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Important Questions Class 11 Biology Chapter 21 Neural Control Coordination

The functionalities of the organ system/system in the human body should be in a controlled and coordinated pattern in order to support homeostasis. Coordination is brought about by the interaction of two or multiple organs which supplement the functions of each other. The neural system and the  endocrine system  coordinate in the human body thereby integrating all the movements of the organs so as to operate in a synchronized manner. This process is facilitated by a structured arrangement of point-to-point attachments for an immediate response. Read on to learn more.

Q.1. Arrange the following in the accurate order of their association in electrical impulse movement – Synaptic knob, Axon terminal, Axon, dendrites, Cell body. A.1.  Dendrites, Cell body, Axon, Axon terminal, Synaptic knob. Q.2. Name the retina cells that allows us to see coloured objects. A.2.  Cone cells. There are three kinds of cones that have characteristic photopigments which react to red, blue, and green light. Q.3. Rearrange the following in the sequential order of reception and transmission of sound waves from the eardrum – External auditory nerve, eardrum, cochlear nerve, malleus, stapes, incus, cochlea A.3.  Sound waves are received and transmitted in this order: External auditory nerve→ eardrum→malleus→Incus → Stapes → Cochlea → Cochlear nerve. Q.4. List the structures that protect the brain. A.4.  Cranium – 8 cranial bones form the hard outer covering for the brain Meninges – The brain is covered with three membranes called meninges. The pia mater, arachnoid membrane, and the dura mater Cerebrospinal fluid – It is present in the spaces between the meninges and absorbs shocks. Q.5. What do the white and grey matter in the human brain indicate? A.5.  The cerebral cortex is known as the grey matter as it appears grey in colour which is attributed to the neuron cell bodies imparting the colour. Fibres of the tracts are covered with the myelin sheath that forms the inner part of the cerebral hemisphere, imparting an opaque white appearance to the layer hence the white colour. Q.6. Where in the human brain is the centre for hunger located? A.6.  Hypothalamus Q.7. Name the sense organ involved in vertigo. A.7.  Vestibular apparatus of the inner ear. Q.8. Where is the hunger centre located in the human brain? A.8.  Hypothalamus. It is a small region of the brain, which is located at the base of the brain, near to the pituitary gland. Q.9. What are the three layers of the human eye?  A.9.  Lens, Aqueous humour and Vitreous humour are the three layers of the human eye. Q.10. Which is photosensitive part of the human eye? A.10.  The retina is mainly composed of light-sensitive cells known as rods and cones, therefore it is called the light-sensitive layer that lines the interior of the eye.

Q.1. State the difference between chemical and electrical transmission. A.1.  The differences are as below:

Q.2. Write the similarities between computers and neural system. ( Hint: CPU, input-output devices) A.2.  Various organs possess sensory neurons which sense the surroundings and send across the communication to the brain which is similar to the input device in computers. The  human brain  can be compared to the Central Processing Unit (CPU). The data that is gathered by the sensory neurons is processed by the brain which further commands the specific organ to work in accordance. Finally, the message is picked by the motor neurons that are similar to output devices. Q.3. How could it affect a person’s CNS if he is attacked by a blow on the back of the neck? A.3.  It would lead to an impairment of cognitive abilities or dysfunctionalities physically. Furthermore, it can also cause disturbance of emotional or behavioural functioning. Cervical damages can lead to tetraplegia. Q.4. What is the role attributed to the Eustachian tube? A.4.  It connects the pharynx with the middle ear cavity and aids in equalizing pressures on both the parts of the eardrum. There is a valve present towards the pharyngeal opening of the tube that remains closed usually. It opens during swallowing, yawning, an unexpected change in altitude when the air leaves or enters the tympanic cavity so as to stabilize the air pressure on both parts of the tympanic membrane. Q.5.What are the functions of the Eustachian tube? A.5.  The eustachian tube is also called a pharyngotympanic tube. The  Eustachian tube has many functions, the most notable are:

Q.1. Describe the phenomena of release and transport of a neurotransmitter. A.1.  Synapses are junctions that transmit nerve impulses from one to another neuron. It is produced through the membranes of the postsynaptic and presynaptic neuron that may be or may not be parted by a synaptic cleft which is a gap. The membranes of the presynaptic and postsynaptic neurons at a chemical synapse are divided by a space filled with fluid known as the synaptic cleft. The neurotransmitters transmit impulses at such synapses. The axon terminals possess vesicles that have the neurotransmitters. When an impulse arrives, it reaches the axon terminal and triggers the action of the synaptic vesicles supporting the membrane wherein they join with the plasma membrane to produce their neurotransmitters, all in the synaptic cleft, which in turn attach to their particular receptors situated on the postsynaptic membrane. This union unfolds ion channels permitting the entrance of ions which can produce a new potential in the postsynaptic neuron which can either be inhibitory or excitatory. Q.2. List the human forebrain parts representing their respective functions A.2.  The human forebrain comprises of the cerebrum, hypothalamus, and the thalamus. The main component of the human brain is formed by the cerebrum which is separated longitudinally by a cleft into 2 halves, named as the left and the right cerebral hemisphere which are linked by a tract of nerve fibres known as the corpus callosum. Cerebral hemisphere is covered by a cell layer known as the cerebral cortex having evident folds. Its greyish appearance attributed by the cell bodies of the neuron is the reason the cerebral cortex is termed as the grey matter. It contains sensory areas, motor areas, and large regions which are neither motor nor sensory in function, and are referred to as association areas responsible for functionalities such as intersensory associations, communication, and memory. The inner part of the cerebral hemisphere is constituted by the fibres of the tracts comprised of the myelin sheath. It is called as the white matter as they impart an opaque white appearance to the layer. The thalamus is contained in the cerebrum which coordinates the motor and sensory signalling. At the base of the thalamus is the hypothalamus, containing several centres regulating the impulse for eating, drinking and body temperature. It also has a number of neurosecretory cells that produce hormones known as hypothalamic hormones. The limbic system is formed by the internal parts of the cerebral hemispheres and a combination of related deep structures such as the hippocampus, amygdala, etc. This system accompanying the hypothalamus is concerned with controlling sexual behaviour, expressing emotional reactions, motivation, etc. Q.3. Describe the structure of the internal and middle ear. A.3.  Ears are a pair of a statoacoustic organ that helps in balancing and hearing. The human ear includes – the middle ear, the inner ear, and the internal ear. The pinna is a part of the auditory system and forms the external ear. The middle ear has 3 bones – the malleus(hammer), the stapes(stirrup) and incus(anvil) which are attached in a chain-like pattern. The stapes is connected to the oval window of cochlea and the malleus is connected to the tympanic membrane. These three bones or ossicles raises the productivity of communication of sound waves to the inner ear. The middle ear leads to the Eustachian tube that bridges along with the pharynx and controls the force between the outside and the middle ear. The inner ear comprises a labyrinth of chambers filled with fluids inside the temporal bone of the skull. The labyrinth has 2 parts – the membranous and the bony labyrinth(series of channels). Inside the channels lies the membranous labyrinth which is girdled by a fluid known as perilymph and filled with a fluid called endolymph. The labyrinth has a coiled structure called the cochlea. Which has 2 large canals – upper vestibular canal and a lower tympanic canal that is divided by a small cochlear duct. Both canals contain the perilymph with endolymph in the cochlear duct. Towards the base of the scala vestibuli, the membranous labyrinth walls are in sync with the fenestra ovalis and at the lower end of the scala tympani is the fenestra rotunda.

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They take place in the electric synapse.

They take place at a chemical synapse.

The synaptic cleft may or may not be present.

The electric current at electric synapses flows from one to another neuron through these synapses. Impulse transmission across an electrical transmission is fast always.

The neurotransmitter at the chemical synapse from the pre-synaptic neurons transfers to the post-synaptic neurons causing transmission of the impulse. Chemical transmission is slower.