MCAT Biology : MCAT Biological Sciences

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #201 : Mcat Biological Sciences

Proprioceptive stimuli differ from tactile stimuli in that __________.

Possible Answers:

tactile stimuli result in a general sensation, while proprioceptive signals the intensity of the sensation

tactile stimuli are transmitted through the spinal trigeminal pathway, while proprioceptive stimuli are transmitted through the main sensory trigeminal pathway

proprioceptive stimuli are internal and generated by body position and movement, while tactile stimuli are external

tactile neurons are able to differentiate a range of sensations, while proprioceptive neurons are specific to a particular quantity of force

Correct answer:

proprioceptive stimuli are internal and generated by body position and movement, while tactile stimuli are external

Explanation:

The only entirely true statement is that proprioceptive stimuli are internal and generated by body position and movement, while tactile stimuli are external. Proprioception is the awareness of the body in space, which allows animals to have the sensation of the placement of their bodies without needing to see what they are doing or feel their way. Tactile perception is the body's interaction with an external stimulus, such as pain, temperature, or pressure.

While most tactile stimuli are transmitted through the spinal trigeminal pathway, certain sensations use the main sensory trigeminal pathway.

Example Question #201 : Mcat Biological Sciences

The basal cells of the gustatory system __________.

Possible Answers:

will eventually differentiate into taste receptor cells

contain synaptic structures that transport sensory information

serve as structural support for neuro-epithelial cells

are dependent on ion channels to produce action potentials

Correct answer:

will eventually differentiate into taste receptor cells

Explanation:

Taste buds are bulb-shaped and open to the environment through a small pore. Chemical compounds bind to small cellular hairs of taste receptor cells to stimulate an action potential, relaying the taste to the brain. Basal cells are located at the bottom of the taste bud. As taste receptors die, basal cells will differentiate into new receptors to maintain the taste bud.

Example Question #202 : Mcat Biological Sciences

Receptors for salty and sour tastes are similar in that __________.

Possible Answers:

stimulation blocks the efflux of potassium ions

both involve G-protein coupling

both sodium and hydrogen cations are able to pass through sodium channels

an influx of chlorine and hydroxide anions causes hyperpolarization

Correct answer:

both sodium and hydrogen cations are able to pass through sodium channels

Explanation:

Options must be considered carefully here, as all answer choices relate to the gustatory system. The only similarity is that salty (sodium ion) and sour (hydrogen ion) tastes both involve the passing of these ions through sodium channels. (Hydrogen can also pass through proton transport channels.) While sour tastes can block the efflux of potassium ions, this is not true for salts, making this an incorrect answer choice.

Example Question #203 : Mcat Biological Sciences

Which two molecules would be expected to interact via mechanisms within the olfactory system?   

Possible Answers:

Ethane and benzene

Ethanol and ammonia

Methane and ethane

Ethanol and methane

Correct answer:

Ethanol and methane

Explanation:

Hydrophilic (polar) molecules are able to diffuse across the olfactory mucosa, while hydrophobic (nonpolar) molecules are first bound to transport proteins. We are looking for the answer choice that contains one polar and one nonpolar molecule. Ethanol is polar and methane is nonpolar, making this the correct answer choice.

Methane, ethane, and benzene are all nonpolar. Ethanol and ammonia are both polar.

Example Question #204 : Mcat Biological Sciences

Which of the following is an accurate statement about the olfactory mucosa?

Possible Answers:

Basal cells line the columnar epithelium and secrete olfactory mucosa

The olfactory and columnar neurons are the only cells which receive information about the external environment

Columnar cells surround olfactory neurons and periodically differentiate to replace them

Density of cilia on the olfactory neurons determines odor sensitivity

Correct answer:

Density of cilia on the olfactory neurons determines odor sensitivity

Explanation:

Olfactory neurons are the sole nerve cells that receive sensory information from the external environment. Basal cells will differentiate into neurons while columnar cells secrete mucosa. The true statement is that cilia density on the ends of the olfactory neurons determines odor sensitivity; the cilia contain many odor-specific receptor proteins.

Example Question #205 : Mcat Biological Sciences

Which of the following does not occur during transmission of a signal from a taste receptor to the brain?

Possible Answers:

Influx of chloride ions into the taste receptor

Influx of calcium ions into the taste receptor

Influx of sodium ions into the afferent nerve fiber

Release of neurotransmitter from the taste receptor

Correct answer:

Influx of chloride ions into the taste receptor

Explanation:

After taste receptor cells contact solutes in the saliva, action potentials cause a calcium influx through ion channels, which leads to the release of the neurotransmitter that induces an action potential in the afferent nerve. This action potential is carried to the brain for integration and interpretation.

Chloride ions do not enter the receptor during this process.

Example Question #206 : Mcat Biological Sciences

Which of the following is found in the middle ear?

Possible Answers:

Incus

Perilymph

Pinna

Semicircular canals

Correct answer:

Incus

Explanation:

The incus, along with the malleus and stapes, are three bones found in the middle ear, which act as a lever system to transmit sound waves to the oval window.

The pinna is simply the skin and cartilage component of the outer ear. The semicircular canals are found in the inner ear, and are responsible for adapting the head and body to positional changes, thus maintaining balance. The perilymph is the fluid found within the inner ear. 

Example Question #102 : Nervous System And Nervous Tissue

The malleus, incus and stapes are components of the __________.

Possible Answers:

middle ear

inner ear

cochlear structure

outer ear

Correct answer:

middle ear

Explanation:

The malleus, incus, and stapes are the three bones of the ear. Sound enters the external ear by using air as a medium. In the middle ear, vibrations from the air transition to vibrations through bone. The inner ear converts these bone vibrations to fluid vibrations in the cochlea, which converts the fluid vibrations to electrical stimuli for the nervous system.

Example Question #201 : Mcat Biological Sciences

Which of the following is not a component of the inner ear's maintenance of equilibrium?  

Possible Answers:

Movement of the crista is conveyed to brain centers via the vestibular nerve

Head movement causes displacement of crista in the ampulla

Fluid movement within the crista signals positional change to the vestibular apparatus

In the vestibular apparatus, fluid moves within the semicircular canals

Correct answer:

Fluid movement within the crista signals positional change to the vestibular apparatus

Explanation:

The vestibular apparatus is the name given for the entire inner ear structure that interprets position. It contains substructures such as the semicircular canals, the ampulla, and the crista. The crista are the specialized hair cells that respond to fluid movement; fluid does not move within the crista themselves.

All other listed answers are true.

Example Question #111 : Nervous System And Nervous Tissue

Which of the following structures is not responsible for transmitting information to the acoustic nerve?  

Possible Answers:

The cochlea

The incus

The crista

All of these structures play a role in transmitting information to the acoustic nerve

Correct answer:

All of these structures play a role in transmitting information to the acoustic nerve

Explanation:

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.

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