The Endocrine System Flashcards
1- what is homeostasis?
Maintenance of a dynamic equilibrium within the body
Regulating of variables so that internal states remain stable and relatively constant
Homeostatic mechanisms work to counteract internal changes to the body’s environment
1- what does homeostasis failure lead to?
Disease
1- name the four levels at which homeostasis mechanisms exist. Give examples
Cells (e.g. regulation of calcium concentration on intracellular level)
Tissues (e.g. apoptosis- balance between cell proliferation and cell death)
Organs (e.g. kidney regulates water and ion concentration in blood)
Organisms (e.g. constant body temp)
1- what four things make up a control system?
1- stimulus
2- receptor- detects the stimuli (chemoreceptors, thermoreceptor, nocicereceotors, proprioceotors)
3- control centre- determines set point
4- effector- causes change (e.g. sweat glands, muscle, kidney)
1- one example of a homeostasis control system is ‘body water homeostasis’, explain this
Total body water % is around 50% of total body mass in the average person
This needs to be maintained
Intercellular fluid needs to make up 2/3 of water
Extracellular fluid needs to make up 1/3 of water
Osmoreceptors and baroreceptors react accordingly to osmolality changes
Water-regulating hormone release
Kidneys react- to hormone stimulation and thirst activation
2- define ‘hormone’
Chemicals signals
They are produced in endocrine glands or tissues
They travel in the bloodstream to cause an effect on other tissues
2- what is the endocrine system?
A collection of glands located in different areas of the body that release hormones
2- what other organs and tissues, apart from the endocrine glands, also release hormones?
Heart- ANP, BNP
Liver- IGF1
Stomach- ghrelin
Placenta- placental hormones
Adipose- leptin
Kidney- erythropoietin, renin
2- identify as many if the major endocrine glands as you can
Hypothalamus
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid gland
Thymus
Adrenal gland
Pancreas
Ovary
Testis
2- name the four major mechanisms of communication used by hormones
Autocrine- hormone acts back on cell of origin
Paracrine- hormone carried short distance via interstitial fluid
Endocrine- hormone into bloodstream and carried to distant target cells
Neurocrine- hormone originates in neuron, travels down axon, released into blood, carried to distant target cells
2- name and briefly explain the chemical classes of hormones
Peptide/polypeptide
-Largest group
-short chains of amino acids
-water soluble
Amines
-synthesised from aromatic amino acids
-adrenal medulla hormones- water soluble
-thyroid hormones- lipid soluble
Glycoproteins
-large protein molecules
-made of sub units
-carbohydrate side chain
-all water soluble
Steroids
-all derived from cholesterol
-tissues convert cholesterol into different hormones
All lipid soluble
2- describe transportation of hormones
All hormones travel in blood
Blood travel is carried out in two different ways:
1- travel in blood in simple solution
2- most hormones bind to specific proteins (e,g, thyroid hormones bind to thyroxine-binding globulin protein)
2- what are the three factors that determine hormone levels in blood?
Rate of production-
Synthesis and secretion
Rate of delivery-
Higher blood flow to specific organ means higher hormone delivery
Rate of degradation-
Metabolised and excreted
2- what hormone does the hypothalamus release?
TRH
GHRH
CRH
2- what hormone does the pituitary gland release?
LH
FSH
Prolactin
Oxytocin
2- what hormone does the pineal gland release?
Melatonin
2- what hormone does the thyroid gland release?
Thyroxine
2- what hormone does the parathyroid gland release?
Parathyroid hormones
2- what hormone does the thymus release?
Thymosin
Thymopoetin
Thymulin
2- what hormone does the adrenal gland release?
Adrenaline
2- what hormone does the pancreas release?
Insulin
2- what hormone does the ovary release?
Oestrogen
2- what hormone does the testis release?
Testosterone
3- describe the concept of negative feedback
A way that the body responds in order to REVERSE the direction of change to maintain homeostasis
When conditions change from the set point, it works to return the conditions to this set point
Most common form of feedback
3- describe the concept of positive feedback
Responds in a way to change/push the variable EVEN MORE IN DIRECTION OF CHANGE
Used when the stimulus is promoted, not unwanted
Used in times when we need rapid change
Quite rare
3- give some examples of negative feedback
Body temperature regulation (sweating and shivering)
Blood sugar regulation (high- pancreas releases insulin, low- pancreas sleazes glucagon)
Metabolism (when hungry, metabolism slows down to conserve energy)
3- give some examples of positive feedback
Childbirth (stretching continues using contractions to further promote labour)
Lactation (child feeding stimulates milk production to further promote breast feeding)
4- what term describes the relationship between the hypothalamus and pituitary gland?
Hypothalamic pituitary axis
4- outline what is meant by the hypothalamic pituitary axis
The hypothalamus and pituitary gland form a complex functional unit to serve as the major link between the ENDOCRINE and NERVOUS systems
Neuroendocrine mechanism
Mediates effects if stressors by regulating numerous physiological processes
4- name some processes that are modulated by the hypothalamic pituitary axis
Lactation
Puberty
Body growth
Reproduction
4- describe the function of the posterior pituitary gland
It is physically connected to the hypothalamus
Oxytocin and ADH secreted by hypothalamus, transported down nerve cell axons to the posterior pituitary, stored, released by posterior pituitary, into general blood circulation, acts on target cells and organs
4- describe the function of the anterior pituitary gland
NEUROCRINE
Hormones are synthesised in hypothalamus,
Transported down axons,
Stored in median eminence,
Release into hypophyspheal system,
Target endocrine cells in anterior pituitary
ENDOCRINE
Anterior pituitary has endocrine cells,
They secrete different hormones into the bloodstream to act on distant targets
4- what six type of hormones are produced by the hypothalamus? What do they have direct effect upon?
Six different tropic hormones are produced by the hypothalamus
Direct effect in the release of hormones from the anterior pituitary
4- what two hormones are produced by the hypothalamus to have effect on the posterior pituitary gland and be released from here?
Oxytocin - milk and uterus contractions
Antidiuretic Hormone (ADH) - water volume regulation
4- summarise the HPA in regards to its distinct neurocrine pathways
The hypothalamus has nerve cells which produce hormones, these hormones act via TWO neurocrine pathways
Posterior pituitary- direct effects on targets
Anterior pituitary- indirect effect on targets (hormones secreted into hypophyseal portal system, then they effect endocrine cells)
