M3s2 Skeletal Muscle

Question 1

Introduction to skeletal muscle

Answer 1

-only voluntary muscle tissue in human body (controlled consciously)
-every physical action that a person consciously performs like speaking, walking or writing requires skeletal muscle
-attached to the bones of skeletal system are about 700 named muscles that account for roughly half of a person’s body weight
-each muscle in a discrete organ composed of skeletal muscle tissue, epithelial connective and nervous tissue

Question 2

Function of skeletal muscle

Answer 2

-contract to move parts of the body
-most skeletal muscles are attached to 2 bones across a joint, such that when contracted muscle brings parts of those bones closer to each other

Skeletal muscle function to:
-produce movement
-maintain posture and stabilize joints
-control excretion (elimination of urine and feces) and swallowing
-produce heat
-support and protect internal organs

Question 3

Organization of skeletal muscle tissue

Answer 3

• refer to photo in goodnotes
  -skeletal muscle consists of muscle tissue and connective tissue
  -connective tissue surrounds the muscle tissue and attaches the ends of each muscle to bone

Question 4

Skeletal muscle and connective tissue

Answer 4

-refer to goodnotes for image
-3 layers

Epimysium - layer of connective tissue that surrounds entire muscle and is continuous with the tissue that becomes the tendon

Perimysium - layer of connective tissue surrounding a bundle of muscle fibres (fascicle) within a muscle

Endomysium - layer of connective tissue that surrounds the individual muscle cells (muscle fibres) within a muscle bundle

Question 5

Microscopic anatomy of skeletal muscle tissue

Answer 5

-within a muscle cell (myofibre) there are many myofibrils that contain numerous myofilaments, the units of crontraction for the muscle cell

Question 6

Microscopic - muscle cells

Answer 6

• refer to goodnotes for images
  -muscle cells have a number of features

Sarcolemma:
-cell membrane surrounding a muscle cell
-different entity from the endomysium
-beneath sarcolemma are nuclei, myofibrils, and sarcoplasm (cellular fluid)

Nuclei:
-Skeletal muscle cells are multi-nucleated, meaning more than one nucleus
-nuclei are located towards outside of the myofiber

Myofibril:
-structural units of the muscle cell
-contain contractile myofilaments

Myofilaments:
-contractile units of the muscle cell

Sarcoplasmic reticulum:
-surrounds each myofibril
-where muscle cell stores calcium, which is necessary for muscle function

T-Tubules:
-traverse tubules (T-Tubules) are extensions of sarcolemma that surround myofibrils and transmit nerve stimulation to sarcoplasmic reticulum within cell

Question 7

Microscopic - myofilaments

Answer 7

• refer to goodnotes for images
  -organized into repeating structural units known as sarcomeres
  -when shortened, sacomeres cause contraction of the muscle
  -each unit consists of actin and myosin
  -one sacrome spans from one Z line to the next
  -Z lines are depicted as blue lines along the myofibril in image

Actin and myosin
Looking at one individual sarcomere, can observe the myofilaments create this unit
-consist of thin and thick myofilaments known as actin (thin) and myosin (thick)

Sarcomere banding
-skeletal muscle has striated appearance due to arrangement of actin and myosin into organized sarcomeres that form distinct lines and bands
A-Band - made of thick and thin filaments. Appears darker when viewed histologically
Z-Line - composed of protein that makes a “zig-zag” line marking the beginning and end of each sarcomere. It lies in the middle of the I band and where thin filaments attach
M-Line - composed of protein down the centre of the sarcomere (“mid-line”). Where thick filaments attach
I-Band - made up of thin filaments. Appears lighter in colour and transverse two sarcomeres

Question 8

Sarcomere appear light and dark bands

Answer 8

-due to overlap of thick and thin filaments
-I band light because area only consists of thin filaments (actin) and the Z-line down row middle is dark because it contains an abundance of structural proteins
-A-band dark because consists of thick filaments (myosin) and even darker towards sides because it is overlapping with actin, thus that area has both thick and thin filaments
-like Z-line the m-line is an abundance of structural proteins that create a dark line

See structure of sarcomere as seen with transmission electron microscopy (TEM)

Question 9

Skeletal muscle organization

Answer 9

-muscles of body generally organized as being either superficial (shallow), intermediate or deep
-most muscles focus on in this course are superficial muscles
-axial muscles include like inside and head while appendicular your arms and legs

Question 10

axial or appendicular: accounts for 126 bones in the skeleton and their associated muscles

Answer 10

Appendicular

Question 11

Axial or appendicular: includes bones and muscles associated with the skull, vertebral column (spine), and thoracic cage (ribs and sternum)

Answer 11

Axial

Question 12

Axial or appendicular: stabilize and control the movements of the pectoral (shoulder) and pelvic (hip) griddles

Answer 12

Appendicular

Question 13

Axial or appendicular: the muscle control the ,movements of the upper and lower limbs

Answer 13

Appendicular

Question 14

Forms the long axis of the body and consists of 80 bones and rate associated muscles

Answer 14

Axial