Class 11 Biology Chapter 18 Neural Control And Coordination

Key Concept: Limbic System, Function of Synapses and Neurotransmitters

c) Amygdala activation enhances synaptic plasticity, facilitating memory retrieval.

[Solution Description] The limbic system, particularly the amygdala and hippocampus, are crucial for processing emotions and memories. Upon recalling an emotional event, the amygdala activates to evaluate the emotional significance, while the hippocampus retrieves associated memory details. This process involves complex synaptic activity where neurotransmitters like glutamate facilitate long-term potentiation, strengthening synaptic connections to enhance memory retention.

Key Concept: Ion Movement

b) Sodium ($Na^+$)

[Solution Description] During depolarization, sodium ions ($Na^+$) move into the cell, which causes the inside of the neuron to become more positive, leading to the reversal of membrane polarity.

Key Concept: PNS Nerve Fibres

d) Afferent fibres

[Solution Description] Afferent fibres are responsible for transmitting sensory information from different parts of the body to the central nervous system.

Key Concept: Basic Functions

c) Endocrine system

[Solution Description] The endocrine system is responsible for chemical integration in the body by secreting hormones into the bloodstream, which then travel to target organs and exert their effects.

Key Concept: Basic Structure

c) Assertion is true, but Reason is false.

[Solution Description]

The assertion describes the components of the central nervous system correctly, as it comprises the brain and the spinal cord. The reason, however, incorrectly states that the peripheral nervous system is solely responsible for voluntary muscle control. While it does include somatic parts which handle voluntary actions, the PNS also contains autonomic divisions that control involuntary actions. Thus, the Reason is false.

Key Concept: Synapse Types

d) Electrical synapse

[Solution Description] Electrical synapses involve a direct flow of ions between neurons through gap junctions, allowing rapid transmission of impulses.

Key Concept: Myelination

a) They have nodes of Ranvier

[Solution Description] Myelinated nerve fibers are characterized by the presence of a myelin sheath formed by Schwann cells around the axon, which increases the speed of nerve impulse conduction.

Key Concept: Brain Functions

c) Thermoregulation

[Solution Description] The brain is responsible for processing sensory information, controlling voluntary and involuntary movements, and regulating various bodily functions like thermoregulation.

Key Concept: Neural Divisions

c) Sympathetic and parasympathetic

[Solution Description] The autonomic neural system is divided into the sympathetic and parasympathetic systems. These subdivisions manage involuntary bodily functions in opposite manners.

Key Concept: Autonomic System

c) Sympathetic

[Solution Description] The sympathetic division of the autonomic neural system prepares the body for intense physical activity by increasing heart rate, dilating airways, and releasing stored energy, commonly known as the “fight or flight” response.

Key Concept: Simple Definition

b) Balance and coordination

[Solution Description] The cerebellum’s primary function is to maintain balance and coordination by accommodating more neurons on its convoluted surface.

Key Concept: Basic Structure

d) Dendrites

[Solution Description] The part of the neuron that receives signals from other neurons is called dendrites. Dendrites have structures that function as receptors, allowing them to detect and receive electrochemical impulses from other cells.

Key Concept: Neural System Components

a) Central Nervous System and Peripheral Nervous System

[Solution Description] The human neural system is divided into the central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system (PNS), which connects the CNS to various parts of the body.

Key Concept: Basic Definitions

b) Transmit signals from CNS to muscles and organs

[Solution Description]

Efferent nerve fibres are responsible for transmitting impulses from the central nervous system (CNS) to various parts of the body, such as muscles and glands, thus enabling response actions.

Key Concept: Neuron Types

a) Multipolar

[Solution Description] A multipolar neuron is characterized by having one axon and several dendrites. This structure allows it to integrate information from many other neurons.

Key Concept: Action Potential

b) Stimulus causes membrane permeability to $\text{Na}^+$.

[Solution Description] An action potential is initiated when a stimulus makes the membrane permeable to $\text{Na}^+$ ions, causing them to rush into the neuron. This influx results in depolarization of the membrane.

Key Concept: Synapses: Characteristics of Electrical Synapse

c) There is direct flow of electrical current between neurons.

[Solution Description] Electrical synapses are characterized by direct flow of electrical current between neurons through gap junctions, which results in faster transmission compared to chemical synapses.

Key Concept: Basic Definition

c) Resting potential

[Solution Description] The electrical potential difference across the resting plasma membrane is termed as “Resting potential”. It represents the voltage difference when a neuron is not conducting any impulses.

Key Concept: Basic Definition

d) Resting Potential

[Solution Description]

Resting potential is referred to as the electrical potential difference across the resting plasma membrane of a neuron.

Key Concept: Function Identification

a) Respiration rate

[Solution Description] During physical exercise, the body’s demand for energy rises, leading to an increase in oxygen supply, respiration rate, heart beat, and blood flow.

Key Concept: Structure Identification

c) Cerebral aqueduct

[Solution Description] The cerebral aqueduct is the canal that passes through the midbrain.

Key Concept: Complex Function Analysis, Systemic Coordination

c) Emotional inputs from the limbic system are integrated with cortical reasoning.

[Solution Description] The limbic system is integral to processing emotions and memory. Under stress, it interacts extensively with the prefrontal cortex, responsible for decision-making and reasoning. This interaction allows individuals to evaluate emotional contexts and make informed decisions rather than impulsive reactions. However, heightened emotional arousal may overpower rational cortical functions, leading to decisions that prioritize immediate emotional relief over long-term benefits.

Key Concept: Basic Structure

b) Corpus callosum

[Solution Description] The corpus callosum is the thick band of nerve fibers that connects the two cerebral hemispheres, allowing for communication between them.

Key Concept: Basic Coordination

d) Neural system

[Solution Description] The neural system is known for providing rapid point-to-point communication, allowing organs and tissues to coordinate their activities swiftly to maintain homeostasis.

Key Concept: Nerve Fibres

b) Afferent fibres

[Solution Description] Afferent fibres in the peripheral neural system are responsible for transmitting sensory impulses from various tissues and organs back to the central neural system (CNS).

Key Concept: Function Identification

d) Transmitting impulses to involuntary organs

[Solution Description] The visceral nervous system’s primary function is transmitting impulses to involuntary organs and smooth muscles, such as the heart and digestive tract.

Key Concept: Synapse Types

b) Direct flow of electrical current

[Solution Description] Electrical synapses are characterized by direct flow of electrical current from one neuron to another, allowing for faster transmission. Unlike chemical synapses, they do not rely on neurotransmitters or a synaptic cleft.

Key Concept: Depolarization

d) Sodium (Na$^+$)

[Solution Description] During the depolarization phase of an action potential, voltage-gated sodium ($\text{Na}^+$) channels open, allowing $\text{Na}^+$ ions to enter the neuron rapidly. This influx of sodium ions reverses the membrane polarity.