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Neural Control and Coordination - Nervous system in humans (Central, Peripheral and Visceral)

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The human nervous system is divided into two parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

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The CNS includes the brain and the spinal cord and is the site of information processing and control.

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The PNS comprises all the nerves of the body associated with the CNS. It is divided into the Somatic neural system and the Autonomic neural system.

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The Somatic neural system relays impulses from the CNS to skeletal muscles, whereas the Autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles.

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The Autonomic neural system is further classified into the Sympathetic neural system and the Parasympathetic neural system.

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The Visceral nervous system is the part of the PNS that comprises the whole complex of nerves, fibers, ganglia, and plexuses by which impulses travel from the CNS to the viscera and from the viscera to the CNS.

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Nerve impulse conduction is an electrochemical process. At resting state, the axonal membrane is more permeable to K+K^+ and nearly impermeable to Na+Na^+.

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The resting potential is maintained by the active transport of ions by the Na+/K+Na^+/K^+ pump, which transports 3Na+3 Na^+ outwards for 2K+2 K^+ into the cell.

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Depolarization occurs when a stimulus triggers the opening of Na+Na^+ channels, causing an influx of Na+Na^+ and changing the polarity to positive inside (+30+30 to +40 mV+40\text{ mV}).

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The Brain is divided into the Forebrain (Cerebrum, Thalamus, Hypothalamus), Midbrain, and Hindbrain (Pons, Cerebellum, Medulla oblongata).

📐Formulae

3Naout+:2Kin+ (Sodium-Potassium Pump ratio)3 Na^+_{out} : 2 K^+_{in} \text{ (Sodium-Potassium Pump ratio)}

Resting Membrane Potential≈−70 mV\text{Resting Membrane Potential} \approx -70\text{ mV}

Threshold Potential≈−55 mV\text{Threshold Potential} \approx -55\text{ mV}

Action Potential (Peak)≈+30 to +40 mV\text{Action Potential (Peak)} \approx +30\text{ to } +40\text{ mV}

💡Examples

Problem 1:

During the resting state of a neural membrane, if the Na+/K+Na^+/K^+ pump is inhibited, what will happen to the membrane potential?

Solution:

The membrane potential will gradually move towards 0 mV0\text{ mV}, resulting in depolarization.

Explanation:

The Na+/K+Na^+/K^+ pump maintains the concentration gradient by pumping 3Na+3 Na^+ out and 2K+2 K^+ in against their gradients using ATP. If inhibited, the ionic gradients will dissipate due to leakage, and the resting potential of −70 mV-70\text{ mV} cannot be maintained.

Problem 2:

A person suffers a head injury that results in the loss of ability to regulate body temperature. Which part of the brain is likely damaged?

Solution:

The Hypothalamus.

Explanation:

The Hypothalamus contains centers which control body temperature, urge for eating, and drinking. It is the master control center for the autonomic nervous system and homeostasis.

Problem 3:

Calculate the net charge movement across the axonal membrane for every 5 cycles of the Na+/K+Na^+/K^+ pump.

Solution:

Net movement of 55 positive charges (5e+5e^+) out of the cell.

Explanation:

In one cycle, 3Na+3 Na^+ (positive) move out and 2K+2 K^+ (positive) move in. Net charge per cycle is 3−2=13 - 2 = 1 positive charge moving out. For 5 cycles: 5×1=55 \times 1 = 5 positive charges out.

Nervous system in humans (Central, Peripheral and Visceral) Revision - Class 11 Biology CBSE