Anatomy - Endocrine system Flashcards
What forms of intercellular communication is there
Gap junctions
Neurotransmitters
Paracrines
Hormones
Gap junctions
physically joined cells, enabling cytoplasms of different cells to connect. (smooth muscle, cardiac muscle, epithelial, and other cells).
Neurotransmitters
chemical messengers released by nerve cells or neurons, they diffuse across a narrow synaptic cleft, and bind to receptors on the surface of the next cell causing some change.
Paracrines
Chemicals (local hormones) secreted by one cell and diffuse into neighbouring cells, usually in the same tissue and stimulate their physiology.
Hormones
chemical messengers made by endocrine glands transported by the bloodstream and stimulate their target cells at a considerable distance.
What is endocrinology
It is the study of the endocrine system
What is the endocrine system
inter-cellular communication system that consist of glands, tissue and cells that secrete hormones.
What is the function of the endocrine system
It enables homoeostasis and structural changes in the body (increase height and development of sexual organs)
Endocrine and exocrine
Endocrine glands produce hormones that are directly secreted into the bloodstream, exocrine glands produce substances that are secreted via ducts.
What are the differences between the nervous and endocrine system
The nervous system communicates by means of electrical impulses and neurotransmitters while the endocrine system communicates by means of hormones.
The nervous system releases neurotransmitters at synapses at specific target cells while the endocrine system releases hormones into the bloodstream for general distribution throughout body.
The nervous system usually has relatively local, specific effects while the endocrine system sometimes has very general, widespread effects.
The nervous system reacts quickly to stimuli, usually within 1-10 msec while reacts mores slowly to stimuli, often taking seconds to days.
The nervous system stops quickly when stimulus stops while the endocrine system may continue responding long after stimulus stops.
The nervous system adapts relatively quickly to continual stimulation while the endocrine system adapts relatively slowly; may respond for days to weeks
Interactions of the endocrine and nervous system
They often interact each other
and…
ACTH name
Adrenocorticotropic hormone (corticotropin)
ACTH source
pituitary
ADH name
Antidiuretic hormone (vasopressin)
ADH source
Posterior pituitary
ANP name
Atrial natriuretic peptide
ANP source
Heart
CRH name
Corticotropin-releasing hormone
CRH source
Hypothalamus
DHEA name
Dehydroepiandrosterone
DHEA source
Adrenal cortex
EPO name
Erythropoietin
EPO source
Kidney, liver
FSH name
Follicle-stimulating hormone
FSH source
Anterior pituitary
GH name
Growth hormone (somatotropin)
GH source
Anterior pituitary
GHRH name
Growth hormone-releasing hormone
GHRH source
Hypothalamus
GnRH name
Gonadotropin-releasing hormone
GnRH source
Hypothalamus
IGFs name
Insulin-like growth factors (somatomedins)
IGFs source
Liver, other tissues
LH name
Luteinizing hormone
LH source
Anterior pituitary
NE name
Norepinephrine
NE source
Adrenal medulla
OT name
Oxytocin
OT source
Posterior pituitary
PIH name
Prolactin-inhibiting hormone (dopamine)
PIH source
Hypothalamus
PRL name
Prolactin
PRL source
Anterior pituitary
PTH name
Parathyroid hormone (parathormore)
PTH source
Parathyroids
T3 name
Triiodothyronine
T3 source
Thyroid
T4 name
Thyroxine (tetraiodothyronine)
T4 source
Thyroid
TH name
Thyroid hormone (T3 and T4)
TH source
Thyroid
TRH name
Thyrotropin-releasing hormone
TRH source
Hypothalamus
TSH name
Thyroid-stimulating hormone (thyrotropin)
TSH source
Anterior pituitary
Hypothalamus
forms the floors and walls of the 3rd ventricle. Regulates primitive functions, water balance, sex drive and childbirth. Works closely with the pituitary.
Pituitary gland
is suspended from the floor of the third ventricle by the infundibulum and sits in the sella turcica of the sphenoid bone.
Anterior part of the pituitary
called the adenohypophysis contains the anterior love and the Pars tuberalis
Posterior part of the pituitary
called the neurohypophysis composed of modified nervous tissue and it includes the median eminence, stalk (infundibulum) and posterior lobe.
Some of the hypothalamic neurons have long axons that go into the posterior pituitary forming the hypothalamic tract.
Paraventricular nucleus
of the hypothalamus are neurons concentrated on the walls of the third ventricle, these produce the hormone oxytocin.
Supraoptic nucleus
are another collection of hypothalamic neurons found just superior to the optic chiasm, these make the hormone ADH-antidiuretic hormone.
What is the optic chiasm
crossing of the left and right optic nerve
Hypophyseal portal system
a system of primary and secondary capillaries that transport hormones via the portal venues from the primary capillary bed to the secondary capillary bed.
About the hypothalamic hormones…
hormones secreted by hypothalamic neurons and then absorbed into primary capillary system formed by the superior hypophyseal artery.
Examples of hypothalamic hormones
Gonadotropin-releasing hormone (GnRH) Thyrotropin-releasing hormone (TRH) Corticotropin-releasing hormone (CRH) Prolactin-inhibiting hormone Growth hormone-releasing hormone (GHRH) Somatostatin
What does TRH do
Promotes secretion of thyroid-stimulating hormone (TSU) and prolactin (PRL)
What does CRH do
Promotes secretion of adrenocorticotropic hormone (ACTH)
What does GnRH do
Promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
What does GHRH do
Promotes secretion of growth hormone (GH)
What does Prolacting-inhibiting hormone (PIH) do
Inhibits secretion of prolactin (PRL)
What does somatostatin do
Inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH)
About anterior lobe hormones…
its secretion is stimulated by hypothalamic hormones transported by the hypophyseal portal
Examples of anterior pituitary hormone
Follicle-stimulating hormone (FSH) Luteinizing hormone (TSH) Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Prolactin (PRL) Growth hormone (GH)
Posterior pituitary hormone
Antidiuretic hormone (ADH) Oxytocin (OT)
Both produced in the hypothalamus
Where is (FSH) targeted
Ovaries, testes
Where is (LH) targeted
Ovaries, testes
Where is (TSH) targeted
Thyroid gland
Where is (ACTH) targeted
Adrenal cortex
Where is (PRL) targeted
Mammary glands, testes
Where is (GH) targeted
Liver, bone, cartilage, muscle, fat
What does (FSH) do
Female: growth of ovarian follicles and secretion of estrogen
Male: sperm production
What does (LH) do
Female: ovulation, maintenance of corpus luteum
Male: testosteron secretion
What does (TSH) do
Growth of thyroid, secretion of thyroid hormone
What does (ACTH) do
Growth of adrenal cortex, secretion of glucocorticoids
What does (PRL) do
Female: milk synthesis
Male: increased LH sensitivity and testosterone secretion
What does (GH)
Widespread tissue growth, especially in the stated tissues
About (ADH)…
It is targeted at the kidneys and is responsible for water retention
About (OT)…
It is targeted at the uterus and mammary glands and is in charged of labor contractions, milk release; possibly involved in ejaculation, sperm transport, sexual affection, and mother-infant bonding.
How does the pituitary secretion works
By negative feed back loop.
The hypothalamus releases TRH via the hypophyseal portal system, which impinge on the anterior pituitary and cause it to make TSH.
This is transported by the bloodstream to its targeted organ, the thyroid, which causes it to release the thyroid hormone.
Thyroid hormone has an inhibitory effect back in the anterior pituitary in terms of TRH.
Therefore this is regulated by negative feedback.
About pineal gland…
It is found in the brain. Mainly active up to puberty, then shrinks.
It regulates 24-hr circladian rhythms of physiology.
It secretes melatonin, thich varies with length of the day. Involved in pre-menstrual tension and seasonal affective disorder.
The gland also has a role on the onset of puberty.
About the thymus…
It is large in children, then shrinks. It secretes hormones that influence the development of T-lymphocytes and development of other lymphatic tissues and organs.
About the thyroid…
It is the largest endocrine gland in adults and has very high blood flow per gram. It produces mainly T4 hormones.
Thyroid hormone increases basal metabolic rate, respiratory rate, heart rate, strength of heart beat, promotes appetite and breaks down fuel molecules.
It also produces calcitonin for regulation of blood calcium.
About the Parathyroid…
Produces parathyroid hormone for regulation of blood calcium levels.
About the adrenal glands…
It is found on the superior pole of the kidneys.
Medulla - inner part (20%) Modified neurons called neuroendocrine cells/chromaffin cells which release the neurotransmitters adrenaline, noradrenaline and dopamine into the bloodstream. This hormones are responsible for the fight-fright-flight response.
Cortex - outer part (80%) Makes steroids (based of cholesterol) hormones called corticosteroids of corticoids.
What do corticosteroids or corticoids divide into
MIneralocorticoids - e.g. adosterone to control the blood pressure.
Glucocorticoids - e.g. cortisol to cause the breakdown of fats and proteins to cause the manufactoring of glucose and to release fatty acids and glucose into the blood.
Sex steroids - e.g. androgens which are converted into testosterone and oestradiol.
What is the manufactoring of glucose called
gluconeogenesis
About pancreas…
It has both endocrine and exocrine functions. For it’s endocrine function there are two types of cells:
Alpha cells - secrete glucagon, which stimulates gluconeogenesis, releases glucose into the blood, fat catabolism, and releases fatty acids.
Beta cells - secrete insuline, which increase the cellular uptake of glucose and causes particular organs to synthesis glycogen.
About gonads…
Ovaries - make oestradiol and progesterone, responsible for the menstrual cycle and in pregnancy.
Testes - make testosterone.
Important for secondary sexual characteristics, and growth.
What are the most common types of hormones
Steroids
Peptites
Monoamines
Examples of Steroid hormones
(derived from cholesterol)
oestrogens, progesterone and testosterone
Examples of peptites hormones
(short amino acid chains)
Insuline
Examples of monoamines hormone
adrenaline, noradrenaline and melatonin
Hormone receptors
Hormone act by binding to receptors which may be on the cell surface or intracellular receptors.
Chemical changes occur that bring about action.
Cells can control sensitivity to hormones by controlling the density of receptors. In up-regulation the cell produces more receptors and in down-regulation where the cell reduces its density.
