Chapter 4 - Chemical Messengers Flashcards
(44 cards)
Homeostasis is…
the maintenance of a constant internal environment
What are the three things that homeostasis ensures?
- contains the optimum concentration of nutrients, ions, gases and water
- constant temperature
- maintain the optimum pressure
What is steady state?
Anothe name for homeostasis
What must the body do to maintain homeostasis?
To maintain homeostasis the body must be able to both sense the changes in the internal and external environment and compensate for those changes.
Whatis a feedback system?
A feedback system is a circular situation in which the body responds to change or stimulus with the response altering the origional stimulus.
What is a negative feedback system?
A negative feedback system is a system which brings about a change opposite to, or reduces the effect of, the original stimulus
What are the five stages of a negativefeedback system?
- Stimulus
- Receptor
- Modulator
- Effector
- Feedback
What two systems control homeostatic mechanisms?
- The Endocrine system
- The Nervous system
The endocrine system…
…secrete chemical messengers, or homones, into the blood
The nervous system…
…sends electrical messages to the appropriate organs so that the change is counteracted
Name and describe two glands in the body. Give examples.
- Exocrine gland: sweat glands, mucous glands, salivery glands
- Endocrine glands: Pancreas, Testis, Ovaries
What is a hormone and how is it transported?
A hormone is a chemical secreated by an endocrine gland and affects the functioning of a cell or organ often carried in the blood.
It is transported throughout the body in the blood.
Cells can communicate through…
secreting chemicals that diffuse adjacent cells
How do hormones change the functioning of a cell and what can they change?
Hormones change the functioning of a cell by changing the type, activities or quantities of proteins produced.
Hormones may:
- Activate certain genes
- Change the shape
- Change the rate of production
What is enzyme amplification?
Enzyme amplification is a series of chamical reactions in which the product of one step is an enzyme that produces an even greater number of product molecules at the nest step; in turn this results in an even greater amount of the product.
What happens once the hormone has produced the required effect?
It must be turned off. This is done by breaking down the hormone, some breakdown in target cells but most breakdown in the liver and kidneys.
They are then excreted either in the bile or in the urine.
What can cause the body to function abnormally?
Over secretion or under secretion
How are hormonal secretions regulated?
Hormonal secretion is regulated by negative feedback systems.
The hypothalamus can secrete…
Releasing factors: stimulate the release of a hormone
Inhibiting factors: which slow down the secretion of a hormone.
What does the hypothalamus regulate?
The hypothalamus regulates the basic functions of the body
- body temperature
- water balance
- heart rate
The functions of the hypothalamus is carried out by which gland?
Pituitary gland
What joins the pituitary gland and the hypothalamus?
The infundibulum
Name and describe the two lobes which the Pituitary consists of.
- Anterior lobe: Has no nerves connected to the hypothalamus but is connected by a complex network of blood vessels
- Posterior lobe: is not a true gland because it does not secrete substances. It is joined to the hypothalamus by nerve fibres.
What is the target organ and main effects of the hormone Prolactin?
