Ch. 7: Endocrine System
What is a hormone, and how does it travel in the body?
A hormone is a chemical messenger produced by glands that travels through the bloodstream to target cells with specific receptors.
What is a receptive field, and how does its size affect sensory localization?
A receptive field is the physical area a sensory neuron responds to stimuli; smaller receptive fields allow for more precise localization.
What is the primary function of red blood cells (erythrocytes)?
To transport oxygen from the lungs to the body and carbon dioxide from the body to the lungs.
What are the four primary functions of the respiratory system?
Exchange of gases, regulation of body pH via CO2, protection from inhaled substances, and vocalization.
What is the primary function of cortisol in metabolism?
It prevents hypoglycemia by promoting gluconeogenesis, protein breakdown, and lipolysis.
What is the difference between water-soluble and lipid-soluble hormones?
Water-soluble hormones circulate freely in plasma and act on surface receptors, while lipid-soluble hormones travel bound to proteins and act on intracellular receptors.
What are nociceptors, and what types of stimuli activate them?
Nociceptors are pain receptors (free nerve endings) that respond to strong noxious stimuli such as chemical, mechanical, or thermal damage.
What is hematocrit, and what does a value of 38% indicate?
Hematocrit is the percentage of total blood volume made up of red blood cells; 38% means 38% of the blood is composed of RBCs.
What principle explains how air moves through the respiratory system?
Air flows from regions of higher pressure to lower pressure, driven by pressure gradients created by muscular activity.
Which hormones are released from the three zones of the adrenal cortex, and what are their general functions?
Zona glomerulosa releases mineralocorticoids (regulates mineral balance), zona fasciculata releases glucocorticoids (affects glucose metabolism), and zona reticularis releases weak androgens (masculinizing effects).
Explain how peptide hormones and steroid hormones differ in their mechanism of action.
Peptide hormones bind to surface receptors and use second messengers for rapid responses, while steroid hormones enter cells, bind intracellular receptors, and regulate gene expression more slowly.
Explain the gate-control theory of pain.
It states that non-painful input (like mechanical stimuli via Aβ fibers) can inhibit pain signals by activating inhibitory interneurons in the spinal cord, reducing pain perception.
Describe two structural characteristics of red blood cells and explain their significance.
RBCs are biconcave discs and lack a nucleus; this shape increases surface area for gas exchange, and the absence of a nucleus allows more space for hemoglobin.
Differentiate between external respiration and internal (cellular) respiration.
External respiration is gas exchange between the environment and body cells, while internal respiration is the cellular use of oxygen to produce CO2, water, and ATP.
Explain how thyroid hormone release is regulated through the hypothalamic-pituitary-thyroid (HPT) axis.
The hypothalamus releases TRH, which stimulates the anterior pituitary to release TSH, which then stimulates the thyroid gland to produce T3 and T4. These hormones provide negative feedback to both the hypothalamus and pituitary.
Describe the hypothalamic-pituitary-thyroid axis.
The hypothalamus releases TRH, which stimulates the anterior pituitary to release TSH, which then stimulates the thyroid gland to produce thyroid hormones.
Trace the olfactory pathway from receptor activation to conscious perception.
Olfactory receptors in the epithelium are stimulated, signals travel through olfactory nerves to the olfactory bulbs, then along the olfactory tract to the temporal lobe, where smell is consciously perceived.
Explain the three main steps of hemostasis.
1) Vasoconstriction reduces blood flow, 2) Platelet plug formation creates a temporary seal, 3) Clotting cascade forms a stable fibrin clot.
Explain the role of pleural fluid in lung function.
Pleural fluid provides lubrication for smooth lung movement and helps keep the lungs adhered to the thoracic wall.
Compare the effects of hyperthyroidism and hypothyroidism on the body.
Hyperthyroidism increases metabolic rate, heart rate, and heat production and can cause irritability and muscle weakness. Hypothyroidism decreases metabolic rate, heart rate, and protein synthesis, leading to fatigue, slowed thinking, and, in children, impaired growth.
Analyze how different types of hormone interactions (synergism, permissiveness, antagonism) regulate physiological processes.
Hormone interactions regulate responses by enhancing effects (synergism), requiring another hormone for full action (permissiveness), or opposing effects (antagonism), ensuring precise control of body functions.
Describe how taste information is transmitted to the brain, including the nerves involved.
Taste signals originate in taste buds and travel via the facial (VII), glossopharyngeal (IX), and vagus (X) nerves to the gustatory nucleus in the brainstem, then to the thalamus and primary gustatory cortex for perception.
How does hemoglobin contribute to both oxygen transport and the regulation of blood flow?
Hemoglobin carries oxygen in red blood cells and can bind/release nitric oxide, which causes vasodilation and improves blood flow and oxygen delivery.
How does airway structure (such as branching and diameter) influence airflow and resistance?
As airways branch, diameter decreases and resistance increases; reduced cartilage and increased smooth muscle allow for regulation of airflow but can also increase resistance.
Describe how parathyroid hormone, calcitriol, and calcitonin work together to regulate calcium homeostasis.
Parathyroid hormone and calcitriol increase blood calcium by promoting bone resorption, kidney reabsorption, and intestinal absorption. Calcitonin lowers blood calcium by inhibiting bone resorption and increasing calcium excretion by the kidneys.