Physiology Unit #2 Exam (chapter 6)

What forms can physiological signals or commands take?

Electrical signals and Chemical signals

What are electrical signals?

Changes in cell membrane potential, transmitted from one cell to another.

What causes a cell to change its membrane potential?

ions and ion channels.

What are chemical signals?

“commands used to change cell function”

Molecules secreted by cells into the ECF, travel a long or short distance, and bind to another cell.

What is the active process of secretion called?

Exocytosis

What do we call the cells that create and release these signals to communicate information?

-Signal generators

• They control the function of other cells in the body with their signal.

• They are typically neurons, endocrine cells, or immune cells.

What do we call the cells that receive or reposed to these signals?

-Target cells or effector cells

• They could be any cell in the body that preforms an action (ex; skeletal muscle cells, cardiac muscle cells, glandular cells, etc.)

What is the fastest form of cell to cell communication?

Gap junctions.

• There is a physical connection between the cytosol of adjacent cells through complexes of membrane-spanning proteins called connexions.

• This can be a transfer of chemical and or electrical signals between the connected cells.

What are the muscle cells in your heart interconnected with?

Gap junctions

Why is the heart interconnected with gap junctions?

• Electrical signals can spread seamlessly through all cells in an entire heart chamber (all will depolarize simultaneously).

• This causes all those cardiac muscle cells to contract in unison and pump blood.

What is contact-dependent signaling?

• It requires interaction between signal molecules on one cell’s plasma membrane to bind to protein receptor on the other cell.

• Transfers info in both directions (both cells will change function in a specific way).

In what body system cells do we see contact-dependent cells a lot?

Immune System.

• One will place a fragment of a pathogen on its cell membrane and stimulate others to “seek and destroy” the same target by touching other immune cells. (think direct contact informs cells what pathogen they are trying to seek and destroy).

Neurons, endocrine cells, and immune cells secrete signal molecules by ——— to affect the function of their target cell.

Exocytosis

What are autocrine signals?

Act on the same cell that secreted them.

(signal generator is the target cell)

What are paracrine signals?

Are secreted by one cell and diffuse to adjacent cell.

(the cell talks to neighboring cells)

What are hormones and how are they part of long distance cell-to-cell communication?

1. They are produced ahead to time and stored in vesicles until needed.

2. Are relapsed by specialized endocrine cells/glands under specific circumstances.

3. Travel through the blood to distant target cells.

If a cell doesn’t have a receptor for a hormone what will happen? If it does have a receptor what will happen?

If it doesn’t have a receptor there will be no repose. If the cell does have a receptor the hormone will bind and cause a response.

How are cytokines similar to hormones?

Both are released into the blood.

How are cytokines different from hormones?

1. They are made on demand.

2. They are not released from specialized cells. Cytokines can be produced in and secreted from any nucleated cell in body.

What form of long distance signal molecules are faster than hormones?

Neurocrines, neurotransmitter, and neuromodulators

Where are neurocrines, neurotransmitter, and neuromodulators released from?

They are released from the axon terminal, cross the synaptic cleft, and bind directly to receptors on the target cells.

What are neurotransmitters (NT)?

Have a very fast effect on the target cells function

ex: acetylcholine can cause skeletal muscle cells to contract in just a few hundred milliseconds.

What are neuromodulators (NM)?

Lead to long-term changes in target cell function.

ex: changes in brain serotonin levels are associated with mood regulation, but these changes can take several minutes to occur.

What are neurohormones?

• They are released into the blood similarly to hormones.

• It affects target cell function longer than a neurotransmitter or neuromodulator (many minutes to an hour).

• It leaves the blood and binds to receptors on its target cell to change its function in specific ways.

• (ex: epinephrine is released in fight or flight)

Review: What are long range signal molecules released by neurons into the blood?

Neurohormones.

Review: What are fast acting signal molecules released from one neuron directly onto the surface of its target cell?

Neurotransmitters.

Review: What signal molecules can be produced by nearly every cell of the body?

Cytokines.

Review: What are the long range signal molecules that are produced by a specialized glandular cells and are released into the blood?

Hormones.

Review: Neurotransmitters and neuromodulators are examples of ————— single molecules excuse they bind to target cells and are nearby.

Paracrine

What are the two different things that receptors could mean?

• Receptors can be protein molecules on the plasma membrane or inside cells.

• Can also be a cluster of specialized cells placed strategically around the body.

What are central receptors?

• Are in or close to the brain

• eyes (vision), ears (hearing, equilibrium), nose (smell), tongue (taste), central chemo-, osmo-, and thermoreceptors.

What are peripheral receptors?

• Lie outside the brain

• chemoreceptors, osmorecptors, thermorecepetrs, baroreceptors, proprioceptors, other mechanoreceptors.

Where do non-polar signal molecules bind to receptors?

In the cytosol or in the nucleus

Non-polar (lipophiliic) signal molecules can pass through the plasma membrane by ————-?

simple diffusion

Non-polar signal molecules lead to ————— changes in cell function, since they typically alter protein synthesis (gene expression)

slower

What are some examples of non polar signal molecules?

Steroid hormones, eicsanoids, gas signal molecules (ex nitric oxide)

Where do polar signal molecules have to bind to?

They must bind to receptor proteins on the plasma membrane.

Can polar signal molecules pass through the plasma membrane?

No they cannot pass through the plasma membrane.

For polar signal molecule complex can stimulate rapid changes in cell functions by doing what?

By altering the function of specific intracellular protein workers.

What are some examples of polar signal molecules?

Peptide or amine hormones, neurotransmitters, neurohormones, neuromodulators, and cytokines.

Steps that the polar signal molecules must take in order to get a response:

1. signal molecule binds to:

2. membrane receptor protein which activates:

3. intracellular signal molecules which alters:

4. target proteins to create

5. a response

Communication pathway using polar signal molecules (skeletal muscle) steps to reach response:

1. signal molcule = ach

2. binds to nicotinic receptors

3. action potential on muscle cell membrane releases intracellular chemical (calcium ion)

4. target proteins actin and myosin interact

5. response: the muscle cells contract (shortens), pulls on skeleton, and you move

What are receipts-channels?

Ligand binding opens or closes the channel.

What are G-protein coupled receptors?

Ligand-binding to a G protein-coupled receptor opens an ion channel or alters enzyme activity.

What is a receptor-enzyme?

• catalytic receptor

• ligand binding to a receptor enzyme activates an intracellular enzyme.

What is a integrin receptor?

Ligand binding to intern receptor alters enzymes or the cytoskeleton.

What happens after a signal molecules binds to its receptor?

Signal transduction.

What is signal transduction?

Information carried by the signal molecules is “translated” into a new, intracellular message that triggers a change in protein function and target cell function overall.

Receptors act as transducers. What does this mean?

-They translate extracellular signals into intracellular messages, which leads to a cell reposes (change in function).

-Each receptor type has a unique method of transduction.

What are the three main ways to trigger a cell response?

1. Modulation of intracellular protein workers by phosphorylation.

2. Modulation of intracellular calcium-binding proteins.

3. Modulation of ion channels in the plasma membrane to change membrane potential.

What is tyrosine kinase an example of?

It’s an example of a receptor enzyme.

How does tyrosine kinase work?

1. ligand binds to a receptor on the extracellular side.

2. that event induces a structural change in that receptor

3. the reception directly activates the intracellular kinase enzyme.

4. those phosphoralyated protein workers will then change the target cells function.

What do other receptor enzymes use to alter target cell function?

Amplification

When does amplification occur?

Occurs when a membrane receptor directly activates an amplifier enzyme (AE) inside the target ell.

• the command carrier by the first messenger (hormone, neurotransmitter, etc) is amplified into many intracellular second messenger molecules.

What is adenylyl cyclase?

• Amplifier enzyme that converts lots of ATP to lots of cyclic adenosine monophosphate (cAMP).

What is guanylyl cyclase?

• Amplifier enzyme: that converts lots of GTP (guanosine triphosphate) into lots of cyclic guanosine monophosphate (cGMP).

What are cGMP and cAMP examples of?

second messangers.

How are cGMP and cAMP second messengers?

• they turn up the “volume” and can spread a message very rapidly through the cell.

• they don’t mediate a change in cell function directly, but rather activate or inhibit target proteins that then actually carry out the change in cell function.

What is a a g-protein coupled receptor (GPCR)?

Made up of a receptor protein embedded in the plasma membrane linked to a G-protein inside the cell.

Why a g-proteins called g-proteins?

They get there name because they bind guanosine nucleotides, such as guanine diphosphate (GDP) or guanosine triphosphate (GTP).

When the GPCR is activated by its signal molecule, the G-protein physically detaches and will either…

1. Modulate amplifier enzyme activity on the intracellular side of the membrane OR

2. Open an ion channel in the membrane

What are GPCRs typically associated with?

1. Adenylyl cyclase: which produces cAMP as a second messenger.

2. Phospholipase C: which produces IP3 and DAG as second messengers.

What are the 5 steps in the adenylyl cyclase -cAMP pathway?

1. Signal molecule binds to G protein-coupled receptor (GPCR), which activates the G protein.

2. G protein turns on adenylyl cyclase, an amplifier enzyme.

3. Adenylyl cyclase converts ATP to cyclic cAMP.

4. cAMP activates protein kinase A.

5. Protein kinase A phosphoralyates other proteins, leading ultimately to cellular response.

What are the 5 steps of the GPCR: phospholipase C pathway?

1. signal molecule activates receptor and associated g-protein.

2. g-protein activates phospholipase C (PLC), an amplifier enzyme.

3. PLC converts membrane phospholipids into diacylglycerol (DAG), which remains in the membrane, and IP3, which diffuses into the cytoplasm.

4. DAG activates protein kinase C (PKC), which phosphorylates proteins.

5. IP3 causes release of Ca2+ from organelles, creating a Ca2+ signal.

What is PLC?

phospholipase C

What is DAG?

diacylglycerol

What is PKC?

protein kinase C

What is IP3?

Inositol triphosphate

What is ER?

endoplasmic reticulum

What are receptor channels?

• A sub type of the chemically-gated channels.

• The fastest way that an external signal molecule can change a cells function (milliseconds)

• Only a few ions need to cross the membrane to change a cells membrane poetical.

Signal molecules are structurally-specific to the binding site on their receptor. Therefore these ——- are subject to competition from molecular “mimics”

ligands.

What are agonists?

• They mimic the primary ligand and stimulate the same change in cell function.

• Can be used therapeutically when abnormally-low cell- to cell communication is causing pathophysiology.

• ex partisans disease.

What are antagonists?

• They are sometimes called blockers, they physically block ligands from binding to their receptors, causing less or no change in cell function.

• can be used therapeutically when abnormally high-cell to cell communication is cause pathophysiology.

• ex ex beta blockers decrease epipinerphrine which reduces high blood pressure.

/What is up-regulation?

Increase in the number of receptors through protein synthesis to make target cells MORE sensitive to a specific signal molecule.

What is down regulation?

Decrease in the number of receptors by pulling them into the cell via endocytosis and destroying them using enzymes in a lysosome.

This makes target cells LESS sensitive to a specific signal molecule.

One explanation for drug tolerance.

What is desensitization?

A different receptor variant can be made that has a low affinity for its signal molecule.

Perhaps by altering how mRNA is processed or by altering post-translational modification.

Another explanation for drug tolerance.

What’s true about multiple receptorsfod signal molecules?

• Those different receipts are strategically placed around the body, at different target cells.

• This allows for one signal molecule to cue different responses in different areas of the body (each receptor is linked to a different intracellular cascade.

Signal molecules are often parts of the ——- and —— pathways of feedback loops.

afferent and efferent

When are receptors mentioned?

When you define and effector

What are the two typical ways integrating centers control their effectors?

• tonic control pathway

• antagonistic control pathway

For a tonic control system, how many signal molecules are used to control the effector cell?

One

The amount of that one signal molecule (its intensity) is adjusted up or down as needed:

High amounts of the single molecule produce one response.

Low amounts of the signal molecule produced the opposite effect.

For an antagonistic control systems how man efferent pathways are the organs are controlled by?

2 efferent pathways

How do antagonist control systems work?

• one signal molecule increases activity o the effector cells.

• the other single molecule decreases activity of the effector cells.