3.5 - Endocrine System

What are the main glands of the endocrine system?

• Pituitary gland

• Thyroid

• Parathyroid

• Adrenal

• Islets of Langerhans

• Testes and Ovaries (sex glands)

What is the difference between the endocrine and nervous system?

Nervous:

• More rapid and instantaneous

• Lasts a shorter amount of time

  • e.g. contracting a muscle

Endocrine:

• Slower speed

• More impactful

  • e.g. Metabolism

What are hormones and what are the two types?

Hormones are chemical messengers that are made by the endocrine glands. These messages help regulate functions throughout the body.

The two types are protein hormones and steroid hormones.

What are protein hormones and where are their receptors?

• Hydrophillic and cannot diffuse easily through the plasma membrane (they are polar)

• Because of this, they must bind to specific (extracellular) receptors that have the same shape as the hormone

e.g. insulin, glucagon, growth hormone

What are steroid hormones and where are their receptors?

• Synthesised from cholesterol

• Hydrophobic and can easily diffuse through plasma membrane as they are made from a lipid

• Because of this they have intracellular receptors in the cytosol

e.g. cortisol, aldosterone

What is the function of the pituitary gland and what happens if the hormones are over/under produced?

• Secretes 9 different hormones:

  • Growth

  • Blood pressure

  • Pregnancy regulation

  • Breast milk production

  • Sex organ function

  • Release of thyroid

  • Metabolism

  • Water regulation

  • Temperature

Growth hormone:

• Oversecretion:

  • Gigantism, all bones, hands, feet are very big

• Undersecretion:

  • Dwarfism, all bones and parts of the body are much smaller in stature

What is the function of the thyroid gland and what happens if the hormones are over/under produced?

• Releases thyroxine and calcitonin

• Thyroxine:

  • Regulates the rate of metabolism (increases)

  • Oversecretion:

    • Nervousness and weight loss

  • Undersecretion:

    • Underdeveloped mental capacity and less muscle development

• Calcitonin:

  • Regulates the metabolism of calcium (decreases blood calcium)

• Iodine deficiency in diet results in goiter - enlarged thyroid gland

What is the function of the parathyroid gland and what happens if the hormones are over/under produced?

• Releases parathormone

• Control the metabolism of calcium (increase levels)

  • Necessary for nerve and muscle function, blood clotting and healthy bones

• Undersecretion:

  • Nerve disorders, brittle bones (osteoporosis), clotting problems

What is the function of the adrenal gland and what happens if the hormones are over/under produced?

• Hormones released are cortisone and adrenaline

• Cortisone:

  • Released as a result of stress

  • Regulates carbs, proteins and fats

    • Converts fats and proteins to glucose

• Adrenaline:

  • Raise blood sugar levels, heart rate, breathing rate

    • Increased heart rate pumps blood and transports oxygen for muscles

    • Blood sugar levels for instant energy

What is the function of the pancreatic islets and what happens if the hormones are over/under produced?

• Hormones produced are insulin and glucagon

• Insulin:

  • Stimulates glucose uptake by cells

  • Takes the glucose from the blood and stores it as glycogen

• Glucagon

  • Converts the glycogen into glucose to raise blood sugar levels

  • Opposite of insulin

What are the two types of feedback in the endocrine system?

• Negative and positive feedback

• Negative:

  • Overall function is to increase or decrease the stimulus back to its original state

  • e.g. Insulin

• Positive:

  • Overall function is to amplify the stimulus to rapidly increase the response

  • e.g. Adrenaline