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Neural Control and Coordination - Sensory perception

Grade 11CBSEBiology

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

🔑Concepts

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The human eye consists of three layers: the external sclera (with the transparent cornea), the middle choroid (containing the ciliary body and iris), and the inner retina.

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The retina contains two types of photoreceptor cells: Rods (for scotopic/twilight vision, containing the protein rhodopsin) and Cones (for photopic/daylight and color vision).

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The fovea is a thinned-out portion of the retina where only cones are densely packed, providing the highest visual acuity (resolution).

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Mechanism of vision: Light causes the dissociation of retinal (an aldehyde of Vitamin A) from opsin (a protein). This change in structure alters membrane permeability, generating action potentials in the ganglion cells through the bipolar cells.

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The human ear is divided into the outer ear, middle ear, and inner ear. The middle ear contains three ossicles: Malleus, Incus, and Stapes, which increase the efficiency of sound wave transmission.

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The inner ear consists of the bony labyrinth and the membranous labyrinth. The coiled portion is the cochlea, which is the main organ for hearing.

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The Organ of Corti, located on the basilar membrane, contains hair cells that act as auditory receptors. These cells convert mechanical vibrations into nerve impulses.

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The vestibular apparatus is responsible for maintaining body balance and posture. It consists of three semi-circular canals and the otolith organs (saccule and utricle).

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Dynamic equilibrium is maintained by the crista ampullaris in the semicircular canals, while static equilibrium and linear acceleration are sensed by the macula in the otolith organs.

📐Formulae

Visual Pigment Reaction: Rhodopsin→LightOpsin+Retinal\text{Visual Pigment Reaction: } Rhodopsin \xrightarrow{Light} Opsin + Retinal

Sound Amplification: PInner_Ear≈20 to 22×PTympanic_Membrane\text{Sound Amplification: } P_{Inner\_Ear} \approx 20 \text{ to } 22 \times P_{Tympanic\_Membrane}

Retinal=Aldehyde of Vitamin A\text{Retinal} = \text{Aldehyde of Vitamin A}

Nerve Impulse Generation: ΔVmembrane→Action Potential\text{Nerve Impulse Generation: } \Delta V_{membrane} \rightarrow \text{Action Potential}

💡Examples

Problem 1:

Trace the path of light through the human eye until it reaches the photoreceptors.

Solution:

Cornea →\rightarrow Aqueous humor →\rightarrow Pupil (controlled by Iris) →\rightarrow Lens →\rightarrow Vitreous humor →\rightarrow Retina (Photoreceptors).

Explanation:

Light rays in the visible spectrum are focused on the retina through the cornea and lens, triggering the photochemical reaction in rods and cones.

Problem 2:

Explain how sound waves are converted into nerve impulses in the ear.

Solution:

Tympanic membrane →\rightarrow Ear ossicles →\rightarrow Oval window →\rightarrow Perilymph of cochlea →\rightarrow Basilar membrane ripple →\rightarrow Hair cells press against Tectorial membrane →\rightarrow Nerve impulse.

Explanation:

Mechanical vibrations are amplified by the ossicles and cause fluid movement in the cochlea, which moves the basilar membrane. The bending of hair cells against the tectorial membrane generates an action potential in the auditory nerve.

Problem 3:

What happens to the visual pigment when light strikes the retina?

Solution:

When light (hνh\nu) strikes the retina, the retinal dissociates from the protein opsin.

Explanation:

The dissociation of RetinalRetinal from OpsinOpsin causes a conformational change in the protein, which leads to a change in membrane permeability to ions like Na+Na^+, initiating a neural signal.

Sensory perception - Revision Notes & Key Diagrams | CBSE Class 11 Biology