Mod 14: Cell Signaling

What is necessary for appropriate growth and development?

communication b/t cells

what is necessary for the body to adapt to changes in the environment?

communication b/t cells

The nervous system correlates with … molecules.

neurotransmitter

The endocrine system correlates with … molecules.

hormone

the immune system equates to … molecules

cytokine

How far can messages travel?

short or long distances

Messages traveling from short distances is …

cell to cell

Messages traveling from long distances is …

through the bloodstream

What is the result message transmission?

1. activation of receptors that open ion channels

2. enzymes activated

   1. initiating production of other communication molecules to produce desired effect

Signaling is a … process.

dyanmic

What does signaling result from?

multiple complex interactions within an organism

What are positive feedback loops?

increased output of a signaling molecule

What is increased out of signaling molecule triggered by? (positive feedback loops)

activation of receptors by that same molecule

What are positive feedback loops associated with?

amplifying a process

What is an example of a positive feedback loop?

uterine muscle contractions during childbirth

What is a negative feedback loop?

activation of a receptor by signaling molecule

What do negative feedback loops result in?

decreased output of a molecule

What are negative feedback loops associated with?

decreasing a process

what is an example of a negative feedback loop?

blood sugar regulation

What do endocrine glands secrete?

hormones

What do hormones signal?

specific actions by target cell types

How are hormones usually transmitted?

via the circulatory system

What is an example of endocrine signaling?

pituitary gland releases:

• adrenocorticotropic hormone

• thyroid stimulating hormone

• growth hormone

These affect activities at the adrenal cortex, thyroid gland, and in muscles/bones

What is paracrine signaling?

cells that are near each other communicate by releasing various chemical messengers

what is an example of paracrine signaling?

synaptic signaling:

• neurotransmitters are released from one neuron into a synapse, where the messengers diffuses across to the receiving cell

paracrine signaling

What is synaptic signaling sometimes called?

neurocrine signaling

What is autocrine signaling?

the chemical messenger acts on the cell that secreted it

What concept is autocrine signaling involved with?

negative and positive feedback loops

What has been implicated in tumor growth (cancer growth)?

autocrine signaling

What does a typical chemical messenger system include?

1. messenger molecule secreted from a cell in response to a stimulus

2. the messenger diffused or is transported to a target cell

3. a specific molecular target in/on the target cell bind the messenger

4. binding of the messenger elicits a response

5. the signal ceases or is terminated

What is a receptor?

a specific molecular target in/on the target cell

What is a messenger?

a molecule secreted from a specific cell in response to a stimulus

The specificity of the response in a chemical messaging system is determined by …

the type of receptor it acts on, and its location

Each receptor binds only …

one specific messenger

What do receptors tend to do to cellular process?

activate or inhibit them

What do target cells carry?

very specific receptors

What do target cell’s receptors make them?

uniquely capable of responding to chemical messengers

How many chemical messengers does the nervous system secrete?

2

What are the chemical messengers that the nervous system secretes?

1. neuropeptides

2. neurotransmitters

What are neurotransmitters also called?

biogenic amines

What are the size of neurotransmitters?

small

What do neurotransmitters contain chemically?

nitrogen

True or false. neurotransmitters are hydrophobic.

false. they are hydrophillic

Many neurotransmitters are …

amino acids or derived from them

What are common neurotransmitters?

dopa, dopamine, levo, epi

What amino acid is dopa, epi, levo, and dopamine derived from?

tyrosine

tyrosine

Dopa

dopamine

norepi

epi

GABA

Which neurotransmitters are catecholamines?

1. epi

1. norepi

2. dopamine

Which neurotransmitters are amino acids?

1. glutamate

2. GABA

3. glycine

Which neurotransmitters are neuropeptides?

endorphins and substance P

Which neurotransmitter is a gaseous molecule?

nitric oxide

Function of GABA

main inhibitory transmitter (brain)

Which class of drugs bind to GABA receptors?

1. benzos

2. barbs

3. anesthetics

4. hypnotics

Functions of endorphins

analgesia, euphoria

Which class of drugs bind to endorphin receptors?

opioids

What is the function of nitric oxide?

smooth muscle dilation and immune response

which drugs bind to nitric oxide receptors?

sildenafil, nitroglycerin

The endocrine system utilizes …

hormones secreted by endocrine cells

Which hormones are polypeptide hormones?

1. insulin

2. pituitary hormones

3. angiotensin

What are examples of steroidal hormones?

1. glucocorticoids

2. mineralocorticoids

3. estrogen

4. cortisol

What are mineralocorticoids derived from?

cholesterol

True or false. Steroidal hormones are lipophillic.

true

Which chemical messengers does the immune system use?

cytokines

Cytokines are considered …

small molecules

What are the 3 cytokine molecules?

1. interleukins

2. tumor necrosis factors

3. interferons

What do cytokines do to other cells?

alter their behavior in the immune system

How do cytokines alter cell’s behavior?

by activating transcription of genes for proteins involved in the immune response

What are eicosanoids?

a class of lipophilic molecule produced by cells in response to injury

What are the eicosanoid molecules?

1. prostanglandin (prostacyclin)

2. thromboxane

3. leukotriene

What are the eicosanoid molecules derived from?

arachidonic acid

What is arachidonic acid derived from?

the cell membrane

What kind of fat is arachidonic acid?

a fatty acid

Messengers intended to reach intracellular receptors must be …

hydrophobic - to diffuse through the plasma membrane

Which messengers are hydrophobic and can get through the cell membrane?

eicosanoids and steroidal hormones

Which messengers cannot cross the cell membrane by themselves?

polar molecules such as:

• polypeptides hormones

• cytokines

• catecholamines

What are the majority of intracellular receptors for?

gene-specific transcription factors

What are gene-specific transcription factors?

proteins that bind to a specific site on DNA to regulate the rate of transcription of a gene (regulating production of mRNA)

How do the lipophilic signaling molecules get through the membrane?

diffusion or use a transporter

(steroidal hormones and thyroid hormones do this)

What do lipophilic signaling molecules do once they get through the cell membrane?

bind to the transcription factor → binds to and alters expression of DNA

(steroidal hormones and thyroid hormones do this)

What are the 2 thyroid hormones?

T3 and T4

How does thyroid hormone get inside the cell?

using a transporter

What does thyroid hormone do once inside the cell?

bind with thyroid hormones receptors (TR)

What do thyroid hormone receptors attract?

coactivators that encourage transcription of a bunch of genes

What are ion-channel receptors considered?

inotropic receptors

What chemical messenger binds to ion-channel receptors?

ligands (produce a conformational change once bound that opens and closes the channel)

What is a classic example of ion-channel receptors?

nicotinic-acetylcholine receptor

What happens at the nicotinic acetylcholine receptor?

an action potential in a motor neuron elicits dumping of vesicles that contain acetylcholine into the synaptic cleft - neuromuscular junction

Which molecules use ion-channel receptors?

• small-molecule neurotransmitters

• some neuropeptides

in the nervous system, what happens to voltage mediated nerve impulses?

they can be rapidly disseminated to other neurons, which carry the voltage-based message on

what is a kinase?

an enzyme that functions to phosphorylates something (adding a phosphate)

What does phosphorylation usually do to a receptor?

Activates it

What are kinase-activated receptors do?

activate another protein or group of proteins that act as signal transducer proteins

What domain does the tyrosine kinase receptor have?

enzymatic

What is a tyrosine enzymatic domain also called?

a tyrosine kinase domain