein synthesis which is a slow process.
Why are intercellular receptors' effects slow on target cells?
Membrane receptor function
Messenger must be lipophobic

Receptors are part of the cell membrane.

Have 3 categories of receptors (Channel-linked, Enzyme-linked, G-protein linked)
membrane receptors
Channel-linked
Enzyme-linked
G-protein linked
Channel-linked receptors
Acts as a receptor and a channel
Involved in ion movement across cell membrane.
A gated channel
When receptor interacts w/messenger the channel will open.
Will change cell function
All INTERNAL changes in cell
Enzyme-linked receptors
Receptor act as both a receptor and an intracellular enzyme
Enzyme function is inactive unless a messenger molecule is attached.
G-protein linked receptors
Receptor is linked to a group of proteins found in the cell membrane.

The second messenger molecule may be CA++ or cAMP.

Messenger moleucle acting on the receptor activates the _ ________ which in turn act on another protein found in the cell membrane.
Long distance communication
Utilizes nervous & endocrine systems

Neurons can be over 1 meter in length

used for rapid communication (signal speed up to 100 meter/sec.

Endocrine system secretes hormones often control protein synthesis which is a slow process and it takes time to reach the target cells.
Effects can be long lasting
receptor
A target cell has certain proteins that specifically recognize and bind the messenger.
Paracrines
A chemical secreted by a cell that acts on cells in the immediate vicinity.
Neurotransmitters
chemical released into the interstitial fluid from nervous system cells called neurons.

Released from a specialized protion of the neuron called the axon terminal, which is very close to the target cell.
Presynaptic neuron
The neuron which conducts an action potential toward a synapse.
Postsynaptic neuron
The neuron which receives the signal at a synapse.
Hormones
are chemicals released from endocrine glands into the interstitial fluid, where they can diffuse with the blood.

Travels in blood to get to its target cell.

Bloodstream distributes these to all cells of body, BUT cell only have specific receptors for specific _________.
Insulin
a hormone secreted by the pancreas and acts on target cells throughout the body to regulate energy metabolism.
Cytokines
interferons
interleukins
Plasma membrane
What is the location of receptors on target cells of A.A.s?
Plasma membrane
What is the location of receptors on target cells of Amines?
Plasma membrane
What is the location of receptors on target cells of peptide/proteins?
cytosol
What is the location of receptors on target cells of steroids?
cytosol
What is the location of receptors on target cells of eicosanoids?
neurotransmitters
What is the functional classification of AAs?
Paracrines
Autocrines
Neurotransmitters
Hormones
Neurohormones
What are the functional classification of amines?
Paracrines
Autocrines
Neurotransmitters
Hormones
Neurohormones
Cytokines
What are the functional classification of peptides/proteins?
hormones
What is the functional classification of steroids?
Paracrines
What is the functional classification of eicosanoids?
A.A. messengers
glutamate
aspertate
glycine
GABA
Eicosanoid messengers
prostaglandins
leukotrienes
thromoboxanes
Catecholamine
A type of organic compound that contains a benzene ring structure and an amine group. Dopamine, norepinephrine epinephrine and are _____________.
transmitters
Dopamine are NE are primarily _________.
hormone
E is primarily a __________.
Amino acid synthesis
neurotransmitters must be synthesized in the neuron.
Glycolysis
Pyruvic acid turns into Aceytl CoA
Krebs cycle
neurotransmitters are then transported into vesicles where they are stored until they are released by exocytosis.
Amines
derived from A.A.s
Peptide & protein synthesis
Ribosome attached to rough E.R. is where translation occurs. Polypeptide is formed inside the lumen of rough E.R. (prepropeptide)

In lumen of e.r., proteolytic enzymes cleave off A.A.s from prepropeptide, now called propeptide.

In smooth e.r. the propeptide is packaged into transport vesicle.

Vesicle is transported to golgi apparatus.

Golgi apparatus packages propeptide in secretory vesiclefor storage until release is triggered. More A.A.s are cleaved off in golgi apparatus now called a _______.
steroid synthesis
All _______ are capable of crossing the plasma membrane because they are membrane-permeant, _______ cannot be stored prior to release and instead diffuse out of the cell into the interstitial fluid as soon as they are synthesized.

Are synthesized on demand and released immediately.
Eicosanoid synthesis
Phospholipase A2 catalyzes the conversion of a membrane phospholipid to arachinodonic acid, the precursor for all eicosanoids. Arachidonic acid is converted into _________ via 2 ways:
1. the cyclooxygenase-dependent pathway leads to the production of prostaglandins, prostacyclins, and thromboxanes
2. lipoxygenase-dependent pathway leads to the production of leukotrienes.
half-life
the time it take for half of the hormone in the blood to be degradaded.
Carrier proteins
Messengers can be transported in the nlood either in dissolved form or bound to _______ ________.
hydrophilic
To be transported in dissolved form, the messenger must be a _________ messenger.
albumin
carrier protein that is NOT specific and can transport many different hormones.