EAP Ch. 9 The Senses Flashcards
Describe the sensory pathway (4 parts)
- Receptors change the energy of a stimulus to the electrical energy of a nerve impulse
- Sensory neurons found in the spinal/cranial nerves transmits impulses to the central nervous system
- Sensory tracts are white matter that carry impulses to specific parts of the brain
- Sensory areas in the brain (mostly cerebral cortex) feel and interpret sensations
Senses
Describe: Projection, Intensity, Contrast, and Adaptation
- 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)
- Intensity - the more impulses the more intense the sensation
- Contrast - new sensations are compared relatively to old ones (ex: a pool feels colder when you’re hot)
- Adaptation - get used to continuous stimulus (ex: white noise)
Senses
Describe the following: Types of cutaneous senses; Neuropathy; 3 types of itching; Where the sensory areas for the skin are
- 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).
Describe referred pain and visceral pain
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.
Describe muscle sense
Stretch receptors > muscle sense. Consciously felt by parietal lobes and unconsciously used by cerebellum to coordinate involuntary movements (i.e., muscle memory)
Describe sense of taste
Taste buds have chemoreceptors that detect chemicals (food) and solution (saliva). Also have receptors for pain, heat (spiciness), and touch (texture of foods)
Describe sense of smell
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.
Describe hunger and thirst
These are visceral sensations that are projected. If you don’t eat eventually you’ll adapt (to a certain point) but thirst never adapts.
Parts of the eye
Describe: Eyelashes and eyelids
Keep dust out of the eye; lids sweep tears across the anterior surface of the eyeball
Parts of the eye
Describe: Lacrimal glands
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.
Parts of the eye
Describe: Extrinsic muscles
Connect to the eyeball to move it around
Parts of the eye
Describe: Sclera
The white of the eye
Parts of the eye
Describe: Cornea
The outermost layer of the eye (front of the sclera) that covers the iris
Parts of the eye
Describe: Conjunctiva
The underside of the eyelid (i.e. conjunctivitis when it gets infected/inflamed)
Parts of the eye
Describe: Choroid layer
Between the sclera and retina - has dark pigment
Parts of the eye
Describe: Iris
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
Parts of the eye
Describe: Ciliary body (muscle)
Connects to the lens to make it contract and constrict which changes focus
Parts of the eye
Describe: Lens
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.
Parts of the eye
Describe: Aqueous humour
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.
Parts of the eye
Describe: Canal of Schlemm
Small veins at the edge of the iris where aqueous humor fluid is absorbed back into the blood
Parts of the eye
Describe: Vitreous humor
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)
Parts of the Retina and Optic Pathway
Describe the following: Retina, Optic disc, Rods, Cones, Macula lutea, and Ganglion neurons
- 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
Parts of the Retina and Optic Pathway
Describe the following: Optic chiasma, Optic tracts, Visual areas
- 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
Physiology of vision
Describe: refraction
Refraction: deflection or bending of a ray of light. Steps: cornea > aqueous humor > lens > vitreous humor (only the lens can adjust).
Physiology of vision
Describe the following: Myopia, Hyperopia, Presbyopia, Astigmatism, Night blindness, Color blindness, and Strabisumus
- 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)
The Parts of the Ear
Describe the following: Auricle, External auditory meatus
- Auricle (outer ear) - external ear
- External auditory meatus (outer ear) - the ear canal, a tunnel into the temporal bone that ends at the eardrum
The Parts of the Ear
Describe the following: Tympanic membrane, Malleus/Incus/Stapes, and Eustachian tubs
- 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)
The Parts of the Ear
Describe the following: Bony and membranous labyrinths, Cochlea, Organ of Corti, Urticle/Saccule, Semicircular canals
- 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
The Parts of the Ear
Describe: 8th cranial nerve
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
Describe 3 types of deafness
- 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)
