CHAPTER 6 - communication, integration, homeostasis

name the 7 kinds of proteins of the body

1. membrane transporters

2. enzymes

3. receptors

4. regulatory proteins

5. binding proteins

6. signal molecules

7. immunoglobulins

what are the 2 physiological signals in cell to cell communication

1. electrical signals - change cell membrane potential

2. chemical signals - molecules secreted by cells and received by target cells (most common)

3 local communications in cell to cell communication

1. gap junctions

2. contact-dependent

3. autocrine/paracrine

3 long distance communications in cell to cell communication

1. endocrine (hormones from glands)

2. neurotransmitters (electrical, action potentials)

3. neurohormones (released into bloodstream in response to nerve signals)

what are gap junctions

form direct cytoplasmis connections between adjacent cells

eg. heart muscle, smooth muscle

what are desmosomes in the cardiac muscle

• type of cell junction

• strong proteins that surround sarcomeres and bind neighbouring sarcomeres

• allow force to be transferred

what are gap junctions in the cardiac muscle

• provide electrical connection

• electrical signals are rapidly transmitted via these protein pores providing the basis for synchronous contraction

what are autocrine/ paracrine cells

autocrine - act on same cells that secreted them

paracrine - secreted by one cell and diffuse to adjacent cells

eg. histamine, cytokines, eicosanoids

what are contact dependent signals

require interaction between membrane molecules on two cells, occurs in system during growth and development

what 2 systems look after long distance signalling

endocrine and nervous

where are hormones released from

endocrine glands/ endocrine cells

where are neurocrines released from

neurons; neurotransmitter, neuromodulator, neurohormone

what are cytokines

peptides, both local and long distance,

short proteins that help in signalling

3 neurocrine molecules

1. neurotransmitters

2. neuromodulators

3. neurohormones

define hormones

chemical messengers produced by endocrine glands that are released into the bloodstream and travel to target organs or tissues

what are neurotransmitters

• chemical messengers that transmit signals across a synapse from one neuron to another target neuron, muscle cell, or gland cell

• released from synaptic vesicles in the presynaptic neuron into the synaptic cleft, where they bind to specific receptors on the postsynaptic membrane.

what are neurohormones

chemicals released by neurons into the blood for action at distant targets

what are lipophobic signal molecules

• dont want to diffuse through cell membrane

• bind receptors on the cell membrane

what are lipophilic signal molecules

• diffuse through cell membrane

• usually bind cytosolic receptors or nuclear receptors

what is a cascade signal transduction

conversion of substrate to product

what is signal amplification

allows a small amount of signal to have a large effect

what are the 4 categories of membrane transporters

1. receptor - channel: ligand binding opens and closes channel

2. g protein receptor: opens an ion channel or alters enzyme activity

3. receptor - enzyme: activates an intracellular enzyme

4. integrin receptor: alters enzymes or cytoskeleton

what membrane receptor is most commonly used for signal transduction

G protein coupled receptors

what is a receptor-channel

ligand binding opens or closes the channel

what is a G protein-coupled receptor

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

which is a faster reaction: gated signal transduction or cascade

gated

what is a second messenger

a substance whose release within a cell is promoted by a hormone and which brings about a response by the cell.

name the 5 steps of lipophobic hormones during signal transduction (cAMP system)

1. signal molecule binds to G protein coupled receptor, activating G protein

2. G protein activates adenylyl cyclase

3. adenylyl cyclase converts ATP to cAMP ( secondary signal)

4. cAMP activated protein kinase A

5. protein kinase A amplifies leading to a cellular response

name the 5 steps of lipid- derived second messengers during signal transduction

1. signal molecule activates receptor, activating G protein

2. G protein acivates phospholipase

3. phospholipase converts membrane phospholipids into diacylglycerol (DAG) - remains in membrane and IP3 - diffuses into the cytoplasm

4. DAG activates protein kinase C which phosphorylates proteins

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

name 6 secondary messenger molecules

1. cAMP

2. calcium

3. DAG

4. IP3

5. Kinase A

6. cGMP

what is paracrine signalling

acts on cells nearby

what is autocrine signalling

acts on the same cell that produced the hormone

what is an agonist ligand

a ligand that still has some affinity and can activate the receptor but not as much as the primary ligand

what is an antagonist ligand

a ligand that blocks the receptor activity

eg. CO2 block O2 receptors in cells

alpha receptors have a high affinity to norepinephrine or epinephrine

norepinephrine

beta receptors have a high affinity to norepinephrine or epinephrine

epinephrine

what is tonic control

continuous regulation of a physiological function by a single control mechanism or signal, which can be increased or decreased as needed.

• signal always present, changes in intensity

what is antagonistic control

Antagonistic control involves the regulation of a physiological function by opposing signals or mechanisms.

define up regulation

Upregulation refers to the process by which a cell increases the number or sensitivity of its receptors or signaling molecules in response to a particular stimulus.

define down regulation

Downregulation is the process by which a cell decreases the number or sensitivity of its receptors or signaling molecules in response to prolonged exposure to a stimulus.

define pathway termination

Pathway termination refers to the processes that deactivate or stop a signaling pathway once the appropriate cellular response has been achieved or the stimulus is no longer present