Communication and Hormones (Hormonal and Nervous Communication (Steroid…
Communication and Hormones
The endocrine system uses hormones, which travel around the bloodstream, and trigger a response when they bind with target cells or target tissues.
Some examples of characteristics of life include: homeostasis, organisation, metabolism, growth, adaptation, response to stimuli and reproduction.
Homeostasis - the process of maintaining a constant internal environment despite external changes which may be taking place.
Multicellular organisms require communication as they are differentiated and have this division of labour, in order to coordinate functions of the different systems. It provides a link between the receptor, detecting the stimulus and the effector being triggered to carry out an appropriate response.
Negative feedback - operates by detecting the external change, communicating with other cells, and the reversing change (the response).
Endocrines and Exocrines
The duct glands, called exocrine glands, do not release hormones, but instead, secrete materials along a duct directly to the target location, for example, salivary glands secreting saliva which flows into the mouth.
There are two types of glands in our bodes (one has ducts and one doesn't).
Endocrine systems rely on blood circulation to transfer their signals. Molecules called hormones are released into the bloodstream directly by endocrine glands.
Adrenaline is a protein hormone, meaning that it can't enter the cell itself. It can still cause an effect. There is an adrenaline receptor on target cells, which is shaped in a way which is complementary to the hormone molecule itself. Every receptor for adrenaline has n enzyme associated with it on the inner surface membrane, called adenyl cyclase.
The adrenal medulla is the central part of the gland, The cells there manufacture and release adrenaline in response to stress such as pain or shock. The effects of th hormone are widespread as there are receptors for the hormones on many tissues around the body.
The hormone adrenaline increases heart rate, increases breathing rate, causes arterial contraction, causes pupil dilation, etc.
The adrenal cortex uses cholesterol to produce steroid hormones, which have a variety of roles in the body. For example, aldosterone helps to maintain the concentrations of sodium and potassium in the blood, and cortisol helps to control the metabolism of carbohydrates and proteins in the liver.
Hormonal and Nervous Communication
Steroid hormones can pass through the cell surface membrane and enter the cell directly to produce a direct effect on the DNA in the nucleus, whereas the phospholipid bilayer is not permeable to proteins and so protein hormones do not enter the cell.
In nervous communication an electrical impulse is carried by neurones. This signal is initiated in receptors/CNS.
In hormonal communication the effect is slower but lasts longer. One hormone can affect several systems.
In hormonal communication chemicals are carried around the blood by hormones. These signals are secreted by endocrine glands.
In nervous communication there is a much quicker response but a much shorter effect. One nervous signal triggers one specific, targeted response.
Cells receiving a specific (protein) hormone must have a specific complementary receptor on the surface membrane which allows the hormone to bind to the membrane. A hormone will bind to the receptor site of any cell with the correct receptor. Such cells are called target cells, grouped together to form a tissue for the hormone.