e ndocrine vs. n ervous

Chemical Signals in Chemical Signals in Animals:Animals:

Endocrine System and Hormonal Control

Campbell Chapter 45

Nancy G. Morris

Endocrine vs. Nervous

The nervous system brings about immediateimmediate responses, but the endocrine system is slowerslower acting and regulates processes that occur over days or even months.

Hormones

Endocrine systems exert control through the use of hormones.hormones.

HormonesHormones are 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.

HormonesHormones are secreted into the bloodstream and regulate whole body processes like growth, reproduction, complex behaviors including courtship and migration.

Hormones

HormonesHormones influence the metabolism of their target cells by binding to receptor proteins within the cell or on the surface of the cell. (Figure 45.3)

Hormones

Exocrine systemsExocrine systems have ducts used for transport of substances directly into the body cavities: salivary glands

Endocrine systemsEndocrine systems are ductless and secrete hormones directly into body fluids: pituitary gland

Exocrine vs. EndocrineExocrine vs. Endocrine

The endocrine and the nervous systems are related

1) structurally 2) chemically 3) functionally

simultaneously maintaining homeostasis, physiology and other body processes.

Hormones

Neurosecretory cells: specialized nerve cells that secrete hormones located within endocrine organs and tissues. Figure 45.3

Hormones

Hormones

Several chemicals serve as both neurotransmitters and hormones.

Epinephrine, produced by the adrenal medulla, acts as the “fight or flight hormone” and a neurotransmitter.

Control

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

Control:- Antagonistic hormones work

in opposition to one other.- Insulin and glucagon

Hormonal ControlHormonal Control In Hydra, one hormone stimulates

growth and budding while inhibiting sexual reproduction.

Invertebrates exhibit a diversity of hormones which function in

1) homeostasis, 2)reproduction, 3)development, and 4)behavior.

Hormonal ControlHormonal 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 Control

Local regulators affect neighboring target cells

Histamine -- immune and regulatory responses

Interlukins – 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 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 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 SignalsChemical 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 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 Vertebrate Endocrine SystemSystem

Coordinates:1)metabolism,2)growth,3)development, and 4)reproduction.

Major Endocrine Organs

Functions of Vertebrate Hormones Some hormones have a

single action while other have multiple functions

Tropic hormones act on other endocrine glands

Functions of vertebrate hormones:

Table 45.1

HypothalamusHypothalamus

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 GlandPituitary Gland

- Located at the base of the hypothalamus

-Two lobes: anterior & posterior; numerous functions

- Figure 45.6

Anterior Pituitary GlandAnterior Pituitary Gland


Produces many different hormones

Regulated by factors of the hypothalamus

Four are tropic hormones that Four are tropic hormones that stimulate other endocrine glands stimulate other endocrine glands to synthesize and release their to synthesize and release their hormones: TSH, ACTH, FSH, LHhormones: TSH, ACTH, FSH, LH


Luteinizing Hormone (LH) Stimulates ovulation and corpus Stimulates ovulation and corpus

luteum formation in females luteum formation in females Stimulates spermatogenesis in Stimulates spermatogenesis in

malesmales


Follicle-Stimulating Hormone (FSH) Tropic hormone that affects the gonads In males, necessary for spermatogenesis In females, it stimulates ovarian follicle

growth


Growth Hormone (GH) Promotes growth

directly Stimulates production of

growth factors


Thyroid-Stimulating Hormone (TSH)

Tropic hormone that stimulates the thyroid gland to produce and secrete its own hormone


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 GlandPosterior Pituitary Gland

Posterior Pituitary GlandPosterior Pituitary Gland

Synthesized in hypothalamus Secreted from posterior pituitary Oxytocin – Oxytocin – induces uterine muscle induces uterine muscle

contraction; induces lactationcontraction; induces lactation Antidiuretic Hormone Antidiuretic Hormone – acts on – acts on

kidneys to increase water retention kidneys to increase water retention thus reducing urine volumethus reducing urine volume

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 hormonesThyroid hormones function in: 1) development 2) bioenergetics 3) homeostasis

ThyroidThyroid is on the ventral side of the trachea.

plays a major role in vertebrate development: participates in embryonic development

control metamorphosis in amphibians

blood pressure heart rate muscle tone digestion reproductive functions rate of O2 consumption &

metabolism (increases)

Thyroid gland maintains homeostasis in mammals including:

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

SSerious metabolic disorders result from deficiency or excess of thyroid hormones.

Negative Feedback System Figure 45.9 Hypothalamus secretes TRH Anterior Pituitary stimulated to produce

TSH TSH binds to receptors & T3 and T4

High levels of T3, T4, and TSH inhibit TRH

TThyroid hormonehyroid hormone secretion is regulated by hypothalamus and pituitary.

Parathyroid hormone Parathyroid hormone (PTH)(PTH)

balances blood calcium needs vitamin D to

function

Pancreas Endocrine Pancreas Endocrine TissuesTissues

Islets of Langerhans: Alpha cells secrete glucagon

Beta cells secrete insulin antagonistic hormones that

regulate blood glucose

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:– epinepherine – norepinepherine

Glucose is mobilized Heart rate is increased Bronchioles dilate

Adrenal glands: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

SteroidsSteroids

Androgens: male sex hormones Testosterone:

– Stimulate the development & maintenance of male reproductive systems

– responsible for secondary male sex characteristics

SteroidsSteroids Estrogens: female sex hormones

– Maintain the female reproductive system

– responsible for secondary sex characteristics

Progestins (Progesterone)– Preparation & maintainace of uterus

for reproduction Gonadotropins from anterior

pituitary (FSH and LH) control the synthesis of both androgens & estrogens

e ndocrine vs. n ervous

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