Grade 11 Biology: Neural Quiz | Concept of Maths Ranchi

Question 1

1. In a resting neuron, the $Na^+/K^+$ pump actively transports ions across the membrane to maintain the electrochemical gradient. If the pump moves $300$ $Na^+$ ions out of the cell, how many $K^+$ ions are simultaneously moved into the cell?

A) 150 ions

B) 200 ions

C) 450 ions

D) 600 ions

Answer

Correct Answer: B

Explanation: The $Na^+/K^+$ ATPase pump operates in a fixed ratio of $3 Na^+$ out for every $2 K^+$ in. Given: $Na^+_{out} = 300$. Let $K^+_{in} = x$. Setting up the ratio: $$\frac{3}{2} = \frac{300}{x}$$ $$3x = 600 \implies x = 200\text{ ions.}$$

Question 2

2. A graph of an Action Potential shows the membrane potential (y-axis) in $mV$ vs Time (x-axis) in $ms$. If the resting potential is $-70\text{ mV}$ and the threshold potential is $-55\text{ mV}$, what is the minimum voltage change ($\Delta V$) required to trigger an "all-or-none" response?

A) $-15\text{ mV}$

B) $+125\text{ mV}$

C) $+15\text{ mV}$

D) $+70\text{ mV}$

Answer

Correct Answer: C

Explanation: The threshold stimulus is the minimum depolarization required. $$\Delta V = V_{\text{threshold}} - V_{\text{resting}}$$ $$\Delta V = -55\text{ mV} - (-70\text{ mV}) = -55 + 70 = +15\text{ mV}.$$

Question 3

3. Consider a myelinated axon of length $L = 1.8$ meters. If the nerve impulse travels via saltatory conduction at a velocity of $v = 120\text{ m/s}$, calculate the time $t$ taken for the signal to reach the axon terminal.

A) 15 ms

B) 1.5 ms

C) 0.15 s

Question 4

4. In a chemical synapse, a delay occurs due to neurotransmitter release and diffusion. If a reflex arc involves 3 synapses with a delay of $0.5\text{ ms}$ each, and the total conduction time through the neurons is $12\text{ ms}$, what is the total reflex latency?

A) 12.5 ms

B) 15 ms

C) 36 ms

D) 13.5 ms

Answer

Correct Answer: D

Explanation: Total Latency = Conduction Time + (Number of Synapses $\times$ Synaptic Delay). $$T = 12\text{ ms} + (3 \times 0.5\text{ ms}) = 12 + 1.5 = 13.5\text{ ms}.$$

Question 5

5. Visual acuity is highest at the Fovea Centralis. If the density of cones in the fovea is $150,000\text{ per mm}^2$ and the density of rods in the peripheral retina is $160,000\text{ per mm}^2$, but the fovea contains ZERO rods, what is the ratio of Rods to Cones in a $1\text{ mm}^2$ sample taken exactly from the foveal center?

A) $16:15$

B) $1:1$

C) $0:1$

D) $15:16$

Answer

Correct Answer: C

Explanation: In the fovea centralis, only cones are present. Rods are entirely absent. $$\text{Ratio} = \frac{\text{Rods}}{\text{Cones}} = \frac{0}{150,000} = 0.$$ This is cleanly expressed as a $0:1$ ratio.

Question 6

6. The human ear can distinguish frequencies from $20\text{ Hz}$ to $20,000\text{ Hz}$. If a specific sound wave has a wavelength of $\lambda = 1.7\text{ cm}$ in air (where speed of sound $v = 340\text{ m/s}$), determine if this frequency falls within the human audible range.

A) No, it is $2,000\text{ Hz}$ (Infra-sonic)

B) Yes, it is $20,000\text{ Hz}$ (Upper limit)

C) Yes, it is $200\text{ Hz}$

D) No, it is $200,000\text{ Hz}$ (Ultra-sonic)

Answer

Correct Answer: B

Explanation: Frequency $f = \frac{v}{\lambda}$. Convert $\lambda$ to meters: $1.7\text{ cm} = 0.017\text{ m}$. $$f = \frac{340}{0.017} = \frac{340000}{17} = 20,000\text{ Hz}.$$ This value marks the exact upper limit of standard human hearing capabilities.

Question 7

7. A patient has a defect in the refractive power of the eye. If the focal length of the eye lens is $2\text{ cm}$, what is its power $P$ in Dioptres ($D$)? (Use $P = 1/f$ where $f$ is in meters).

A) $50\text{ D}$

B) $2\text{ D}$

C) $0.5\text{ D}$

D) $20\text{ D}$

Answer

Correct Answer: A

Explanation: First, convert the focal length to meters: $$f = 2\text{ cm} = 0.02\text{ m}.$$ Now solve for power: $$P = \frac{1}{f} = \frac{1}{0.02} = \frac{100}{2} = 50\text{ Dioptres}.$$

Question 8

8. During the Repolarization phase of an action potential, the permeability of the membrane to $K^+$ increases significantly. If the efflux of $K^+$ ions results in the potential dropping from $+30\text{ mV}$ to $-70\text{ mV}$ in $1\text{ ms}$, what is the rate of voltage change?

A) $40\text{ mV/ms}$

B) $-40\text{ mV/ms}$

C) $100\text{ mV/ms}$

D) $-100\text{ mV/ms}$

Answer

Correct Answer: D

Explanation: Rate of change = $\frac{V_{\text{final}} - V_{\text{initial}}}{\Delta t}$. $$\text{Rate} = \frac{-70\text{ mV} - (+30\text{ mV})}{1\text{ ms}} = \frac{-100\text{ mV}}{1\text{ ms}} = -100\text{ mV/ms}.$$

Question 9

9. The human brain contains approximately $100$ billion neurons. If each neuron has an average of $1,000$ synapses, estimate the total number of synaptic connections in the brain using scientific notation.

A) $10^{11}$

B) $10^{14}$

C) $10^{12}$

D) $10^{15}$

Answer

Correct Answer: B

Explanation: Total synapses = Neurons $\times$ Synapses per neuron. $$100\text{ billion} = 100 \times 10^9 = 10^{11}\text{ neurons.}$$ $$\text{Total} = 10^{11} \times 1,000 = 10^{11} \times 10^3 = 10^{14}\text{ connections.}$$

Question 10

10. Imagine a cross-section of the spinal cord. If there are $31$ pairs of spinal nerves, how many total individual roots (dorsal and ventral) exit the spinal cord in total?

A) 31

B) 62

C) 124

D) 93

Answer

Correct Answer: C

Explanation: There are $31$ pairs of nerves ($62$ individual nerves total). Each singular spinal nerve splits into or is formed by the union of exactly one dorsal root and one ventral root. $$\text{Total roots} = 31\text{ pairs} \times 2\text{ nerves/pair} \times 2\text{ roots/nerve} = 124\text{ roots.}$$

Accepted Answer

Correct Answer: A

Explanation: Velocity $v = \frac{L}{t} \implies t = \frac{L}{v}$. $$t = \frac{1.8\text{ m}}{120\text{ m/s}} = 0.015\text{ seconds.}$$ To convert to milliseconds: $0.015 \times 1000 = 15\text{ ms}$.

Grade 11 : Biology - Neural (Set 4) | Concept of Maths

Grade 11 : Biology - Neural (Set 4) | Concept of Maths

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4. In a chemical synapse, a delay occurs due to neurotransmitter release and diffusion. If a reflex arc involves 3 synapses with a delay of $0.5\text{ ms}$ each, and the total conduction time through the neurons is $12\text{ ms}$, what is the total reflex latency?

6. The human ear can distinguish frequencies from $20\text{ Hz}$ to $20,000\text{ Hz}$. If a specific sound wave has a wavelength of $\lambda = 1.7\text{ cm}$ in air (where speed of sound $v = 340\text{ m/s}$), determine if this frequency falls within the human audible range.

7. A patient has a defect in the refractive power of the eye. If the focal length of the eye lens is $2\text{ cm}$, what is its power $P$ in Dioptres ($D$)? (Use $P = 1/f$ where $f$ is in meters).

8. During the Repolarization phase of an action potential, the permeability of the membrane to $K^+$ increases significantly. If the efflux of $K^+$ ions results in the potential dropping from $+30\text{ mV}$ to $-70\text{ mV}$ in $1\text{ ms}$, what is the rate of voltage change?

9. The human brain contains approximately $100$ billion neurons. If each neuron has an average of $1,000$ synapses, estimate the total number of synaptic connections in the brain using scientific notation.

10. Imagine a cross-section of the spinal cord. If there are $31$ pairs of spinal nerves, how many total individual roots (dorsal and ventral) exit the spinal cord in total?

Grade 11 Biology: Neural Quiz | Concept of Maths Ranchi

1. In a resting neuron, the $Na^+/K^+$ pump actively transports ions across the membrane to maintain the electrochemical gradient. If the pump moves $300$ $Na^+$ ions out of the cell, how many $K^+$ ions are simultaneously moved into the cell?

2. A graph of an Action Potential shows the membrane potential (y-axis) in $mV$ vs Time (x-axis) in $ms$. If the resting potential is $-70\text{ mV}$ and the threshold potential is $-55\text{ mV}$, what is the minimum voltage change ($\Delta V$) required to trigger an "all-or-none" response?

3. Consider a myelinated axon of length $L = 1.8$ meters. If the nerve impulse travels via saltatory conduction at a velocity of $v = 120\text{ m/s}$, calculate the time $t$ taken for the signal to reach the axon terminal.

Grade 11 : Biology - Neural (Set 4) | Concept of Maths

Grade 11 : Biology - Neural (Set 4) | Concept of Maths

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4. In a chemical synapse, a delay occurs due to neurotransmitter release and diffusion. If a reflex arc involves 3 synapses with a delay of $0.5\text{ ms}$ each, and the total conduction time through the neurons is $12\text{ ms}$, what is the total reflex latency?

6. The human ear can distinguish frequencies from $20\text{ Hz}$ to $20,000\text{ Hz}$. If a specific sound wave has a wavelength of $\lambda = 1.7\text{ cm}$ in air (where speed of sound $v = 340\text{ m/s}$), determine if this frequency falls within the human audible range.

7. A patient has a defect in the refractive power of the eye. If the focal length of the eye lens is $2\text{ cm}$, what is its power $P$ in Dioptres ($D$)? (Use $P = 1/f$ where $f$ is in meters).

8. During the Repolarization phase of an action potential, the permeability of the membrane to $K^+$ increases significantly. If the efflux of $K^+$ ions results in the potential dropping from $+30\text{ mV}$ to $-70\text{ mV}$ in $1\text{ ms}$, what is the rate of voltage change?

9. The human brain contains approximately $100$ billion neurons. If each neuron has an average of $1,000$ synapses, estimate the total number of synaptic connections in the brain using scientific notation.

10. Imagine a cross-section of the spinal cord. If there are $31$ pairs of spinal nerves, how many total individual roots (dorsal and ventral) exit the spinal cord in total?