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caballero pt. 2
pre final assignment
| Question | Answer |
|---|---|
| What ions create an action potential, and how does their movement change the membrane voltage? | Sodium ions rush into the neuron first, causing the inside of the membrane to become less negative and then positive . A moment later, potassium ions move out of the cell, bringing the membrane potential back down toward resting levels . |
| What does acetylcholine do at the neuromuscular junction, and what happens if acetylcholinesterase is blocked? | Acetylcholine is released from the motor neuron and binds to receptors on the muscle fiber, triggering the muscle to contract. If acetylcholinesterase is inhibited, acetylcholine is not broken down, so the muscle stays stimulated. |
| What do troponin and tropomyosin do in muscle contraction, and how does calcium affect them? | Tropomyosin normally blocks the binding sites on actin so myosin cannot attach. When calcium binds to troponin, it moves tropomyosin out of the way, exposing the binding sites and allowing contraction to begin. |
| How do the sympathetic and parasympathetic systems differ in their effects on the body? | The sympathetic system increases heart rate, widens the pupils, and slows digestion. The parasympathetic system slows the heart, constricts the pupils, and promotes digestion and absorption. |
| How does negative feedback regulate hormone release? Give an example. | Negative feedback stops hormone production once the body reaches the needed level. For example, when thyroid hormone levels rise enough, the hypothalamus and pituitary reduce TSH and TRH release, preventing excess thyroid hormone. |
| How do arteries, veins, and capillaries differ structurally, and how does that relate to their function? | Arteries have thick, muscular walls to withstand high pressure. Veins have thinner walls and valves to help blood move back to the heart. Capillaries are only one cell thick, allowing easy exchange of gases, nutrients, and wastes with tissues. |
| How does the respiratory system move air in and out of the lungs during normal breathing? | When the diaphragm contracts, the thoracic cavity expands and pressure inside the lungs drops, pulling air in. When the diaphragm relaxes, the space decreases and lung pressure rises, pushing air out. |
| What affects hemoglobin’s affinity for oxygen, and how do pH and temperature change the curve? | High temperature, low pH, and high CO₂ decrease hemoglobin’s affinity for oxygen, causing it to release oxygen more easily. This shifts the oxygen dissociation curve to the right. |
| What is peristalsis, and how does it push food through the digestive tract? | Peristalsis is a wave-like pattern of smooth muscle contractions that squeezes food forward along the digestive tract. Circular muscles contract behind the food bolus while others relax ahead of it, moving it forward. |
| What do villi and microvilli do in the small intestine? | Villi and microvilli greatly increase the surface area of the small intestine, allowing more nutrients to be absorbed. They contain blood vessels and lymph vessels that quickly take in digested nutrients. |
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