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Human Bio > Muscular system > Flashcards

Muscular system Flashcards

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1
Q

Skeletal muscle

A
  • elongated (long cylindrical fibre)
  • striated
  • have many nuclei (multinucleate)
    Cells are surrounded and bundled by connective tissue = great force, but tires easily, Under conscious control. (Voluntary), Attached to bones of skeleton allow posture, form contours + form. Contractions bring about movement at the joints.
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2
Q

Cardiac muscle

A

-Has striations, Branched cylindrical fibre, 1 centrally located nucleus, Involuntary
-Joined to another muscle cell at an intercalated disc
- Found only in the heart. When contracts, it reduces the space in the chambers of the heart and pushes the blood from the heart into the blood vessels.
Steady pace (contract + relax rhythmically without tiring or stopping)

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3
Q

Smooth muscle

A

Has no striations, Spindle-shaped cells, Single nucleus (central), Involuntary – no conscious control
Found mainly in the walls of internal organs (eg blood vessels, uterus, stomach, intestines, reproductive tract), Slow, sustained and tireless contraction (vasoconstriction, peristalsis, sphincters)

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4
Q

All muscles have the following abilities

A
  1. Contractibility – bones move, bringing attached points closer together. (skeletal)
    - reducing the space in heart chambers (cardiac)
    - decreasing diameter of alimentary canal moving contents along. (smooth)
  2. Extensibility- ability to be stretched
  3. Elasticity – ability to return to the original length after being stretched
  4. excitability- the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone.
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5
Q

Structure of skeletal muscle

A

Skeletal muscle is made up of bundles of muscle fiber, each of which contain myofibrils, which contain myofilaments of two types, actin and myosin

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6
Q

Fasicles

A

Muscle cells (muscle fibres) occur in bundles (fascicles) surrounded by a layer of tough connective tissue (perimysium). Fascicles are bound together by connective tissue to form the skeletal muscles.

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7
Q

connective tissue in the muscle bundles

A

A sheath of connective tissue surrounds each bundle so that it can function as an individual unit.
-allows adjacent bundles to slide easily over one another as they contract.
-each bundle join each other, and towards the end of the muscle they taper and blend to form the tendon.
- Amount of connective tissue increases with advancing age.

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8
Q

muscle cell and its surroundings

A

-a muscle bundle is composed of muscle cells that lie parallel to each other.
- Each muscle cell (muscle fibre) is an elongated cylinder with many nuclei.
-Around the cell is a thin, transparent plasma membrane, the sarcolemma, containing cytoplasm, called the sarcoplasm.

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9
Q

Structure of Myofibrils

A

Within the sarcoplasm of each fibre there are thread-like myofibrils
-sarcoplasmic reticulum surrounds the myofibrils. This is a storage site for calcium ions, which are released during muscle contractions.
-Each myofibril is composed of many smaller myofilaments, made of protein, which are the actual units involved in contraction of the muscle.
- Myosin (thick)
- Actin (thin)

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10
Q

How do muscles look striated

A

Myofibrils are divided into sarcomeres (actin – thin and myosin- thick give the myofibril a banded appearance). These bands give the skeletal and cardiac muscle a striated appearance (under microscope).

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11
Q

how do muscles work

A

Muscle properties of excitability, contractibility, extensibility and elasticity. Muscles are able to be:

  • stimulated by a nerve impulse.
  • shorten in length.
  • be stretched.
  • return to their original length.
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12
Q

Bands, zones and lines in the muscle

A

Z lines – protein discs in the middle of the thin filaments.
Sarcomere – distance between successive Z lines.
A Band – Myosin. (Length of thick filament)
At ends of the A band, the thin and thick filaments overlap – Dark.
H zone - Middle of band is lighter as only contains myosin.
I Band – distance between successive thick filaments (only contains actin: thin filaments.)

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13
Q

How do z lines shorten

A

When muscles contract, sarcomeres shorten.
Due to actin and myosin filaments sliding over one another. As the thin actin filaments slide over the thick myosin filaments, the Z lines are drawn closer together and the sarcomere is shortened. Results in shortening the muscle fibres, which then shortens the whole muscle.

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14
Q

Myofibril

A

Bundles of myofilaments. Myofibrils are aligned to give distinct bands
I band = light band
A band = dark band

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15
Q

Sarcomere

A

Contractile unit of a muscle fibre- Shortening of the sarcomeres in a myofibril produces the shortening of the myofibril

Thick filaments = myosin filaments
Composed of the protein myosin
Has ATPase enzymes
Thin filaments = actin filaments
Composed of the protein actin

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16
Q

What do actin and myosin do

A

Muscle cells contain the proteins actin and myosin. These proteins enable the cells to shorten. Because the muscles are anchored to bones this contraction produces movement.
Myosin filaments have heads (extensions, or cross bridges), Myosin and actin overlap somewhat

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17
Q

Sliding filament theory

A

Action potential arrives at axon terminal, voltage dependent calcium channels open and Ca2+ ions flow from extracellular fluid into motor neurone’s cytoplasm.

Calcium exposes the binding sites where Tropian and Tropomysin are attached on the actin site and the calcium is produced/ released from the motor neuron.

Energy released by breakdown of ATP causes change in shape of the myosin heads (crossbridges), resulting in a bending action (power stroke)

This causes the actin filaments to slide past the myosin filaments towards the centre of the sarcomere.

Repeated cycles of myosin heads (crossbridges) bind, pivot + dettach, powered by breakdown of ATP.

If Ca2+ and ATP are no longer available the actin and myosin go back to the orginal resting state.

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18
Q

What does the breakdown of ATP do

A

The breakdown of ATP deforms the heads of the myosin molecules. The simultaneous deformation of millions of myosin heads causes the myosin filament to crawl along the actin filament, rather like a ratchet, resulting in the muscle cell getting shorter (contracting).

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19
Q

Skeletal muscles working together

A

Muscles are attached to the bones of the skeleton by fibrous, inelastic connective tissue called tendons. Tendons bridge the joints so when muscles contract, bones move.

Most skeletal muscles work antagonistically in pairs or groups. When the flexor/abductor muscle contracts, the antagonistic extensor/adductor muscle relaxes, and vice versa.
Agonist (prime mover) – muscle with the major responsibility for a certain movement. (contracts)
Antagonist – muscle that opposes or reverses a prime mover.(relaxes and lengthens)

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20
Q

Muscle attachment points

A

Muscles are attached to at least two points
Origin – attachment to a non-moving (stationary) bone
Insertion – attachment to a movable bone

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21
Q

Synergists and fixator

A

Synergists – muscles that aids a prime mover in a movement and helps prevent rotation (steady the joint) eg. Synergistic muscles immobilize the wrist, stopping it from flexing.

Fixator – when a synergist immobilises a joint. It acts as a stabilizer of one part of the body during movement of another part.

Interaction of agonists, antagonists + synergists makes very fine + precise movements possible.

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22
Q

Muscle tone

A

Muscle tone is maintaining partial contraction of skeletal muscles.

Different fibres contract at different times to provide muscle tone eg head being held up. The process of stimulating various fibres is under involuntary control.

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23
Q

Skeletal system is made up of

A

-bones and associated structures
- tendons
- ligaments
- joints

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24
Q

Function of the skeleton

A

Support – firm framework supporting many soft tissues.
Movement (articulation) – acts as an attachment point for muscles allowing movement to occur at the bone.
Protection – encases most vital organs.
Storage – minerals salts & fats. These can be distributed when required. Eg Ca in pregnant woman.
Blood cell Production – red marrow in spongy bone contains stem cells which can differentiate into different blood cells.

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25
Q

Axial Skeleton

A

bones that lie around central axis of the body.
- Provides main support for erect posture, protects CNS + organs in thorax.
Consists of: - Skull, Vertebral column (backbone) and Ribcage

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26
Q

Appendicular Skeleton: (appendages)

A

Pectoral girdle and Upper limbs

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27
Q

A long bone consists of

A

Diaphysis: (shaft) making up the main portion of the bone and is hollow with compact bone surrounding medullary cavity.

Epiphysis: the enlarged ends of the bone. Have compact bone on outside, but central region contains spongy bone.

Articular cartilage: covers each epiphysis (thin).

Medullary Cavity: used as fat storage site and is often called the yellow bone marrow cavity.

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28
Q

Periosteum

A

dense, white, fibrous covering on the outer surface of the bone. No periosteum at the joints, where the bone is covered with an articular cartilage.

29
Q

what are the two types of bone

A

Two types of bone – compact bone, which is very hard and dense, and spongy bone, which is porous, consisting of a network of small bony plates.

30
Q

Compact bone

A

Shaft of long bone (diaphysis)
Immediately below cartilage
On surface/outer layer of most bones

Function – strength/solidness/support/rigidity/stiffness and Provides a cavity for bone marrow.

31
Q

Cancellous Bone (spongy)

A

Heads of long bones/epiphysis
Irregular shaped bones
filled with red bone marrow
Within flat bones.
Function – Provide strength with lightness
- Spaces allow for lightness
- Lowers density
- Stores red bone marrow
- Shock absorption/elasticity

32
Q

Matrix in connective tissue

A

Bone is classified as a connective tissue.
-Connective tissue cells are separated from each other by lots of matrix (non-cellular material)
- In bone, inorganic salts of calcium and phosphate are deposited in the matrix (increase its rigidity and strength).

33
Q

Compact bone structure

A

Compact bone consists of units called osteons or Haversian systems. They run parallel to the long axis of the bone. Gives the bone its maximum strength.

34
Q

Each osteon has

A

A central canal (Haversian canal).
Concentric layers of bony matrix called lamellae.
Lacunae: Small spaces in the matrix between the lamellae.
Osteoblasts, are young, bone-forming cells, and osteocytes, are mature cells contained in cavities (lacunae).
A bone cell, or osteocyte, occupies each lacuna.
Tiny canals, known as canaliculi, run between the lacunae.
Projections from the bone cells enter the canaliculi and pass materials from cell to cell.

35
Q

Microscopic Structure of Spongy Bone

A

consists of an irregular arrangement of thin, bony plates (trabeculae) often filled with red marrow.
The bone cells occupy spaces in the trabeculae.
Lamellae are not arranged in concentric layers.
Nerves and blood vessels pass through irregular spaces in the matrix.

36
Q

Cartalige

A

Cartilage does not contain blood vessels, so all nutrition and waste removal for the cells depends on the diffusion through the matrix.

Slow healing tissue due to low vascularisation and chondrocytes having a slow rate of metabolism and cell division.

Blood supply to cartilage comes from blood vessels located in the inner layer of the perichondrium.
-Perichondrium is a fibrous membrane of connective tissue that covers external surface of cartilage (except on articular cartilage)

37
Q

Cartilage structure

A

Contains numerous fibres made of a protein called collagen. Protein fibres are embedded in a firm matrix of a protein–carbohydrate complex called Chondrin.

Functions as a structural support with fibres giving cartilage certain amount of flexibility .
-it is found on the surface of bones at the joints, in trachea, bronchi, forms nose, larynx and outer ear.

38
Q

Matrix in cartilage

A

Cartilage has a firm matrix in which collagen fibres are embedded. Within the matrix are spaces that contain the cartilage cells called chondroblasts.
Chondroblasts produce matrix and gradually become surrounded by it until they are trapped in small spaces called lacunae. Once this has occurred, they are considered to be mature – chondrocytes.

39
Q

Types of cartalige

A

Hyaline: densely/closely packed collagenous fibres throughout matrix. Very fine fibres (can’t see under light microscope)
-give cartilage strength and flexibility.
- e.g. rings of trachea + bronchi, articular cartilage (where 2 bones meet at a joint)

Elastic: conspicuous elastic fibres + collagenous fibres (similar to hyaline but not so close together.)
- Flexible elastic support (springy!)
- e.g. Pinna, nose

Fibrocartilage- parallel bundles of thick collagenous fibres, not very compacted. (course appearance)
- can be compressed slightly
- e.g. Intervertebral discs, pubic symphysis, knee joint (meniscus)

40
Q

Movement of bones

A

Can be classified according to:
-range of movement (functional classification) eg immovable, slightly movable, freely movable.
-type of connective tissue that binds joints together. (structural classification ) eg fibrous, cartilaginous or synovial.
3 types: - Fixed/fibrous (immovable)
- Cartilaginous (slightly movable)
- Synovial (freely movable)

41
Q

Fibrous or Fixed

A

No movement between bones. Fibrous connective tissue holds in place
eg. Sutures of skull
Between teeth and jaw

42
Q

Cartilaginous or slightly moveable

A

Held in place by cartilage, slight movement.
Pubic Symphysis (between 2 pelvic bones)
Between adjacent vertebrae
between ribs + sternum

43
Q

Synovial or Freely moveable

A

Large amount of movement, but limited by ligaments, tendons, muscles + adjoining bones.
Ball & Socket joint
b. Hinge joint
c. Pivot joint
d. Gliding joint
e. Saddle joint
f. Condyloid/ellipsoid joint

44
Q

Ball and Socket

A

Spherical head of one bone fits into a cup like cavity of another
Shoulder joint (head of humerus + scapula) hip joint (head of femur + pelvis

45
Q

Hinge joint

A

Allow movement in one plane only. Formed when convex surface fits into concave surface.
Elbow
Knee
Ankle
b/t fingers + toes

46
Q

Pivot joint

A

a rounded or pointed or conical end of 1 bone articulates with a ring partly formed by bone + partly by a ligament.
(1st two vertebrae (head rotates)
radius + ulna (elbow)

47
Q

Gliding joint

A

Allow movement in a side to side or back and forward motion. Restricted by ligaments or bony processes. Flat bones against each other.
sternum +clavicle

48
Q

Saddle joint

A

Two bones are saddle shape ie one is concave, other is convex fit together. Movement is both side to side and back and forth.
Thumb joins the palm of hand. (carpals)

49
Q

Condyloid or ellipsoid joint

A

One surface of bone slightly convex, fitting into slightly concave depression in another bone. Allow movement in 2 directions ie up and down and side to side.
Metatarsals and phalanges of toes

50
Q

Structure of a Synovial Joint

A

Synovial joint (Freely moveable joints) have a synovial cavity (space between the articulating surfaces of the bones). Synovial membrane surrounds the synovial cavity, with articular cartilage on the bone surfaces.

51
Q

Articular Capsule

A

– surrounds and encloses the joint.
- comprises of two layers:
fibrous capsule: dense, fibrous connective tissue
attached to periosteum of bones. Flexibility allows
movement at the joint, its strength resists dislocation. Holds the bones together.

synovial membrane: inner layer of capsule. Loose
connective tissue, with blood capillaries. Lines
entire joint cavity, except articular cartilages and
articular disc.

52
Q

Synovial fluid

A

– secreted by synovial membrane, fills synovial cavity.
- lubricates joint, provides nourishment for articular
cartilage. (fluid is egg white like) keeps articular surfaces apart.
- thin film over surfaces in capsule.
- Small amount of fluid in joint, but increases in injury causing swelling, discomfort.

53
Q

Articular cartilage

A

covers articulating surfaces.
Provides smooth surface for movement

54
Q
A

Articular discs (meniscus in knee) – fibrocartilage extending inward from the articular capsule.
- divide the synovial cavity into 2 cavities.
- Synovial fluid directed to areas most friction.
- Tearing of meniscus – torn cartilage

55
Q

Bursae

A

– sacs of synovial fluid
- prevent friction between bone and ligaments or tendon or between bone and skin.

56
Q

Several factors contribute to joint stability.

A
  1. fit of the articulating bones.
  2. strength of joint ligaments. Ie Hip joint
  3. muscle tension
57
Q

Movements of a joint

A

Flexion (bending): decreases the angle between the articulating bones.

Extension (straightening): increases the angle between the articulating bones.

Abduction: movement away from the midline of the body (lifting arms upwards away from the body)

Adduction: movement towards the midline of the body (returning the arms to the sides after abduction.

Rotation: movement of a bone around its long axis. Rotation of the humerus occurs when the palm is turned upwards by twisting the forearm from the shoulder.

Circumduction: conical movement of a limb extending from the joint (e.g. shoulder or hip) at which the movement is controlled. True circumduction allows for 360 degrees of movement.

58
Q

Osteoporosis

A

Osteoporosis is a bone disease most common in postmenopausal women.

It is characterised by a loss of bone tissue resulting in the bones becoming extremely porous and fragile – loss of trabeculae in spongy bone.
-Haversian/Central Canal increases in size and number.
-Reabsorbing more bone that what is being produced. Reduction in osteocytes.
-Loss of minerals such as calcium more quickly than it can be replaced leading to a loss of bone mass or density.

59
Q

Osteoporosis diagnosis

A

Osteoporosis most commonly results from a fall in oestrogen levels after menopause.
A drop in bone mineral density (BMD) can be detected using dual energy X-ray absorptiometry.

60
Q

Osteoporosis can be prevented by

A
  • weight bearing exercise
  • adequate intake of calcium in diet
  • adequate amount of Vitamin D (exposure to sunlight or diet)
    -Oestrogen replacement therapy in some situations
61
Q

Osteoporosis treatment

A

Lifestyle changes such as:
Weight bearing exercise
Using dietary supplements of calcium and vitamin D (sunlight or dietary intake)
Oestrogen replacement therapy in some situations

There are several medications effective in the management of osteoporosis, especially bisphosphonates.

62
Q

Bones most likely affected by osteoporosis

A

-vertebrae
- ribs
- pelvis
- wrist
- upper arm
Can result in: postural changes, muscle weakness, reduced height (hunchback) bone fractures and bone deformity of the spine.

63
Q

Osteoblasts- bone cells

A

Osteoblasts: build bone. Immature bone cells –
Production and mineralisation of bone matrix.
As new bone is formed, a few of the active
osteoblasts become trapped in the matrix
and eventually become osteocytes. Small cells with single nucleus. Deposit calcium into bone.

64
Q

Osteocytes- bone cells

A

mature bone cells found in open spaces in
bone called lacunae. Function is maintenance
of bone matrix or calcium homeostasis.

65
Q

Osteoclasts- bone cells

A

Breakdown bone. Release calcium into blood Large cells, multinucleated.

66
Q

Osteoarthritis

A

is a degenerative joint disease that occurs mainly in older people and is associated with ageing. Could be due to joint injury/overuse, obesity, hereditary, older age. More than 50% of people over the age of 50 report painful knee joints.
irritation of the joints, wear and abrasion, may also be involved.

67
Q

Symptoms

A

Symptoms often occur in middle age (most people will have some symptoms by 70) Up to age 55 effects men and women equally.
-pain
- stiffness or swollen joint
- pain more severe after exercise or weight bearing or pressure on joint.
- Rubbing, grating or crackling sound when move joint.

68
Q

Treatment

A

Weight control and exercise.
Physiotherapy to strengthen muscles around the joint. Surgery to re-align bones or joint replacement surgery.
Injections of hyaluronan, extracted from rooster combs, and glucosamine sulphate, are reported to have beneficial effects on the symptoms and progression of the disease.

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