Sense Organs-Class 3

What are the two main branches of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS).

What is the role of sense organs in the nervous system?

They allow the brain to perceive external stimuli and respond to the outside world.

What are the three types of sensory receptors based on structural classification?

Encapsulated Ending, Free Nerve Ending, Specialized Receptor.

What are the three types of sensory receptors based on locational classification?

Proprioceptor, Interoceptor, Exteroceptor.

What are the five types of sensory receptors based on functional classification?

Thermoreceptors, Photoreceptors, Mechanoreceptors, Chemoreceptors, Nociceptors.

What do mechanoreceptors respond to?

Mechanical forces such as pressure, vibration, stretch, and motion.

What is the function of Meissner's Corpuscles?

They detect light touch and texture, located in the upper dermis.

What do Merkel Discs respond to?

Sustained pressure and light touch, located in the epidermis stratum basale.

What type of stimuli do Pacinian Corpuscles detect?

Deep pressure and high-frequency vibration, located in the deep dermis.

What is the role of Ruffini Endings?

They respond to skin stretch and play a role in proprioception.

What do hair follicle receptors detect?

They detect hair movement and sense light touch.

What are hair cells in the inner ear responsible for?

Hearing and balance, detecting sound vibrations.

What do thermoreceptors detect?

Temperature changes.

Where are peripheral thermoreceptors located?

In the skin, mucous membranes, and parts of the hypothalamus.

What are the two types of peripheral thermoreceptors?

Cold receptors and warm receptors.

What temperature range activates cold receptors?

Approximately 10°C to 35°C (50°F to 95°F).

What temperature range activates warm receptors?

Approximately 30°C to 45°C (86°F to 113°F).

What happens when temperatures exceed 45°C?

Nociceptors (pain receptors) begin to activate.

Where are central thermoreceptors found?

In the hypothalamus, spinal cord, and viscera.

What is the role of mechanoreceptors in the body?

They are needed for reflexes, coordination, balance, and spatial awareness.

What are the general senses?

Touch, pressure, pain, temperature, itch, and proprioception.

What are the special senses?

Sight, hearing, balance, smell, and taste.

What disorders are associated with vision?

Myopia, hyperopia, presbyopia, nyctalopia, astigmatism, and conjunctivitis.

What disorders are associated with hearing and smell?

Otitis media, types of deafness, Anosmia/dysosmia, and dysgeusia.

What is the role of nociceptors?

Nociceptors detect pain and are classified based on the type of stimulus they respond to.

What are the two types of fibers used by mechanical nociceptors?

Mechanical nociceptors often involve A-delta fibers, which are thin and myelinated, leading to sharp, localized pain.

What stimuli do thermal nociceptors respond to?

Thermal nociceptors respond to extreme heat or cold, outside the range for thermoreceptors, and also use A-delta fibers.

What type of pain do polymodal nociceptors detect?

Polymodal nociceptors respond to mechanical, thermal, and chemical stimuli, leading to dull, burning, or aching pain.

What are silent (or sleeping) nociceptors?

Silent nociceptors are normally inactive but become responsive during inflammation or injury, contributing to chronic pain and hyperalgesia.

What are the steps in the pathway of pain perception?

1. Stimulus activates nociceptors, sending signals via A-delta or C fibers. 2. Signal travels to spinal cord dorsal horn. 3. Signals are relayed via the spinothalamic tract to the thalamus and somatosensory cortex. 4. Processed as conscious pain perception, triggering reflexes or emotional responses.

What are the functions of nociceptors?

Nociceptors help with withdrawal reflexes, protect tissues, signal injury, and aid in healing.

What is the function of photoreceptors?

Photoreceptors in the retina respond to light and convert it into electrical signals, allowing the brain to form images and perceive color, brightness, and movement.

What are the two types of photoreceptors and their functions?

Rods detect light intensity and are sensitive to dim light for night vision; cones detect color and require bright light for daytime vision.

What do chemoreceptors detect?

Chemoreceptors detect chemical stimuli in the environment or body, playing a critical role in taste and smell.

How do olfactory chemoreceptors function?

Olfactory chemoreceptors in the nose detect airborne molecules and send signals via the olfactory nerve to the brain for sensory perception.

What is the role of gustatory chemoreceptors?

Gustatory chemoreceptors in taste buds detect chemicals in food and send signals through cranial nerves to help us taste flavors.

What is a fun fact about dogs' sense of smell?

Dogs have up to 300 million olfactory receptors in their noses, compared to about six million in humans.

What do proprioceptors help the body sense?

Proprioceptors help the body sense its own position, movement, and balance.

What are the three types of proprioceptors?

Muscle spindles detect muscle stretch, Golgi tendon organs detect tension in tendons, and joint receptors monitor joint angle, pressure, and movement.

What is the difference between general senses and special senses?

General senses are scattered throughout the body and provide constant status updates, while special senses are clustered in specialized head organs and provide rich, detailed information.

What is the primary function of general-sense receptors?

General-sense receptors keep you balanced, protected, and oriented without requiring conscious effort.

Where are general sensory receptors located in the body?

Skin layers, skeletal muscles, joint capsules, and visceral walls.

What type of receptor detects light touch?

Meissner corpuscle.

Provide a real-world example of deep pressure sensation.

Leaning on a desk with your elbow.

What is the function of nociceptors?

They detect pain, such as a prick from a needle.

What do proprioceptors help you sense?

Body position and movement without looking.

What type of receptor is responsible for itch sensation?

Free nerve endings.

What are the five basic taste qualities?

Sweet, salty, sour, bitter, and umami.

What structures are involved in the sense of vision?

Eyes (retinal photoreceptors).

How do hair cells in the cochlea function?

They turn sound waves into electrical signals for the brain to interpret.

What is the role of semicircular canals?

They detect head movements and gravity to maintain balance.

What is the function of taste buds?

They detect taste (gustation) on the tongue.

What is the primary function of the olfactory epithelium?

It detects odors for the sense of smell.

What percentage of sensory receptors are located in the eyes?

Approximately 70%.

What are the protective structures of the eye?

Eyebrows, eyelids, eyelashes, conjunctiva, lacrimal apparatus, and extrinsic eye muscles.

What is the fibrous layer of the eyeball?

The outer layer that includes the sclera and cornea.

What is the function of the choroid in the eye?

It provides oxygen and nutrients to the retina.

What are the two types of photoreceptors in the retina?

Rods (detect dim light and motion) and cones (detect color and detail).

What is the path of light through the eye?

Cornea → Aqueous humor → Pupil → Lens → Vitreous humor → Retina.

What happens to light when it reaches the retina?

Photoreceptors convert light into nerve impulses.

What is the role of the ciliary body in the eye?

It focuses the lens.

What part of the brain flips the upside-down image and combines input from both eyes into a 3D scene?

The occipital lobe.

What happens to the pupils in bright light and dim light?

In bright light, pupils constrict to protect photoreceptors; in dim light, pupils dilate to enhance sensitivity.

What are the three major regions of the ear?

Outer Ear, Middle Ear, Inner Ear.

What is the function of the tympanic membrane (eardrum)?

It vibrates when hit by sound.

What are the three tiny bones in the middle ear that amplify sound?

Malleus, Incus, and Stapes.

What is the role of the Eustachian tube?

It balances air pressure.

What is the function of the cochlea?

It is responsible for hearing.

What structures in the inner ear are responsible for balance?

Vestibule and Semicircular canals.

What is the process of hearing starting from sound waves entering the auditory canal?

1. Sound waves enter the auditory canal. 2. They hit the tympanic membrane, causing vibrations. 3. Vibrations pass through the ossicles, getting amplified. 4. The stapes taps the oval window of the cochlea. 5. Fluid in the cochlea moves, triggering hair cells in the organ of Corti. 6. Hair cells generate electrical signals. 7. Signals travel via the cochlear nerve to the auditory cortex.

How do louder sounds and higher pitches affect vibrations?

Louder sounds produce stronger vibrations; higher pitch corresponds to faster wave frequency.

What are the two structures in the vestibular system that help detect motion and head position?

Vestibule (utricle and saccule) and Semicircular Canals.

What is the role of the olfactory system in detecting smell?

It detects airborne molecules that bind to olfactory receptors, sending signals to the brain.

What are the steps involved in the process of smell?

1. Airborne molecules dissolve in mucus. 2. Molecules bind to olfactory receptors. 3. Receptors send impulses through the olfactory nerve. 4. Signals go to the olfactory bulb and olfactory cortex.

What are the functions of smell?

Detects hazards, enhances taste, and plays a role in social and emotional behavior.

What are the five basic tastes detected by the tongue?

Sweet, Salty, Sour, Bitter, Umami.

How does the tongue detect taste?

Chemicals dissolve in saliva, stimulate gustatory receptors in taste buds, and signals travel via facial, glossopharyngeal, and vagus nerves to the gustatory cortex.

What are common disorders associated with vision?

Myopia, Hyperopia, Presbyopia, Nyctalopia, Astigmatism, Conjunctivitis, Color Blindness.

What are the two types of deafness?

Conductive (problem with outer/middle ear) and Sensorineural (damage to cochlea or auditory nerve).

What is anosmia and dysosmia?

Anosmia is the loss of smell; dysosmia is distorted smell.

What is dysgeusia?

Altered or impaired taste.

What unique feature do olfactory neurons have?

They can regenerate regularly, which is rare for neurons.

What is the role of tiny otoliths in the vestibular system?

They shift with gravity, bending hair cells to help detect head position.

How does the brain process signals from the vestibular system?

Signals travel via the vestibular nerve to the brainstem and cerebellum to coordinate posture, maintain balance, and adjust eye movements.

What happens if the vestibular system is impaired?

You may feel dizzy, stumble, or lose orientation.