Muscles

Question 1

How many muscles and joints are there in the body?

Answer 1

650 muscles
187 joints

Question 2

Primary tissue is divided into 3 types
Name them-

Answer 2

Cardiac muscle - responsible for circulating blood. Small cells, limited repair ability. Involuntary contractions . Each cell has one nucleus

Skeletal muscle- multinucleated. Larger cells (up to 30cm long) can partially repair themselves. Voluntary contractions

Smooth muscle- found in organ walls eg intestines. One nucleus per cell. Has ability to repair itself if it sustains damage. Involuntary contraction

Question 3

Functions of muscle tissue -

Answer 3

Produces body movement and stabilises body position
Regulates organ volumes - bands of smooth muscle called sphincters - relax to allow release eg within bowel
Movement of substances within body - blood,lymph,urine,air,food and fluids, sperm
Produces heat - involuntary contractions of skeletal muscle (shivering)

Question 4

What should patients struggling with substance movement do ? Eg venous return from lower leg -

Answer 4

Eg struggle with venous return from lower leg should be encouraged to get.muscles working to aid this. Plantar and Doris flexion of the ankle - muscles contract, increase pressure and aid venous return.
Feet elevation and compression garments are also effective.

Question 5

Properties of muscle tissue
Excitability -
Conductivity -
Contractivity -

Answer 5

Excitability - responds to chemicals released from nerve cells
Conductivity - ability to propagate electrical signals over membrane
Contractivity - ability to shorten and generate force

Question 6

Properties of muscle tissue
Extensibility -
Elasticity -

Answer 6

Extensibility - to be selected without damaging the tissue
Elasticity - ability to return to original shape after being stretched

Question 7

Properties of skeletal muscle tissue:
And how it appears under microscope:

Answer 7

Attaches to bone/skin/fascia, maybe via tendons/aponeurones
Striated with light and dark bands visible with a microscope
Voluntary contraction and relaxation control
Cells are formed from multiple myoblasts, they fuse together and are therefore multinucleated

Question 8

Functions of skeletal muscle -

Answer 8

Produce Skeletal movement
Maintain body position
Support soft/hard tissues
Guard body openings
Maintain body temperature
Stores nutrient reserves
Proprioception

Question 9

Skeletal muscle structures
Layers: 1) epimysium -

Answer 9

Outer layer that surrounds the whole muscle
Dense irregular connective tissue
Exterior collagen layer so is therefore not elastic
Connected to deep fascia
Separates muscle from surrounding tissues

Question 10

Skeletal muscle structures
Connective tissue layers: 2)perimysium:

Answer 10

Middle layer that surrounds fasciculus (find muscle fibres/cells within this)
More elastic than the outer layer as contains elastin as well as collagen
Contains blood vessels and never supply to fascicles

Question 11

Skeletal muscle structures
Connective tissue layers: 3) endomysium:

Answer 11

Inner layer that surrounds muscle fibres (individual muscle cells) within fascicles
High proportion of elastic fibres which loosely connects them
Contains capillaries and nerve fibres contacting muscle cells
Contains satellite cells (stem cells) that repair any damage

Question 12

Skeletal muscle:
Describe how connective tissue muscle attach to structures:

Answer 12

All 3 layers that make up the CT come together at the ends of muscles to form connective tissue attachment to bone matrix
Eg tendon (bundle) - transfers force muscle to bone
Apeneurosis (sheet) - broader attachment

Question 13

Skeletal muscle structures
Nerves: where are they found, functions etc…

Answer 13

In perimysium and endomysium
Nerves control voluntary contractions. Messages from CNS reach muscle tissue via peripheral nerve
Collection of muscle cells are supplies by a motor neurone
One motor nerve and the muscle fibres it supplies = motor unit!!
Each muscle cell supplied by a terminal branch of a motor neurone

Question 14

Skeletal muscle structures
Blood vessels: functions and muscle contact with them etc..

Answer 14

Muscles have extensive vascular systems that:
Supply large amounts of o2
Supply nutrients
And carry away waste products eg. Co2 h2o ADP

Each muscle cell is in contact with 1 or 2 capillaries
Nerve fibres and capillaries are found in the endomysium between individual cells

Question 15

Skeletal muscle structures
Muscle tissue (cells/fibres): structure and shape etc..

Answer 15

Long and cylindrical
Develop through mesodermal cell fusion (myoblasts)
Become very large
Contain hundreds of nuclei that are arranged around periphery of cell
Contain many mitochondria

Question 16

Organisation of skeletal muscle fibres
- the sarcolemma:

Answer 16

The cell membrane of the cell
Surrounds sarcoplasm
Sarcoplasm filled with tiny threads called myofibrils and myoglobin
Contractions begin when there is a change in transmembrane potential

Question 17

Organisation of skeletal muscle fibres
-Transverse (T) tubules

Answer 17

T tubules are invaginations of the sarcolemma into he centre of the cell
Filled with extracellular fluid
Carry muscle AP’s down into cell
Allow entire muscle fibre to contract simultaneously
Mitochondria lie in rows throughout the cell - near muscle
Proteins present that use ATP during contraction

Question 18

Organisation of skeletal muscle fibres
- sarcoplasmic reticulum (SR)

Answer 18

A membrane structure surrounding each myofibril
System of tubular sacs similar to smooth endoplasmic reticulum in non-muscle cells
Helps transmit AP’s to the myofibril
Forms chambers at each end (terminal cisternae) attached to the-tubules
Chambers store calcium, when released, contraction begins

Question 19

Skeletal muscle structures
What is a triad and its benefit ?

Answer 19

One T-tubule and two terminal cisternae make up a triad
Calcium in high conc via ion pumps and allow this to be maintained
Release calcium into sarcomeres to begin muscle contraction

Question 20

Skeletal muscle fibre organisation
Myofibrils and myofilaments -

Answer 20

Each muscle fibre can have hundreds/thousands of myofibrils depending on size
Muscle fibres filled with threads called myofibrils separated by SR (sarcoplasmic reticulum)
Myofibrils made up of bundles of protein filaments = myofilaments
Myofilaments are the contractile proteins of a muscle (thick and thin myofilaments)
Actin = thin
Myosin = thick

Question 21

Myofilaments and the sarcomere
** look over the diagram for sarcomere contraction, have to be able to recognise and identify elements ***
What bands contain what filaments ?

Answer 21

Thick and thin filaments overlap eachother in a pattern that creates striations (alternating light I bands and dark A bands)
I band - contains only thin filaments (actin)
A band- contains thick filaments (myosin)
H zone and M zone only have thick filaments

Filaments arranged in compartments which makes up the sarcomere, and separated by Z discs

Question 22

Name the proteins of a muscle and their 3 actions:

Answer 22

Contractile proteins (myofilaments) - myosin and actin
Regulatory proteins - turn contractions on and off = trooping and tropomyosin
Structural proteins - provide proper alignment, elasticity and extensibility = titin (important one) myomesin, nebulin and dystrophin

Question 23

Proteins of a muscle
Myosin -

Answer 23

Thick filaments
Each molecule resembles two golf clubs twisted together
Myosin heads (cross bridges) extend towards the thin filaments
Held in place by M line proteins

Question 24

Proteins of a muscle
Actin - (and other molecules attached)

Answer 24

Thin filaments - also contain troponin and tropomysoin
Myosin binding site present on each actin molecule is covered by tropomyosin in a relaxed muscle
For a contraction to occur, binding site needs to be uncovered so myosin heads can attach to actin molecules
Thin filaments are held in place by Z lines.

Question 25

How can we classify what one sarcomere is?

Answer 25

One Z line to the next Z line is a sarcomere

Question 26

Proteins of a muscle Titin -

Answer 26

Anchors thick filaments to M line and to Z discs. Portion of molecule between Z discs and end of the thick filament - able to stretch to 4x its resting length and spring back unharmed (og shape) Role in muscle recovery from being stretched, therefore important in eccentric contractions

Question 27

Other structural proteins - myomein = - nebulin = - dystrophin =

Answer 27

Myomesin - M line, connets titin to adjacent thick filaments Nebulin - inelastic protein helps align thin filaments Dystrophin - links thin filaments to sarcolemma and transmit tension generated to the tendon

Question 28

What happens to the sliding filament model when contracting (isotonic concentric)?

Answer 28

Z discs move closer together Sarcomeres shorten Thick and thin filaments don’t change in length - width of band A stays the same Thin filaments slide towards M line

Question 29

Describe the stages of skeletal muscle contraction:

Answer 29

Nerve impulses reach an axon terminal and synaptic vesicles release Ach (acetylcholine) Ach diffuses to receptors on the sarcolemma - Na channels open Sodium rushes into the cell A muscle AP spreads over the sarcolemma and down into the T-tubules AP reaches a triad Terminal cisternae release Calcium into sarcoplasm Calcium binds to troponin and causes troponin-tropomyosin complex to move and reveal myosin binding sites on actin Excitation - contraction coupling Contraction cycle begins

Question 30

Describe stages of the contraction cycle:

Answer 30

Repeating sequence of events that causes things to actin filaments to slide between the thick filaments Cycle steps - exposure of active sites ATP hydrolysis into ADPand Pi Attachment of myosin to actin to form cross bridges Power stroke - pivoting of the myosin head, pulling in the thin filament Detachment of myosin from actin Reactivation of myosin Cycle will repeat as long as there is ATP available and high calcium level near thin filaments

Question 31

Describe the stages of muscle relaxation:

Answer 31

Acetylcholine breaks down within synaptic cleft Muscle action potential ceases Calcium release Channels close Calcium detaches from troponin Active transport pumps calcium back into storage in the terminal cisternae of the sarcoplasmic reticulum Calcium conc falls Tropomyosin-troponin complex recovers, binding site on actin molecules are now prevented from myosin binding Contraction ends Relaxation occurs, muscle returns passively to resting length

Question 32

Length of muscle fibres How do we get the greatest amount of tension?

Answer 32

Optimal overlap of thick and thin filaments produces the greatest number of cross bridges and the greatest amount of tension

Question 33

Length of muscle fibres What happens as the muscle stretches past optimal length? And if muscle is overaly shortened (less than optimal)?

Answer 33

As it stretches, fewer cross bridges exist so therefore less force is produced When short, fewer cross bridges exist and less force is produced. Thick filaments are crumpled by Z discs

Question 34

What is normal resting muscle length?

Answer 34

70-130% of the optimum length This can be demonstrated by a graph - length tension curve

Question 35

Muscle metabolism - name the sources of ATP production and explain briefly why we need them:

Answer 35

Muscle uses ATP at a great rate when active Sarcoplasmic ATP only last for a few seconds 3 sources of ATP production within muscle: Creatine phosphate Anaerobic cellular respiration Aerobic cellular respiration

Question 36

Muscle metabolism Creatine phosphate -

Answer 36

Excess ATP within resting muscle used to form Creatine phosphate CP is 3-6 times more plentiful than ATP within muscle It’s quick breakdown provides energy for creation of ATP Sustains maximal contraction for 15 seconds Athletes tried Creatine supplemation - gain body mass but shut down bodies own synthesis

Question 37

Muscle metabolism Anaerobic cellular respiration -

Answer 37

ATP produced from glucose broken down into pyruvic acid (x2) during glycolysis - net gain 2x ATP When no O2 present - pyrvic converted to lactic acid which diffuses into the blood Glycolysis can continue anaerobically to provide ATP for 30-40 seconds of maximal activity Eg 200m race

Question 38

Muscle metabolism Erotic cellular respiration -

Answer 38

ATP for any activity lasting over 30 seconds If sufficient O2 available, pyruvic acid enters mitochondria to generate ATP, water,heat Fatty acids and amino acid can also be used by the mitochondria Provides 90% of ATP energy if activity lasts more than 10mins