General Physiology Lecture - Endocrine System

Adrenaline

Hormone that prepares body for actions, or excitement

Endocrine System

System that regulates energy levels, metabolism, growth, emotioms, and stress response. A collection of glands that secret hormones into the blood.

Growth Hormones

Hormone/s responsible for tissue repair

Endorphins

Hormone for the experience of happiness

Hormones

Chemical messengers secreted by the endocrine system; acts on specific target cells

Biosynthesis

Mechanisms of Hormonal signaling; Hormones are synthesized in soecific endocrine glands

Storage and Secretion

Mechanisms of Hormonal signaling; Hormones are stored and released into the bloodstream upon tsimulation

Transport

Mechanisms of Hormonal signaling; Hormones travel through bloodstream to reach their target cells

Recognition

Mechanisms of Hormonal signaling; Hormones bind to specific receptors either on the cell membrane, or inside the target cell

Signal of transduction and amplification.

Mechanisms of Hormonal signaling; The hormone-receptor interaction triggers a cascade of intracellular events

Cellular response

Mechanisms of Hormonal signaling; Target cell responds by altering its activity, such as producing proteins or enzymes

Feedback Regulation

Mechanisms of Hormonal signaling; The response is often regulated through feedback loops to maintain homeostasis

Thyroid gland

Gland that primarily affects metabolism

Parathyroids

Help regulate level of calcium in the blood

Testis

Secretes male sex hormones

Hypothalamus

Brain region controlling the pituitary gland

Pituitary gland

Secretes a significant portion of hormones, some of which control the action of other glands

Ovary

Secretes female sex hormones

Aldosterone

Hormone that regioates sodium and potassium balance, controlling blood pressure. From adrenal cortex

Steroid hormones

Lipid soluble hormones that need to enter the target cell in order to function. Includes sex hormones and adrenal gland hormones

Major classes of steroid hormones

Glucocorticoids (Cortisol), Mineralocorticoids (Aldosterone), Androgens (Testosterone), Estrogens (Estradiol)m Progestogens (Progesterone), Vitamin D (Calcitrol/Active Vitamin D3 - regulates calcium and bone metabolism)

Anabolic steroids

Synthetic substances related to the male sex hormones. Stimulate the production of proteins (used to build muscle), growth hormone, and testosterone

Abuse of anabolic steroids

Disrupts the normal production of hormones in the body. Results in infertility, hair loss, and heart attacks

Nonsteroid hormones

Water-soluble hormones that bind to cell surface receptors and use secondary messengers like cAMP to trigger cellular responses

G proteins

Signal transducers that convert signals from the outside into signals within the cell.

Glycoprotein-derived hormones

Thyroid-stimulating hormones (TSH) - Stimulates thyroid gland to produce T3&T4

Follicle-stimulating hormones (FSH) - Stimulates ovarian follicle growth and sperm production

Luteinizing hormone (LH) - Triggers ovulation amd testosterone production

All from Anterior pituitary

Amino acid derived hormones

Epinephrine (Adrenaline) - Adrenal Medulla - Increases heart rate, blood pressure, and energy supply (fight-or-flight response)

Norepinephrine (Noradrenaline) - Adrenal medulla - helps regulate blood pressure and alertness

Melatonin - Pineal gland - regulates sleep-wake cycle

Peptide hormones

Oxytocin, ADH/Vasopressin, Glucagon, Insulin

Protein hormones

Growth hormone, Prolactin (stimulates milk production in pituitary gland)

Hypothalamus and Pituitary Gland

Links the nervous and endocrin systems together.

Anterior pituitary gland hormones

Oxytocin and ADH

Posterior pituitary gland hormones

TSH, ACTH, FSH and LH, Growth Hormones, Prolactin, Endorphins

Neuroendocrine cells

function as both nerve cells and endocrine cell

Function of antiduretic hormone

Urine concentration, water reabsorption from distal and collecting tubules, spasm of smooth muscles (increase BP)

Effects of Diabetes insipidus or a nonfunctioning pituitary gland.

Kidney makes a lot of urine

Nephrogenic diabetes insipidus

Kidneys don’t respond to ADH hormone

Central diabetes insipidus

Pituitary gland doesn’t make enough ADH hormones

Oxytocin

Hormone that causes the contraction of smooth muscles and ejection milk from mother.

Neuroendocrine reflex

A response that consists from both the endocrine and nervous system. Release of milk is one.

Process of milk production in breasts.

1. Nursing stimulates nerve receptors in nipple

2. Sensory and spinal nerves carry impulses to the hypothalamus

3. Release of ocytoxin when stimulated

4. Oxytocin is transported by blood to mammary glands

Purposes of Thyroid Gland

1. Metabolism regulation - stimulates oxygen consumptioon in cells an dbreakdown of materials for energy

2. Growth and Development - essential for brain development and muscle function

3. Cardiovascular system - Increases heart rate and cardiac output

4. Nervous system function - helps regulate blood pressure

5. Body temperature regulation - controls heat production by increasing metabolic activity

6. Digestion and Gut Health - Supports proper digestive function and nutrient absorption

Hypothyroidism (Low T3 and T4 levels)

Underactive thyroid gland (due to iodine deficiency, Hashimoto’s disease, or pituitary disorders). Causes fatigue, weight gain, depression. Treatment is thyroid hormone replacement therapy (levothyroxine)

Hyperthyroidism (High T3 and T4 levels)

Overactive thyroid gland (due to Graves’ disease, thyroid nodules, or excessive iodine intake). Causes weight loss, rapid heartbeat, sweating, nervousness, and heat intolerance. Treatment involves antithyroid medications, radioactive iodine therapy, or surgery.

Goiter

Caused when iodine levels inthe body is low, as thyroid hormone production cannot increase in response to increasing TSH levels, causing the thyroid to enlargen and TSH levels to remain high.

Source of Progesterone

Mainly secreted by the corpus luteum after ovulation and later by the placenta during pregnancy.

Parts of Adrenal Gland

• Capsule - Outer covering

• Cortex

  • Zona glomerulosa - aldosterone

  • Zona fasciculata - Cortisol

  • Zona reticularis - Androgens

• Medulla - Epinephrine

Cushing’s Syndrome

Caused by excessive cortisol production, often due to prolonged steroid use or adrenal tumors. Symptoms include weight gain, high blood pressure, muscle weakness, and a “moon face” syndrome.

Addison’s Disease

A condition where the adrenal gland fail to produce enough cortisol and aldosterone. Symptoms include weight loss, fatigue, low blood pressure, hyperpigmentation, and salt cravings. It’s an autoimmune condition,

Estrogens

Regulates the menstrual cycle, promote the development of female secondary sexual characteristics, maintain bone density, and influences cardiovascular health.

Source of estrogen

Primarily secreted by ovarian follicles, corpus luteum (forms after ovulation), and, during Pregnancy, the placenta.

Progesterone

Prepares the endometrium for implantation, supports pregnancy, regulates the menstrual cycle, and influences mammary gland development.

inhibins (Inhibin A and Inhibin B)

Inhibit follicle-stimulating hormone secretion to regulate follicuar development and prevent excessive follicle maturation. Sourced from Granulosa cells

Relaxin

Facilitates cervical softening and relaxation of pelvic ligaments during pregnancy; may also play a role in inhibiting uterine contractions. Sourced from corpus luteum

Corpus luteum

Temporary endocrine structure in female ovaries that produces estrogen and progesterone. Develops after ovulation and regreses if fertilization does not occur.

Androgens

Serves as precursors for estrogen synthesis and contribute to libido and hair growth. Sourced from thecal cells.

Process of Ovulation

1. Low Estrogen and Progesterone signal the pituitary gland to release FSH

2. FSH matures the follicles in the ovary, which produces estrogen

3. Estrogens signals the pituitary to release LH, which leads to ovulation

4. Corpus luteum releases progesterone and estrogen

5. As the corpus luteum breaks down, less estrogen and progesterone are produced

Polycystic Ovary Syndrome

Hormonal disorder affecting women of reproductive age, leading to irregular ovulation, excess androgens (male hormones), and ovarian cysts. Assosciated with metabolic and reproductive disturbances

Key physiological features of Polycystic Ovary Syndrome

• Increased LH - stimulates excessive androgen production from the theca cells of the ovaries

• Low or nomal FSH

• Increased androgen

• Estrogen dominance

• Insulin resistance - leads to high insulin, stimulating androgen production and risk if Type 2 diabetes and obesity

• Ovarian Dysfunction - prevents regular ovulation, causing irregular or absent menstrual cycles. Forms polycystic ovaries due to immature follicle accumulation.

Testosterone

Regulates the development of male secondary sexual characteristics, spermatogenesis,and influences libido, bone density, and red blood cell production. Secreted mainly by Leydig cells.

Inhibin B

Inhibits follicle-stimulating hormones (FSH) from regulating spermatogenesis. Secreted by Sertoli cells within the seminiferous tubules.

Androstenedione and Dehydroepiandosteronen(DHEA)

Serves as precursors for testosterone synthesis. Produced in small amounts by Leydig cells,

Estradiol (E2)

Plays a minor role in male reproductive function by regulatig libido, spermatogenesis, and inegrity and maturation of sperm. Produced by leydig cells andconverted from testosterone by the enzyme aromatase in peripheral tissues.

Process of Testosterone regulation

1. Testosterone levels get too low

2. Release of gonadotropin releasing hormone (GnRH)

3. LH and FSH from Pituitary gland activate Testes

4. Testes produces testosterone and Inhibin B

Somatotropin

Growth hormones are also called _____

Growth hormones/somatotropin

Is secreted by the somatotropic cells of the anterior pituitary gland, and is regulated by Growth Hormone-Releasing Hormone (GHRH), which stimulates Growth Hormone secretion

Somatostatin (GHIH)

Inhibits HG secretion

Ghrelin

From the stomach. Stimulates GH release.

IGF-1

Insulin-like Growth Factor

Function of Growth Hormone

• Growth and Development - stimulates bone and cartilage growth by increasing chondrocyte and osteoblast activity. Works through IGF1, which is released by the liver,

• Metabolism and Regulation - increases protein synthesis, enhances fat breakdown, and reduces glucose uptake (anti-insulin effect)

• Organ and Tissue Maintenance - immune function and organ maintenance

• Neural and Cognitive Effects - helps with brain development, cognition, and mood regulation

Pituitary Dwarfism

GH Deficiency (in children)

Achomdroplasia

GH clinical condition characterized by abnormally short limbs with a regularly-sized body

Gigantism

Excessive GH (in children)

Acromegaly

Caused by GH deficiency. Characterized by a prominent forehead, nose, lips and tongue, and chin and jaw.

Prolactin and functions.

Hormone produced by women.

• Lactation

• Breast Development

• Regulation of Reproductive function - inhibits GnRH

• Metabolic and Immune Effects - Immune regulation and maternal behavior and bonding

Endorphins function

• Natural pain relief (Analgesia)

• Mood Regulation and Stress Reduction

• Enhancement of exercise performance

• Immune system modulation

• Regulation of appetite and sleep