Chemical Coordination
Chemicals released and active in their immediate vicinity Chemical mediators Chemicals released and active in their immediate vicinity Histamine Chemical released by: Basophil white cells; Mast cells (in connective and mucus tissues); Trigger for release: Antigens; Effect: Histamine receptors in smooth muscle leads to dilation of small arteries & arterioles; Increases capillary permeability to white cells and proteins; Redness, swelling and itching. [Note: histamine has a number of other roles including as a neurotransmitter]
Chemical mediators Prostaglandins A number of fatty acid derived compounds with various effects Released by: most cells; Triggered by: tissue damage; Effect: In response to injury dilation of arterioles; increased capillary permeability; increased sensitivity to pain; Other roles: relaxation of smooth muscle in the gut; promotion of muscle contraction during birth.
Two types of gland Endocrine gland Exocrine glands Contain cells that produce a hormone and release it straight into the blood They are ductless Exocrine glands They produce a substance which is not directly released into the blood They have a duct which carries the secretion to another place
The glands of the endocrine system Pituitary Hypothalamus Thyroid (and parathyroid) Pineal Thymus Adrenal Pancreas Ovary Testis
Endocrine Glands - hormones A hormone from an endocrine cell is secreted into the blood, which carries it to its target cell. [Exocrine glands secrete products into a duct e.g. saliva, sweat]
Targeting the signal If the hormone is transported around the whole body then how does it act on specific target organs?
Targeting the signal Each hormone is different from all the others Some cells have complementary receptors on their plasma membrane (target cells) The hormone binds to the receptor and the cell then responds to the signal This allows hormones to travel around the body without affecting other cells
Types of hormones There are two types of hormones; Protein and peptide hormones Are not soluble in the membrane so DO NOT enter the cell Steroid hormones Can pass through the membrane and enter the cell Act upon the DNA in the nucleus
Task Discuss the ways in which the endocrine system is similar to, and different to, the nervous system. Construct a table to compare the two systems. 10 minutes!
Hormones Vs Nerves Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Transmission relatively slow Transmission very rapid Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Hormonal system Nervous system Chemical communication Nervous communication Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Transmission relatively slow Transmission very rapid Hormones travel throughout body but only target responds Nerve impulse specifically targeted Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Transmission relatively slow Transmission very rapid Hormones travel throughout body but only target responds Nerve impulse specifically targeted Response is widespread Response is localised Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Transmission relatively slow Transmission very rapid Hormones travel throughout body but only target responds Nerve impulse specifically targeted Response is widespread Response is localised Response slow Response rapid Response longer lasting Response short lived Effect may be permanent & irreversible Effect is temporary Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Transmission relatively slow Transmission very rapid Hormones travel throughout body but only target responds Nerve impulse specifically targeted Response is widespread Response is localised Response slow Response rapid Response longer lasting Response short lived Hormonal system Nervous system Chemical communication Nervous communication Transmission by blood Transmission by neurones Transmission relatively slow Transmission very rapid Hormones travel throughout body but only target responds Nerve impulse specifically targeted Response is widespread Response is localised Response slow Response rapid