L27: Neuro-endocrine connection, hypothalmus

• the hypothalamus contains both brain centres and endocrine tissue. it provides the highest level of endocrine control
• hypothalamus provides highest level of endocrine control by intergrating the activities of the nervous and endocrine system.
• hypothalamus (posterior lobe) means neural connection
• hypothalamus on anterior lobe means capillaries, releasing hormones
• the hypothalamus on anterior pituitary, neurons release chemicals into a blood portal connection to anterior pituitary gland cells
• the hypothalamus to posterior pituitary, neurons have long axons that extend into and terminate in the posterior pituitary gland
• the posterior pituitary hormones are made in the hypothalamic neuron cell bodies. it travels down the axon to be stored in the axon terminals until required.
• posterior pituitary hormones are released into the main bloodstream when an action potential depolarises the axon terminal
• the hypothalamus is connected to the anterior pituitary by a portal blood stream.
• the neurons secret 'releasing' or 'inhibiting' horomones that travel via blood portal to the anterior pituitary and bind to the membrane receptors on the anterior pituitary cells, causing the anterior pituitary cells to release another hormone.
• oxytocin are water-soluble. it stimulates milk release during breast feeding. it stimulates the contraction of uterine muscles during childbirth
• anti-diuretic hormone (ADH) is water-soluble. it stimulates the kidney to reabsorb water when a person is dehydrated. it is one of the hormones secreted during exercise and stress response
• growth hormone is water-soluble. it stimulates growth and fuel mobilisation and stimulates release of IGF-1 from liver also for growth.
• thyroid secreting hormone (TSH) is water-soluble. it stimulates the release of thyroid hormones from the thyroid gland, to increase basal metabolic rate
• Adrenocorticotropin hormone is water-soluble and stimulated the release of cortisol for stress response
• connections label

  A) hypothalamus

  B) blood

  C) anterior

  D) posterior

  E) blood

  
• ADH and OXT are released into circulation from the posterior lobe of the pituitary gland
• pattern or hormone release

  A) stimulus

  B) hypothalamus

  C) releasing hormone

  D) anterior

  E) pituitary hormone

  F) target endocrine organ

  G) 3rd

  H) target effectors

  I) effect

  
• when the stimulus is exercise and cold stress, the hypothalamus secretes TRH. the anterior pituitary gland secrets TSH. the thyroid gland secrets thyroid hormones. the target of thyroid hormones are all body cells. the effects increase basal metabolic rate.
• target cell activation by thyroid hormones (T3 and T4) are made in advance and stored until required. it it travels bound to a carrier protein and detaches from the carrier protein and enters the target cell
• thyroid hormones bind to the receptor in the nucleus
• specific genes are activated to transcribe messenger RNA (mRNA) and specific proteins are synthesised that lead to increased basal metabolic rate. the response time is 45 minutes to days
• Basal metabolic rate (BMR) is the energy the body requires for its most basic functions to sustain life.
• BMR is influenced by sex, age, body type, food intake, etc
• thyroid hormones increase BMR by increasing thermogenesis, oxygen and ATP consumption and fat, protein breakdown
• thyroid hormones also have a complex interaction with various organs to ensure enough glucose is available for metabolic processes, without disturbing the plasma glucose homeostasis
• the thyroid gland wraps around the trachea, just below the adams apple and on the anterior and lateral surfaces of the trachea
• thyroid hormones (T3 and T4) are made by cells that line the follicles to increase metabolic activity, growth and alertness
• the structural and function units of the thyroid gland are thyroid follicles
• thyroglobulin (TGB) is a protein made in thyroid follicles and contains tyrosine (Y).
• iodine (I) enters the cells lining a thyroid follicle and reacts with tyrosine (Y) in thyroglobulin (TGB)
• thyroid hormones detach from iodised TGB as they are needed and travel in blood bound to a carrier protein
• Hypothalamus, pituitary gland and parathyroid glands are involved in growth and cell metabolism
• daily secretion pattern: growth hormone plasma concentration fluctuates over a day and are highest during sleep
• lifetime secretion pattern: growth hormone plasma concentration is higher in children than adults and highest during puberty and decline with age
• label direct effects of GH: fuel mobilisation

  A) muscle

  B) inhibits

  C) cellular uptake of glucose

  D) protein synthesis

  E) liver

  F) glucose synthesis

  G) adipose

  H) increases fat breakdown

  
• indirect effects of GH (growth) via insulin-like growth factor (IGF-1)
• IGF-1 is released from liver cells when stimulated by GH and promotes the growth of bones, muscles and other tissues
• in adults, GH helps maintain normal glucose concentration to mobilise lipid reserves