Muscle Tissue (Structure and Function) Flashcards
1
Q
What are the 2 muscle cell types?
A
Striated and non-striated
2
Q
What are the 2 muscle cell types further divided into?
A
Striated - skeletal muscle and cardiac muscle
Non-striated - smooth muscle
3
Q
What is always present in striated muscle?
A
Myoglobin
4
Q
2 ways in which cardiac and smooth muscle are similar
A
- involuntary control
- indirect nerve-muscle communication (cell doesn’t interact directly with cardiac/smooth muscle)
5
Q
How do skeletal muscles communicate with nerve?
A
Direct nerve-muscle communication (nerve attaches to the muscle and stimulates it)
6
Q
How do Cardiac Muscles Communicate with nerve
A
Indirect nerve-muscle communication
7
Q
How do Smooth muscles communicate with nerve
A
Indirect nerve-muscle communication
8
Q
What is myoglobin and its function?
A
An oxygen-storing molecule, providing oxygen to working striated muscles
9
Q
What makes myoglobin good at its function?
A
Myoglobin has a higher affinity for oxygen than haemoglobin, especially at low pH, so at extremities of the body where CO2 levels are high
10
Q
What happens when striated muscle dies or is damaged?
A
Myoglobin is released into the bloodstream and is taken up by the kidneys to be removed from the blood (myoglobinuria- tea coloured urine)
11
Q
What is
1. muscle necrosis
2. rhabdomyolysis
3. myoglobinaemia
A
- When striated muscle dies (muscle necrosis)
- When damaged (rhabdomyolysis)
- `myoglobin is released into the bloodstream (myoglobinaemia)
12
Q
How can myoglobin cause renal damage?
A
If the kidneys take up too much myoglobin it can block the glomerulus and cause renal damage
13
Q
What is the sarcolemma?
A
The outer membrane of a muscle cell (like a plasma membrane)
14
Q
What is the Sarcoplasm
A
cytoplasm of a muscle cell
15
Q
What is a sarcosome
A
The mitochondrion of muscle cells
16
Q
What is the Sacromere
A
The contraction unit in striated muscle
( z line to z line)
17
Q
What is the Sacroplasmic reticulum
A
The Smooth Endoplasmic Reticulum of a muscle cell
18
Q
What is a T-tubule?
A
Connects the myofibrils to the sarcolemma
19
Q
3 connective tissue components of striated muscle
A
Endomysium
Perimysium
Epimysium
20
Q
How do you get the striated pattern
A
Dark Band then White band layers
21
Q
What is a striated muscle cell called
A
A striated muscle cell is called a muscle fibre
22
Q
What is the plasmalemma of a muscle cell called
A
The plasmalemma of a muscle cell is called its sarcolemma
23
Q
What does each cell (fibre) contain
A
Each cell (fibre) contains numerous myofibrils
24
Q
What is thicker between myosin filament and actin filament
A
Myosin Filament = Thick
Actin Filament = Thin
25
What is the structure of Myofibrils
Look at lecture slide
26
Describe the endomysium?
Surrounding loose connective tissue of different muscle fibres within a fascicle. Contains capillaries and small nerve endings
27
Describe the perimysium
Connective tissue surrounding the fascicle (make up the muscle) and contains arterioles and venuoles
28
Describe the epimysium
Dense connective tissue layer on a muscle that is continuous with tendon
29
What is a point of origin and insertion in skeletal muscles?
Origin - where tendon attaches to bone - does not move during contraction
Insertion - where muscle attached to bone - does move when the muscle contracts
30
What is thicker between myosin filament and actin filament
Myosin Filament = Thick
Actin Filament = Thin
31
What is direction of movement dependent on?
Movement is always along the direction of a fascicle
(direction of the muscle fibres (cells) contraction
32
Where is movement created?
At the insertion point if it crosses a joint
33
Where is tension created in skeletal muscles?
At the origin point
34
What is the function of Skeletal muscles
The function is to Contract
35
What is a Fascicle
Each fascicle (or fasciculus) is a bundle of muscle fibers, also called myocytes, bound together via the endomysium tissue that provides pathways for the passage of blood vessels and nerves.
36
Why is Direction of movement of muscles not easy to predict
Lots of different muscle shapes
Movement if always along the direction of a fascicle
37
What do extrinsic muscles of the tongue do?
Attached to bone or cartilage and allows movement of the tongue - retract it and move side to side
38
Which muscle in the tongue permits us to stick the tongue out?
Geniohyoid muscle - attached to chin and base of tongue
39
Describe intrinsic muscles of the tongue and their role
They are not attached to bone (muscle to muscle only) and allow tongue to change shape but not position. AID IN SWALLOWING
40
Where are nuclei found in skeletal muscle histology?
Peripheral in transverse section of fascicles (appear as a bundle of muscle cells)
Nuclei in rows in longitudinal section
41
What accounts for the mobility of the Tongue
The plasticity and strength of the connective tissues
and the multidirectional orientation of the muscle fibres accounts for the mobility of the tongue
42
What is each fascicle in a skeletal muscle shown to be surrounded by in histology?
Perimysium (connective tissue) carrying nerves and blood vessels
43
What are the dark longitudinal streaks seen on histology of skeletal muscles?
Mitochondria
44
What is a muscle fibre made up of?
Contains numerous myofibrils
45
What makes up myofibrils?
Sarcomeres
46
What is a myofibril?
Make up muscle fibres which form fascicles
47
What is a fascicle?
Bundles of muscle fibres
48
A-band of a sarcomere
Where actin and myosin overlap - thick bands
49
I-band of sarcomere
Only contains actin filaments - light bands
50
Why would you find fibroblasts in skeletal muscle histology?
They lay down material for endomysium
51
In a transverse section of myofibrils in histology, what are the individual dots?
Myosin filaments
52
What are t-tubules usually associated with?
Mitochondrial line
53
Types of muscle fibres in skeletal
Slow (Type 1)
fast ( Typw 2A)
intermediate (Type 2B)
54
Different fibres require different amounts of blood, how does this work
* Thin fibres less blood
* Thick fibres more blood
55
What are the three types of contraction speeds
What does a fascicle have
Three types:
Slow, fast and intermediate
Each fascicle has at least one of each
56
What are red muscle fibres?
Slow twitch
57
What are white muscle fibres?
Fast twitch
58
Why are fast twitch muscles white
As they do not contain much blood
59
Compare the amount of myoglobin and mitochondria in fast twitch compared to slow switch muscle fibres
High amount of myoglobin and mitochondria (and therefore cytochrome) in slow twitch fibres, low amounts in fast
60
What is the relative diameter in fast twitch fibres compared to slows?
Fast have a large diameter and slow have a smaller diameter
61
Example site of slow twitch muscle fibres
Spinal muscles
62
How does myoglobin differ to haemoglobin?
Myoglobin can only bind to oxygen, whereas haemoglobin can also bind to CO2
63
What do type 2A fibres do?
Type 2A fibres are sometimes called intermediate fibres because they possess characteristics that are intermediate between fast fibres and slow fibres. They produce ATP relatively quickly, more quickly than SO fibres, and thus can produce relatively high amounts of tension.
64
Difference between slow and fast twitch fibres
LECTURE SLIDE PG 25
65
What are the types of Slow twich fibres
Type 1 (Slow oxidative) fibres
66
What are the types of fast twitch muscle fibres
- Type 2A (Fast oxidative glycolytic) fibres
- Type 2B (2X; Fast glycolytic) fibres
67
Which twitch, slow or fast, requires a rich capillary supply?
Slow requires rich capillary supply as its aerobic, whereas fast twitch is anaerobic
68
Oxidative and glycolytic muscle fibres
Oxidative 32 mol ATP/mol glucose - slow twitch
Glycolytic - 2 mol ATP/mol glucose - fast twitch
69
What does continued muscle contraction depend on?
Calcium ions
Amounts of ATP
70
How are cardiac cells joined to adjacent cells?
Using intercalated disks
71
What are intercalated disks used for in cardiac muscle cells?
Allow electrical signals through to adjacent cells so they can't contract together
72
How and what ions pass through adjacent cardiac cells?
The gap junctions allow ATP and Ca2+ through as they are essential to continue muscle contraction
73
What happens when the intercalated disk becomes damaged and the cardiac myocyte is broken?
The cell isn't getting nutrients from adjacent cells so dies - fibroblasts fill this with connective tissue and make a scar.
74
Which muscle fibres are able to branch?
Cardiac muscle fibres
75
What two peptides are released during cardiac distension (failure)?
Atrial natriuretic peptide (ANP) released by atria
Brain-type natriuretic peptide (BNP) released by ventricles
76
When will BNP be released by the ventricles? (2)
During left ventricular hypertrophy
Mitral valve disease
77
What hormone is released during congestive heart failure?
ANP - reduces blood volume and therefore blood pressure
78
How does ANP work to reduce blood pressure? (2)
1. Increases glomerulus filtration rate in kidneys so more fluid released from bladder
2. Decreases renin enzyme which decrease AngII and Aldo (constrict arterioles) leading to vasodilation and more fluid excreted via pee
79
What is hypertrophy?
Cells enlarge
80
What is hyperplasia?
multiplication of cells of same size by cell division/mitosis
81
What is atrophy?
Decrease in cell size
82
What nerve system control involuntary cardiac muscles?
Autonomous nervous system
83
Describe how nerve signals cause atria to contract
1. Signal is sent to sinoatrial node
2. Sinoatrial node receives this signal and send it though Bachmann muddles which are around the atria
3. Cause the atria to contract
84
Describe how nerve signals can cause ventricle contraction
1. Signals from sinoatrial node are sent to atrioventricular node
2. This collects electrical signals and stores them until a threshold is reached
3. Once reached, signals are fired down septum to Bundle of His
4. Bundle of His divides into left and right branches which pass to Purkinje fibres
5. Purkinje fibres make ventricles contract
85
Why is the conducting system of the heart effective?
You can achieve coordinated control... atria contracts first followed by ventricles
86
How do Purkinje fibres allow ventricles to contract in almost synchronous manner?
Conduct action potentials more rapidly than normal cardiac muscle fibres as the intercalated disk in Purkinje fibres becomes the outer part of the cell so multiple cells are connected
87
Are Purkinje fibres striated?
No, as they have sparse myofibrils
88
Where will you find Purkinje fibres?
Apex of the heart close to the endocardium lining of the ventricle
89
Where are nuclei found in cardiac muscles compared to skeletal?
Nuclei are central in cardiac muscle ( and sometimes 2/cell) and peripheral in skeletal
90
How do contractive cell types differ from cardiac to skeletal muscles?
Cardiac only have one type of contractive cell - cardiomyocytes
Skeletal more - fast and slow twitch fibres
91
How are contraction mechanisms similar in cardiac and skeletal muscles?
Both have sarcomeres, but sarcomere less well developed in cardiac
92
What is the shape of a smooth muscle cell?
Spindle shaped with a single central large nucleus
93
What are smooth muscles capable of that other aren't?
They can be stretched substantially and may remain contracted for hours or days as long as enough calcium and ATP
94
What dopes contraction of smooth muscle cells rely on?
Actin-myosin interactions
95
Why is contraction slower in smooth muscles?
There are no sarcomeres
96
4 stimulus of smooth muscle cell
Hormones
drugs
nerve signals
blood gases
97
How do ATP and calcium travel between smooth muscle cells?
Through gap junctions
98
What structures are found running along the edge of smooth muscle? What is their function?
Pinocytic caveolae (cave-like invaginations) they undergo pinocytosis to sample extracellular space for drugs e.t.c
99
What are dense bodies in smooth muscle cell?
Act as an attachment point for actin filaments for muscle contraction
Connection : Dense body -> actin -> myosin -> actin -> dense body
100
What is connected to dense plaques in smooth muscle cells?
Associated with intermediate funk arts which hold the shape of the cell and prevent too much change in structure during contraction
101
Where are smooth muscles found?
Contractile walls of passages or cavities like respiratory tract
102
4 clinical disorders due to involuntary smooth muscle
Lung disease e.g asthma due to bronchi muscle spasm
Painful menstruation
Incontinence - bladder made of smooth muscle
High blood pressure
103
How are most smooth muscles innervated?
By autonomic nervous system fibres
Release neurotransmitters from varicosities which contain synaptic vesicles into a wide synaptic cleft
Cells are stimulated at the same time
Coordinated contraction of smooth muscle cell
104
Why are smooth muscle cells often damaged?
The cells shorten by about 80% during contraction and can hold that configuration while calcium and ATP are present, meaning its easier for them to break or tear
105
To what extent are cardiac muscles capable of regeneration?
Incapable of regeneration- following damage, fibroblasts layer down scar tissue
106
Incapable of regeneration- following damage, fibroblasts layer down scar tissue
They cannot divide (no mitotic ability) but can regenerate by satellite cells- hyperplasia follows muscle injury
107
What are satellite cells?
Stem cells which can give rise to myoblasts which go on to make muscle tissue
108
To what extent can smooth muscle repair itself?
Very good at repairing themselves as they retain their mitotic ability so can form new cells
109
What special cell contacts does the intercalated disc contain in cardiac muscle?
Fascia adherens, desmosomes and gap junctions - gap junctions allows fast electrical conductance between mardiomyocytes
