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Chapter 18. The Endocrine System. communication between cells. mechanisms. direct cell-to-cell cell-to-cell (short distance) cell-cell cell-to-cell (long distance). gap junctions paracrine local chemicals neurotransmitters endocrine chemicals via bloodstream. Table 18-1.

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Chapter 18

The Endocrine System


communication between cells

mechanisms

direct cell-to-cell

cell-to-cell

(short distance)

cell-cell

cell-to-cell

(long distance)

gap junctions

paracrine

local chemicals

neurotransmitters

endocrine

chemicals via

bloodstream



Endocrine system

cells (tissues, organs) that produce chemical messengers (hormones) that travel via the bloodstream to have distant effects


Endocrine system

classes of hormones:

peptide:

lipid:

  • amino acid derivatives

  • polypeptides

  • eicosaniods

  • (from arachidonic acid)

  • steroids

  • (from cholesterol)



Endocrine system

receptors and mechanism of action

peptide hormones

receptors on cell surface

activate G proteins

use second messengers

(cAMP)

activates enzymes

alter cellular activity


Endocrine system

receptors and mechanism of action

steroid hormones

diffuse across membrane

receptors in cytoplasm

activate specific genes

alter cellular activity


100 keys (pg. 599)

“Hormones coordinate cell, tissue, and organ activities on a sustained basis. They circulate in the extracellular fluid and bind to specific receptors on or in target cells. They then modify cellular activities by altering membrane permeability, activating or inactivating key enzymes, or changing genetic activity.”


Endocrine reflexes

triggered by:

  • humoral stimuli

    • body fluid changes

  • hormonal stimuli

  • neural stimuli


  • Endocrine reflexes

    many are controlled by negative feedback

    simple - a single hormone

    complex - two or more

    several steps

    many are controlled by the hypothalamus


    the “master gland” of the endocrine system:

    pituitary gland

    posterior

    anterior

    fig 18-6


    pituitary gland

    produces 9 “peptide” hormones

    anterior

    *posterior

    ocytocin

    ADH

    TSH

    ACTH

    FSH

    LH

    prolactin

    GH

    MSH


    pituitary gland

    controlled

    by

    hypothalamus

    produces

    RH releasing hormones

    IH inhibiting hormones


    pituitary gland

    controlled

    by

    hypothalamus

    produces

    RH

    IH

    fig 18-7


    pituitary gland

    anterior

    TSH

    ACTH

    FSH

    LH

    prolactin

    GH

    MSH

    thyroid gland

    adrenal gland

    gamete development

    reproduction

    milk production

    growth

    pigment cells


    pituitary gland

    an example

    1

    2

    TSH

    thyroid gland

    3

    5

    4


    pituitary gland

    OT

    ADH

    controlled

    by

    hypothalamus

    produces

    RH

    IH

    ADH

    OT

    fig 18-7


    pituitary gland

    the “master gland”

    fig 18-9


    100 keys (pg. 604)

    “The hypothalamus produces regulatory factors that adjust the activities of the anterior lobe of the pituitary gland, which produces 7 hormones. Most of the hormones control other endocrine organs, including the thyroid gland, adrenal gland, and gonads. The anterior lobe also produces growth hormone, which stimulates cell growth and protein synthesis.”


    100 keys (pg. 604)

    “The posterior lobe of the pituitary gland releases two hormones produced in the hypothalamus; ADH restricts water loss and promotes thirst, and oxytocin stimulates smooth muscle contractions in the mammary lands and uterus (in females) and the prostate gland (in males).”


    other endocrine organs

    • thyroid glands

      • C-cells of thyroid gland

    • parathyroid glands

    • adrenal glands

      • cortex

      • medulla

    • pineal gland

    • pancreas

    • intestines, gonads, kidneys, adipose


    other endocrine organs

    thyroid glands

    produce thyroxine (T3, T4)

    affect all cells

     O2 use

     ATP production

     HR, bp

     erythropoiesis


    other endocrine organs

    • thyroid glands

      • C-cells of thyroid gland

    • parathyroid glands

    calcitonin

     blood [Ca2+ ]

    • PTH

    •  blood [Ca2+ ]


    100 keys (pg. 612)

    “The thyroid gland produces

    (1) hormones that adjust tissue

    metabolic rates and

    (2) a hormone that usually plays a minor

    role in calcium ion homeostasis by

    opposing the action of parathyroid hormone.”


    to here 4/18

    lec #39


    other endocrine organs

    • adrenal glands

    • cortex

    • medulla

    mineralocorticoids

    aldosterone retain Na+

    lose K+

    glucocorticoids

    hydrocortisone

    anti-inflammatory

    NE, E (Sympathetic ANS)


    100 keys (pg. 616)

    “The adrenal glands produce hormones that adjust metabolic activities at specific sites, affecting either the pattern of nutrient utilization, mineral ion balance, or the rate of energy consumption by active tissues.”


    other endocrine organs

    pineal gland

    produce melatonin

    timing of sexual maturation

    protect from free radicals

    set circadian rhythms


    other endocrine organs

    pancreas

    produces digestive enzymes

    contains islets

    produce (4) hormones

    insulin

    glucagon


    pancreas

    insulin

    released when blood [glucose]

    is greater than ~110 mg/dl

    most cells in the body have insulin receptor

    insulin dependent


    pancreas

    insulin

    most cells in the body have insulin receptor

    insulin dependent

    insulin causes these cells to

    5 glucose absorption

    5 glucose utilization

    4 blood [glucose] 6


    pancreas

    glucagon

    released when blood [glucose]

    is less than ~70 mg/dl

    stimulates:

    breakdown of glycogen

    breakdown of triglycerides

    production of glucose

    4 blood [glucose] 5


    100 keys (pg. 620)

    “The pancreatic islets release insulin and glucagon. Insulin is released when blood glucose levels rise, and it stimulates glucose transport into, and utilization by, peripheral tissues.

    Glucagon is released when blood glucose levels decline, and it stimulates glycogen breakdown, glucose synthesis and fatty acid release.”


    the “other” diabetes

    diabetes insipidus

    diabetes mellitus

    flow-through sweet

    What would make the urine sweet?

    Why would glucose be in the urine?


    diabetes mellitus

    causes

    • genetic

    • pathological conditions

    • injury

    • immune disorder

    • hormonal abnormality

    mutations leading to

    low insulin production

    abnormal insulin

    defective receptors


    diabetes mellitus

    types

    • type 1

    • insulin dependent (juvenile onset)

    • controlled by insulin injections

    • type 2

    • insulin independent (adult onset)

    • controlled by diet/lifestyle


    diabetes mellitus

    abnormally high blood [glucose]

    (hyperglycemia)

    so much glucose in the glomerular filtrate, that PCT can’t reabsorb it all…

    (transport proteins are saturated)

    … so some ends up in the urine

    glycosuria

    polyuria


    diabetes mellitus

    health problems

    much of the body thinks it is “starving”

    diabetic retinopathy

    diabetic neuropathy

    5 risk of MI (3x-5x)

    other vascular problems


    other endocrine organs

    intestines

    gonads

    kidneys

    adipose, thymus, heart

    digestive hormones

    reproductive hormones

    EPO, renin


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