Muscle histology wk3

Question 1

what are muscle functions?

Answer 1

• survival (heart beat)
• movement
• moving substances through the body
• for speech/communication, chewing, posture, circulation, urination

Question 2

overview of skeletal muscle

Answer 2

• voluntary, under conscious control - somatic nervous system
• specialised for rapid contraction of short duration
• striated

Question 3

overview of smooth muscle

Answer 3

• found in vessels, GI tract, uterus and bladder
• involuntary
• non-striated

Question 4

overview of cardiac muscle

Answer 4

• found only in heart (myocardium)
• involuntary
• rate and force of contraction regulated by ANS
• striated

Question 5

how do you identify cardiac muscle?

Answer 5

central nuclei, broader, more dense areas that split up cardiomyocytes

Question 6

what is the structure of skeletal muscle?

Answer 6

• muscle is made of several fascicles surrounded by a sense collagenous sheath - epimysium
• fascicles is surrounded by loose collagenous tissue - perimysium
• fascicles is made of many individual muscle cells/fibres
• these calls are held together by supporting tissue endomysium

Question 7

histology of a muscle spindle

Answer 7

extrafusal muscle fibres - cause contraction
intrafusal muscle fibres (smaller) - surrounded by capsule
sensory nerve wraps around to detect amount of stretch
important in muscle tone and stretch reflexes

Question 8

structures of inside muscles

Answer 8

muscles ==> fascicles ==> muscle fibres ==> myofibrils

Question 9

what are dark and light bands in muscle fibres?

Answer 9

dark - both actin and myosin (thick filaments) present

light - only actin (thin filaments) present

Question 10

what is the repeating functional unit of a myofibril?

Answer 10

sarcomere

Question 11

what is sliding filament theory?

Answer 11

• under control of action potential

- sarcomere shortens so whole muscle shortens but filament does not

Question 12

define sarcoplasm

Answer 12

cytoplasm of muscle cells

Question 13

define sarcolemma

Answer 13

plasma membrane

Question 14

what is sarcoplasmic reticulum?

Answer 14

derived from SER acts as a calcium reservoir. found between t tubules

Question 15

what are t tubules?

Answer 15

• formed by invagination of sarcolemma and is around each myofibril
• forms internal network
• allows all myofibrils to contract at once as the depolarisation spreads rather than slowly travelling from area to area

Question 16

what is the neuromuscular junction?

Answer 16

• presynaptic membrane filled with synaptic vesicles filled with ACh neurotransmitter

Question 17

what is the structure of the tongue?

Answer 17

• tongue has muscle fascicles in different orientations
• transverse sections (chunks) and longitudinal sections (longggg)
• some perimysium between fasciculi
• other tissue includes adipose, glandular tissue, blood vessels and nervous tissue

Question 18

what are mitochondrial assays?

Answer 18

• assays demonstrate the activity of mitochondria within muscle fibres
• dark:aerobic fibres, type 1 (slow twitch)
• grey: intermediate fibres type IIA (fast twitch)
• light: anaerobic fibres type IIB (fast twitch)

Question 19

overview of type I/slow twitch (aerobic)

Answer 19

• large amounts of mitochondria and myoglobin
• smaller diameter, rich blood supply
• fibres maintain continuous contraction
• for muscles used all the time e.g. posture

Question 20

overview of type IIB/fast twitch (anaerobic)

Answer 20

• contracts more rapidly due to faster myosin
• little mitochondria/myoglobin (white)
• glycogen - glycolysis
• for muscles for intense but sporadic contraction - extra-ocular muscles

Question 21

overview of type IIA/fast twitch (intermediate)

Answer 21

• more mitochondria/myoglobin (red)

- aerobic and anaerobic respiration

Question 22

where is nicleus in cardiac muscle ?

Answer 22

central position

Question 23

what are intercalated discs?

Answer 23

• contains gap junctions, desmosomes, adhering junctions
• all rapid spread of contractile stimuli
• allow physical and electrical connections
• many mitochondria present
• when one cardiomyocyte contracts, so does the next one

Question 24

What do smooth muscle cells have?

Answer 24

• single central nucleus
• spindle shaped
• non striated - arrangement of sarcomeres are in separate directions
• cells connected by gap junctions

Question 25

What are satellite cells?

Answer 25

• Involved in the maintenance, repair and regeneration of skeletal muscle cells

Question 26

What is the advantage of the nerve entering the muscle SGT nerve entry point being halfway between its origin and insertion?

Answer 26

Helps contraction - muscle shortens at its centre first, pulling extremities in both directions allowing even contraction