Endocrine System Overview and Hormonal Regulation

Inhibition of Natural Hormones by Steroids

• Steroid use can inhibit the production of natural hormones.
• Image depicts a very muscular man, likely due to steroid use, which can have detrimental effects on natural hormone production.

Endocrine System Overview

• Nervous and endocrine systems work together to coordinate bodily functions.
• Endocrine glands are scattered throughout the body, secreting hormones into the bloodstream.
• These glands, although tiny, play a crucial role in regulating many bodily functions.

Learning Outcomes

• Students should be able to compare and contrast the nervous and endocrine systems.
• Understand hormone function and the organization of endocrine glands.
• Identify hormone regulation mechanisms.
• Understand the relationship between the hypothalamus and pituitary glands.
• Describe the function of each hormone secreted by the pituitary gland.

Introduction to Endocrine Systems

• Nervous and endocrine systems work together for body function coordination.
• Endocrine glands are scattered throughout the body, secreting hormones into the blood.
• The small glands are extremely important for their roles.

Comparison of Nervous and Endocrine Systems

• Nervous system uses nerve impulses and neurotransmitters.
• Endocrine system uses hormones.
• Nervous system effects are short-lived and localized.
• Endocrine system effects are longer-lasting and widespread.
• Nervous system can stimulate or inhibit hormone release.

Summary of Nervous and Endocrine Systems

• Nervous uses electrical signals (action potentials).
• Endocrine uses chemical signals (hormones).
• Nervous system transmits quickly through neurons.
• Endocrine system transmits hormones via blood.
• Nervous system response is often voluntary or involuntary, but localized.
• Endocrine system response is always involuntary, often distant.

Functions of Hormones

• Regulate chemical composition and volume of internal environment (interstitial fluid).
• Control metabolism and energy balance.
• Manage smooth and cardiac muscle contraction.
• Regulate glandular secretion.
• Influence immune system activities.
• Control development and growth processes.
• Manage reproductive system operations.
• Establish circadian rhythms (body clock).

Types of Glands

• Exocrine glands secrete their products into ducts, reaching target sites.
• Examples include sweat, sebaceous, and mammary glands & digestive enzymes.
• Endocrine glands are ductless; hormones enter the bloodstream directly.

Endocrine Glands

• A list of major and minor endocrine glands.
• major glands, including pituitary, thyroid, parathyroid, adrenal, pancreas, minor glands, thymus, pineal, gonads (ovaries, testes), are mentioned.
• Locations are noted for some.

Other Hormone-Producing Structures

• Structures like kidneys, gastrointestinal mucosa, skin, liver, small intestine, placenta, and atrial muscle cells (ANP) produce hormones,
• But they are not traditionally considered part of the endocrine system.

Recap of Hormone-Producing Organ Systems

• Includes detailed descriptions of which organs secrete certain hormones, providing a concise recap.

Chemical Nature of Hormones

• sex Hormones and those from adrenzl cortex are classified as steroids.
• Most hormones are proteins or protein-derived.
• Receptors for protein hormones are on the cell membrane.
• Protein hormones are difficult to administer orally.
• Steroid hormones have receptors inside the cells.
• Steroid hormones are typically lipid-soluble.

Mechanisms of Hormone Action

• Hormones are carried throughout the body.
• Hormones affect only specific cells with matching receptors.
• Hormone binding to receptor triggers a response.
• Protein hormones use second messengers (like cyclic AMP).
• Steroid hormones directly influence gene expression.
• protein hormone that react with receptor sites on the surface of cells called first messenger
• cyclic AMP which brings about the action attributed to the hormone called second messenger

Summary of Hormone Action

• Diagrammatic summaries of steroid and non-steroid hormone action.
• Steroid hormones influence gene expression.
• Non-steroid hormones use second messengers.

Control of Hormone Secretion

• Hormones tend to be released in short bursts.
• Regulation by feedback mechanisms maintains homeostasis.
• Disorders can occur due to improper regulation.
• hormone secretion is regulated by , neural stimulus, humoral stimulus (changes in blood) and hormonal stimulus

Hormonal Stimuli, Neural Stimuli, Humoral Stimuli

• Hormone secretion is managed by neural, humoral, and hormonal stimuli.
• Neural stimuli involve nerve impulses.
• Humoral stimulus comes from changes in blood levels.
• Hormonal stimuli from other hormones' release.

Control of Hormones Secretion: Further Details

• Types of stimuli which regulate hormone release.
• Explicit examples for each type, like norepinephrine and epinephrine under stress.

Hormonal Regulation: Details on Feedback Mechanisms

• Negative feedback systems reverse a stimulus.
• Positive feedback mechanisms amplify the initial stimulus, often for temporary effects.
• Examples include calcium regulation and childbirth processes.
• negative feedback, Ca+ level controlled by parathyroid hormone. Too high, PTH secrete calci5onin to lower Ca+ level

Hypothalamus and Pituitary Gland

• The hypothalamus links the nervous and endocrine systems.
• It controls the pituitary gland through releasing and inhibiting hormones.
• The pituitary gland has anterior and posterior lobes.

Hypothalamus and Pituitary Gland: Detailed Info

• hyppthalamus major link between nervous and endocrine systems
• regulate all aspect of growth, development, metabolism and homeostasis

Hypothesis and Anterior Pituitary

• Neurosecretory cells of the hypothalamus release hormones into capillaries.
• The hormones move through the blood vessels to the pituitary.
• Releasing and inhibiting hormones affect anterior pituitary hormone secretion.
• receive input from thalamus -pituitary gland is attached to hypothalamus and consist of 2 lobes, anterior pituitary(adenohypophysis) and posterior pituitary (neurohypophysis)
• hormo.ne from them controlled by releasing and inhibiting hormones produce by hypothalamus

Anterior Pituitary Hormones

• Human growth hormone (hGH) stimulates growth of bones & muscle.
• Thyroid-stimulating hormone (TSH) controls thyroid hormone synthesis & release.
• Prolactin (PRL) promotes mammary gland development & milk production.

Anterior Pituitary Hormones (Continued)

• Follicle-stimulating hormone (FSH) influences egg and sperm production.
• Luteinizing hormone (LH) triggers ovulation and regulates sex hormones like estrogen & progesterone (in female). It stimulates testosterone (in males).
• Adrenocorticotropic hormone (ACTH) controls hormones released by adrenal glands.
• Melanocyte-stimulating hormone (MSH) impacts skin color and certain bodily functions.

Anterior Pituitary Hormones: Clinical Applications

• The lack of hGH in children causes dwarfism.
• Excessive hGH leads to gigantism in childhood and acromegaly in adults.

Posterior Pituitary Hormones

• Oxytocin and ADH are released from neurosecretory cells in the hypothalamus, stored and released by the posterior pituitary.
• Oxytocin targets smooth muscle in uterus and breasts
• in uterus, oxytocin stimulates uterine contractions -stimulate milk letdown.
• ADH influences water reabsorption in kidneys and minimizes water loss.

Posterior Pituitary Hormones: Clinical Applications

• Insufficient ADH can lead to Diabetes Insipidus.
• Excess ADH can lead to increased blood pressure.

Recap/Quiz – Endocrine System Review

• Summary questions and answers to reinforce key concepts about the endocrine system.