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Anatomy & Physiology > Muscle Anatomy & Physiology > Flashcards

Muscle Anatomy & Physiology Flashcards

1
Q

What are the 3 types of muscle ?

A
  1. skeletal
  2. cardiac
  3. smooth
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2
Q

Define skeletal muscle

A

moves muscles attached to bone, voluntary & striated

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3
Q

Define cardiac muscle

A

heart muscle, involuntary, striated & auto-rhythmicity

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4
Q

Define smooth muscle

A

non-striated, involuntary, elements of auto-rhythmicity

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5
Q

What are the properties of muscular tissue ?

A
  • excitability
  • extensibility
  • contractility
  • elasticity
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5
Q

What are some basic functions of muscles ?

A
  • body movement
  • postural stability
  • storage & movement of substances
  • heat generation
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6
Q

Define Extensibility

A
  • stretch without being damaged –> smooth muscle experiences this in the stomach as it fills
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7
Q

Define Excitability

A
  • action potentials via innervation of muscle
  • triggered by auto rhythmic nature of the heart & chemical stimuli via neurotransmitters
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8
Q

Define contractility

A
  • generation of force as an output from an action potential
  • contraction generates tension as the muscle pulls on its attachment points
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9
Q

Define elasticity

A

ability to return to original shape and conformation following muscle contraction

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10
Q

How is skeletal muscle developed ?

A
  • zygote cleaved into an 8 stage cell
  • 8 stage cell is cleaved into a blastula
  • Blastula under goes gastrulation to create blastopore
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11
Q

What are the 3 layers of an embryo ?

A

Outer = Ectoderm
Middle = Mesoderm
Inner = Endoderm

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12
Q

Describe the ectoderm

A
  • epidermis skin & its derivatives (sweat glands & hair follicles)
  • nervous & sensory systems
  • pituitary gland & adrenal medulla
  • jaws & teeth
  • germ cells
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13
Q

Describe the mesoderm

A
  • skeletal & muscular systems
  • circulatory & lymphatic
  • excretory & reproductive systems
  • dermis of skin
  • adrenal cortex
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14
Q

Describe the endoderm

A
  • epithelial lining of digestive tracts & associated organs
  • thymus, thyroid & parathyroid glands
  • epithelial lining of respiratory, excretory & reproductive tracts/ducts
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15
Q

How are skeletal muscles organised ?

A

muscle (epimysium)
fascicle (perimysium)
muscle fibre (sarcolemma)
myofibril (sarcomere)
myofilaments (actin & myosin)

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16
Q

Define epimysium

A

layer covering the whole muscle

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17
Q

Define perimysium

A

surrounds 10-100 fibres

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18
Q

What is a fascicle ?

A

a bundle of fibres

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19
Q

Describe the nerve & blood supply in skeletal muscle tissue

A
  • artery with 1/2 veins accompany each nerve that penetrates the muscle
  • each fibre is innervated to form an NMJ (neuromuscular junction)
  • blood supply via capillary network, supply of oxygen & nutrients
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20
Q

What is the microscopic anatomy of skeletal muscle tissue ?

A
  • diameter = 10-100 um
  • length = 10-30cm
  • multi-nucleated
  • fibre number is set at birth
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21
Q

Define hypertrophy

A
  • increase in fibre size,
  • HGH and testosterone promotes muscle growth
22
Q

Define atrophy

A

reduction in fibre size , typically caused by disease, disuse and ageing

23
Q

What is the sarcolemma ?

A

the plasma membrane of the muscle cell

24
Q

What are T-tubules ?

A

invagination of the sarcolemma, involved in AP propagation

25
Q

What is the sarcoplasm?

A

cytoplasm of the muscle fibre

26
Q

What are myofibrils ?

A
  • contractile machinery of muscle -2mM in diameter
  • comprised of myosin & actin
27
Q

Describe the sarcoplasmic reticulum

A

network of ER which is specialised for skeletal muscle in Ca 2+ handling

28
Q

Describe the sarcomere

A
  • each myofibril has a striated pattern = sarcomere
  • basci unit of striated muscle tissue
  • repeating unit between 2 Z discs
  • ends of actin filaments are attached to a Z disc
  • length of sarcomere changes upon contraction
29
Q

What are the components of the sarcomere ?

A
  • contractile proteins
  • regulatory proteins
  • structural proteins
30
Q

Describe contractile proteins

A
  • generate force during contraction
  • example = actin & myosin
31
Q

Describe regulatory proteins

A
  • helps switch the contraction process on/off
  • troponin & tropomyosin = example
32
Q

Describe structural proteins

A
  • maintain the structure integrity of the sarcomere
  • examples = Titin, alpha actin and myomesin
33
Q

Describe the process of muscle contraction

A
  • action potential travels along the nerve axon
  • ends at the synaptic terminal
  • synaptic terminal releases neurotransmitter acetylcholine into the synaptic cleft
34
Q

Describe a motor unit

A
  • consists of a somatic motor neurone plus all the skeletal muscle fibres it stimulates
35
Q

What is the process of muscle contraction ?

A
  1. ACh is released, binding to reception on the motor end plate
  2. action potential reaches the T tubule
  3. sarcoplasmic reticulum releases Ca2+
  4. active site exposure, cross bridge formation
  5. contraction begins
36
Q

What is the process of muscle relaxation?

A
  1. Aceltycholine is broken down by AChE
  2. Sarcoplasmic reticulum recaptures Ca2+
  3. active sites are covered, no cross bridge interaction
  4. contraction ends
  5. relaxation occurs, passive return to resting length
37
Q

Describe muscle contraction in regards to myosin & actin

A
  1. myosin heads hydrolyse ATP and become reoriented & energised
  2. myosin heads bind to actin, forming cross bridges
  3. myosin cross bridges rotate centre of the sarcomere
  4. as myosin heads bind ATP the cross bridges detach from actin
38
Q

Where does energy for muscle contraction come from?

A
  • muscle contraction is a cyclical process which relies on a supply of key substrates = ATP & Ions (Ca2+)
39
Q

What are the 3 types of skeletal muscle fibres ?

A
  • slow oxidative - type 1
  • fast oxidative/glyolytic - type 2a
  • fast glycolytic - type 2b
40
Q

What are the 2 main types of smooth muscle ?

A
  1. multi-unit smooth muscle
  2. unitary smooth muscle
41
Q

What are the functions of smooth muscle ?

A
  • vascular tone
  • peristalsis
  • pupil constriction/dilation
42
Q

Define peristalsis

A

movement of food down the digestive tract

43
Q

Describe the general structure of smooth muscle

A
  • single, centrally places nucleus
  • spindle (fusiform) shape
  • not-striated
  • actin filaments attached to dense bodies
  • myosin filaments are interspersed in the actin
44
Q

Describe the structure of multi-unit smooth muscle

A
  • composed of discrete, separate smooth muscle fibres
  • each fibre operates independently of the others, innervated by a single nerve ending
  • covered by a thin basement membrane composed of fine collagen & glycoproteins
  • controlled by nerve signals
45
Q

What are some examples of multi-unit smooth muscle ?

A
  • iris muscle of the eye
  • piloerector muscle - erection of hairs upon sympathetic NS stimulation
46
Q

Physiology of Smooth Muscle

A
  • principles of contraction are similar to SKM = Ca2+
  • smooth muscle contracts & relaxes in response to action potentials from the ANS
  • responsive to changes in hormones, pH, temp and ion conc. at a local level
47
Q

What 3 types of cardiac muscle make up the heart?

A
  • atrial muscle
  • ventricular muscle
  • excitatory & conductive muscle fibres
48
Q

How do excitatory & conductive muscle fibres contract ?

A
  • feebly due to few contractile fibrils
49
Q

Describe the structure of the cardiac muscle

A
  • fibres arranged in a latticework
  • striated appearance
  • dark area crossing fibres = intercalated disc
50
Q

What are intercalated discs ?

A

cells that separate individual cardiac muscle cells
- at each intercalated disc cell membrane fuse together
- gap junctions allow for rapid diffusion of ions

51
Q

What are the 2 syncytiums of the heart ?

A
  • atrial - 2 walls of the atria
  • ventricular - 2 walls of the ventricles
52
Q

What does the 2 syncytiums allows ?

A

they allow atria to contract a short time ahead of the ventricular contractions

Anatomy & Physiology (15 decks)

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