Chapter 9 the senses Flashcards
What does the sensory pathway consist of?
Receptors, sensory neurons, sensory tracts and sensory areas
What do the receptors do?
detect changes (stimuli) and generate impulses
What do the sensory neurons do?
transmit impulses from receptors to the CNS
What do the sensory tracts do?
white matter in the spinal cord or brain that transmits impulses to a specific part of the brain
What are the sensory areas?
most of are in the cerebral cortex. they feel and interpret sensations
What is projection?
sensation seems to come from the area where the receptors where stimulated even though its the brain that truly feels the sensation
What is localization?
the ability to identify the part of the body receiving the sensation
learned in infancy
What is intensity?
the degree to which a sensation is felt
a strong stimulus affects more receptors, more impulses are sent to the brain and are interpreted as a more intense sensation
What is contrast?
the effect of a previous or simultaneous sensation on a current sensation as the brain compares them
What is adaptation?
becoming unaware of a continuing stimulus
if the stimulus remains constant, there is no change for receptors to detect
What is after-image?
the sensation remains in the consiousness after the stimulus has stopped; often true for sensations of greater intensity
What is free-nerve endings?
receptors for heat, cold, itch, and pain
what is encapsulated nerve endings?
receptors for touch and pressure
Where are sensory areas located?
parietal lobes; largest areas are in the hands and face
What is neuropathy?
damage to nerves that impairs sensation
What is referred pain?
visceral pain that is felt as cutaneous pain
common pathways in the CNS carry both cutaneous and visceral impulses
the brain usually projects sensation to the more frequent source of impulses
What do stretch receptors in muscles do?
they detect stretching which enable the brain to create a mental picture of the muscles
Where are the sensory areas for conscious muscle located?
parietal lobes
Why does the cerebellum use unconscious muscle sense?
to coordinate voluntary movement
What are chemoreceptors for taste?
are in tastebuds on the tongue
detect chemicals in solution in the mouth
touch receptors detect textures
What are the 5 basic tastes?
sweet, sour, salty, bitter, and savory;
foods stimulate combination of receptors
pain receptors for “hot food”
where are the impulses from the taste buds transmitted?
by the facial and glossopharyngeal nerves to the taste areas in the parietal-temporal cortex
some adaptation does occur
what are chemoreceptors for smell?
olfactory receptors in upper nasal cavities, detect vaporized chemicals
how are olfactory receptors transmitted?
olfactory nerves through the ethmoid bone to the olfactory bulbs to olfactory areas in the temporal lobes
Are taste and smell intertwined?
yes
Hunger and thirst may be called what?
visceral sensations
Receptors for hunger?
in hypothalamus, detect changes in GI hormones and nutrient levels in the blood
hunger is projected to the stomach
adaption does occur at first
Receptors for thirst?
in hypothalamus, osmoreceptors detect changes in body water;
thirst is projected to the mouth and pharynx
adaptation does not occur
What do the eyelashes and eyelids do?
spread tears and keep dust out of eyes
what is the conjunctivae?
lines the eyelids and cover the white eye
What is conjunctivitis?
inflammation of conjunctivae
may be caused by allergies or by certain baceria
what are tears produced by?
lacrimal glands, which flows across the eyeball to two lacrimal ducts, to lacrimal sac, to nasolacrimal duct to nasal activity
What do tears do?
wash the anterior eyeball and contains lysozome to inhibit bacterial growth
What is the eyeball protected by?
the bony orbit (socket)
What do the six extrinsic muscles do?
four rectus and two oblique
move the eyeball up, down, and side to side
nerves are the 3rd, 4th, and 6th cranial nerves
What is the schlera?
outermost layer of the eyeball, made of fibrous connective tissue; anterior portion is the transparent cornea, the first light refracting structure
What is the choroid layer?
middle layer of eyeball; dark blue pigment absorbs light to prevent glare within the eyeball
what is the ciliary body?
a circular smooth muscle that surrounds the edge of the lens and is connected to the lens by suspensory ligaments
ciliary body and suspensory ligaments
change shape of lens, which is made of a transparent elastic protein and which refracts light
what is the lens?
transparent and elastic protein disc behind the iris; refracts the light rays and is adjustable for different distances
what is the iris?
two sets of smooth muscle fibers regulate diameter of pupil, that is, how much light strikes the retina
radial fibers-dilate pupils (sympathetic)
circular fibers-constrict pupils (parasympathetic)
What is the retina?
innermost layer of eyeball; contains rods and cones
what do the rods and cones do?
rods- detect light; abundant toward periphery of retina
cones- detect color; abundant in center of retina
What is the fovea?
in the center of the macula lutea; contains only cones; area of best color vision
What is the optic disc?
no rods or cones; optic nerve passes through eyeball
what are the two cavities within the eyes?
posterior cavity and anterior cavity
What is the posterior cavity?
found between lens and retina and contains vitreous humor that keeps the retina in place
what is the anterior cavity?
found between cornea and lens and contains aqueous humor that nourishes the lens and cornea;
made by capillaries of the ciliary body, flows through pupil, is reabsorbed to blood at the canal of Schlemm
what is refraction of light rays?
the deflection or bending of a ray of light as it passes through one object and into another object greater or lesser density
takes place within the cornea, aqueous humor, lens and vitreous humor
what is the only adjustable part of the refraction system?
the lens
ciliary muscles relaxes for distant vision, and lens is thin
ciliary muscle contracts for near vision, and elastic lens thickens and has greater refractive power
what happens when light strikes retina?
stimulates chemical reactions in the rods and cones
In rods, which chemical breaks down to form scotopsin and retinal?
rhodopsin
In cones, specific wavelengths of light are absorbed which are?
red- absorbing, blue-absorbing, and green absorbing cones
what are ganglion neurons?
receive impulses generated by the rods and cones
their axons form the optic nerve
what are optic nerves?
the 2nd cranial nerves, each extends posteriorly from the retina to the optic chiasma
What is the optic chiasma?
site of the crossover of medial fibers of both optic nerves, permitting binocular vision
optic tracts
nerve pathways from the optic chiasma to the brain; branches take impulses to the mid-brain for visual reflexes
convergence at the thalamus for integration and dispersal
continuations to the occipital lobes for seeing and interpretation
Where are the visual areas?
the areas in the occiptal lobes where impulses from the retina are “seen” and interpreted
what does the outer ear consist of?
auricle and the ear canal
what is the auricle or pinna?
the external ear, made of cartilage covered with skin
has no function for people
what is the external auditory meatus?
the ear canal, a tunnel into the temporal bone that ends at the eardrum
what is the tympanic membrane?
the eardrum, the first structure to vibrate when sound waves enter the ear canal
what is the malleus, incus, and stapes?
the bones of the middle ear cavity (filled with air) which transmit vibrations from the eardrum to the oval window and the cochlea of the inner ear
what is the eustachian tube?
extends from the middle ear cavity to the nasopharynx; permits air to enter or leave to equalize the pressure and allow the eardrum to vibrate properly
what is the bony and membranous labryinths ?
the inner ear cavities in the temporal bone, filled with fluid, the vestibule contains the utricle and saccule; adjacent are three semiculuar canals
what is the chochlea?
shaped like a snail shell, receives vibrations from the stapes at the oval window; vibrations continue to the round window, which bulges to equalize the pressure, contains the spiral organ of corti
what is the utricle and saccule?
membranous sacs that contain otoliths (CaCo crystals) that are pulled by gravity and bend hair cells when the head tilits; impulses from the hair cells are carried by the 8th cranial nerve
What is the semicircular canals?
three membrane loops, each containing a tuft of hair cells (crista) that are bent by movement of the head or body as a whole; impulses from the hair cells are carried by the 8th cranial nerve
VII (8th) cranial nerve (auditory or vestibulocochlear)
tranmits impulses from all of the inner ear receptors to the brain; temporal lobes for hearing; cerebellum, midbrain, and cerebrum for equilibrium
what is the aortic arch?
receives blood pumped by the left ventricle of the heart, curves over the top of the heart
what are the left and right carotid arteries?
branches of the aortic arch that take blood through the neck on the way to the brain
what do the pressoreceptors in the carotid sinuses and aortic sinuses?
detect changes in blood pressure
what do the chemoreceptors in the carotid bodies and the aortic body do?
detect changes in the oxygen and carbon dioxide content and the ph of blood
