Lec1 Intro to Endo System Flashcards
- Comparison of nervous and endocrine systems - Definition of a hormone - Gross anatomy of the endocrine system - Mechanisms of hormone action - Characteristics of hormones - Control of the endocrine system
What is needed for communication to occur?
Two cells are required for communication to occur
One cell has to release a chemical transmitter to influence the activity of the other
The nervous system
allows very rapid, focused and precise communication between individual cells
The endocrine system
uses the cardiovascular system to transport the hormone
and allows very slow, sustained communication between groups of cells
The endocrine system is a system of:
DUCTLESS glands which secrete chemical messengers (HORMONES) into the blood
Hormones act on
cells possessing the appropriate hormone receptors - i.e. target tissues. Each hormone may act on several target tissues
Name the endocrine glands of the body
Pineal gland Pituitary gland Thyroid gland Parathyroid gland Adrenal gland Ovary Testis
The pituitary gland
is the most important - it communicates with the hypothalamus
The pituitary gland is situated:
below the brain, encased in skull
The pituitary gland controls the activity of:
the thyroid gland, adrenal glands, ovaries and testes
The stalk of the pituitary gland is known as:
infundibulum
The anterior pituitary gland stores and secretes:
Corticotrophin/ Adrenocorticotrophic hormone (ACTH)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Prolactin
Thyrotrophin/ Thyroid stimulating hormone (TSH)
Growth hormone (GH)
The posterior pituitary gland stores and secretes:
Oxytocin
Vasopressin
The thyroid and parathyroid glands are situated:
in the neck
The thyroid and parathyroid glands are important in the control of:
metabolic rate and calcium homeostasis
The exocrine function of the pancreas:
secretes digestive enzymes directly into the GI tract
The endocrine function of the pancreas
is ductless and secretes INSULIN and GLUCAGON into the blood
What is the function of insulin?
To regulate blood glucose concentrations and glucose utilisation
Where are the adrenal glands situated?
they lie on top of the kidneys
The adrenal glands are divided into?
The MEDULLA and CORTEX
The medulla of the adrenal glands is involved in?
the stress response
The cortex of the adrenal glands is involved in?
stress, sodium and glucose homeostasis
The gonads - ovaries or testes
secrete the female and male reproductive hormones
The male and female reproductive hormones are responsible for:
the development of secondary sexual characteristics and reproduction
How do hormones produce their effects?
by interacting with specific receptors - intracellular or membrane bound - in the target tissues
What are the major types of receptors?
Steroid hormone receptors
G-protein coupled receptors
Tyrosine Kinase receptors
Steroid hormone receptors are
cytoplasmic or nuclear
The steroid hormone receptor complex binds to:
hormone-response element of the DNA to influence gene transcription
the receptor may be constitutively active
When a hormone binds to G-protein coupled receptors
it causes synthesis of a second messenger
Give examples of second messengers
Inositol trisphosphate
Cyclic AMP
What do the second messengers do?
They phosphorylate intracellular, regulatory proteins to influence the cellular activity e.g. smooth muscle contraction
Activation of IP3 leads to:
smooth muscle contraction e.g. oxytocin
Production of cAMP leads to:
smooth muscle relaxation e.g. adrenaline causing bronchodilation
Giving IV oxytocin would cause:
Uterine contractions in a female within seconds
A tyrosine kinase receptor is a
membrane bound enzyme which is a single strand of protein
Often, in order for hormone action to occur at TyK receptors
two receptors must be present
dimerised receptor
What happens when one hormone molecule binds to each receptor?
The receptor then acts as an enzyme to phosphorylate the tyrosine components of intracellular, regulatory proteins
TyK receptors are involved with:
growth and development and have a very slow effect
Insulin acts via:
TyK receptors and lowers blood sugar within 15 mins
What are the two broad classes of hormones?
Peptide hormones
Steroid & Thyroid hormones
Peptide hormones are:
highly water soluble susceptible to protease attack unable to cross cell membrane without a carrier protein act on membrane bound receptors not orally active short plasma life short duration of action
Steroid & Thyroid hormones are:
highly lipid soluble
poorly water soluble
able to cross cell membrane and act on intracellular receptors
Orally active
Long plasma half life
Long duration of action
Must be transported in blood bound to plasma protein - dangerous if not because it travels in clumps
only unbound hormone is biologically active
Secretion of a hormone by a given gland is typically but not always controlled by:
Anterior Pituitary Gland
Anterior Pituitary Gland secretes:
Stimulating or Trophic hormones
Stimulating hormones
stimulate secretion of a hormone
Trophic hormones
cause the growth of a gland
The secretion of a hormone by the anterior pituitary gland is controlled by:
hypothalamus
The hypothalamus secretes:
Releasing hormones
Name the releasing hormones secreted by the hypothalamus
Corticotrophin releasing hormone (CRH)
Gonadotrophin releasing hormone (GnRH)
Thyrotrophin releasing hormone (TRH)
Growth hormone releasing hormone (GHRH)
The thyroid hormone decreases secretion of:
Thyrotrophin releasing hormone (TRH)
Thyroid stimulating hormone (TSH)
Cortisol acts to decrease secretion of:
Corticotrophin releasing hormone (CRH) Adrenocorticotrophic hormone (ACTH)
Oestrogen acts to decrease secretion of:
Gonadotrophin releasing hormone (GnRH)
Follicle stimulating hormone (FSH)
A common consequence of negative feedback is:
cyclical variation e.g. diurnal variation of cortisol secretion
What is a portal system?
a blood vessel directly linking two organs/structures
