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Physiology of Aging - Lecture 9
Terms in this set (70)
Treatment for Parkinson's Disease
there is no cure for it and no proven preventative measures. Treatments are therefore aimed at alleviating the symptoms
types of treatment for Parkinson's
(1) Drug Treatment
(2) Surgical Treatment
(3) Experimental Strategies
is aimed at increasing dopamine levels. Different drugs that are given include:
(2) Cholinergic inhibitors
(3) other drugs, including Dopamine agonists, MAO and COMT inhibitors, and Amantidine
crosses the blood brain barrier and is a precursor of dopamine that is converted to dopamine by dopa decarboxylase
effects of L-dopa:
(1) decreases some of the most disturbing symptoms of Parkinson's
(2) its side effects can be motor complications (dyskinesias), periods of freezing, tremor, rigidity, and gastrointestinal problems
(3) it loses its effectiveness in 3-5 years
(4) can be neurotoxic due to the generation of ROS, though vitamin E is often given to decrease ROS damage
involuntary writhing and twisting
these are sometimes given simultaneously to decrease the excitatory input of the substantia nigra, though they can impair memory
are drugs that activate dopamine receptors and therefore mimic dopamine's effects
MAO and COMT inhibitors
decrease the degradation of dopamine, which should increase dopamine concentration in the brain
increases dopamine release and decreases reuptake
Surgical treatment of Parkinson's
this has been used for many years with varying levels of success. Treatment includes removal of the ventromedial pallidus to prevent overstimulation of the substantia nigra and deep brain electrical stimulation to certain regions of the basal ganglia
why is deep brain electrical stiimulation done?
it is an attempt to increase the amount of dopaminergic neurons present there.
Experimental treatment strategies
include preventing cell death with nerve growth factor injection, implanting stem cells, or using antioxidants. So far there have been mixed results for all of these strategies
is a 24 hour, rhythm that governs many physiological functions. This rhythm includes hormone rhythms, body temperature, and sleep
purpose of sleep
it is unknown, but it is thought to provide recovery from the strains of the waking hours. REM is possibly psychologically restorative, and state 3 and 4 sleep may be physically restorative.
when does deep sleep occur?
stage 3 and 4 of sleep
Stages of sleep
awake, stage 1, stage 2, stage 3, stage 4, REM
REM (rapid eye movement)
this is the phase of sleep where dreaming occurs, and you become paralyzed. The amount of time spent in REM lengthens as the night progresses
changes in stages of sleep with aging
(1) REM and phase 3 &4 sleep shortens
(2) Phase 1 & 2 lengthen
(3) it takes longer to fall asleep
(4) nocturnal sleep is often interrupted, there are more disturbances/awakenings
(5) daytime naps are often added, and many complain of daytime sleepiness
(6) daytime sleepiness may be due to the loss in phase 3& 4 sleep.
(7) increase in occurrence of sleep apnea
(1) occurs during REM sleep
(2) causes a person to feel less rested
(3) is when one stops breathing while asleep
(4) is due to the collapse of the upper airways in the sleeping state (related snoring)
(5) results in decrease in blood oxygen, which causes arousal from sleep and restoration of activity in the upper airway muscles
how many respiratory disturbances do young adults have per night?
how many respiratory disturbances do the elderly (70s) have?
up to 50 per night. This could be the cause of much of their fragmented sleep
Cause of sleep apnea
its cause is unknown, but it is known that:
(1) it is most frequent during REM sleep
(2) is associated with increased sympathetic stimulation and norepinephrine release
(3) leads to cardiac arrhythmias and pulmonary hypertension common during apneic periods, which is a life-threatening condition
(4) common with mental disorders like depression, and also common with certain medications
(5) is associated with obesity
sleep can also be fragmented by:
uncontrollable leg movements while sleeping, like restless leg syndrome; this is associated with parkinson's disease
Causes of changing sleep patterns:
the causes is unknown, but:
(1) it may be related to changes in serotonin (type of neurotransmitter), which modulates effects of light on circadian rhythm. Serotonin is a precursor for melatonin, a sleep-inducing hormone
(2) it may be caused by changes in the reticular activating system, which is a part of the brain.
functions of the reticular activating system:
(1) controls alertness, behavior, and sensory input that modify sleep patterns
(2) alterations in this system may explain the decreased response time in the elderly
(3) is involved in reaction time
Basic structure of the eye includes the:
is responsible for most of the refraction of light waves, which helps to start focusing the light.
cornea with aging
the cornea increases in thickness and becomes less curved, leading to defective diffusion of light
focuses light rays into the retina.
proper lens function requires...
transparency, so that light can pass through effectively and be refracted. It also requires flexibility, because the lens must change shape to focus on objects at different distances. This process is called accommodation.
to accommodate focusing n a near object the lens...
must become more rounded and spherical
how does a lens focus on a more far object
the lens assumes a more flattened shape
accomodation is achieved by..
contraction/relaxation of the ciliary muscles. when the ciliary muscle is relaxed, the suspensory ligaments are pulled tight and the lens is flattened, the right shape for distance vision. When the ciliary muscle is contracted, suspensory ligaments relax and the lens becomes more round and spherical, the appropriate shape for near vision
a ring of smooth muscle around he lens
lens and aging
with aging, the lens loses transparency and flexibility, and the lens increases in thickness thoughout life, which decreases flexibility
composition of lens
lens is composed of cytoskeletal proteins, collagens, and alpha-, beta-, and gamma-crystallins. Lens is mostly acellular, and the crystallins give it transparency. Lens do not turnover, so damage to the proteins can accumulate over time and make the lens more dense, opaque, and yellowish
excessive damage can lead to...
cataracts, which are excessive opacity
what causes damage to crystallin proteins?
glycation, carboamination, and deamidation, which are alterations common with oxidative damage.
the inability to have near-vision focus; is very common with aging. It can be corrected by bifocals
cause of presbyopia
because of the loss of flexibility in the lens with aging, it becomes less able to accommodate to focus on near objects. lens' loss of flexibility is due to compaction of the collagen and crystallins in the lens.
point of near vision and aging
the "point of near vision" increases with aging. So, the minimum distance between the eyes and an object that is required to form a clear image increases with age:
(1) at age 10 it is 9 cm
(2) at age 20 it is 10 cm
(3) at age 45 it is 20 cm
(4) at age 60 it is 84 cm
because older adults cannot focus on nearby objects, bifocal lenses are needed by most adults over the age of 55 for reading or performing tasks near to the eyes (presbyopia).
a smooth muscular ring that forms the pupil. It controls the amount of light entering the eye. It wwill typically dilate in the dark to let in more light
iris in the elderly
the iris does not dilate as well (relatively constricted, compared to younger people) and can lead to night vision impairment.
a layer along the back of the eye that contains photoreceptor cells. Retina contains several types of cells. its function is to detect light and color, and transduce this into an image in the brain. Contains a blind spot and the macula
cells that respond to light and transduce the signal
types of cells in theretina:
(3) horizontal cells
(4) bipolar cells
(5) amacrine cells
(6) ganglion cells
detect shades of gray
cells that detect color. When stimulated, they send signals to horizontal cells, bipolar cells, amacrine, cells and ganglion cells, and these all converge at the optic nerve, which travels to the visual cortex of the brain
this is where the optic nerve attaches to the back of the retina
changes in the retina with aging:
(1) rod cells are lost beginning in the 30s or 40s, and may be related to accumulated light damage
(2) about 3% of cone cells are lost per decade. There is a decrease in density of the conce cells, but remaining cells increase in size. This could be a major factor in the loss of visual acuity with age
(3) about 30% of bipolar, amacrine, and horizontal cells are lost
(4) about 50% of ganglion cells are lost
(5) there is an increase in Mueller cells, which are a type of glial (immune) cell
Functional Changes in vision with aging:
(1) increase in visual threshold
(2) decrease in visual acuity
(3) decreased color perception
increase in visual threshold with aging
the elderly need more light to see an object, due to the smaller pupil and decreased in number of rod cells
the ability to discern detail and contours of an object
decrease in visual acuity with aging may be due to:
(1) altered refraction of light by cornea and lens
(2) decreased accommodation
(3) decreased light input, due to a smaller pupil
(4) decreased density, number, and function of photoreceptor and retinal cells
(5) changes in central neural structures of the visual system (example: cell loss and/or dysfunction of visual cortex neurons)
what can enhance visual acuity in the elderly?
improved illumination and decreased glare
Decreased color Perception with aging (doesn't occur in all colors)
this decrease starts in the 40s, and men have a greater decline than woman. Short wave-length light detection (blue and yellow) declines first, due to yellowing of the lens (lost opaqueness). After age 60, loss of green detection occurs and is due to central and retinal factors, because it persists even when the lens is removed, so if we replace the lens the ability to detect green is not restored
Effects of Visual Impairments of the Edlerly
they can affect everyday tasks like driving and reading, which contributes to an increase in dependency and disability in the elderly.
Eye disease of the aged
(3) senile macular degeneration
46% of those 75-85 years have cataracts, 28% have macular degeneration, and 7.2% have glaucoma
(1) excessive accumulation of pigment and protein changes in the lens
(2) lens becomes opaque and cloudy and can cause functional blindness
(3) occurs more frequently in diabetics and females
(4) may be related to a decrease in dietary antioxidants, and there may also be decreased production of the antioxidant glutathione in the lens
(5) causes functional blindness
treatment of cataracts
involves surgical removal of the damaged lens, replacement with a plastic implant, and use of corrective glasses/contacts
(1) an increase in in pressure inside of the eyeball (intraocular pressure), which puts pressure on the side of the optic nerve and can lead to ischemic damage of the optic nerve
(2) is sometimes corrrelated with hypertension (high blood pressure)
(3) changes the shape of the eye (makes it more round)
(4) gives tunnel vision
(5) its cause is unknown
treatment for glaucoma
treated with eye drops that contain agents (hypotensive agents) that reduce pressure in the eye. It can also be treated with laser surgery as a way to reduce pressure in the eye
Senile Macular degeneration
involves degeneration in the macular region of the retina, especially the fovea; can have wet and dry conditions
macular region of retina
has a high density of cones, is involved in day and color vision, and is an area of high visual acuity
who is affected by senile macular degeneration?
(1) typically occurs in both eyes
(2) more common in women
(3) increases in incidence with age
(4) affected by environment, i.e. its incidence is increased with cigarette smoking
(5) is probably hereditary, so it is not just simple aging of retinal cells
(6) it accounts for 50% of thecases of legal blindness
characteristics of senile macular degeneration:
(1) abnormal deposits (Drusen-nodules) on sub-retinal membrane --> dry condition
(2) atrophy of retinal pigment epithelium (RPE); it deteriorates
(3) detachment of RPE
(4) subretinal neovasularization (new blood vessel growth that is abnormal --> wet condition), causes hemorrhaging in the eye
(5) retinal scarring
Treatment of senile macular degeneration
there is no prevention or cure, though antioxidants may be protective. Evidence, however, is not conclusive. Since there are no god treatments, the goal of treatment is to merely prevent retinal detachment and hemorrhage, typically by laser destruction of abnormal new blood vessels.
drugs as treatment of senile macular degeneration
can decrease angiogenesis with drugs, injected into the eye, that inhibit angiogenesis.
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