A summary of the notes on the lecture 'Principles of endocrine control', including the role of the hypothalamus, the types of signal transduction and the modes of cell signalling.
Glands: Group of epithelial cells
1) Peptides specialised for secretion
receptor Secretion: release of biochemicals from
Definitions
Signal
transduction a particular type of cell upon stimulation
Endocrine: glandular secretions enter
the bloodstream and circulate the body
Exocrine: glandular secretions travel
Signal through ducts
ATP AC cAMP
transduction
The hormone binds to the receptor which becomes
Modes
activated Principles Autocrine:
of cell the
biochemical
The 2nd messenger is released and activates an signaling secreted
effector protein – in this case adenyl cyclase of acts on the same cell
The adenyl cyclase converts ATP to cyclic AMP
Further events occur leading to a cell response endocrine Paracrine: the biochemical secreted
acts locally on nearby cells
(signal transduction)
control Hormonal: the biochemical secreted
2) Steroids travels in the systemic bloodstream
Nucleus containing before binding to the target cell’s
DNA receptors
receptor Neuroendocrine: gland in the CNS
Protein releases a biochemical into a
mRNA synthesis circulatory system before they reach
The steroid passes through the cell membrane and the target cell.
Hormone
classification Neurotransmitters: biochemicals
binds to a receptor inside the cell
Once bound, it acts on the DNA acting as a released from a neurone straight to
transcription factor
The genes are then transcribed and produce mRNA,
the target cell (so it itself acts locally)
leading to protein synthesis and a cell response
Solubility Structure
- Hydrophilic (so can - Peptides: hydrophilic; chain
Hypothalamusa dissolve in plasma) of specific amino acids
nd pituitary - Lipophilic (so can - Amines: solubility varies in
easily pass through this group; derivatives of
the cell membrane) amino acids
The hypothalamus and the pituitary gland form part - Steroids: lipophilic;
of the CNS. The pituitary is split into two lobes, the derivatives of cholesterol
anterior and posterior, and it is connected to the
hypothalamus by the pituitary stalk. Hypothalamus-pituitary-gonad (HPG) axis
This is the axis that is responsible for the production and
Anterior lobe Posterior lobe
regulation of the (lipophilic) sex hormones: oestrogen and
Hypothalamus produces Hormones produced in
progesterone (at the ovaries) and testosterone (at the
releasing and inhibiting the hypothalamus but
testes). The hypothalamus produces gonadotrophin-
hormones which cause released in the posterior
releasing hormone causing gonadotrophs (a specific group
the anterior pituitary pituitary gland
of cells in the anterior pituitary) to produce FSH and LH
gland to release its own
which in turn cause the ovaries or testes (both of which are
hormones into the blood Neurohypophysis –
endocrine glands) to produce their respective hormones.
connection to the
The levels of testosterone are regulated through negative
Adenohypophysis – hypothalamus via a
feedback, whilst the levels of progesterone and oestrogen
connection to the neural pathway
are controlled through both positive and negative feedback.
hypothalamus via the
Control of testicular function Control of ovarian
pituitary portal system
function
(the circulatory system
connecting the anterior
pituitary to the
hypothalamus) – more
vascular
Contains its own
glandular cells
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