Chapter 14: The Somatic Nervous System

Opsin pigments

are actually transmembrane proteins that contain a cofactor known as retinal.

Sensory receptors

are specialized cells that detect changes in the environment and convert them into electrical signals that can be interpreted by the brain.

anterior corticospinal tract

The is responsible for controlling the muscles of the body trunk.

Tears

are produced by the lacrimal gland, located beneath the lateral edges of the nose.

Movement

of the eye within the orbit is accomplished by the contraction of six extraocular muscles that originate from the bones of the orbit and insert into the surface of the eyeball.

Vision

is the special sense of sight that is based on the transduction of light stimuli received through the eyes.

Chemical stimuli

can be interpreted by a chemoreceptor that interprets , such as an objects taste or smell.

Osmoreceptors

respond to solute concentrations of body fluids.

Visual acuity

, or the sharpness of vision, is greatest at the fovea.

internal organs

An interoceptor is one that interprets stimuli from and tissues, such as the receptors that sense the increase in blood pressure in the aorta or carotid sinus.

ciliary body

Overlaying the , and visible in the anterior eye, is the iris- the colored part of the eye.

proprioceptor

Finally, a(n) is a receptor located near a moving part of the body, such as a muscle, that interprets the positions of the tissues as they move.

Somatosensation

(Touch) is the sense of touch, pressure, temperature, and pain that is detected by the skin and other body parts.

photosensitive pigment

The rod- shaped outer segments of the rod photoreceptor contain a stack of membrane- bound discs that contain the rhodopsin.

Alkaloids

are nitrogen- containing molecules that often have a basic pH.

tympanic membrane

At the end of the auditory canal is the , or ear drum, which vibrates after it is struck by sound waves.

choroid

The is a layer of highly vascularized connective tissue that provides a blood supply to the eyeball.

posterior cavity

The is filled with a more viscous fluid called the vitreous humor.

ossicles

The three are the malleus, incus, and stapes, which are Latin names that roughly translate to hammer, anvil, and stirrup.

anterior cavity

The is the space between the cornea and lens, including the iris and ciliary body.

inner ear

Along with audition, the is responsible for encoding information about equilibrium, the sense of balance.

papillae

Raised bumps called (singular= ) contain the structures for gustatory transduction.

Physical stimuli

, such as pressure and vibration, as well as the sensation of sound and body position (balance), are interpreted through a mechanoreceptor.

lateral corticospinal tract

The is composed of the fibers that cross the midline at the pyramidal decussation.

Photoreceptor cells

have two parts, the inner segment and the outer segment segment.

Sound

is transduced into neural signals within the cochlear region of the inner ear, which contains the sensory neurons of the spiral ganglia.

cochlea

The is attached to the stapes through the oval window.

sensory pathway

The for gustation travels along the facial and glossopharyngeal cranial nerves, which synapse with neurons of the solitary nucleus in the brain stem.

auricle

The , ear canal, and tympanic membrane are often referred to as the external ear.

cervical enlargement

The is particularly large because there is greater control over the fine musculature of the upper limbs, particularly of the fingers.

inner surface of each lid

The is a thin membrane known as the palpebral conjunctiva.

general sense

The of touch, which is known as somatosensation, can be separated into light pressure, deep pressure, vibration, itch, pain, temperature, or hair movement.

transduction of sound

Hearing, or audition, is the waves into a neural signal that is made possible by the structures of the ear.

similar intense stimuli

Additionally, pain is primarily a chemical sense that interprets the presence of chemicals from tissue damage, or , through a nociceptor.

oval window

The is located at the beginning of a fluid- filled tube within the cochlea called the scala vestibuli.

dorsal column

The is separated into two component tracts, the fasciculus gracilis that contains axons from the legs and lower body, and the fasciculus cuneatus that contains axons from the upper body and arms.

cone

The - shaped outer segments of the photoreceptor contain their photosensitive pigments in infoldings of the cell membrane.There are three photopigments, called opsins, which are each sensitive to a particular wavelength of light.

lumbar enlargement

The is not as significant in appearance because there is less fine motor control of the lower limbs.

vestibulospinal tract

The connects the brain stem nuclei of the vestibular system with the spinal cord.

Head position

is sensed by the utricle and saccule, whereas head movement is sensed by the semicircular canals.

reticulospinal tract

The connects the reticular system, a diffuse region of gray matter in the brain stem, with the spinal cord.

scala tympani

The ends at the round window, which is covered by a membrane that contains the fluid within the scala.

receptor

An exteroceptor is a(n) that is located near a stimulus in the external environment, such as the somatosensory that are located in the skin.

olfactory receptor neurons

The are located in a small region within the superior nasal cavity.

dorsal column system

The (sometimes referred to as the dorsal column- medial lemniscus) and the spinothalamic tract are two major pathways that bring sensory information to the brain.