Human endocrine system Flashcards
What is the endocrine system responsible for?
Chemical coordination
Maintaining healthy functioning of the body and its metabolic activities
What does the endocrine system consist of?
ductless glands called endocrine glands
What do endocrine glands secrete?
useful substances called hormones directly into the blood
How is a hormone transported? Also, where is it transported to?
carried by the bloodstream to its target tissues or organs
What do hormones do at target tissues or organs?
They regulate the metabolic reactions
What do hormones play a role in maintaining?
homeostasis (maintaining a constant internal environment)
Give some examples of endocrine glands
hypothalamus pituitary gland thyroid gland pancreas adrenal glands gonads
Does every endocrine gland produce the same hormones?
No
What, in essence, are hormones?
chemical messengers
What can over- or under secretion of hormones lead to?
A number of disorders
What is hypoactivity?
The under-secretion of a hormone
What is hyperactivity?
The over-secretion of a hormone
What kind of hormone does the hypothalamus secrete?
ADH (anti-diuretic hormone)
What hormones does the pituitary gland secrete?
STH (growth hormone) TSH FSH LH Prolactin
What hormones does the thyroid gland secrete?
Just thyroxin
What does the pancreas use to secrete its hormones?
islets of Langerhans
What hormones does the pancreas secrete through the islets of Langerhans?
glucagon
insulin
What hormones does the adrenal gland secrete?
adrenalin
aldosterone
What hormones does the ovary secrete?
oestrogen
Progesterone
What hormones does the testis secrete?
Testosterone
Where is the pituitary gland?
attached to the hypothalamus
in a small bony cavity beneath the brain
Where is the pancreas?
Just above the adrenal gland
Where is the adrenal gland?
Right near (almost on) the kidneys
What are exocrine glands?
glands that have ducts that carry secretions to specific locations
What does vascular mean?
richly supplied with blood vessels
Why is the pancreas unusual?
It behaves like an endocrine gland and an exocrine gland
The pancreas behaves as an endocrine gland. In what way does it also behave like an exocrine gland?
It secretes pancreatic juice through a duct that leads into the digestive system
What is vascular - an endocrine gland or an exocrine gland?
An endocrine gland
What is considered to be the ‘master endocrine gland’ (the chemical coordinator of most other endocrine glands)?
The pituitary gland
Which endocrine gland secretes the most hormones?
The pituitary gland
What does STH (growth hormone) stand for?
somatotrophic hormone
What does STH target?
The muscles and bones
What is the function of STH?
It promotes skeletal and muscular growth
What does hyposecretion of STH result in?
dwarfism
What does hypersecretion of STH result in?
Children: giantism
Adults: acromegaly
What does TSH (secreted by pituitary gland) target?
The thyroid gland
What does TSH do?
Stimulates the thyroid gland to secrete thyroxin
What does FSH (secreted by the pituitary gland) target?
The ovaries
What does FSH do?
stimulates the development of the follicle
stimulates the ovaries to secrete oestrogen
What does LH target?
Ovaries and testes
What is the function of LH in males?
stimulates the production of testosterone by testes
What is the function of LH in females?
stimulates ovulation and the development of the corpus luteum
What does the hormone prolactin (secreted by the pituitary gland) target?
The mammary glands
What is the function of prolactin?
Stimulates the production and secretion of breast milk
What does the hypothalamus detect?
Changes in the solute concentration in the blood
What happens if the blood becomes too concentrated?
The hypothalamus causes a sensation of thirst and stimulates the pituitary gland to secrete ADH
What does ADH stand for?
anti-diuretic hormone
What does ADH target?
the kidneys
What is the function of ADH?
helps conserve water in the body by causing more water to be reabsorbed into the blood.
What two hormones play an important role in the kidneys?
ADH and aldosterone
What part of the adrenal gland secretes adrenalin?
The adrenal medulla
What part of the adrenal gland secretes aldosterone?
The adrenal cortex
What is the target organ of aldosterone?
Collecting ducts of the kidneys
What is the function of aldosterone?
It controls the concentration of sodium in the blood
What function does adrenalin have?
It prepares the body for action to cope with an emergency
What are EIGHT effects of adrenalin on the body?
blood pressure increases (blood vessels constrict) blood sugar levels increase (glycogen converted to glucose) oxygen content increases heart rate increases pupils dilate sweating increases skeletal muscle tone is increased reduction of digestive system activity
Why does blood pressure increase (due to the blood vessels constricting) due to the secretion of adrenalin?
More blood can flow to skeletal and cardiac muscles where it is needed
Why do blood sugar levels increase (by glycogen in liver being converted into glucose) when adrenalin is secreted?
Glucose is required for cellular respiration, which results in more energy being produced
Why does oxygen levels increase when adrenalin is secreted?
Oxygen is required for cellular respiration which will result in more energy being produced
Why does heart rate increase when adrenalin is secreted?
Blood which transports glucose and oxygen reaches the muscles
This increases cellular respiration which increases energy
Why do the pupils dilate when adrenalin is secreted by the adrenal gland?
The body has better vision in times of danger
Why does the body sweat when adrenalin in released by the body?
Overheating is prevented
Why does skeletal muscle tone increased when adrenalin is secreted?
muscles can respond quickly
why is there a reduction in digestive system activity when adrenalin is secreted?
In an emergency, the digestive process is a waste of valuable energy
What are the gonads
the reproductive organs (testes and ovaries)
What do the hormones secreted by the gonads stimulate?
secondary sexual characteristics at the start of puberty
What if the target organ for oestrogen which is secreted by the ovaries?
the whole body, especially the uterus
What are some of the functions of oestrogen, which is secreted by the ovaries?
development of secondary sex characteristics
rapid increase in growth
stimulates rebuilding of endometrium
What is the target organ for progesterone?
uterus
What is the function of progesterone?
It causes the endometrium to:
thicken
become more vascular
In preparation for receiving a fertilised ovum (egg)
What is the target organ for testosterone?
the whole body
What is the function of testosterone?
development of secondary sex characteristics
sex drive
sperm production
What is hypoglycaemia?
when the glucose lever in the blood is too low
Within the islets of Langerhans (in the pancreas), which cells secrete glucagon and which cells secrete insulin?
alpha cells: glucagon
beta cells: insulin
What two hormones function together to control blood sugar levels in the blood?
glucagon and insulin
What is hyperglycaemia?
When the glucose level in the blood is too high
What organ does glucagon target?
The liver
What is the function of glucagon?
Stimulates the conversion of glycogen to glucose
What does insulin target?
The liver and muscle cells
What is the function of insulin?
stimulates the conversion of glucose to glycogen and therefore lowers blood glucose levels
What is the difference between glycogen and glucagon?
Glucagon: A hormone; raises blood sugar
Glycogen: A stored form of glucose
What happens when the beta cells in the islets of Langerhans in the pancreas are unable to produce enough insulin?
The body is unable to control the level of glucose in blood
Type 1 diabetes
What are symptoms of type 1 diabetes?
tiredness
constant thirst
large quantities of urine
weight loss
How do type 1 diabetics control the level of glucose in their blood?
daily insulin injections
Takes the place of insulin that should normally be produced by the body
Where is the thyroid gland?
on both sides of the trachea, just below the larynx in the front of the neck
What is the main hormone secreted by the thyroid gland?
thyroxin
What is the target organ for thyroxin?
all body ce3lls, the heart and the nervous system
What is the function of thyroxin?
increases the basal metabolic rate
involved in normal functioning of heart (heart rate & blood pressure)
essential for normal functioning of the nervous system
What are some of the symptoms of hyposecretion of thyroxin?
stunted physical growth
stunted mental ability
thick tongue
What is a deficiency (hyposecretion) of thyroxin in adults called?
myxoedema
What is a deficiency (hyposecretion) of thyroxin in early childhood brain development called?
cretinism
What is the hypersecretion of thryroxin known as?
goitre
There is only one name for HYPERSECRETION of thyroxin in both adults and children
What are some symptoms of hypersecretion (usually resulting in goitre) of thyroxin?
swollen thyroid gland and neck
protruding eyes
hyperactivity
increased heart rate
How is the level of thyroxin in the body kept constant?
By a negative feedback mechanism
What is needed in order to make thyroxin?
The micro-nutrient, iodine
What exists to detect and restore changes or imbalances in the internal environment of the human body?
negative feedback mechanisms
What happens when an imbalance in the internal environment of the body is detected?
a control centre is stimulated
the control centre sends info to an effector (target organ)
The effector responds and causes the levels to return to normal
When does the effector stop responding to the message from the control centre?
until the detector finds that a certain level is too low/high
the detector then sends a message to the effector to stop its action
the effector then responds
What are some examples of negative feedback mechanisms in the human body?
regulation of thyroxin
regulation of blood sugar level
regulation of water levels
Which two glands are involved in the control of thyroxin levels?
the thyroid gland (which releases thyroxin)
the pituitary gland (which releases TSH)
What happens when the thyroxin levels decreases below normal levels?
the pituitary gland is stimulated to produce TSH
High TSH levels stimulate the thyroid gland to secrete more thyroxin
What happens when thyroxin levels increase above normal levels?
The pituitary gland is stimulated to produce less TSH
The low TSH levels stimulate the thyroid gland to secrete less thyroxin
What happens when glucose levels increase?
the beta cells in the pancreas secrete insulin.
glucose is converted into glycogen and stored in the liver and muscles
What. happens when the glucose levels decrease?
The alpha cells in the pancreas secrete glucagon.
glycogen in the liver is converted into glucose
What does injected insulin that diabetics take help do?
helps to move sugar from the blood into other body tissues there it is used for energy
Also stops the liver from producing more sugar
