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Chemical Signals in Animals: Endocrine System and Hormonal Control. E ndocrine vs. N ervous. The nervous system brings about immediate responses, but the endocrine system is slower acting and regulates processes that occur over days or even months. Hormones.

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e ndocrine vs n ervous
Endocrine vs. Nervous
  • The nervous system brings about immediate responses, but the endocrine system is sloweracting and regulates processes that occur over days or even months.
  • Endocrine systems exert control through the use of hormones.
  • Hormonesare chemical messengers produced by ductless glands in one part of the body which travel through the bloodstream and exert their influence in another part of the body.
  • Hormones are secreted into the bloodstream and regulate whole body processes like growth, reproduction, complex behaviors including courtship and migration.
  • Hormones influence the metabolism of their target cells by binding to receptor proteins within the cell or on the surface of the cell.
exocrine vs endocrine
Exocrine vs. Endocrine
  • Exocrine systemshave ducts used for transport of substances directly into the body cavities: salivary glands
  • Endocrine systems are ductless and secrete hormones directly into body fluids: pituitary gland

The endocrine and the nervous systems are related

1) structurally

2) chemically

3) functionally

simultaneously maintaining homeostasis, physiology and other body processes.

  • Neurosecretory cells: specialized nerve cells that secrete hormones located within endocrine organs and tissues.
  • Several chemicals serve as both neurotransmitters and hormones.
  • Epinephrine, produced by the adrenal medulla, acts as the “fight or flight hormone” and a neurotransmitter.
  • Positive and Negative Feedback regulate mechanisms of both systems
  • Positive feed back: output intensifies and increases the likelihood of a response
  • Mammal milk production and release

- Antagonistic hormones work in opposition to one other.

- Insulin and glucagon

hormonal control
Hormonal Control
  • In Hydra, one hormone stimulates growth and budding while inhibiting sexual reproduction.
  • Invertebrates exhibit a diversity of hormones which function in

1) homeostasis,


3)development, and


hormonal control16
Hormonal Control
  • Chemical signals operate at virtually all levels of organization:
  • Local regulators
    • Intracellular
    • Cell to cell
  • Tissue to tissue regulators
  • Organ to organ regulators
  • Organism to organism (pheromones)
hormonal control17
Hormonal Control
  • Local regulators affect neighboring target cells
  • Histamine -- immune and regulatory responses
  • Interleukins– immune response
  • Growth factors – peptides and proteins that regulate the behavior of cells in growing and developing tissues
  • Prostaglandins – modified fatty acids released into interstitial fluid
hormonal control18
Hormonal Control
  • Binding of a chemical signal to a specific receptor protein triggers chemical events in the target cell that result in a change in that cell.
  • The response to a chemical signal depends on the number and affinity of the receptor proteins.
chemical signals
Chemical Signals
  • Chemical signals often bind to a specific protein receptor on the plasma membrane of the target cell
  • Because of their chemical nature, most signal molecules (peptides, proteins, glycoproteins) are unable to diffuse through the plasma membrane
chemical signals21
Chemical Signals
  • The binding of the signal molecule to a plasma membrane receptor initiates a signal transduction pathway, a series of events that converts the signal into a specific cellular response.
chemical signals22
Chemical Signals
  • A specific example is the binding on the polypeptide hormone insulin to the insulin receptor:
  • Insulin binding initiates a chain of events that accounts for the blood sugar lowering effects of insulin.
vertebrate endocrine system
Vertebrate Endocrine System




3)development, and


functions of vertebrate hormones
Functions of Vertebrate Hormones
  • Some hormones have a single action while other have multiple functions
  • Tropic hormones act on other endocrine glands
  • Region of the lower brain
  • Receives information from nerves throughout the body and brain
  • Initiates endocrine signals appropriate to the environmental conditions
  • Regulates the Pituitary Gland
pituitary gland
Pituitary Gland

- Located at the base of the hypothalamus

-Two lobes: anterior and posterior; numerous functions

anterior pituitary gland31
Anterior Pituitary Gland
  • Produces many different hormones
  • Regulated by factors of the hypothalamus
  • Four are tropic hormones that stimulate other endocrine glands to synthesize and release their hormones: TSH, ACTH, FSH, LH
anterior pituitary gland32
Anterior Pituitary Gland
  • Luteinizing Hormone (LH)
  • Stimulates ovulation and corpus luteum formation in females
  • Stimulates spermatogenesis in males
anterior pituitary gland33
Anterior Pituitary Gland
  • Follicle-Stimulating Hormone (FSH)
  • Tropic hormone that affects the gonads
  • In males, necessary for spermatogenesis
  • In females, it stimulates ovarian follicle growth
anterior pituitary gland34
Anterior Pituitary Gland
  • Growth Hormone (GH)
  • Promotes growth directly
  • Stimulates production of growth factors
anterior pituitary gland35
Anterior Pituitary Gland
  • Thyroid-Stimulating Hormone (TSH)
  • Tropic hormone that stimulates the thyroid gland to produce and secrete its own hormone
anterior pituitary gland36
Anterior Pituitary Gland
  • Adrenocorticotropin (ACTH) stimulates the adrenal cortex to produce and secrete its steroid hormones
  • Melanocyte-Stimulating Hormone (MSH) regulates the activity of pigment-containing skin cells
  • Endorphins inhibit pain perception
posterior pituitary gland38
Posterior Pituitary Gland
  • Synthesized in hypothalamus
  • Secreted from posterior pituitary
  • Oxytocin – induces uterine muscle contraction; induces lactation
  • Antidiuretic Hormone – acts on kidneys to increase water retention thus reducing urine volume
pineal gland
Pineal Gland
  • Small mass near the center of the brain
  • Produces melatonin
    • modified amino acid that modulates skin pigmentation
    • secreted only at night; larger amounts secreted in winter
    • Involved in regulation of biorhythms

Thyroid is on the ventral side of the trachea.

  • plays a major role in vertebrate development: participates in embryonic development
  • control metamorphosis in amphibians
thyroid gland maintains homeostasis in mammals including
Thyroid gland maintains homeostasis in mammals including:
  • blood pressure
  • heart rate
  • muscle tone
  • digestion
  • reproductive functions
  • rate of O2 consumption and metabolism (increases)
s erious metabolic disorders result from deficiency or excess of thyroid hormones
Serious metabolic disorders result from deficiency or excess of thyroid hormones.
  • Hyperthyroidism - high body temperature, sweating, weight loss, irritability, high blood pressure
  • Hypothyroidism – can cause cretinism in infants and weight gain, lethargy, and cold-intolerance in adults
  • Goiter - enlarged thyroid caused by a deficiency in iodine
t hyroid hormone secretion is regulated by hypothalamus and pituitary
Thyroid hormone secretion is regulated by hypothalamus and pituitary.
  • Negative Feedback System.
  • Hypothalamus secretes TRH 
  • Anterior Pituitary stimulated to produce TSH 
  • TSH binds to receptors and T3 and T4
  • High levels of T3, T4, and TSH inhibit TRH
parathyroid hormone pth
Parathyroid hormone (PTH)
  • balances blood calcium
  • needs vitamin D to function
pancreas endocrine tissues
Pancreas Endocrine Tissues
  • Islets of Langerhans:
  • Alpha cells secrete glucagon
  • Beta cells secrete insulin
  • antagonistic hormones that regulate blood glucose
if glucose homeostasis is unbalanced
If glucose homeostasis is unbalanced:
  • Type I diabetes mellitus (insulin-dependent diabetes)
  • Type II diabetes (non-insulin-dependent diabetes)
  • Both types untreated will result in high blood sugar:
    • Kidneys excrete glucose
    • More water is excreted
    • Fat is the major source of fuel for cell respiration.
adrenal glands
Adrenal Glands:
  • located on top of kidneys
  • Adrenal medula synthesizes catecholamines:
    • epinephrine
    • norepinephrine
  • Glucose is mobilized
  • Heart rate is increased
  • Bronchioles dilate
adrenal glands53
Adrenal Glands:
  • Adrenal cortex synthesizes and secretes corticosteroids as directed by ACTH from the anterior pituitary
    • Mineralocorticoids affect salt and water balance
    • Aldosterone stimulates kidney cells to reabsorb sodium ions and water
    • Glucocorticoids – promote glucose synthesis from noncarbohydrate substances such as proteins
  • Androgens: male sex hormones
  • Testosterone:
    • Stimulate the development and maintenance of male reproductive systems
    • responsible for secondary male sex characteristics
  • Estrogens: female sex hormones
    • Maintain the female reproductive system
    • responsible for secondary sex characteristics
  • Progestins (Progesterone)
    • Preparation and maintainace of uterus for reproduction
  • Gonadotropinsfrom anterior pituitary (FSH and LH) control the synthesis of both androgens and estrogens