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Physical Health Sciences > Muscular System > Flashcards

Muscular System Flashcards

1
Q

What is the function of muscles?

A

To contract and shorten to enable movement

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2
Q

What are the 3 types of muscle cells?

A
  1. Skeletal
  2. Cardiac
  3. Smooth
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3
Q

Describe skeletal muscle cells

A
  • Attached to bones and skin
  • Contract in response to stimulation from the nervous system
  • Under voluntary control
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4
Q

What are the 2 points of the bone that skeletal muscles attach to?

A
  1. Origin (immovable)

2. Insertion (movable)

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5
Q

Give 5 properties of skeletal muscle cells

A
  1. Striations
  2. Long and large
  3. Cylindrical
  4. Hundreds of nuclei
  5. Lots of mitochondria
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6
Q

Describe cardiac muscle cells

A
  • Located in the walls of the heart
  • Called myocardium (which is myogenic - generates its own impulse)
  • Under involuntary control
  • Regulated by a pacemaker, the NS and hormone control
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7
Q

Give 6 properties of cardiac muscle cells

A
  1. Striations
  2. 1 nucleus
  3. Short, wide T-tubules
  4. Sarcoplasmic reticulum has no terminal cisternae
  5. Aerobic (high in myoglobin and mitochondria)
  6. Intercalated discs
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8
Q

Describe smooth muscle cells

A
  • Found in the walls of the respiratory tract, digestive system and ducts in glands
  • Under involuntary control (autonomic NS)
  • Regulated by NS, hormonal and chemical control
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9
Q

Give 7 properties of smooth muscle cells

A
  1. Not striated
  2. 1 nucleus
  3. No sarcomeres, T-tubules, myofibrils, tendons or aponeuroses
  4. Long, slender and spindle shaped
  5. Scattered myosin fibres which have more heads per thick filament
  6. Thin filaments attached to dense bodies which transmit contractions from cell to cell
  7. Intermediate filaments called desmin
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10
Q

Explain the difference between single-unit and multi-unit smooth muscle cells

A 
Single-unit = cells connected via gap junctions
Multi-unit = bundles of cells held together by a neurone
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11
Q

Give 4 examples of smooth muscle cells and where they are found

A
  • Integumentary system = arrector pilli muscles (cause goose bumps)
  • Cardiovascular + Respiratory systems = regulate BP and airflow
  • Reproductive + Glandular systems = produce movement
  • Digestive + Urinary systems = form sphincters and produce contractions
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12
Q

What is a sarcolemma?

A

A plasma membrane surrounding skeletal muscle cells

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13
Q

What is a sarcomere?

A

The basic unit or skeletal and cardiac muscle

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14
Q

What is a sarcoplasmic reticulum?

A

A specialised organelle that stores calcium

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15
Q

What are myofibrils?

A

Long organelles in the cytoplasm of muscle cells that hold the nuclei apart

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16
Q

Describe the structure of myofibrils

A
  • The light (I) bands and dark (A) bands give the muscle its striated appearance
  • The light (I) bands are made up of thin myofilaments and have a midline interruption called the Z line/disc which divides each sarcomere
  • The dark (A) bands are made up of mainly thick myofilaments and have a lighter central area called the H zone
  • The M line is the centre of the H zone and contains tiny protein rods that hold thick myofilaments together
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17
Q

Give the microscopic structure of muscle cells in order

A

Muscle cell –> Myofibril –> Sarcomere –> Thick and thin filaments

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18
Q

What are the thick and thin myofilaments made of?

A 
Thick = myosin
Thin = actin
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19
Q

Describe the structure of thick myofilaments

A
  • The mid-part of the filament is smooth but the end is studded; this is called the myosin head
  • Myosin heads form cross-bridges to link thick and thin filaments together during muscle contraction
  • Attached to the Z line by titin, which are elastic filaments that run through the core of the filament
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20
Q

What do thick myofilaments contain and why?

A

ATPase enzymes to release energy for muscle contraction

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21
Q

What do thin myofilaments contain and why?

A
  • Regulatory proteins that allow/prevent myosin heads binding to actin
  • Also contain tropomyosin and troponin
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22
Q

How are muscle fibres protected?

A
  • Each muscle fibre is enclosed in a delicate connective tissue sheath called Endomysium
  • Several sheathed fibres are then wrapped by a coarser fibrous membrane called Perimysium to form a bundle of fibres called a Fascicle
  • Many fascicles are bound together by tougher connective tissue called an Epimysium which covers the entire muscle
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23
Q

What is a motor unit?

A

A neurone and all the skeletal muscle fibres that it stimulates

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24
Q

What is a neuromuscular junction?

A

A junction between axon terminals and the sarcolemma of the next muscle cell

25
Q

What is a neurotransmitter?

A
  • A chemical in the synaptic vesicles of the neuromuscular junction
  • ACh (acetylcholine) is the neurotransmitter that stimulates skeletal muscle fibres
26
Q

What is a synaptic cleft?

A

The gap between the nerve endings and the muscle fibre membranes which is filled with interstitial fluid

27
Q

Describe how a muscle contractions happens

A
  • Initiated by an action potential from a motor neurone in the somatic NS
  • When contraction occurs, thick and thin filaments slide between each other, shortening the distance between the Z lines
28
Q

What are the 4 functional properties of muscle fibres?

A
  1. Irritability/ Responsiveness - the ability to receive and respond to a stimulus
  2. Contractility - the ability to forcibly shorten when adequately stimulated
  3. Extensibility - the ability to stretch
  4. Elasticity - the ability to recoil and resume resting length
29
Q

Describe steps 1-5 of the process of muscle contraction

A
  1. Nerve impulse reaches the axon terminal as an action potential
  2. Calcium channels open and calcium ions enter the axon terminal
  3. This causes some of the synaptic vesicles to fuse with the cell membrane and release ACh
  4. ACh diffuses across the synaptic cleft and attaches to membrane receptors in the highly folded regions of the sarcolemma
  5. Sarcolemma becomes temporarily more permeable to sodium ions (diffuse in to fibre) and potassium ions (diffuse out of fibre) - more sodium enters than potassium leaves
30
Q

Describe steps 6-9 of the process of muscle contraction

A
  1. Conc. gradient created means the interior of the cell has an excess of positive ions which reverses the resting electrical conditions of the sarcolemma (depolarisation)
  2. More sodium channels open and this movement of ions is called an action potential
  3. The action potential then spreads across the whole sarcolemma which causes contraction
  4. While the action potential is occurring, acetylecholinesterase (AChE), which is present in the synaptic cleft , breaks down ACh to acetic acid and choline to ensure that a single nerve impulse only produces one contraction
31
Q

Describe steps 1-3 of the journey of an action potential

A
  1. The action potential travels along the sarcolemma and down the T-tubules to the triads which triggers the release of calcium ions from the terminal cisternae of the sarcoplasmic reticulum into the cytoplasm
  2. The calcium ions bind to troponin which weakens the bond between actin and the troponin-tropomyosin complex
  3. The troponin molecules then change position, rolling the tropomyosin molecule away from the active sites on actin and allowing interaction with the energised myosin heads
32
Q

Describe steps 4-7 of the journey of an action potential

A
  1. Once the active sites are exposed, the myosin head binds to them, which forms cross-bridges
  2. The energy that was stored in the resting state is then released as the myosin head pivots towards the M line and the ADP + Pi are released; this is called the power stroke
  3. When another ATP molecule binds to the myosin head, the link between the head and the active site of actin is broken, meaning another cross-bridge can form
  4. Myosin reactivation occurs when the free myosin head splits ATP into ADP + Pi; the energy released is used to re-cock the myosin head
33
Q

What effect does myosin have on the action potential journey in step 3?

A

It converts ATP –> ADP + Pi to change the position of the head to a 90 degree angle

34
Q

What are the 4 functions of muscles?

A
  1. Movement - responsible for movement and response to changes in external environment
  2. Maintain Posture - make continuous adjustments
  3. Stabilise Joints - pull on bones to provide movement and stability
  4. Generate Heat - muscle activity generates heat due to the release of ATP
35
Q

What is an isometric contraction?

A

Muscle tension develops but the load is not moved

36
Q

What is an isotonic contraction?

A

Muscle tension develops and overcomes the load and muscle shortening occurs

37
Q

What determines how forcefully a muscle contracts?

A

The number of cells that are stimulated

38
Q

What are the 7 characteristics used to name muscles?

A
  1. Direction of muscle fibres
  2. Relative size of muscle
  3. Location of muscle
  4. Shape of muscle
  5. Number of origins
  6. Location of muscle origins and insertions
  7. Action of muscle
39
Q

What is muscle fatigue?

A

A state in which a muscle can no longer perform a required activity

40
Q

What happens as a result of muscle fatigue?

A
  • Depletion of metabolic reserves
  • Damage to sarcolemma and sarcoplasmic reticulum
  • Low pH (lactic acid is a waste product of ATP production)
  • Muscle exhaustion and pain
41
Q

What is force?

A

Maximum amount of tension produced

42
Q

What is endurance?

A

Amount of time an activity can be sustained for

43
Q

What affects the force and endurance of a muscle?

A

The type of muscle fibre and physical conditioning (exercise)

44
Q

What is the primary function of the Gluteus Maximus?

A

Extends hip (when forceful extension is required)

45
Q

What is the primary function of the Trapezius?

A

Raises, retracts and rotates scapula

46
Q

What is the primary function of the Deltoid?

A

Abducts humerus

47
Q

What is the primary function of the Pectoralis Major?

A

Adducts and flexes humerus

48
Q

What is the primary function of the Soleus?

A

Plantar flexes foot

49
Q

What is the primary function of the Latissimus Dorsi?

A

Extends and adducts humerus

50
Q

What is the primary function of the Rectus Abdominis?

A

Flexes vertebral column

51
Q

What is the primary function of the Gastrocnemius?

A

Plantar flexes foot and flexes knee

52
Q

What are the 3 types of Hamstring muscle and what is their primary function?

A
  1. Semi-tendinous
  2. Semi-membranous
  3. Biceps femoris
    - Flexes knee and extends hip
53
Q

What is the primary function of the Gluteus Medius?

A

Abducts thigh: steadies pelvis during walking

54
Q

What is the primary function of the Biceps Brachialis?

A

Flexes elbow and supinates forearm

55
Q

What is the primary function of the Triceps Brachii?

A

Extends elbow

56
Q

What is the primary function of the External Oblique?

A

Flexes and rotates vertebral column

57
Q

What is the primary function of the Sartorius?

A

Flexes thigh on hip

58
Q

What is the primary function of the Sternocleidomastoid?

A

Flexes neck; laterally rotates head

59
Q

What are the 4 muscles in the Quadriceps group and what is their primary function?

A
  1. Vastus medialis
  2. Intermedius
  3. Lateralis
  4. Rectus femoris
    - All extend knee: rectus femoris also flexes hip on thigh

Physical Health Sciences (15 decks)

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