muscle histology

Question 1

why do smooth muscles appear unstriated

Answer 1

because their myofibrils are not in a regular arrangment

Question 2

describe the cell structure of a muscle cell

Answer 2

its a long unbranched cylindrical cell with peripheral nuclei - potentially multinucleated. striated appearance

Question 3

why are the nuclei of skeletal muscle fibers peripheral

Answer 3

due to the myofibrils in the cell

Question 4

are there organelles in a skeletal muscle cell

Answer 4

yes there are, they are just squished between the myofibrils

Question 5

what is around the sarcolemma

Answer 5

a basal lamina and then the endomysium

Question 6

what organelle is the sarcoplasmic reticulum

Answer 6

it is the smooth endoplasmic reticulum of the muscle cells

Question 7

what makes up a T triad

Answer 7

a t triad is 2 of the terminal swellings of the sarcoplasmic reticulum - the terminal cisternae, and a t tubule

Question 8

whats important about the terminal cisternae

Answer 8

this is where the excitation of the AP is coupled to the muscle contraction. as this is where the serca pumps are and stuff, so muscle contraction is initiated here.

Question 9

in the myofibril geographies, where is the triad located

Answer 9

the A band

Question 10

what is the space between the myosin heads and either side of the Z line

Answer 10

the I band- the blank space really

Question 11

whats the H band

Answer 11

the parts where we only find the myosin filaments

Question 12

what is the A band

Answer 12

the space where there is the myosin plus the overlap of the actin. so parts where its myosin plus actin, but also plus the rest of the myosin

Question 13

during contraction, of the bands and all that jazz, what shortens what stays the same and shit

Answer 13

during contraction of the myofibril the Z disks get closer together. the A band stays the same thickness, the I band and the H band shortens.

Question 14

what does the dystrophin protein do

Answer 14

it connects actin filaments to the basal lamina

Question 15

what is muscular dystrophy

Answer 15

weakened contractions due to the defective dystrophin proteins.

Question 16

where is the muscle spindle

Answer 16

this is in the inner of the muscle, the intrafusal.

Question 17

what is the muscle spindle

Answer 17

specialised type of skeletal muscle within a connective tissue capsule - which itself is inside the muscle fascicle

Question 18

the capsule of the muscle spindle is an extension from what

Answer 18

extension of connective tissue from the perimysium

Question 19

what is the function of the muscle spindle and how do they do this

Answer 19

these are key in proprioception,
there will be stretch signal in the muscle spindle, this force is converted to the capsule then the nerve endings, this is sent to the spinal cord and back. the motor information back is to the extrafusal muscle to engage the muscles in some activity to prevent too greater tension on the connective tissues

Question 20

where are the muscle sateillite cells and what do they do

Answer 20

these are found on the cell periphery and they are between the sarcolemma and the basal lamina. normally inactive but in acute muscle injury they act as a muscle stem cell, helping repair the damaged muscles

Question 21

tell me about the type one muscle fibres

Answer 21

these are the slow twitch oxidative muscle fibers. these get their energy to contract from aerobic oxidation of fats. hence have many mitochondria and many capillaries to maintain blood supply. hence they are red in colour. these are used in long term activity - fatigue resistant - postural muscles for example

Question 22

describe the type 2 muscle fibres

Answer 22

these are your white, fast twitch muscle fibres. these get their energy from anaerobic glycolysis. they have few mitochondria and capillaries. have granules of glycogen stores. they break down this glycogen quickly when activity us needed. but once this glycogen is used they need rest period to restore the glycogen and ph - as lactic acid was made