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Histology > Muscle tissue > Flashcards

Muscle tissue Flashcards

1
Q

Which types of muscle are specialised for contraction

A

Skeletal
Cardiac
Smooth

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2
Q

How is voluntary control mediated

A

By the somatic system via motoneurons

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3
Q

The (unconscious) autonomic system mediates which movement

A

Involuntary control

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4
Q

Muscles with a striped or banded appearance are referred to as…

A

Striated

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5
Q

classification of skeletal tissue

A

Somatic (voluntary) and striated

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6
Q

What muscle is striated but controlled by the autonomic system

A

Cardiac muscle

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7
Q

What is the non striated muscle tissue

A

Smooth muscle

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8
Q

What are the functions of skeletal muscle

A

Attached to skeleton, responsible for voluntary movement by moving bones in skeleton
Specialised for contractions that produce movement
Controls subconscious movement such as balance and posture

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9
Q

Make up under a microscope

A

Elongated (large), cylindrical cells (muscle fibres)
Multiple peripherally located nuclei (multinucleated) as skeletal muscle cells are full of protein units (myofibrils) containing repeating units of myofilaments leaving no room for nuclei
Main tissue type in skeletal muscle

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10
Q

Are muscles organs

A

yes

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11
Q

What is skeletal muscle composed of

A

Skeletal muscle tissue
Nervous tissue
Blood vessels
Connective tissues

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12
Q

What is the Epimysium

A

Dense irregular connective tissue which encases muscles separating them from other tissues and organs
Forms tendons along with other connective tissues to attach the muscle to bone

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13
Q

What are fascicles

A

Bundles of skeletal muscle cells encased in perimysium (connective tissue)

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14
Q

What is the endomysium

A

The innermost layer of connective tissue found in muscles surrounding each individual muscle fibre

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15
Q

How to identify skeletal muscle cross sections

A

-Individual muscle fibres separated by endomysium
-Grouped of muscle fibres grouped together in fasciculi
-Each fascicule surrounded by loose connective tissue called perimysium
-Entire muscle is externally surrounded by a dense connective epimysium
-Blood vessels and nerves spread throughout these connective tissues

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16
Q

How is skeletal muscle specialised for contraction

A

Each muscle fibre is packed full of numerous myofibrils
Arrangement of myofibrils gives rise to the striated appearance

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17
Q

Types of myofillaments

A

Actin
Myosin

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18
Q

Appearance of myofilaments

A

Actin is smaller thinner (light) while myosin is thicker (darker)

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19
Q

What causes banded appearance

A

Arrangement of actin and myosin

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20
Q

To what are actin filaments anchored

A

Z lines which depict the contractile units (sarcomere)

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21
Q

What are sarcomeres

A

The contractile units of skeletal muscle

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22
Q

What mechanism is used in muscle contraction

A

Sliding filament mechanism
A conformational change causes the filaments to slide over each other causing the sarcomere to shorten (contract)

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23
Q

What is a motor unit

A

A single motor neuron and all the muscle fibres it innervates

24
Q

What is a neuromuscular junction

A

Where the synapse of a motor neuron interacts with a muscle fibre

25
Q

What occurs at a nueromuscular junction

A

Neuronal action potential is converted to chemical messenger (acetylcholine) which is detected by receptors on muscle fibres and stimulates action potential in muscle fibres causing the muscle to contract EXCITATION- CONTRACTION coupling

26
Q

Modifications of muscular organelles

A

Sarcolemma (plasma membrane of skeletal muscle cells)
-Invaginates into sarcoplasm to form membranous T tubules (rapid distribution of depolarisation signal)
-Continuous with extracellular space

Sarcoplasmic reticulum
-Modified smooth ER
-Ca2+ conc (required for actin to interact with myosin so SR acts as store) within SR

Both help to distribute and coordinate the signals that are required for muscle contraction

27
Q

What is the function of cardiac muscle

A

-Specialised for continuous autonomous contractions
-Pumps blood through the cardiovascular system

28
Q

Describe the structure of cardiac muscle cells

A

Elongated, branched cylindrical cells
One or two centrally located nuclei
Striated

29
Q

How many layers does the heart wall have

A

3

30
Q

Name the layers of the heart wall

A

Pericardium: Outer supporting tissue layer
Myocardium: Cardiac muscle tissue
Endocardium: Single layer of endothelium cells

31
Q

What are cardiomyocytes

A

Cardiac muscle cells

32
Q

Histological structure of cardiac muscle

A

-Branched structure of individual cardiac muscle cells (cardiomyocytes)
-Reticular connective tissue supports rich capillary network
-Specialised intercellular junctions (intercalated discs) which anchor cardiac cells together

33
Q

What are the similarities between the structure of skeletal and cardiac muscle

A

-Identical arrangement of sarcomeres
-Contain T tubules and sarcoplasmic reticulum
-Numerous mitochondria
-Glycogen(G) and Lipid(L) granules
-Contraction by sliding-filament mechanism

34
Q

What type of respiration is the heart more reliant on

A

Aerobic respiration, which is why the cardiac muscle contains far more mitochondria than skeletal tissue

35
Q

Differences between skeletal and cardiac muscle

A

-Skeletal muscle is voluntary while cardiac muscle is autonomous (involuntary)
-The sarcoplasmic reticulum slowly leaks Ca2+ in cardiac muscle to allow the heart to automatically generate own action potentials while the skeletal muscle relies on external stimulus
-Cardiac muscle contains specialised cardiac muscle cells known as the conducting system which is responsible for delivering the contraction system to the cardiomyocytes
-Intercalated discs - allow cardiac muscle cells to function as syncytium (work as single unit)

(allows signal to spread through cardiomyocytes) gap junctions present at intercalated discs allows depolarisation signal to travel through neighbouring cells meaning each cell does not require stimulation

36
Q

Where are pacemaker cells found

A

Primarily at the sinoatrial node

37
Q

Which cardiac muscle cells can undergo spontaneous depolarisation and why

A

Pacemaker cells due to the slow leaking of calcium ions
They set the basic heart rhythm

38
Q

Movement of autonomous contraction through the heart

A

-Initiated at the sinoatrial node in pacemaker cells
-Left and right atria contract as the signal moves into the atrioventricular node
-Signal moves from node to the atrioventricular bundle (of His)
-Reaches the Purkinje fibres which relay signal to contract to the rest of the cardiac muscle cells which initiates contraction of ventricles which push blood up into aorta
-The cells of conducting system initiate and coordinate heart beat and pass signal to cardiomyocytes which produce powerful contractions to pump the blood

39
Q

Involuntary contraction occurs via….

A

Intrinsic/spontaneous contractile ability
-Pacemaker cells (Sino-atrial node)
-Slow release of Ca2+ from SR

Rate of inherent rhythm modulated by
-Autonomic nervous stimulation
-Hormonal stimulation

40
Q

Features of smooth muscle which aid in its function

A

-Specialised for continuous contractions
-typically to propel lumen contents - peristalsis

41
Q

Where is smooth muscle found

A

Lining hollow organs (Gastrointestinal tract)

42
Q

What is the structure of smooth muscle

A

-Elongated, spindle shaped cells with tapered ends
-Single centrally located nuclei
-No sarcomeres hence no striations

43
Q

What is peristalsis

A

movement (contractions) of food through the GI tract

44
Q

Structure of the gastrointestinal tract

A

A muscular tube lined by a mucous membrane
Two muscle layers at right angle

45
Q

Action of smooth muscle for peristalsis

A

-Anatomical arrangement specialised for peristalsis
-Inner circular layer constricts lumen diameter
-Outer longitudinal layer shortens length
-Squeeze food through GI tract
-Parasympathetic ganglia modulate intensity of peristalsis

46
Q

What smooth muscle layers form the bowel wall

A

CM - inner circular layer
LM - outer longitudinal layer
PG - parasympathetic ganglia (parasympathetic nerve cell bodies which regulate and control intensity of peristalsis contractions)

47
Q

Structure of smooth muscle cells in comparison to skeletal and cardiac

A

-No T tubules, myofibrils or sarcomeres (non striated)
-Actin and myosin are arranged in a criss-cross lattice
-Anchored to cytoplasm and cell membrane via dense bodies
-Ina relaxed state the cell is elongated
-When contracted the muscle cell becomes shortened and globular

48
Q

What is the third type of filament found in smooth muscle cells

A

Intermediate filament (desmin)
helps to anchor the actin

49
Q

Which type of muscle has the slowest contractions using the least energy

A

smooth muscle

50
Q

What name is given to the innermost layer (luminal surface) that is composed predominantly of epithelium?

A

Mucosa
The mucosa is made up of three components: the epithelium, a
supporting lamina propria and a thin smooth muscle layer, the muscularis
mucosae, which produces local movement and folding of the mucosa.

51
Q

What layer of tissue supports the mucosa and contains larger blood vessels, lymphatics and nerves

A

Submucosa

52
Q

Name the layer of smooth muscle beneath the submucosa in the small intestine

A

Muscularis propria
The muscular wall proper consists of
smooth muscle that is usually arranged as an inner circular layer and an outer
longitudinal layer. In the stomach only, there is an inner oblique layer of
muscle. The action of the two layers, at right angles to one another, is the
basis of peristaltic contraction.

53
Q

Name the outer layer of loose supporting tissue lining the outside of the small intestine

A

Adventitia (protective tissue layer)

54
Q

What is the name for the mucous secreting cells lining the lumen of the small intestine

A

Goblet cells

55
Q

Why is it called smooth muscle

A

The contractile proteins lack the obvious organised structure of striated muscle.

56
Q

What name is used to describe this arrangement of muscle fibres

A

Fasciculi
The individual muscle cells (muscle fibres) are grouped together
into elongated bundles called fasciculi or fascicles with delicate supporting
tissue called endomysium occupying the spaces between individual muscle fibres.

57
Q

What is the name given to the layer of connective tissue surrounding each fascicle in skeletal muscle

A

Perimysium

Histology (9 decks)

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