Chapter 4 - Chemical Messengers Flashcards
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?
Why is the pituitary referred to as the ‘master gland’ ?
The pituitary gland is referred to as the ‘master gland because many pituitary hormones regulate the activity of other endocrine glands.
What do the hormones released by the anterior lobe do?
They regulate a great range of the bodys activities.
What are the hormones produced by the Anterior lobe?
- Follicle Stimulating (FSH)
- Luteinising hormone (LH)
- Growth Hormone (GH)
- Thyroid Stimulating hormone (TSH)
- Adenocorticotropic hormone (ACTH)
- Prolactin (PRL)
What hormones do the Posterior lobe produce?
- Oxytocin (OT)
- Antidiuretic hormone (ADH)
What is the target organ and main effects of the hormone Follicle Stimulating?
- Ovaries (females): Growth follicles
- Testis (Males): Production of sperm
What is the target organ and main effects of the hormone Lutenising hormone (LH)?
- Ovaries: ovulation and maintenance of corpus luteum
- Testis: secretion of testosterone
What is the target organ and main effects of the hormone Growth hormone (GH)?
- All cells: Growth and protein synthesis
What is the target organ and main effects of the hormone Thryoid stimulating hormone (TSH)?
- Thyroid gland: secretion of hormones from the thyroid
What is the target organ and main effects of the hormone Adrenocorticotropic hormone (ACTH)?
- Adrenal cortex: Secretion of hormones from the adrenal cortex
What is the target organ and main effects of the hormone Antidiuretic hormone (ADH) ?
- Kidneys: Reabsorption of water
What is the target organ and main effects of the hormone Oxytocin (OT) ?
- Uterus: contractions of uterus during childbirth
- Mammary glands: Release of milk
What is the target organ and main effects of the hormone Prolactin (PRL)?
- Mammary glands: Milk production
For the gland Thyroid, name its hormone produced, its target cells and its main effects.
Hormone produced: Thyroxine
Targeted cells: Most
Main effects: Increases metabolic rate and therefore oxygen consumption and heat production
For the gland Parathyroids, name its hormone produced, its target cells and its main effects.
Hormone produced: Parathyroid hormone
Targeted cells: Bones, Kidneys
Main effects: Increases level of calcium in blood
For the gland Thymus, name its hormone produced, its target cells and its main effects.
Hormone produced: Thymosis
Targeted cells: T lymphocytes
Main effects: Stimulates development and maturation of T lymphocytes
For the gland Adrenal Cortex, name its hormone produced, its target cells and its main effects.
Hormone produced: Aldosterone
Targeted cells: Kidney
Main effects: Inreases reabsorption od sodium ions and excretion of potassium ions
Hormone produced: Cortisol
Targeted cells: Most
Main effects: Promotes normal metabolism; helps the body deal with stress; promotes repair of damaged tissue
For the gland Adrenal Medulla, name its hormone produced, its target cells and its main effects.
Hormone produced: Adrenaline and Nonadrenaline
Targeted cells: Most tissues
Main effects: Prepares the body for fight-or-flight responses; reinforces the effects of the sympathetic nervous system
For the gland Pancreas, name its hormone produced, its target cells and its main effects.
Hormone produced: Insulin
Targeted cells: Most
Main effects: Stimulates uptake of glucose; lowers blood glucose level
Hormone produced: Glucagon
Targeted cells: Liver and fat storage tissues
Main effects: Stimulates breakdown of glycogen and fat; increases blood glucose level
For the gland Testes, name its hormone produced, its target cells and its main effects.
Hormone produced: Androgens
Targeted cells: Many Tissues
Main effects: stimulate sperm production; growth of skeleton and muscles and male sexual characteristics
For the gland Ovaries, name its hormone produced, its target cells and its main effects.
Hormone produced: Oestrogens
Targeted cells: Many Tissues
Main effects: Stimulate the development of female characteristics; regulate the menstrual cycle
Hormone produced: Progesterone
Targeted cells: Uterus and mammary glands
Main effects: Regulates menstural cycle and pregnancy; prepares mammary glands for milk secretion
