KIN 270 - Lecture - Communication and Homeostasis

What is Homeostasis?

The automatic process that we use to keep a stable, balanced internal environment while outside conditions change

What are times that we purposely take ourselves out of Homeostasis?

Ice Baths - Sauna - Exercise

Brainstorm ways humans communicate

Body Language - Talking - Writing/Texting - Sign Language - Touch (Thermal/Pressure) Short Distance and Long Distance

Cell to Cell Communication: What are the different ways of local communication of cells?

Gap Junctions - Contact-Dependent Signals - Local Diffusion of signalling molecules to proximal cells

What are the different ways for physiological signals in cells?

Electrical and Chemical

Physiological Signals: What is the Electrical Signal?

Changes in the membrane potential of a cell - Analogy: Text Message

Physiological Signals: What is a chemical signal?

Molecules secreted by cells into extracellular fluid - responsible for most communication within the body - Analogy: Discussion question and the dicussion and response)

What are Gap Junctions at the Local Level?

Different kinds of channels through which ions, ATP, cyclic AMP and amino acids can flow through. Proteins called “connexins” form the channels that can open and close.

What are contact-dependent transportation at the local level?

Lock and Key method (Direct Command) - signalling molecule inidicates/influences that only that cell can come into contact with it

An example of where gap junctions would occur?

Heart - Digestive System - Smooth Muscle

An example where contact dependent would occur?

Sperm and Egg - Over Growth - Injury (Swelling)

What is Autocrine Signals at the local level?

The same cell produces the same that causes it to occur Ex. Internal Thoughts - Body Language - Cancer Cells

What are paracrine signals at the local level?

The cell itself is a part of a change reaction of the signal Ex. Blood Sugar Balance

What is Long distance communication?

It is mainly chemical signals

What are the different chemical signals? (2)

The ones released from the endocrine system are hormones - the ones that are released by nerve cells are called neurocrines

What are the different Neurocrine signals?

Diffuse across a synapse - neurotransmitters / diffuse by paracrine signalling - neuromodulators / diffuse into the vascular system - neurohormones

What are chemical signals released by the endocrine system through the bloodstream? and why do they take longer?

Hormones - they are slower due to being in the bloodstream and it causes a prolonged effect

What are cytokines?

They control cell development, differentiation, and immune response. - All nucleated cells synthesize and secrete cytokines in response to stimuli - They can also be inhibitory in nature

How are Cytokines different from hormones?

Because they are not produced and stored by endocrine tissue

Where are cytokines produced and where do they effect?

They are produced in one cell, and their effect is systemic (all tissues of the body are effected)

Are cytokines efficient or inefficient?

Very Efficient

What is the cell membrane composed of, and what does it contain?

It is composed of a phospholipid bilayer and has many transmembrane proteins (like channel proteins that serve as ion channels)

Why do some cells respond to a chemical signal while others do not?

Because different cells have different channel proteins and different tasks (confirm)

Signalling Pathways: What does a ligand depend on to bind to?

Whether it is lipophilic (friends with everybody - easy to pass through) or lipophobic (ask to come in - carrier protein)

What are the three categories that we cover of receptors and pathways for lipophobic ligands?

Receptor Ion Channels - Receptor Enzyme - G protein-coupled receptors

What are voltage-gated channels?

amino acids in the structure of the protein that are sensitive to charge and cause the pore (channel) to open to the selected ion - Ionotropic Receptors

When do voltage gated channels open?

They open when the transmembrane voltage changes around them

How do mechanically gated channels open?

they open when a mechanical change happens in the surrounding tissue, such as pressure or touch - the channel is physically opened

Do thermorecpetors work the same way as voltage-gated or mechanically gated channels?

Mechanically Gated Channels - when the local tissue temp changes, the protein reacts by physically opening the channel

What are leakage channels and what are they used for?

They are needed to move ions across membranes randomly - We need to maintain a negative interior and a positive exterior Ex. Red Blood Cells (Oxygen and CO2)

What are Receptor Enzymes?

They cause a cascade response - they have an extracellular receptor region and an intracellular enzyme-producing region - the enzymes are either protein kinases or guanylyl cyclase

What are the 2 receptor enzymes ligands?

Tyrosine Kinase Receptor - G Protein Coupled Receptors (GPCRS)

What does Tyrosine Kinase Recptor transfer?

Transfers a phosphate group from ATP to tyrosine (an amino acid) of a protein

What are the steps of the tyrosine kinase receptor?

Signals molecule binds to surface receptor - Tyrosine kinase on cytoplasmic side - and then develops Phosphorylated Protein

What are examples of Tyrosine Kinase Receptors?

Insulin - Platelet Growth Factors - Metabolic Activations

What are G Protein Coupled Receptors (GPCRS)

They get their name from binding guanosine nucleotides - Inactive (GDP), Active (GTP)

What are the 5 steps of GPCR-adenylyl cyclase signal transduction and amplification?

1. Signal Molecule binds to a 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 AMP (cAMP)

4. cAMP activates protein kinase A

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

There are G protein pathways? what are they and what do they do?

G (sub) S - Amplifier

G (sub) I - Inhibitory

G (sub) q - Alternate Pathway

What are the 5 steps of the GPCR-phospholipase G signal transduction (Alternate Pathway)?

1. Signal molecule activates receptor and associated G protein

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

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

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

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

What are the three gases that we talked about that are ephemeral signal molecules?

Nitric Oxide (NO) - Carbon Monoxide (CO) - Hydrogen Sulphide (H2S)

What is Nitric Oxide?

A short acting paracrine and autocrine signaling molcule produces by endothelial cells - produced by the enzyme Nitic oxide synthase that acts on arginine in presence of O2 - diffuses into smooth muscle and cause vasodilation - activated guanylyl cyclase second messenger systems and can act as a neuromodulator and neurotransmitter

What is Carbon Monoxide ?

Activated guanylyl cylase and cGMP

Targets smooth muscle and neural tissue

Hydrogen Sulphide (H2S)

Targets cardiovascular system to relax blood vessels - Garlic is a major dietary source of precursors

How can one chemical have multiple effects on various targets?

Receptor Saturation - Specificity - Competition

What are agonists and antagonists with Ligands?

Primary Mover - Agonist

Opposite of primary mover - Antagonist