Neural Control and Coordination - Class 11 Biology - Chapter 16 - Notes, NCERT Solutions & Extra Questions
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Extra Questions - Neural Control and Coordination | NCERT | Biology | Class 11
The given diagram represents a reflex action showing the knee jerk reflex.
A | B | C | D | E | |
---|---|---|---|---|---|
(a) | Ventral root ganglion | White Matter | gray Matter | Efferent Matter | Afferent Matter |
(b) | Dorsal root ganglion | gray Matter | White Matter | Efferent Matter | Afferent Matter |
(c) | Dorsal root ganglion | White Matter | gray Matter | Efferent Matter | Afferent Matter |
(d) | Dorsal root ganglion | White Matter | gray Matter | Afferent Matter | Efferent Matter |
In which of the following options, the correct words for all the 5 blanks ($A$ to $E$) are illustrated.
The given diagram illustrates the knee-jerk reflex, a fundamental example of a reflex arc, and labels various components of the nervous system involved in reflex actions. To understand the solution:
Label A represents the Dorsal root ganglion, which houses the cell bodies of sensory neurons.
Label B represents the White matter in the spinal cord, known for containing myelinated axons which carry nerve impulses.
Label C shows the Gray matter of the spinal cord, which primarily contains neuron cell bodies and is the site of information processing.
Label D points to the Efferent pathway or motor pathway, responsible for conveying commands from the central nervous system to the muscles.
Label E is the Afferent pathway, which includes sensory neurons carrying signals from receptors to the central nervous system.
The options provided in the multiple-choice question need to match the diagram’s annotations correctly:
(a) Mistakenly mentions ventral root ganglion for A.
(b) Incorrectly swaps the locations of white and gray matter and mislabels the pathways.
(c) Correctly matches all descriptions: Dorsal root ganglion for A, White matter for B, Gray matter for C, Efferent pathway for D, and Afferent pathway for E.
(d) Errors in identifying the afferent and efferent pathways.
Thus, the correct answer is Option C. This matches the labels in the diagram accurately according to the established understanding of spinal cord anatomy and the functioning of reflex arcs.
An area in the brain which is associated with strong emotions is:
A) Cerebral cortex
B) Cerebellum
C) Limbic system
D) Medulla
The correct option is C) Limbic system.
The Limbic system is integral in controlling emotions such as excitement, pleasure, rage, and fear and is involved in motivation processes.
The Cerebral cortex is essential for voluntary activities, language, speech, thinking, and memory functions.
The Cerebellum is responsible for coordinating voluntary movements, which include posture, balance, and speech, to ensure smooth and balanced muscular activity.
The Medulla oblongata regulates vital autonomic functions, including respiration, cardiac function, and reflex actions like vomiting, coughing, sneezing, and swallowing.
Leakage channels are regulated by
A) Voltage
B) Chemicals
C) Nothing
D) Heat
The correct option is C) Nothing
Leakage channels, unlike gated channels, are not regulated and remain open continuously. They do not respond to specific stimuli that regulate other types of channels, which include voltage, chemicals, or thermal factors. Leakage channels simply allow ions to pass through them at all times without the influence of external controls.
Corpora Quadrigemina are part of:
A. Rhombencephalon
B. Mesencephalon
C. Diencephalon
D. Metencephalon
Solution:
The correct option is B. Mesencephalon
Explanation:
The Corpora Quadrigemina are a component of the midbrain, which is also known as the mesencephalon.
Which of the following statements define a myogenic heart?
A) A heart with 4 chambers is called a myogenic heart.
B) A heart in which the blood circulates twice is called a myogenic heart.
C) A heart that does not require neural input to beat is called a myogenic heart.
D) A heart that requires neural input to beat is called a myogenic heart.
The correct answer is C) A heart that does not require neural input to beat is called a myogenic heart.
Explanation:
The term myogenic refers to the heart's ability to initiate its own heartbeat independent of external neural input. This inherent capability arises from specialized muscle tissue capable of generating electrochemical impulses. In humans, the sinoatrial (SA) node located in the right atrium functions as this initiation point.
Additional Context:
- A neurogenic heart, which requires neural impulses to begin beating, is commonly found in arthropods.
- The human heart, and those of all mammals and birds, include four chambers: two atria and two ventricles.
- The double circulation system, where the blood passes through the heart twice during each circuit (systemic and pulmonary circulation), is an arrangement seen in mammals and birds.
Which among the following carries both sensory and motor information?
A. Cranial nerves
B. Spinal nerves
C. Mixed nerves
D. Depressor nerve
The correct answer is C. Mixed nerves.
Mixed nerves are unique in their composition and function. Nerves can be classified as either sensory, motor, or mixed. Sensory nerves primarily carry information from sensory receptors to the brain and spinal cord, detailing experiences like touch, temperature, and pain. Conversely, motor nerves are responsible for transmitting impulses from the brain and spinal cord to muscles, facilitating movement.
Mixed nerves, however, contain both sensory and motor fibers, which allow them to perform dual functions. They are capable of transmitting signals in both directions, from sensory organs to the brain and from the brain to muscles, making them integral for comprehensive neural communication and coordination.
Mention where in the human body the following are located and state their main functions: (a) Corpus callosum (b) Central canal
Solution
(a) Corpus Callosum
- Location: Located in the forebrain.
- Main Function: Its primary function is to connect the two cerebral hemispheres and facilitate the transfer of information between them.
(b) Central Canal
- Location: Found at the center of the spinal cord.
- Main Function: Continues from the cavities of the brain and is filled with cerebrospinal fluid. It serves as a shock-absorbing cushion and aids in the exchange of materials with neurons.
Sympathetic and parasympathetic nervous systems are parts of the autonomic nervous system.
A) True
B) False
The correct answer is A) True.
The sympathetic and parasympathetic nervous systems are indeed part of the autonomic nervous system (ANS), which regulates involuntary physiological processes including heart rate, respiratory rate, pupil dilation, and digestion among others. The sympathetic nervous system gears the body up for 'fight or flight' responses, increasing heart rate and energy output. In contrast, the parasympathetic nervous system helps calm the body down and conserves energy, bringing the body back to a more restful state after a perceived threat has passed.
Sympathetic and parasympathetic nervous systems are parts of which system?
A) Central Nervous System
B) Autonomous Nervous System
C) Peripheral Nervous System
D) Special Nervous System
The correct answer is B) Autonomous Nervous System.
The sympathetic and parasympathetic nervous systems are integral components of the Autonomic Nervous System (ANS). These systems regulate involuntary actions such as heart rate, breathing rate, and body temperature. Specifically, the sympathetic nervous system is crucial for preparing the body for "fight or flight" responses, while the parasympathetic system helps the body to relax and return to normalcy after stress.
In how many parts is the human brain divided?
A. 4
B. 5
C. 3
D. 2
The human brain is divided into three main parts. These parts include:
The Cerebrum - This is the largest part of the brain, responsible for various complex functions such as sensory processing and voluntary muscle activity.
The Cerebellum - It helps manage motor functions and maintain posture and balance.
The Brainstem - This serves as the relay center connecting the cerebrum and cerebellum to the spinal cord and manages automatic functions necessary for survival, like breathing and heart rate.
The correct answer to the question is: C. 3
Central Nervous system consists of brain and _____
Spinal cord
Spinal nerves
Cranial nerves
All the nerves
The Central Nervous System (CNS) consists primarily of the brain and the spinal cord. Contrary to common misconception, it does not include nerves such as spinal nerves or cranial nerves. Those are part of the Peripheral Nervous System (PNS), which operates externally to the CNS. The PNS is crucial as it carries out the function of transmitting signals from the CNS to various organs throughout the body.
To sum up, the CNS is fundamentally composed of the brain and spinal cord, which are central to processing and sending out signals that result in various bodily actions and reactions.
Is it right to say that the giant squid has thick nerve fibres for the quicker conduction of nerve impulses? If not, why?
Neurons with myelin (myelinated neurons) conduct impulses significantly faster than those without myelin. Schwann cells (or oligodendrocytes) are situated at regular intervals along the axons and, for some neurons, dendrites. Between areas of myelin, there are non-myelinated areas known as the nodes of Ranvier.
Since myelin acts as an insulator, the membrane coated with myelin does not conduct an impulse. In a myelinated neuron, action potentials occur only at the nodes, causing impulses to 'jump' over the myelinated regions. This process is called saltatory conduction, derived from the Latin word "saltare" which means 'jumping'. As a result, impulses travel much faster along a myelinated neuron compared to a non-myelinated neuron.
The velocity of nerve impulses is not only dependent on myelination but also on the thickness of the nerve fibres. Impulses travel faster in thicker nerve fibres than in thinner ones. In invertebrates like squids, non-myelinated, but very thick nerve fibres enable rapid conduction of impulses to distant parts, such as the long arms of squids.
Vertebrates have evolved a different mechanism for rapid conduction of nerve impulses. They possess thin myelinated nerve fibres which convey nerve impulses much faster than non-myelinated nerve fibres. This adaptation eliminates the necessity for inconveniently thick fibres in animals with long limbs.
The number of pairs of nerves which arise from the spinal cord is _____.
(a) 21
(b) 31
(c) 41
(d) 51
Correct Answer: (b) 31
The spinal cord gives rise to a total of 31 pairs of nerves. These nerves act as important conduits for transmitting signals between the body and the brain, playing a crucial role in both motor and sensory functions.
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Briefly describe the structure of the Brain
The brain is the central information processing organ of our body and is divided into three major parts:
Forebrain:
Cerebrum: The largest part, divided into left and right hemispheres connected by the corpus callosum. It contains the cerebral cortex (grey matter) which includes motor, sensory, and association areas.
Thalamus: Acts as the major coordinating center for sensory and motor signaling.
Hypothalamus: Controls body temperature, hunger, thirst, and releases hypothalamic hormones. It’s also part of the limbic system which regulates emotional reactions and motivations.
Midbrain:
Located between the thalamus/hypothalamus and the pons.
Contains the cerebral aqueduct and corpora quadrigemina.
Hindbrain:
Pons: Contains fibre tracts linking different regions of the brain.
Cerebellum: Highly convoluted surface that integrates sensory information and coordinates voluntary movements.
Medulla Oblongata: Connected to the spinal cord, it regulates vital functions such as respiration, cardiovascular reflexes, and gastric secretions.
The brain is protected by the skull and cranial meninges that include dura mater, arachnoid, and pia mater.
Compare the following:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
(b) Resting potential and action potential
(a) Central Neural System (CNS) vs Peripheral Neural System (PNS)
Aspect | Central Neural System (CNS) | Peripheral Neural System (PNS) |
---|---|---|
Components | Brain and spinal cord | All the nerves associated with the CNS (brain and spinal cord) |
Functions | Information processing and control | Transmission of impulses from the CNS to the rest of the body and back |
Divisions | Not divided further | Somatic neural system and Autonomic neural system |
Structural Organisation | Complex, includes various parts like cerebrum, cerebellum, medulla, etc. | Less complex, mainly composed of nerve fibers (afferent and efferent) |
(b) Resting Potential vs Action Potential
Aspect | Resting Potential | Action Potential |
---|---|---|
Definition | Electrical potential difference across the plasma membrane when a neuron is not transmitting an impulse | Electrical potential change in the plasma membrane during stimulation |
Ion Permeability | Membrane is more permeable to K+ ions and nearly impermeable to Na+ ions | Membrane becomes freely permeable to Na+ ions allowing rapid influx |
Charge Distribution | Inner membrane surface is negative while outer surface is positive | Inner membrane surface becomes positive while outer surface becomes negative |
Mechanism | Maintained by the sodium-potassium pump, transporting 3 Na+ ions outwards for 2 K+ ions inwards | Generated by the influx of Na+ ions, reversing the polarity at the stimulated site |
State | Polarised state (more negatively charged inside) | Depolarised state (temporarily more positively charged inside) |
In summary, CNS is primarily for processing and control functions, whereas PNS is primarily for the transmission of impulses. Resting potential is a state of readiness in neurons, while action potential is the active state of impulse transmission.
Explain the following processes:
(a) Polarisation of the membrane of a nerve fibre
(b) Depolarisation of the membrane of a nerve fibre
(c) Transmission of a nerve impulse across a chemical synapse
(a) Polarisation of the membrane of a nerve fibre
Polarisation of the membrane of a nerve fibre occurs when the neuron is at rest. The key points include:
The axonal membrane is more permeable to potassium ions (K+) and nearly impermeable to sodium ions (Na+).
Because the axoplasm has a high concentration of (K^+) and negatively charged proteins, and the external fluid has a high concentration of (Na^+), there is a concentration gradient.
The sodium-potassium pump actively transports 3 (Na^+) out of the cell and 2 (K^+) into the cell.
As a result, the outer surface of the membrane is positively charged while the inner surface is negatively charged, creating a resting potential.
(b) Depolarisation of the membrane of a nerve fibre
Depolarisation occurs when a stimulus triggers the nerve fibre:
Upon stimulation, the membrane at the site becomes freely permeable to Na+, leading to a rapid influx of (Na^+).
This reverses the membrane polarity at that site, i.e., the outer surface becomes negatively charged and the inner surface becomes positively charged.
The resulting change in electrical potential is called the action potential or nerve impulse.
This depolarisation propagates along the length of the axon, conducting the nerve impulse.
(c) Transmission of a nerve impulse across a chemical synapse
Chemical synapse transmission involves neurotransmitters and occurs as follows:
When the action potential arrives at the axon terminal, it stimulates synaptic vesicles to move toward the membrane.
The vesicles fuse with the membrane and release neurotransmitters into the synaptic cleft.
These neurotransmitters bind to specific receptors on the post-synaptic membrane.
The binding opens ion channels in the post-synaptic membrane, allowing the entry of ions and generating a new potential.
This new potential can be excitatory or inhibitory, depending on the type of neurotransmitter released.
These processes highlight how neurons communicate and transmit signals, crucial for the functioning of the nervous system.
Draw labelled diagrams of the following:
(a) Neuron
(b) Brain
(a) Neuron
Dendrites
Cell Body
Axon
Synaptic Knob
(b) Brain
Forebrain
Cerebrum
Thalamus
Hypothalamus
Midbrain
Hindbrain
Pons
Cerebellum
Medulla
Write short notes on the following:
(a) Neural coordination
(b) Forebrain
(c) Midbrain
(d) Hindbrain
(e) Synapse
(a) Neural coordination
Neural coordination is the process through which the neural system ensures the synchronized functioning of different organs and systems in the body. It involves the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which consists of nerves that connect the CNS to other parts of the body. Neural coordination enables rapid and precise adjustments to maintain homeostasis and respond to external stimuli.
(b) Forebrain
The forebrain consists of the cerebrum, thalamus, and hypothalamus. The cerebrum is the largest part and is divided into two hemispheres connected by the corpus callosum. It includes the cerebral cortex, which is involved in complex functions like memory, sensory perception, and motor commands. The thalamus serves as a relay station for sensory and motor signals, while the hypothalamus regulates vital functions such as body temperature, hunger, thirst, and release of hormones.
(c) Midbrain
The midbrain is located between the thalamus/hypothalamus of the forebrain and the pons of the hindbrain. It acts as a conduit for auditory and visual signals and contains the cerebral aqueduct. The dorsal part, corpora quadrigemina, consists of four rounded swellings responsible for processing auditory and visual information.
(d) Hindbrain
The hindbrain includes the pons, cerebellum, and medulla oblongata. The pons contains nerve fibers that connect different brain regions and plays a role in regulating respiratory rhythms. The cerebellum coordinates voluntary movements and balance. The medulla oblongata connects the brain to the spinal cord and regulates vital functions such as heart rate, respiratory rate, and digestion.
(e) Synapse
A synapse is a junction between two neurons or between a neuron and a muscle cell. It allows the transmission of electrical or chemical signals. Chemical synapses involve neurotransmitter release into a synaptic cleft, binding to receptors on the post-synaptic cell, leading to the propagation or inhibition of the signal. Electrical synapses allow direct passage of current between cells, providing faster impulse conduction.
Give a brief account of Mechanism of synaptic transmission.
Mechanism of Synaptic Transmission
Synaptic transmission is the process through which a nerve impulse is transmitted from one neuron to another or to an effector cell. This process occurs at synapses, which can be either electrical or chemical.
Electrical Synapses
Proximity: The membranes of pre- and post-synaptic neurons are in very close proximity.
Transmission: Electrical current flows directly from one neuron to another.
Speed: Transmission is very rapid.
Rarity: These synapses are rare in humans.
Chemical Synapses
Separation: The membranes of pre- and post-synaptic neurons are separated by a synaptic cleft filled with fluid.
Neurotransmitters: Chemicals called neurotransmitters are involved in impulse transmission.
Release: When an impulse arrives at the axon terminal, it causes the synaptic vesicles to move towards the membrane.
Exocytosis: These vesicles fuse with the plasma membrane and release neurotransmitters into the synaptic cleft.
Receptor Binding: The neurotransmitters bind to specific receptors on the post-synaptic membrane.
Ion Channels: Binding opens ion channels, allowing ions to enter, which generates a new potential in the post-synaptic neuron.
Excitatory or Inhibitory: The new potential can be either excitatory or inhibitory, depending on the neurotransmitter.
Key Points:
Presynaptic Neuron: Releases neurotransmitters.
Synaptic Cleft: The gap where neurotransmitters are released.
Postsynaptic Neuron: Receives the neurotransmitters, leading to ion channel opening.
This process ensures that nerve impulses are transmitted efficiently from one neuron to another or to target cells like muscle or gland cells.
Explain the role of $\mathrm{Na}^{+}$in the generation of action potential.
During the generation of an action potential, the role of $\mathrm{Na}^{+}$ (sodium ions) is crucial. Here’s a step-by-step explanation of its role:
Resting State: In a resting neuron, the axonal membrane is more permeable to $\mathrm{K}^{+}$ (potassium ions) and nearly impermeable to $\mathrm{Na}^{+}$, maintaining a negative charge inside the axon and a positive charge outside.
Depolarization: When a stimulus is applied, the membrane at the site becomes freely permeable to $\mathrm{Na}^{+}$ ions. This permeability causes an influx of $\mathrm{Na}^{+}$ ions into the neuron.
Reversal of Polarity: The rapid influx of $\mathrm{Na}^{+}$ reverses the polarity of the membrane at that site, making the inside of the axon positively charged relative to the outside. This reversal of polarity is known as depolarization.
Action Potential: The depolarized state where the inside of the neuron is positively charged compared to the outside is called the action potential. It is essentially the nerve impulse.
Propagation: The depolarization at one site causes adjacent areas to depolarize, allowing the action potential to propagate along the length of the axon.
Repolarization: Shortly after $\mathrm{Na}^{+}$ entry, permeability to $\mathrm{K}^{+}$ ions increases, and $\mathrm{K}^{+}$ ions exit the neuron, restoring the negative charge inside the axon (repolarization).
Restoration: Finally, the sodium-potassium pump actively transports $\mathrm{Na}^{+}$ out of the cell and $\mathrm{K}^{+}$ into the cell to restore the original ionic balance, maintaining the resting potential.
Summary: $\mathrm{Na}^{+}$ ions are essential for the depolarization phase of the action potential, leading to the generation and propagation of the nerve impulse.
Differentiate between:
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Thalamus and Hypothalamus
(d) Cerebrum and Cerebellum
(a) Myelinated and Non-Myelinated Axons
Myelinated Axons:
Covering: Have a myelin sheath formed by Schwann cells.
Nodes of Ranvier: Present, gaps between adjacent myelin sheaths.
Conduction Speed: Faster due to saltatory conduction.
Location: Found in spinal and cranial nerves.
Non-Myelinated Axons:
Covering: Enclosed by a Schwann cell but without forming a myelin sheath.
Nodes of Ranvier: Absent.
Conduction Speed: Slower compared to myelinated axons.
Location: Found in autonomous and somatic neural systems.
(b) Dendrites and Axons
Dendrites:
Structure: Short and branched.
Function: Transmit impulses towards the cell body.
Content: Contain Nissl's granules.
Axons:
Structure: Long and usually unbranched except at the distal end.
Function: Transmit impulses away from the cell body to a synapse or neuro-muscular junction.
Special Features: Distal end forms synaptic knobs containing neurotransmitters.
(c) Thalamus and Hypothalamus
Thalamus:
Location: Part of the forebrain.
Function: Major coordinating center for sensory and motor signaling.
Hypothalamus:
Location: Lies at the base of the thalamus.
Function: Controls body temperature, hunger, thirst, and several autonomic functions. Contains neurosecretory cells that secrete hypothalamic hormones.
(d) Cerebrum and Cerebellum
Cerebrum:
Location: Part of the forebrain, forms the major part of the human brain.
Function: Responsible for voluntary movements, sensory perception, memory, communication and complex cognitive functions.
Special Features: Divided into left and right hemispheres connected by the corpus callosum.
Cerebellum:
Location: Part of the hindbrain.
Function: Maintains balance, coordination, and posture.
Special Features: Highly convoluted surface to accommodate more neurons.
Answer the following:
(a) Which part of the human brain is the most developed?
(b) Which part of our central neural system acts as a master clock?
(a) The cerebrum is the most developed part of the human brain.
(b) The hypothalamus acts as a master clock in our central neural system.
Distinguish between:
(a) afferent neurons and efferent neurons
(b) impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre
(c) cranial nerves and spinal nerves.
(a) Afferent Neurons vs. Efferent Neurons
Afferent Neurons:
Function: Transmit impulses from tissues/organs to the CNS (Central Nervous System).
Direction: Carry sensory information towards the brain and spinal cord.
Efferent Neurons:
Function: Transmit regulatory impulses from the CNS to the concerned peripheral tissues/organs.
Direction: Carry motor information away from the brain and spinal cord to muscles and glands.
(b) Impulse Conduction in Myelinated Nerve Fibre vs. Unmyelinated Nerve Fibre
Myelinated Nerve Fibre:
Structure: Axons are enveloped with Schwann cells forming a myelin sheath.
Conduction: Impulses are conducted in a saltatory manner, jumping from one node of Ranvier to the next, which makes it faster.
Unmyelinated Nerve Fibre:
Structure: Axons are enclosed by a Schwann cell but do not have a myelin sheath.
Conduction: Impulses are conducted in a continuous manner along the entire length of the axon, making it slower.
(c) Cranial Nerves vs. Spinal Nerves
Cranial Nerves:
Origin: Emerge directly from the brain.
Number: There are 12 pairs of cranial nerves.
Function: Mainly associated with the head and neck regions; control functions such as sight, smell, taste, and hearing.
Spinal Nerves:Origin: Emerge from the spinal cord.Number: There are 31 pairs of spinal nerves.Function: Connect the spinal cord with the rest of the body; involved in both sensory and motor functions.
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Understanding Neural Control and Coordination: Class 11 Notes
Neural control and coordination are vital processes that enable an organism to perform and regulate physiological functions seamlessly. This comprehensive guide will take you through the basics and crucial aspects of the neural system in human beings, which is a key topic for class 11 biology students.
Overview of Neural Control and Coordination
Introduction to Neural Control and Coordination
Neural control and coordination refer to the mechanisms by which the human body maintains functional harmony among its various organs and systems. This is essential for maintaining homeostasis, which is the stable equilibrium in the internal environment of the body.
Importance of Neural Coordination in Physiological Functions
The coordinated activities of different organs ensure they work in synchrony. For example, during physical exercise, the neural system helps in balancing the increased oxygen demand by adjusting the rate of respiration, heartbeat, and blood flow.
Human Neural System
Central Neural System (CNS)
The CNS, consisting of the brain and spinal cord, serves as the control centre for the body. It processes information from various parts of the body and sends out instructions.
Components of CNS: Brain and Spinal Cord
- Brain: The brain processes sensory information and controls cognitive functions like thought and memory.
- Spinal Cord: The spinal cord conducts motor information from the brain to peripheral organs and sensory information from these organs to the brain.
Functions of CNS
The CNS controls voluntary movements and involuntary functions like heart rate, respiration, and reflex actions.
Peripheral Neural System (PNS)
The PNS comprises nerves that connect the CNS to the rest of the body.
-
Afferent and Efferent Nerve Fibres
- Afferent Nerve Fibres: Transmit information from organs/tissues to the CNS.
- Efferent Nerve Fibres: Carry instructions from the CNS to organs/tissues.
-
Divisions of PNS
- Somatic Neural System: Relays impulses from CNS to skeletal muscles.
- Autonomic Neural System: Transmits impulses from CNS to involuntary organs.
Visceral Nervous System: A part of the PNS that connects nerve fibres to the viscera (internal organs).
Neuron as the Structural and Functional Unit
Structure of a Neuron
A neuron consists of three main parts: cell body, dendrites, and axon.
- Cell Body: Contains the nucleus and other cellular organelles.
- Dendrites: Branch-like structures that receive impulses and convey them to the cell body.
- Axon: A long fibre that transmits impulses away from the cell body to other neurons or muscles.
Types of Neurons
Neurons can be classified into three types based on their structure:
- Multipolar Neurons: One axon and multiple dendrites, found in the cerebral cortex.
- Bipolar Neurons: One axon and one dendrite, found in the retina.
- Unipolar Neurons: Single axon, usually found in the embryonic stage.
Myelinated vs. Non-myelinated Nerve Fibres
- Myelinated Nerve Fibres: Surrounded by a myelin sheath, enabling faster transmission.
- Non-myelinated Nerve Fibres: Lack a myelin sheath, found in somatic and autonomic neural systems.
Generation and Conduction of Nerve Impulse
Polarisation and Resting Potential
In a resting state, neurons exhibit a specific electrical charge difference across their membranes, known as the resting potential.
Action Potential and Depolarisation
When a stimulus is applied, the neuronal membrane's permeability changes, leading to a rapid influx of Na+ ions, and subsequent depolarisation. This process generates an action potential, otherwise known as a nerve impulse.
Process of Repolarisation
Following depolarisation, the membrane's permeability to K+ ions increases, restoring the resting potential.
Transmission of Impulses
Electrical Synapses
At electrical synapses, ions flow directly from one neuron to another, allowing rapid transmission.
Chemical Synapses
Chemical synapses involve neurotransmitters that cross the synaptic cleft to carry the impulse to the next neuron.
Mermaid.js Diagram Representing Synapse:
graph TD;
A[Presynaptic Neuron] -->|Neurotransmitters release| B[Synapse]
B -->|Signal transmitted| C[Postsynaptic Neuron]
style B fill:#f9f,stroke:#333,stroke-width:2px;
Central Neural System in Detail
Forebrain
Cerebrum, Thalamus, and Hypothalamus: The forebrain consists of the cerebrum, which is further divided into two hemispheres connected by the corpus callosum. The thalamus acts as a relay centre, while the hypothalamus controls vital functions like temperature regulation and hunger.
Midbrain
Situated between the forebrain and hindbrain, the midbrain integrates sensory information.
Hindbrain
The hindbrain is composed of:
- Pons: Relays signals between different brain parts.
- Cerebellum: Manages motor control and coordination.
- Medulla Oblongata: Regulates involuntary functions like heart rate and respiration.
Coordination and Homeostasis
Role of Neural System in Maintaining Homeostasis
The neural system ensures the internal conditions of the body remain stable amid changes in the external environment.
Interaction Between Neural and Endocrine Systems
The neural and endocrine systems work together to coordinate physiological functions through electrical impulses and hormones, respectively.
Frequently Asked Questions (FAQs)
FAQs Related to Neural Control and Coordination for Class 11
- What is the key role of the neural system in homeostasis?
- How does the CNS differ from the PNS?
- What are the major functions of the brain's forebrain, midbrain, and hindbrain?
This article aims to provide students with a clear understanding of neural control and coordination, a critical subject in class 11 biology. The various sections delve into the structural and functional aspects of the human neural system, making the concepts easier to grasp.
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