Muscle (& epithelia) Flashcards
(128 cards)
1
Q
What are the 4 basic types of tissue?
A
- Epithelia
- Muscular
- Nervous
- Connective tissue
2
Q
Where are epithelia found (vaguely)?
A
As a boundary between controlled internal environment & uncontrolled external environment
3
Q
What are the 3 germ layers that epithelia can develop from?
A
Endoderm - e.g. GI lining
Mesoderm - e.g. Lining of CV system
Ectoderm - e.g. epidermis
4
Q
What is an example of an area of high abrasion where epithelia is found?
A
Skin
5
Q
Why is the purpose of epithelia in the lungs?
A
Aids with diffusion in the lungs
6
Q
What is the purpose of epithelia in the small intestine?
A
Aids with absorption
7
Q
Why is epithelia described as a dynamic barrier?
A
It is able to import & expel substance, sometimes against concentration gradients.
8
Q
What connects epithelial cells and creates very low free diffusion to occur?
A
Tight junctions
9
Q
What effect does tight junctions have on the location on differing membrane properties & functions?
A
Leads to the apical & basolateral domains to be polarized
10
Q
Epithelia is avascular - what does this mean?
A
- It is entirely cellular (no blood vessels & cells)
- it lacks extracellular fibers
11
Q
Why do epithelial have minimal extracellular space?
A
Due to tight packing of junction
12
Q
What property is CRITICAL to epithelial function?
A
Polarity
13
Q
What do basement membranes separate?
A
Cells from underlying connective tissue (collagen 4)
14
Q
What attaches epithelia to a basement membrane?
A
Epithelial cell’s basal surface attaches to a basement membrane.
15
Q
What is the benefits for epithelia, of epithelia’s basal layer attaching to the basement membrane?
A
- Provides mechanical support
- Supports the growth & survival of epithelial, through controlling its nutrient, ions, proteins & oxygen.
16
Q
What does epithelia rely on for their blood supply?
A
Capillaries in the underlying tissues.
17
Q
Why is the basement membrane’s ability to regulate growth & division of epithelial cells so important?
A
Restricts migration of metastatic cells in the progression of cancer
18
Q
What are the 2 components of the basement membrane?
A
- Basal lamina
- Reticular lamina
19
Q
What is the function of the basal lamina?
A
Provides support by resisting stretching & tearing
20
Q
What can the basal lamina be subdivided into?
A
- Lamina lucida
- Lamina densa
21
Q
What is the function of the reticular lamina?
A
Anchors basal lamina to connective tissue
22
Q
What type of movement does tight junction prevent?
A
Paracellular transport
23
Q
How do claudins determine the ‘tightness’ of tight junctions?
A
Different claudins have different levels of permeability (combinations of claudins determine permeability)
24
Q
Which is more permeable - small intestine or bladder?
A
Small intestine
25
How many claudins genes are there?
24
26
What type of junctions form a belt around the cell?
Adhering junctions
27
What type of junctions allow lateral communication between cell?
Gap junctions (permit small molecules to diffuse) - therefore cells are electrically coupled
28
What are desmosomes?
Extracellular domains that form strong adhesion points
29
What is more likely to occur when the cell experiences a hostile external environment?
Cell death
30
How long does it take for intestine self-renewal to occur?
5 days
31
How long does it take for inter-follicular epidermis self-renewal to occur?
4 weeks
32
How long does it take for lung epithelial self-renewal to occur?
6 months
33
What are the 2 ways of classifying epithelia?
- Simple epithelia
- Stratified epithelia
34
What is simple epithelia?
Single layer of cells
35
Where is an example of simple epithelia?
Lungs
36
What is stratified epithelia?
Many layers of cells
37
What are 2 types of non-typical epithelia classification?
- pseudo-stratified (upper respiratory tract)
- transitional (urothelium - found in bladder)
38
What are the 2 types of simple epithelia?
- simple squamous epithelium
- simple cuboidal epithelia
39
What is the role of simple squamous epithelium?
Facilitate rapid passage of molecules
40
Where is simple squamous epithelium found?
Alveoli
41
What is the difference between simple squamous epithelium and simple cuboidal epithelium?
Simple cuboidal epithelium has a non-motile cilium
42
What are the 2 types of columnar epithelia?
- simple columnar epithelia
- pseudostratified columnar epithelia
43
Where are 2 examples of where simple columnar epithelia can be found?
- GI tract
- Fallopian tubes
44
Which membrane are pseudostratified columnar always touching?
Basolateral membrane
45
What is the most common type of stratified epithelium in human body?
Stratified squamous epithelia
46
Which membrane are stratified squamous epithelia always touching?
Apical cells
47
Where are stratified cuboidal found?
- Glands
- Anus
- Male urethra
- Embryo
48
What is the function of transitional epithelia?
Facilitates shape change in distension without damaging the epithelial lining
49
What system is adopted when glands secrete through ducts?
Exocrine system
50
What system is adopted when glands secrete without ducts?
Endocrine system
51
What are the 3 substances that can be secreted from glands?
- Mucus
- Protein
- Sebum
52
What glands secrete mucus?
Mucus glands
53
What glands secrete protein?
Serous glands
54
What glands secrete Sebum?
Sebaceous glands
55
What are 2 examples of exocrine glands?
- unicellular goblet cells
- multicellular acinar
56
What is the skeletal muscle responsive for?
- Voluntary movement of bones that underpins locomotion
- Control of inspiration by contraction of diaphragm
- Skeletal-muscle pump - help with venous return to the heart
57
Where does contraction take place?
Sarcomere
58
Do skeletal muscles have striations?
Yes
59
Describe the size of the myosin fibres & actin fibres on a skeletal muscle
Thick - myosin fibres
Thin - actin fibres
60
What makes up the Z line in skeletal muscle structure?
Actinin
61
Describe the structure of the actin fibres
Double helical structure in hexagonal shapes
62
The release of what neurotransmitter at the neuromuscular junction initiates an action potential in the plasma membrane of the muscle fibre?
Acetylcholine
63
What is an example of muscles that require fine control?
Movement of the eye (2-6 muscle fibres per motor neurone)
64
What is an example of a muscle that doesn't require fine control?
Gastrocnemius muscle (100-1000 innervated by a single motor neurone)
65
Where does the wave of depolarization pass through following the sarcolemma?
T-tubule network
66
What is the name given to the endoplasmic reticulum in skeletal muscles?
Sarcoplasmic reticulum
67
What substance is released following depolarisation in the T-tubule network?
Intracellular calcium
68
The T-tubule runs near 2 areas of the SR forming a what?
Triad
69
What is the advantage of having a triad?
Enables efficient contraction - enables the wave of depolarisation to enter deep into the cell.
70
Approximately how many myosin heads do each thick filament contain?
300
71
What phase occurs after an interaction between the head of the myosin & actin thin filament?
Powerstroke phase (leading to contraction)
72
Why is muscle contraction an active process?
It is an ATP-requiring process
73
When ATP binds to the myosin head, what happens to the affinity of myosin for actin?
It decreases
74
What occurs when the affinity of myosin for actin decreases (following the binding of ATP)?
The myosin will then detach from the actin.
75
What conformational change occurs to the myosin head following the hydrolysis of the ATP?
The myosin straightens, aligning it with the next actin filament further down.
76
What happens if an electrical stimulus is applied to a muscle?
Measurement of contraction to occur
77
What happens in the latent period (of muscle contraction)?
This is before the release of calcium
78
What happens in the contraction period (of muscle contraction)?
Calcium is released which leads to contraction
79
What happens in the relaxation period (of muscle contraction)?
Calcium is removed, leading to inactivation of muscle contraction
80
What is temporal summation?
Increased frequent stimulus - before relaxation period, another stimulus generated, leading to a bigger development of tension
81
What is unfused tetanus? (think calcium level)
Small level of calcium drop
82
What is fused tetanus? (think calcium level)
No calcium is removed
83
What are the 3 different classes of muscle fibres?
- Slow oxidative (type 1)
- Fast oxidative (type a)
- Fast glycolytic (type b)
84
What type of ATP synthesis is slow oxidative?
aerobic (red)
85
What type of ATP synthesis is slow oxidative?
aerobic (red)
86
What type of ATP synthesis is fast glycolytic?
anaerobic (white)
87
Describe the diameter of slow vs fast muscle
Slow fibres are half the diameter of fast fibres
88
What is isometric contraction?
Muscle at fixed length, tension generated but no change in length.
89
What is isotonic contraction?
Muscle stimulation causes a change in length
90
What molecule enters the cell, when the nerve terminal becomes depolarised?
Calcium
91
What is triggered when extracellular calcium moves into the cell (synapse)?
Acetylcholine-containing vesicles exocytose into the synaptic cleft.
92
What does the acetylcholine molecules that are released into the synaptic cleft bind to?
Acetylcholine receptor channels.
93
What occurs when the acetylcholine receptors on the sarcoplasmic membrane are stimulated?
The channels are opened, leading to a depolarisation of the sarcolemma.
94
What breaks down the acetylcholine to inhibit stimulation of the acetylcholine receptors?
Acetylcholinesterase
95
How does the presynaptic neurone become repolarised?
Potassium leave through the voltage-gated potassium channels, down its electrochemical gradient. This will lead to the repolarisation of the membrane potential.
96
What does the inhibitor tetrodotoxin do?
Inhibits sodium channel - prevents the release of acetylcholine.
97
What does the inhibitor dendrotoxin do?
Inhibits potassium channel - prevents membrane repolarization.
98
What do the inhibitors Tetanus toxin & Botulinum toxin do?
Prevent the release of acetylcholine
99
What does the inhibitor conotoxin do?
Can affect calcium channels - affects the release of acetylcholine
100
What does the inhibitor bungarotoxin do?
Inhibits acetylcholine receptor - prevents transmission of the action potential into the muscle cell
101
What does the inhibitor physostigmine do?
Inhibits acetylcholinesterase
102
What does the inhibitor saxitoxin do?
Inhibit sodium channel - prevents transmission of the polarisation in the muscle membrane
103
What is the physiological consequence of botulinum toxin?
Muscle paralysis
104
How does Botulinum Toxin impact on SNARES?
V&T snares are cut up, preventing the formation of the V snare & T snare complex and therefore the release of acetylcholine
105
What does the V&T SNARE complex formation allow for?
The release of acetylcholine
106
What is a clinical use of botulinum toxin?
Blepharophasm - uncontrolled eyelid movement
Cosmetic treatments - even may help treat migraines
107
What 2 types of muscle is striated?
Skeletal muscle & cardiac muscle
108
Describe the structural differences between cardiac myocytes & skeletal muscle
Cardiac myocytes are shorter and more branched as well as being joined at the intercalated disk
109
What type of junction allows electrical coupling between adjacent myocytes at the intercalated disk?
Gap junction
110
What type of muscle is non-striated?
Smooth muscle
111
What is the primary pacemaker in the heart that can overrule other pacemakers?
Sino-atrial node
112
What 2 processes can cause smooth muscle to contract?
- presence of an action potential
- change in membrane potential
113
What is an example of where smooth muscle is present in a physiological system?
Digestive, urinary & reproductive system
114
What ligand can lead to the contraction of smooth muscle?
Hormones & histamines
115
What are the 2 classes of smooth muscle?
Multiunit & unitary
116
What type of calcium channels are in the T-tubule membrane?
L-type Ca2+ channels
117
What causes a mechanical tethering between L-type Ca2+ channels in the T-tubule & Ca2+ release channels (ryanodine receptors) in skeletal muscles.
An influx of calcium into the T-tubules
118
What removes Calcium from the cytoplasm?
Plasma Membrane Calcium ATPase (PMCA)
119
What does smooth muscle have because it lacks T-tubules?
Shallow invaginations - caveolae
120
What 4 proteins wrap around the actin?
Tropomyosin - (wraps round actin)
Troponin complex - TnC, TnT, TnI
121
What is the role of Troponin C?
Calcium binding protein
122
What is the role of Troponin T?
Interacts with tropomyosin, binding protein
123
What is the role of Troponin I?
Inhibitory protein, prevents the binding of myosin to actin
124
What is the role of the Troponin complex?
Prevents the binding of actin & myosin
125
What binds to the Troponin complex which causes a conformational change, revealing actin fibres?
Calcium
126
Is there Troponin in smooth muscle?
No
127
What is the replacement for Troponin in smooth muscle?
Calponin
128
What happens when the myosin light chain kinase is activated?
It phosphorylates MLC (myosin light chain)
