Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIO MIDTERM 3 > BIO MIDTERM 3 > Flashcards

BIO MIDTERM 3 Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

cells go through a program of …

A

differentiation and morphogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

the fate of cells in the embryo is determined by …

A

cytoplasmic determinants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

cleavage generates…

A

lots of small undifferentiated cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

cleavage is followed by

A

gastrulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

gastrulation…

A

organises these cells into 3 germ layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the 3 germ layers and what are they involved in

A

ectoderm, endoderm and mesoderm
involved in gastrulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

germ layers develop into …

A

organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

a single celled zygote gives rise to …

A

cells of many different types, each with a different structure and corresponding function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

during embryonic development, fertilized egg gives rise to…

A

many different cell types

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

gene expression orchestrates…

A

the development programs of animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what processes transform the zygote to adult

A

cell division, cell differentiation and morphogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

cell differentiation is the …

A

process by which cells become specialized in structure and function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

morphogenesis is

A

the physical process that gives an organism its shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

an egg’s cytoplasm contains…

A

RNA, proteins, and other substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how are the contents of the unfetilized egg distributed

A

UNEVENLY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are cytoplasmic determinants

A

maternal substances in the egg that influence early development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what happens when the zygote divides by mitosis

A

cells contain different cytoplasmic determinants which lead to different gene expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what time is important for cytoplasmic determinants

A

when the zygote divides by mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

other than cytoplasmic determinants what is another important source of developmental information

A

INDUCTIVE SIGNALS aka the environment around the cell especially signals from nearby embryonic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is inductive signals

A

signal molecules from embryonic cells cause transcriptional changes in nearby target cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

interactions between cells can …….

A

INDUCE differentiation of specialized cell types

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does determination do?

A

commits a cell to its final fate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the order of differentiation and determination?

A

determination precedes differentiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

cell differentiation is marked by…

A

the production of tissue specific PROTEINS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

give an example of tissue specific proteins

A

MyoD protein in muscle cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

myoblasts produce…

A

muscle specific proteins and form skeletal muscle cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

MyoD is ….
(what does it produce?)

A

one of several master regulatory genes

myoblasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is the function of MYoD…

A

they produce proteins that commit the cell to becoming skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

the myoD protein does what to the actual DNA

A

is A TRANSCRIPTION FACTOR that binds to enhancers of various target genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what are the two things that describe MYOD

A

master regulatory gene
TRANSCRIPTION FACTOR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is pattern formation

A

the development of spatial organization of tissues and organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

IN ANIMALS pattern formation begins with

A

the establishment of the major axes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

In drosophila, cytoplasmic determinants in the unfertilized egg do what?

A

determine the axes before fetilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

in fruit flies, after fetilization …

A

the embryo develops into a segmented larava with three larval stages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

A bicoid is what type of gene…

A

maternal effect gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what part of the body does the bicoid gene effect

A

the front half of the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what would happen to an embryo whose mother has no functional bicoid gene

A

lacks the front half of its body and has duplicate posterior structures at both ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what is a bicoid …

A

a morphogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

the bicoid comes from the

A

MOTHER’s genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

the product of the mother’s bicoid gene is concentrated at the

A

future anterior end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what is the morphogen gradient

A

in which gradients morphogens establish an embryo’s axes and other features

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what are morphogens

A

gradients of substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

why is bicoid research important

A

it identifies a specific protein required for some early steps in pattern formation

it increased understanding of the mother’s role in embryo development

it demonstrated a key developmental principle that a gradient of molecules can determine polarity and position in the embryo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what are the embryonic development stages

A

fertilization, cleavage, gastrulation organogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what is fertilization

A

combination of sperm and egg nuclei and egg activation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

3 words that describe fertilization

A

HAPLOID TO DIPLOID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what is cleavage

A

rapid cell divisions without substantial growth in size to generate a multicellular embryo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is gastrulation

A

mass cell movements to generate three germ layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what is organogenesis

A

localized changes in tissue and cell shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

cleavage splits the ….

A

the cytoplasm of one large cell into many smaller cells called blastomeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

what is the blastula

A

ball of cells with fluid like cavity in the center

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what is the fluid-filled cavity in the blastula called

A

blastocoel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what is the yolk

A

stored nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what is a key factor influencing the pattern of cleavage?

A

the distribution of yolk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

describe the amount of yolk at each pole

A

vegetal pole has more yolk
animal pole has less yolk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

the difference in yolk distibution results in

A

animal and vegetal hemispheres that differ in appearance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

when do animal embryos complete cleavage

A

when the ratio of material in the nucleus relative to the cytoplasm is sufficiently large

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

what happens after cleavage

A

the rate of cell divisions slows and the normal cell cycle is restored

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

morphogenesis in animals involves

A

specific changes in cell shape, position and survival

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what are the two types of morphogenesis

A

gastrulation and organogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

how does frog gastrulation begin

A

when a group of cells on the dorsal side of the blastula begins to invaginate (be turned inside out)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

the beginning of gastrulation causes

A

a crease along the region where the gray cresent formed in the zygote

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

the part above the crease is called

A

the dorsal lip of the blastopore

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

how do the cells move from the embryo surface into the embryo

A

by involution (inward movement)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

the cells on the inside form the

A

endoderm and the mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

the cells on the embryo surface will form the

A

ectoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

the ectoderm is the

A

outer layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

the mesoderm is the

A

middle layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

the endoderm is the

A

inner layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

the ectoderm forms the

A

epidermis of the skin and its derivatives, nervous and sensory systems, was. and teeth, pituitary glands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

the mesoderm forms the

A

skeletal and muscular systems
circulatory and lymohatic systems
excretory and reproductive systems
dermis of skin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

the endoderm forms the

A

epithelial ining of digestive trats
epethilial lining of respiratory, excretory and reproductive tracts
thymus , thyroid, parathyroid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

in early vertebrate organogenesis, ….

A

the notochord forms from mesoderm
neural plate forms from ectoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

the neural tube will become the

A

central nervous system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

the neural crest cells develop along the

A

neural tube of vertebrates and form various part of the embryo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

the neural plate curves inward forming the …

A

neural tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What is the dorsal lip?

A

tissue
its cells commit to invaginate into the blastula –> initiates gastrulation and forms the notochord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What is the notochord?

A

main axial skeletal element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

information is processed by …

A

neurons organised into the brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

what are the three types of neuronal types

A

sensory neurons, interneurons and motor neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

how do neurons transmit information?

A

through propagated changes in the membrane known as ACTION POTENTIALS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

action potentials are the result of …

A

opening and closing of voltage gates sodium and potassium channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

neurons are …

A

nerve cells that transfer information within the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

what are the two signals that neurons use to communicate

A

electrical and chemical

84
Q

what is the difference between electrical and chemical signals

A

electrical is LONG DISTANCE
chemical is SHORT DISTANCE

85
Q

WHAT does the central nervous system include

A

brain and spinal cord

86
Q

what does the peripheral nervous system include

A

cranial nerves, ganglia outside CNS, and spinal nerves

87
Q

where does processing of information take place>

A

ganglia or brain

88
Q

what is a brain

A

complex organization of neurons

89
Q

what are the three stages of information processing

A

sensory input
integration
motor output

90
Q

which part of the information processing happens in the CNS? PNS?

A

sensory input and motor output take place in the PNS

integration happens in the CNS

91
Q

synapse?

A

a junction between an axon and another cell

92
Q

synaptic terminal?

A

passes information across the synapse in the form of chemical messengers called neurotransmitters

93
Q

what are the chemical messengers in neurons

A

neurotransmitters

94
Q

describe the pathway of information in a neuron

A

a neuron receives information, transmits it along an axon, and transmits the information to other cells via synapse

95
Q

what is something neurons cannot do

A

go through cell cycle/ divide

96
Q

the cell body houses

A

the nucleus + organelles+ ALL DNA

97
Q

dendrites?

A

receive information and pass it to cell body

98
Q

what happens at the Axon Hillick

A

where axon is attached to the cell body
generates electrical signals
WHERE ACTION POTENTIAL IS GENERATED

99
Q

where does chemical signaling occur

A

at the synapse

100
Q

where does electrical signaling happen

A

along the axon

101
Q

in how many directions can electrical impulses travel in

A

ONEE

102
Q

an electrical impulse is ______ but the _________ _ ______ varies

A

identical
frequency of signaling

103
Q

sensory neurons do what

A

receive sensory information

104
Q

what do interneurons do?

A

process information

105
Q

what do motor neurons do?

A

control muscles, gland
carry out physical response

106
Q

what do glands do in response to stimulus

A

secrete things

107
Q

what is the name given to the cell from where information is transmitted from

A

presynaptic cell

108
Q

what is the name of the cell where the information is received?

A

postsynaptic cell

109
Q

most neurons are nourished or insulated by cells called

A

glia

110
Q

what are the types of glia cells

A

astrocytes
ependymal cells
microglia
oligodendrocytes and schwann cells

111
Q

astrocytes?

A

support neurons and form the blood-brain barrier

112
Q

ependymal cells?

A

promote circulation of cerebrospinal fluid

113
Q

microglia?

A

protect the nervous system from microogranisms

114
Q

oligodendrocytes and schwann cells

A

form the myelin sheath around axons

115
Q

difference between Schwann cells and oligodendrocytes

A

schwann found in peripheral nervous system
oligodendrocytes in cns

116
Q

what is a membrane potential

A

voltage (Difference in electrical charge) across its plasma membrane

117
Q

(electrical) how are messages transmitted in TWO WORDS

A

membrane potential

118
Q

resting potential ?

A

membrane potential of a neuron not sending signals

119
Q

what is the resting potential in humans

A

-70mv

120
Q

what maintains the resting potential of a neuron

A

ion pumps and ion channels

121
Q

in mammalian neuron at resting potential, the concentration of K+ is…. NA+??`

A

greater inside the cell for K+
greater outside the cell NA+

122
Q

sodium-potassium pumps use

A

the energy of ATP to maintain these K+ and Na+ gradient across the plasma membrane

123
Q

the concentration gradients of k and na represent

A

chemical potential energy

124
Q

leak channels?

A

allow K+ to leak outside the cell

125
Q

what type of membrane ion channel is most likely to be open when a neuron is not transmitting an electrical signal

A

those channels that admit K+ ions

126
Q

resting neurons are most permeable to

A

K+ ions

127
Q

what can contribute to the negative charge within the neuron

A

anions trapped inside the cell

128
Q

the opening of ion channels in the plasma membrane converts…

A

chemical potential to electrical potential

129
Q

a neuron at resting potential contains…

A

many open K+ channels (leak channels ) and fewer open NA+ channels

130
Q

voltage gated ion channels?

A

open or close in response to stimuli

131
Q

when do leak potassium channels open?

A

always open

132
Q

why are leak potassium channels good?

A

they help set the resting potential

133
Q

why are voltage-gated potassium channels important

A

for restoring membrane potential following depolarization

134
Q

how do voltage gated potassium channels open?

A

open slowly causing delayed efflux (movement out of neuron) of potassium

135
Q

why are gated sodium channels important

A

for depolarizing membrane (making more positive) during action potential

136
Q

how does the voltage gates sodium channels open

A

opens rapidly allowing influx of sodium`

137
Q

voltage gates calcium channels open when?

A

when membrane depolarises and lets calcium flow into cell

138
Q

why are voltage gates calcium channels important

A

for synaptic release

139
Q

at resting potential voltage gated NA+ channels are –> open/ closed?

A

closed

140
Q

when the membrane is depolarised the voltage gated NA channels are …

A

open

141
Q

in depolarization the membrane potential becomes …

A

less negative

142
Q

what is the action potential threshold

A

-55mv

143
Q

action potential is an ___ or ___ response

A

ALL OR NONE response

144
Q

the action potential carries info across …

A

axon

145
Q

how many actions potentials can a neuron produce

A

hundreds of action potential

146
Q

what reflects the strength of a stimulus

A

the frequency of action potential

147
Q

what are the stages of an action potential

A

1) resting state
2) depolarization ( some NA channels open)
3) rising phase of the action potential
4) falling phase of the action potential( gates NA channels close and most gates K channels open)
5) undershoot

148
Q

different regions of the brain are responsible for …

A

different function

149
Q

imbalances in neurotransmitters are associated with …

A

neurological/psyhchological disorders

150
Q

different neurons use different…

A

neurotransmitters

151
Q

temporal and spatial summation lead to

A

action potential generation

152
Q

neurotransmitters binding to receptors on the postsynaptic membrane generate …

A

a postsynaptic potential

153
Q

refractory period?

A

after an action potential a second action potential cannot be initiated

154
Q

the refractory period is a result of a

A

temporary inactivation of NA + channels

155
Q

how can an action potential travel long distances

A

by regenerating itself along the axon

156
Q

at the axon hillock…

A

an electrical current depolarizes the neighboring region of the axon membrane

157
Q

what prevents the action potential from traveling backward

A

inactivated NA+ channels behind the zone of depolarization

158
Q

what location do action potentials travel to

A

toward the synaptic terminals

159
Q

the speed of an action potential….

A

increases with the axon’s diameter

160
Q

in vertebrates axons are insulated by…

A

myelin sheath

161
Q

what is the effect of the myelin sheath?

A

causes an action potential’s speed to increase.

162
Q

what is the depolarized region of the axon

A

node of ranvier

163
Q

where are action potentials formed only ?

A

at nodes of ranvier

164
Q

nodes of ranvier?

A

gaps in the myelin sheath where voltage gated NA+ channels are found

165
Q

saltatory conduction?

A

the way action potentials in myelinated axons jump between the nodes of ranvier

166
Q

most synapses are…

A

chemical

167
Q

chemical synapse order …

A
  1. Arrival of action potential at synaptic
    terminal depolarizes membrane, opening
    voltage-gated channels that allow Ca2+ to
    diffuse into the terminal.
  2. This triggers vesicles to fuse with
    membrane and release neurotransmitter.
  3. The neurotransmitter diffuses across the
    synaptic cleft, binds to ligand-gated ion
    channels in the post-synaptic membrane,
    opening the channels.
168
Q

direct synaptic transmission involves…

A

binding of neurotransmitters to ligand-gated ion channel in post synaptic cells

169
Q

neurotransmitters binding causes…

A

ion channels to open, generating a post synaptic potential

170
Q

neurotransmitters can be…

A

excitatory or inhibitory
(cause firing or prevent firing)

171
Q

a single excitatory post synaptic potential is ….

A

not sufficient to trigger an action potential in a postsynaptic neuron

172
Q

a postsynaptic potential is a change…

A

in the membrane potential of the postsynaptic neuron

173
Q

temporal summation?

A

two EPSP (excitatory postsynaptic potential) are produced in rapid sucession

174
Q

a single EPSP is usually..

A

too small to trigger an action potential in a postsynaptic neuron

175
Q

spatial summation?

A

EPSPs produced nearly simultaneously by different synapses on the same postsynaptic neuron ass together

176
Q

the combo of EPSPs through spatial and temporal summation can ….

A

can result in depolarization of the membrane and trigger an action potential

177
Q

what are the three options after the release of the neurotransmitter

A

1) may diffuse out of the synaptic cleft
2) may be taken up by surrounding cells
3) may be degraded by enzymes

178
Q

the same neurotransmitter can produce…

A

different effects in different types of cells

179
Q

what are the 5 major classes of neurotransmitters

A

acetylcholine, biogenic amines, amino acids, neuropeptides, and gases

180
Q

what are some amino acid neurotransmitters?

A

glutamate
GABA
GLYCINE

181
Q

what are some examples of biogenic amines

A

norepinephrine
dopamine
serotonin

182
Q

what is acetylcholine involved in

A

muscle stimulation, memory formation and learning

183
Q

what disrupts acetylcholine neurotransmitiion

A

a number of toxins
including nerve gas, serin, botulism

184
Q

what is botulism

A

a severe form of food poising
produced by certain bacteria

185
Q

where is acetylcholine common in?

A

vertebrate and invertebrates

186
Q

what are the two major classes of acetylcholine receptor?

A

ligand gates
metabotropic

187
Q

cholinergic neurons ….

A

release acytlcholine

188
Q

the neurotransmitters biogenic amines are derived from

A

amino acids

189
Q

most common biogenic amines

A

serotonin
dopamine
epinephrine
norepinephrine

190
Q

how can be depression treated

A

with drugs that block the reuptake of serotonin

191
Q

parkinson;s disease is associated with

A

lack of dopamine in the brain

192
Q

how do biogenic amines affect the body

A

affect sleep, mood, attention, learning and memory

193
Q

psychoative drugs like LSD and mescaline produce ____ by _________

A

produce hallucinatory effect by binding receptors for serotonin and dopamine

194
Q

dopaminergic neurons release

A

DOPAMINE

195
Q

what does the motor cortex control

A

control of skeletal muscles

196
Q

prefrontal cortex controls

A

decision making, planning

197
Q

broca’s area?

A

forming speech

198
Q

somatosensory cortex?

A

sense of touch

199
Q

sensory association cortex?

A

integration of sensory information

200
Q

visual association cortex

A

combining images and object recognition

201
Q

visual cortex?

A

processing visual stimuli and pattern recognition

202
Q

wernicke’s area

A

comprehending language

203
Q

cerebellum

A

coordinating movement and balance

204
Q

frontal lobe?

A

control over many abilities, including the way you think, how you move and how you remember things.

205
Q

pariental lobe ?

A

responsible for receiving and processing sensory input such as touch, pressure, heat, cold, and pain

206
Q

temporal lobe?

A

managing your emotions, processing information from your senses, storing and retrieving memories, and understanding language.

207
Q

occipital lobe?

A

responsible for visual perception, including colour, form and motion.

208
Q

why must neurotransmitters be terminated ASAP

A

so that the action potential doesn’t stay continuous

BIO MIDTERM 3 (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions