Cell to Cell Communication and Receptors

Define juxtacrine communication

Type of direct communication that relies on contact-dependent signalling (cells need to be in physical contact through a connexon)

Define indirect communication

Cell communication that does not require contact between communicating cells (requires specific messenger molecules)

How are cells connected in juxtacrine communication

Connected by two connexons (2 connexons for every gap junction)

1 connexon = 6 connexins

Describe function of connexons

Connexons allow ions, glucose and amino acids to transfer across cells

Very fast communication using electrical synapses (cells in tissue can act synchronously)

What cells use juxtacrine communication

Heart, brain and smooth muscle cells

Name five types of indirect cell to cell communication

Endocrine, autocrine, paracrine, neurocrine and neurotransmission

Describe endocrine communication

Endocrine cell (part of gland) produces a hormone that is transported to the target cell via the bloodstream

Describe neurocrine communication

Neurocrine cell (neuron) produces a hormone that is transported to the target cell via the bloodstream

Describe paracrine communication

Paracrine cell secretes a paracrine molecule into the interstitial fluid between cells and acts on target cells nearby

Describe autocrine communication

Autocrine cell secretes an autocrine molecule into the interstitial fluid and then acts on the same cell that produced the molecule

Describe neurotransmission

Neurons produce a neurotransmitter that is released via exocytosis in the synapse between neurons and acts on target cells by binding to its receptor

Describe general functions of hormones

• chemical composition and interstitial fluid

• metabolism and energy balance

• contraction of smooth/cardiac muscle

• glandular secretions

• immune system

• control growth and development

• reproductive system

• establishment of circadian rhythms

Name and describe two types of hormones

Water soluble - cannot travel directly through cell membrane (lipid bilayer)

Lipid soluble - can travel directly through lipid bilayer

Describe secretion of water soluble hormones

Secreted through exocytosis into the bloodstream and binds to a receptor on the target cell to cause a response

Describe secretion of lipid soluble hormones

Secreted through exocytosis into the bloodstream (requires a protein to carry it as lipid soluble = hydrophobic) and travels directly through cell membrane into the cell to produce a response

Define synergistic hormones

Enhance the action of another hormone

Define antagonistic hormones

Oppose the action of another hormone

How are hormone secretions regulated

Regulated by signals from nervous system, chemical changes in blood/cells and other hormones

What determines target cell response (after hormone binds to receptor/enters membrane)

Based on hormone concentration in the blood, number of receptors on target cell and influences from other hormones

Name three types of receptors

Ligand, ionotropic and metabotropic

Describe ligand receptors

Specific proteins that function when a specific molecule binds to the receptor

Once bound, a signal is sent into the cell (metabotropic) or open a channel for molecules to pass through (ionotropic)

Where are ligand receptors located

Present on cell membrane and will eventually diffuse away or can be intracellular and induce an effect in a cell

Describe ionotropic receptors

Channel that opens when messenger molecule binds to it which allows a specific ion/s to enter

Positive ion = activation of cell

Negative ion = inhibition of cell (relaxes cell)

Describe metabotropic receptors

External and internal receptor segment - messenger molecule binds to external receptor, activating a protein attached to the internal receptor (G protein)

The type of G protein released produces the activation/inhibition of the cell