Download 1 Chemical Coordination

Chemical Coordination
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
– 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
Pineal
Thyroid (and
parathyroid)
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;
1. Protein and peptide hormones
•
Are not soluble in the membrane so DO
NOT enter the cell
2. 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
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