Human Body — Hard Practice Quiz

A Biology cheat sheet for Human Body — every key formula with its symbols defined — plus a hard-level practice quiz to test recall.

Practice quiz

1. Describe the sequence of events involving the liver and pancreatic hormones that maintain blood glucose homeostasis, and identify the type of feedback mechanism primarily involved.

   • High blood glucose $\rightarrow$ pancreas releases insulin $\rightarrow$ liver stores glucose as glycogen $\rightarrow$ blood glucose decreases. This is positive feedback.
   • High blood glucose $\rightarrow$ pancreas releases glucagon $\rightarrow$ liver releases glucose $\rightarrow$ blood glucose increases. This is negative feedback.
   • High blood glucose $\rightarrow$ pancreas releases insulin $\rightarrow$ liver stores glucose as glycogen $\rightarrow$ blood glucose decreases. This is negative feedback.
   • Low blood glucose $\rightarrow$ pancreas releases insulin $\rightarrow$ liver breaks down glycogen $\rightarrow$ blood glucose increases. This is positive feedback.

   Answer: High blood glucose $\rightarrow$ pancreas releases insulin $\rightarrow$ liver stores glucose as glycogen $\rightarrow$ blood glucose decreases. This is negative feedback.

2. Trace the neural pathway and cellular events from sensing the heat to muscle contraction, identifying the type of nervous system control and the key neurotransmitter involved in the muscle response.

   • Sensory neuron $\rightarrow$ CNS $\rightarrow$ motor neuron releases dopamine at neuromuscular junction $\rightarrow$ muscle contracts. This is part of the autonomic nervous system.
   • Sensory neuron $\rightarrow$ CNS $\rightarrow$ motor neuron releases acetylcholine at neuromuscular junction $\rightarrow$ muscle contracts. This is part of the somatic nervous system.
   • Sensory neuron $\rightarrow$ CNS $\rightarrow$ interneuron $\rightarrow$ motor neuron releases GABA at neuromuscular junction $\rightarrow$ muscle contracts. This is part of the sympathetic nervous system.
   • Sensory neuron $\rightarrow$ CNS $\rightarrow$ motor neuron releases epinephrine at neuromuscular junction $\rightarrow$ muscle contracts. This is part of the parasympathetic nervous system.

   Answer: Sensory neuron $\rightarrow$ CNS $\rightarrow$ motor neuron releases acetylcholine at neuromuscular junction $\rightarrow$ muscle contracts. This is part of the somatic nervous system.

3. Explain how the kidneys, regulated by specific hormones, respond to severe dehydration to restore fluid balance, detailing the primary processes within the nephron affected.

   • Hypothalamus releases ADH $\rightarrow$ increases water reabsorption in collecting ducts $\rightarrow$ less urine volume. Aldosterone increases $\text{Na}^+$ secretion.
   • Hypothalamus releases ADH $\rightarrow$ increases water reabsorption in collecting ducts $\rightarrow$ less urine volume. Adrenal cortex releases aldosterone $\rightarrow$ increases $\text{Na}^+$ reabsorption in distal tubule.
   • Hypothalamus releases ADH $\rightarrow$ decreases water reabsorption in collecting ducts $\rightarrow$ more urine volume. Aldosterone increases $\text{K}^+$ reabsorption.
   • Adrenal medulla releases epinephrine $\rightarrow$ increases filtration rate in glomerulus $\rightarrow$ more urine volume.

   Answer: Hypothalamus releases ADH $\rightarrow$ increases water reabsorption in collecting ducts $\rightarrow$ less urine volume. Adrenal cortex releases aldosterone $\rightarrow$ increases $\text{Na}^+$ reabsorption in distal tubule.

4. Describe the primary sites of chemical digestion for the major macromolecules in this meal and how their breakdown products are absorbed and utilized for energy or storage.

   • Starch digestion begins in the stomach by pepsin; proteins are digested in the small intestine by amylase. Fats are absorbed directly into the bloodstream.
   • Starch digestion begins in the mouth by amylase; proteins are digested in the stomach by pepsin. Fats are emulsified by bile and digested in the small intestine, then absorbed into lacteals.
   • Proteins are digested in the mouth; starch is digested in the small intestine. Fats are digested in the large intestine.
   • All macromolecules are primarily digested in the large intestine, and their energy is stored exclusively as glycogen in muscles.

   Answer: Starch digestion begins in the mouth by amylase; proteins are digested in the stomach by pepsin. Fats are emulsified by bile and digested in the small intestine, then absorbed into lacteals.

5. Identify the primary endocrine glands and hormones involved in regulating blood calcium, and explain their coordinated actions to raise blood calcium levels, including their effects on bone cells.

   • Thyroid gland releases calcitonin, stimulating osteoblasts to build bone and increasing calcium reabsorption in kidneys.
   • Parathyroid glands release PTH, stimulating osteoclasts to break down bone and increasing calcium reabsorption in kidneys.
   • Adrenal glands release cortisol, which directly stimulates calcium absorption from the gut and inhibits osteoclast activity.
   • Pancreas releases glucagon, which signals the liver to release stored calcium into the blood.

   Answer: Parathyroid glands release PTH, stimulating osteoclasts to break down bone and increasing calcium reabsorption in kidneys.

6. Explain what "systolic pressure" represents in terms of heart activity and blood vessel dynamics, and describe the pathway blood takes immediately after leaving the left ventricle to reach systemic capillaries.

   • Systolic pressure is the pressure during ventricular relaxation. Blood leaves the left ventricle, enters the pulmonary artery, then capillaries.
   • Systolic pressure is the pressure during ventricular contraction. Blood leaves the left ventricle, enters the aorta, then systemic arteries, and finally systemic capillaries.
   • Systolic pressure is the pressure in the atria during contraction. Blood leaves the left ventricle, enters the vena cava, then systemic capillaries.
   • Systolic pressure is the pressure in the veins returning to the heart. Blood leaves the left ventricle, enters the right atrium, then systemic capillaries.

   Answer: Systolic pressure is the pressure during ventricular contraction. Blood leaves the left ventricle, enters the aorta, then systemic arteries, and finally systemic capillaries.

7. Describe the coordinated roles of B cells and Helper T cells in the primary adaptive immune response to this pathogen, including the specific functions of antibodies and the requirement for antigen presentation.

   • B cells directly kill infected cells, while Helper T cells produce antibodies. This response is immediate and non-specific.
   • B cells, after activation by Helper T cells and antigen binding, differentiate into plasma cells to produce antibodies. Helper T cells recognize antigens presented on MHC molecules and release cytokines to activate B cells.
   • Cytotoxic T cells produce antibodies, which then activate B cells to engulf pathogens. This process does not require antigen presentation.
   • Memory B cells are immediately activated to produce large amounts of IgE, leading to a rapid inflammatory response, without T cell involvement.

   Answer: B cells, after activation by Helper T cells and antigen binding, differentiate into plasma cells to produce antibodies. Helper T cells recognize antigens presented on MHC molecules and release cytokines to activate B cells.

8. Explain the hormonal events initiated by the hypothalamus that characterize the follicular phase, leading up to ovulation, and describe the primary effects of these hormones on the ovarian follicle and uterine lining.

   • High levels of progesterone from the corpus luteum stimulate FSH release, causing the endometrium to thicken.
   • GnRH from the hypothalamus stimulates the anterior pituitary to release FSH, which promotes follicle growth and estrogen production. Rising estrogen then thickens the endometrium.
   • LH surge from the posterior pituitary causes the corpus luteum to form, which then secretes estrogen to prepare for ovulation.
   • Estrogen levels are low, inhibiting GnRH and FSH, leading to the shedding of the uterine lining.

   Answer: GnRH from the hypothalamus stimulates the anterior pituitary to release FSH, which promotes follicle growth and estrogen production. Rising estrogen then thickens the endometrium.

9. Describe the hierarchical physiological response, starting from the organ system level, that maintains the animal's core body temperature, identifying the primary control center and the type of feedback mechanism involved.

   • The integumentary system detects cold, signaling the cerebrum to initiate shivering. This is positive feedback.
   • The hypothalamus detects cold, stimulating the muscular system to shiver and increasing metabolic rate. This is a negative feedback mechanism to restore temperature.
   • The adrenal glands release epinephrine, causing vasodilation and increased sweating to generate heat. This is positive feedback.
   • The kidneys increase water reabsorption to conserve heat, and the liver releases glucose to fuel shivering. This is a feed-forward mechanism.

   Answer: The hypothalamus detects cold, stimulating the muscular system to shiver and increasing metabolic rate. This is a negative feedback mechanism to restore temperature.

10. Explain the sequence of neural events that allows for the rapid withdrawal of the hand before the sensation of pain is consciously perceived, identifying the key structures involved and the type of neural pathway responsible for the initial withdrawal.

    • Sensory input travels directly to the frontal lobe for processing, which then sends a signal to the motor cortex for withdrawal. Pain is perceived simultaneously.
    • A reflex arc in the spinal cord, involving a sensory neuron, interneuron, and motor neuron, causes immediate hand withdrawal. The signal for pain travels separately to the brain (e.g., parietal lobe) for conscious perception.
    • The limbic system processes the sharp object stimulus, triggering an emotional response that causes withdrawal, followed by a signal to the cerebellum for pain perception.
    • The autonomic nervous system initiates the withdrawal reflex, with the sympathetic division causing muscle contraction, and the signal for pain being processed by the brainstem.

    Answer: A reflex arc in the spinal cord, involving a sensory neuron, interneuron, and motor neuron, causes immediate hand withdrawal. The signal for pain travels separately to the brain (e.g., parietal lobe) for conscious perception.