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Week 4 Lecture 12: Endocrine System (Hormones (Three different groups (2.…
Week 4 Lecture 12: Endocrine System
Hormones
Molecular signals
Released by specific cell types
Influence other cells
The study of hormones is known as
endocrinology
Three
different groups
1.
Peptides or proteins
Major group
Water soluble (hydrophilic)
Easily transported in
blood
Packaged within vesicles in cells
Secreted via
exocytosis
e.g. insulin
2.
Steroid hormones (lipid hormones)
Synthesised from
cholesterol
, a steroid
Lipid soluble (lipophilic)
Can pass through cell membranes
NOT packaged into vesicles
Secretion regulated by
regulating synthesis
This is how synthesis is limited
Diffuse
out of cells
Steroid hormones are
bound
to carrier molecules in blood
e.g. testosterone
Because steroid ligands are lipophilic, they are
hydrophobic
and need the
hydrophilic
carrier molecule to transport them
e.g. estrogen
e.g. aldosterone
e.g. cortisol
3.
Amines
Mostly synthesised from
tyrosine
, an essential amino acid
Can be water soluble OR lipid soluble (hydrophilic or lipophilic)
Therefore, mode of action differs
e.g. epinephrine
e.g. thyroxine
A system that includes a variety of cells, tissues and organs that produce hormonal molecular signals
Hormone receptors
(same as Lecture 11)
Three
different kinds
1.
Membrane bound
Binded to a
protein/amine
Causes a signal transduction
cascade
Activation of an enzyme in cytoplasm
Short-term effect
e.g. epinephrine stimulate glucose synthesis
Activate another molecule to stimulate RNA transcription in nucleus
Synthesis of a product via cytoplasmic enzymes
2.
Cytoplasmic
Binded to a
steroid/amine
Steroid hormones mostly act in the nucleus
3.
Nuclear
Usually a
steroid-receptor complex
that travels through the nuclear pore into the nuclear
#
This initiates or inhibits
RNA transcription
Regulating a
number of genes (20 or 30)
Long-term effect
Effects up to an hour, a few hours or even more
Glands
Hormones are in glands
Glands are tissue
Epithelial tissue
Connective tissue
Two
types of glands in the body
1.
Endocrine
Aggregation/collection of cells that
secrete hormones
directly into the
blood
e.g. endocrine pancreas secretes
insulin
and
glucagon
directly into blood
Types of endocrine glands in humans, their hormones and their target tissue
(or function)
Pineal gland
Melatonin
Hypothalamus
Releasing and inhibiting hormones that directly stimulate or inhibit the anterior pituitary gland to secrete its hormones, via the
portal vessels
Pituitary gland
(raisin-sized; releases
eight
hormones)
Anterior pituitary
Thyroid stimulating hormone (TSH) :red_flag:
Thyroid gland
Also known as
thyrotropin
Follicle stimulating hormone (FSH)
Ovaries
Allows the egg to ovulate in the ovaries
Testes
Enables sperm production
Luteinising hormone (LH)
Regulates release of sex hormones (steroids) in the gonads
Testes
Ovaries
Adrenocorticotropic hormone (ACTH)
Adrenal glands
Stimulates the production of cortisol from the adrenal glands
Also known as
corticotropin
Growth hormone (GH)
Most cells
Tropic or non-tropic?
Prolactin
Breast cells
Stimulates breast milk in women
Sexual response in men
Effect on oligodendrocytes (glial cells) in brain
Endorphins
Pain receptors in the brain
Posterior pituitary
Oxytocin
Uterine muscles
Uterine contraction to prepare the uterus for delivery, and during delivery
Mammary glands
Antidiuretic hormone (ADH)
Kidney tubules
Regulates the amount of water in blood
Parathyroid glands
Four
small glands behind the thyroid gland
Release
parathyroid hormone
to increase
calcium
levels in the blood
Thyroid gland
Thyroxine :red_flag:
Calcitonin
Regulates blood calcium levels
Also synthesised by the follicular cells
Thymus gland
Adrenal glands
Two
, one on top of each kidney
Components of an adrenal gland (synthesise and store hormones)
Inner medulla
Epinephrine :red_flag:
1 more item...
Norepinephrine
1 more item...
These hormones from the
inner medulla
are
amines
which are NOT lipid soluble
1 more item...
The brain detects danger and signals the adrenal glands to release epinephrine and norepinephrine in a
stressful situation
2 more items...
Outer cortex
Aldosterone
Cortisol
Pancreas
Insulin
Decreases blood glucose levels
Glucagon
Increases blood glucose levels
Gonads (release sex hormones)
Ovaries
Estrogen
Progesterone
Testes
Testosterone
Other types of endocrine glands that
secrete hormones
Adipose tissue
Heart
Stomach
Skin
Liver
2.
Exocrine
Secrete enzymes
(usually) via ducts to an external environment (target tissue/organ)
Often to an external surface (but not necessarily skin – can be the gut for example)
e.g. exocrine pancreas secretes
enzymes
and
bicarbonate
via a duct to the
duodenum
:red_flag:
e.g. salivary glands secrete
amylases
during mechanical digestion
e.g. lacrimal glands
e.g. gallbladder
Hypothalamus and pituitary gland
Pituitary gland
Location
Put two sticks through both ears and one up the nose; where they meet is the pituitary gland location
Sits
below
the hypothalamus
Sits in a cavity, a bony depression of the skull bone known as the
sella turcica
Function
Secretes a number of hormones
Anatomy
Anterior pituitary (towards the
front
)
Gland – epithelial and connective tissue
Made up of
cells
:warning:
Posterior pituitary (towards the
back
)
Neural tissue
:warning:
Linked to the hypothalamus via a
stalk
The cell body (
soma
) is located in the hypothalamus
The cell body is connected to neuron axons that run down the stalk (
infundibulum
)
The axons leads to the axon
terminals
in the posterior pituitary where hormones are released into capillaries
Hypothalamus
Location
Sits
above
the pituitary gland
Part of the brain, but sits in a region full of neural cell bodies
Function
Controls and regulates what the pituitary gland secretes
Pituitary tumour
Removed via
trans-sphenoidal surgery
via two methods
Sublabial approach
Goes through the upper lip to open a path between the hard palate in the roof of the mouth and the nose
Most common
method of pituitary tumour removal
Relatively painful
Endonasal approach
Goes through the back of the nostril using an endoscope to see and a curette to remove the tumour
Minimally invasive