Short & Long Question Answers with Solution: Neural Control and Coordination | Biology for SSS 3 PDF Download

Short Answer Type Questions

Q1: What are the functions of the Eustachian tube?
Ans: The eustachian tube, also known as the pharyngotympanic tube, serves several important functions, including:

• Assisting in the drainage of secretions from the middle ear.
• Connecting the middle ear cavity to the nasopharynx.
• Equalizing the pressure between the middle ear and the surrounding atmosphere.

Q2: Explain the types of reflexes
Ans: There are two categories of reflexes: simple, or unconditioned, reflexes, and conditioned reflexes.

• Simple reflexes are regulated by the spinal cord rather than the brain. For instance, an increase in heart rate upon hearing a loud noise is an example of a simple reflex. Other instances of simple reflexes encompass actions like sneezing, coughing, vomiting, and swallowing.
• Conditioned reflexes, on the other hand, involve the brain, particularly the cerebrum. Examples of conditioned reflexes encompass activities such as swimming, dancing, driving, cycling, and so forth.

Q3: What is the role attributed to the Eustachian tube?
Ans: This structure links the pharynx to the middle ear cavity and plays a role in balancing the pressures on either side of the eardrum. Typically, there is a valve near the pharyngeal end of the tube that remains shut. However, it opens during actions like swallowing, yawning, or sudden shifts in altitude, allowing air to move in or out of the tympanic cavity and thereby equalizing the air pressure on both sides of the tympanic membrane.

Q4: Enumerate eye disorders.
Ans: The eye disorder is:

• Night blindness
• Myopia
• hypermetropia
• Colour blindness
• Conjunctivitis
• Strabismus 
• Cataract
• Glaucoma
• Presbiopia
• Astigmatism

Q5: How could it affect a person’s CNS if he is attacked by a blow on the back of the neck?
Ans: This could result in a decline in cognitive functions or physical dysfunction. Additionally, it may disrupt emotional or behavioral well-being. Damage to the cervical region can result in tetraplegia. 

Q6: What do you mean by Schneiderian membrane?
Ans: The olfactory lining is referred to as the Schneiderian membrane, and it serves as a sensory component for the sense of smell.
This membrane comprises three distinct types of cells:

• Receptor cells
• Supporting cells
• Glandular cells of Bowman's gland

The intensity of the smell experience is contingent upon the quantity of activated receptors.

Q7: Write the similarities between computers and neural system.
Ans: Different organs contain sensory neurons that detect the environment and transmit this information to the brain, functioning much like input devices in computers. The human brain can be likened to a Central Processing Unit (CPU). The information collected by sensory neurons undergoes processing in the brain, which then directs specific organs to perform their functions accordingly. Ultimately, motor neurons, akin to output devices, transmit the commands from the brain to carry out actions.

Q8: Mention some sensory organs.
Ans: The sensory organs are:

• Lateral line organ
• Jacobson organ
• Johnston’s organ
• Loreal pit
• Ampullae of Lorenzini.

Q9: State the difference between chemical and electrical transmission.
Ans: The differences are as below:


Q10: What are the receptors present on the skin?
Ans: The receptors are:

• Meissner’s corpuscles for touch.
• Krause’s End bulbs for cold
• Ruffini end bulb for hot
• Paccinian’s corpuscles for pressure
• Free nerve endings for pain.

Q11: Answer the following questions:

• Which part of the ear determines the pitch of the sound?
• Which is the most developed part of the brain?
• Which part of the central nervous system is called the master clock?

Ans: 

• The pitch of sound is determined by the cochlea.
• The forebrain is the most extensive and highly developed section of the brain.
• The hypothalamus serves as the body's central timekeeping mechanism.

Q12: What would affect the person’s CNS if someone received a blow on the back of the neck?
Ans: Injuries to the cervical region can lead to quadriplegia or tetraplegia. A blow to the back of the neck can cause a decline in physical capabilities and cognitive functions. Such injuries may also give rise to behavioral disruptions and emotional imbalances.

Q13: What do grey and white matter in the brain represent?
Ans: Grey matter comprises the outer layer of the brain and an inner layer of the spinal cord. It appears grey and consists of non-myelinated nerve fibers, leading to relatively slower nerve impulse transmission.
In contrast, white matter constitutes the inner portion of the brain and the outer region of the spinal cord. It appears white and is composed of myelinated nerve fibers, enabling very rapid nerve impulse transmission.

Q14: What is the significance of saltatory conduction?
Ans: In myelinated nerve fibers, the action potential leaps from one node of Ranvier to the next. This jumping action results in significantly faster nerve impulse conduction across myelinated nerve fibers, with a speed that is approximately 50 times faster than non-myelinated nerve fibers. This phenomenon is known as saltatory conduction and is of great importance in the efficient transmission of nerve impulses.

Q15:  Write a note on neural coordination.
Ans: The nervous system plays a vital role in providing neural coordination to efficiently manage a well-organized network of point-to-point connections.
The mechanisms involved in neural coordination include:

• Nerve impulse transmission.
• Coordination of impulses across a synapse.
• The physiology of reflex actions.

These processes collectively contribute to effective neural coordination within the body.

Long Answer Type Questions

Q1: Describe the structure of the internal and middle ear.
Ans: The ears serve as a pair of statoacoustic organs responsible for both balance and hearing. The human ear consists of three main parts: the middle ear, inner ear, and internal ear. The external ear includes the pinna, which is part of the auditory system. In the middle ear, there are three small bones arranged in a chain-like pattern: the malleus (hammer), incus (anvil), and stapes (stirrup). The stapes connects to the oval window of the cochlea, while the malleus is linked to the tympanic membrane. These three ossicles enhance the transmission of sound waves to the inner ear.
The middle ear is connected to the Eustachian tube, which extends into the pharynx and helps regulate pressure between the outer and middle ear. Moving on to the inner ear, it consists of a labyrinth of chambers filled with fluids within the temporal bone of the skull. This labyrinth has two parts: the membranous labyrinth and the bony labyrinth, which is a series of channels. Inside these channels lies the membranous labyrinth surrounded by a fluid known as perilymph and containing another fluid called endolymph. The cochlea, a coiled structure, is part of this labyrinth and features two major canals: the upper vestibular canal and the lower tympanic canal, separated by a small cochlear duct. Both canals are filled with perilymph, while endolymph is present in the cochlear duct. The walls of the membranous labyrinth are aligned with the fenestra ovalis at the base of the scala vestibuli and the fenestra rotunda at the lower end of the scala tympani.

Q2: Explain the role of sodium in the generation of the action potential.
Ans: Upon stimulation, the nerve membrane becomes highly permeable to sodium ions.
After stimulation, there is a swift inflow of sodium ions, leading to a reversal in polarity. In other words, the outer surface of the membrane becomes negatively charged while the inner side becomes positively charged.
This disparity in electrical potential across the membrane is referred to as the action potential, which is also known as the nerve impulse. Sodium ions play a crucial role in initiating the action potential.

Q3: List the human forebrain parts representing their respective functions.
Ans: The human forebrain is composed of three major parts: the cerebrum, hypothalamus, and thalamus. The cerebrum is the largest component of the human brain and is divided into two halves, the left and right cerebral hemispheres, which are connected by a bundle of nerve fibers called the corpus callosum. The cerebral hemispheres are characterized by a folded outer layer known as the cerebral cortex, which appears gray due to the presence of neuron cell bodies, earning it the name "grey matter." The cerebral cortex contains sensory areas, motor areas, and extensive regions responsible for various functions such as intersensory associations, communication, and memory, known as association areas.
Beneath the cerebral cortex lies the inner part of the cerebral hemisphere, which is composed of nerve fiber tracts covered in a myelin sheath. This myelinated region imparts a white appearance to this layer, leading to its designation as "white matter." The thalamus, located within the cerebrum, plays a crucial role in coordinating motor and sensory signals. Situated below the thalamus is the hypothalamus, which houses several centers responsible for regulating impulses related to eating, drinking, and body temperature. Additionally, the hypothalamus contains neurosecretory cells that produce hormones referred to as hypothalamic hormones.
The limbic system comprises the internal portions of the cerebral hemispheres and associated deep structures like the hippocampus and amygdala. This system, in conjunction with the hypothalamus, is involved in controlling sexual behavior, expressing emotions, motivating behavior, and more.

Q4: Difference between myelinated and non-myelinated axons.
Ans:
 
Q5: Describe the phenomena of release and transport of a neurotransmitter.
Ans: Synapses are connections that facilitate the transmission of nerve signals from one neuron to another. These connections are formed between the cell membranes of the sending (presynaptic) neuron and the receiving (postsynaptic) neuron, and they may or may not be separated by a small gap called the synaptic cleft. In chemical synapses, which are the most common type, the membranes of the presynaptic and postsynaptic neurons are separated by this synaptic cleft. The transmission of nerve signals across these synapses is accomplished through the use of chemical messengers called neurotransmitters.
Within the axon terminals of the presynaptic neuron, there are small sacs called vesicles that contain these neurotransmitters. When a nerve signal arrives at the axon terminal, it triggers the release of these neurotransmitters from the vesicles. These neurotransmitters are then released into the synaptic cleft, where they bind to specific receptors on the postsynaptic neuron's membrane. This binding process opens ion channels, allowing ions to enter the postsynaptic neuron. This influx of ions can generate a new electrical potential in the postsynaptic neuron, which can either excite or inhibit further nerve signal transmission.

Q6: What is the difference between resting and action potential?
Ans:

Q7: During resting potential, the axonal membrane is polarised. Explain the movement of positive and negative ions leading to polarisation.
Ans: When a nerve is not actively transmitting an impulse, the axoplasm contains a higher concentration of potassium ions and a lower concentration of sodium ions.
The surrounding fluid outside the axon contains a lower concentration of potassium ions and a higher concentration of sodium ions. This creates a concentration gradient.
To maintain this potential difference, the Na+-K+ pump comes into play. It operates by moving three sodium ions out of the cell and simultaneously bringing two potassium ions into the cell, thereby helping to uphold the ionic gradients across the resting membrane.
The membrane is described as polarized when its outer surface carries a positive charge, while its inner surface bears a negative charge.
The electrical potential difference present across the resting membrane is termed as the resting potential, and this condition of the resting membrane is referred to as polarization.

Q8: Differentiate between the thalamus and the hypothalamus.
Ans: Thalamus and hypothalamus are distinct regions in the brain with different functions:

• Thalamus is situated within the cerebrum and serves as a relay center for sensory information. It plays a role in selecting and directing sensory inputs to the cerebrum.
• Hypothalamus is located at the base of the thalamus and is responsible for regulating various physiological processes, including sexual behavior and emotional responses. Additionally, it contains neurosecretory cells that release hormones known as hypothalamic hormones.

Q9: Compare cranial nerves and spinal nerves.
Ans:

Q10: Draw a well-labelled diagram of the neuron.
Ans:
A neuron, also known as a nerve cell, is the basic functional unit of the nervous system in animals, including humans. Neurons play a crucial role in transmitting electrical and chemical signals within the nervous system, allowing for the communication of information throughout the body.
Structure of a Neuron:

• Cell Body (Soma): The central part of the neuron, called the cell body or soma, contains the nucleus and other organelles responsible for the cell's metabolic functions.
• Dendrites: Dendrites are branch-like extensions that protrude from the cell body. They serve as the input regions of the neuron, receiving signals from other neurons or sensory receptors. Dendrites receive incoming electrical signals in the form of neurotransmitters.
• Axon: The axon is a long, slender extension that carries electrical impulses away from the cell body. It is covered by a protective myelin sheath in many neurons, which speeds up the transmission of signals.
• Axon Terminal: At the end of the axon, there are numerous small structures called axon terminals or synaptic terminals. These structures are responsible for transmitting signals to other neurons or target cells through synapses.