Chemical Signalling (HL IB Biology)

Neurotransmitters are chemicals released by neurones at synapses which transmit signals to other neurones, muscle cells, or glands. Hormones are another category of signalling chemicals. 

State the names of two other functional categories of signalling chemicals in animals.

Amino acids provide the majority of neurotransmission in the nervous system. One such amino acid is glycine. Glycine receptors are ligand-gated ion channels present on postsynaptic membranes.

Suggest how the activation of glycine receptors may affect the postsynaptic membrane potential.

Compare and contrast neurotransmitters and hormones as chemical signalling molecules. 

The hormone progesterone keeps oestradiol production within a normal range. Unopposed oestrogenic action is a condition in which oestradiol acts without the counteracting influence of progesterone. Unopposed oestrogenic action can lead to the development of endometrial cancer in both humans and rats.

Activation of ligand molecules (AHR ligands) can lead to anti-oestrogenic actions. AHR ligands are specific to AHR receptors; the interaction results in the metabolism of oestradiol and may reduce the development of endometrial cancer. 

Suggest the role AHR ligand molecules have in activating an anti-oestrogenic action in endometrium cells.  

Progesterone and oestradiol are steroid hormones that can act as ligands and are responsible for the expression of many genes within a cell.

Describe the action of oestradiol as a ligand responsible for regulating expression of genes that control the menstrual cycle.

Describe the effects of progesterone on the body.