compendium 10

• list the main organs of the endocrine system (9)

  1. pineal gland

  2. hypothalamus

  3. pituitary gland

  - anterior

  - posterior

  4. parathyroid glands

  5. thymus gland

  6. adrenal gland

  7. pancreas

  8. ovary

  9. testis
• pineal gland


  - sleep wake cycles

  - melatonin
• hypothalamus


  makes 2 hormones (neuropeptides)

  - oxytocin

  - ADH
• similarities between the nervous and endocrine system

  - both associated with the brain

  - uses same chemical messenger as neurotransmitter and hormone e.g. epinephrine

  - two system are cooperative
• differences between the nervous and endocrine system

  mode of transport

  - axon: NS

  - blood: ES

  speed of response

  - instant: NS

  - delayed: ES

  duration of response:

  - seconds/milliseconds: NS

  - minutes, days: ES
• structure of posterior pituitary (neurohypophysis)


  extension of the nervous system via infundibulum

  secretes neuropeptides

  nervous tissue
• structure of anterior pituitary (adenohypophysis)


  develops from embryonic oral cavity

  secretes traditional hormones

  glandular tissue
• relationship between anterior pituitary gland and hypothalamus

  - hypo regulates secretions of anterior pituitary gland

  - makes 7 hormones to go into circulation

  - blood vessels make up hypothalamohypophysial portal system (hormones travels through this to APG)

  - hypothalamis releasing and inhibiting hormones stimulate or inhibit APG hormones release
• relationship between posterior pituitary and hypothalamus


  - posterior pituitary extension of hypothalamus

  - neuropeptides made by hypothalamus to travel down stalk to posterior PG

  - hormones produced in hypo stored in posterior PG

  - axons form hypothalamohypophysial tract

  - action potentials in neurons cause hormone release
• describe how the hypothalamus and anterior pituitary gland interact with one another for target tissues


  - stimuli from NS regulate secretion of releasing hormones from neurons in hypothalamus

  - releasing hormones pass to APG (hypothalamohypophysial portal system)

  - releasing hormone = stimulate hormone release from APG

  - hormones travel into blood stream to target tissue (cells that the receptor on it)
• list the hypothalamic hormones

  1. growth hormone releasing hormone (GHRH)

  2. growth hormone inhibiting hormone (GHIH)

  3. thyrotropic-releasing hormone (TRH) TSH secretion

  4. melanocyte releasing hormone (MRH) MSH secretion

  5. corticotropin releasing hormone (CRH) ACTH secretion

  6. gonadotropic releasing hormone (GnRH) secretion of gonadotropic LH, FSH

  7. prolactin releasing hormone (PRH)

  8. dopamine (prolactin inhibiting hormone, PIH)
• Growth Hormone (GH)


  acts on most body cells

  overall metabolism and growth
• thyroid stimulating hormone (TSH)


  stimulates thyroid to secrete T3 and T4
• adrenocorticotropic hormone (ACTH)


  stimulates adrenal cortex to secrete cortisol and aldosterone (water and salt balance)
• melanocyte stimulating hormone (MSH)


  causes melanocytes to produce more melanin
• Gonadotropins (FSH and LH)

  luteinising hormone

  follicle stimulating hormone

  both regulate production of gametes and reproductive hormones

  testes: make testosterone and spermatogenesis (sperm)

  ovaries: make oestrogen and progesterone and oogenesis (oocytes)
• tropic vs non-tropic hormones

  tropic

  - released from APG

  - stimulates secretion of other hormones from target tissues

  e.g. LH and FSH act on other glands to release testosterone or oestrogen

  non-tropic:

  - initiates effect

  - secondary hormone
• list the anterior pituitary hormones (7)

  1. growth hormone

  2. thyroid stimulating hormone

  3. adrenocorticotropic hormone

  4. melanocyte stimulating hormone

  5. luteinizing hormone

  6. follicle stimulating hormone

  7. prolactin
• describe how the hypothalamus and posterior pituitary interact to go to target tissues

  - stimulus cause neurons in hypo to increase or decrease action potential frequency

  - tells hypo to make neuropeptides (these travel in axons of neurons)

  - AP's conducted along neurons from hypothalamus to PPG

  - axon terminals of neurons store neuro-hormones

  - AP's cause release of neurohormones into circulatory system

  - PPG hormones travel in blood stream to target tissue
• posterior pituitary hormones (2)

  1. antidiuretic hormone (ADH)

  2. oxytocin
• antidiuretic hormone (ADH)


  - stimulates increased reabsorption of Na and water from nephrons

  - lees, more concentrated urine produced

  water conserved by body

  - decreased BP stimulates ADH secretion

  - aka vasopressin (vasoconstrictor, increase BP)
• oxytocin


  - non tropic

  - uterine contractions during birth

  - ejection of milk from lactating breast (let down reflex)
• controlling hormone secretion (negative feedback)

  - APG secretes tropic hormone

  - travels in blood to target endocrine cell

  - hormone from target endocrine cell travels to its target

  - info travels ack to APG and hypo to say homeostasis has returned and to stop releasing hormone

  - hormone from target cell has opposite effect on hypothalamus and APG to decrease secretion of tropic hormone
• negative feedback

  response is opposite to original stimulus

  when homeostasis returns to normal negative feedback stops activity
• control of hormone secretion (positive feedback)


  - APG secretes tropic hormone

  - travels in blood to target endocrine cell

  - hormone from target cell travels to its target

  - hormone from target cell has positive feedback effect on hypothalamus and APG to increase secretion of tropic hormone
• positive feedback


  cycle continues until a big change occurs/stimulus is removed
• stimulation, transport and secretion of growth hormone

  stimulation:

  - stress

  - decrease blood glucose levels

  transport:

  - GNRH, GHIH travel through hypothalamohypophysial portal system to APG

  secretion:

  - increase GHRH and reduced GHIH act on APG

  - results in increased GH secretion
• effects of growth hormone

  negative feedback effect

  - increase aa uptake

  - increase protein synthesis

  - increase fat breakdown (energy source)

  - promote bone and cartilage growth

  - regulate blood levels of nutrients after a meal

  - stimulates liver and skeletal muscle to make IGF-1

  - increase glucose synthesis

  - reduce glucose usage

  - increase somatomedin secretion
• stimulation, transport and secretion of thyroid stimulating hormone (T3, T4)

  stimulation:

  - stress, hypothermia

  transport:

  - TRH released from neurons in hypo

  - passes through hypothalamohypophysial portal system to APG

  secretion

  - TRH cause APG cells to secrete TSH

  - passes through general circulation to thyroid gland

  - TSH cause increase synthesis and release of T3 and T4 into circulation

  - t3 and t4 act on target tissues to produce response
• T3 and T4 effects

  - increase metabolism

  - increase body temp

  - increase normal growth and development

  - inhibitory effect on TRH secretion from hypo and TSH from APG
• structure and function of thyroid gland

  - highly vascular

  - stores hormone

  - composed of follicles

  - follicular cells surrounding thyroglobulin/thyroid hormones

  - iodine and tyrosine necessary for t3 and t4 production

  - increases rate of glucose, fat, protein metabolism in many tissues

  - increases body temp

  - normal growth of many tissues
• cortisol releasing hormone


  - from hypothalamus

  - causes release of ACTH, which causes release of cortisol from adrenal cortex

  - causes aldosterone secretion from adrenal cortex

  - causes androgen (weak sex hormone)
• stimulation, transport and secretion of cortisol

  stimulation:

  - low blood glucose

  - stress

  transport:

  - CRH released from hypothalamic neurons in response

  - hypothalamohypophysial portal system to APG

  secretion:

  - CRH binds and stimulates cells that secrete ACTH

  - ACTH binds to membrane bound receptors on cells of adrenal cortex and stimulates secretion of glucorticoids

  - cortisol acts on target tissues
• effects of cortisol


  - increased lipid and protein breakdown

  - increase glucose levels

  - anti inflammatory effects

  - negative feedback effect

  - inhibits CRH release from hypothalamus and ACTH secretion from APG
• how is the adrenal medulla stimulated

  - stress, physical activity, low blood glucose levels act as stimuli to hypothalamus

  - results in increase sympathetic NS activity

  - increase AP frequency conducted through sympathetic division of autonomic NS

  - stimulates adrenal medulla to secrete epinephrine and norepinephrine into CVS

  - secretion of hormones prepares body for physical activity

  - short lived
• epinephrine and norepinephrine


  - aka adrenaline and noradrenaline

  - increases heart rate and contraction force

  - cause blood vessels to constrict in skin, kidneys, gastrointestinal tract

  - increase metabolic rate of skeletal muscles

  - decrease visceral organ functions

  - increase release of fatty acids from adipose tissue into the blood
• melanocyte stimulating hormone (MSH)

  - acts on receptors in skin cells (melanocytes)

  - stimulates melanin (colour pigment) in skin

  - role in regulating appetite and sexual behaviour

  - stimulated by MRH (e.g. sunlight)
• LH and FSH


  - GnRH from hypothalamus stimulates its secretion

  - from APG

  - gonadotropins: glycoprotein hormones promoting growth and function of gonads

  - both hormones regulate gamete production and reproductive hormones
• LH and FSH effects on testes and ovaries

  testes: testosterone

  - makes sperm

  - spermatogenesis

  - secondary sex characteristics

  ovaries: estrogen and progesterone

  - sex organ development and characteristics

  - menstrual cycle

  - pregnancy

  - makes oocytes
• feedback of LH and FSH

  - GnRH stimulates LH and FSH secretion

  - LH stimulates testosterone secretion from interstitial cells

  - FSH stimulations sustentacular cells of seminiferous tubules to increase spermatogenesis and secrete inhibin

  - testosterone stimulatory effect on sustentacular cells and on development of sex organs and secondary sexual characteristics

  - testosterone = negative feedback on hypo and pituitary to reduce LH and FSH

  - inhibin = negative feedback on APG to reduce FSH