Topic: Cerebral Circulation
Subtopic: Cerebral Blood Flow (CBF)
Keywords:
• Cerebral blood flow (CBF): The volume of blood passing through the brain per unit time.
• ml/min: Milliliters per minute, unit of flow rate.
• Autoregulation: Brain's mechanism to maintain constant CBF despite changes in blood pressure.
• Ischemia: Insufficient blood flow causing tissue damage.
• Hyperemia: Increased blood flow to tissues.
Lead Question - 2013 (September 2008)
Normal cerebral blood flow in ml/min ?
a) 55
b) 150
c) 750
d) 1000
Answer and Explanation:
Correct answer is c) 750. Normal cerebral blood flow in an adult is approximately 750 ml/min, supplying essential oxygen and nutrients to brain tissue. Autoregulatory mechanisms maintain this flow across a range of systemic blood pressures. Insufficient CBF leads to ischemia, while excessive flow may cause hyperemia or edema. (50 words)
1. Cerebral autoregulation maintains constant blood flow at what mean arterial pressure range?
a) 50-150 mmHg
b) 70-110 mmHg
c) 90-160 mmHg
d) 40-120 mmHg
Explanation:
Cerebral autoregulation preserves stable cerebral blood flow despite systemic blood pressure changes, within a mean arterial pressure range of approximately 50–150 mmHg. Outside this range, autoregulation fails, risking ischemia or hyperemia. (Answer: a)
2. Which condition decreases cerebral blood flow?
a) Hypercapnia
b) Hypotension
c) Fever
d) Exercise
Explanation:
Hypotension reduces cerebral perfusion pressure, impairing blood flow to the brain, risking ischemia. Hypercapnia and fever increase cerebral blood flow, while exercise generally increases systemic flow, also enhancing cerebral perfusion. (Answer: b)
3. The major factor increasing cerebral blood flow is:
a) Hypocapnia
b) Hypercapnia
c) Hypothermia
d) Hypoxia
Explanation:
Hypercapnia (elevated CO2 levels) dilates cerebral vessels, significantly increasing cerebral blood flow. Hypocapnia causes vasoconstriction and reduces flow. Hypoxia increases flow as compensatory, but hypercapnia remains the primary regulator. (Answer: b)
4. Clinical correlation: In head trauma, monitoring cerebral perfusion pressure is vital because:
a) Prevents seizures
b) Avoids ischemia
c) Controls temperature
d) Reduces intracranial pressure
Explanation:
Monitoring cerebral perfusion pressure ensures adequate blood flow, preventing ischemic injury in traumatic brain injury. Insufficient perfusion worsens neuronal damage, while elevated pressure risks herniation. Seizures and temperature control are secondary considerations. (Answer: b)
5. In ischemic stroke, cerebral blood flow is typically:
a) Increased
b) Normal
c) Severely reduced
d) Unchanged
Explanation:
Ischemic stroke results from arterial blockage, leading to a marked decrease in cerebral blood flow to the affected region, risking permanent neuronal damage unless promptly reperfused. (Answer: c)
6. The primary unit of cerebral blood flow measurement is:
a) ml/min
b) ml/100g/min
c) mmHg
d) L/min
Explanation:
Cerebral blood flow is typically expressed in ml/100g/min to account for brain mass differences, though absolute flow in ml/min is also used. (Answer: b)
7. Hyperemia in the brain is caused by:
a) Hypocapnia
b) Hypoxia
c) Low blood glucose
d) Low body temperature
Explanation:
Hyperemia results from vasodilation, triggered by hypoxia or increased metabolic demand. Hypocapnia causes vasoconstriction, reducing flow, while hypoglycemia and low temperature reduce metabolic rate and flow. (Answer: b)
8. Normal cerebral blood flow per 100 grams of brain tissue is approximately:
a) 20-25 ml/min
b) 50-55 ml/min
c) 10-15 ml/min
d) 60-70 ml/min
Explanation:
Normal cerebral blood flow is around 50-55 ml/100g/min, ensuring adequate oxygen and nutrient supply. Values below 20 ml/100g/min risk ischemia. (Answer: b)
9. Which area of the brain has the highest blood flow?
a) White matter
b) Basal ganglia
c) Gray matter
d) Brainstem
Explanation:
Gray matter has the highest cerebral blood flow due to high metabolic demands, approximately 80 ml/100g/min, compared to white matter. This supports active neuronal processing. (Answer: c)
10. In conditions of chronic hypertension, cerebral autoregulation curve:
a) Shifts left
b) Shifts right
c) Remains unchanged
d) Becomes steeper
Explanation:
Chronic hypertension shifts the autoregulatory curve rightward, meaning higher pressures are needed to maintain normal cerebral blood flow, increasing risk of hypoperfusion if aggressive BP lowering occurs. (Answer: b)
Topic: Reflex Actions
Subtopic: Withdrawal Reflex
Keywords:
• Withdrawal reflex: An automatic response to a painful stimulus to protect the body.
• Flexion: Bending a limb towards the body.
• Extension: Straightening a limb away from the body.
• Polysynaptic reflex: Reflex involving multiple synapses.
• Protective reflex: Prevents injury by removing body part from harm.
Lead Question - 2013 (September 2008)
What is seen in withdrawal reflex ?
a) Extension
b) Flexion
c) Extension followed by flexion
d) None of the above
Answer and Explanation:
Correct answer is b) Flexion. The withdrawal reflex is a protective polysynaptic reflex resulting in the flexion of a limb when exposed to a painful stimulus. This action helps rapidly remove the body part from harm. It involves sensory neurons, interneurons, and motor neurons. (50 words)
1. The withdrawal reflex primarily involves which type of neurons?
a) Sensory and motor only
b) Sensory, interneurons, and motor
c) Only motor neurons
d) Only sensory neurons
Explanation:
The withdrawal reflex is polysynaptic and involves sensory neurons detecting the painful stimulus, interneurons in the spinal cord transmitting the signal, and motor neurons triggering the flexor muscles to contract and withdraw the limb. (Answer: b)
2. Clinically, exaggerated withdrawal reflex indicates:
a) Normal response
b) Upper motor neuron lesion
c) Lower motor neuron lesion
d) Spinal shock
Explanation:
An exaggerated withdrawal reflex may suggest an upper motor neuron lesion, indicating disinhibition of spinal reflexes. It points toward a lack of supraspinal modulation. (Answer: b)
3. In the withdrawal reflex, the contralateral limb shows:
a) Flexion
b) Extension
c) No response
d) Tremors
Explanation:
During the withdrawal reflex, the crossed extensor reflex causes the contralateral limb to extend, providing balance and support when the affected limb withdraws from the painful stimulus. (Answer: b)
4. The withdrawal reflex is mediated at the level of the:
a) Brain
b) Spinal cord
c) Brainstem
d) Peripheral nerve
Explanation:
The withdrawal reflex is primarily mediated at the spinal cord level, allowing for rapid response without cortical involvement, which ensures speed and efficiency in protecting the body from harmful stimuli. (Answer: b)
5. In clinical testing, absence of the withdrawal reflex may indicate:
a) Upper motor neuron lesion
b) Lower motor neuron lesion
c) Normal finding
d) Hyperreflexia
Explanation:
An absent withdrawal reflex may suggest a lower motor neuron lesion, indicating damage to peripheral nerves or the spinal cord segment responsible for reflex arc, impairing the protective response. (Answer: b)
6. The speed of the withdrawal reflex is typically:
a) Very slow
b) Intermediate
c) Rapid
d) Variable
Explanation:
The withdrawal reflex is rapid to promptly remove the body part from painful stimuli, preventing injury. Its speed is enhanced by short reflex pathways and minimal synapses involved. (Answer: c)
7. Flexor muscles involved in withdrawal reflex are activated via:
a) Direct sensory neuron connections
b) Interneurons
c) Brain control
d) Hormonal signaling
Explanation:
Flexor muscles in the withdrawal reflex are activated via interneurons in the spinal cord, which transmit the pain signal from sensory neurons to motor neurons, causing the necessary contraction. (Answer: b)
8. Painful stimulus applied to the foot initiates the withdrawal reflex causing:
a) Flexion of leg
b) Extension of leg
c) No movement
d) Opposite limb movement only
Explanation:
A painful stimulus on the foot activates sensory receptors, initiating the withdrawal reflex. This leads to flexion of the affected leg to withdraw from harm, often coupled with contralateral limb extension for support. (Answer: a)
9. The withdrawal reflex is classified as:
a) Monosynaptic reflex
b) Polysynaptic reflex
c) Cranial reflex
d) Voluntary reflex
Explanation:
The withdrawal reflex is a polysynaptic reflex involving multiple interneurons and synapses, unlike monosynaptic reflexes like the knee jerk. This complexity allows for integration and modulation of the response. (Answer: b)
10. Which neurotransmitter is primarily involved in the withdrawal reflex?
a) Acetylcholine
b) Dopamine
c) Glutamate
d) GABA
Explanation:
Glutamate is the primary excitatory neurotransmitter involved in the withdrawal reflex, mediating signal transmission between sensory neurons, interneurons, and motor neurons in the spinal cord to activate muscle contraction. (Answer: c)
Topic: Cerebrospinal Fluid (CSF) Composition
Subtopic: Electrolyte Concentrations in CSF and Plasma
Keywords:
• Cerebrospinal fluid (CSF): Clear fluid surrounding brain and spinal cord, providing protection.
• Plasma: The liquid component of blood carrying cells and proteins.
• Electrolytes: Ions like Na+, K+, Cl-, Ca2+, important for cell function.
• Glucose: Primary energy source in body fluids.
• Bicarbonate (HCO3-): Important for pH buffering in body fluids.
Lead Question - 2013 (September 2008)
Which of the following has same concentration in CSF and plasma ?
a) Ca2+
b) HCO3
c) Glucose
d) Cl-
Answer and Explanation:
Correct answer is d) Cl-. Chloride ion concentration in CSF is approximately equal to plasma because it crosses the blood-brain barrier more freely compared to other ions. Ca2+, HCO3 and glucose are regulated and have different concentrations in CSF vs plasma to maintain CNS homeostasis. (50 words)
1. The main function of CSF is:
a) Oxygen transport
b) Nutrient delivery
c) Mechanical protection and chemical stability
d) Hormone transport
Explanation:
The primary function of CSF is to cushion the brain and spinal cord, maintain chemical stability, and remove waste products. It provides mechanical protection and optimal ionic environment for neuronal function. (Answer: c)
2. CSF is produced mainly by:
a) Arachnoid villi
b) Choroid plexus
c) Ependymal cells
d) Subarachnoid space
Explanation:
The majority of CSF is produced by the choroid plexus within the ventricles of the brain through selective filtration and active secretion mechanisms. (Answer: b)
3. Glucose concentration in CSF compared to plasma is generally:
a) Equal
b) Higher
c) Lower
d) Zero
Explanation:
CSF glucose concentration is typically about two-thirds of plasma glucose concentration due to restricted transport across the blood-brain barrier. (Answer: c)
4. In bacterial meningitis, CSF glucose level is usually:
a) Increased
b) Normal
c) Decreased
d) Unchanged
Explanation:
In bacterial meningitis, CSF glucose level typically decreases because bacteria consume glucose and inflammation impairs glucose transport across the blood-brain barrier. (Answer: c)
5. The blood-brain barrier allows easy passage of which ion into CSF?
a) K+
b) Na+
c) Cl-
d) Protein
Explanation:
Chloride ions (Cl-) can pass relatively freely across the blood-brain barrier, hence their concentrations in plasma and CSF are approximately equal. (Answer: c)
6. Bicarbonate concentration in CSF compared to plasma is:
a) Same
b) Lower
c) Higher
d) Zero
Explanation:
Bicarbonate concentration in CSF is slightly lower than in plasma due to selective transport, contributing to pH regulation in the CNS. (Answer: b)
7. Calcium concentration in CSF is generally:
a) Equal to plasma
b) Higher than plasma
c) Lower than plasma
d) Zero
Explanation:
Calcium concentration in CSF is lower than in plasma because tight regulation prevents excess calcium influx, protecting neurons from excitotoxicity. (Answer: c)
8. In which condition would CSF protein be markedly elevated?
a) Viral meningitis
b) Bacterial meningitis
c) Hypoglycemia
d) Hypocalcemia
Explanation:
CSF protein levels are markedly elevated in bacterial meningitis due to increased permeability of the blood-brain barrier and inflammation. (Answer: b)
9. The osmolarity of CSF compared to plasma is:
a) Lower
b) Higher
c) Equal
d) Variable
Explanation:
Osmolarity of CSF is nearly equal to plasma, maintained by regulated ion transport to preserve CNS homeostasis and prevent neuronal dysfunction. (Answer: c)
10. Which of the following is not a function of CSF?
a) Mechanical cushioning
b) Nutrient supply
c) Waste removal
d) Blood oxygen transport
Explanation:
CSF provides mechanical cushioning, supplies nutrients, and removes waste, but oxygen transport is primarily carried out by blood, not CSF. (Answer: d)
Topic: Sympathetic Nervous System
Subtopic: Control of Sweat Glands
Keywords:
• Sweating: Process of producing sweat to regulate body temperature.
• Norepinephrine: Neurotransmitter involved in sympathetic nervous responses.
• Epinephrine: Hormone and neurotransmitter involved in fight or flight response.
• Acetylcholine: Neurotransmitter in both parasympathetic and sympathetic nervous systems.
• Histamine: Chemical involved in allergic reactions and inflammation.
Lead Question - 2013 (September 2008)
Sweating is mediated by ?
a) Norepinephrine
b) Epinephrine
c) Acetylcholine
d) Histamine
Answer and Explanation:
Correct answer is c) Acetylcholine. Unlike most sympathetic postganglionic neurons that release norepinephrine, sweat glands are activated by acetylcholine acting on muscarinic receptors. This unique exception allows thermoregulatory sweating to occur, especially in response to increased body temperature or emotional stress. (50 words)
1. Sympathetic preganglionic fibers release:
a) Acetylcholine
b) Norepinephrine
c) Epinephrine
d) Dopamine
Explanation:
Sympathetic preganglionic fibers always release acetylcholine at synapses with postganglionic neurons, stimulating them to release norepinephrine or acetylcholine depending on the target tissue. (Answer: a)
2. Which receptor type mediates sweating?
a) Alpha-1 adrenergic
b) Beta-2 adrenergic
c) Muscarinic cholinergic
d) Nicotinic cholinergic
Explanation:
Sweating is mediated by muscarinic cholinergic receptors on sweat glands activated by acetylcholine, differing from typical adrenergic sympathetic responses. (Answer: c)
3. In hyperhidrosis, excessive sweating is primarily due to:
a) Increased norepinephrine
b) Increased acetylcholine
c) Decreased dopamine
d) Decreased epinephrine
Explanation:
Hyperhidrosis is commonly caused by overactivity of cholinergic sympathetic fibers, leading to excessive acetylcholine release and profuse sweating. (Answer: b)
4. Sweat glands controlled by sympathetic system are called:
a) Apocrine glands
b) Eccrine glands
c) Sebaceous glands
d) Ceruminous glands
Explanation:
Eccrine sweat glands, responsible for thermoregulation, are controlled by the sympathetic nervous system via acetylcholine release onto muscarinic receptors. (Answer: b)
5. Which is not a function of sweating?
a) Temperature regulation
b) Excretion of toxins
c) Lubrication of skin
d) pH regulation
Explanation:
Sweating primarily regulates body temperature and eliminates waste; however, lubrication of skin is a function of sebaceous glands, not sweat glands. (Answer: c)
6. Emotional sweating is mediated by which part of nervous system?
a) Parasympathetic
b) Somatic
c) Sympathetic
d) Central
Explanation:
Emotional sweating is mediated by the sympathetic nervous system via cholinergic stimulation of eccrine glands, independent of thermoregulatory needs. (Answer: c)
7. Histamine acts primarily in:
a) Sweat gland stimulation
b) Vasodilation and allergic reactions
c) Muscle contraction
d) Thermoregulation
Explanation:
Histamine is involved in allergic responses and vasodilation but does not play a direct role in mediating sweat gland activity. (Answer: b)
8. Which is true regarding acetylcholine's role in the ANS?
a) Only released in parasympathetic pathways
b) Released in both sympathetic and parasympathetic pathways
c) Only released in somatic motor neurons
d) Not involved in ANS
Explanation:
Acetylcholine is the neurotransmitter at all preganglionic synapses and at parasympathetic postganglionic synapses, as well as for sympathetic postganglionic innervation of sweat glands. (Answer: b)
9. Dysfunction in acetylcholine receptors causes which condition?
a) Myasthenia gravis
b) Hyperthyroidism
c) Diabetes mellitus
d) Hypotension
Explanation:
Myasthenia gravis is an autoimmune disorder targeting acetylcholine receptors, leading to muscle weakness and impaired neuromuscular transmission. (Answer: a)
10. Eccrine sweat gland stimulation is predominantly:
a) Adrenergic
b) Cholinergic
c) Dopaminergic
d) Serotonergic
Explanation:
Eccrine sweat glands are stimulated by cholinergic fibers in the sympathetic nervous system, releasing acetylcholine onto muscarinic receptors. (Answer: b)
Topic: Thalamus and Basal Ganglia
Subtopic: Thalamic Nuclei Functions
Keywords:
• Thalamic Nuclei: Relay centers in the brain transmitting sensory and motor signals.
• Basal Ganglia: Brain structures involved in movement control and coordination.
• Lateral Dorsal Nucleus: Thalamic relay nucleus involved in limbic system connections.
• Pulvinar: Thalamic nucleus involved in visual processing.
• Ventral Anterior Nucleus: Thalamic nucleus linked with motor control circuits.
• Intralaminar Nuclei: Group of thalamic nuclei involved in arousal, awareness, and basal ganglia function.
Lead Question - 2013 (September 2008)
Which thalamic nuclei can produce basal ganglia symptoms?
a) Lateral dorsal
b) Pulvinar
c) Ventral anterior
d) Intralaminar
Answer and Explanation:
Correct answer is d) Intralaminar. The intralaminar thalamic nuclei are involved in connecting the basal ganglia with the cortex and play a critical role in modulating motor function and awareness. Lesions in these nuclei can lead to symptoms mimicking basal ganglia dysfunction such as movement disorders or altered consciousness. (50 words)
1. The basal ganglia includes all except:
a) Caudate nucleus
b) Putamen
c) Thalamus
d) Globus pallidus
Explanation:
Thalamus is not part of the basal ganglia but acts as a relay station, whereas caudate, putamen, and globus pallidus are core basal ganglia structures involved in motor control. (Answer: c)
2. Lesion in ventral anterior nucleus causes:
a) Sensory loss
b) Movement disorder
c) Visual impairment
d) Hearing loss
Explanation:
Ventral anterior nucleus is part of the motor thalamus and its lesion typically results in movement disorders due to disrupted motor control pathways. (Answer: b)
3. Which pathway connects basal ganglia to cortex via thalamus?
a) Corticospinal tract
b) Corticothalamic pathway
c) Pallidothalamic tract
d) Spinothalamic tract
Explanation:
Pallidothalamic tract connects globus pallidus of basal ganglia to the thalamus, modulating motor signals relayed to the cortex. (Answer: c)
4. Lesions in intralaminar nuclei cause:
a) Aphasia
b) Basal ganglia symptoms
c) Cerebellar ataxia
d) Visual field defects
Explanation:
Intralaminar nuclei are connected to basal ganglia circuits; damage can cause movement disorders resembling basal ganglia disease. (Answer: b)
5. Pulvinar nucleus mainly affects:
a) Motor function
b) Visual processing
c) Sensory perception
d) Speech production
Explanation:
Pulvinar nucleus is primarily involved in visual processing and higher visual functions, not basal ganglia symptoms. (Answer: b)
6. Lateral dorsal nucleus connects primarily with:
a) Motor cortex
b) Limbic system
c) Visual cortex
d) Brainstem
Explanation:
Lateral dorsal nucleus is part of the limbic thalamic group, involved in emotional and memory functions, not basal ganglia symptoms. (Answer: b)
7. Basal ganglia symptoms include:
a) Bradykinesia
b) Aphasia
c) Hemianopia
d) Anosmia
Explanation:
Bradykinesia, or slowed movement, is a cardinal feature of basal ganglia dysfunction due to impaired modulation of motor circuits. (Answer: a)
8. Intralaminar nuclei receive input from:
a) Cerebral cortex
b) Brainstem reticular formation
c) Cerebellum
d) Peripheral nerves
Explanation:
Intralaminar nuclei receive extensive input from brainstem reticular formation and basal ganglia, crucial for arousal and motor coordination. (Answer: b)
9. Thalamic syndrome includes:
a) Motor weakness
b) Sensory loss with pain
c) Visual field defects
d) Aphasia
Explanation:
Thalamic syndrome is typically characterized by contralateral sensory loss with severe pain due to lesions in thalamic sensory relay nuclei. (Answer: b)
10. Basal ganglia is primarily involved in:
a) Memory processing
b) Voluntary motor control
c) Visual acuity
d) Hearing perception
Explanation:
Basal ganglia play a key role in voluntary motor control, movement initiation, and coordination, not in sensory processing like vision or hearing. (Answer: b)
Topic: Cerebellum
Subtopic: Cerebellar Nuclei Functions
Keywords:
• Cerebellar Nucleus: A deep collection of nerve cells in the cerebellum that processes input and output signals.
• Caudate Nucleus: Part of basal ganglia involved in motor control and learning.
• Subthalamic Nucleus: Basal ganglia structure involved in movement regulation.
• Fastigial Nucleus: A deep cerebellar nucleus involved in balance and posture control.
• Putamen: Basal ganglia nucleus important for motor skills.
Lead Question - 2013 (September 2008)
Which of the following is a cerebellar nucleus?
a) Caudate nucleus
b) Subthalamic nucleus
c) Fastigial nucleus
d) Putamen
Answer and Explanation:
Correct answer is c) Fastigial nucleus. The fastigial nucleus is one of the deep cerebellar nuclei involved in the coordination of balance and posture. It processes input from the cerebellar cortex and integrates vestibular and proprioceptive signals. Other choices are part of the basal ganglia, not cerebellum. (50 words)
1. The dentate nucleus is associated with:
a) Muscle tone regulation
b) Planning of voluntary movements
c) Sensory perception
d) Reflex actions
Explanation:
The dentate nucleus, largest of the cerebellar nuclei, is involved in planning, initiation, and control of voluntary movements by connecting the cerebellum with motor areas of the cerebral cortex. (Answer: b)
2. Which is not a cerebellar deep nucleus?
a) Fastigial
b) Globus pallidus
c) Interposed
d) Dentate
Explanation:
Globus pallidus is part of the basal ganglia, not cerebellar nuclei. Cerebellar deep nuclei include fastigial, interposed, and dentate nuclei, important for motor control. (Answer: b)
3. Lesion in fastigial nucleus may lead to:
a) Ataxia
b) Loss of fine touch
c) Aphasia
d) Visual field defect
Explanation:
Lesions in the fastigial nucleus affect posture and balance, causing ataxia due to disrupted vestibulocerebellar connections. (Answer: a)
4. Interposed nucleus controls:
a) Muscle tone
b) Limb movement coordination
c) Visual processing
d) Auditory perception
Explanation:
Interposed nucleus (globose and emboliform) plays a role in regulating limb movement coordination and fine motor control via cerebellar pathways. (Answer: b)
5. The primary function of cerebellar nuclei is to:
a) Generate motor commands
b) Relay and modulate signals from cerebellar cortex
c) Process sensory input
d) Regulate consciousness
Explanation:
Cerebellar nuclei relay and modulate signals from the cerebellar cortex to motor areas, integrating sensory and motor information to coordinate movement. (Answer: b)
6. Cerebellar damage presents clinically with:
a) Hemiplegia
b) Dysmetria
c) Aphasia
d) Hemianopia
Explanation:
Cerebellar damage leads to dysmetria—impaired control of movement range and force—due to disrupted coordination, especially from deep nuclei dysfunction. (Answer: b)
7. Which is true about dentate nucleus?
a) It is involved in posture regulation
b) Largest cerebellar nucleus
c) Receives input from vestibular apparatus
d) Controls spinal reflexes
Explanation:
The dentate nucleus is the largest cerebellar nucleus and is primarily involved in the planning and initiation of voluntary movements. (Answer: b)
8. Cerebellar nuclei send output via:
a) Spinothalamic tract
b) Superior cerebellar peduncle
c) Inferior cerebellar peduncle
d) Medial lemniscus
Explanation:
Cerebellar nuclei send efferent output via the superior cerebellar peduncle, mainly targeting thalamus and motor cortex to regulate movement. (Answer: b)
9. Damage to subthalamic nucleus causes:
a) Hemiballismus
b) Ataxia
c) Aphasia
d) Hypotonia
Explanation:
Lesions in the subthalamic nucleus cause hemiballismus—a unilateral, involuntary flinging movement of limbs—due to basal ganglia dysfunction, not cerebellar. (Answer: a)
10. The cerebellar vermis is involved in:
a) Cognitive processing
b) Eye movement control
c) Body posture and locomotion
d) Hearing pathways
Explanation:
Cerebellar vermis contributes to control of axial muscles, body posture, and locomotion, integrating sensory inputs and motor coordination via cerebellar nuclei. (Answer: c)
Topic: Reflexes
Subtopic: Conditioned Reflex
Keywords:
• Conditioned Reflex: A learned response to a previously neutral stimulus.
• Reinforcement: Process of strengthening a conditioned response.
• Habituation: Decreased response to a repeated benign stimulus.
• Innate Reflex: Inborn automatic response to a stimulus.
Lead Question - 2013 (September 2008)
Salivation of dog when food is given along with bell is?
a) Conditioned reflex
b) Reinforcement
c) Habituation
d) Innate reflex
Answer and Explanation:
Correct answer is a) Conditioned reflex. Pavlov’s experiment demonstrated that a neutral stimulus (bell) when paired with food becomes a conditioned stimulus, leading to salivation as a conditioned reflex. This is a classic example of learned behavior where the dog salivates to the bell alone after conditioning. (50 words)
1. Classical conditioning was first demonstrated by?
a) Skinner
b) Pavlov
c) Watson
d) Thorndike
Explanation:
Ivan Pavlov first demonstrated classical conditioning through experiments with dogs, showing that a neutral stimulus paired with food can trigger a conditioned reflex. (Answer: b)
2. In conditioned reflex, the stimulus-response association is:
a) Innate
b) Learned
c) Genetic
d) Random
Explanation:
Conditioned reflex involves a learned association between a neutral stimulus and a biologically significant stimulus, resulting in a new behavioral response. (Answer: b)
3. Reinforcement in conditioning is used to:
a) Weaken response
b) Strengthen conditioned response
c) Remove stimulus
d) Introduce habit
Explanation:
Reinforcement strengthens the conditioned reflex by increasing the probability that the conditioned response occurs following the conditioned stimulus. (Answer: b)
4. Habituation leads to:
a) Increased response
b) Unchanged response
c) Decreased response to repeated stimulus
d) Conditioned reflex formation
Explanation:
Habituation is a process where the organism gradually decreases its response to a harmless stimulus when presented repeatedly over time. (Answer: c)
5. Example of innate reflex is:
a) Pavlov's dog salivation
b) Knee jerk reflex
c) Learning to read
d) Phobia formation
Explanation:
An innate reflex, like the knee jerk reflex, is a pre-programmed automatic response not dependent on prior learning or experience. (Answer: b)
6. Which part of the brain is critical for conditioned reflex?
a) Cerebellum
b) Hypothalamus
c) Cerebral Cortex
d) Medulla
Explanation:
The cerebral cortex is primarily responsible for conditioned reflex formation by integrating sensory input and associating new stimulus-response patterns. (Answer: c)
7. Pavlov’s experiment demonstrated which type of learning?
a) Operant conditioning
b) Classical conditioning
c) Observational learning
d) Habituation
Explanation:
Pavlov’s dog experiment is a seminal example of classical conditioning, where a neutral stimulus paired with an unconditioned stimulus elicits a conditioned response. (Answer: b)
8. A neutral stimulus becomes a conditioned stimulus when:
a) It naturally triggers a response
b) It is repeatedly paired with an unconditioned stimulus
c) It is presented alone
d) It loses its effect
Explanation:
A neutral stimulus becomes conditioned by being repeatedly paired with an unconditioned stimulus until it elicits the response on its own. (Answer: b)
9. Conditioned reflex differs from innate reflex because:
a) Both are genetically programmed
b) Conditioned reflex is learned, innate is inborn
c) Innate reflex involves reinforcement
d) Conditioned reflex is involuntary
Explanation:
Conditioned reflex is acquired through learning and experience, whereas innate reflexes are inborn and do not require learning or practice. (Answer: b)
10. An example of conditioned reflex in humans is:
a) Sneezing
b) Salivating to the smell of food
c) Knee jerk
d) Cough reflex
Explanation:
Salivating at the smell or sight of food is a conditioned reflex in humans, where a neutral stimulus becomes associated with food anticipation. (Answer: b)
Topic: Motor System
Subtopic: Corticospinal Tract and Precentral Gyrus
Keywords:
• Precentral Gyrus: Brain region responsible for voluntary motor control.
• Corticospinal Tract: Major pathway transmitting motor commands from brain to spinal cord.
• Vision: Sensory perception of light and images.
• Olfaction: Sense of smell.
• Auditory: Related to hearing.
• Voluntary Movement: Conscious control of skeletal muscles.
Lead Question - 2013 (September 2008)
Precentral gyrus & corticospinal tract are essential for?
a) Vision
b) Olfaction
c) Auditory
d) Voluntary movement
Answer and Explanation:
Correct answer is d) Voluntary movement. The precentral gyrus (primary motor cortex) initiates voluntary movements, and the corticospinal tract transmits these motor signals from the cortex to the spinal motor neurons, enabling conscious control of muscle activity. This system is critical for purposeful and coordinated bodily movements. (50 words)
1. The primary function of the precentral gyrus is:
a) Sensory perception
b) Voluntary motor control
c) Balance regulation
d) Speech comprehension
Explanation:
The precentral gyrus, part of the frontal lobe, controls voluntary skeletal muscle movements by sending motor commands through the corticospinal tract. (Answer: b)
2. Corticospinal tract primarily carries:
a) Sensory signals
b) Autonomic signals
c) Voluntary motor commands
d) Reflex arcs
Explanation:
The corticospinal tract transmits voluntary motor commands from the precentral gyrus to spinal cord neurons, enabling conscious muscle control. (Answer: c)
3. Lesion of precentral gyrus causes:
a) Blindness
b) Loss of voluntary movement
c) Loss of smell
d) Hearing loss
Explanation:
Damage to the precentral gyrus results in paralysis or weakness of voluntary muscles contralateral to the lesion, as it is the primary motor cortex. (Answer: b)
4. Corticospinal tract decussation occurs at:
a) Midbrain
b) Medulla
c) Pons
d) Spinal cord
Explanation:
The corticospinal tract crosses (decussates) at the medullary pyramids, ensuring contralateral control of voluntary motor functions. (Answer: b)
5. Damage to corticospinal tract leads to:
a) Sensory loss
b) Muscle atrophy
c) Spastic paralysis
d) Loss of consciousness
Explanation:
Lesions of the corticospinal tract often produce spastic paralysis, characterized by increased muscle tone and exaggerated reflexes. (Answer: c)
6. Voluntary movement requires integration of:
a) Sensory input and motor commands
b) Reflex actions only
c) Autonomic responses
d) Visual stimuli alone
Explanation:
Voluntary movements involve integrating sensory inputs and motor commands from the precentral gyrus and other brain regions to execute precise actions. (Answer: a)
7. Corticospinal tract is also known as:
a) Pyramidal tract
b) Extrapyramidal tract
c) Spinothalamic tract
d) Vestibulospinal tract
Explanation:
The corticospinal tract is called the pyramidal tract due to its passage through the medullary pyramids and its critical role in voluntary movement control. (Answer: a)
8. Clinical sign of upper motor neuron lesion is:
a) Flaccid paralysis
b) Spasticity and hyperreflexia
c) Muscle fasciculations
d) Decreased tone
Explanation:
Upper motor neuron lesions affecting the corticospinal tract typically cause spasticity and hyperreflexia, due to loss of inhibitory control. (Answer: b)
9. Which lobe contains the precentral gyrus?
a) Parietal
b) Temporal
c) Frontal
d) Occipital
Explanation:
The precentral gyrus is located in the frontal lobe and houses the primary motor cortex responsible for voluntary motor control. (Answer: c)
10. The primary neurotransmitter of corticospinal neurons is:
a) Dopamine
b) Acetylcholine
c) Norepinephrine
d) GABA
Explanation:
Corticospinal neurons use glutamate as the primary excitatory neurotransmitter, but acetylcholine is released at the neuromuscular junction by lower motor neurons. (Answer: b)
Topic: Visual System
Subtopic: Retina and Photoreceptors
Keywords:
• Retina: Light-sensitive layer at the back of the eye.
• Cones: Photoreceptor cells responsible for color vision and visual acuity.
• Photoreceptor: Specialized cell that responds to light.
• Visual System: Structures and pathways involved in vision.
Lead Question - 2013 (September 2008)
Number of cones in Retina?
a) 3-5 millions
b) 10-20 millions
c) 25-50 millions
d) 50-100 millions
Answer and Explanation:
Correct answer is a) 3-5 millions. The human retina contains approximately 3 to 5 million cone photoreceptors concentrated in the central region called the fovea. These cones enable high-resolution color vision under bright light (photopic) conditions and are essential for tasks requiring fine visual detail. (50 words)
1. Rod cells are responsible for:
a) Color vision
b) Low-light vision
c) High-resolution vision
d) Motion detection
Explanation:
Rod cells are specialized for low-light (scotopic) vision, providing black and white images in dim conditions, with high sensitivity but low spatial resolution. (Answer: b)
2. Fovea centralis contains predominantly:
a) Rods
b) Cones
c) Bipolar cells
d) Ganglion cells
Explanation:
The fovea centralis contains the highest concentration of cone cells, essential for sharp central vision and color discrimination in bright light. (Answer: b)
3. Cone cells are most sensitive to which type of light?
a) Dim light
b) Bright light
c) Infrared light
d) Ultraviolet light
Explanation:
Cone cells function optimally in bright light conditions, enabling high acuity and color perception. (Answer: b)
4. Total number of rod cells in human retina is approximately:
a) 120 million
b) 6 million
c) 3 million
d) 1 million
Explanation:
The human retina contains around 120 million rod cells, which mediate vision in low-light conditions and are more numerous than cone cells. (Answer: a)
5. The three types of cones are sensitive to:
a) Red, Green, Blue wavelengths
b) Ultraviolet, Infrared, Visible
c) Alpha, Beta, Gamma
d) Rod, Cone, Bipolar
Explanation:
Cone cells are categorized into three types based on spectral sensitivity to red (long), green (medium), and blue (short) wavelengths, enabling color vision. (Answer: a)
6. Clinical condition related to cone dysfunction is called:
a) Night blindness
b) Color blindness
c) Glaucoma
d) Cataract
Explanation:
Color blindness is caused by defective or absent cone cells, impairing color discrimination, typically inherited and most commonly affecting red-green perception. (Answer: b)
7. Which layer of retina contains photoreceptors?
a) Ganglion cell layer
b) Inner nuclear layer
c) Outer nuclear layer
d) Plexiform layer
Explanation:
The photoreceptors, including rods and cones, are located in the outer nuclear layer of the retina, where they transduce light into neural signals. (Answer: c)
8. Cone density is maximum at:
a) Optic disc
b) Peripheral retina
c) Fovea centralis
d) Macula lutea
Explanation:
Cone density peaks in the fovea centralis, the central region of the retina, responsible for sharp and detailed central vision. (Answer: c)
9. Cone cells mediate which type of vision?
a) Scotopic
b) Photopic
c) Mesopic
d) None
Explanation:
Cone cells mediate photopic vision, functioning under bright light conditions, essential for color perception and high visual acuity. (Answer: b)
10. Cone dysfunction may lead to which of the following disorders?
a) Glaucoma
b) Achromatopsia
c) Retinitis pigmentosa
d) Optic neuritis
Explanation:
Achromatopsia is a congenital condition caused by cone dysfunction, resulting in color blindness, poor visual acuity, and photophobia. (Answer: b)
Topic: Hypothalamic Regulation
Subtopic: Orexigenic Neurons
Keyword Definitions:
Orexigenic Neurons: Neurons that stimulate appetite and increase food intake.
Dorsal Raphae: Nucleus in brainstem involved in serotonin production.
Locus Coeruleus: Brainstem nucleus involved in noradrenaline production.
Lateral Hypothalamic Area: Hypothalamic region promoting feeding behavior.
Hippocampus: Brain structure involved in memory formation.
Lead Question - 2013
Cell bodies of orexigenic neurons are present in?
a) Dorsal raphae
b) Locus coeruleus
c) Lateral hypothalamic area
d) Hippocampus
Answer & Explanation:
Answer: c) Lateral hypothalamic area.
Orexigenic neurons, which promote appetite, are primarily located in the lateral hypothalamic area. These neurons stimulate food intake by releasing neuropeptides that act on various brain regions. Dysfunction in this area may lead to eating disorders such as anorexia or obesity. The correct answer is lateral hypothalamic area.
1. Guessed Question
Which neurotransmitter is primarily involved in stimulating orexigenic neurons?
a) Dopamine
b) Norepinephrine
c) Neuropeptide Y
d) Serotonin
Answer & Explanation:
Answer: c) Neuropeptide Y.
Neuropeptide Y (NPY) is a powerful orexigenic neurotransmitter that stimulates food intake and reduces energy expenditure. It is synthesized in the hypothalamus and acts on various brain regions to promote hunger. Increased NPY activity is associated with increased appetite and obesity, while decreased levels relate to anorexia.
2. Guessed Question
Destruction of the lateral hypothalamic area causes:
a) Hyperphagia
b) Aphagia
c) Polydipsia
d) Polyuria
Answer & Explanation:
Answer: b) Aphagia.
Destruction of the lateral hypothalamic area leads to aphagia, which is the inability or refusal to eat. This area is crucial for hunger signaling. Damage to this region results in severe anorexia and weight loss. Therefore, the correct answer is aphagia, indicating its role in promoting food intake.
3. Guessed Question
Which of the following is NOT a function of the hypothalamus?
a) Regulation of hunger
b) Thermoregulation
c) Visual processing
d) Water balance regulation
Answer & Explanation:
Answer: c) Visual processing.
The hypothalamus regulates hunger, thirst, body temperature, and circadian rhythms but does not participate directly in visual processing. Visual information is processed by the occipital lobe and visual cortex. Therefore, visual processing is not a function of the hypothalamus, making it the correct choice for this question.
4. Guessed Question
Which hormone released by the hypothalamus stimulates appetite?
a) Leptin
b) Ghrelin
c) Insulin
d) Cortisol
Answer & Explanation:
Answer: b) Ghrelin.
Ghrelin, secreted by the stomach, acts on the hypothalamus to stimulate appetite and promote food intake. It increases before meals and decreases after food consumption. High ghrelin levels are associated with increased hunger and potential weight gain, while low levels relate to appetite suppression.
5. Guessed Question
Orexigenic neurons are activated during:
a) Postprandial state
b) Fasting state
c) Sleep
d) Physical exercise
Answer & Explanation:
Answer: b) Fasting state.
During fasting, orexigenic neurons in the lateral hypothalamic area become activated, increasing the secretion of hunger-promoting neuropeptides like NPY and AgRP. This stimulates appetite and encourages food-seeking behavior, aiming to restore energy balance. Therefore, the correct answer is fasting state.
6. Guessed Question
Which peptide inhibits orexigenic neurons?
a) Agouti-related peptide (AgRP)
b) Leptin
c) Neuropeptide Y (NPY)
d) Melanin-concentrating hormone (MCH)
Answer & Explanation:
Answer: b) Leptin.
Leptin, secreted by adipose tissue, inhibits orexigenic neurons and promotes satiety. High leptin levels signal sufficient energy stores, decreasing appetite. In obesity, leptin resistance may develop, impairing this regulation. Therefore, leptin is the key hormone that suppresses orexigenic neuronal activity.
7. Guessed Question
Orexigenic neurons primarily release which of the following?
a) Dopamine
b) Agouti-related peptide (AgRP)
c) Acetylcholine
d) GABA
Answer & Explanation:
Answer: b) Agouti-related peptide (AgRP).
Orexigenic neurons release Agouti-related peptide (AgRP) and neuropeptide Y (NPY), which stimulate appetite by antagonizing melanocortin receptors in the hypothalamus. These peptides promote feeding and reduce energy expenditure. Hence, AgRP is correctly identified as a primary mediator of orexigenic neuron action.
8. Guessed Question
Which clinical condition is associated with damage to the lateral hypothalamic area?
a) Obesity
b) Anorexia
c) Hypertension
d) Diabetes insipidus
Answer & Explanation:
Answer: b) Anorexia.
Damage to the lateral hypothalamic area causes severe anorexia and aphagia, leading to weight loss. This area is critical for hunger signaling. Absence of its function impairs the body's ability to initiate feeding behavior, resulting in decreased food intake and energy imbalance.
9. Guessed Question
Which of the following statements is true about orexigenic neurons?
a) Inhibit food intake
b) Located in hippocampus
c) Promote feeding behavior
d) Located in dorsal raphae
Answer & Explanation:
Answer: c) Promote feeding behavior.
Orexigenic neurons stimulate appetite and promote food intake by releasing neuropeptides such as NPY and AgRP. Located in the lateral hypothalamic area, they are activated during energy deficit states. Their primary role is to encourage feeding, contrasting with anorexigenic neurons that suppress appetite.
10. Guessed Question
Leptin resistance is commonly observed in:
a) Anorexia nervosa
b) Obesity
c) Hypothyroidism
d) Addison's disease
Answer & Explanation:
Answer: b) Obesity.
Leptin resistance occurs when high leptin levels fail to suppress appetite, commonly observed in obesity. This condition prevents adequate feedback to the hypothalamus, causing continued food intake despite sufficient energy stores. It is a key factor in the pathophysiology of obesity, leading to further weight gain.