Chapter 14 - Endocrine System

Endocrine gland

• group of cells that secrete hormones

Major Endocrine glands

• pituitary gland

  • growth hormone, ADH, gonadotrophins

• thyroid gland

  • thyroxines

• adrenal gland

  • adrenaline

• testis

  • testosterone

• pineal

  • melatonin

  • brain

• thymus

  • thymosin

  • above the chest

• pancreas

  • insulin

  • glucagon

• ovary

  • oestrogen

  • progesterone

Hormones

• secreted directly into blood

• transported in blood plasma all over the body

• diffuse out of blood and bind to target cells (complementary shape)

• stimulate target cells to produce a response

Types of hormones

• steroid

  • lipid soluble

  • pass through the membrane

  • bind to receptors in the cytoplasm or nucleus

• non-steroid

  • hydrophilic

  • can’t pass directly through cell membrane

  • bind to specific receptors on the cell surface membrane

  • triggers a cascade reaction

Hormonal vs neuronal

• hormonal

  • slow response

  • longer lasting effects

  • transmission by blood

  • widespread response

  • effect may be permanent

• neuronal

  • rapid response

  • short lived effects

  • transmission by nerves

  • localised response

  • effect is temporary

Adrenal glands

• adrenal cortex

  • outer region

  • hormones that are vital to life

  • glucocorticoids

    • controlled by hypothalamus

    • cortisol

      • regulates metabolism

      • regulates blood pressure and cardiovascular function

    • corticosterone

      • regulates immune response

      • suppresses inflammatory reactions

  • mineralocorticoids

    • controlled by kidney

    • aldosterone

      • maintains water and salt concentrations

  • androgens

    • sex hormones

    • ovaries and testes

• adrenal medulla

  • inner region

  • non-essential hormones

  • adrenaline

    • increases heart rate

    • increases blood glucose concentration levels

  • noradrenaline

    • works with adrenaline

    • increased heart rate, dilated pupils, widening of air in lungs

    • narrowing of blood vessels

Pancreas roles

• exocrine gland

  • produces enzymes

  • releases them via a duct into the duodenum

• endocrine gland

  • produces hormones

Pancreas - exocrine gland

• produces digestive enzymes and pancreatic juice

• most of the pancreas is exocrine glandular tissue

• amylases

  • breaks down starch into simple sugars

• proteases

  • breaks down proteins into amino acids

• lipases

  • breaks down lipids into fatty acids and glycerol

Pancreas - endocrine gland

• produces insulin and glucagon

  • regulate blood glucose concentration

• in the exocrine tissue, there are regions of endocrine tissue

  • islets of Langerhans

  • these cells produce insulin and glucagon

Histology of the pancreas

• islets of Langerhans

  • lighter stained

  • large, spherical clusters

  • endocrine

• pancreatic acini

  • darker stained

  • small, berry-like clusters

  • exocrine

Islets of Langerhans

• alpha cells

  • produce and secrete glucagon

  • stain pink

• beta cells

  • produce and secrete insulin

  • stain blue

Type 1 diabetes

• beta cells in islets of Langerhans do not produce insulin

• can’t be cured but can be treated

• treated with regular injections of insulin

• test blood glucose concentration to know how much insulin to inject

Type 2 diabetes

• can’t effectively use insulin

• either because beta cells don’t produce enough insulin or cells do not respond properly to insulin

• usually due to being overweight, poor diet and lack of exercise

• treated by regulating carbohydrate intake, increasing exercise

• in extreme cases, drugs can be taken

Production of insulin

• used to be taken from cows and pigs

• made by genetically modified bacteria

• less likely to cause allergic reactions

• produced in high quantities

• cheaper production costs

• religious/ethical concerns over using animal products

Baroreceptors

• pressure receptors

• detect changes in blood pressure

• e.g. if bp is low, heart rate will increase

• present in aorta, vena cava and carotid arteries

• impulses sent to the medulla oblongata centre

Chemoreceptors

• chemical receptors

• sensitive to changes in the pH of the blood

• detect changes in levels of particular chemicals in the blood

• located in the aorta, carotid artery and the medulla

Controlling heart rate

• medulla oblongata is responsible

• contains two centres linked to the SAN (sinoatrial node) in the heart

• one centre increases heart rate

  • sends impulses through the sympathetic nervous system

  • transmitted by the accelerator nerve

• the other decreases heart rate

  • send impulses through the parasympathetic nervous system

  • transmitted by the vagus nerve

Effect of hormones on heart rate

• hormones can influence heart rate

• e.g. adrenaline and noradrenaline

• hormones affect the heart itself