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Biology 12th MCQ PDF - All Chapters
NCERT Based MCQ with Explanation:
1. Which organ system coordinates the functions of various organs in the human body?
(a) Digestive system
(b) Circulatory system
(c) Neural and endocrine systems
(d) Respiratory system
Explanation: The neural and endocrine systems work together to maintain homeostasis by coordinating the functions of various organs.
2. What is the basic functional unit of the neural system?
(a) Ganglia
(b) Neuron
(c) Synapse
(d) Axon
Explanation: Neurons are specialized cells responsible for detecting, receiving, and transmitting stimuli, making them the basic units of the neural system.
3. Which part of the human neural system includes the brain and the spinal cord?
(a) Central neural system (CNS)
(b) Peripheral neural system (PNS)
(c) Autonomic nervous system
(d) Somatic nervous system
Explanation: The CNS, consisting of the brain and spinal cord, serves as the main site for information processing and control.
4. What is the function of afferent nerve fibers?
(a) Transmit impulses from CNS to muscles
(b) Transmit impulses from tissues to CNS
(c) Transmit signals between neurons
(d) Control involuntary organ actions
Explanation: Afferent nerve fibers carry sensory impulses from tissues and organs to the CNS.
5. The peripheral neural system (PNS) is divided into which two divisions?
(a) Central and somatic
(b) Sympathetic and parasympathetic
(c) Somatic and autonomic
(d) Afferent and efferent
Explanation: The PNS comprises the somatic system, which controls skeletal muscles, and the autonomic system, which regulates involuntary actions.
6. Which type of neuron has one axon and two or more dendrites?
(a) Bipolar
(b) Unipolar
(c) Multipolar
(d) Pseudo-unipolar
Explanation: Multipolar neurons, found in the cerebral cortex, have one axon and multiple dendrites, allowing complex processing.
7. What is the resting potential of a neuron?
(a) The state of neuron activity
(b) Potential during impulse transmission
(c) Electrical potential across the resting plasma membrane
(d) Zero potential across the membrane
Explanation: Resting potential is the difference in charge across the neuron membrane when it is not transmitting impulses.
8. Which ion's influx leads to depolarization of a neuron during impulse conduction?
(a) Potassium (K⁺)
(b) Sodium (Na⁺)
(c) Calcium (Ca²⁺)
(d) Chloride (Cl⁻)
Explanation: The rapid influx of Na⁺ ions into the neuron causes depolarization, triggering an action potential.
9. What is the function of the sodium-potassium pump in a neuron?
(a) Passive ion exchange
(b) Transmit nerve impulses
(c) Maintain ionic gradients
(d) Activate neurotransmitter release
Explanation: The sodium-potassium pump actively maintains the concentration gradients by moving 3 Na⁺ out and 2 K⁺ into the cell.
10. Which part of the neuron releases neurotransmitters?
(a) Dendrites
(b) Cell body
(c) Axon terminals
(d) Node of Ranvier
Explanation: Neurotransmitters are released from synaptic vesicles in the axon terminals to transmit signals to the next neuron.
Biology MCQ, Class-12, Chapter-9, Biotechnology: Principles and Processes11. Which part of the nervous system controls voluntary movements?
(a) Autonomic nervous system
(b) Sympathetic nervous system
(c) Somatic nervous system
(d) Parasympathetic nervous system
Explanation: The somatic nervous system transmits impulses from the CNS to skeletal muscles, controlling voluntary actions.
12. What is the primary role of dendrites in a neuron?
(a) Transmit impulses away from the cell body
(b) Connect neurons at synapses
(c) Transmit impulses towards the cell body
(d) Produce myelin sheath
Explanation: Dendrites receive signals and direct them toward the cell body for processing.
13. What is the significance of nodes of Ranvier?
(a) Generate neurotransmitters
(b) Speed up nerve impulse conduction
(c) Connect neurons in the CNS
(d) Protect the axon
Explanation: Nodes of Ranvier allow saltatory conduction, where impulses jump from node to node, increasing conduction speed.
14. What happens at a chemical synapse?
(a) Direct current flow between neurons
(b) Ion exchange across the synaptic cleft
(c) Neurotransmitters transfer impulses
(d) Electrical synapse formation
Explanation: At chemical synapses, neurotransmitters released into the synaptic cleft bind to receptors on the post-synaptic membrane.
15. What type of neurotransmitter is commonly involved in excitatory synapses?
(a) Serotonin
(b) GABA
(c) Glutamate
(d) Acetylcholinesterase
Explanation: Glutamate is a primary excitatory neurotransmitter, facilitating the generation of action potentials in post-synaptic neurons.
16. Which part of the brain is responsible for higher cognitive functions like memory and reasoning?
(a) Cerebellum
(b) Hypothalamus
(c) Cerebrum
(d) Medulla oblongata
Explanation: The cerebrum, particularly its association areas, is involved in memory, reasoning, and other higher cognitive functions.
17. Which structure connects the two cerebral hemispheres?
(a) Thalamus
(b) Corpus callosum
(c) Hypothalamus
(d) Limbic system
Explanation: The corpus callosum is a thick band of nerve fibers that enables communication between the left and right hemispheres.
18. What role does the thalamus play in the brain?
(a) Regulates emotions
(b) Controls involuntary actions
(c) Coordinates sensory and motor signaling
(d) Maintains circadian rhythms
Explanation: The thalamus acts as a relay center, processing and transmitting sensory and motor signals to appropriate brain regions.
19. Which brain part regulates body temperature and hunger?
(a) Cerebrum
(b) Pons
(c) Hypothalamus
(d) Midbrain
Explanation: The hypothalamus is crucial for maintaining homeostasis, including regulating body temperature and hunger.
20. What is the function of the limbic system?
(a) Motor coordination
(b) Emotional regulation and memory
(c) Visual and auditory processing
(d) Reflex actions
Explanation: The limbic system is involved in emotion, memory formation, and responses to environmental stimuli.
21. Which part of the brain controls balance and posture?
(a) Cerebrum
(b) Cerebellum
(c) Medulla oblongata
(d) Hypothalamus
22. What is the role of the midbrain?
(a) Relaying signals between the forebrain and hindbrain
(b) Controlling respiratory reflexes
(c) Regulating body temperature
(d) Processing auditory information only
23. What are the main components of the hindbrain?
(a) Thalamus and hypothalamus
(b) Cerebellum, pons, and medulla oblongata
(c) Midbrain and cerebral aqueduct
(d) Limbic system and amygdala
24. What is the primary function of pons in the brain?
(a) Relaying signals between different brain regions
(b) Generating reflex actions
(c) Controlling auditory functions
(d) Secreting hormones
25. Which neurotransmitter is released at neuromuscular junctions?
(a) Dopamine
(b) Acetylcholine
(c) Serotonin
(d) Glutamate
26. What characterizes myelinated nerve fibers?
(a) Presence of nodes of Ranvier
(b) Continuous conduction of impulses
(c) Slower conduction speed
(d) Lack of Schwann cells
27. What triggers neurotransmitter release in a neuron?
(a) Opening of potassium channels
(b) Depolarization of the presynaptic membrane
(c) Hyperpolarization of the postsynaptic membrane
(d) Activation of the sodium-potassium pump
28. Which type of synapse allows direct flow of electrical current between neurons?
(a) Chemical synapse
(b) Electrical synapse
(c) Mixed synapse
(d) Reflex synapse
29. What is the function of the medulla oblongata?
(a) Regulating emotions
(b) Controlling respiration and heart rate
(c) Maintaining equilibrium
(d) Processing auditory signals
30. What is the primary composition of grey matter in the brain?
(a) Myelinated axons
(b) Neuron cell bodies and dendrites
(c) Schwann cells
(d) Blood vessels