The muscular system Flashcards
(43 cards)
Muscle structure
A muscle is a group of specialised elastic tissues Muscles comprise 23% of a woman’s and 40% of a
man’s body
Each skeletal muscle is an organ that consists of ——-
various integrated tissues these Tissues include the skeletal muscle fibres, blood vessels,
nerve fibres, and connective tissue
Each skeletal muscle has three layers of connective tissue These compartmentalize the muscle fibres within the muscle
1-Epimysium
2-Perimysium
3-Endomysium
what is Epimysium
Each muscle is wrapped in a sheath of dense connective tissue called the epimysium
* Separates muscle from other tissues and organs in
the area, allowing the muscle to move independently
what is Perimysium
Inside each skeletal muscle, muscle fibres are organized into individual bundles Each called a fascicle,
surrounded by a middle layer of connective tissue
called the perimysium
what is Endomysium
- Inside each fascicle, each muscle fibre is encased in a thin connective tissue layer of collagen and reticular fibres called the endomysium.
- The endomysium contains the extracellular fluid and nutrients to support the muscle fibre.
- These nutrients are supplied via blood to the muscle tissue.
Muscle function
- The best-known feature of skeletal muscle is its ability to contract and cause movement
- They can also stop movement E.g. resisting gravity to maintain posture
- Small, constant adjustments of the skeletal muscles are needed to hold a body upright or balanced in any position
what is Skeletal muscle
- Striated and voluntary
- Muscles under conscious control
- Has cylindrical cells which make up fibres
- Each muscle fibre (cell) is multinucleated
- Muscle fibres form bundles
- Bundles all run in the same direction
1-The plasma membrane of muscle fibers is called the-
2-The cytoplasm is referred to as ——
3-The endoplasmic reticulum is called the——-
1-sarcolemma
2-sarcoplasm
3-sarcoplasmic reticulum
The sarcomere
- The functional unit of a skeletal muscle fibre
- Contains thin filaments of actin and thick filaments of myosin
- These slide over each other during contraction
- Approximately 2μm in length
- Bordered by z-discs/z-lines
how does the The sarcomere work
- ATP and Ca+ are required for the muscle to contract
- Myosin heads on the thick filaments form cross bridges with the thin filaments
- Thin filaments slide over the thick filaments
- Sarcomere shortens
what is Smooth muscle
- Non striated and involuntary
- Found in the walls of hollow organs e.g. urinary bladder, uterus, stomach, intestines etc.
- Muscle fibres are spindle shaped
- Have a single nucleus
- Have no distinct membrane
- Also have actin and myosin
what is Cardiac muscle
-Only found in the heart
-Involuntary but similar to skeletal muscle
-Also organised into sarcomeres
-Fibres are shorter than skeletal muscle fibres
-Fibres contain only 1 nucleus
-Possess many mitochondria and myoglobin
-ATP produced mainly from aerobic respiration
-Cells connected by intercalated discs
Types of contractions
1-Isometric contraction
* As the muscle contracts its length remains the same whilst the tension increases
2-Isotonic contraction
* As the muscle contracts its length changes whilst the tension remains constant
Making movement
- Muscle contraction pulls one bone towards another moving the limb
- Muscles never work alone
- Any movement results from the actions of several muscles
- Muscles generally work in pairs
- Agonist & antagonist
The agonist is the—–
The antagonist is the——
1-contracting muscle
2-opposing relaxing muscle
The agonist and antagonist must contract and relax equally for smooth movement
what cuses muscles contract
- Impulses from a motor neuron causes muscle contraction
- Each motor neuron synapses with numerous muscle fibres
- All the muscle fibres innervated by a single motor neuron contract together
- Motor unit
Requirements for muscle contraction
An adequate blood supply is required to:
* Provide oxygen and nutrients
* Remove carbon dioxide and waste products
* Muscles receive nutrients and oxygen from the arterial capillaries
* They are used by the muscle to generate energy
* Waste products e.g. lactic acid is excreted into the venous blood stream
What affects muscle contraction
1-Energy available
2-Strength of the stimulus from the nerve
3-Time muscle has been contracting
4-Adequate blood supply bringing enough oxygen and nutrients
5-Strength of inhibitory nerve supply
6-Temperature of muscle (warmth increases response)
7-Presence of waste products e.g. lactic acid
Different stages of contraction
1-Tone
Slight degree of contraction by some fibres as others are relaxing This happens even during sleep Also to maintain posture
2-Relaxation
A lessening of tension A reduction in the number of fibres contracting at any one time Muscle tension can be affected by conscious effort
Problems with over-contraction
Muscle tension and Muscle fatigue
what is Muscle tension
*Over stimulation of muscle fibres
*More fibres contract than are necessary to maintain postural tone
what is Muscle fatigue
*Muscles need oxygen and fuel for its energy
*Glucose is the main source of energy
*Glucose is stored as glycogen and fats in muscle
*Glucose and fats are burned to release energy using oxygen from the blood
*Continuous contraction leads to oxygen deficiency
*Results in lactic acid build up causing a burning sensation
*Muscle soon stops contracting.
*Causes stiffness and pain
Important terms in muscles
1-Origin
* The fixed end of a muscle
* This end barely moves during muscle action
2-Insertion
* The moving end of a muscle
* The point to which the force of a muscle is directed
* A muscle always works from its insertion towards its origin
3-Attachment
* At their origin and insertion muscles are attached to bone via tendons
* This produces movement of joints
* They sometimes take attachment from other connective tissue e.g. cartilage or fascia of other muscle
4-Belly
* Thickest part or main body of a muscle
* Usually the middle part of the muscle
