1
Q
Muscular tissue is made up of _______ cells that are specialized to ____ and _____ force
A
Elongated, contact, exert
2
Q
What are the functions of muscular tissue?
A
Movement
Digestion/waste elimination
Breathing, speech, and expression
Blood/circulatory system
3
Q
What are the three types of muscular tissue?
A
- skeletal
- cardiac
- smooth
4
Q
When you say muscular system, what types of muscular tissue are you referring to?
A
Skeletal
5
Q
Where are skeletal muscles found and describe them
A
- Bone or skin attachment
- Long, parallel unbranched muscle fibers
- Striated
- Voluntary control
- Each muscle fiber has multiple nuclei near edges of cell
6
Q
What types of cells make up skeletal muscles?
A
Muscle fiber (or myofibers)
7
Q
Where is cardiac muscle found and describe it
A
- Found only in heart
- Short, branded cells
- Striated
- Involuntary control
- Central nuclei within each cell
8
Q
What types of cells make up cardiac muscles?
A
Cardiomyocytes
9
Q
Where are smooth muscles found and describe them
A
- Blood vessels and hollow organ (ex: stomach, uterus)
- Fusiform shape
- NO striations
- Involuntary control
- Single nucleus per cell
10
Q
What types of cells make up smooth muscles?
A
Myocytes
11
Q
About how many human skeletal muscles are there? What percentage of our body weight is that?
A
~600 muscles
~50% of body weight
12
Q
What is the major purpose of skeletal muscles?
A
Take chemical energy (ATP) and convert it into mechanical energy
13
Q
What is myology?
A
The study of the muscle system (molecular, cellular, and tissue level)
14
Q
How do muscles function to aid in movement?
A
- externally visible movements
- internal movement (keeping the digestive tract going, helping you pee)
- communication (writing, talking, etc)
15
Q
How do muscles function to aid in stability?
A
- prevent unwanted movement
- help with posture and holding bones/joints in place
16
Q
How do muscles function to aid in the control of body openings and passages?
A
- sphincter muscles
- control how much light we get in our eyeballs
- control where blood goes, waste, etc
17
Q
How do muscles function to aid in heat generation?
A
- 20-30% of body heat
18
Q
How do muscles function to aid in glycemic control?
A
- aids in regulation of blood glucose
- absorbs, stores, and uses glucose
19
Q
Why are older individuals more prone to type 2 diabetes?
A
Because they have decreased muscle mass and function, which means their muscles don’t do as well of job at absorbing, storing, and using glucose properly
20
Q
What type of muscle is voluntary and striated?
A
Skeletal
21
Q
What type of muscle is involuntary and not striated?
A
Smooth
22
Q
What type of muscle is involuntary and striated?
A
Cardiac
23
Q
Muscle cells have some universal properties. What does it mean for a muscle to be excitable?
A
- Respond when stimulated
- Can be stimulated via electrical changes across the plasma membrane
24
Q
Muscle cells have some universal properties. What does it mean for a muscle to exhibit conductivity?
A
- Local electrical excitation imitates a wave of excitation that travels along the muscle fiber
- Which is how it contracts
- (The muscle fiber is the conductor of the excitation)
25
Muscle cells have some universal properties. What does it mean for a muscle to be contractable?
- Shortens when stimulated (resulting in movement)
26
Muscle cells have some universal properties. What does it mean for a muscle to exhibit extensibility?
- Capable of being stretched between contractions
27
Muscle cells have some universal properties. What does it mean for a muscle to exhibit elasticity?
- Returns to its original rest length after being stretched
28
What is the thick myofilament?
Myosin
29
What is the thin myofilament?
Actin
30
A bunch of myofilaments together make a ___?
Myofibril
31
A bunch of myofibrils together make a ____?
Muscle Fiber
32
A muscle fiber is surrounded by?
Endomysium
33
Muscle fibers are bundled into ________
Muscle fascicles
34
Muscle fascicles are surrounded by ______
Perimysium
35
Muscle fascicles all together make up the ______
Muscle
36
The muscle is surrounded by ________
Epimysium
37
What are -myosiums made up of?
[primarily] areolar connective tissue
38
What are the 3 myosiums and what do they surround?
1. epimysium (fibrous sheath, surrounds whole muscle)
2. Perimysium (thickish CT, surrounds muscle fascicles)
3. Endomysium (loose CT, surrounds muscle fiber)
39
What are some features of the epimysium?
Fibrous sheath
| Fascia - sheet of CT that separates muscles/groups
40
What are some features of the perimysium?
Thickish CT
| Nerves, blood vessels, and stretch receptors
41
What are some features of the endomysium?
Loose CT
Allows room for capillaries and nerves
Extracellular chemical environment for contraction
42
Describe skeletal muscle cells? What are they called
Long, slender shape
Multiple nuclei - pressed against the inside of the sarcolemma
Name: muscle fibers
43
What is the sarcolemma?
Plasma membrane of muscle fiber (muscle cell)
44
What is the sarcoplasm?
Cytoplasm of a muscle fiber (muscle cell)
45
What are myofibrils?
Thick bundles of contractile proteins
| Myofilaments = actin and myosin
46
What can you find packed between myofibrils?
Mitochondria, smooth endoplasm reticulum
Glycogen (carbohydrate)
Myoglobin (oxygen-storing pigment)
47
What are Transverse (T) tubules and what do they do?
Infoldings of the sarcolemma
Penetrate muscle fiber
Carry electrical current
48
What is the sarcoplasmic reticulum and what does it store?
Smooth endoplasmic reticulum of muscle fiber
Forms web around myofibrils
Stores calcium
49
What are terminal cisternae?
Dilated sacs around T tubules
| Aid in calcium storage by binding to calsequestrin
50
What is a Triad?
T tubule + 2 terminal cisterns
51
What does the sarcoplasmic reticulum need to released into the cytosol for a muscle contraction?
Calcium
52
Describe thick filaments/myosin
2 chains: shaft-like tail and double globular head (golf club)
Heads directed outward in a helical array (head on one half angle to left, angle to right on other half, bare zone in the middle with no heads)
53
What are elastic filaments called and what do they do?
```
Titin (aka connectin)
Huge, springy protein
Runs through core of thick filament (anchors myosin to Z disc and M line)
Stabilizes and positions
Prevents overstitching
Provides recoil
```
54
What do contractile proteins do in a myofilament?
shorten the muscle fiber
55
What regulatory proteins are found in a myofilament and what do they do?
Tropomyosin and troponin
Act like a switch that determines when fiber can (and cannot) contract
Calcium can flip the switch
56
Where types of cells are myosin and actin found?
Nearly all cells
Most abundant in skeletal and cardiac muscle
Organization accounts for striations in muscles
57
What do other proteins associated with myofilaments do?
Anchor, align, and regulate
58
What is dystrophin and what does it do?
It's a clinically important protein
Links actin in outermost myofilaments to membrane proteins and then to the endomysium
transfers forces of muscle contraction to CT and ultimately leads to tendon
59
What protein is muscular dystrophy related to?
Dystrophin (genetic defects in it)
60
How do striations occur?
Precise organization of actin and myosin
61
What is the different in A bands and I bands?
A bands:
- dark bands
- thick and thin filaments overlap
- Middle part (H-band) has myosin only (so not as dark)
I bands:
- light bands
- only thin filaments
- bisected by thin dark line (Z disc)
62
What is a sarcomere and what does it do?
The segment from one Z disc to the next
Functional contractile unit
Muscle shortening - due to sarcomeres shortening/sliding, pull z discs closer together
63
What is the functional contractile unit in a muscle cell?
Sarcomere
64
What changes during shortening of a sarcomere?
The amount of overlap
65
Do thick filaments change length during shortening of a sarcomere? What about thin filaments?
Neither change length, only the amount of overlap changes
66
How does dystrophin play into shortening of a sarcomere?
Dystrophin and linking proteins pull on extracellular proteins
This transfers pull to the extracellular tissues
67
What must happen for skeletal muscle to contract?
It must be stimulated by a nerve (or artificially)
68
What happens if nerve connections are lost?
The muscle is paralyzen
69
What is denervation atrophy?
Shrinkage of paralyzed muscle when nerve remains disconnected
70
What are the two types of cells in nervous tissue?
1. Neurons (nerve cells, initiate and conduct electrical activity)
2. Glial cells (cells that support and protect neurons)
71
What do somatic motor neurons do?
Stimulate skeletal muscles
| Soma located in brainstem/spinal cord
72
What are somatic nerve fibers and what do they do?
Axons of motor neurons leading to muscles
Branch to muscle muscle fibers
One fiber : one motor neuron
73
Can 1 neuron innervate multiple fibers?
Yes
74
Can 1 fiber have multiple neurons innervating it? Why/how?
No
| Because you don't want conflicting signals, so just one neuron so only one signal
75
What is a motor unit? How big are they?
One motor neuron and all the muscle fibers supplied (all contract at once)
Some are very large for power (1 neuron = ~1000 fibers)
Some are very small for fine motor control (1 neuron = 3-5 fibers)
76
What does it mean for motor units to "work in shifts"
Don't always all need to work at once
We are always using muscles (ex: just to hold our head up in class)
Working in shifts prevents fatigue
Helps with long-term contraction of muscle
77
What is the place called where a nerve meets a muscle fiber?
Synapse
78
What is an axon terminal? What's another name for it?
Aka synaptic knob
| Swelling / depression in muscle fiber
79
What is the synaptic cleft?
Gap between terminal and sarcolemma
80
What insulates the neuromuscular junction (NMJ)?
```
Schwann Cells
Basal lamina (layer of collagen and glycoprotein)
```
81
What are synaptic vesicles?
```
Membrane-bound sacs in axon terminal
Contain acetylcholine (ACh), a neurotransmitter
```
82
What is ACh and what does it do?
Acetylcholine (a neurotransmitter)
Released by nerve fiber (via exocytosis)
Binds to receptors on sarcolemma (motor end plate)
83
What is the purpose of junctional folds?
Increase the surface area
84
What is acetylcholinesterase?
An enzyme that breaks down acetylcholine (stops muscle stimulation)
85
What are the steps of muscle contraction (4)?
1. Excitation
2. Excitation-Contraction Coupling
3. Contraction
4. Relaxation
86
What happens in the first step of muscle contraction (excitation)?
Process in which nerve action potentials lead to muscle action potentials
Electrical nerve signal --> electrical signal (action potential) in muscle fiber
87
Describe the steps of muscle excitation (4)
1. Nerve signal arrives at terminal
2. Stimulates synaptic vesicles to release ACh into cleft (diffuses across cleft)
3. Binds ACh receptors on sarcolemma
4. Initiates wave of voltage changes (action potential) spread in all directions away from neuromuscular junction and down t-tubules
88
Describe the steps of excitation-contraction coupling (5)
1. Action potentials pass into/down t-tubules (sarcoplasmic reticulum triggers calcium release from terminal cisterns)
2. Cytosol floods
3. Calcium binds to troponin
4. Calcium binding leads to change in shape of troponin-tropomyosin complex, which reveals active sites on actin
5. During all this, ATP binds to myosin heads, spits into ADP and phosphate, and the myosin head becomes cocked into postion
**Action potentials on sarcolemma lead to activation of myofilaments**
89
Describe the steps of muscle contraction (like break down step 3 of the entire contraction process) (3 steps)
1. Myosin head binds to active site on actin, forms cross-bridge
2. Myosin releases phosphate and ADP, flexes into OG position, power stroke
3. ATP binds to m myosin AGAIN, actin released by myosin head, breaks the cross-bridge
**the head is now prepared to repeat the whole process**
90
Describe what happens to the following when a muscle contracts and a sarcomere shortens:
- Z discs
- A bands
- I bands
- Thin filaments
- H band
- Z discs: move closer together
- A bands: do NOT shorten
- I bands: narrow
- Thin filaments: do not shorten, slide toward the M-line
- H band: shortens/disappears
91
Describe the relationship between thick and thin filaments during contraction
Thin filaments slide past thick filaments
92
Do the length of filaments change when the muscle is contracted or relaxed?
They never change, only their relative positions change
93
Describe the steps of muscle relaxation (4)
1. Nerve signal ceases, no more ACh released
2. ACh already in synapse is released from receptors, broken down by acetylcholinesterase, stops muscle fiber stimulation
3. Calcium is actively pumped out of the cytoplasm and reabsorbed by the sarcoplasmic reticulum (requires ATP)
4. In the troponin-tropomyosin complex, calcium dissociates, everything returns to resting positions, myosin is blocked from binding to actin, muscle is relaxed
Anatomy
flashcards
Decks in class (14)
# Cards
-
Intro Vocab22
-
Glands And Membranes (ch 3)55
-
Chapter 5 - Integumentary System62
-
Types of Tissues (ch 3)59
-
General Ch 36
-
Chapter 6 - Bone Tissue54
-
Chapter 7 - Axial Skelly64
-
Chapter 8 - Appendicular Skelly63
-
Chapter 9 - Joints88
-
Chapter 10 - Muscular System93
-
Chapter 11 - Muscular System pt 242
-
Master Muscle List121
-
Nervous Tissue - Chapter 1344
-
Spinal Cord - Chapter 1420
