Lecture 7 - Cell to Cell Communication

Active transport energy requirement

ATP

Passive transport energy requirement

None

Passive transport flow direction

Down the concentration gradient (high to low)

Active transport flow direction

Against the concentration gradient (low to high)

Does passive transport require assistance

Sometimes

Does active transport require assistance

Always (carrier proteins/pumps

Transport allowing passage of small, non-polar(O2, CO2), water, ions

Passive transport

Transport allowing passage of large molecules, ions(Na+, K+), glucose

Active transport

Physiological signal involving a change in the cell’s membrane potential

Electrical

Physiological signal involving molecules secreted into extracellular fluid

Chemical

Simplest way of transferring info between cells

Cytoplasmic bridges between cells

Provide channels in gap junctions

Connexins

Cell communication method good for ions and small molecules found in nearly all cell types

Gap junctions

Multi-cell contact dependent communication important during growth and development

Cell-to-cell contact

Signal that acts in immediate vicinity of secreted signal

Paracrine signal

Signal that acts on cell that secreted it

Autocrine signal

Signals that diffuse through interstitial fluid

Paracrine and autocrine

Is histamine paracrine or autocrine

Paracrine

Type of cells that store histamine

Immune

Released in response to allergic reactions, injury, or infection

Histamine

Histamine causes _______ to dilate, and capillaries to become more _____

Blood vessels, permeable

Cells that detect injury and release histamine

Mast cells

Communication that can be both chemical or electrical

Long distance communication

Cells that use hormones, which are chemical signals secreted into blood and distributed

Endocrine cells

Signals used by the nervous system

Chemical and electrical

Diffuse across narrow extracellular space with quick effect

Neurotransmitters

Released into blood and affect cells further away

Neurohormones

What is required for a cell to respond to a signal

Target cell receptor proteins

Molecule or atom that binds to a receptor

Ligand

What happens after the signal molecule (ligand) binds to a receptor

The ligand-receptor complex is activated

What happens after the the ligand-receptor complex is activated

The now activated receptor activates intracellular molecules

What does it mean for the signalling pathway once the intracellular molecules are activated by the receptor

The cellular response is activated

Compete for the binding site with histamines to lessen a response

Antihistamine

Can a ligand bond to multiple receptors

Yes

Constricts intestinal blood vessels, dilates blood vessels in skeletal muscle

Epinephrine

How does epinephrine constrict intestinal blood vessels, and dilate blood vessels in skeletal muscle (generally)

Multiple receptors

Is adrenaline (involved in fight or flight), a neurotransmitter or a hormone

Both

Does a response depend on the receptor or the ligand

Receptor

Epinephrine a-receptor function

Constricts intestinal blood vessels

Epinephrine b-receptor function

Dilates skeletal muscle blood vessels

Can multiple ligands with similar structures bind to the same receptor

Yes

Both bind to adrenergic receptors, and a-cells and b-cells

Epinephrine and norepinephrine

What happens when a ligand activates a receptor

Response agonist activation

What happens when a ligand occupies a binding site

Response agonist prevention

Drugs that occupy receptors and activate them

Agonists

Drugs that occupy receptors but do not activate them, and block receptor activation by agonists

Antagonists

Mimic or block hormones

Hormone disruptor

Do hormone mimics increase or decrease cellular response

Increase

Do hormone blockers increase or decrease cellular response

Decrease

Cellular signalling systems are responsible for maintaining

Homeostasis

2 control systems involved in long distance reflex pathways

Nervous and endocrine

Number of steps in a homeostatic reflex pathways

7

Disturbance starting a reflex pathway

Stimulus

Multicellular receptor responding to environmental changes

Varied sensor and integrating centre depending on the reflex

Input signal

Why is the input signal not found in endocrine signals

The stimulus acts directly on endocrine cells

Interpret and initiate a response in a reflex pathway

Integrating center

Integrating center location in neural reflexes

CNS

Electrical and chemical signals sent by neurons (nervous) or hormones (endocrine) that travel in blood

Output signal

Cells or tissues that carry out the response

Target

Muscles, glands, and adipose tissue are examples of what reflex pathway step

Output (neural)

Cells having a proper receptor in the endocrine system are an example of what reflex pathway step

Output

Cellular response in a target cell

Response

Overall change in an organism

Systemic response

Dim light causes the parasympathetic nervous system to transmit a signal, causing the pupils to

Dilate

Bright light causes the parasympathetic nervous system to transmit a signal, causing the pupils to

Constrict

Hormone released due to low blood concentration of calcium

Parathyroid hormone

Parathyroid hormone stimulates the release of _____ into the blood

Calcium