chapter 8 - purely muscles

Question 1

what are the three types of muscles

Answer 1

skeletal, smooth and cardiac

Question 2

elaborate on skeletal muscles

Answer 2

move bones and enable us to walk, run etc.

voluntary

attached to the bones of the skeleton

Question 3

elaborate on smooth muscles

Answer 3

involuntary

wrap around alimentary canal and contract to decrease the diameter of the canal

Question 4

elaborate on cardiac muscles

Answer 4

heart muscle

involuntary

upon contraction, chambers of the heart decrease, pushing blood from the heart into vessels

Question 5

what are the properties of muscles?

Answer 5

• excitability
• contractibility
• extensibility
• elasticity

Question 6

structure of skeletal muscles (muscle bundles)

Answer 6

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

Question 7

connective tissue increases with…?

Answer 7

age

Question 8

structure of muscle fibres

Answer 8

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

Question 9

structure of myofibrils

Answer 9

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

Question 10

difference between the two units of muscle contraction

Answer 10

mysosin - thick myofilament

actin - thin filament

Question 11

what happens when a muscle fibre is supplied with sufficient energy and is activated by a nerve impulse?

Answer 11

actin and myosin myofilaments slide past each other in a manner that shortens the myofibril

Question 12

what give muscle its banded appearance

Answer 12

the arrangement of actin and myosin

Question 13

define excitability

Answer 13

muscles are stimulated by nerve impulses

Question 14

define contractibility

Answer 14

muscles are able to shorten in length

Question 15

define extensibility

Answer 15

muscles are able to be stretched

Question 16

define elasticity

Answer 16

muscles are able to return to their original length

Question 17

explain the sliding filament theory

Answer 17

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

Question 18

what are muscles attached to bone by?

Answer 18

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)

Question 19

what are pairs of muscles referred to as

Answer 19

antagonists - meaning they have opposite reactions

eg. biceps and triceps or hamstrings and quadriceps

Question 20

provide an example of antagonist pairs

Answer 20

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

Question 21

define origin

Answer 21

the end of the muscle attached to the stationary bone.

Question 22

define insertion

Answer 22

the end of the muscle fixed to the moveable bone

Question 23

what is the agonist?

Answer 23

a muscle that produces the desired movement or action

also called the prime mover

Question 24

what are synergists?

Answer 24

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

Question 25

provide an example of a synergist being a fixator

Answer 25

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

Question 26

what is muscle tone

Answer 26

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.