Biology Final Exam Study Guide: Endocrine Secretion, Circulation, Shock

UDR endocrine secretion axes; Thyroid and HPA axis as examples

The endocrine system uses axes to regulate hormone secretion, with the Thyroid and Hypothalamic-Pituitary-Adrenal (HPA) axes as key examples.

Thyroid Axis:

• Process: The hypothalamus releases Thyrotropin-Releasing Hormone (TRH), which stimulates the anterior pituitary to secrete Thyroid-Stimulating Hormone (TSH). TSH then prompts the thyroid gland to produce thyroid hormones.
• Feedback: Rising thyroid hormone levels inhibit TRH and TSH release, maintaining balance.

HPA Axis:

• Process: The hypothalamus secretes Corticotropin-Releasing Hormone (CRH), triggering the anterior pituitary to release Adrenocorticotropic Hormone (ACTH). ACTH stimulates the adrenal cortex to produce glucocorticoids.
• Feedback: Increased glucocorticoid levels inhibit CRH and ACTH secretion, ensuring homeostasis.

How do hormones elicit response once they reach their target tissues? How is this different for water- and fat-soluble hormones?

Hormones elicit responses in target tissues by interacting with specific receptors, and the mechanism varies based on the hormone's solubility:

1. Water-Soluble Hormones:

   These hormones, such as epinephrine, cannot pass through the cell membrane. They bind to receptors on the cell's plasma membrane.

   This binding activates intracellular second-messenger systems, often involving G proteins, which mediate the cell's response.

2. Lipid-Soluble Hormones:

   These include steroid and thyroid hormones, which can diffuse through the cell membrane.

   O They bind to receptors inside the cell, often in the nucleus, directly activating genes to synthesize new proteins.

Comparison Table: Hormone Solubility

What are the 3 means of stimulating an endocrine gland to secrete?

Humoral Stimuli:

o This involves the direct response to changing levels of ions or nutrients in the blood. For example, the parathyroid glands release parathyroid hormone (PTH) when calcium levels in the blood are low, which helps increase calcium levels.

Neural Stimuli:

o Hormone release is triggered by neural input. A classic example is the adrenal medulla, which secretes epinephrine and norepinephrine in response to action potentials from the sympathetic nervous system.

Hormonal Stimuli:

o This occurs when one hormone stimulates the release of another hormone. For instance, the hypothalamus releases hormones that prompt the anterior pituitary to secrete hormones, which then stimulate other endocrine glands like the thyroid or adrenal cortex.

What is the relationship between the hypothalamus and adeno- and neurohypophysis?

The hypothalamus and the pituitary gland work closely together to regulate various bodily functions through hormone release. Here's how they interact with the adenohypophysis (anterior pituitary) and neurohypophysis (posterior pituitary):

Neurohypophysis (Posterior Pituitary):

• o The posterior pituitary is an extension of the hypothalamus, composed of neural tissue.
• o It stores and releases hormones like oxytocin and antidiuretic hormone (ADH), which are synthesized in the hypothalamus.
• o These hormones travel down the hypothalamic-hypophyseal tract and are released into the bloodstream when hypothalamic neurons fire.

The anterior pituitary is glandular and connected to the hypothalamus via the hypophyseal portal system.

The hypothalamus secretes releasing and inhibiting hormones into this portal system, which regulates the anterior pituitary's hormone secretion.

Hormones like growth hormone (GH) and thyroid-stimulating hormone (TSH) are then released into the general circulation.

How do blood/serum concentration and half-life contribute to a hormone's effectiveness?

LIPID-SOLUBLE HORMONES WATER-SOLUBLE HORMONES Consist of All steroid hormones and thyroid hormone All amino acid-based hormones except thyroid hormone Sources Adrenal cortex, gonads, and thyroid gland All other endocrine glands Stored in secretory vesicles No Yes Transport in blood Bound to plasma proteins Usually free in plasma Half-life in blood Long (most need to be metabolized by liver) Short (most can be removed by kidneys) Location of receptors Usually inside cell On plasma membrane Mechanism of action at target cell Activate genes, causing synthesis of new proteins Usually act through second-messenger systems

UDR the differences between secretions from medulla and cortex of adrenals

Differences Between Secretions from the Adrenal Medulla and Cortex

The adrenal glands, located atop the kidneys, consist of two distinct parts: the adrenal cortex and the adrenal medulla, each producing different types of hormones.

1. Adrenal Cortex:

• . Hormones Produced: Steroid hormones, collectively known as corticosteroids.
• Types of Hormones:
  • Mineralocorticoids (e.g., aldosterone): Regulate sodium and potassium balance, affecting blood pressure and volume.
  • Glucocorticoids (e.g., cortisol): Involved in metabolism and stress response, increasing blood glucose and suppressing the immune system.
  • Gonadocorticoids (e.g., androgens): Contribute to sexual development and characteristics.
• Regulation: Hormone release is primarily stimulated by ACTH (adrenocorticotropic hormone).

2. Adrenal Medulla:

• Hormones Produced: Catecholamines, such as epinephrine(Heart) and norepinephrine(Blood vessel).
• . Function: These hormones enhance the fight-or-flight response, increasing heart rate and blood pressure.
• Regulation: Release is triggered by the sympathetic nervous system.

UDR the hypo- and hypersecretory conditions associated with the hormones released from the Big 3 glands discussed in class (pituitary, thyroid, adrenals)

Hypo- and Hypersecretory Conditions of the Big 3 Glands

1. Pituitary Gland:

• Growth Hormone (GH):
  • Hyposecretion: Leads to pituitary dwarfism in children.
  • . Hypersecretion: Causes gigantism in children and acromegaly in adults.
• Antidiuretic Hormone (ADH):
  • Hyposecretion: Results in diabetes insipidus, characterized by excessive urination and thirst.
  • . Hypersecretion: Causes the syndrome of inappropriate ADH secretion (SIADH), leading to water retention and hyponatremia.

2. Thyroid Gland:

• Thyroid-Stimulating Hormone (TSH):
  • . Hyposecretion: Can cause hypothyroidism, potentially leading to myxedema.
  • . Hypersecretion: Often results in hyperthyroidism, commonly due to Graves' disease.

3. Adrenal Glands:

• Cortisol (Glucocorticoids):
  • . Hyposecretion: Leads to Addison's disease, causing fatigue and low blood pressure.
  • Hypersecretion: Results in Cushing's syndrome, characterized by weight gain and high blood pressure.
• Aldosterone (Mineralocorticoids):
  • Hyposecretion: Also contributes to Addison's disease.
  • Hypersecretion: Causes aldosteronism, leading to hypertension and edema.

Hypersecretory too much hormone Hyposecretory not enough hormone

UDR the 3 circulatory routes in the body and their primary purpose(s)

Circulatory Routes in the Body

The human body has three main circulatory routes, each serving distinct purposes:

1. Pulmonary Circulation:

• Purpose: Transports oxygen-poor, carbon dioxide-rich blood from the right ventricle to the lungs. Here, gas exchange occurs, oxygenating the blood and removing carbon dioxide.

2. Systemic Circulation:

• . Purpose: Delivers oxygenated blood from the left ventricle to all body tissues, supplying nutrients and removing waste products.

3. Hepatic Portal Circulation:

• . Purpose: Directs blood from parts of the gastrointestinal tract to the liver for detoxification and nutrient processing before it enters the systemic circulation.

These routes ensure efficient distribution and exchange of gases, nutrients, and waste products throughout the body.

c/c the roles of the R/ L sides of heart; especially ventricles and how they differ functionally and anatomically

Roles of the Right and Left Sides of the Heart

The heart functions as a double pump, with each side serving distinct roles:

1. Right Side (Pulmonary Circuit Pump):

• Function: Pumps deoxygenated blood to the lungs for oxygenation.
• . Anatomy: The right ventricle has a thinner wall and a crescent shape, reflecting its role in the low-pressure pulmonary circuit.

2. Left Side (Systemic Circuit Pump):

• Function: Pumps oxygenated blood throughout the body, delivering nutrients and oxygen to tissues.
• . Anatomy: The left ventricle has a thicker wall and a round shape, enabling it to generate higher pressure needed for the systemic circuit.

Both ventricles pump simultaneously, but the left ventricle works harder due to the greater resistance in the systemic circuit. This anatomical and functional distinction is crucial for efficient blood circulation.

know and apply the implications of the "diagnostic triangle" involving heart/kidneys/lungs discussed in class.

The "diagnostic triangle" involving the heart, kidneys, and lungs highlights the interconnectedness of these organs in maintaining homeostasis and how dysfunction in one can affect the others.

1. Heart:

• Role: Pumps blood to supply oxygen and nutrients.
• Impact: Heart issues can lead to poor circulation, affecting kidney filtration and lung oxygenation.

2. Kidneys:

• Role: Filter blood, regulate blood pressure, and maintain electrolyte balance.
• . Impact: Kidney dysfunction can lead to fluid overload, increasing heart workload and causing pulmonary congestion.

3. Lungs:

• Role: Oxygenate blood and remove carbon dioxide.
• Impact: Lung issues can reduce oxygen supply, affecting heart function and kidney perfusion.

what is the definition of shock; know the various types.

Shock is a critical condition where blood perfusion to body tissues is inadequate, leading to insufficient oxygen and nutrient delivery. There are several types of shock, each with distinct causes and characteristics:

1. Hypovolemic Shock:

• Cause: Large-scale blood or fluid loss, such as from hemorrhage, severe vomiting, or burns.
• Signs: Rapid heart rate, weak pulse, and intense vasoconstriction. Blood pressure may initially remain stable but drops sharply if untreated.
• Management: Rapid fluid replacement is crucial.

2. Vascular Shock:

• . Cause: Normal blood volume but poor circulation due to extreme vasodilation.
• Types:
  • Anaphylactic Shock: Triggered by a severe allergic reaction causing widespread vasodilation.
  • Septic Shock: Caused by severe bacterial infections leading to systemic vasodilation.

3. Cardiogenic Shock:

• . Cause: Heart's inability to pump effectively, often due to myocardial damage from heart attacks.