Anatomy › Human Anatomy and Physiology
Your patient’s x-ray shows a “Terry Thomas/David Letterman” sign. This finding suggests injury to which structure?
Scahpolunate ligament
Anterior talofibular ligament
Radial collateral ligament of the wrist
Ulnar collateral ligament of the wrist
Triangular fibrocartilage complex
The "Terry Thomas/David Letterman" sign is specific to the articulations of the wrist, and involves injury to the scapholunate ligament. When this ligament is damaged, the scaphoid and lunate drift apart, creating a gap on x-rays reminiscent of the gap in Terry Thomas'/David Letterman's front teeth.
Which of the following neurotransmitters generally has an inhibitory effect on the postsynaptic neuron?
GABA
Dopamine
Serotonin
Norepinephrine
Glutamate
GABA is the only neurotransmitter to actively suppress the formation of an action potential when binding to the dendrites on the postsynaptic neuron.
Norepinephrine, dopamine, serotonin, and glutamate have various physiological effects in different regions of the body, but all acts to stimulate the formation of an action potential.
If an individual has a blood pH of 6.8, then they should __________.
breathe faster to remove excess CO2
breathe faster to intake excess O2
breathe slower to minimize loss of CO2
breathe slower to maximize use of O2
eat more acidic foods
Normal blood pH is about 7.4 in most tissues (it is a bit lower in veins since they carry waste products, which are acidic). To get back to the physiological set point of pH = 7.4, we want to remove the acid from the blood. The major blood buffer system is shown in the following equation:
As we know, carbon dioxide is one of the major byproducts of respiration, and is considered waste for our bodies. Combined with water and catalyzed by carbonic anhydrase, it is converted into carbonic acid. Carbonic acid is a weak acid and will partially dissociate into hydrogen ions and bicarbonate ions. Thus, overall, carbon dioxide and water yields acid (hydrogen ions). As a result, excess carbon dioxide in the blood will lower the pH.
In order to increase the pH, we must stop this equation from proceeding in the forward direction; thus, (remember Le Chatelier's principle) we must remove carbon dioxide from the left side. This will push the reaction in the reverse direction, quenching hydrogen ions (acid) and removing them from the blood, increasing blood pH back to normal.
Since we want to get rid of excess carbon dioxide, we breathe faster. Oxygen does not have any effect on blood pH. Furthermore, the atmospheric oxygen level (21%) is plenty for our bodies to utilize, as when we exhale there is about 15% oxygen left over, meaning we only use about 25% of the oxygen we breathe (this is why CPR works!).
In which part of bones does hematopoiesis take place?
Red marrow
Yellow marrow
Compact
Spongy
Periosteum
The correct answer is red marrow.
Hematopoiesis is the formation of blood cells, which is a function of red marrow. Red marrow forms red blood cells, white blood cells and blood platelets. The process beings with a stem cell that proliferates (reproduces rapidly), differentiates (becomes a specialized cell) and replicates (duplicates).
The other choices are all parts of bones, but have different functions/characteristics besides hematopoiesis. While red marrow contains the red and white blood cells and blood platelets, yellow marrow consists of mostly fat cells. Compact bones are hard and contain closely packed osteons that form a solid mass. The periosteum is the connective tissue covering the surface of a bone. Spongy bones are less dense than compact bone and are lighter than compact bones. It contains plates (trabeculae) of bone and cavities that contain the red marrow.
Which of the following is the start of the gastrointestinal tract?
Mouth
Stomach
Pharynx
Esophagus
The mouth is the start of the gastrointestinal tract. It is the site of both mechanical and chemical digestion via chewing, and saliva, respectively. Saliva contains the enzyme amylase that breaks down carbohydrates.
Which of the following support cells myelinates the axons of the peripheral nervous system?
Schwann cells
Oligodendrocytes
Ependymal cells
Astrocytes
There are two types of support cells that myelinate axons in the nervous system: oligodendrocytes and Schwann cells. The difference between these two cell types is their location in the nervous system. Oligodendrocytes myelinate axons in the central nervous system, and Schwann cells myelinate axons in the peripheral nervous system.
Ependymal cells secrete cerebrospinal fluid and astrocytes help form and regulate the blood-brain barrier.
The autonomic nervous system consists of three divisions.
Which of the following is not a division of the autonomic system?
Somatic
Sympathetic
Parasympathetic
Enteric
The autonomic nervous system (ANS) consists of a set of pathways to and from the central nervous system (CNS) that innervate and regulate smooth muscle, cardiac muscle, and glands. The ANS is distinct from the somatic nervous system, which innervates skeletal muscle. The ANS has three divisions the sympathetic, parasympathetic, and enteric nervous systems.
Which of the following does not serve an endocrine function?
Medulla oblongata
Heart
Kidney
Liver
Pancreas
Endocrine organs are capable of secreting hormone signals into the blood. The heart releases atrial-natriuretic hormone, which stimulates vasodilation to reduce blood pressure and affects kidney function. The liver releases insulin-like growth factor in response to growth hormone, which has direct effects on stimulating cell growth and division. The kidneys release renin, which acts to increase blood pressure via sodium retention. The pancreas secretes insulin and glucagon to regulate blood glucose concentration.
The medulla oblongata is located in the brain stem and regulates several vital functions, such as respiration and heart rate. It performs these actions via action potentials and innervation, rather than the secretion of hormones.
Which of the following is not a long bone?
Axis
Second metatarsal
Humerus
Fibula
The axis is the only bone listed that is not a long bone. The axis is the second cervical vertebra (C2) and is classified as an irregular bone.
What are the two gates of the voltage-gated channels along the axonal plasma membrane?
Activation and inactivation
Activation and reactivation
and
Positive and negative
The voltage-gated channels along the axonal plasma membrane open and close in response to changes in voltage, and may exist in three distinct states: deactivated, activated, and inactivated. While the axon is at rest, these channels are said to be deactivated; they are impermeable to sodium ions since their activation gates are closed. Once the neuron gets depolarized to the threshold of the voltage-gated sodium channels, the activation gates open, allowing the influx of sodium down its concentration gradient into the cell. During this time the channels are in their activated state. At the peak of the action potential the activation gates are still open, but the inactivation gates close, stopping the flow of sodium through the channels. The channels are in the inactivated state due to the cell becoming depolarized. Once the membrane potential drops back down towards resting, the inactivation gates open, and the activation gates close, thereby deactivating the channels again, until another action potential depolarizes the membrane.