Muscles

Question 1

Skeletal muscles:

Answer 1

Voluntary striated muscle that is attached to bones

Human muscular tissue makes up 40-50% of body weight

Question 2

What are the physiological characteristics of muscle?

Answer 2

1 Irritability (responsiveness) 
2 Contractility 
3 Elasticity
4 Conductivity 
5 Extensibility 

ICECE

Question 3

Irritability

Answer 3

1. Irritability
   - Property of all living cells
   - Muscles and nerve cells develop this property to the highest degree
   - referred to as excitability
   - receives stimuli (e.g cold, a change in environment) and responds to them.
   - muscle response to the stimuli is contraction

Question 4

Contractility

Answer 4

Enables muscles to change their shape and become shorter and thicker

Question 5

Elasticity

Answer 5

When a muscle cell is stretched and then tension is released, it recoils to its original resting length.

The return to the original length when tension is released

Question 6

Conductivity

Answer 6

Stimulation of a muscle fibre produces more than a local effect

The local electrical change triggers a wave of excitation that travels rapidly along the fibre and initiates processes leading to muscle contraction

Question 7

Extensibility

Answer 7

In order to contract, a muscle cell must also be extensible - able to stretch again between contractions

Skeletal muscle fibres can stretch as much as 3x their contracted length
(Most cells rupture if stretched a little)

Question 8

All motion in the body is due to three types of muscles

Answer 8

1. Skeletal (striated)
2. Smooth
3. Cardiac

Question 9

Skeletal / Striated muscle

Answer 9

Skeletal muscle contraction allows for movement of the entire body and is under voluntary control.

Skeletal muscles are attached to bones and make up a large percentage of body mass

Nerve impulses trigger a reaction from the muscle which contracts, moving its associated bone or joint

Question 10

Smooth muscle/ non-striated muscles

Answer 10

• also known as involuntary/ visceral
• function automatically, without conscious will
• these muscles are found in the digestive and circulatory system and some internal organs of the body

Question 11

Cardiac muscle

Answer 11

The involuntary muscle that makes up the heart

It is unique and not found in any other part of the body

It is striated and has a crossing, banding pattern that allows contraction; thus beating of the heart

It is under the control of the autonomic nervous system

Question 12

Muscles are attached to the bone by;

Answer 12

Structures of connective tissue with extensions of loose fibres called tendons

Question 13

Muscle is always under some degree of contraction which is referred to as:

Answer 13

Tone

Tone of the skeletal muscle gives firmness and maintains a slight steady pull on the attachment even when the muscle is at rest

Question 14

What are the three parts of a muscle?

Answer 14

1. The origin
2. The belly
3. The insertion

Question 15

The origin

Answer 15

Is the more fixed part of the muscle closest to the skeleton, which flexes but remains stationary

Question 16

The belly

Answer 16

Middle part of the muscle

Question 17

The insertion

Answer 17

The part of the muscle which is the movable attachment and farthest from the skeleton

Question 18

What is the action of this muscle?

Orbicularis oculi

Answer 18

Closure of eyelids

Draws lacrimal canal on to surface of eye

Muscle pulls on lacrimal sac

Question 19

What is the action of this muscle?

Levatore palpebrae superioris

Answer 19

Raises upper eyelid or voluntarily opens the eye

Opposes orbicularis oculi

Question 20

What is the action of this muscle?

Corrugator supercilii

Answer 20

Draws eyebrows medially and inferiorly

Question 21

What is the action of this muscle?

Procerus

Answer 21

Draws down medial angles of eye browns and produces transverse wrinkles over bridge of nose

Question 22

What is the action of this muscle?

Orbicularis oris

Answer 22

Closes and protrudes lips

Question 23

What is the action of this muscle?

Nasalis

Answer 23

Covers the nose, flares the nostrils

Question 24

What is the action of this muscle?

Levator Labii superioris

Answer 24

Elevates upper lip

Question 25

What is the action of this muscle?

Levator anguli oris

Answer 25

Elevates corners of mouth

Question 26

What is the action of this muscle?

Zygomaticus major and minor

Answer 26

Draws angles of mouth upward and outward, elevates the lip, as in laughing

Question 27

What is the action of this muscle?

Risorius

Answer 27

Draws angle of mouth out and back (laterally)

Question 28

What is the action of this muscle?

Depressor labii inferious

Answer 28

Draws lower lip inferiorly and laterally during mastication

Question 29

What is the action of this muscle?

Depressor anguli oris

Answer 29

Draws angle of mouth down and laterally

Question 30

What is the action of this muscle?

Mentalis

Answer 30

Elevates and protrudes lower lip, wrinkling the skin of the chin

Question 31

What is the action of this muscle?

Frontalis

Answer 31

Draws back scalp, aids in wrinkling forehead

Involved in headaches

Question 32

Muscles of mastication (chewing)

Answer 32

1. Buccinator - draws corner of mouth laterally, compresses cheek
   FUNCTION: chewing, whistling, suckling
2. Temporalis - Elevates and retracts mandible, assists in side to side movement of mandible
   FUNCTION: elevates and stabilizes the jaw
3. Masseter - elevates mandible slightly and protracts it
   FUNCTION: elevates the jaw, clenching the teeth

Question 33

Muscles of the neck:

Answer 33

Platysma - draws down the lower jaw & lips
(Murphy brown neck)

Sternocleidomastoid - bends neck up and down, rotates head to opposite side