Adrenal Medulla Consists of groups of irregularly shaped cells
(medullary cells) around the blood vessels, these cells are
connected to the autonomic nervous system with sympathetic
division. Consists of Chromaffin Cells that convert the amino acid
tyrosine into adrenaline and noradrenaline. Release is stimulated
by acetylcholine which is from preganglionic sympathetic fibres
inside the medulla. When the signal from the brain is released, the
blood vessels are dilated and adrenaline or noradrenaline is
released in a 17:3 ratio.
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Adrenaline and Noradrenaline Adrenaline and noradrenaline bind
to adrenergic receptors which are transmembrane proteins in the
plasma membrane of many cell types. These are protein hormones that
are short term. Target Cells for Adrenaline include: Heart Cells
Muscle Cells Red Blood Cells (Circulating Oxygen) Liver Cells,
Brain Cells, Repository system, skin cells
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Adrenaline and Noradrenaline
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What Does Adrenaline Do? When targeting cells, the following
occurs in the body: Increase in Heart Rate & Strength Increase
in Blood Sugar Blood Shunted from Skin & sent to Internal
Organs Increase Metabolic Rate Pupils and Bronchi dilate Secretion
of ACTH from the anterior lobe of the pituitary increases This is
immediate, vigorous action
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Adrenal Cortex Triggered by the release of ACTH from the
anterior lobe of the pituitary; an increase of ACTH was stimulated
by the adrenal medulla earlier. Made up of three distinct layers GF
& R which correspond to G=Salt levels, F= Sugar Levels and R=
Sex Hormone Levels
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How Cholesterol Gets In The adrenocortical hormones are made
from cholesterol During excitement, cholesterol is goes into the
inner mitochondrial membrane in the Adrenal Cortex, it is then
converted into Cortisol and Aldosterone The amount of cholesterol
limits the amount of hormones that can be produced
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Target Cells 1.Travel through the blood stream to locate the
target cells such as: 2.Hormone binds to receptor of the target
cell, usually a protein in the cytoplasm or nucleus 3.A dimer is
formed when two hormone- receptors bind together. 4.The dimer
migrates to the nucleus of the cell, if it is not already. 5.The
dimer bonds to hormone response elements in DNA. 6.These elements
are the promoter regions for genes that start the process of
transcription. This produces the steroid hormones, which are long
term.
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Mineralocorticoids Have an effect on mineral metabolisms
Control Salt Levels (G) Aldosterone Acts on the kidneys (Targets
kidney cells) Promotes re-absorption of Na ions into the blood,
since water follows Na it helps maintain blood pressure Reduces the
loss of Na through perspiration by acting on sweat glands Increases
the taste buds sensitivity to Na by acting on taste cells
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Glucocorticoids Raises the level of blood glucose which is
level F (sugar) Stimulate gluconeogenesis that resides in the liver
(targets liver cells) Gluconeogenesis converts fat and protein into
intermediate metabolites, which is then converted into glucose
Application: Used as an anti-inflammatory, prevents rejection of
transplanted organs and controls asthma.
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Androgens Secretes testosterone and other precursors to
androgens. Androgens are the final layer R (Sex hormones)
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Complications with the Adrenal Glands Cannot live without the
Adrenal Glands Endocrinologists specialize in Adrenal Problems Such
problems occur: Diabetes, male patterned baldness in women
Uncontrolled blood pressure, abnormal sodium or potassium levels
Excess fat in midsection Early puberty in males