All Free Biology MCQs with Answers

2131. Which of the following statements is incorrect about skeletal muscle fibers?

• A. They are multinucleated.
• B. They are 10 - 100 ?m in diameter & surrounded by sarcolemma
• C. They contain O2 storing molecules called hemoglobin.
• D. Their cytoplasm contains high concentration of carbohydrates

Explanation: Skeletal muscle fibres contain myoglobin, an oxygen-storing pigment, rather than haemoglobin, which is the oxygen-carrying protein in red blood cells. Students may choose a statement about multinucleation or fibre diameter, but those descriptions are typical features of skeletal muscle fibres.

2132. Why skeletal muscles are called striated muscles?

• A. They appear darker than smooth muscles by naked eye.
• B. Alternating dark and light bands appear on their surface when visualized by naked eye.
• C. Alternating dark and light bands appear on their surface when visualized via a microscope.
• D. All of these

Explanation: Skeletal muscle is called striated because microscopic examination shows repeating alternating dark A bands and light I bands. Students may choose b because the bands are visible as a pattern, but they are not normally resolved by the naked eye.

2133. The contraction of which of the following muscle fibers, is controlled by hormones?

• A. A smooth muscle
• B. A cardiac muscle
• C. A skeletal muscle.
• D. All of these

Explanation: Smooth muscle contraction is regulated involuntarily by autonomic signals, local factors, and hormones, rather than by conscious motor commands. Students may choose cardiac muscle because hormones influence heart rate, but cardiac contraction is generated intrinsically by the pacemaker system and only modulated by hormones.

2134. Sodium ions are "pumped" from a region of lower concentration to a region of higher concentration in the nerve cells of humans. This process is an example of

• A. Diffusion
• B. Passive transport
• C. Osmosis
• D. Active transport

Explanation: Moving sodium ions from lower to higher concentration requires energy from ATP and is therefore active transport, carried out by membrane pumps such as the sodium-potassium pump. Diffusion moves particles down their concentration gradient, which is the misunderstanding behind choosing option a.

2135. Which system links brain to every part of body?

• A. Nervous system
• B. Brain
• C. Spinal cord
• D. All of above

Explanation: The nervous system connects the brain with the rest of the body through sensory and motor neurons, allowing information to travel in both directions. The brain and spinal cord are important parts of this system, but neither one alone links the brain to every body part. Students may choose the spinal cord because it carries many nerve pathways, but peripheral nerves are also required.

2136. Dorsal root of spinal nerves contain only __________ ?

• A. Effectors neurons
• B. Receptor neurons
• C. Stimulators
• D. Detector neurons

Explanation: The dorsal root of a spinal nerve carries sensory, or afferent, fibres entering the spinal cord from receptors. Motor fibres leave through the ventral root, so students may choose effectors neurons by confusing the destination of motor impulses with the sensory input carried by the dorsal root.

2137. Human brain contains__________neurons.

• A. 10,000,00
• B. 100,000,000
• C. 100,000,000,000
• D. 1000

Explanation: The human brain contains approximately 86 billion neurons, which is commonly rounded in older exam material to about 100,000,000,000 neurons. This is a count of cells, not a percentage or a number of brain regions. Students may choose 100,000,000 because it is a large number, but it is far below the accepted estimate for total human brain neurons.

2138. Which of the following feature is not related to neuron?

• A. Conduction
• B. Regeneration
• C. Reflex
• D. Movement

Explanation: Regeneration is not a normal defining function of neurons, which are specialized mainly for receiving, conducting and transmitting impulses; most mature central neurons have very limited regenerative ability. Students may choose movement because motor neurons do not themselves contract muscles, but they control movement by transmitting impulses to muscles.

2139. Value of resting membrane potential is_____________?

• A. 0.03 V
• B. 0.05 V
• C. 0.07 V
• D. 0.09V

Explanation: The resting membrane potential of a typical neuron is about -0.07 V, meaning the inside is approximately 0.07 V more negative than the outside. Students may choose 0.05 V because membrane potentials vary among cells, but 0.07 V is the standard textbook value intended here.

2140. It is one of the convulsive disorders of nerves which are characterized by abrupt transient symptoms of motor, sensory, psychic or autonomic nature________________?

• A. Parkinson's disease
• B. Epilepsy
• C. Alzheimer's discease
• D. Dementia

Explanation: Epilepsy is a convulsive neurological disorder caused by abnormal, excessive electrical activity in the brain, producing temporary motor, sensory, psychic or autonomic symptoms. Students may choose Parkinson's disease because it also affects movement, but Parkinson's is primarily a progressive movement disorder rather than recurrent seizures.