Senses

Question 1

What are the two classifications of senses?

Answer 1

General senses - detected by sensory organs that exists as individual cells or receptor units; widely distributed throughout the body; also found in deep organs

Special sense - detected by large and complex organs, or localized grouping of sensory receptors

Question 2

What are the six types of encapsulated nerve endings? Describe their location and function.

Answer 2

Bulboid corpuscle - dermis, lips, eyelids, external genitals; touch

Lamellar corpuscle - around joints, mammary glands, external genitals; pressure, high-frequency vibration

Tactile corpuscle - fingertips and lips; fine touch, low-frequency vibration

Bulbous corpuscle - dermis and subcutaneous tissue of fingers; touch and pressure

Tendon organ - near junction of tendons and muscles; proprioception (sense of muscle tension)

Muscle spindle - skeletal muscle; proprioception (sense of muscle length)

Question 3

What is the sclera?

Answer 3

The “white” of the eye. (fibrous layer)

Question 4

What is the cornea?

Answer 4

Transparent “window” over iris. (fibrous layer)

Question 5

What is the conjuctiva?

Answer 5

Mucous membrane covering front of fibrous layer.

Question 6

What is the lacrimal gland?

Answer 6

Secretes tears. (fibrous layer)

Question 7

What is the choroid?

Answer 7

Pigmented, melanin-rich layer prevents scattering of light. (vascular layer)

Question 8

What is the iris?

Answer 8

The coloured part of the eye; the pupil is the hole in the center. (vascular layer)

Question 9

What is the lens?

Answer 9

Transparent body behind the pupil; focuses or refracts light rays on the retina. (vascular layer)

Question 10

What is the ciliary muscle?

Answer 10

Near front of vascular layer of eye, just outside the edge of the iris; contraction affects the shape of lens, thus altering focus for near objects.

Question 11

What is the retina?

Answer 11

Inner most sensory layer of the eye; contains various kinds of photoreceptors.

Question 12

What are cones?

Answer 12

Receptors for day and colour vision.

Question 13

What are rods?

Answer 13

Receptors for night and peripheral vision.

Question 14

What are ganglion cells?

Answer 14

Receptors for changing light patterns (days, months, seasons).

Question 15

Explain the visual pathway.

Answer 15

• Impulse travels from the rods and cones through the bipolar and ganglionic layers of retina
• Nerve impulse leaves the eye through the optic nerve; the point of exit is free of receptors and is therefore called a “blind spot”
• Visual interpretation occurs in the visual cortex of the of the occipital lobe of the cerebrum.

Question 16

What are the parts of the external ear?

Answer 16

• Auricle (pinna)
• External acoustic canal (curving canal, 2.5cm in length; contains ceruminous [wax] glands; ends at the tympanic membrane.

Question 17

What are the parts of the middle ear?

Answer 17

• Ear ossicles (malleus, incus, stapes)
• ends in the oval window
• the auditory tube (Eustachian tube) connects the middle ear to the throat

Question 18

What is otitis media?

Answer 18

Inflammation of the middle ear. (Ear infection)

Question 19

What are the parts of the inner ear?

Answer 19

• Bony labyrinth filled with perilymph
• Subdivided into the vestibule, semicircular canals, and cochlea
• membranous labyrinth filled with endolymph

Question 20

Explain the auditory pathway (hearing).

Answer 20

• Sound waves funneled by auricle into external acoustic canal and vibrate the tympanic membrane
• Vibrations of tympanic membrane are amplified by auditory ossicles and transmitted to the oval window
• Vibrations of the oval window trigger vibrations in perilymph, which in turn vibrates endolymph
• Sensory hair cells on the spiral organ (organ of corti) respond when bent by the movement of surrounding endolymph set in motion by sound waves

Question 21

What is static equilibrium?

Answer 21

• Sense of gravity
• Detected by ciliated hair cells (mechanoreceptors) of the two maculae in the vestibule
• When the head tilts, gravity pulls the heavy gel of each macula, bending the sensory cilia and producing a nerve signal

Question 22

What is dynamic equilibrium?

Answer 22

• Sense of speed and direction of movement
• Detected by ciliated hair cells (mechanoreceptors) of the crista ampullaris in the ampulla of each semicircular canal
• When speed or direction of movement of head changes, the flow of endolymph in the semicircular canals is altered, which causes change in the bending of sensory cilia (producing a nerve signal)

Question 23

What is the vestibular nerve?

Answer 23

• Carries nerve impulses from the equilibrium receptors of the vestibule; joins with cochlear nerve to form vestibulocochlear nerve (cranial nerve 8)

Question 24

What are gustatory cells?

Answer 24

• Chemoreceptors located in taste buds (cranial nerves 7 and 9 carry gustatory impulses)

Question 25

What are the primary taste modes?

Answer 25

Sweet - sugars
Sour - acids
Bitter - alkaline solutions
Salty - sodium ions
Metallic - metal ions
Umami (savory) - glutamate (an amino acid)

Question 26

Explain the olfactory pathway (smell).

Answer 26

• Olfactory receptors in olfactory mucosa of nasal cavity are extremely sensitive but easily adapt (become fatigued)
• Odor-causing chemicals initiate a nerve impulse that is carried on cranial nerve 1
• Olfaction has a strong relationship with emotions and memory through the limbic system

Question 27

How do the integration of senses contribute to posture and balance?

Answer 27

Both senses of equilibrium with vision and proprioception combine to help is maintain a safe body position