Systems Biology and Tissue Types - MCAT Biological and Biochemical Foundations of Living Systems

With morphological changes, cells are most likely to be caught in regions with the smallest cross sectional area. Though capiallary beds have the highest TOTAL cross sectional area of any vessel bed in the body, individual capillaries are smaller than any other type of blood vessel. The result is that misshapen red blood cells, such as those in sickle cell anemia, can easily get stuck in capillaries.

The basic idea of cooperativity is that oxygen will bind with lower affinity once an oxygen atom is removed. Once you remove the first oxygen atom, the remaining ones are more likely to come off to supply tissue. This change is instigated by conformational changes in hemoglobin structure when an oxygen is removed.

High levels of carbon dioxide (CO2), low pH, and high temperatures all act to decrease oxygen's affinity toward human hemoglobin. Think of working muscle, which produces hot, acidic, high CO2 conditions in the blood; in this environment, it is important for hemoglobin to release transported oxygen to provide an aerobic environment to the muscle.

The plasma portion of the blood is the extracellular matrix that suspends the erythrocytes and lymphocytes traveling through circulation. The plasma contains water, proteins (chiefly albumin), electrolytes, and clotting factors (such as thrombin). Whole blood contains the cells, as well as thx extracellular plasma. Blood serum refers to blood plasma that has had the clotting factors removed.

When blood returns to the heart via the superior and inferior vena cavae, it is deoxygenated. It remains this way as it passes through the right atrium, the right ventricle, and the pulmonary arteries, through which it travels to the lungs to conduct gas exchange with the alveoli. Both the right ventricle and the pulmonary artery contain deoxygenated blood.

All of the other answer choices contain at least one component that carries oxygenated blood.

The scrotum is a bag of skin containing the testes. The importance of the scrotum is to regulate temperature because sperm synthesis in the testes must occur at a few degrees below body temperature. The testes are the location of sperm synthesis, androgen synthesis occurs in the interstitial cells, nourishment of the sperm takes place in the seminal vesicles, and lubrication occurs in the bulbourethral glands.

Gastrulation is the phase in embryogenesis in which the single-layered blastula is reorganized into a trilaminar structure called the gastrula. These three germ layers are called the endoderm, mesoderm, and ectoderm and give rise to individual organs during organogenesis.

The blastula is implanted into the uterine lining and the morula undergoes rapid cell divisions (cleavage) after fertilization of the zygote.

Most cells contain a complete genome, but not all genes are activated in each cell. Activation of particular genes produces appropriate protein function.

During the absolute refractory period, no action potential can occur. In the relative refractory period, an action potential can occur with more stimulation than is normally required.

Remember that an action potential starts with the diffusion of sodium into the cell. As more sodium enters the cell, more voltage gated sodium channels open up. This leads to depolarization of the cell. With a steady diffusion of sodium into the cell, the threshold stimulus will eventually be attained, and an action potential will be generated. It is the steady diffusion of sodium into the autorhythmic cells which results in an action potential.

The medulla oblongata, a part of the hindbrain, is primarily responsible for the control of ventilation and heart rate. The midbrain serves as a relay station for visual and auditory information. The cerebellum is responsible for balance and coordination. The corpus callosum is a connective tissue between the two hemispheres of the brain and allows for their intercommunication. The temporal lobes are primarily responsible for auditory processing. Therefore, the patient is most likely suffering from a damage to the medulla oblongata.

The cochlear and vestibular nerves join to form the auditory nerve. The crista are specialized hair cells that help in postural equilibrium and send information via the vestibular nerve. The incus is one of the three auditory bones (the others include the malleus and the stapes), the motion of which is part of sound reception. This information is transmitted via the cochlear nerve. Finally, the cochlea is the fluid-filled structure of the inner ear that translates movement into vibrations (also involved in sound reception). All of the given structures take part in transmitting information to the acoustic nerve.

Somatosensory neurons are most sensitive to mechanical force, temperature change, and tissue damage. Nociception is the processing of pain signals, which could result from any of these stimuli.

The sarcoplasmic reticulum contains a large amount of Ca2+ ions. This calcium is released from the sarcoplasmic reticulum when an electrical signal is sent to the cell. This release of calcium allows for contraction.

The proteins troponin and tropomyosin are attached to the actin filaments in sarcomeres. These proteins function to block the myosin-binding site on the actin protein, preventing unnecessary contraction. When calcium is released from the sarcoplasmic reticulum, it will attach to troponin. The troponin will then pull tropomyosin away from the actin filament, which allows myosin heads to attach and cause a contraction.

ATP binds myosin to release it from the actin binding site and is converted to ADP in order to adjust the myosin head to a high-energy position.

An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.

The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.

Cardiac muscle and skeletal muscle are both composed of sarcomeres. This layout gives both muscle types a striated appearance, alternating dark bands of myosin with lighter bands of actin. Only cardiac muscle has intercalated discs and skeletal muscle is the only type that is multinucleated. No muscle type is attached directly to bone, but skeletal muscle is linked to bone via tendons.

Skeletal muscle is under voluntary control, and are innervated by the somatic nervous system. Skeletal muscle is responsible for skeletal movement, such as swinging the arms or lifting the legs.

Cardiac and smooth muscle are under the control of the autonomic nervous system. Cardiac muscle contracts the heart autonomously, without additional neuronal input.

Volkmann canals connect different Haversian systems, allowing the osteocytes within their lacuna to communicate via chemical and cellular signalling.

Canaliculi form a "spiderweb" of tiny channels to facilitate communication between osteocytes within a single Haversian system, but do not permit communication between different osteons.