Which structures make up the central nervous system?
The brain and spinal cord.
Which structures belong to the peripheral nervous system?
Cranial and spinal nerves.
Where do sensory (afferent) nerves carry information?
Into the brain and spinal cord.
Where do motor (efferent) nerves carry information?
From the CNS to effectors.
Which muscles do somatic motor nerves signal?
Skeletal muscles for voluntary action.
Which targets do autonomic motor nerves signal involuntarily?
Smooth muscle, cardiac muscle, and glands.
What is a sensory receptor?
A specialized dendrite that detects a certain type of stimulus.
What do exteroceptors detect?
Stimuli from outside the body, such as taste, hearing, and vision.
What do interoceptors detect?
Stimuli from inside the body, such as changes in blood pressure.
What do chemoreceptors, nociceptors, photoreceptors, mechanoreceptors, and thermoreceptors detect?
Nearby chemicals, chemicals released by damaged tissue, light, mechanical forces, and temperature changes, respectively.
What sequence produces conscious sensation?
Receptors respond to environmental stimuli, impulses travel to the cerebral cortex, and the stimuli are consciously perceived.
What reflex-related role do proprioceptors perform?
They help maintain muscle tone, equilibrium, and posture.
Where are cutaneous receptors located?
In the dermis.
Which sensations do cutaneous receptors make the skin detect?
Touch, pressure, pain, and temperature.
What are the five main taste types?
Sweet, sour, salty, bitter, and umami.
What percentage of perceived taste is actually due to smell?
About 80–90%.
Which three coats make up the eye?
The sclera, choroid, and retina.
Where is the anterior compartment, and which fluid does it contain?
Between the cornea and lens; aqueous humor.
What does the posterior compartment contain?
Vitreous humor.
What is visual accommodation?
A change in lens shape that focuses light on the retina to form an image.
Which two types of photoreceptors does the retina contain?
Rods and cones.
What kind of light are rods sensitive to?
Light.
Which visual pigment do rods contain?
Rhodopsin.
Which vitamin do rods require to function properly?
Vitamin A.
Where are cones located mostly?
In the fovea.
What happens to the lens in a cataract?
It becomes cloudy.
What causes glaucoma?
A buildup of fluid pressure in the eye.
What eyeball shape causes nearsightedness?
An eyeball that is too long.
What visual difficulty does nearsightedness cause?
Difficulty seeing distant objects.
Which ear regions are air-filled and function in hearing?
The outer and middle ear.
Which functions does the fluid-filled inner ear perform?
Hearing and balance.
What do the malleus, incus, and stapes do to sound waves?
They amplify them.
What does the stapes produce by vibrating against the oval-window membrane?
Fluid waves in the cochlea.
Which equilibrium function does the vestibule serve?
Gravitational equilibrium.
Which equilibrium function do the semicircular canals serve?
Rotational equilibrium.
Which sources send signals through somatic sensory nerves?
The skin, muscles, joints, and special senses.
What is the parasympathetic division associated with?
“Rest and digest.”
What is sensory adaptation?
A decrease in response to a repetitive stimulus, such as an odor.
Which skin receptors detect pain, heat, and cold?
Free nerve endings.
Which skin receptors detect touch?
Merkel disks, Krause end bulbs, root hair plexuses, and Meissner corpuscles.
Which skin receptors detect pressure?
Ruffini endings and Pacinian corpuscles.
About how many taste buds do adult humans have?
About 4,000.
Where are adult human taste buds located primarily?
On the tongue.
How many olfactory cells does smell depend on?
About 10–20 million.
Where are olfactory cells located in the nasal cavity?
In the roof of the nasal cavity.
What type of cells are olfactory cells?
Modified neurons.
What is the cornea, and how does it affect light?
The transparent portion of the sclera that refracts light.
What is the pupil’s role in the eyeball?
It allows light into the eyeball.
What does the iris regulate?
Pupil size.
What happens to the ciliary muscle during near focus?
It contracts.
Where are images focused on the retina?
At the fovea centralis.
What does the fovea centralis contain densely?
Cones.
What carries impulses from retinal sensory receptors to the brain?
The optic nerve.
What type of abnormality is color blindness?
A genetic abnormality.
Which colors are usually difficult to distinguish with color blindness?
Red and green.
In which group is color blindness most common?
Males.
What makes an image fuzzy in astigmatism?
An uneven cornea or lens.
What does the pinna do with sound waves?
It catches them.
What does the auditory canal direct sound waves toward?
The tympanic membrane.
What does the auditory tube connect to the middle ear?
The throat.
What determines pitch and volume in hearing?
Pitch depends on frequency; volume depends on amplitude.
Where are the hair cells that detect angular movement in each semicircular canal?
In the ampulla at its base.
What movement do ampulla hair cells detect?
Angular movement associated with rotational equilibrium.
Which organs contain hair cells detecting head movement in vertical and horizontal planes?
The utricle and saccule.
What kind of equilibrium is associated with head movement detected by the utricle and saccule?
Gravitational equilibrium.
Answer 24 questions on Human Sensory Systems.
1. Which structures make up the central nervous system, as distinct from the peripheral nervous system?
2. A nerve carries sensory information from the skin toward the spinal cord. How is this nerve classified by the direction its signals travel?
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