Physio Labs Flashcards
the ability to determine fine detail and distinguish one object from another
Visual acuity
Snellen test
E charts
several rows of letters
only the letter E in different positions
some letters
disappear while you are looking at other letters. You may have
visual field problem
Having 20/20 vision means that
your visual acuity at 20 feet away from an object is normal
Refractive errors, such as nearsightedness or farsightedness, occur when light rays entering the eye can’t focus exactly
on the nerve layer (retina
refraction
When light passes from one substance to another of different density its speed changes and the rays are bent.
The bending power of the cornea and vitreous humor are
constant
but the lens’s refractive strength varies when it
Changes shape
In general, light from a distant source (over 20 feet) approaches the eyes as parallel rays so
change in lens shape is necessary for it to focus properly on the retina.
Retina needs to be flat
The lens is flat because the ciliary muscle is ….. and the tension of the suspensory ligament attached to the lens is ……, so light refraction is …..
relaxed
increased
decreased
The ability of the eye to focus for close objects (less than 20 feet) is called
accommodation
To focus on near objects, the lens becomes … because the ciliary muscle ….. and the tension of the suspensory ligament is ….., so light refraction is ….
round
contracts
decreased
increased
The elasticity of the lens decreases dramatically with age, resulting in difficulty in focusing for near or close vision. This is called
presbyopia
Lens elasticity can be tested by measuring the
near point accommodation
In young adults, the near point of accommodation is about
10 cm from the eye.
Closer in children and further in old people
The eye that focuses images correctly on the retina is said to have
emmetropia.
the image focuses in front of the retina
myopia
the image focuses behind the retina
hyperopia
Irregularities in the curvature of the lens and/or the cornea lead to a blurred vision problem called
astigmatism
In astigmatism blurry images occur because
points of light are focused on the retina as lines rather than individual points
The intrinsic muscles,
controlled by the autonomic nervous system, are
ciliary body
Iris
ciliary body function
which changes the shape of the lens
Iris function
which controls the pupil size and regulates the amount of light rays entering the eye
The extrinsic muscles, controlled by the somatic nervous system, are
the rectus and oblique muscles,
the rectus and oblique muscles, functions
control eyeball movement and make it possible to keep moving objects focused on the fovea centralis (for central vision)
convergence, or medial eye movement, which is essential to keep both eyes aimed at a close object for near vision.
Pupils that dilate in response to bright light, or are sluggish to close, are abnormal and may indicate
a neurological disorder (such as autism, Alzheimer’s disease, etc.), or it may indicate drunkenness
Accomodation reflex involve
triad of changes when a person looks at a nearby object
accommodation reflex is
mediated by
both of the intrinsic eye muscles. The lens becomes rounder so that the divergent light rays will be refracted to focus on the fovea centralis during near vision, and the iris constricts to reduce divergent light rays from entering the eye for a sharper image. The convergence reflex is mediated by the extrinsic eye muscles. Medial movement of the eyeball keeps the pupil aligned with the object as it moves closer.
Pathway of accommodation
- Afferent impulses from retina pass along the normal visual pathway to reach the visual areas in the occipital lobe 2. From the visual areas fibers descend to the oculomotor (3rd cranial nerve) nucleus of both side in the midbrain.
- Efferent fibers pass along the 3 rd cranial nerve to the eye to supply the following muscles:
Medial rectus muscle
Constrictor pupillae muscle
Ciliaris muscle
In accommodation reflex the fibers reach the lateral geniculate body and the occipital cortex but they donot pass through
the pretectal nucleus situated in midbrain.
Direct pupillary reflex checks health of
Optic and occulomotor nerve of the same eye
InDirect pupillary reflex checks health of
Occulomotor nerve of the same eye and optic nerve of the other eye.
The basis of distinguishing colors is based on the presence of
3 separate photopigments sensitive to different wavelengths of light in different cones.
3 separate photopigments are most sensitive to
Blue
Green
Red
Respectively
The perception of colors of different hues is mediated by
varying degrees of excitation of cones bearing different photopigments.
The blue sensitive photopigment is encoded in the …. chromosome of the human genome, and the green and red sensitive photopigment is encoded in the genes on …… Color blindness is mostly a …. disorder
7th
the X chromosome
genetic
Protanopia
red color blindness,
Deuteranopia
green color blindness
tritanopia
blue color blindness.
the Ishihara test,
Color blind test
reflex is made possible by
neural pathways called reflex arcs which can act on an impulse before that impulse reaches the brain.
automatic response to a stimulus that does not receive or need
conscious thought.
Reflex
the operation of reflexes.
- Receptor detects the internal or external change.
- Sensory neuron transmits nerve impulses from the receptor into the brain or spinal cord.
- Interneuron serves as processing center, conducts nerve impulses from the sensory neuron to a motor neuron.
- Motor neuron: conducts motor output fron the brain or spinal cord to the periphery.
- Effecter can be a muscle or gland. It responses to stimulation by the motor neuron and produces the reflex or behavioral action.
Wires attached to head by salty base that conducts electricity
Electrodes
Wave amplitude is measured by… and indicates….
Microvolts
How much electricity is going beneath the electrodes
EEG paterns are due to
Postsynaptic Graded potential
A high amplitude (يعني من فوق لتحت) indicates
Many neurons activated
Synchronous
A low amplitude
Neurons are less activated
Asynchronous
Amplitude range
0.5-100 microvolt
Wave frequency indicates and is measured by
Hertz
How often the wave cycles from max to min amplitude
Range of frequency
1-40 hz
Low frequency indicates while high frequency indicates
Less responsive states
High alerts
Distinct levels of frequency
Beta (14-30) Hz
Alpha (8-13) Hz
Theta (4-7) Hz
Delta (lower than 3.5)
Patterns are abnormal over
Diseased or damaged areas
A shift from a low amplitude to a high one means
Epileptic seizure
High amplitude in epilepsy reaches
1000 mv
Epilepsy can cause
Seizure
Loss of consciousness
Changes in behaviour
2 ways of transmission of sound waves
Air (ossicle)
Bone construction
A normal ear hears better in
2X better in ossicle ratger tham bone
Our own voice is transferred via
Both air and bone
Steps of air transmission
Waves in air vibrate fluid in cochlea which moves trympanic memebrane, middle ear ossicle and oval window
In normal hearing weber is
R rinne
L rinne
Centralized in middle
+
+
If right ear is conducive hearing loss then
Weber: right centralized
Right Rinne : negative
Left rinne: positive
If a right ear has sensory neural loss then
Weber: left centralized
Right rinne: pathological positive
Left rinne: positive
an involuntary and nearly instantaneous movement in response to a stimulus
Reflex
neural pathways which can act on an impulse before that impulse reaches the brain.
called reflex arcs
Lesions that damage the sensory or motor limb of a reflex arc will
diminish that reflex.
the net result of lesions that damage the descending tracts is facilitation of reflexes that are mediated
at only the level of the spinal cord
After acute lesions, spinal reflexes often pass through an initial stage of hypoactivity. This stage has been called
spinal shock” or diaschisis
When reflexes return after spinal transection, they become
extremely hyperactive.
a simple reflex, with the receptor neuron having direct connections to the muscle spindle apparatus in the muscle and with the alpha motor neurons in the central nervous system that send axons back to that muscle
myotatic) reflex i
the ability to discern between two points touching the skin.
Two-point discrimination
Two factors determine two-point discrimination:
density of sensory receptors, and size of neuronal receptive fields.
Fingertips have….. more density of sensory receptors than the hand.
3-4 times
specific sensory space that if simulated will result in the activation of that particular neurone.
receptive field of that neurone.
areas with the most sensitive two-point discrimination should have
high density of receptors with small receptive fields.
