chapter 8 - purely muscles Flashcards
what are the three types of muscles
skeletal, smooth and cardiac
elaborate on skeletal muscles
move bones and enable us to walk, run etc.
voluntary
attached to the bones of the skeleton
elaborate on smooth muscles
involuntary
wrap around alimentary canal and contract to decrease the diameter of the canal
elaborate on cardiac muscles
heart muscle
involuntary
upon contraction, chambers of the heart decrease, pushing blood from the heart into vessels
what are the properties of muscles?
- excitability
- contractibility
- extensibility
- elasticity
structure of skeletal muscles (muscle bundles)
muscle cells are held together in muscle bundles
sheath of connective tissue (perimysium) surrounds each bundle to help it function as a unit
perimysium allows adjacent bundles to slide easily over one another as they contract
sheaths of connective tissue (epimysium) hold bundles together, towards the end of the muscle they taper and blend to form the tendon
connective tissue increases with…?
age
structure of muscle fibres
a muscle bundle is composed of muscle cells (muscle fibres) that lie parallel to each other in an elongated cylinder with many nuclei
around each muscle fibre is a thin, transparent plasma membrane (sarcolemma) containing cytoplasm (sarcoplasm)
between 10 and 100 micrometers in diameter and vary in length from a few mm to several cm
structure of myofibrils
thread like structures found within the sarcoplasm of each fibre
lie parallel to each other and run the length of the fibre
tubular network called sarcoplasmic reticulum surrounds the myofibrils (a storage site for Ca2+, which is released to initiate muscle contraction)
each is composed of many smaller myofilaments, which are made up of protein - myosin and actin
difference between the two units of muscle contraction
mysosin - thick myofilament
actin - thin filament
what happens when a muscle fibre is supplied with sufficient energy and is activated by a nerve impulse?
actin and myosin myofilaments slide past each other in a manner that shortens the myofibril
what give muscle its banded appearance
the arrangement of actin and myosin
define excitability
muscles are stimulated by nerve impulses
define contractibility
muscles are able to shorten in length
define extensibility
muscles are able to be stretched
define elasticity
muscles are able to return to their original length
explain the sliding filament theory
the theory suggests that when muscles contract the sarcomeres shorten due to actin and myosin myofilaments sliding over each other
at any given time, some muscle fibres can be contrasted while others are relaxed
energy is required ton initiate muscle contraction
what are muscles attached to bone by?
muscles are attached to bones by fibrous, inelastic connective tissue called tendons
they’re attached to the bone in such a way that when muscles contract they move bone (muscles are said to be ‘bridge’ joints)
what are pairs of muscles referred to as
antagonists - meaning they have opposite reactions
eg. biceps and triceps or hamstrings and quadriceps
provide an example of antagonist pairs
the biceps and triceps are antagonist muscles. they produce movements that are opposite. the triceps straightens the arm and the biceps bend the arm.
when thew biceps contract to bend the arm, the triceps must relax; the opposite occurs when the arm is straightened
define origin
the end of the muscle attached to the stationary bone.
define insertion
the end of the muscle fixed to the moveable bone
what is the agonist?
a muscle that produces the desired movement or action
also called the prime mover
what are synergists?
they’re muscles that help the prime mover.
synergists may:
- produce the same movement as the prime mover
- steady a joint during a particular movement to prevent unwanted movement
provide an example of a synergist being a fixator
eg the wrist would flex each time the fist was clenched if not for the synergist muscles
when a synergist immobilises a joint it is called a fixator
what is muscle tone
maintaining partial contraction of skeletal muscles
at any one time, some muscle fibres are contracted and some are relaxed. such partial contraction tightens a muscle with not enough force produced for movement.
eg. the partial contraction of muscles in the neck hold the head up.
