Question 1
Question
Match the developmental stages of the eye to their functionality:
Rudimentary: small patch of photosensitive cells; [blank_start]only for presence of light[blank_end]
[blank_start]Invagination of patch[blank_end]: limited directional sensitivity
Pinhole Eye: forces light to fall on a very small area; [blank_start]direction and imaging[blank_end]
Fluid-Filled: introduced [blank_start]diffraction and lens to refine travel[blank_end]
Modern Eye: another fluid filled chamber, [blank_start]separate cornea and iris[blank_end]
Question 2
Question
Which gene, related to the eyes, seems to be conserved amongst species?
Question 3
Question
Label the Compound Eye.
Answer
-
Cornea
-
The Ommatidium
-
Psuedocone
-
Support Cells
-
Retinular Cells
-
Rhabdomeres
Question 4
Question
Match the components of the compound eye with its purpose:
Cornea: [blank_start]focuses light into central aspect[blank_end]
[blank_start]Ommatidium[blank_end]: the single visual transduction unit that makes up the compound eye
[blank_start]Support Cells[blank_end]: continue to focus light into the central portion of the cell
Retinular Cells: [blank_start]transfer information to the rhabdomeres[blank_end]
[blank_start]Rhabdomeres[blank_end]: inside of the retinular cells, send signals down to axon
Rhabdomeres: [blank_start]made of microvilli, full of action[blank_end]
[blank_start]Membrane of the Rhabdomeres[blank_end]: contain lots of photopigments (Rhodopsin)
Answer
-
focuses light into central aspect
-
Ommatidium
-
Support Cells
-
transfer information to the rhabdomeres
-
Rhabdomeres
-
made of microvilli, full of action
-
Membrane of the Rhabdomeres
Question 5
Question
Why do Rhabdomeres have so many microvilli?
Answer
-
To help it move around for better signal transduction
-
To help it contact the Retinular cells
-
To increase SA and the amount of Rhodopsin that can be contained on the membrane
Question 6
Question
What is the 2nd messenger cascade for Rhodopsin receptors?
Answer
-
G protein --> IP3/PKC --> activate TRP cation channel
-
G protein --> Rab 2 --> activate TRP cation channel
-
G protein --> IP3/PKC --> Ca2+ release from SER
Question 7
Question
The vertebrate eye differs from the compound eye in that the vertebrate eye has the ability to focus light, giving it more acuity.
Question 8
Question
What does the fluid filled portion of the eye introduce?
Answer
-
Diffraction
-
Reflection
-
Refraction
-
Squishy Stuff
Question 9
Question
[blank_start]Convex[blank_end] lenses cause light to converge while [blank_start]concave[blank_end] lenses cause light to diverge. This is caused by [blank_start]refraction[blank_end].
Answer
-
Convex
-
Concave
-
concave
-
convex
-
refraction
-
diffraction
-
reflection
Question 10
Question
Striated Muscle is:
Question 11
Question
The smallest unit of skeletal muscle is called a myoblast
Question 12
Question
Identify the correct order for the creation of a multinucleated muscle cell
Answer
-
Myoblast, myotubule, myocyte
-
Myocyte, myotubule, myoblast
-
Myotubule, myocyte, myoblast
-
myotubule, myoblast, myocyte
Question 13
Question
What makes a muscle striated?
Question 14
Question
Thick filaments are made of [blank_start]myosin[blank_end] and thin filaments are made of [blank_start]actin[blank_end].
Question 15
Question
Label the lines and bands on the sarcomere below:
Answer
-
Z-Disk
-
H-Zone
-
M-Line (Myosin)
-
Actin
-
I-Band
-
A-Band
Question 16
Question
In the sarcomere, [blank_start]titin[blank_end] asociates with myosin and [blank_start]nebulin[blank_end] associates with actin.
Question 17
Question
Label the electromicrograph with the location of:
1) The A band
2) The I band
3) The H Band
4) How these components interact with light (put this on top of the location) --> only for A and I
Question 18
Question
What is the thin:thick ratio of filaments in mammal skeltal muscle?
Question 19
Question
Myosin is made up of:
Answer
-
2 heavy chains and 4 light chains
-
4 heavy chains and 2 light chains
-
1 heavy chain and 3 light chain
-
3 heavy chains and 1 light chain
Question 20
Question
The myosin heavy chain is made up of ______________ and the myosin light chains are made up of ________________.
Answer
-
tail, head, neck AND essential and regulatory units
-
head AND tail
-
neck AND head and tail
-
essential and regulatory units AND tail, head, neck
Question 21
Question
What two binding sites does the myosin head contain?
Answer
-
Actin and ATP
-
Calcium and ATP
-
Actin and Calcium
Question 22
Question
What happens if trypsin is added to myosin?
Question 23
Question
What happens when Papain is applied to myosin?
Question 24
Question
There are 2 myosin light chain components per head. For a total of 4 MLC components.
Question 25
Question
What are the two forms of actin?
Answer
-
Globular & Filamentous
-
Aggregated & Spiraled
Question 26
Question
What are the two main regulatory proteins that associate with actin?
Answer
-
Troponin
-
Tropomyosin
-
Malbulim
-
Triulin
Question 27
Question
What was proposed in the Sliding Filament Theory?
Answer
-
The width of the A-band remains constant, the I-band and H band gets shorter
-
The width of the I-band remains constant, the A-band gets shorter
-
The width of the H-band and I-band remains constant, the I-band gets shorter
Question 28
Question
A. Huxley and H. Huxley both confirmed the Sliding Filament Theory through different methods.
Question 29
Question
Describe what is happening at each of the points identified in the graph
Answer
-
Myosin is being crushed by the Z-disks
-
Polarity Interference; reduces Ca releas
-
Maximal cross bridge overlap
-
A little overlap
-
No more cross-bridges being formed
-
Ascending Limb
-
Plateau
-
Descending Limb
Question 30
Question
Pure actin contains [blank_start]no binding proteins[blank_end]. Native actin contains [blank_start]tropomyosin and troponin[blank_end].
Answer
-
no binding proteins
-
tropomyosin and troponin
Question 31
Question
What characterizes rigormortis?
Answer
-
Calcium is present, ATP is absent
-
Calcium is absent, ATP is present
-
Troponin is present, tropomyosin is absent
-
Tropomyosin is absent, troponin is present
Question 32
Question
What is the phyisiological calcium concentration?
Answer
-
10^-9 M
-
10^-5 M
-
10^-2 M
-
10^-3 M
Question 33
Question
What is the highest number of calcium ions that troponin C can bind to?
Question 34
Question
Do invertebrates have Na+ channels in T tubules?
Question 35
Question
How is an action potential propogated in invertebrate T Tubules?
Question 36
Question
What type of ACh receptors do skeltal muscles have?
Question 37
Question
What stores calcium in a cell?
Answer
-
Mitochondria
-
Lysosome
-
Smooth ER
-
Rough ER
Question 38
Question
What does it mean to be an "L-type" voltage gated channel?
Answer
-
Long-lasting activation
-
Short-activation
Question 39
Question
What type of receptor is dihydrophyridine?
Question 40
Question
What type of receptor is ryanodine?
Question 41
Question
The dihydropyridine receptor is localized on the T-tubules while the ryanodine receptor is localized on the SER membrane.
Question 42
Question
The huge difference in concentration between the SER and the cytoplasm helps with [blank_start]diffusion[blank_end] but, not with [blank_start]reuptake[blank_end]. Therefore, [blank_start]calsequesterin[blank_end] helps to sequester calcium in the SER and help the SERCa pumps wor.
Answer
-
diffusion
-
reuptake
-
calsequesterin
-
calmodulin
Question 43
Question
Which elements in muscle contribute to the resting tension (if a muscle were to be pulled without cross-bridges forming)?
Answer
-
Parallel Elements
-
Series Elements
-
Perpendicular Elements
Question 44
Question
What type of elements do tendons serve as in muscle mechanics?
Question 45
Question
What is the difference between a concentric and an eccentric contraction? (concentric, eccentric)
Answer
-
Muscle shortens, Muscle lengthens
-
Muscle lengthens, Muscle shortens
Question 46
Question
Why is the muscle force generated from a single depolarization relatively small?
Answer
-
It takes time for the series elastic components to stretch and generate force
-
It takes time for the parallel elastic components to stretch and generate force
-
It takes time for the contractile elements to stretch and generate force
Question 47
Question
Incomplete tetanus occurs when there is a [blank_start]small refractory period[blank_end] between action potentials. Fused or complete tetanus occurs when there is [blank_start]no refractory period[blank_end] between action potentials.
Answer
-
small refractory period
-
no refractory period
Question 48
Question
As tetanus occurs, the overall force that the muscle can generate increases but, the force reaches a plateau after fused tetanus occurs.
Question 49
Question
What is contained in a motor unit?
Question 50
Question
The motor neuron extends out of the [blank_start]ventral[blank_end] horn of the spinal cord
Question 51
Question
Spatial Summation controls:
Answer
-
The number of muscle cells recruited
-
The distribution of muscle cells in the body
-
The areas of the body that respond to external stimuli
Question 52
Question
What happens in a skeletal muscle cell as the velocity of shortening increases
Question 53
Question
Power reaches a max at 20-40% of Vmax.
Question 54
Question
The muscle uses ATP in the following ways:
25%: [blank_start]Pumping calcium via SERCa pumps[blank_end]
[blank_start]50%[blank_end]: Heat
[blank_start]25%[blank_end]: Useful work in the cross-bridge cycle
Question 55
Question
What is muscle efficiency?
Question 56
Question
Is there work generated from an isometric contraction?
Question 57
Question
What are the three sources of ATP for muscle?
Question 58
Question
Which two (helper) proteins are involved in the smooth muscle thick and thin filament network?
Answer
-
Caldesmon
-
Xinculin
-
Alpha-actin
-
Shelanin
Question 59
Question
STRESS RELAXATION ALLOWS ORGANS THAT ARE LINED BY SMOOTH MUSCLE (E.G. THE GUT) TO ACCOMMODATE LARGE CHANGES IN DIAMETER AND STILL PRODUCE ABOUT THE SAME AMOUNT OF FORCE
Question 60
Question
Match the type of smooth muscle with its mechanism of action:
1. Single Unit Smooth Muscle (Visceral): [blank_start]gap junctions, myogenic[blank_end]
2. Multi-unit Smooth Muscle: [blank_start]independent, neurogenic, fine control[blank_end]
Question 61
Question
How does visceral smooth muscle depolarize without neural input?
Question 62
Question
Where are neurotransmitters released from in neural activation of smooth muscle?
Question 63
Question
What is the neurotransmitter and receptor type involved in parasympathetic smooth muscle activation?
Answer
-
Ach, nicotinic
-
Ach, muscarinic
-
Epi, alpha
-
Epi, beta
Question 64
Question
What is the neurotransmitter(s) and receptor type(s) involved in sympathetic smooth muscle activation?
Answer
-
Alpha (Norepi & Epi) - contraction; Beta (Epi)- relaxation
-
Beta (Norepi & Epi) - contraction; Alpha (Epi)-relaxation
-
Beta (Epi) - contraction; Alpha (Norepi & Epi) - relaxation
Question 65
Question
What is it about smooth muscles that allow for Calcium diffusion WITHOUT the presence of T-Tubules?
Question 66
Question
The SER is the primary source of Calcium for smooth muscles.
Question 67
Question
What does MLCK do?
Answer
-
Phosphorylate MLC
-
Dephosphorylate MLC
-
Hydroxylate MLC
-
Dehydroxylate MLC
Question 68
Question
What is an antagonist of MLCK?
Answer
-
MLC phosphotase
-
MLC hydrotase
-
MLC dehydrogenase
-
MLC transferase
Question 69
Question
What are the effects of serotonin and protein kinase C on smooth muscle?
Question 70
Question
How is protein kinase activated in smooth muscle and how does it affect MLCK?
Answer
-
Activated by Beta2 receptors; phosphorylates MLCK; inactivates it
-
Activated by Beta2 receptors; phosphorylates MLCK; activates it
-
Activated by Alpha1 receptors; phosphorylates MLCK; inactivates it
-
Activated by Alpha1 receptors; phosphorylates MLCK; activates it
Question 71
Question
Is Protein Kinase C an inhibitory or excitatory protein in smooth muscle contraction?
Question 72
Question
What is reciprocal innervation and when does it occur?
Answer
-
Excitation to neuron and inhibition to another; withdrawl reflex
-
Excitation to neuron and inhibition to another; cross-extensor reflex
-
Excitation to neuron and inhibition to another; stretch reflex
Question 73
Question
What is the muscle involved in a myotatic/stretch reflex and what are some of its basic characteristics?
Question 74
Question
What are the receptors contained within the intrafusal muscle?
Answer
-
Annulospiral Receptor
-
Flower Spray Receptor
-
Dihydropuridine Receptor
-
Ryanodine Receptor
Question 75
Question
What type of neuron is used by Annulospiral Receptors
Answer
-
IA - afferent
-
IIA- afferent
-
IIIA - afferent
Question 76
Question
What type of neuron is used by Flower Spray Receptors in a myotatic reflex?
Answer
-
IA - afferent
-
IIA - afferent
-
IIIA- afferent
Question 77
Question
Label the layers of the skin and the 4 mammalian mechanoreceptors
Answer
-
Epidermis
-
Dermis
-
Pacinan Corpuscle
-
Ruffini Ending
-
Messiner's Corpuscle
-
Merkel Discs
-
Free Nerve Ending
-
Hair Cell
Question 78
Question
What type of cell is this?
Question 79
Answer
-
Pinna
-
External Auditory Meatus
-
Tympanic Membrane
-
Ossicles
-
Semi-circular canals
-
Auditory Nerve
-
Cochlea
-
Oval Window
-
Round Window
-
Outer Ear
-
Middle Ear
-
Inner Ear
Question 80
Question
Label the diagram
Answer
-
External auditory meatus
-
Tympanic Membrane
-
Malleus (Hammer)
-
Incus (Anvil)
-
Stapes (Stirup)
-
Oval Window
-
Round Window
Question 81
Question
The two muscles involved in dampening noise to the inner ear are the tensor tympani muscle and the stapedius muscle. The tensor tempani is active when we are [blank_start]chewing[blank_end] whereas the stapedius muscle contracts when we are [blank_start]talking[blank_end].
Question 82
Question
Label the inner ear
Answer
-
Oval Window
-
Scala Vestibuli
-
Helicotrema
-
Scala tympani
-
Stapes
-
Vestibular Membrane
-
Basilar Membrane
-
Scala Media
-
Organ of Corti
-
Round Window
Question 83
Question
The scala vestibuli and the scala tempani are continuous, there is no membrane separating them from eachother.
Question 84
Question
The organ of Corti sits on top of the Basilar Membrane.
Question 85
Question
Label pathway 1 and 2 with their purpose.
Question 86
Question
The perilymph has a [blank_start]similar make up to the ECF[blank_end]. The Endolymph has a [blank_start]high K+ concentration[blank_end].
Question 87
Question
Humans can hear between what frequency?
Answer
-
20 Hz-2000 Hz
-
200-2000 Hz
-
1000-2000 Hz
Question 88
Question
Label the image. Which organ is this?
Answer
-
Organ of Corti
-
Tectorial Membrane
-
Scala Media
-
Support Cells
-
Inner Hair Cells
-
Auditory Nerve
-
Stereocillia
-
Outer Hair Cells
Question 89
Question
Outer hair cells [blank_start]control auditory transduction[blank_end] by lengthening and shortening the hair cells, while inner hair cells [blank_start]lead to auditory transduction[blank_end].
Question 90
Question
What is the kinocilium?
Question 91
Question
What are tip links connected to?
Question 92
Question
Why do Calcium and potassium enter stereocilia when stretch-gated channels are opened?
Answer
-
Hair cells are in the endolymph
-
Hair cells are in the perilymph
-
Hair cells are in the ECF
Question 93
Question
Which organs provide us information about balance and movement?
Answer
-
Semicircular Canals
-
Otolith Organs
-
Stapes
-
Ampulla
Question 94
Question
There are [blank_start]three[blank_end] semicircular canals that provide us information about [blank_start]rotational movement[blank_end]. The Utricle and Saccule are [blank_start]Otolith organs[blank_end] that give information about [blank_start]linear movement[blank_end]. The Utricle signals [blank_start]horizontal movement[blank_end], while the Saccule signals [blank_start]verticle movement[blank_end].
Answer
-
three
-
two
-
four
-
rotational movement
-
Otolith organs
-
linear movement
-
horizontal movement
-
verticle movement
Question 95
Question
Label the diagram
Answer
-
Semicircular Canals
-
Utricle
-
Saccule
-
Cochlea
-
Ampulla
-
Auditory Nerve
-
Oval Window
-
Round Window
Question 96
Question
What fluid fills the semi-circular canals?
Question 97
Question
If you rotate your head to the left, which way is the fluid in the semicircular canals moving?
Question 98
Question
When the head rotates, the ampulla in each ear
Question 99
Question
When the ampulla moves it pulls on the __________, which affects ___________.
Answer
-
Hair cells, stretch activated channels
-
Stapes, stretch activated channels
-
Stretch activated channels, hair cells
Question 100
Question
When the hair cells are pushed towards the kinocilium, the cells are [blank_start]depolarized[blank_end]. When the hair cells are pushed away from the kinocilium, the cells are [blank_start]hyperpolarized[blank_end].
Answer
-
hyperpolarized
-
depolarized
Question 101
Question
When you move along one axis, the hair cells in one ear are depolarized while the hair cells in the other ear are hyperpolarized. This helps you determine directionality of the movement.
Question 102
Question
What happens to the ampulla after you consume a generous amount of alcohol?
Answer
-
Specific Gravity of fluid in the canals changes --> ampulla flops over
-
Your otoliths detach and make you feel like you are spinning
-
Your semicircular canals become blocked
Question 103
Question
What are otoliths?
Answer
-
The smallest bones in the body
-
Small Stones of calcium carbonate
-
They are part of the hair cell
Question 104
Question
Label the diagram
Answer
-
Kinocilium
-
Stereocillia
-
Otoliths
-
Gelatinous Layer
-
Hair Cell
-
Support Cell
-
Nerve Fibre
Question 105
Question
What is the function of otoliths and the gelatinous layer they are found in?
Answer
-
They cause a lag in the movement of hair cells which helps us detect linear motion
-
They contact hair cells to activate them
-
They cause the cell to depolarize
Question 106
Question
What is vertigo caused by?
Question 107
Answer
-
Fovea
-
Optic Disk
-
Optic Nerve
-
Sclera
-
Lens
-
Vitreous Humor
-
Aqueous Humor
-
Cornea
-
Pupil
-
Iris
-
Ciliary Body
-
Suspensory Ligaments
-
Retina
Question 108
Question
Where does the majority of refraction take place (in the eye)?
Answer
-
Lens
-
Cornea
-
Retina
-
Aqueous Humor
Question 109
Question
What produced aqueous humor?
Answer
-
Cornea
-
Ciliary Bodies
-
Conjunctiva
-
Lens
Question 110
Question
What does the aquous humor do?
Question 111
Question
How is vitreous humor produced?
Question 112
Question
What is the structure that allows aqueous humor to drain from the eye?
Answer
-
Tear Duct
-
Conjunctiva
-
Pupil
-
Canals of Schlem
Question 113
Question
How many mL of aqueous humor is produced in a day?
Question 114
Question
What is the purpose of the iris?
Question 115
Question
Match the muscle with 1) Movement of eye 2) Where it is located in the iris 3) which system it responds to:
Circular: [blank_start]constrictive[blank_end]; [blank_start]center[blank_end]; [blank_start]parasympathetic[blank_end]
Radial: [blank_start]dilates[blank_end]; [blank_start]outer portion[blank_end]; [blank_start]sympathetic[blank_end]
Answer
-
constrictive
-
center
-
parasympathetic
-
dilates
-
outer portion
-
sympathetic
Question 116
Question
Label the image,
- the blue and pink arrows indicated the type of stimulation
- label the other lines with the characteristics of that particular part of the eye
- In front of the cornea of each eye, label the type of light that causes the observed changes
Answer
-
Sympathetic Stimulation
-
Far object --> light comes in parallel
-
Near object --> light comes in diverging
-
Relaxed Ciliary Muscles
-
Flattened, weak lens
-
Tight suspensory ligaments
-
Parasympathetic Stimulation
-
Contracted Ciliary Muscles
-
Strong, Rounded Lens
-
Loose suspensory ligaments
Question 117
Question
Match the terms:
Normal Vision: [blank_start]emmetropia[blank_end]
Near-sighted: [blank_start]myopia[blank_end]
Far- sighted: [blank_start]hyperopia[blank_end]
Answer
-
emmetropia
-
myopia
-
hyperopia
Question 118
Question
How do you correct myopia?
Question 119
Question
What happens in hyperopia?
Question 120
Answer
-
The crystalline structure in our eyes starts to deteriorate
-
Cataracts form
-
Lens becomes more flexible
-
Lens becomes less flexible
-
Presbyopia develops
-
Near-Sighted
-
Far-sighted
Question 121
Question
Label the Retinal Cells
Answer
-
Light
-
Ganglion Cell
-
Amacrine Cells
-
Bipolar Cells
-
Horizontal Cell
-
Rod
-
Cone
-
Back of Retina
Question 122
Question
What is it about the processing cells in the retina that allow light to travel to the photoreceptors?
Answer
-
They are transparent
-
There are spaces between the cells for light to pass through
-
Light cannot pass through, it has to be transmitted through the processing cells first
Question 123
Question
What is at the optic disk?
Question 124
Question
There are many more rods than cones in the retina.
Question 125
Question
There are more [blank_start]rods[blank_end] than [blank_start]cones[blank_end] in the retina. Rods are activated by [blank_start]low light[blank_end] and have a [blank_start]slow[blank_end] response time. Cones are activated in [blank_start]intense light[blank_end] and have a [blank_start]fast[blank_end] response time. Rods are [blank_start]monochromatic[blank_end] while cones are [blank_start]trichromatic[blank_end].
Answer
-
rods
-
cones
-
low light
-
slow
-
intense light
-
fast
-
monochromatic
-
trichromatic
Question 126
Question
Cones are better than rods in detecting changes in visual stimuli.
Question 127
Question
Which neurotransmitter is released by rods and cones?
Answer
-
Glutamate
-
Dopamine
-
Serotonin
-
Glutamine
Question 128
Question
Why are cones better at transducing light?
Question 129
Question
Retinal is derived from which vitamin?
Answer
-
Vit B1
-
Vit B6
-
Vit E
-
Vit A
Question 130
Question
When no light is present, retinal is in the all [blank_start]cis[blank_end] form. When light hits, it is converted into the all [blank_start]trans[blank_end] form. This form is also called [blank_start]metarhodopsin II[blank_end].
Answer
-
cis
-
trans
-
metarhodopsin II
Question 131
Question
cGMP phosphodiesterase converts [blank_start]cGMP[blank_end] into [blank_start]5' GMP[blank_end] which causes the rod cell to [blank_start]hyperpolarize[blank_end].
Answer
-
cGMP
-
5' GMP
-
hyperpolarize
Question 132
Question
If an on-center bipolar cell is stimulated, this means that the off-center bipolar cell will not be stimulated.
Question 133
Question
Label the diagram
Answer
-
Photoreceptor = hyperpolarized (LIGHT)
-
On-center bipolar (DEPOL)
-
On-center Ganglion (DEPOL)
-
Off-center Bipolar (HYPERPOL)
-
Off-center Ganglion (HYPERPOL)
-
Few APs
-
Many APs
Question 134
Question
What type of pathway is visual transduction following in this pathway ?(label in top L corner)
Label the cell types present
Answer
-
Vertical Pathway
-
Lateral Pathway
-
Photoreceptor = HYPERPOL (LIGHT)
-
Horizontal = HYPERPOL
-
Adjacent PR = DEPOL
-
Adjacent PR = HYPERPOL
-
On-center bipolar = HYPERPOL
-
Off-center bipolar = HYPERPOL
-
Off-center ganglion = HYPERPOL
-
On-center ganglion = HYPERPOL
-
Few APs
-
Lots of APs
Question 135
Question
What type of process would generate these responses?
Answer
-
On-Center Processes
-
Off-Center Processes
Question 136
Question
What type of processes would generate these responses?
Answer
-
Off-Center Processes
-
On-Center Processes
Question 137
Question
Blue cones contain the pigment [blank_start]cyanolabe[blank_end]
Green cones contain the pigment [blank_start]chlorolabe[blank_end]
Red cones contain the pigment [blank_start]erythrolabe[blank_end]
Answer
-
cyanolabe
-
Chlorolabe
-
Erythrolabe
-
chlorolabe
-
Cyanolabe
-
erythrolabe
-
erythrolabe
-
cyanolabe
-
chlorolabe
Question 138
Question
Blue light has the [blank_start]shortest[blank_end] wavelength of light, while red has the [blank_start]longest[blank_end].
Question 139
Question
What is color blindness caused by?