1. Chemical Coordination

2. 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]

3. 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.

4. 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

5. The glands of the endocrine system
Pituitary
Hypothalamus
Thyroid (and parathyroid)
Pineal
Thymus
Adrenal
Pancreas
Ovary
Testis

6. 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]

7. Targeting the signal
If the hormone is transported around the whole body then how does it act on specific target organs?

8. 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

9. 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

10. 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!

11. 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