D4. Muscles Flashcards
1
Q
Smooth Muscle
A
- Long and tapered at each end
- Only one nucleus
- Lines the internal organs
- Involuntary
- Slower to contract than skeletal
- Sustain prolonged contractions
- Does not fatigue easily
2
Q
Cardiac (heart) muscle
A
- Forms the walls of the heart
- Tubular and striated (bands of light and dark)
- Cells have one nucleus
- Branched, creating a net-like structure
- Involuntary
3
Q
Skeletal (striated) muscle: Function
A
- Allow body to move
- Atached to the bone with tendons
- Protects internal organs
- Stabilize joints
- Supports body
- Helps maintain a constant body temperature
4
Q
Skeletal (striated) muscle: Structure
A
- Very long
- Many nuclei
- Voluntary - it’s contraction is consciously controlled by the nervous system
- Striated/tubular
5
Q
Hierarchy of Muscle Structure
A
- Muscle
- Muscle-fibre bundle
- Muscle fibre
- Myofibrils
- Myofilaments
6
Q
Two types of myofilaments
A
- Actin: Light, thin filaments
- Myosin: Dark, thick filaments
7
Q
Sliding Filament Model
A
- Muscles contract when coordinated sliding and pulling motions occur between Z bands
- When a muscle is relaxed, myosin heads are not bound to actin
8
Q
Sacromere
A
- Section of a myofibril from one Z-line to the next
- The arrangement of these sacromeres next to each other produces the striations of the skeletal muscle fibers
9
Q
The Sliding Filament Model
A
- Muscles contract when coordinated sliding and pulling motions occur between Z bands
- When a muscle is relaxed, myosin heads are not bound to actin
10
Q
The Role of Calcium and Regulatory Proteins
A
- An increase in Ca2+ levels trigger changes that expose binding sites for myosin
- The myosin heads bind to actin filaments
- Once bound, the myosin heads will tilt towards the sacromere’s center, sliding the bound actin filament with them
- The myosin head contains ATPase
- When ATP binds to a myosin head, the head releases its grip on actin
- The ATP is hydrolyzed to ADP and the myosin head reverts to its original position
- If Ca2+ and ATP are still present, the procecss may be repeated
11
Q
Energy Sources for Contraction
A
- ATP reserves: Small amount found around myofilbrils/can provide only a brief contraction
- Creatine Phosphate: Initial source of energy to regenerate ATP from ADP and P; only lasts about 10 seconds
- Cellular Respiration: Produces up to 38 ATP per glucose molecule (requires O2)
12
Q
Types of Skeletal Muscle Fibers
Slow-Twitch
A
- Sustain long contractions, often found in muscles that maintain posture
- Rely on aerobic respiration
- Break down ATP slowly, but efficiently to release energy
- Found in greater abundance in distance runners
12
Q
Types of Skeletal Muscle Fibers
Fast-Twitch
A
- Brief, rapid, powerful contractions
- Rely on glycolysis (anaerobic respiration)
- Found in abundance in sprinters
13
Q
Muscle Fatigue
A
- The inability of the muscles to contract
- Causes:
- Lack of oxygen
- Lack of ATP
- Accumulation of wastes (lactic acid, pyruvic acid, etc.) → lowered pH is caused by acids, results in increased heart rate
14
Q
Nerve Control of Muscle Tension
Muscle Twitch
A
- Skeletal muscles are stimulated by nerves
- The arrival of nerve impulse causes a muscle fibre to undergo a single contraction or a twitch
