muscle tissues

Question 1

what is muscle tissue specialised for

Answer 1

contraction

Question 2

what the three types of muscle tissue?

Answer 2

• skeletal
• cardiac
• smooth

Question 3

describe somatic muscle tissue

Answer 3

• voluntary control (conscious)
• striated structure
• skeletal muscle tissue

Question 4

describe autonomic muscle tissue

Answer 4

• involuntary control (unconscious)
• striated or non-striated
• cardiac muscle tissue (striated- only found in walls of heart to pump blood)
• smooth muscle tissue (non-striated- lines hollow organs to propel its contents through the organ)
• heartrate, breathing etc.

Question 5

what is striated muscle tissue?

Answer 5

features repeating functional units called sarcomeres which make up myofibrils

Question 6

what are the roles of skeletal muscle roles?

Answer 6

• voluntary (conscious) movement of skeleton
• involuntary (subconscious) control of balace/posture

Question 7

describe the cells in skeletal muscle tissue?

Answer 7

• often called fibres as they resemble fibres
• very long (up to 30cm), elongated, cylindrical cells
• they contain multiple periphically located nuclei which lie around the outside of the cell as the cells are packed with protein units (myofibrils) which are important for producing contractions

Question 8

what is each individual skeletal muscle made up of?

Answer 8

(classed as an organ)
- skeletal muscle tissue
- nervous tissue
- connective tissue
- blood vessels

Question 9

what is a fasicle?

Answer 9

a bundle of muscle fibres bound together via the endomysium tissue wrapped by perimysium

Question 10

what is the name for muscle fibres?

Answer 10

myocytes

Question 11

what is perimysium?

Answer 11

connective tissue

Question 12

what is the epimysium?

Answer 12

dense connective tissue which externally surrounds entire muscles

Question 13

what is the endomysium?

Answer 13

the innermost connective tissue which surrounds individual muscle fibres

Question 14

what are sarcomeres?

Answer 14

contractile units of skeletal muscle

Question 15

how do sarcomeres contract?

Answer 15

the sliding filament mechanism
- a conformational change causes the filaments to slide over each other causing the sarcomere to contract

Question 16

describe the electron-microscopic cell structure of skeletal muscle

Answer 16

• myofibrils composed of repeating protein units called myofilaments
• dark thicker bands (mysoin)
• light thinner bands (actin)
• z lines bisect light bands, dividing each myofibril into contractile units called sarcomeres

Question 17

what do somatic motor neurons do?

Answer 17

innervate (supply with nerves) skeletal muscle

(1 neuron innervates several muscle fibres)

Question 18

what makes up a motor unit?

Answer 18

a single motor neuron together with all the muscle fibres it innervates

Question 19

what is excitation-contraction coupling?

Answer 19

• the neuronal action potential is converted to a chemical messenger called acetylcholine at the neurotransmitter junction
• this is detected by receptors on the plasma membrane of muscle cells/fibres
• stimulates an action potential in muscle fibres which contract

Question 20

what happens at the neurotransmitter junction?

Answer 20

the synapse of a motor neuron interacts with a muscle fibre

Question 21

what is the sarcolemma and its role?

Answer 21

• the sarcolemma is the modified plasma membrane of skeletal muscle cells
• it ivagenates into sarcoplasm to form membranous T tubules
• T tubules propagate action potentials into the interior of the cell
• it is continuous with the extracellular space

Question 22

what does ivagenates mean?

Answer 22

pores into

Question 23

what is the sarcoplasmic reticulum?

Answer 23

• modified smooth endoplasmic reticulum
• Ca2+ is concentrated within in the sarcoplasmic reticulum when muscle cells are relaxed and is required for actin to interact with myosin to give contraction
• therefore, when muscle contraction isn’t wanted, the Ca2+ is kept away from the myofibrils

Question 24

what two things support synchronous contraction of sarcomeres?

Answer 24

sarcolemma and sarcoplasmic reticulum

Question 25

what is the function of cardiac muscle?

Answer 25

- specialised for continuous autonomous contractions - pumps blood through the cardiovascular system

Question 26

where is cardiac muscle found?

Answer 26

ONLY in the heart

Question 27

what is the structure of cardiac muscle?

Answer 27

- elongated, some branched, cylindrical cells - striated

Question 28

what are the three layers of the heart wall?

Answer 28

- pericardium- outer supporting tissue - myocardium- cardiac muscle tissue - endocardium- single layer of epithelial cells

Question 29

describe the histological structure of cardiac muscle

Answer 29

- branched structure of individual cardiac muscle cells - regular connective tissue supports its rich capillary network - intercalated discs anchor cardiac cells together

Question 30

what is the name for cardiac muscle cells?

Answer 30

cardiomyocytes

Question 31

what are intercalated discs?

Answer 31

- allow cardiomyocytes to function as syncytium (a single unit) - specialised intercellular junctions - contain desmosomes - contain gap junctions - found at adjoining edge of cariomyocytes

Question 32

what is the function of a gap junction?

Answer 32

allow ions and signals to pass from cell to cell

Question 33

what are the similarities between cardiac and skeletal muscle?

Answer 33

- identical arrangement of sarcomeres - striated - contain T tubules and sarcoplasmic reticulum - contain numerous mitochondria - contain glycogen and lipid granules - contraction occurs by sliding-filament mechanism

Question 34

what are the differences between cardiac and skeletal muscle?

Answer 34

- cardiac is autonomous contraction - SR of cardiac muscle slowly leaks Ca2+ - there are specialised cardiac muscle cells (the conducting system) - cardiac muscle cells have intercalated discs

Question 35

what do pacemaker cells do?

Answer 35

undergo spontaneous depolarisation which sets the basic heart rhythm

Question 36

describe the conducting system of the heart

Answer 36

- autonomous contraction - initiated at the sinoatrial node (pacemaker cells are found here) - left and right atria contract - atrioventricular node - atrioventricular bundle - purkinje fibres - ventricles contract pushing blood into aorta - cardiac muscle fibres

Question 37

what is the function of smooth muscle?

Answer 37

-specialised for continuous contractions - typically typically to propel lumen contents (peristalsis- wave of contraction and relaxation in gastrointestinal tract)

Question 38

where is smooth muscle found?

Answer 38

lining hollow organs

Question 39

describe the structure of smooth muscle cells

Answer 39

- elongated, spindle-shaped with tapered ends - single centrally located nuclei - no sarcomeres therefore non-striated muscle

Question 40

what is peristalsis?

Answer 40

involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward

Question 41

what is the gastrointestinal tract?

Answer 41

Muscular tube lined by a mucous membrane Two muscle layers at right angles Peristalsis is how food moves through the GI tract

Question 42

describe peristalsis in the GI

Answer 42

- Lined internally by epithelium called the mucosa/mucous membrane- 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. - Submucosa is directly beneath the mucosa - The muscularis propria is directly beneath the submucosa. 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. - The adventitia is directly below the muscularis propria. his outer layer of loose supporting tissue conducts the major vessels, nerves and contains variable adipose tissue. Where the gut lies within the abdominal cavity (peritoneal cavity), the adventitia is referred to as the serosa (visceral peritoneum) and is lined by a simple squamous epithelium known as mesothelium. - Muscular tube lined by a mucous membrane - Two smooth muscle layers at right angles- muscularis propria

Question 43

describe smooth muscle contraction

Answer 43

- No myofibils or sarcomeres - Actin and myosin arranged in a criss-cross lattice - Anchored to cytoplasm and cell membrane via dense bodies - In a relaxed state the cell is elongated (a) - Muscle cell becomes shortened and globular

Question 44

what is the parasympathetic ganglia?

Answer 44

layer between two different layers of muscle- it modulates the intensity of peristalsis

Question 45

what is desmin?

Answer 45

third type of filament which anchors actin and allows the myosin to slide over it, as this happens the cells shorten and twist (contract)- these contractions happen more slowly and use less energy