Chapter 9: Muscles And Muscle Tissue Flashcards
What are the 3 types of muscle tissue?
- Skeletal
- Cardiac
- Smooth
Describe Skeletal Muscle Tissue
- Striated
- Location: Attached to skin and bone
- Voluntary
Describe Cardiac Muscle Tissue
- Striated
- Location: Heart
- Involuntary
Describe Smooth Muscle Tissue
- No Striations
- Location: Walls of hollow organs
- Involuntary
What are the 4 main characteristics of muscle tissue?
1) Excitability (responsiveness)
2) Contractibility
3) Extensibility
4) Elasticity
Excitability (responsiveness)
Ability to receive and respond to stimuli
Contractibility
Ability to shorten forcibly when stimulated
Extensibility
Ability to be stretched
Elasticity
Ability to recoil to resting length
What are the 4 main functions of the muscle?
- Produce movement
- Maintain posture
- Stabilize joints
- Generate heat as they contract
What are the 3 features of the Skeletal muscle anatomy?
1) Nerve and blood supply
2) CT sheaths
3) Attachments
Nerve and Blood Supply
- Each muscle receives a nerve, artery, and veins–> cellular respiration
- Contracting muscle fibers require huge amounts of oxygen and nutrients
CT Sheaths
- Every skeletal muscle (and muscle fiber) is covered in CT
- Support cells and reinforce whole muscle
- Sheaths from external to internal (3)
What are the 3 Sheaths of CT?
1) Epimysium
2) Perimysium
3) Endomysium
Epimysium
Dense irregular CT surrounding entire muscle
Perimysium
Fibrous CT surrounding fascicles
Endomysium
Fine areolar CT surrounding each muscle fiber (cell)
Attachments
• Muscle spans joints and attach to bones
- Muscles attach to bone in a least (2) places:
• Insertion
• Origin
Insertion
Attachment to movable bone
Origin
Attachment to immovable or less movable bone
Sarcolemma
Muscle fiber plasma membrane
Sarcoplasm
Muscle fiber cytoplasm
Myofibrils
Densely packed, rodlike elements
Muscle tension
The force exerted on load or object to be moved; produced by contraction
What are the 2 types of contractions?
1) Isometric
2) Isotonic
Isometric Contraction
No shortening; muscle tension increases but does not exceed load
Isotonic Contraction
Muscle shortens because muscle tension exceeds load
Why does the force and duration of a contraction vary?
In response to stimuli of different frequencies and intensities
Motor Unit
Consists of the motor neuron and all muscle fibers it supplies
Muscle twitch
Simplest contraction resulting from a muscle fiber’s response to a single action potential from motor neuron
Why do graded muscle responses vary?
The various strength of contractions are for different demands
How do muscles graded in response to change change in stimulus frequency?
- Single stimuli= single contractile (i.e muscle twitch)
- Multiple stimuli= multiple contractiles from same fiber
How does stimulus strength change to muscle response?
Recruitment (or multiple unit stimulation )
Recruitment (or multiple unit stimulation )
Stimulus is sent to more muscle fibers, leading to more precise control
What are the 3 types of stimulus in recruitment?
1) Sub threshold
2) Threshold
3) Maximal
Sub Threshold stimulus
Stimulus not strong enough, so no contractions seen
Threshold stimulus
Stimulus is strong enough to cause first observable contraction
Maximal stimulus
Strongest stimulus that increases maximum contractile force
Describe the asynchronous contraction of motor units in muscles?
Tag team back-and-forth, contracting and relaxing
Muscle tone
Constant, slightly contracted state of all muscles
ATP supplies the energy needed for the muscle fiber to:
- Move and detach cross bridges
- Pump calcium back into SR
- End the action potential moving through the muscle
What are the 3 mechanisms in which ATP is regenerated quickly?
- Direct phosphorylation of ADP by creatine phosphate (CP)
- Anaerobic pathway; glycolysis and lactic acid formation
- Aerobic respiration
