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Muscles

Definition:
= Muscle is a contractile tissue type of animals

Khan video: Anatomy of a muscle cell

(External Link)

Khan video: Myosin and actin

(External Link)

Khan video: Role of sarcoplasmic reticulum in muscle cell

(External Link)

Three types of muscle

Smooth/ involuntary

  • not by will- spontaneous
  • unconscious routine tasks of the body:
    • Food moving down the digestive system
    • keeping the eyes in focus
    • adjusting the diameter of blood vessels

Structure:

  • spindle shaped cells with nucleus
Illustrates the structure of a smooth muscle

Functions:

Found in the walls of:

  • blood vessels
  • Uterus
  • bladder
  • Intestines

Cardiac muscle

  • Responsible for your heart beat (muscle only found in the heart)
  • Only found in the walls of the heart

Structure

  • branched and contains intercalated disks
  • Carry message in each cell for heart contraction
Illustrates the structure of the cardiac muscle

Voluntary/skeletal

controlled by will

  • Running
  • Walking
  • Skipping

Structure:

  • The basic units of a muscle are called myofibrils .
  • These myofibrils make up the muscle fibre (large muscle cells).
  • Numerous muscle fibres (cells) are found in bundles .
  • These bundles are surrounded by perimisium
    • This is called fasciculus
  • Numerous fasciculi are surrounded by epimysium
  • This forms a muscle
Indicates the differing structural components of the voluntary muscle.

Muscle contraction

  • Myofibrils are responsible for the muscle contraction.
  • Each myofibril consists of units called sarcomeres (there are many sarcomeres ineach myofibril )
  • Sarcomeres consist of thin actin filaments and thick myosin filaments.
  • When muscle fibres contract these filaments slide across each other.
  • The actin filaments shorten, but the length of the myosin filaments do not change.
  • This causes the sarcomeres shorten,
    • leading to the whole muscle to shorten
  • ATP (energy) is a substance in the muscle fibre that provides energy for the contracting actin filament.

IMAGE!!!Details on wish list

Video: Summary of the workings of the muscle

(External Link)

Muscle Exercise:

Column A

Column B

A) Attached to skeleton by tendons 1) Cardiac muscle
B) Seen in bundles 2) Blood vesels
C) They make up muscle fibers 3) Muscles
D) Spindle shaped structure 4) movement
E) Causes the pumping action of the heart. 5) muscle fibres
F) smooth muscles are found here 6) Fasciculus
G) specialized tissue 7) myofibrils
H) contraction and relaxation 8) voluntary muscles
I) bundles surrounded by perimysium 9) epimysium
J) Numerous fasciculi are surrounded by 10) Involuntary muscle

Choose the correct answer for column A from column B (only one correct answer per question)

Activity: classifying muscle types

  • Use the following story to classify the different muscle types. Use a coloured pen or highlighter to underline or highlight the actions in the story whichrequire the different types of muscles
  • Suggested colours to use: Pink = Cardiac Muslces; Blue =Voluntary ; Yellow = Involuntary
  • Then draw each structure in the space provided

Story:

BEEP BEEP BEEP!!!

6 a.m on a Monday morning Tsholo’s alarm goes off.

She jumps out of bed and walks to the toilet to relieve her bladder. Tsholo is very excited for the day and skips back to her room to get dressed and pack herschool bag for the new week. In the kitchen mom has prepared Tsholo’s favourite porridge –Mielie Meal *. Tsholo eats het porridge with greatpleasure. After breakfast, she brushes het teeth and skips to the car where she waits for mom to unlock the doors.

At school Tsholo runs to her friends in total excitement to tell them about her visit to her grandmother. While chatting she sees Tom - the boy she likes alot! He looks her way and Tsholo’s starts blushing. Her heart rate increases and her palms become sweaty.

The bell rings.

Tsholo and her friends walk to class, giggling and talking. Her heart rate slowly returns back to normal . The week has begun…

Draw and label the three different muscle types

Cardiac:

Voluntary:

Involuntary:

Interesting facts – skeleton

  • A baby is born with more bones (360 bones) than an adult (average 206 bones). Bones making up the skull and the spine fuse together as the body grows makingit less.
  • The femur/thigh bone is the largest in your body. The femur is approximately one quarter of a person’s overall height.
  • Strengthen your skeleton by drinking milk and eating leafy greens (such as brussels sprouts and kale). They contain calcium which keeps bones healthy andstrong.
  • A broken bone produces many new cells to rebuild the bone. These cells cover both ends of the broken part of the bone and close up the break.
  • Your bones are alive! In your body bones have their own nerves and blood vessels.
  • Your bone is 50% water and 50% solid material
  • You have 14 bones are in your face.
  • There are 8 bones in each of your wrists
  • You have 23 bones in each foot ( this includes the ankle)
  • Your skull is made up of fused bones which acts like a hard protective helmet for your brain.

Questions & Answers

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Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
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