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.
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
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
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
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
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.
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
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.
Androgens Secretes testosterone and other precursors to androgens. Androgens are the final layer R (Sex hormones)
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