All Free Biology MCQs with Answers
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19844 questions · page 704 of 1985
7031. The central nervous system consists of the brain and the spinal cord. In general, tracts allow for the brain to communicate up and down with the spinal cord. The commissures allow for the two hemispheres of the brain to communicate with each other. One of the most important commissures is the corpus callosum. The association fibers allow for the anterior regions of the brain to communicate with the posterior regions. One of the evolved routes from the spinal cord to the brain is via the dorsal column pathway. This route allows for fine touch, vibration, proprioception and 2 points discrimination. This pathway is much faster than the pain route. From the lower limbs, the signal ascends to the brain via a region called the gracile fasciculus. From the upper limbs, the signal ascends via the cuneate fasciculus region in the spinal cord.Which of the following sentences correctly explains what happens when a person steps on a pin? I. Transmit to the brain rapidly II. Will utilise the gracile fasciculus region in the spinal cordIII. Will utilise the cuneate fasciculus region in the spinal cord
- A. I only
- B. II only
- C. III only
- D. None of these
Explanation: Fine touch, vibration, proprioception and 2 points discrimination all utilizes the dorsal column pathway. The upper region utilizes the cuneate fasciculus in the spinal cord while the lower region depends on the gracile fasciculus. According to the passage, these sensations are of the rapid pathway whereas other sensations such as pain is not as fast. The dorsal column pathway is heavily myelinated while the pain pathway is not as myelinated.
Correct answer: None of these7032. The central nervous system consists of the brain and the spinal cord. In general, tracts allow for the brain to communicate up and down with the spinal cord. The commissures allow for the two hemispheres of the brain to communicate with each other. One of the most important commissures is the corpus callosum. The association fibers allow for the anterior regions of the brain to communicate with the posterior regions. One of the evolved routes from the spinal cord to the brain is via the dorsal column pathway. This route allows for fine touch, vibration, proprioception and 2 points discrimination. This pathway is much faster than the pain route. From the lower limbs, the signal ascends to the brain via a region called the gracile fasciculus. From the upper limbs, the signal ascends via the cuneate fasciculus region in the spinal cord.Patient A has a tumor in his spinal cord. He is able to feel a fine touch above the waist. Below the waist he is unable to feel fine touch on either side. Where is the tumor most likely located? I. All levels of the spinal cordII. In the gracile fasciculus regionIII. In the cuneate fasciculus region
- A. II only
- B. I only
- C. I and II
- D. None of these
Explanation: Patient A is unable to feel a fine touch below the waist. A tumour in the gracile fasciculus region will prevent the signal from below the waist to reach the brain.
Correct answer: II only7033. Which part of the brain is responsible for controlling body temperature, and adjusting to external temperature conditions?
- A. Hypothalamus
- B. Thalamus
- C. Cerebrum
- D. Cerebellum
Explanation: The hypothalamus is responsible for cooling and heating mechanisms in the body, and thus is the correct answer.
Correct answer: Hypothalamus7034. A lesion to which brain region would result in a lack of coordinated movement?
- A. The left temporal lobe
- B. The hypothalamus
- C. The medulla oblongata
- D. The cerebellum
Explanation: The correct answer is D) The cerebellum, because its primary function is to regulate motor movements, coordination, posture, and balance, so a lesion here directly results in a lack of coordinated movement (ataxia) . The other options are incorrect: The left temporal lobe is mainly involved in hearing, memory, and language comprehension; the hypothalamus controls vital functions like hunger, thirst, and body temperature; and the medulla oblongata regulates autonomic functions such as breathing, heart rate, and blood pressure.
Correct answer: The cerebellum7035. Which of the following accurately describes white matter?
- A. White matter is denser than gray matter
- B. White matter is located in the central part of the spinal cord and is surrounded by gray matter
- C. White matter is only found in the peripheral nervous system
- D. White matter consists of myelinated axons in the central nervous system
Explanation: White matter refers to the white-colored myelin that surrounds the axons of neurons in the central nervous system. These axons are grouped together, creating distinct regions of white matter. In contrast, grey matter refers to the cell bodies of neurons in the central nervous system. The cell bodies are packed together into dense regions to create grey matter.
Correct answer: White matter consists of myelinated axons in the central nervous system7036. Which is the correct order of sequences during the knee-jerk reflex?
- A. Patella tendon stretches - sensory neuron - spinal cord - motor neuron - quadriceps contract
- B. Patella tendon stretches - spinal cord - sensory neuron - motor neuron - quadriceps contract
- C. Patella tendon stretches - sensory neuron - spinal cord -brain - motor neuron - quadriceps contract (reflex bypasses the brain)
- D. Quadriceps stretch - sensory neuron - spinal cord - motor neuron - patella tendon contracts
Explanation: During the knee-jerk reflex, the neural signal is initiated by the stretching of the patella tendon, which is transmitted via sensory neuron to the spinal cord. In turn, the signal is transmitted to the motor neuron, resulting in the contraction of quadriceps. Most importantly, the reflex bypasses the brain, allowing a speedy reaction of the body to the stimulus.
Correct answer: Patella tendon stretches - sensory neuron - spinal cord - motor neuron - quadriceps contract7037. Color blindness could be a result of the dysfunction of which type of cell?
- A. Vitreous humor cells
- B. Cones
- C. Rods
- D. Ciliary body cells
Explanation: Cones are responsible for the perception of colour. Three different types of cones exist, each type containing a different pigment specifically tuned to a wavelength or colour of light.
Correct answer: Cones7038. Which of the following somatic sensory neurons is responsible for the perception of pain?
- A. Mechanoreceptors
- B. Proprioceptors
- C. Nociceptors
- D. Photoreceptors
Explanation: Mechanoreceptors, propioreceptors, photoreceptors, and nociceptors are all classified as somatic sensory receptors, and are responsible for conveying information about the external environment to the brain.Nociceptors are able to detect and transmit the sensations of pain and extreme temperatures.
Correct answer: Nociceptors7039. Somatosensory neurons are most sensitive to which type(s) of stimulus?
- A. Nociception
- B. Temperature change and nociception
- C. Tissue damage
- D. Mechanical force, temperature change, and tissue damage
Explanation: The correct answer is D) Mechanical force, temperature change, and tissue damage. Somatosensory neurons are a broad class of sensory neurons that detect stimuli related to the body surface, including mechanical force (touch, pressure, vibration), temperature change (hot and cold), and signals related to tissue damage (pain, or nociception). Options A and B are incomplete because they only list one or two types of stimuli, failing to capture the full range of detection by somatosensory neurons. Option C is also incomplete, as tissue damage is just one category of stimulus.
Correct answer: Mechanical force, temperature change, and tissue damage7040. The touch receptor organs of the somatosensory system include _.
- A. Somatosensory neurons
- B. The skin, joint tissues, and muscles
- C. Joint tissues and muscles
- D. The skin only
Explanation: While somatosensory neurons are found within specialised touch receptors, the touch receptor organ for the tactile system is the skin. These sensors will detect stimuli for pressure, temperature change, and pain. Though these sensations can be detected in some internal regions of the body as well, the sensation of touch must be triggered by an external stimulus. As such, the receptors must have contact with the external environment (via the skin).
Correct answer: The skin only