Physiology Chpt 6

Front 1

What are the two types of physiological signals?

Back 1

Chemical and electrical

Front 2

Electrical signals

Back 2

Changes in a cell's membrane potential

Front 3

Chemical signals

Back 3

Molecules secreted by cells into the extracellular fluid. Can act as ligands that bind to proteins to create a response.

Front 4

Target cells

Back 4

RESPOND TO ELECTRICAL OR CHEMICAL SIGNALS

Front 5

4 methods of cell-to-cell communication/ Local communication

Back 5

-gap junctions

-contact dependent signals

-Chemicals diffused through the ECF to act on the target cell(s)

-long distance communication (combination of chemical and electrical signals)

Front 6

Gap junctions

Back 6

-Direct cytoplasmic transfer of electrical and chemical signals between adjacent cells.

-simplest form of communication.

-protein channels that create cytoplasmic bridges.

-ions and small molecules can go through these.

-This is the only way electrical signals can be passed directly through.

Front 7

Contact-Dependent Signals

Back 7

-Surface molecules in the immune system and during growth and development.

-Cell adhesion molecules (CAMs) are used as receptors and can transport signals in both directions by their connections with the cytoskeleton and intracellular enzymes.

Front 8

Paracrine signal

Back 8

Chemical that acts on cells in the immediate vicinity of the cell that secreted it. ie. Histamine

Front 9

autocrine signals

Back 9

chemical signal that acts on the cell that secreted it.

Front 10

What system(s) is long distance communication typically through?

Back 10

Nervous and endocrine

Front 11

Hormones

Back 11

-Endocrine chemical signals released into the blood and are taken all over the body. Only cells with receptors for that hormone can be targets.

-The most common ones in the body are peptides.

Front 12

neurocrine molecules

Back 12

chemicals secreted by neurons.

Front 13

neurotransmitter

Back 13

neurocrine molecule that diffuses across a narrow extracellular space to the target.

Rapid onset effect.

Front 14

neuromodulator

Back 14

neurocrine molecule that acts slower, like a paracrine or autocrine signal.

Front 15

neurohormone

Back 15

neurocrine molecule diffuses into the blood for body distribution. Is part of both the nervous system and the endocrine in a way.

Front 16

Receptor proteins

Back 16

A cell can bind to a particular chemical signal only if it has the right receptor protein to bind to the signal.

Front 17

Signal pathway for receptor proteins:

Back 17

1) Ligand (1st messenger) is the signal molecule and will bind to the protein receptor

2) Ligand-receptor binding activated receptor

3) Receptor activates one or more intracellular signal molecules (2nd messengers)

4) Signal molecule creates a response by modifying existing proteins or synthesizes new proteins

Front 18

Lipophilic signal molecules

Back 18

(non polar)

Enter through simple diffusion and bind to cystolic receptors or nuclear receptors. Typically directs cell to make new mRNA, and new proteins. Can sometimes repress gene activity.

ie. hormones

Front 19

Lipophobic signal molecules

Back 19

(Polar)

Unable to enter through cell membrane, so they stay in the extracellular fluid and bind to the receptor proteins on the cell membrane.

Rapid response time

Front 20

What are the 4 categories of membrane receptors?

Back 20

Receptor channel

G-Protein Coupled Receptor (GPCR)

Receptor-enzyme

Integrin receptor

Front 21

Signal transduction

Back 21

transmission of info from one side of the cell membrane to the other side. Signal from extracellular to intracellular will alter intercellular molecules.

Transducer changes a signal from one form to another

Front 22

What can 2nd messenger molecules do?

Back 22

- Alter gating on ion channels

- Increase intracellular calcium (changes protein function creating a new response)

- Changes enzyme activity (especially protein kinases and protein phosphatases, either phosphorylating or de-phosphorylating proteins, changing shape and creating a response)

Front 23

What is responsible for a cell's response to a signal?

Back 23

Proteins modified by calcium binding and phosphorylation.

Front 24

Protein Kinases

Back 24

Phosphorylate proteins

Front 25

Amplification

Back 25

signal is made larger. One signal molecule turns into multiple second molecules by an amplification enzyme.

Front 26

Receptor Channels

Back 26

Simplest membrane receptor

Most rapid effect. An increase or decrease in the permeability of ions will change the membrane potential almost right away.

Found in nerves and muscles

ie.Acetylcholine-gated monovalent cation channel of skeletal muscle. ACh bings to the ACh receptors and opens the channel. Then Na and K flow through, K leaving the cell and Na coming in (along the electrochemical gradient). This depolarizes the cell leading to muscle contraction.

Front 27

G-Protein Coupled Receptors (GPCR) (1/2)

Back 27

G Protein: 3 part membrane transducer connected to cytoplasmic tail.

Hormones, growth factors, olfactory molecules, visual pigments, and neurotransmitters can attach to G proteins.

Phosphorylating GDP to GTP activated the protein

This receptor can open or close ion channels or alter enzyme activity on the cytoplasmic side of the membrane.

Linked to amplifier enzymes

Front 28

G-Protein Coupled Receptors (GPCR) (2/2)

Back 28

Many lipophobic hormones use GPRC-cAMP pathways.

When this pathway is activated phospholipase C (PLC) converts membrane phospholipids into 2 lipid derived 2nd messengers:

(1)Diaglycerol: DAG. non polar. Remains in lipid portion of mem. Ca activated enzyme associated with cytoplasmic side, used for a cnts 2nd messenger cascade.(2)Inositol triphosphate: IP3. H2O soluble messenger leaves membrane and enters the cytoplasm. Binds to Ca channel on endoplasmic reticulum, letting Ca diffuse out of ER

Front 29

Receptor-Enzyme

Back 29

2 regions:

-Receptor on extracellular side. Catalytic receptors

-enzyme on intracellular side

Sometimes they are part of the same protein and sometimes different proteins.Activated from a ligand binding to receptor

enzymes are either protein kinases or guanylyl cyclase (converts GTP to cyclic GMP [cGMP])

ie.Tyrosine kinase receptor

Front 30

Tyrosine Kinase receptor

Back 30

Receptor-Enzyme process

1) Signal molecule (ligand) binds to the surface receptor

2) Transfers a signal to the Tyrosine Kinase on the cytoplasmic side of the membrane

3) A tyrosine molecule then binds to Tyrosine Kinase and it transfers a phosphate from ATP to the tyrosine molecule.

-This is also how insulin works

Front 31

Integrin receptors

Back 31

Membrane spanning proteins

Attach to the inside of the cell via anchor proteins

Activate intracellular enzymes or alter organization of cytoskeleton.

Catalytic receptors

Front 32

What are the 4 groups of modified proteins due to a cell response?

Back 32

- Motor Proteins

- Enzyme activity

- gene regulation and protein synthesis

- Membrane transport and receptor proteins

Front 33

GPCR-adenyl Cyclase Signal Transduction and Amplification

Back 33

1) Signal molecule binds to GPCR, activating the G-Protein.

2) G-Protein turns on adenylyl cyclase (the amplifier enzyme to create a cascade of proteins)

3) Adenylyl cyclase converts ATP into cyclic AMP (2nd messenger)

4) cAMP activates Protein Kinase A

5) Protein Kinase A phosphorylates other proteins, leading to a cell response.

Front 34

Signal transduction using ion channels

Back 34

1a) some channels may be directly linked to G-Protein Coupled Receptors which create intracellular signal molecules to signal the opening of ion channels. b) Receptor channels open/close in response to a signal molecule binding

2) Change in permeability of K+, Na+, and Cl-

3) Creates and electrical signal

4) Voltage sensitive protein senses the electrical signal

5) Cell response

Front 35

Calcium as a Intracellular signal

Back 35

A) 1)Ca2+ enters the cell via a channel (mechanical, voltage, or chemical gates)

2) Ca levels increase in the cytosol

3) Ca binds to proteins (either Calmodulin or other)

4) Calmodulin alters protein activity. Other binding molecules start exocytosis and movement in the cell

B) 1)Electrical signal causes the release of Ca from intracellular stores

2-4) Same as above

Front 36

Calmodulin

Back 36

alters enzyme or transporter activity, or gating ions

Front 37

What do target responses rely on?

Back 37

Target response rely on TARGET TISSUES. (Whether they have receptors or not and the reaction of the receptor)

ie. Epinephrine can bind to different receptors ultimately dilating or contracting blood vessels. (alpha receptors =constricts, Beta receptors= dilate)

Front 38

Down-regulation

Back 38

decrease in the number of receptor on a cell.

Can be done via:

-Physical removal via endocytosis

-Desensitization: easily reversible. Achieved by binding a chemical modulator to a receptor protein. ie. competitive inhibitor

Front 39

up regulation

Back 39

target cell inserts more receptors into membrane. This is used during development and allows cells to be very responsive to growth factors and other signals.

Front 40

How can cells terminate signal pathways?

Back 40

-ligand can be broken down via enzymes

-removed from the ECF into neighboring cells (neurotransmitters)

-Endocytosis of receptor (ligand and complex)

Front 41

Reflex control pathway

Back 41

Complex information must be transmitted through the body via chemical signals, electrical signals, or both. ie the process of the release of T4 and T3.

Front 42

Cannon's 4 postulates

Back 42

1. The nervous system has a role in preserving the parameters of the internal environment.

2. Some systems of the bode are under tonic control.

3. Some systems of the body are under antagonistic control. (ie. glucagon and insulin)

4.One chemical signal can have different effects in different tissues.

Front 43

What controls long distance pathways?

Back 43

Nervous and endocrine systems

Front 44

Response loops

Back 44

Stimulus--> Sensor/Receptor --> Input (afferent) signal --> Integrating Center (compares input to set point) --> Output (efferent) signal --> target --> response

Front 45

Central receptors

Back 45

In the brain and closely linked to the brain

Front 46

Peripheral receptors

Back 46

elsewhere in body that is away from brain. ie. Skin receptors and internal receptors

Front 47

Threshold

Back 47

All sensors have this minimum stimulus needed to start a reflex response.

Front 48

Why do control systems vary?

Back 48

Specificity, nature of the signal (fast/slow acting), duration of action, and the coding for stimulus intensity (frequency or amount released).

Front 49

Simple endocrine reflex

Back 49

Only has one integrating center, receptor, and hormone

Front 50

Complex neuro-endocrine reflex

Back 50

Multiple receptors, integrating centers, and hormones

Front 51

What do disease and drugs do to pathways?

Back 51

Modulate signal pathways