Muscle Structure And Function

Question 1

How many muscles and joints does the human body have?

Answer 1

650 muscles

187 joints

Question 2

What are the three types of muscle tissues?

Answer 2

Cardiac - in the heart
Smooth - found at walls of organs and around blood vessels
Skeletal - large muscles and muscle cells

Question 3

Describe cardiac muscle

Answer 3

Responsible for circulating blood
Small cells
Single nucleated
Involuntary

Question 4

Describe smooth muscle

Answer 4

Single nucleated

Involuntary

Question 5

Describe skeletal muscle

Answer 5

Multinucleated

Voluntary

Question 6

What are the 3 layers of connective tissues in a muscle?

Answer 6

Epimysium
Perimysium
Endomysium

Question 7

Describe the epimysium

Answer 7

A tough connective tissue
Surround the whole muscle.
Surrounds bundles of nerve cells that run in long fibres called fascicles.

Question 8

Describe perimysium

Answer 8

Surround the individual fascicles

Allowing nerves and blood flow to individual fibres

Question 9

Describe the endomysium

Answer 9

Surrounds each individual fibre

Acts as a protective layer

Question 10

What are the functions of muscle tissue?

Answer 10

Produce movement 
Stabilise 
Produce heat
Movement of substances 
Regulate organ volumes

Question 11

What are the properties of muscle tissue?

Answer 11

Excitability - responses to chemicals released from nerve cells
Conductivity - produce and receive electrical signals
Contractibility - ability to shorten and generate force
Extensibility - can be stretched without damage
Elasticity - can return to normal shape after being stretched

Question 12

What is the most common type of muscle?

Answer 12

Skeletal

Question 13

Describe skeletal muscle

Answer 13

Attaches to bone, skin or fascia
Striated with light and dark bands
Multi nucleated
Voluntary control of contraction and relaxation

Question 14

What causes the skeletal muscle to be multi nucleated?

Answer 14

Formed out of myoblast cells fusing together.

Each myoblast contains a nucleus so when they fuse it produces a muscle with lots of nuclei.

Question 15

What are some functions of skeletal muscle?

Answer 15

Produces movement 
Maintains posture
Supports - soft and hard tissues
Maintain body temp 
Proprioception

Question 16

What are the structures that skeletal muscle is composed of?

Answer 16

Connective tissue
Muscle tissue
Nerves
Blood vessels

Question 17

What are the connective tissue structures?

Answer 17

Epimysium
Perimysium
Endomysium

Question 18

What is the epimysiums role?

Answer 18

The outer layer
Irregular fibrous tissue 
Surrounds whole muscle 
Exterior collagen layer 
Connected to deep fascia 
Separated muscle from surrounding tissue

Question 19

What is the perimysiums role?

Answer 19

Middle layer 
Surrounds muscle fibre bundles = fascicles 
Half collagen 
Half elastin 
Contains blood vessels and nerve supply

Question 20

What is the endomysiums role?

Answer 20

Inner layer
Surround individual muscle cells - muscle fibres and myofibrils
Contain capillaries and nerve fibres
Contain satellite cells that repair damage

Question 21

What occurs with the 3 connective tissues at the end of the muscle?

Answer 21

The come together to form connective tissue attachments to bone such as tendons or aponeurosis.

Question 22

Describe the nerves in a skeletal muscle

Answer 22

Collection of muscle cells is supplied by a motor neurone
One motor nerve and the muscle fibre it supplies if known as a motor unit.
Each muscle cell is supplied by a terminal branch of a motor neurone
Found in the endomysium

Question 23

Describe the blood vessels located in a skeletal muscle

Answer 23

Muscles have extensive vascular systems
Get large amounts of oxygen
Supply nutrients
Carry away waste products
Each muscle cell is in contact with 1 or 2 capillaries
Found in the endomysium
Exeter the muscle at the same point as the nerve.

Question 24

Describe skeletal muscle tissue

Answer 24

Very long and cylindrical
Become very large
Contain hundreds of nuclei
Contain many mitochondria

Question 25

What are the main structures located in a skeletal muscle?

Answer 25

``` Sarcolemma T - tubules Sarcoplasmic reticulum Myofibrils and myofilaments Sarcomeres ```

Question 26

Describe the Sarcolemma

Answer 26

Cell membrane of a muscle cell Surround the Sarcoplasm - cytoplasms of a muscle cell Filled with tiny threads called Myofibrils and myoglobin A change in its transmembrane potential can begin depolarisation

Question 27

Describe the T- tubules

Answer 27

Invaginations of the Sarcolemma into the centre of the cell Allow the whole muscle to contract at the same time Fill with extra cellular fluid Carry action potentials down into the cell Contain many mitochondria

Question 28

Describe the Sarcoplasmic reticulum

Answer 28

Membranous structure surrounding each Myofibril System of tubular sacs similar to smooth endoplasmic reticulum Help to transmit action potentials to myofibrils Form chambers at each end = Terminal Cisternae This is where the primary site of calcium is released Store calcium Release it to trigger action potentials

Question 29

What is a triad?

Answer 29

Formed from one T - tubules and 2 terminal cisternae | An active mechanism, that releases calcium to start a muscle contraction.

Question 30

Describe myofibrils and myofilaments

Answer 30

These are threads that are separated by the Sarcoplasmic reticulum Maude up of bundle of protein filaments called microfilaments These are contractile proteins

Question 31

Describe the sarcomere

Answer 31

Thick and thin filaments over lap each other, forming a striated pattern Thick = myosin protein Thin = actin protein known as Light I bands In the over lap region it’s known as the A band for both actin and myosin cross over They’re arranged in compartments known as sarcomeres - separated by Z discs at each end H zone is an area of only myosin filaments M line if the middle of the sarcomere Contractile units of the muscle

Question 32

What are the 4 main muscle proteins?

Answer 32

Myosin, actin, troponin and tropomyosin

Question 33

What are 4 other proteins found?

Answer 33

Titin, myomesin, nebulin and dystrophin

Question 34

Describe myosin

Answer 34

Thick filaments Composed of a long tail and two head The heads rotate - at the hinge region- to extend towards the thin action filaments - to form cross bridges They’re held in place my m- line proteins Tail binds to other myosin proteins When contraction occurs, myosin doesn’t change length

Question 35

Describe actin, tropomyosin and tropnin and how they work together

Answer 35

Thin filaments At resting - tropomyosin heads cover the actin binding sites To initiate a muscle contraction they have to move to expose the sites Calcium ions bind to troponin Causing both proteins to rotate and move away Exposing the binding site Myosin heads can now bind = cross bridge formed Held in place by the z discs

Question 36

Describe TITIN

Answer 36

``` Acts as an anchor to thick filaments Attach the m line and the z disc Can stretch to 4 times its resting length Role in recovery Important in eccentric contractions ```

Question 37

Describe myomesin

Answer 37

Forms the M line and connects to TITIN and adjacent thick filaments

Question 38

Describe Nebulin

Answer 38

Inelastic protein | He,so to align thin filaments

Question 39

Describe Dystrophin

Answer 39

Links thin filaments to the Sarcolemma | Transmits tension generated to the tendon

Question 40

What occurs is we lengthen our muscle past optimal range?

Answer 40

Fewer cross bridges formed | Less force and contraction produced

Question 41

What occurs if the muscle is overly Shortened?

Answer 41

Few cross bridges formed Less force and contraction produced Thick filaments crumpled by z discs

Question 42

What does the length tension curve show?

Answer 42

A graph of force of contraction versus length of the sarcomere.

Question 43

What is ATP’s role in a muscle contraction?

Answer 43

Supplies energy for the contraction Supplies the energy for active transport of Ca ions into the SR Amounts already in the muscle is low Sufficient to power a few seconds Has to be regenerated quickly for sustainable contractions

Question 44

What are the 3 sources of ATP production within a muscle?

Answer 44

Creatine phosphate Anaerobic Cellular Respiration Aerobic Cellular Respiration

Question 45

Describe how creatine phosphate works

Answer 45

Excess ATP in a resting muscle is used to form CP ADP + P - the P is transferred to combine with creatine to make CP THe CP can be used quickly to create ATP when needed CP will transfer back its phosphate to ADP to form ATP and creatine Quick breakdown Maximal contraction of 15 seconds Can be taken as a supplement - but this can have negative impacts

Question 46

Describe how anaerobic respiration works

Answer 46

ATP is produced from the breakdown of glucose into pyruvic acid Occurs in a process known as glycolysis Pyruvic acid converted to lactic acid Diffuses into the blood - too much will cause muscle fatigue and stop the contraction This process can continue for around 30-40 seconds

Question 47

Describe how aerobic respiration works

Answer 47

Pyruvate, fatty acids, oxygen, amino acids - all processed in separate compartments in the mitochondria Uses water and heat The ATP created lasts for any activity over 39 seconds and up Sufficient o2 = pyruvic acid enters mitochondria to generate ATP Fatty acids and amino acids are also used Provides 90% of ATP