Endocrine System and Sensory Pathways

Endocrine System

• Anterior Pituitary Gland Hormones:

  • Adrenocorticotropic Hormone (ACTH): Controls the release of glucocorticoids from the adrenal cortex.

  • Thyroid-Stimulating Hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones.

  • Luteinizing Hormone (LH): Triggers ovulation and testosterone production.

  • Follicle-Stimulating Hormone (FSH): Stimulates the growth of ovarian follicles and sperm production.

  • Growth Hormone (GH): Regulates growth and metabolism.

  • Prolactin (PRL): Promotes milk production in females.

• Posterior Pituitary Gland Hormones (from Hypothalamus):

  • Oxytocin: Stimulates uterine contractions during childbirth and milk ejection during breastfeeding.

  • Vasopressin (Antidiuretic Hormone, ADH): Regulates water balance in the body.

• Three Classes of Hormones:

  • Steroid Hormones:

  • Site of Synthesis: Adrenal cortex, gonads.

  • Receptors' Location: Intracellular (inside the cell).

  • Examples: Cortisol, Testosterone.

  • Peptide Hormones:

  • Site of Synthesis: Pituitary gland, pancreas.

  • Receptors' Location: Cell surface.

  • Examples: Insulin, Growth Hormone.

  • Amino Acid Derivatives:

  • Site of Synthesis: Thyroid, adrenal glands.

  • Receptors' Location: Cell surface (for catecholamines) or intracellular (for thyroid hormones).

  • Examples: Epinephrine, Thyroxine.

• Cholesterol as a Precursor:

  • Cholesterol is a precursor for the synthesis of steroid hormones such as cortisol, testosterone, and estrogen.

• Hormones of the Adrenal Medulla:

  • Epinephrine (Adrenaline): Increases heart rate, blood flow.

  • Norepinephrine (Noradrenaline): Increases alertness and prepares the body for stress.

• Description of Pathologies:

  • Addison's Disease: Hormone deficiency due to adrenal insufficiency; symptoms include fatigue, weight loss, low blood pressure.

  • Cushing's Disease: Excess cortisol production; symptoms include weight gain, high blood pressure, and easy bruising.

  • Graves' Disease: Overproduction of thyroid hormones; symptoms include anxiety, bloating, and exophthalmos (bulging eyes).

  • Paget's Disease: Abnormal bone remodeling; symptoms include enlarged bones, pain, and deformities.

  • Acromegaly: Excess growth hormone; symptoms include enlarged features, joint pain, and diabetes.

  • Adrenogenital Syndrome: Excess androgens leading to abnormal sexual development.

  • Cretinism: Severe hypothyroidism during infancy; symptoms include stunted growth, mental retardation.

  • Dwarfism: Short stature due to genetic or hormonal reasons; most commonly due to growth hormone deficiency.

  • Exophthalmos: Protrusion of the eyeballs, often associated with Graves' disease.

Sensory System

• Sensory Pathway Travel: All sensory pathways first travel to the thalamus before reaching the cerebral cortex; exception: olfactory nerve pathways (smell) go directly to the olfactory bulb.

• Two-point Discrimination Test: A sensory test determining the ability to perceive two closely spaced points as separate stimuli; often used to assess tactile acuity.

• Phasic Receptors: Receptors that adapt quickly to a stimulus and decrease the frequency of action potentials when the stimulus is constant.

• Nociceptors: Pain receptors that respond to potentially damaging stimuli by sending signals to the brain.

• Referred Pain: Pain perceived in an area other than the site of the actual injury or damage; often due to shared neural pathways.

• Chronic Pain: Persistent pain that lasts for an extended period, often defined as pain lasting longer than 3 to 6 months.

• Umami Taste: One of the five primary taste sensations, often described as savory; triggered by amino acids like glutamate.

• Primary Taste Sensations: There are five primary taste sensations: sweet, sour, salty, bitter, and umami.

• Middle Ear Structures:

  • Ossicles: The three tiny bones (malleus, incus, stapes) that amplify sound vibrations from the eardrum to the inner ear.

  • Function: Transmit sound vibrations from the air to the fluid-filled inner ear.

• Visual Pathway Structures:

  • Begins at the retina (photoreceptor cells) → optic nerve → optic chiasm → optic tract → lateral geniculate nucleus (LGN) → optic radiations → visual cortex (occipital lobe).

Anterior Pituitary Gland Hormones:

• Adrenocorticotropic Hormone (ACTH): Controls the release of glucocorticoids from the adrenal cortex, playing a crucial role in the body's response to stress by regulating metabolism and immune function.

• Thyroid-Stimulating Hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones, affecting processes such as growth and metabolism; regulated by the hypothalamic thyrotropin-releasing hormone (TRH).

• Luteinizing Hormone (LH): Triggers ovulation and stimulates testosterone production in males; regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus.

• Follicle-Stimulating Hormone (FSH): Stimulates the growth of ovarian follicles in females and promotes sperm production in males; its activity is important in the regulation of reproductive processes.

• Growth Hormone (GH): Regulates growth, metabolism, and body composition; stimulates growth in almost all tissues, including muscle and bone, through mechanisms involving insulin-like growth factors (IGFs).

• Prolactin (PRL): Promotes milk production in females; inhibited by dopamine and regulated during pregnancy and nursing.

Posterior Pituitary Gland Hormones (from Hypothalamus):

• Oxytocin: Stimulates uterine contractions during childbirth and triggers milk ejection during breastfeeding, also plays a role in social bonding and emotional responses.

• Vasopressin (Antidiuretic Hormone, ADH): Regulates water balance in the body by promoting water reabsorption in the kidneys and preventing excessive water loss through urine. High levels are released during dehydration.

Three Classes of Hormones:

1. Steroid Hormones:

   • Site of Synthesis: Adrenal cortex, gonads (testes and ovaries).

   • Receptors' Location: Intracellular (inside the cell).

   • Examples: Cortisol (stress response), Testosterone (male sex hormone).

2. Peptide Hormones:

   • Site of Synthesis: Pituitary gland, pancreas.

   • Receptors' Location: Cell surface (bind to membrane receptors).

   • Examples: Insulin (regulates blood sugar), Growth Hormone (stimulates growth).

3. Amino Acid Derivatives:

   • Site of Synthesis: Thyroid, adrenal glands.

   • Receptors' Location: Cell surface (for catecholamines) or intracellular (for thyroid hormones).

   • Examples: Epinephrine (adrenaline, fight or flight response), Thyroxine (regulates metabolism).

Cholesterol as a Precursor:

• Cholesterol is a precursor for the synthesis of steroid hormones such as cortisol, testosterone, and estrogen, essential for various physiological functions through their signaling pathways.

Hormones of the Adrenal Medulla:

• Epinephrine (Adrenaline): Increases heart rate and blood flow, enhances the body's fight-or-flight response by mobilizing energy.

• Norepinephrine (Noradrenaline): Increases alertness, prepares the body for stress by constricting blood vessels and raising blood pressure.

Description of Pathologies:

• Addison's Disease: Hormone deficiency due to adrenal insufficiency; symptoms include fatigue, weight loss, low blood pressure, and darkening of the skin (hyperpigmentation).

• Cushing's Disease: Excess cortisol production; symptoms include weight gain, high blood pressure, easy bruising, and psychological effects such as depression or anxiety.

• Graves' Disease: Overproduction of thyroid hormones; symptoms include anxiety, bloating, heat intolerance, and exophthalmos (bulging eyes).

• Paget's Disease: Abnormal bone remodeling; symptoms include enlarged bones, pain, and deformities, especially in the pelvis, skull, and spine.

• Acromegaly: Excess growth hormone; symptoms include enlarged features, joint pain, diabetes, and increased risk of cardiovascular issues.

• Adrenogenital Syndrome: Excess androgens leading to abnormal sexual development; may cause premature puberty or infertility.

• Cretinism: Severe hypothyroidism during infancy; symptoms include stunted growth, mental retardation, and developmental delays associated with thyroid hormone deficiency.

• Dwarfism: Short stature due to genetic or hormonal reasons; most commonly due to growth hormone deficiency, with various syndromes affecting height and growth.

• Exophthalmos: Protrusion of the eyeballs, often associated with Graves' disease; can lead to vision problems and discomfort in the eyes