TEST 1 Flashcards
(239 cards)
1
Q
What is sensation?
A
The conscious awareness of stimuli received by sensory receptors. AKA perception
2
Q
Sensations arise from ______?
A
Sensory receptors
3
Q
Sensory receptors can be: (3)
A
- Entirely neurons
- Dendrites from neurons combines with non-neural cells.
- Neurons combined with other tissues in sensory organs
4
Q
Sensory receptors around the body respond to stimuli by generating ________ in the neurons they are associated with?
A
action potentials
5
Q
The action potential is a sequential series of ______?
A
voltage-gated ion channels opening one after another throughout the cell’s plasma membrane
6
Q
The action potential travels down the neuron’s axon to the _____ that the neuron synapses with?
A
target cell
7
Q
The target cell synapsed with the firing neuron is usually another ______?
A
neuron
8
Q
The action potential in the firing neuron causes that neuron to release _____ across the synapse to the target neuron?
A
neurotransmitters
9
Q
The target neurons respond to the neurotransmitters by generating their own action potentials which cause what?
A
neurotransmitters to be released across their own synapses.
10
Q
The _____ is the gray matter that makes up the outer most layer of the cerebrum?
A
cerebral cortex
11
Q
When a neuron fires, what travels down the neuron’s plasma membrane?
A
An action potential
12
Q
In general, the _____ the stimulus, the _____ the frequency of the action potentials arriving at the brain?
A
larger and greater
13
Q
The brain interprets the _____ (touch, or sound, or whatever) on the basis of the area of the brain stimulated?
A
nature of the stimulus
14
Q
The general senses are: (6)
A
- touch
- temperature
- pain
- pressure
- chemical detection
- proprioception
15
Q
What is proprioception?
A
The ability to sense the location and position of body parts
16
Q
The sensory receptors for the general senses are found where?
A
throughout the body
17
Q
What is somatic sense?
A
The sensory receptors for a general sense that are found in skin, muscles, or joints
18
Q
What is visceral sense?
A
The sensory receptors for a general sense that are found in internal organs like the stomach or heart
19
Q
Somatic sensory (SS) includes :
A
Touch, pain, pressure, vibration, temperature, and proprioception from the skin, body wall, and limbs
20
Q
Visceral Sensory (VS) includes:
A
Stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger
21
Q
What type of sense receives stimuli from receptors in the skin, muscles, or joints?
A
Somatic sense
22
Q
The special senses are: (5)
A
- smell
- taste
- sight
- hearing
- balance
23
Q
Why are the special senses “special”?
A
Their sensory receptors are in sense organs or in specialized areas of other organs
24
Q
Three ways that perception of stimulus information sent to the brain is reduced are:
A
- Unconscious processing
- Adaptation
- Selective Awareness
25
What is unconscious processing?
A lot of sensory information is sent to the CNS without our being consciously aware of it
26
What is an example of unconscious processing?
The maintaining of various homeostatic balances in the body such as pH, blood oxygen levels, blood metabolites levels, blood pressure, etc.
27
What is sensory adaptation (sensory accommodation)?
Sensory adaptation is the decreased awareness of stimuli that is consciously monitored. It is when sensory receptors trigger action potentials in their associated neurons less frequently in response to the same stimulus continued for some length of time
28
What is an example of sensory adaptation (sensory accommodation)?
Awareness of resting arms on table over time.
29
What is it called when action potential frequency decreases without the stimulus changing?
Sensory adaptation
30
What is selective awareness?
This results because we are more aware of stimuli we consciously choose to focus on, and less aware of other stimuli.
31
What are 7 main categories sensory receptors can be classified into according to the type of stimulus they respond to?
1. Mechanoreceptors
2. Baroreceptors
3. Chemoreceptors
4. Photoreceptors
5. Thermoreceptors
6. Nociceptors
7. Proprioceptors
32
Mechanoreceptors respond to?
Respond to mechanical stimuli (i.e., one producing a physical change), such as compression, bending, stretching.
33
Baroreceptors respond to?
Respond to pressure changes in blood vessels, digestive tract, respiratory tract, etc.
34
Chemoreceptors respond to?
Respond to specific chemicals, such as odor molecules, but also O2, blood sugar, etc.
35
Photoreceptors respond to?
Respond to light, located in the eye.
36
Thermoreceptors respond to?
Respond to temperature changes
37
Most thermoreceptors are in the _____ of the skin?
dermis
38
Nociceptors respond to?
Respond to painful mechanical, thermal, or chemical stimuli.
39
Nociceptors are abundant in the skin but are also found in?
internal organs and in joints
40
Proprioceptors respond to?
Detect position and movement of body parts relative to one another.
41
Where are proprioceptors located?
in muscles, skin, and internal organs
42
What do proprioceptors respond to?
Change in position of a body part
43
Baroreceptors can also be considered a subtype of ______ because pressure is a type of mechanical stimulus?
mechanoreceptor
44
_____ and _____ are mediated by chemoreceptors, but there are also other chemoreceptors throughout the body detecting important metabolite levels?
Smell and taste
45
What is a receptive field?
The area monitored by a single receptor neuron
46
The _____ the receptive field for a particular receptor, the greater the brain’s ability to determine the exact spot where a stimulus occurred?
smaller
47
The ability to determine the location of a stimulus is reflected in _____?
Two-point discrimination
48
What is two-point discrimination?
The ability to detect simultaneous stimulation at two points
49
What technique is used to determine receptive field areas throughout the body?
Two-point discrimination
50
On the tongue and fingertips, receptive fields are ls than ____ in diameter, allowing fine discrimination of stimuli.
1mm
51
Receptive fields of sensory neurons get ____ as you move up the arm?
larger
52
What are the five special senses?
- Smell (olfaction)
- Taste (gustation)
- Sight (vision)
- Hearing
- Balance
53
What is olfaction?
The sense of smell
54
What is gustation?
The sense of taste
55
What are odorants?
The molecules in the air that trigger the sense of smell
56
What the nasal cavity?
The large air filled space behind the nose where olfaction is initiated
57
The entire nasal cavity is lined with a mucus-secreting layer of epithelial tissue called the what?
the olfactory epithelium
58
The roof of the nasal cavity is separated from the brain by the _____?
ethmoid bone
59
Directly above the ethmoid bone are the _____ of the brain?
olfactory bulbs
60
What organ are the olfactory bulbs part of?
The brain
61
The olfactory epithelium is a _____ epithelium, with epithelial-lined glands dotted along it?
simple columnar epithelium,
62
A typical epithelial cell in the nasal cavity lasts about _____ months, but there are epithelial stem cells present to replace them?
three
63
The glandular epithelia in the nasal cavity secrete a thin nasal mucus that does what?
covers the surface of the nasal cavity
64
What does nasal mucus do?
It is sticky and serves to capture unwanted particles (dust, microbes) and as well as odorant molecules breathed into the nose
65
What are dendrites?
The branches that come off the cell body of a neuron and are the parts of the neuron that typically receive incoming signals that determine whether the neuron fires or not
66
The dendrites of olfactory neurons project onto the _____ surface of the olfactory epithelial cells?
apical (outside facing)
67
The dendrites of olfactory neurons are also called what?
olfactory cilia or olfactory hair
68
What are olfactory cilia?
The dendrites at the “start” of olfactory neurons.
69
The “cilia” of olfactory neurons are really just _____?
dendrites
70
Most of the epithelial cells of the nasal cavity have true epithelial cilia, what does it do?
They beat to move nasal mucus into the throat where most of it is swallowed, so stomach acid can destroy most of what is trapped there.
71
The olfactory neuron dendrites contain _____ in their plasma membranes?
odorant receptor proteins
72
The olfactory bulb where the olfactory neurons send their signals is part of the _____ system?
limbic system
73
What is the limbic system?
A group of structures from various sections of the brain that helps control emotions and motivations
74
What 2 main mechanisms cause adaptations to smells?
1. The olfactory bulb has feedback loops that inhibit olfactory neuron firing triggered by the same odorant binding to the same receptor.
2. Receptors themselves become less sensitive to the same odorant molecule and bind less of it after prolonged exposure, reducing the rate at which olfactory neurons fire.
75
What are tastants?
The molecules in saliva the mouth that trigger the sense of taste
76
What are taste buds?
the structures that detect taste
77
About how many taste buds are on the tongue?
10,000 taste buds
78
Most of the taste buds on the tongue are found as part of raised areas called ______?
papillae (nipple)s
79
What is the relationship between papillae and taste buds?
Sometimes they go together; sometimes there are papillae without taste buds; sometimes there are taste buds without papillae.
80
Each taste bud is made up of a bulb-like arrangement of specialized ______?
epithelial cells
81
Taste bud cells have a typical life span of about _____?
10 days
82
What are the 3 types of specialized epithelial cells in a taste bud?
1. taste cells
2. supporting cells
3. basal cells
83
What are taste cells?
They have receptors for different molecules that trigger the taste sensation
84
What are supporting cells?
they provide support
85
What are basal cells?
They are the epithelial stem cells that will divide and replace old cells
86
The taste cells within the taste bud are each connected to a _____?
neuron
87
What is a taste pore?
The opening just above each taste bud
88
What are taste hairs?
Microvilli projections on taste cells that project into the taste pore
89
What five primary tastes have been identified by humans?
1. salty
2. sour
3. sweet
4. bitter
5. umami (savoury)
90
What are salty tastes triggered by?
Na+
91
What are sour tastes triggered by?
Acids
92
What are sweet tastes triggered by?
sugars and proteins
93
What are bitter tastes triggered by?
alkaloids (bases)
94
What are umami (savoury) triggered by?
the amino acid glutamate (MSG) and related compounds
95
The visual system includes what?
eyes, visual nerves, and accessory structures
96
What do the eye accessory structures do?
protect, lubricate, and move the eye
97
The accessory structures of eyes are: (5)
- eyebrow
- eyelids
- tarsal glands
- conjunctiva
- lacrimal apparatus
98
What are the eyebrows purpose?
To protect the eye from direct perspiration and shade the eye from sun
99
What are the eyelids purpose?
to protect the eye, lubricate the eye and regulate the amount of light entering the eye
100
What muscle allows for both the upper and lower eyelid to open/close?
Orbicularis oculi muscle
101
Why can the upper eyelid be opened further?
by a small levator muscle
102
Where are tarsal glands located?
they are dotted along the inner margins of the eyelid across from the eyeball
103
What do the tarsal glands produce?
meibum
104
What is meibum?
An oily secretion form the tarsal glands that lubricate the lids and to restrain tears from flowing over the margin of the eyelids
105
What is meibum similar to?
sebum that secreted on the skin
106
Where is the caruncle?
at the medial margin of the eye where the upper and lower lid meet closest to the nose "mound of tissue"
107
What role does the caruncle serve?
None. It is a vestigial organ.
108
What is the conjunctiva?
It starts as part of the eyelid and attaches to the anterior/front surface of the eyeball and is a very thin and transparent layer of epithelial cells on top of a thin transparent layer of connective tissue
109
What role does the conjunctiva serve?
it reduces friction as the eyelid moves over the surface of the eye and serves as a barrier to the entry of microbes into the body
110
What is pink eye?
Conjunctivitis and it is when the conjunctiva gets inflamed due to a viral infection of its cells or due to an allergic reaction.
111
What is the role of the lacrimal apparatus?
It produces a constant flow of tears
112
About how many tears does the lacrimal apparatus produce per day?
1 mL
113
The functions do the tears produced by the lacrimal apparatus serve?
- reduce friction
- remove debris
- combat bacteria
- provide nutrients and oxygen to the epithelial cells of the conjunctiva
114
The lacrimal apparatus consists of:
- a lacrimal gland
- many lacrimal ducts
- a paired lacrimal canaliculi
- a lacrimal sac
- a nasolacrimal duct
115
What role does the lacrimal gland serve?
produces tears and secrete tears
116
What does tears mostly consist of?
water, lipids, salts, mucus, and lactoferrin and lysozyme
117
How do tears leave the lacrimal glands?
through several lacrimal ducts
118
Where are excess tears collected?
In 2 tubes called lacrimal canaliculi at the medial side of the eye, one superior and one inferior and then the canaliculi connect to the nasolacrimal duct which drains into the nasal cavity
119
What three layers is the eyeball composed of?
1. outer fibrous layer
2. middle vascular layer
3. inner retina
120
Most of the outer fibrous layer of the eyeball is the ______?
sclera
121
What is the "white" of the eye?
sclera
122
Is the sclera vascular or avascular?
vascular because it is supplied on its surface with some blood vessels
123
What is the sclera's purpose?
Help maintain eyeball shape, protects eyeball contents, and provides attachment point for the extrinsic muscles that move the eyeball
124
What is the other part of the outer fibrous layer of the eyeball?
cornea
125
Is the cornea vascular or avascular?
avascular
126
What is the cornea's purpose?
The cornea bends (refracts) the light entering the eye before the light is further bent by the lens and helps focus the light on the retina in the back of the eye
127
How does the cornea help the lens?
It starts bending the light before it is further bent and focused by the lens.
128
What is the middle vascular layer of the eye mostly made up of?
the choroid
129
What gives the choroid is black color
Its many melanin containing pigment cells
130
What purpose does the black color of the choroid serve?
The black color prevents it from reflecting light around the inside of the eye disrupting the light absorbing cells in the retina
131
In the front of the eye, the choroid thickens and becomes the ____?
ciliary body
132
What is the role of the ciliary body?
By contracting tits muscles, the ciliary body can change the shape of the lens to allow it to change its focus
133
What is the iris?
A colored vascular layer of the eye
134
What 2 groups of smooth muscles change the size of the pupil?
Constrictor muscles and dilator muscles
135
Why does the pupil remain black?
Because the light entering the pupil is all absorbed by the black choroid or the light absorbing cells of the retina
136
Why does our pupil appear red if a light shines directing into it?
Because of the blood vessels on the surface of the retina
137
What is the retina?
The inner layer of the eye and it covers the back of the eye but only extends forward to the ciliary body connecting to the lens
138
What is the macula?
A 4mm yellowish spot on the back of the eye near the center of the retina
139
What is the fovea?
The small pit in the center of the and the spot with the densest collection of photoreceptors neurons
140
What is macular degeneration?
Vision loss due to damage to the macula
141
What is the optic disk?
Known as the blind spot and is the opening in the retina and blood vessel that serve the retina enter and exit the optic disk
142
What is the lens made up of?
epithelial cells
143
The epithelial cells in the center of the lens are transparent because?
they have lost their nuclei and organelles and mostly consist of cytoplasm and the colorless proteins called crystallines
144
Is the lens vascular of avascular?
avascular
145
What causes cataracts?
When the transparent fiber cell of the lens get cloudy due to a build up of proteins other than crystallines
146
When the ciliary body muscles relax, the lens is _____?
flatter
147
When the ciliary body muscles contract, the lens is _____?
rounder
148
What is accommodation?
Bending incoming light
149
The retina, moving from most interior to exterior consists of:
1. a layer of axons that are traveling to the optic disc where they can exit the eye to the brain
2. Followed by 3 layers of neurons
3. Ending with a single layer of pigmented epithelial cells
150
What are the 3 layers of neurons after the layer of axons from outermost to innermost?
Ganglion neurons, bipolar neurons , photoreceptor neurons
151
What is the outermost layer of neurons called and what is their role?
ganglion neurons
152
What are ganglion neurons role?
They send action potentials out of the eye via the optic nerve to the brain
153
What is the middle layer of neurons called?
Bipolar neurons
154
What is bipolar neurons role?
They connect to the outer most and inner most neurons
155
What is the innermost layer of neurons called?
photoreceptor neurons
156
What are the photoreceptor neurons role?
They absorb light and initiate action potentials that will travel out of the eye via the optic nerve
157
There are two types of photoreceptor neurons what are they?
cones and rods
158
Describe how cones look?
they taper to a blunt end
159
Describe how rods look?
they end in an elogated cylinder
160
Rods are responsible for what type of vision?
noncolor vision and vision under reduced light (r=reduced light)
161
Cones are responsible for what type of vision?
color vision and clarity (c=color and clarity)
162
Why is the most acute vision in the center of the eye's field of view?
The light hits the fovea where the cones provide most clarity
163
Each eye has how many rods and cones?
120 million rods and 6 million cones
164
The fovea in the center of the macula has how many cones and rods?
35,000 cones and no rods
165
The neural pathway from the eyes to the brain goes:
1. from the photoreceptor neuron
2. to bipolar neuron
3. to ganglionic neuron\
4. down optic nerve (through the optic disk out of the ey)
166
The "rod" like end of rods contain about 700 membrane bound disks and throughout those disks in the rods are molecules _______?
rhodopsin
167
Rhodopsin consists of what?
1. An opsin protein
| 2. The molecule retinal
168
Since rob cells cannot synthesize retinal, how can we obtain retinal?
Through our diet in the form of vitamin A. The cell can convert vitamin A to retinal
169
The "cone" part of the cones contain membrane folds that contain large amounts of _____?
iodopsin
170
Iodopsin consists of what?
1. an opsin protein
| 2. The molecule retinal
171
What do rod and cone cells do in the absence of light?
They are continually and spontaneously generating action potentials and releasing glutamate as a neurotransmitter
172
What is glutamate?
It is an inhibitory neurotransmitter for the bipolar neurons, so it causes them not to fire and the ganglionic neurons do not fire and no action potentials are sent down the optic nerve
173
How do rods allow us to see in the dark?
The rods are absorbing what little there is, since rods don't respond to color in dim light everything looks greyish and uncolored
174
What is color blindness a result of?
A result of dysfunction in one or more of the iodopsins that detect colored light in cons
175
Sound is caused by?
the vibration of air molecules
176
What is the cochleas role?
It is responsible for both hearing and balance
177
What is sound attenuation reflex?
When loud sounds cause small muscles attached to the auditory ossicles to contract reflexively to prevent the auditory ossicle from vibrating excessively protecting the middle and inner ear from damage
178
The cochlea is a coiled tube with its interior divided by membranes in how many fluid filled chambers?
3
179
The two outer chambers of the cochlea are filled with a liquid called?
perilymph
180
The central chamber of the cochlea is filled with a liquid called?
endolymph
181
One of the membranes separating the middle chamber of the cochlea from the other two has specialized neurons called _____ that project into the endolymph?
hair cells
182
What is stereocilia?
projections from hair cells into the endolymph and the stereocilia increase in length from one side of the hair cell to the other
183
What happens if stereocilia on a hair cell neuron are bent for long enough?
An action potential is triggered in the hair cell neuron and it releases neurotransmitter. this triggers the neurons synapsed with the hair cell to fire sending signals to the brain that will be interpreted as sound
184
What are the 2 types of balance?
static balance and dynamic balance
185
What is static balance?
Which evaluates the position of the head relative to gravity (up vs. down)
186
What is dynamic balance?
Which evaluates changes in the head's direction (other than up vs. down) and how fast its direction is changing
187
What are the 2 organs of balance that are in the inner ear?
Vestibule and semicircular canals
188
Which inner ear organ is responsible for static balance?
The vestibule
189
Which inner ear organ is responsible for dynamic balance?
Semicircular canals
190
What are otoliths?
Crystals of calcium carbonate and proteins
191
What do the otolith crystals do?
Help shift or slide the entire otolithic membrane over the hair cells when gravity pulls on them
192
Dynamic balance is due to the _______?
semicircular canals
193
What are the 3 semicircular canals names?
frontal plane
transverse plane
sagittal plane
194
Where is the crista empullaris?
At the base of all 3 semicircular canals it is a modified section of epithelial cells lining the canal interior
195
What is the cupula membrane?
It is this gelatinous covering layer in the crista ampullaris
196
What causes motion sickness?
When the semicircular canal (or vestibule) sends signals to the brain that movement is occurring but the eyes send signals to the brain that movement is not occurring (because the car, or boat, or swing around you is not moving relative to you.)
197
What is the endocrine system?
The network of ductless glands in the body that synthesize and secrete hormones to act as chemical messengers to control metabolism, structures, and functions in target organs, tissues, and cells.
198
Then endocrine system sends out commands in what form?
the form of hormone molecules
199
What do both the endocrine and nervous system do the same?
Both respond to stimuli.
Both are involved in maintaining body homeostasis.
Both use chemical messengers to produce changes in targets.
Both use feedback loops to initiate and end their responses.
200
What is the main difference between the endocrine system and the nervous system?
The time fame of their actions. The endocrine system is slower to have affect but their effects are longer lasting, while the nervous system will have immediate effects but they are short term.
201
What are the 3 categories most hormones produced by the endocrine glands fit into?
derivatives of amino acids, peptides, or steroids
202
Which two hormones are hydrophobic?
steroids are lipids and SOME amino acids derivatives are hydrophobic and are not very soluble in water
203
How do insoluble hormones get to their target tissues and cells?
They bind to transport proteins in the blood which is soluble which take them there. There are different transport proteins for each different insoluble hormone
204
Each target cell must have a _____ for the hormone to bind and begin the changes that result in the target cell?
receptor
205
Where are receptors mostly but not always located on a target cell?
the plasma membrane
206
If a particular cell is a target for a hormone, what will it always have?
A receptor for that hormone.
207
Why are hormones called signal molecules?
Because by binding to a cellular receptor protein they are signaling a specific sequence of events to begin
208
After a hormone binds to its cellular receptor, hormone-receptor complex initiates a sequence of events called a _____?
Signal transduction pathway
209
What are the 6 major endocrine glands?
1. Hypothalamus pituitary gland complex
2. pineal gland
3. thyroid gland
4. parathyroid gland
5. adrenal glands
6. pancreas
210
What are the organs that have secondary endocrine functions?
1. gonads
2. intestines
3. heart
4. adipose
5. kidneys
6. bones
211
Which organ is considered a secondary endocrine gland by some physiologists, but as a primary one by others?
The gonads
212
The hypothalamus is apart of the ______ in the brain?
diencephalon
213
The hormones released by the pituitary gland are controlled and regulated by the _____?
hypothalamus
214
The pituitary gland hangs down from the hypothalamus by a stalk called the _____?
pituitary stalk
215
The pituitary gland is divided into what 2 lobes?
1. the anterior lobe
| 2. the posterior lobe
216
What is another name for the entire pituitary gland?
Hypophysis
217
What is the command center of the endocrine system?
hypothalamus pituitary gland complex
218
The pituitary stalk and the two lobes are surrounded by networks of _____?
capillaries
219
How are the 2 lobes of the pituitary gland distinct from each other?
1. in how they interact with the hypothalamus
2. in what cells release the hormones
3. in the effects of the hormones they release
220
In the anterior pituitary, epithelial cells release the hormones but in the posterior pituitary, _____ release the hormones?
neurons that start in the hypothalamus
221
The anterior pituitary hormones target both _____ and _____?
other endocrine organs and specific tissues
222
The posterior pituitary hormones only target _____?
specific tissues
223
`What are the two hormones produced by the posterior pituitary gland?
ADH (antidiuretic hormone) and Oxytocin
224
_____ hormone is released when osmoreceptors in the hypothalamus detect too many solutes n the blood (the blood in to concentrated)?
Antidiuretic hormone or ADH
225
What effect does ADH have on blood?
It makes it more dilute
226
When ADH is released it binds to the receptors in the plasma membrane of kidneys and it causes the kidney to what?
The kidney to release more H2O back into the blood diluting it
227
What doe oxytocin do in females?
1. induces uterine contractions during birth
2. Induces contraction of milk ducts during breast feeding
3. facilitates pair bonding during physical interactions
228
What does oxytocin do in males?
1. causes contraction of vas deferens in penis during ejaculation
2. facilitates pair bonding during physical interactions
229
What are the hormones released by the hypothalamus that target the anterior pituitary called?
Releasing hormones
230
How many releasing hormones does the hypothalamus secrete?
5
231
How many hormones does the anterior pituitary secrete in response to the 5 hypothalamus releasing hormones/
6
232
The hypothalamus secretes 2 inhibiting hormones that induce the anterior pituitary to stop secreting which two specific hormones in response?
growth hormone and prolactin
233
What are the 6 major hormones produced by the anterior pituitary?
1. Follicle stimulating hormone (FSH)
2. Luteinizing hormone (LH)
3. Thyroid stimulating hormone (TSH)
4. Andrenocorticotropic hormone (ACTH)
5. Growth Hormone (GH)
6. Prolactin (PRL)
234
Which anterior pituitary hormones are tropic?
1. Follicle stimulating hormone (FSH)
2. Luteinizing hormone (LH)
3. Thyroid stimulating hormone (TSH)
4. Andrenocorticotropic hormone (ACTH)
235
Which anterior pituitary hormones are tropic and regular?
1. growth hormone
236
Which anterior pituitary hormone is just regular?
prolactin
237
What do tropic hormones target?
Other endocrine glands
238
What is a tropic hormone?
Hormones that target other endocrine glands, inducing them to secrete their own hormones
239
What is a regular hormone?
A regular hormone induces metabolic and genetic changes in its target cells
