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Describe the endocrine system

The endocrine system works along with the nervous system to regulate the functions of the human body to maintain homoeostasis.

However the endocrine system works much more slowly than the nervous system, which can cause responses to occur within milliseconds.

The endocrine system and it’s widely scattered glands secrete hormones are diffuse from the interstitial fluid into the bloodstream.

The hormones, which are chemical messengers, act on target cells, regulating their metabolic functions.

Hormones affect most body cells, regulating growth and development, balance of blood components, body defences, cellular metabolism, Energy balance, and even reproduction. Hormones are considered long-distance chemical signals.

The Endo crime system controls body processes for long periods of time.

The endocrine system, like the nervous system, uses chemical signals that binds to receptor molecules.

Cells that make up endocrine glands are glandular epithelium.

Speed of onset of hormones can be seconds, minutes, or hours. Duration of action can be brief or lasting for days even if secretion stops.


Define the term hormone

Hormones are chemical signals released by glands in the endocrine system. In comparison the nervous system releases neurotransmitters at synapses. Some chemical signals can be found both in the endocrine glands and at a synapse.


Describe the site of production and action of: oxytocin

Produced by the pituitary gland, posterior lobe.

Oxytocin stimulates uterine contractions during childbirth and milk let down. The hormones stimulatory effects are most effective on uterine smooth muscle. When blood levels of oxytocin rise, uterine contractions increase until expulsion of the fetus occurs.

Source: Hypothalamus in response to stretching of uterine and vaginal walls and stimulation of breasts.

Action: Contracts uterine wall muscles and contracts milk secreting gland muscles.


Describe the site of production and action of: Adrenaline

Produced in the adrenal glands

Adrenaline is also called epinephrine.

Epinephrine affects heart by increasing rate and force of contraction.

It affects blood vessels by dilating the skeletal muscle vessels, increasing bloodflow resistance.

Systemic blood pressure increases because of increased cardiac output.
It affects the airway is causing them to dilate.

It activates reticula brain formation.

It effects the liver by promoting glycogen-to-glucose breakdown; increase blood sugar concentration.

Increases metabolic rate.


Describe the site of production and action of: noradrenaline

Produced by the adrenal medulla of the adrenal gland.

Norepinephrine is also called noradrenaline

Norepinephrine effects the heart by increasing the rate and force of contraction.

Blood vessels are effected, increasing skeletal muscle blood flow because of constriction of blood vessels in the skin and viscera.

Systemic blood pressure increases greatly because of vasoconstriction.

Airway is dilate slightly.

Has little effect on reticula brain formation.

Liver: Little effect on blood sugar concentration

Increases metabolic rate


Describe the site of production and action of: Insulin

Produced by the pancreas. More specifically the endocrine cells called ‘Islets of langerhans’. These cells, beta cells, secrete the hormone Insulin.

The insulin tells cells throughout your body to take in glucose from your bloodstream. As the glucose moves into your cells, your blood glucose levels go down.

Some cells use the glucose as energy. Other cells, such as in your liver and muscles, store any excess glucose as a substance called glycogen. Your body uses glycogen for fuel between meals.


Describe the site of production and action of: glucagon

Produced by the pancreas. More specifically the endocrine cells called ‘Islets of langerhans’. These cells, alpha cells, secrete the hormone Glucagon.

Glucagon works to counterbalance the actions of insulin.

About four to six hours after you eat, the glucose levels in your blood decrease, triggering your pancreas to produce glucagon. This hormone signals your liver and muscle cells to change the stored glycogen back into glucose. These cells then release the glucose into your bloodstream so your other cells can use it for energy.

This whole feedback loop with insulin and glucagon is constantly in motion. It keeps your blood sugar levels from dipping too low, ensuring that your body has a steady supply of energy.


Describe the site of production and action of: Aldosterone

The adrenal glands outer adrenal cortex synthesises aldosterone.

Aldosterone helps the kidneys to balance sodium and potassium and stimulate water retention via the process of osmosis.


Describe the site of production and action of: Angiotensin

Angiotensin I is produced by the action of renin (an enzyme produced by the kidneys) on a protein called angiotensinogen, which is formed by the liver. Angiotensin I is transformed into angiotensin II in the blood by the action of angiotensin-converting enzyme (ACE).

It can increase blood pressure by constricting the blood vessels.

It can also trigger thirst or the desire for salt.

Angiotensin is responsible for the release of the pituitary gland’s anti-diuretic hormone.

In the adrenal glands, angiotensin stimulates aldosterone production. This hormone causes the body to retain sodium. In the kidneys, sodium retention triggered by angiotensin changes the way the blood is filtered, causing increased water re-absorption to increase the volume of blood. This, again, increases blood pressure.

While angiotensin has a complex series of effects on the body, the primary results are higher blood volume, blood pressure and sodium content.


Describe the site of production and action of: ANP

Atrial natriuretic peptide (ANP) is a natriuretic peptide hormone secreted from the cardiac atria.

The heart functions as an endocrine organ, releasing atrial natriuretic peptide (ANP), a hormone, in response to sodium and fluid overload. Specifically, ANP is released by cardiac myocytes in response to atrial distension.

The main function of ANP is causing a reduction in expanded extracellular fluid (ECF) volume by increasing renal sodium excretion.

Its main function is to lower blood pressure and to control electrolyte homeostasis.

Makes you wee out more sodium in your wee


Describe the site of production and action of: ADH

Produced by the pituitary gland. Posterior lobe.

Causes conservation of water in the kidneys, in the high concentrations increase is blood pressure.