The type of homeostatic regulation that maintains the balance of salt and water across membranes is called osmoregulation.
Missing Word
osmoregulation
Osmoregulation keeps the concentrations of water and dissolved ions in body fluids within a stable range. In humans the kidneys do most of this work by adjusting how much water and salt leave in urine.
Category: Homeostasis and Kidneys
Question 2
The microscopic functional units of the kidney that filter blood and form urine are called nephrons.
Missing Word
nephrons
Nephrons filter the blood, reabsorb useful substances such as water, glucose and needed ions, and secrete wastes, producing urine.
Category: Homeostasis and Kidneys
Question 3
The narrowing of blood vessels in the skin, which reduces heat loss to the environment, is called vasoconstriction.
Missing Word
vasoconstriction
Vasoconstriction sends less warm blood to the body surface, so less heat escapes. Its opposite, vasodilation, widens skin vessels to release heat.
Category: Homeostasis and Kidneys
Question 4
The wave-like contractions of smooth muscle that push food down the esophagus are called peristalsis.
Missing Word
peristalsis
Peristalsis is an involuntary, rhythmic squeezing of the muscular wall of the digestive tract that moves material in one direction, from the esophagus through the intestines.
Category: Digestion and Nutrition
Question 5
The acidic mixture of partly digested food and gastric juice that leaves the stomach is called chyme.
Missing Word
chyme
Chyme forms as the stomach churns food with acid and enzymes. It passes in small amounts into the small intestine, where digestion is completed.
Category: Digestion and Nutrition
Question 6
The first section of the small intestine, where bile and pancreatic juice enter, is the duodenum.
Missing Word
duodenum
The duodenum receives material from the stomach; there, pancreatic bicarbonate neutralizes stomach acid and bile emulsifies fats. It is followed by the jejunum and ileum.
Category: Digestion and Nutrition
Question 7
Organic nutrients needed only in small amounts, many of which act as coenzymes, are called vitamins.
Missing Word
vitamins
Vitamins are organic compounds the body needs in small quantities and generally cannot make in sufficient amounts, so they must come from the diet. Many assist enzymes as coenzymes. Minerals, by contrast, are inorganic.
Category: Digestion and Nutrition
Question 8
The dome-shaped muscle beneath the lungs that contracts and moves down during inhalation is the diaphragm.
Missing Word
diaphragm
When the diaphragm contracts and descends, the pressure around the lungs drops and air flows in. When it relaxes, air is pushed out.
Category: Circulation and Respiration
Question 9
Capillaries merge into small vessels called venules, which then join to form larger veins.
Missing Word
venules
Venules collect blood from capillary beds and carry it into veins for the return trip to the heart. On the other side of the capillary bed, small arteries called arterioles deliver the blood.
Category: Circulation and Respiration
Question 10
The small gland at the base of the brain whose anterior lobe releases growth hormone and thyroid-stimulating hormone is the pituitary gland.
Missing Word
pituitary
The pituitary gland has an anterior lobe that makes several hormones that control other glands and a posterior lobe that releases ADH and oxytocin. The hypothalamus controls its activity.
Category: Endocrine System
Question 11
The hormone released by the adrenal cortex that raises blood sodium levels is aldosterone.
Missing Word
aldosterone
Aldosterone causes the kidneys to retain sodium. It is released when blood sodium falls, blood volume or pressure drops, or blood potassium rises.
Category: Endocrine System
Question 12
The repeating contractile unit of a skeletal muscle fiber, in which thick and thin filaments alternate, is the sarcomere.
Missing Word
sarcomere
Sarcomeres are lined up end to end along each myofibril. When the filaments in each sarcomere slide past one another, the whole muscle fiber shortens.
Category: Bones and Muscles
Question 13
The longest, heaviest and strongest bone in the human body is the femur, in the thigh.
Missing Word
femur
The femur is the thigh bone of the lower limb, part of the appendicular skeleton. It supports body weight during standing and walking.
Category: Bones and Muscles
Question 14
The junction across which one neuron passes a signal to another cell, usually by releasing neurotransmitter, is called a synapse.
Missing Word
synapse
At a synapse, an action potential triggers the release of neurotransmitter, which diffuses across a narrow gap and binds receptors on the next cell.
Category: Nervous System
Question 15
The brain structure in the temporal lobe that is essential for forming new memories is the hippocampus.
Missing Word
hippocampus
The hippocampus, part of the limbic system, is needed to form new memories. Damage to it can leave a person unable to store new information.
Category: Nervous System