Tissues Flashcards
Later on add some cards about muscle contraction from first year slides
1
Q
multi-cellular human body cells do not…
A
… operate independently
2
Q
what do multi-cellular cells form?
A
They form tight communities that work together and interact with others.
3
Q
Define tissue
A
an aggregate of cells usually of a particular kind together with their intercellular substance that form one of the structural materials of a plant or animal.
4
Q
define histology
A
a branch of anatomy that deals with the minute structure of animal and plant tissues as discernible with the microscope.
5
Q
Individual body cells are…
A
…specialised.
6
Q
Specialised body cells each perform a …
A
… specific function
7
Q
Specialised cells have an […] advantage.
A
Specialised cells have an evolutionary advantage.
8
Q
Specialised cells allows what?
A
Allows sophistication of function and division of labour.
9
Q
Why do specialsed cells have an evolutionary advantage?
A
Because our bodily functions become more sophisticated as we differentiate our cells.
10
Q
WHat are the four primary types of tissue?
A
- Epithelial (covering role)
- Connective (supportive role)
- Muscle (movement role)
- Nervous (control role)
11
Q
WHat are tissues organised into?
A
Tissues are organised into organs,
which often contain all four tissue
types.
12
Q
Where do epithelial cells cover?
A
covers cavities from outside and inside
13
Q
WHat does the arrangement of tissues determine?
A
the organs structure and capabilities.
14
Q
What are the 5 types of epithelial cell?
A
- Squamous
- Cuboidal
- Columnar
- Ciliated
- Glandular
15
Q
SHape of squamos cell?
A
thin and flat
16
Q
3 types of muscular cell?
A
- Unstriated
- Striated
- Cardiac
17
Q
what are the 3 types of connective tissue?
A
- Proper tissue
- Skeletal tissue
- Vascular tissue
18
Q
Function of epithelial tissue?
A
Secretion / absorption
19
Q
function of epithelial tissue
A
secretion / absorption
20
Q
what is the function of connective tissue?
A
support
21
Q
what is the function of muscle tissue?
A
Movement (Contraction / relaxation)
22
Q
A
23
Q
What is embryogenesis?
A
embryonic development
24
Q
Describe embryogenesis / embryonic development.
A
process by which the embryo forms
and develops (early stages of prenatal development). Embryogenesis starts with the
fertilization of the egg cell (ovum) by a mature motile male sex cell (spermatozoon)
25
what are the 3 germ layers?
1) Endoderm
2) Mesoderm
3) Ectoderm
26
what is the blue layer?
ectoderm
27
What is the innermost germ layer?
endoderm
28
what is the outermost germ layer?
ectoderm
29
What is the middle germ layer?
mesoderm
30
What organs does the endoderm form?
gut, liver, lungs.
31
what organs does the mesoderm form?
skeleton, muscle, kidney, heart, blood.
32
What organs does the ectoderm form?
skin, nervous system.
33
Epithelial tissue is also known as what?
epithelium
34
What is Epithelial Tissue?
Epithelial tissue (or an epithelium) is a sheet of cells that covers a body surface or lines a body cavity.
35
what are the epithelial roles?
- Protection
- Absorption
- Sensory reception
- Secretion
- Excretion
- Filtration
36
Epithelial tissue occurs as either:
1) Covering and lining epithelium
2) Glandular eppithelium
37
What is the covering and lining epithelium?
- Outer layer of skin
- Lines the cavities of the cardiovascular, digestive, and respiratory system
- Covers the walls and organs of the ventral body cavity.
38
What is the function of the glandular epithelium?
Forms the glands of the body.
39
what is meant by interface tissue?
Epithelia form boundaries between different environments.
40
nearly all substances received/given off by the body must...
...pass through an epithelium
41
What are two characteristics of the apical surface?
- Direction (orientation) + polarity
- Upper free surface exposed to the body exterior or the cavity of an internal organ.
42
What are some examples of apical surfaces?
1) Skin
2) Cornea
43
What does apical mean?
apical means top / outside / external.
44
What does basal mean?
basal means bottom / pointing inside / internal surface
45
Apical surfaces can be...
... smooth or possess microvilli
cornea = smooth
small intestine = villi
46
what are microvilli?
finger like extensions of the plasma membrane.
47
Cells near apical surface differ in...
... structure & function from those near basal surface.
48
the basal surface is the...
...lower attached surface
49
What is the Basal lamina?
non-cellular adhesive sheet consisting of glycoproteins secreted by epithelial cells.
50
the basal surface contains...
...collagen fibres
51
the basal surface contains collagen fibres that act as a ...
... selective filter / scaffold along which epithelial cells can migrate.
52
Whats an example of a basal surface?
corneal epithelium
53
epithelial cells sit...
... close together to form continuous sheets.
54
Adjacent (epithelial) cells are bound together by...
... three main types of lateral contacts.
55
why must epithelial sit close together in the correct positions?
large gaps = things can leak through / tissue cannot form its function EG = a cut in the skin. So epithelial cells have to sit close together.
56
What are tight junctions?
interlocking integral membrane proteins that prevent molecules from passing through the intercellular space.
57
examples of tight junctions?
skin (physcial barrier/protection
small intestine (absorption)
58
What are desmosomes?
Anchoring junctions and help to form a tension reducing network of fibres
59
Desmosomes work together with...
...tight junctions
60
What are the function of desmosomes?
* Ensure that proteins remain in the apical region of the plasma membrane
* Prevent rotation
* Maintaining the polarity of the epithelial cell
61
What are gap junctions?
communicating junction between cells, where hollow transmembrane proteins (connexons) allow small molecules to pass between cells.
62
What are connexons?
Assembly of six proteins called connexins.
63
Connexins vary in their...
...selectivity
64
What passes through gap junctions?
Different ions, sugars etc. pass through these waterfilled channels
65
Epithelial sheets are supported by...
...connective tissue
66
All epithelial sheets rest upon...
...connective tissue
67
the reticular lamina likes just beneath the...
...basal lamina
68
what does the reticular lamina consist of?
It consists of extra-cellular material containing a fine network of collagen protein fibres
69
reticular = ?
reticular = net-like
70
Together, the basal lamina and reticular lamina form the...
... basement membrane, which reinforces the epithelial sheet.
71
What do simple epithelia consist of?
consist of a single layer of cells, typically found where absorption, secretion and filtration occur.
72
What does stratified epithelia consist of?
consist of two or more cellular layers, stacked on top of one another. Typical in high-abrasion areas, e.g. mouth, skin surface.
73
Height of epithelial cells?
can vary in height
74
THe three common shapes of epithelial cells?
1) Squamous cells
2) Cuboidal cells
3) Columnar cells.
75
what shape are cuboidal cells
box like.
as tall as they are wide.
76
what shape are squamous cells?
flattened cells
77
what shape are columnar cells?
tall column shaped cells.
78
what shape are simple epithelia?
In simple epithelia, all cells are usually the same shape.
79
shapes of stratified epithelia?
In stratified epithelia, cell shapes usually differ among the different cell layers.
80
What are stratified epithelia named according to?
stratified epithelia are named according to cells in the apical layer. e.g. stratified squamous, stratified columnar.
81
Describe the Simple Epithelium of the digestive system.
Single cell layer involved primarily in absorption, secretion and filtration
82
What is simple cuboidal epithelium involved in in the digestive system?
Involved in secretion and absorption
83
What do Simple cuboidal epithelium form?
They form the walls of the smallest ducts or glands.
84
What does simple columnar epithelium line in the digestive system?
Line the digestive tract from stomach to
rectum and are most associated with
absorption and secretion
85
What are the two types of Simple columnar epithelium in the digestive system?
1) Dense microvilli on apical surface of absorptive cells.
2) Secretory cells that produce mucous.
86
What is the most widespread of the stratified epithelia?
stratified squamous epithelium
87
Examples of non-keratinised stratified epithelium?
Oesophagus, mouth, skin, cornea.
88
what do non-keratinised stratified epithelium require to prevent drying?
Require secretions to prevent drying
89
What are some examples of keratinised stratified Epithelium?
- Palms and soles
- Resistant to abrasion
90
What is keratinised Stratified Epithelium resistant to?
resistant to abrasion.
91
As the top layer of Stratified Epithelium is worn away, what happens?
Replaced by basal cells beneath
92
Stratified cuboidal epithelium is...
...rare in the body
93
Where is Stratified cuboidal epithelium found?
found in the ducts of some larger glands including the pancreatic duct.
94
Stratified columnar epithelium is ...
....rare in the body
95
where is Stratified columnar epithelium found?
found in the pharynx / salivary glands, urethra
96
Only the [...] layer is columnar
Only the apical layer is columnar
97
There are several different kinds of connective tissue, all originating from ...
... a derivative of mesoderm called mesenchyme.
98
What is mesenchyme?
connective tissue found mostly during embryonic development. Composed mainly of
ground substance with few cells and fibres.
99
What are the main connective tissues?
1. Loose connective tissue
2. Dense connective tissue
3. Adipose tissue
4. Lymphoid tissue
5. Cartilage
6. Bone
7. Blood and blood-forming tissue
100
Connective tissue are the most...
...abundant and widespread primary tissue in the body
101
Major functions of connective tissue?
Binding and support
Protection
Insulation
Transportation (as blood)
102
What are the main characteristics of connective tissue?
1) Common Origin
2) Degrees of vascularity
3) Extracellular matrix
103
Where do connective tissue originate from?
All arise from mesenchyme undifferentiated embryonic tissue.
Example: Most blood cells are produced by the mesenchymal tissue in the bone marrow.
104
Some connective tissues receive a ...
... poor blood supply
105
Some connective tissues receive a poor blood supply.
Whereas others are...
...richly supplied by blood vessels
106
What do connective tissues contain?
they contain a largely non living extracellular matrix, some are able to bear weight, and withstand great tension and endure trauma.
107
3 main structural elements of connective tissue?
1) ground substance
2) fibres
3) cells
108
what do ground substance and fibres make up?
make up the extracellular matrix.
109
the extracellular matrix fills what?
The extracellular matrix fills the spaces between cells and binds cells and tissues together.
110
connective tissue are very...
... diverse
111
why are connective tissues very diverse?
delicate packaging around organs to the rope like tendons and ligaments.
112
what is Ground substance?
- Unstructured material (liquid, solid, or gel)
- Fills the space between cells
- Contains the fibres.
113
what is ground substance composed of?
interstitial fluid
114
what is exchanged in ground substances?
water, ions, small solutes.
(glycosaminoglycans (GAGs), proteoglycans, cell adhesion proteins)
115
Ground substance holds a ...
... large amount of fluid.
116
What does ground substance function as?
Functions as a molecular sieve through which nutrients and other dissolved substances diffuse between blood capillaries and cells.
117
what are the 3 main types of fibres?
1) Collagen
2) Elastic fibres
3) Reticular fibres.
118
what is collagen constructed from?
constructed from the protein collagen which spontaneously assemble into cross-linked fibrils that form bundles of fibres.
119
what vitamin is required for collagen production?
vitamin C
120
What are elastic fibres?
long thin fibres that form branching
networks.
121
What protein do elastic fibres contain?
Contain the protein elastin that stretches
and recoils
122
What are reticular fibres?
short, fine, collagenous fibres that branch extensively forming delicate networks that surround small blood vessels
123
where are reticular fibres found?
found in the basement membrane of epithelial cells.
124
Each connective tissue type has a ...
...fundamental cell type that exists in immature and mature forms.
125
How are undifferentiated cells indicated?
Undifferentiated cells are indicated by the suffix - blast (forming)
126
what does blast mean?
forming
127
blast cells are actively...
...mitotic cells.
128
blast cells are actively mitotic cells that secrete what?
secrete the ground substance and the fibres characteristic of their particular matrix.
129
what are the primary blast cell types of connective tissue?
1) Bone = osteoblast
2) Connective tissue proper = fibroblast
3) cartilage = chondroblast
130
what is the odd one out?
Blood: Hematopoietic stem cell
131
why is blood the odd one out?
because this cell does not reside in its tissue (blood) and does not contribute to the
fluid matrix (plasma).
132
Once they synthesize the matrix, blast cells assume their...
...less active mature mode (indicated by the suffix -cyte: fibrocyte, chondrocytes, osteocytes).
133
What do mature cells maintain?
the matrix.
134
The mature cells maintain the matrix, but what happens if some trauma occurs?
they revert to their blast state to repair and regenerate the matrix.
135
Other than blast, and cytes, what other cells are found in the matrix?
- Adipocytes: lipid storage
- Wandering/mobile cells (migrate from blood stream)
136
Where do wandering/mobile cells migrate from?
from the blood stream.
137
What are some examples of wandering/mobile cells?
White blood cells
eg: Neutrophils
Eosinophils
Lymphocytes
Mast Cells (granulocyte mastocytes): detect
microorganisms and initiate local inflammatory
responses.
Macrophages: phagocytotic cells that ‘eat’
foreign material, including dead tissue cells
138
What do mast cells (granulocyte mastocytes) do?
detect microorganisms and initiate local inflammatory responses.
139
what are mast cells also known as?
granulocyte mastocytes
140
what is the function of macrophages?
phagocytotic cells that eat foreign material, including dead tissue cells.
141
what is areolar tissue?
Loose arrangement of fibres that provide a reservoir for water and salts for
surrounding body tissues (has a gel-like consistency) -> interstitial fluid
142
Cells obtain their nutrients and release their wastes into ...
...interstitial fluid
143
what kind of consistency does interstitial fluid have?
gel-like consistency
144
What does the interstitial fluid contain?
Contains fibroblasts, macrophages, adipose cells (either singly or in clusters) and
occasional mast cells.
145
What is areolar connective tissue found as in the digestive system?
Found as the lamina propria of mucus membrane epithelia.
146
147
areolar tissue is the most...
...widespread tissue in the body.
148
Why can areolar tissue be difficult to ID?
because it doesn't look like very much under a regular light microscope. When you first see it, it doesn't look like any of the images in the book or on a wall chart.
149
Why is it difficult to see areolar tissue under a light microscope?
areolar tissue is mostly water with some dispersed cells, fibrous proteins, and fat cells.
150
what is embryogenesis also known as?
embryonic development.
151
What are the three parts of the ectoderm?
1) Surface ectoderm
2) Neural crest
3) Neural tube
152
What does the surface ectoderm form?
- Epidermis (skin)
- Hair
- Nails
- Sebaceous glands
- Olfactory epithelium
- Mouth epithelium (anterior pituitry + tooth enamel + cheek epithelium)
- Lens, cornea
153
What does the neural crest form?
- Peripheral nervous system (Schwann cells + neuroglial cells + sympathetic nervous system + parasympathetic nervous system)
- Adrenal medulla
- Melanocytes
- Facial cartilage
- Dentine of teeth
154
What does the neural tube form?
- Brain
- Neural pituitary
- Spinal cord
- Motor neurons
- Retina
155
important slide?
slide 54 - must learn.
156
three overlapping functions of nervous tissue?
1) Sensory input
2) Integration
3) Motor output
157
What does sensory input of nervous system do?
monitor changes via sensory receptors
158
What does integration of nervous tissue do?
processes and interprets sensory input
159
What does motor input of nervous tissue do?
initiates a response via effector organs (muscles and glands).
160
What two parts does the nervous system consist of?
Central Nervous System
(CNS): brain and spinal cord
Peripheral Nervous System (PNS):
consists of bundles of nerves that
extend from the brain and spinal cord.
161
what is the peripheral nervous system further divided into?
1) Sensory (afferent) division
2) Motor (efferent) division
162
What is the function of the sensory (afferent) division?
conveys impulses to the CNS via somatic
(skeletal muscles / joints) or visceral (organs) afferent fibres.
163
What is the function of the motor (efferent) division?
transmits pulse from the CNS to effector organs
164
What two parts does the motor (efferent) division consist of?
1) Somatic nervous system (voluntary nervous system)
2) Autonomic nervous system (ANS – involuntary nervous system)
165
What is the function of the Somatic nervous system (voluntary nervous system)?
allows conscious control of skeletal muscle
166
What is the function of the Autonomic nervous system (ANS – involuntary nervous system)?
Visceral motor fibres that regulate the activity of smooth muscles, cardiac muscle and glands.
167
What are the two subdivisions of the autonomic nervous system?
Sympathetic and parasympathetic nervous systems - typically work in opposition to each other - if one stimulates, the other inhibits.
168
What is the parasympathetic division?
- The "Resting and Digesting” system
- Keeps body energy use as low as possible as it directs “housekeeping” activities like digestion and elimination of faeces and urine.
169
What does the parasympathetic nervous system stimulate?
- Stimulates watery saliva
- Increases motility (peristalsis)
- Increases secretion by digestive organs, relaxes sphincters to allow movement of foodstuffs.
170
What does the sympathetic division do?
- The “Fight or Flight” system
- Stimulates thick, viscous saliva
- Decreases activity of the digestive tract
- Decreases activity of glands and muscles of digestive system and constricts sphincters
171
What do dendrites provide?
Dendrites provide an enormous surface area for receiving signals from other neurons.
172
What is the function of dendrites?
They convey signals toward the cell body
173
What are axons?
- Axons are a single process that originates from axon hillock and ends at synaptic knob.
174
What is the function of axons?
- Transmits impulses AWAY from the cell body.
175
What do nerve impulses release?
Nerve impulses release neurotransmitters into the extracellular space.
176
What is the myelin sheath?
Myelinated fibres conduct nerve impulses rapidly.
177
In which part of the nervous system are oligodendrocytes found?
CNS
178
In which part of the PNS are Schwann cells found?
PNS
179
the myelin sheath wraps itself around what?
Wrap themselves around nerve fibres
180
What does the myelin sheath squeeze out?
Squeezing out their cytoplasm until many concentric layers of plasma membrane enclose the axon.
181
What is a major advantage of the myelin sheath?
Exceptionally good electrical insulation
182
Gaps in between adjacent Schwann cells
are called...
... nodes of Ranvier
183
What are nodes of ranvier important for?
Important in fast impulse transmission.
184
Where does myelination occur?
Myelination in the central and peripheral nervous systems.
185
Describe myelination in the peripheral nervous system.
In the peripheral nervous system, Schwan cells wrap themselves around the axon.
186
Describe myelination in the central nervous system.
in the central nervous system, myelination is
accomplished by the processes of
oligodendrocytes.
187
In the peripheral nervous system, Schwan cells wrap themselves around the axon; in the central nervous system, myelination is
accomplished by the processes of oligodendrocytes.
What does the mechanism of this wrapping entail?
It entails the production of an enormous membrane complex.
188
What is the membrane potential called when the nerve or muscle cell is at rest?
resting membrane potential
189
What is the number of resting membrane potential?
-70 millivolts (mV)
190
When does a typical neuron fire an action potential?
When the depolarization reaches about -55 mV
191
what crosses the neuron membrane very quickly?
ions cross the neuron membrane very quickly.
192
What causes sodium channels to open?
a stimulus.
193
What do plasma membranes contain a variety of?
proteins.
194
Plasma membrane contain a variety of proteins that act as...
...ion channels - each selective for a particular ion.
195
Some channels are always...
...open
196
What are the "always open" channels called?
non-gated
197
Some channels are always open (non-gated), where as others...
...open and close due to:
- Chemically / ligand-gated
- Voltage-gated
- Mechanically-gated channels.
198
Describe chemically / ligand-gated?
open on binding of a suitable chemical stimulant
199
Describe voltage-gated?
open and close in response to changes in membrane potential
200
Describe Mechanically-gated channels?
open in response to physical deformation (pressure)
201
What is found at the end of an axon?
the synaptic knob
202
What is the synaptic knob specilaised to do?
to allow the flow of ions between neurons.
203
What does the synaptic knob contain?
contains vesicles which contain neurotransmitters
204
What is the synaptic cleft?
a fluid filled space between two neurons
205
How wide is the synaptic cleft?
25-50 nm wide
206
Where in the synapse is a neurotransmitter receptor region found?
on the membrane of the dendrite of the postsynaptic neuron.
207
Describe the process of information transfer across chemical synapses.
1) The action potentials arrive at axon terminal
2) Voltage-gated Ca2+ channels become opened
3) Ca2+ enters the cell
4) Ca2+ signals to synaptic vesicles
5) Vesicles move to the membrane
6) Docked vesicles release neurotransmitter by exocytosis.
7) Neurotransmitter diffuses across the synaptic cleft and binds to receptors.
8) Binding of neurotransmitters opens ion channels resulting in graded potentials
9) Neurotransmitter effects are terminated.
208
Some neurotransmitters have a ...
... direct action or indirect action
209
examples of direct action of neurotransmitters?
Acetylcholine Receptor. Binding of Acetylcholine, to Ach receptor opens channel through which Na+
ions can pass into the cell.
210
Examples of indirect action?
G-protein coupled receptor. Binding of neurotransmitter results in the activation of a G-protein that initiate widespread metabolic changes
211
What do G-protein coupled receptors do?
These receptors control second messengers (e.g. cAMP) that regulate ion channels/enzyme cascades.
212
Look at slide 70
213
Describe the two neuron chain
The first cell body neuron (pre-ganglionic neuron) resides in the brain or in the spinal chord. The pre-ganglionic axox (of the pre-ganglionic neuron) synapses with a second motor neuron (the ganglionic neuron). The post-ganglionic axon then connects to the effector organ.
214
What is a sarcomere?
the units of contraction
215
What are the three types of muscle tissue?
1) Skeletal muscle
2) Cardiac muscle
3) Smooth muscle
216
What type of muscle tissue is voluntary muscle?
Skeletal muscle
217
What type of muscle tissue is involuntary?
Smooth muscle
218
What is skeletal muscle?
Organs that attach and cover the bony
skeleton
219
Function of skeletal muscles?
moves arms/legs etc
220
Where does cardiac muscle occur?
Occurs only in the heart.
221
Is cardiac muscle voluntary or involuntary?
involuntary
222
Function of cardiac muscle?
Constitutes the bulk of the heart walls – not voluntary.
223
Where is smooth muscle found?
Found in the walls of hollow visceral organs.
224
What is the function of smooth muscle?
Used in the walls of hollow visceral organs to force liquids and other substances through internal body channels.
225
Where is smooth muscle found?
Bladder, intestines, reproductive system, arteries, stomach.
226
function of the presynaptic receptors?
regulate the release of neurotransmitters in the CNS and PNS
227
What does each muscle fibre contain?
myofibrils which run parallel to its length
228
Each muscle fibre contains myofibrils that run parallel to its length.
The contractile elements (sarcomeres) contain even smaller structures called ...
... myofilaments
229
What are myofilaments made up of?
* Thick filaments (myosin)
* Thin filaments (actin, tropomyosin and troponin)
230
What are thick filaments made up of?
myosin
231
What are thin filaments made up of?
actin, tropomyosin, and troponin.
232
What does sarcolemma resemble?
resembles plasma membrane.
233
What does sarcolemma do?
Acts as the dynamic outer membrane
of the muscle cell.
Sarcolemma also allows calcium uptake.
234
Where is the sarcoplasmic reticulum?
in the sarcoplasm
235
What is the sarcoplasmic reticulum?
A modified endoplasmic reticulum that surrounds each myofibril.
236
How does the sarcoplasmic reticulum run?
Running longitudinally and communicating at H-zone
237
What is stored in the sarcoplasmic reticulum?
calcium storage
238
What is Ca2+ ?
calcium ions
239
Describe the process that occurs at the neuromuscular junction
Calcium ions (Ca2+) causes release of acetylcholine, ACh then binds to nicotinic acetylcholine receptors (nAChRs) on the cell membrane of muscle fibre (carcolemma). Binding of ACh to nAChRs causes depolarization, resulting in muscle contraction.
240
Electrical impulses from nerves travel
along the sarcolemma and into...
... T-tubules which reach deeply into muscle cell and to every sarcomere
241
What are T-tubules?
At each A band / I band junction the sarcolemma of the
muscle cell protrudes deep into the cell interior forming elongated tubes called T-tubules.
242
Role of electrical impulses in skeletal muscle contraction?
These impulses
signal the release of
calcium, causing
muscle fibre contraction at the same time.
243
During contraction, what slides past eachother?
the thin filaments slide past the thick ones so that the actin
and myosin overlap to a greater degree.
244
What do myosin heads latch on to?
Myosin heads latch onto myosin-binding sites on the actin – cross bridges.
245
Myosin heads latch onto myosin-binding sites on the actin.
What does this form?
cross bridges
246
During contraction, the thin filaments slide past the thick ones so that the actin and myosin overlap to a greater degree.
Myosin heads latch onto myosin-binding sites on the actin – cross bridges.
Sliding begins and these heads...
... detach and reattach several times during contraction
247
During contraction, the thin filaments slide past the thick ones so that the actin and myosin overlap to a greater degree.
Myosin heads latch onto myosin-binding sites on the actin – cross bridges.
Sliding begins and these heads detach and reattach several times during contraction.
Then the muscle cell shortens. How does this happen?
Z- discs are pulled toward the M line and I bands shorten
248
What is the shape and size of muscle fibres?
Smooth muscle fibres are spindle shaped cells of variable size
249
Location of nucleus in smooth muscle fibres?
a centrally located nucleus
250
Describe the longitudinal layer of smooth muscle sheets?
run parallel to the long axis of the digestive tract. On
contraction this shortens or dilates the organ.
251
Describe the circular layer of smooth muscle sheets?
run around the circumference of the organ.
On contraction this constricts the lumen of the organ causing it to elongate.
252
What does smooth muscle of the digestive tract contain?
- a small amount of endomysium (fine areolar connective tissue)
- blood vessels / nerves between smooth muscle fibres.
253
What are Varicosities?
release neurotransmitter into a wide synaptic cleft (diffuse junctions)
over several smooth muscle cells.
254
Unlike skeletal muscle, smooth muscle has no...
...striations (hence smooth muscle) and no sarcomeres.
255
Smooth muscle fibres contain intertwining...
...thick / thin filaments, but are much longer than skeletal muscle.
256
In smooth muscle, the thick filaments have...
...myosin heads along their entire length.
257
Compared to skeletal muscle, smooth muscle has fewer...
...thick filaments.
258
What is the difference between the ratio of thick to thin filaments in smooth muscle and skeletal muscle.
ratio of thick to thin is 1:13 in smooth muscle compared to 1:2 for skeletal muscle
259
In the thin filaments of smooth muscle, there are no...
... troponin complexes
260
How are thick and thin filaments arranged in smooth muscle?
Thick and thin filaments are arranged diagonally
around the long axis of the cell
261
Describe Intermediate filament-dense
body network found in smooth muscle?
lattice arrangement of non contractile
intermediate filaments attached
to dense bodies.
262
smooth muscle is 30 times longer to...
... contract and relax than skeletal muscle, at 1 % of the energy cost.
263
Smooth muscle: 30 times longer to contract and relax than skeletal muscle, at 1 % of the energy cost.
This efficiency allows smooth muscle in the intestines to...
... maintain 'tone' without fatigue.
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How is smooth muscle regulated?
By action potentials or graded (local) potentials, releasing neurotransmitters that stimulate or inhibit a group of smooth muscle cells.
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Some smooth muscles do not have a nerve supply and instead ...
... depolarize spontaneously or in response to chemical stimuli linked to G-protein receptors.
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Some smooth muscles do not have a nerve supply and instead depolarize
spontaneously or in response to chemical stimuli linked to G-protein receptors
Can you give an example?
Gastrin stimulates smooth muscle cells of the stomach so that it can churn
foodstuffs efficiently
