EAP Ch. 9 The Senses

Question 1

Describe the sensory pathway (4 parts)

Answer 1

1. Receptors change the energy of a stimulus to the electrical energy of a nerve impulse
2. Sensory neurons found in the spinal/cranial nerves transmits impulses to the central nervous system
3. Sensory tracts are white matter that carry impulses to specific parts of the brain
4. Sensory areas in the brain (mostly cerebral cortex) feel and interpret sensations

Question 2

Senses

Describe: Projection, Intensity, Contrast, and Adaptation

Answer 2

1. Projection - makes it seems like a sensation is coming from where the receptors were stimulated (ex: phantom pains or tinnitus - your brain projects sensations to where receptors used to be)
2. Intensity - the more impulses the more intense the sensation
3. Contrast - new sensations are compared relatively to old ones (ex: a pool feels colder when you’re hot)
4. Adaptation - get used to continuous stimulus (ex: white noise)

Question 3

Senses

Describe the following: Types of cutaneous senses; Neuropathy; 3 types of itching; Where the sensory areas for the skin are

Answer 3

• Cutaneous = Skin: heat, cold, itch, pain (free nerve endings) + touch, pressure (encapsulated nerve endings)
• Neuropathy damage to the nerves that impairs sensations (can be caused by diabetes)
• Chemical itching takes place in the skin (ex: poison ivy) versus mechanical itching (ex: scratchy fabric) versus pathological itching (symptom of some diseases)
• Sensory areas for the skin are in the parietal orbs. Most receptors are in the face and hands (meaning they feel the most sensations).

Question 4

Describe referred pain and visceral pain

Answer 4

Free nerve endings are also found in internal organs- called visceral pain. Can result in referred pain where the pain is felt through the skin.

Question 5

Describe muscle sense

Answer 5

Stretch receptors > muscle sense. Consciously felt by parietal lobes and unconsciously used by cerebellum to coordinate involuntary movements (i.e., muscle memory)

Question 6

Describe sense of taste

Answer 6

Taste buds have chemoreceptors that detect chemicals (food) and solution (saliva). Also have receptors for pain, heat (spiciness), and touch (texture of foods)

Question 7

Describe sense of smell

Answer 7

Chemoreceptors that detect vaporized chemicals. Olfactory receptors generate impulses carried by the olfactory nerves through the ethmoid bone to the olfactory bulbs. The pathway of these impulses ends in the olfactory areas of the temporal lobes.

Question 8

Describe hunger and thirst

Answer 8

These are visceral sensations that are projected. If you don’t eat eventually you’ll adapt (to a certain point) but thirst never adapts.

Question 9

Parts of the eye

Describe: Eyelashes and eyelids

Answer 9

Keep dust out of the eye; lids sweep tears across the anterior surface of the eyeball

Question 10

Parts of the eye

Describe: Lacrimal glands

Answer 10

Produce tears, which wash the eye and contain lysozyme to inhibit growth of bacteria. Drain into nasal cavity, which is why crying give you a runny nose.

Question 11

Parts of the eye

Describe: Extrinsic muscles

Answer 11

Connect to the eyeball to move it around

Question 12

Parts of the eye

Describe: Sclera

Answer 12

The white of the eye

Question 13

Parts of the eye

Describe: Cornea

Answer 13

The outermost layer of the eye (front of the sclera) that covers the iris

Question 14

Parts of the eye

Describe: Conjunctiva

Answer 14

The underside of the eyelid (i.e. conjunctivitis when it gets infected/inflamed)

Question 15

Parts of the eye

Describe: Choroid layer

Answer 15

Between the sclera and retina - has dark pigment

Question 16

Parts of the eye

Describe: Iris

Answer 16

The colored part of the eye. Has muscles that connect to the pupil to make it contract and constrict to change how much light enters the eye

Question 17

Parts of the eye

Describe: Ciliary body (muscle)

Answer 17

Connects to the lens to make it contract and constrict which changes focus

Question 18

Parts of the eye

Describe: Lens

Answer 18

Disc behind the iris/pupil that refracts light. Cataracts are when proteins in the lens break down due to UV light or smoking, causing cloudiness.

Question 19

Parts of the eye

Describe: Aqueous humour

Answer 19

Tissue fluid at the front of the eye that nourishes the lens and cornea, which don’t have their own capillaries. If pressure is too great, fluid can’t drain and you get glaucoma.

Question 20

Parts of the eye

Describe: Canal of Schlemm

Answer 20

Small veins at the edge of the iris where aqueous humor fluid is absorbed back into the blood

Question 21

Parts of the eye

Describe: Vitreous humor

Answer 21

The main big sac of fluid in the eye, which keeps the retina in place through pressure (if it drains, loses pressure, get detached retina)

Question 22

Parts of the Retina and Optic Pathway

Describe the following: Retina, Optic disc, Rods, Cones, Macula lutea, and Ganglion neurons

Answer 22

• Retina - Inner layer of the eyeball (sclera is outer layer and choroid is middle layer) where rods and cones are located
• Optic disc - the opening where the optic nerve enters/leaves the eyeball - has no cones or rods (blind spot)
• Rods - photoreceptors detect presence of light (periphery of retina)
• Cones - photoreceptors detect color (red/blue/green) (center of retina)
• Macula lutea - area of retina right behind lens. Contains smaller area called fovea centralis which is the best area for seeing color. Where macular degeneration occurs (loss of central vision)
• Ganglion neurons - receive impulses from rods and cones and form into optic nerve

Question 23

Parts of the Retina and Optic Pathway

Describe the following: Optic chiasma, Optic tracts, Visual areas

Answer 23

• Optic chiasma - where the optic nerves cross in front of the pituitary gland (how binocular vision works)
• Optic tracts - path of optic nerves that branch off to midbrain and thalamus and on to occipital lobes
• Visual areas - area of occipital lobes in brain where impulses are seen and interpreted

Question 24

Physiology of vision

Describe: refraction

Answer 24

Refraction: deflection or bending of a ray of light. Steps: cornea > aqueous humor > lens > vitreous humor (only the lens can adjust).

Question 25

Physiology of vision

Describe the following: Myopia, Hyperopia, Presbyopia, Astigmatism, Night blindness, Color blindness, and Strabisumus

Answer 25

• Nearsightedness (myopia) when you can’t see far away vs farsightedness (hyperopia) when you can’t see near. Presbyopia is when you become farsighted over time due to age. Astigmatism is an irregular curvature in the cornea or lens that scatters light.
• Night blindness is caused by a deficiency in Vitamin A, which is necessary for the synthesis of rhodopsin in the rods. Color blindness is when one of the three sets of cones (red/blue/green) don’t work.
• Strabismus (lazy eye) cannot direct at one point (convergence isn’t possible) and brain just won’t use images from lazy eye and overtime will go blind (amblyopia)

Question 26

The Parts of the Ear

Describe the following: Auricle, External auditory meatus

Answer 26

• Auricle (outer ear) - external ear
• External auditory meatus (outer ear) - the ear canal, a tunnel into the temporal bone that ends at the eardrum

Question 27

The Parts of the Ear

Describe the following: Tympanic membrane, Malleus/Incus/Stapes, and Eustachian tubs

Answer 27

• Tympanic membrane (middle ear) - the eardrum, the first structure to vibrate when sound waves enter the ear canal
• Malleus, incus, and stapes (middle ear) - 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
• Eustachian tube (middle ear) - 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. When infected = otitis media (especially in children)

Question 28

The Parts of the Ear

Describe the following: Bony and membranous labyrinths, Cochlea, Organ of Corti, Urticle/Saccule, Semicircular canals

Answer 28

• Bony and membranous labyrinths (inner ear) - the inner ear cavities in the temporal bones, filled with fluid; the vestibule contains the utricle and saccule; adjacent are the three semicircular canals
• Cochlea (inner ear) - 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
• Organ of Corti (in cochlea) - Contains the hair cells that bend with the vibrations (from sound waves) in the fluid of cochlea and generate impulses to the 8th cranial nerve
• Utricle and saccule (inner ear) - Membranous sacs that contain otoliths (calcium carbonate crystals) that are pulled by gravity and bend hair cells when the head tilts; impulses from the hair cells are carried by the 8th cranial nerve position of body at rest
• Semicircular canals (inner ear) - Three membranous 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 position of body in motion

Question 29

The Parts of the Ear

Describe: 8th cranial nerve

Answer 29

8th cranial nerve (auditory or vestibulocochlear) - Transmits impulses from all of the inner ear receptors to the brain: temporal lobes for hearing; cerebellum, midbrain, and cerebrum for equilibrium

Question 30

Describe 3 types of deafness

Answer 30

• Conduction deafness - impairment of on the of the structures that transmits vibrations (more temporary)
• Nerve deafness - affects the cochlea (more age based)
• Central deafness - damage to the auditory areas of the temporal lobes (brain)