muscles PART 1 [types of muscles and structure of skeletal muscle]

key terms for muscle structure (2)

-multinucleate or uninucleate

-striated

types of muscle

→found where?

→function

→structure

→arrangement

→contraction speed and contraction duration

→control

CARDIAC MUSCLE

found where?

-found only in the heart

function

-contracts to pump blood around the body

structure

-striated (fainter than skeletal)

-contain branched cells

-fibres are uninucleate

-fibres are connected by intercalated discs

arrangement

-arranged in a branched network

contraction speed and contraction length

-intermediate contraction speed

-intermediate contraction length

control

-involuntary

SKELETAL MUSCLE (voluntary muscle)

found where?

-attached to bone e.g. found intercoastal muscle (between the ribs)

function

-moves bones to allow movement

structure

-striated due to bands of actin & myosin

-contain cylindrical cells

-fibres are multinucleate

arrangement

-regular and parallel arrangement of fibres so muscle contraction occurs in one direction

contraction speed and contraction length

-fast contraction speed

-short contraction length

control

-voluntary

INVOLUNTARY MUSCLE (smooth muscle)

found where?

-bronchioles, arteries etc [airways, blood vessels]

function

-control diameter of bronchioles

-controls pupil size

-involved in peristalsis

structure

-unstriated [tip: smooth so no stripes]

-contain long spindle-shaped cells

-fibres are uninucleate

arrangement

-no regular arrangement of fibres so muscle contraction occurs in different directions

contraction speed and contraction length

-slow contraction speed

-long contraction length

control

-involuntary

why are cardiac muscle fibres branched?

to allow nerve impulses to spread quickly through the muscle

name muscles [microscope images]

labelled cardiac muscle

[intercalated discs are the faint lines that connect the fibres]

skeletal muscle consists of what

bundles of long, cylindrical muscle fibres

how are muscle fibres formed and why?

cells fuse together to form long muscle fibres, ensuring there's no points of weakness between cells and allows contraction over a greater distance

what do muscle fibres contain? (5)

label diagram

myofibrils

sarcolemma- plasma membrane of muscle fibre

sarcoplasm- cytoplasm of muscle fibre

mitochondria

sarcoplasmic reticulum

what are myofibrils made of

made up of repeating units called sarcomeres

what do sarcomeres contain? [describe structures]

contains protein filaments:

myosin

→thick myofilament [tip: has more letters= thick]

→rod shaped with bulbous heads

actin

→thin myofilament

→two strands twisted around each other

A band (dark band)

-contains myosin and overlapping actin filaments [tip: dark= A band]

I band (light band)

-contains only actin filaments [tip: light= I band]

Z line

-marks the ends of each sarcomere (central line within the I band)

M line

-central line of sarcomere

H zone

-contains only myosin filaments

what happens to patterns when skeletal muscle contracts?

-Z line moves closer

-sarcomere becomes shorter

-A band remains the same size [myosin filaments do not shorten]

-I band and H zone become smaller

why does H zone become smaller?

-contains only myosin

-during contraction, actin filaments are pulled closer by myosin, increasing the overlap between actin and myosin

Why A and I bands appear different under a microscope

A band contains myosin filaments

I band contains only actin filaments