The Endocrine System

  • works in conjuction with the nervous system to maintain homeostasis (body balance)

  • able to access every cell in the body and have prolonged effects

  • are ductless and secrete their horomones directly into the blood

horomones: specialized chemical messengers that are active in low concentrations

→ may be effected by stress, excersize, emotions, gender, and age

classifications

  1. where they contact: target (a spefic site) vs. non target (many cells)

  2. work in sequence: tropic hormones cause the release of other horomones, and non-tropic horomones have a direct result on the effector (muscle/gland/organ)

  3. lipid/sterioid: goes through membrane or amino acid/protein/water soluble: need channel/carrier protein in the membrane

Hormone regulation

  • antagonistic hormones: hormones that work against eachother→ example blood sugar (insulin vs. glucagon

  • positive feedback: reinforcement increases further results→ example oxytocin

  • negative feedback: non tropic inhibits tropic hormone production→ example metabolism

the glands of the endocrine system:

the pituitary gland

  • considered the master gland

  • located in the brain below the hypothalamus

hypothalamus:

  • located in the brain

  • the physical link between the nervous and endocrine system

  • produces oxytocin and ADH which are then stored in the posterior pituitary

  • stimulates the pituitary via releasing hormones (RH)- example GnRh

    • hypothalamus → gondatropin releasing horomone → pituitary → gondatropin

    horomones produced in the hypothalamus:

    • andiuretic horomone: made in the hypothalamus, and is released when osmoreceptors shrink (dehydration)

      • directly affects water balance

      • makes nephrons more permeable to water, allowing water to be absorbed back into the body

        • hyposecretion of this horomone: diabetes insepedus

    • thyroid stimulating horomone (TSH): stimulates the thyroid gland to release its horomones

    • adrenocorticotropic horomone (ACTH): stimulates the adrenal cortex to release its horomones

    • human growth horomone (hGH): stimulates the growth of bones and muscles and organs by increasing the uptake of amino acids, the metabolism of fat, and the rate of cell division

      • hyposecretion: dwarfism

      • hypersecretion: gigantism, acromegaly

    • prolactin: causes milk production

    • oxytocin: causes uterine contractions

    • follical stimulating horomone (FSH): stimulates gametogenisis

    • lutenizing horomone (LH): stimulates ovulation and testosterone production

the thyroid gland

  • located in the neck (below the larynx)

  • controled by TSH which is secreted by the pituitary which in turn was stimulated by TRH from the hypothalamus

    • affected by levels of iodine in the body

  • thyroxin (t4): thyroids MVP

    • regulates metabolic rate by speeding up the rate of cell respiration and utilization of glucose and oxygen

    • increases the uptake of carbohydrates from the small intestine

      • hyposecretion: cretinism, goitree

      • hypersecretion: graves disease