BIO 105: General and Special Senses (Chapters 23 & 24)

A comprehensive set of questions and answers covering general and special senses, receptor function, receptor types, sense organs, and major disorders based on the lecture notes.

What is the difference between general senses and special senses?

General senses are somatic receptors distributed widely throughout the body; special senses are localized complex organs for smell, taste, vision, hearing, and balance.

How do receptors respond to stimuli in the receptor response process?

They convert stimuli into nerve impulses (generator/receptor potentials leading to action potentials).

What is a receptor potential?

A local potential that develops in the receptor’s membrane when an adequate stimulus acts on the receptor and may trigger an impulse.

What does adaptation mean in sensory receptors?

A decrease in receptor potential (or firing rate) over time in response to a continuous stimulus.

Where are special senses located compared to general senses?

Special senses are localized in complex organs; general senses are distributed as microscopic receptors throughout the body.

What are exteroceptors?

Receptors on or near the body surface that provide information about the external environment (cutaneous receptors).

What are interoceptors (visceroceptors)?

Located internally, within body organs; monitor the internal environment.

What are proprioceptors and where are they located?

A type of visceroceptor located in skeletal muscle, joint capsules, and tendons; provide information about body position and movement.

What are the two types of proprioceptors mentioned, and what do they provide?

Tonic and phasic proprioceptors; provide information on muscle length and body position.

Name the six receptor classifications by stimulus.

Mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, photoreceptors, osmoreceptors.

What are free nerve endings and what do they primarily detect?

Widely distributed nerves endings that are primary nociceptors for pain.

What are Meissner corpuscles and where are they especially abundant?

Tactile (Meissner) corpuscles detect light touch and are abundant in hairless skin (e.g., fingertips, lips).

What are Pacinian (Lamellar) corpuscles and what do they detect?

Encapsulated receptors in deep dermis and joints that detect deep pressure and high-frequency vibration; they adapt rapidly.

What are Merkel discs and what is their role?

Tactile receptors involved in sustained, discriminative touch, located in the epidermal ridges.

What is the function of muscle spindles and which fibers carry their information?

Detect changes in muscle length; Ia (fast, large-diameter) and II (slower) afferent fibers carry the signals to the brain.

What do Golgi tendon organs detect and which fibers carry their information?

Detect excessive muscle tension/contraction; Ib sensory neurons carry the information.

What are olfactory receptors composed of?

Olfactory cilia, olfactory sensory neurons, olfactory epithelium, and supporting olfactory cells.

What is the olfactory pathway from receptor to brain?

Odorant threshold → receptor potential → action potential → olfactory nerve in the olfactory bulb → olfactory tract → thalamus and olfactory centers for interpretation and memory.

What are gustatory cells and where are they located?

Chemo-receptive sensory cells in taste buds; taste buds are the taste-receptive organs.

How many primary tastes are recognized and what are they?

Five primary tastes: sweet, sour, salty, bitter, and umami.

Describe the neural pathway for taste from the tongue to the cortex.

Anterior 2/3 via facial nerve VII; posterior 1/3 via glossopharyngeal nerve IX; to medulla, then thalamus, and to the gustatory cortex.

What are the three divisions of the ear and their general roles?

External ear (captures sound), middle ear (ossicles transmit vibrations), inner ear (cochlea for hearing and vestibular organs for balance).

What components make up the external ear?

Auricle (pinna) and external acoustic/meatus.

What are the three auditory ossicles in the middle ear?

Malleus (hammer), Incus (anvil), Stapes (stirrup).

What structures connect the middle ear to the nasopharynx?

The auditory (Eustachian) tube.

What is the role of the tympanic membrane?

It vibrates in response to sound waves and transmits energy to the ossicles.

What are the oval and round windows?

Oval window receives vibrations from the stapes; round window relieves pressure in the inner ear.

What are the main components of the inner ear?

Bony labyrinth and membranous labyrinth containing the cochlea, endolymph, and perilymph.

What structures are involved in balance within the inner ear?

Vestibule (utricle and saccule) and three semicircular canals with ampullae and ducts.

What is static equilibrium and what organ helps detect it?

Maintenance of head/body position when stationary; detected by otoliths in the macula of the vestibule.

What is dynamic equilibrium and which structures detect it?

Maintenance of balance during motion; detected by the semicircular ducts and the cupula in the ampullae.

What is the role of otoliths in the vestibular apparatus?

Otoliths add weight to the macula to detect head position and linear acceleration via hair cell deflection.

What is the cupula and where is it located?

A gelatinous structure in the semicircular ducts that bends with endolymph flow to sense angular acceleration.

Which nerve carries vestibular information to the brain?

The vestibular portion of cranial nerve VIII (vestibulocochlear nerve).

What are the external structures of the eye?

Eyebrows, eyelashes, eyelids, conjunctiva, palpebral fissure, and canthus.

What are extrinsic and intrinsic eye muscles?

Extrinsic: six extraocular muscles (superior, inferior, medial, lateral rectus; superior/inferior oblique). Intrinsic: iris and ciliary muscle.

What are the layers of the eyeball and which layer contains the retina?

Outer fibrous layer, middle vascular layer, inner retina (retina is the neural layer). The optic nerve (CN II) extends from the retina to the brain.

What changes occur during near vision (three-part near response)?

Increased curvature of the lens, pupil constriction, and convergence of the eyes.

What is the near reflex photopupillary response?

Constriction of the pupil in response to near vision or bright light.

What happens to the pupil during bright light or near vision?

Pupil constriction (miosis) to limit light and aid focus.

What is convergence of the eyes?

Movement of the eyes medially to maintain single binocular vision on a near object.

What are common refractive/disorder terms and their meanings?

Hyperopia (farsightedness) and myopia (nearsightedness); cataracts (clouding of the lens).

What is glaucoma?

Increased intraocular pressure that can damage the retina and optic nerve.

What are retinal disorders mentioned?

Retinal detachment and diabetic retinopathy (bleeding in retinal vessels with abnormal new vessel growth).

What is the function of the cochlea?

A part of the inner ear involved in hearing.

What are endolymph and perilymph?

Endolymph fills the membranous labyrinth; perilymph fills the space between the bony and membranous labyrinths.

What is the role of the optic nerve in vision?

Transmits visual information from the retina to the brain as the second cranial nerve (CN II).