Paper 1

• Endocrine system

  Uses hormones to transmit messages throughout the body
• Hormones

  Chemical messengers produced by glands and released into the bloodstream to regulate various bodily functions, such as metabolism, growth, and development

  
• Hypothalamus

  • Small but extremely important part of the brain that is located at the base of the brain, just above the brainstem
  • Endocrine gland that plays a vital role in regulating various bodily functions such as hunger, thirst, body temperature, sleep, and emotions
• Pituitary gland

  • Small, pea-sized gland located at the base of the brain
  • Often called the "master gland" because it controls several other hormone glands in the body
  • Produces and secretes many hormones that regulate various bodily functions, including growth, metabolism, reproduction, and stress response

  
• Thyroid gland

  • Important endocrine gland located in the neck
  • Produces and releases the hormone thyroxin which plays a critical role in regulating the body's metabolic rate, which is the rate at which the body converts food into energy
  • Regulated by the pituitary gland, which produces thyroid-stimulating hormone (TSH) to stimulate the thyroid gland
• Pancreas


  • Organ located in the abdominal cavity, behind the stomach
  • Plays a crucial role in digestion and regulating blood sugar levels in the body
  • Endocrine function involves the production and secretion of the hormones insulin and glucagon, which help regulate blood sugar levels

  
• Adrenal glands

  • Pair of small, triangular-shaped glands that sit on top of the kidneys
  • Part of the endocrine system and produce and secrete hormones that regulate various bodily functions

  
• Gonads

  • Endocrine glands that secrete sex hormones
  • Male gonads (testes) secrete testosterone
  • Female gonads (ovaries) secrete oestrogen, progesterone and small amounts of testosterone
• Homeostasis


  The maintenance of a constant internal environment
• Nervous system


  • Uses electrical signals to transmit information quickly between different parts of the body
  • Includes the brain, spinal cord, and nerves
  • Controls voluntary and involuntary actions such as movement, sensation, and reflexes
• Endocrine system


  • Uses hormones to transmit messages throughout the body
  • Hormones are chemical messengers produced by glands and released into the bloodstream to regulate various bodily functions, such as metabolism, growth, and development
  • Responses are slower but longer-lasting, allowing it to have more widespread effects on the body
• Types of glands


  • Endocrine glands
  • Exocrine glands
• Endocrine glands


  • Ductless
  • Secrete hormones into the bloodstream
• Exocrine glands


  • Have ducts
  • Secrete substances into a cavity or onto a surface
• The pancreas is both an endocrine and exocrine gland
• Endocrine glands


  • Hypothalamus
  • Pituitary gland
  • Thyroid gland
  • Pancreas
  • Adrenal glands
  • Ovaries
  • Testes
• Hormones


  • Special chemicals produced by glands in the body that help regulate and control various functions in the body
  • Act like messengers, travelling through your bloodstream and communicating with different organs and tissues to help maintain balance and keep your body functioning properly
  • Hormones do not act alone and often, two or more hormones will interact to elicit an effect
  • Mostly proteins but some can also be lipids (steroids)
  • Only needed in very small amounts and if too much or too little of a hormone is produced, certain disorders can occur
• Functions of hormones


  • Growth, development and reproduction
  • Maintaining homeostasis
  • Regulating the storage and usage of energy
• Hypothalamus


  A small but extremely important part of the brain that is located at the base of the brain, just above the brainstem. It is an endocrine gland that plays a vital role in regulating various bodily functions such as hunger, thirst, body temperature, sleep, and emotions.

  
• Hypothalamus


  • Acts as a control centre, receiving information from different parts of the body and then sending out signals to other parts of the brain and body to help maintain homeostasis
  • Links the nervous system to the endocrine system through the pituitary gland

  
• Antidiuretic hormone (ADH)


  A hormone produced by the hypothalamus that is responsible for maintaining water balance in the body (osmoregulation)

  
• How ADH controls water levels in the body

  1. ADH is sent from the hypothalamus to the pituitary gland

  2. ADH is stored until it is needed

  3. ADH acts on the kidneys to increase water reabsorption, which reduces urine output and helps with osmoregulation

  4. When the body's fluid levels are low, ADH levels increase, causing the kidneys to reabsorb more water and produce less urine

  5. When the body's fluid levels are high, ADH levels decrease, allowing the kidneys to excrete more water and produce more urine

  
• Pituitary gland


  A small, pea-sized gland located at the base of the brain. It's often called the "master gland" because it controls several other hormone glands in the body. It produces and secretes many hormones that regulate various bodily functions, including growth, metabolism, reproduction, and stress response.

  
• Pituitary gland


  • Divided into two parts: the anterior pituitary and the posterior pituitary
  • The anterior pituitary produces hormones such as growth hormone, prolactin, follicle-stimulating hormone, luteinizing hormone, and thyroid-stimulating hormone
  • The posterior pituitary stores and releases ADH, which is produced by the hypothalamus and regulates water balance in the body

  
• Hormones and their functions

  • Thyroid-stimulating hormone (TSH) - Stimulates the thyroid gland to produce thyroxin
  • Follicle-stimulating hormone (FSH) - Stimulates germ cells to mature in males and females, stimulates the ovaries to produce oestrogen in females
  • Luteinizing hormone (LH) - Causes ovulation in females, stimulates the testes to produce testosterone in males
  • Prolactin - Stimulates lactation (when the mammary glands produce milk once a baby is born)
  • Growth hormone (GH) - Causes the growth of tissue and increases the size of muscles and bones
• Growth hormone conditions


  • Dwarfism - Abnormal growth resulting in significantly short stature, caused by too little growth hormone
  • Gigantism - Abnormal growth resulting in a significantly tall stature, caused by too much growth hormone (from childhood)
  • Acromegaly - Excessive growth of bones and tissues, specifically in the hands and face, caused by too much growth hormone (in adulthood)
• Acromegaly


  • Excessive growth of bones and tissues, specifically in the hands and face
• Comparison between gigantism and dwarfism

  • Gigantism - Abnormal growth resulting in a significantly tall stature
  • Dwarfism - Abnormal growth resulting in significantly short stature
• Thyroid gland


  An important endocrine gland located in the neck that produces and releases the hormone thyroxin
• Thyroxin


  A hormone produced by the thyroid gland that plays a critical role in regulating the body's metabolic rate
• Pituitary gland


  A small gland located at the base of the brain that produces thyroid-stimulating hormone (TSH)
• Thyroid-stimulating hormone (TSH)


  A hormone produced by the pituitary gland that stimulates the thyroid gland to produce and release thyroxin
• Problems with the thyroid gland can lead to a range of health issues
• Hyperthyroidism


  An overactive thyroid gland that produces too much thyroxin, causing the thyroid to become enlarged and swollen, and may result in the formation of goitre
• Goitre


  A swelling or lump at the front of the neck caused by a swollen thyroid gland
• Hypothyroidism


  An underactive thyroid gland that does not produce enough thyroxin
• Cretinism


  A condition caused by iodine deficiency in children, resulting in poor growth, intellectual disability, delayed motor development and other issues
• Myxoedema


  A condition caused by iodine deficiency in adults, resulting in low metabolic rate, water retention, weight gain, fatigue, goitre, and decreased heart rate
• Many countries, including South Africa, add iodine to table salt to prevent iodine deficiencies
• Pancreas


  An organ located in the abdominal cavity, behind the stomach, that plays a crucial role in digestion and regulating blood sugar levels