1. Muscles
HBS3B

2. The knee joint
Label the diagrams

3. The knee joint 1 – tendon 2 – patella 3 – bursa 4 – synovial membrane
6 – menisci (articular discs)
7 – cruciate ligaments
8 – articular cartilage
9 - synovial capsule
10 – fibula
11 – femur
12 – ligament
13 – tibia

4. Types of muscles Cardiac muscle found only in the heart
Smooth muscle or involuntary muscle found in the walls of the digestive system, the bladder, the lungs and blood vessels
Skeletal (or voluntary) muscle found in body muscles

5. Movement Muscles have three properties that allow them to work –
Contractibility = ability to contract or shorten
Extensibility = ability to be stretched
Elasticity = ability to return to the original length after stretching
Movement occurs due to muscles pulling on bones either side of a joint. When a muscle works, it slides its filaments together (contraction), thus becoming shorter and thicker, and pulling the ends of the bones together, and bending (or straightening) a joint.
Muscles can not push bones, so in order for the bones to move in the opposite direction, another set of muscles must contract, while the first set relaxes. Because muscles are elastic, they can stretch when relaxed, and shorten when contracted. These pairs of muscles are called agonist-antagonist pairs. The agonist is the muscle that is contracting or doing the work, while the antagonist is the muscle that is relaxing.
Synergists are muscles that help by steadying a joint
Fixators are synergists that fixate a joint (stop it moving)

6. Muscles and tendons Muscles are attached to bones by tendons.
The tendon(s) closest to the body, (attached to the fixed bone), is/are called the tendon(s) of origin, while the tendon(s) furthest from the body, (attached to the moveable bone), is/are called the tendon(s) of insertion.

7. Muscle structure

8. Muscle structure
The sarcolemma is a thin transparent membrane surrounding each muscle cell
Muscle fibres are cylindrical muscle cells
They are made up of many thread-like myofibrils
These are made up of many smaller protein filaments called myofilaments

9. Microscopic structure of muscles
There are two types of myofilaments – thick and thin
Actin makes up the thinner myofilaments
Myosin makes up the thicker myofilaments
A sarcomere is a unit containing overlapping bands of actin and myosin

10. The sarcomere
The arrangement of the actin and myosin fibres give the muscles its striated or banded appearance.
These are given different names:
The I band is where only actin fibres are visible
The A band are where actine and myosin overlap to form a darker appearance
The Z line is where actin molecules are linked together
A similar fainter line can be seen linking the myosin filaments – this is called the M line
The H zone is where only myosin filaments are visible
M line

11. Sliding filament model
Myofibrils comprised of actin and myosin myofilaments
When the muscle contracts, the actin and myosin filaments slide over each other, pulling the z-lines closer and shortening the muscle
This requires the use of energy in the form of Adenosine triphosphate
When the muscle relaxes the actin and myosin filaments are pulled past each other and return to their previous locations, so the muscle returns to its previous length
Actin and myosin don’t change in length – they just slide closer or further apart.

12. Control of muscle movement
Voluntary muscle contraction is initiated by nerve impulses, starting in the brain or spinal cord and travelling through the somatic division of the efferent tract of the peripheral nervous system.
One motor neuron will control several muscle fibres.
A motor unit is the motor neuron and all the fibres it controls

13. The neuromuscular junction
The neuromuscular junction is the point where the message is passed from neuron to muscle
The synaptic knob is the enlarged area at the end of the axon
The motor end plate is depression in the surface of the muscle fibre
The neurotransmitter used is acetylcholine

14. Roles of cerebrum and cerebellum
The primary motor cortex initiates voluntary muscle contraction and at the same time sends messages to the cerebellum
The cerebellum sends messages to co-ordinate different muscles so movement is smooth
Balance receptors send messages to the cerebellum so it can track the position and movement occurring in the head
Stretch receptors detect muscle and joint activity and send messages to the cerebellum so it can track movements of extremities
Upper motor neurons have cell bodies in the cerebrum (and some in spinal cord)
Lower motor neurons have cell bodies in the spinal cord

15. Roles of cerebrum and cerebellum
The diagram shows the nerve pathways from the cerebral cortex
Show the pathways
from sensory receptors
to and from cerebellum

16. Cerebellum involvement
Taken from Newton and Joyce p218

17. Sample questions
The neuron illustrated above would be classified correctly as
(a) a sensory neuron.
(b) a motor neuron.
(c) a connector neuron.
(d) there is not enough information to say.

18. Sample exam questions
1. Which of the following is NOT true of structure A?
(a) It is surrounded by three layers of meninges.
(b) Information from the body terminates in structure A's white matter.
(c) Its surface is convoluted to provide greater surface area.
(d) It is connected to, and able to influence, the cerebellum.
2. This question refers to the list of features below.
(i) regulation of osmotic balance
(ii) regulation of the heart rate
(iii) coordination of posture and movement-
(iv) temperature control
Which of the above features are roles played by structure B?
(a) (i), (ii) and (iii) only
(b) (i), (ii) and (iv) only
(c) (i), (ii), (iii) and (iv) only
(d) (ii) and (iv) only
3. Which of the following statements is true of the fluid contained in structure C?
(a) It is produced by the meninges.
(b) It has an important role in protecting the brain from infection.
(c) It assists with nourishment of the cerebral cortex.
(d) It assists with temperature regulation in the brain.

19. Sample questions
Using a diagram, explain the structures that comprise a synovial joint and their functions.

20. Synovial joints
Synovial capsule surrounds the joint and helps stabilise it and hold it all together
Synovial membrane is thin and smooth, to reduce friction, and secretes synovial fluid
Synovial fluid is thick and sticky, and acts as a lubricant for the joint
Articular cartilage provides a smooth surface to reduce friction as the bones move across each other
Articular disc are cartilaginous discs which act as shock absorbers
Bursae are fluid filled sacs which act as shock absorbers
Accessory ligaments join the bones and keep them together

21. Sample questions
Using diagrams, explain the main differences between compact bone, spongy bone and hyaline cartilage.
Relate these differences to the functions of these tissues.

22. Comparing bone and cartilage
Compact bone
Spongy bone
Bone has a few cells but also lots of mineral matrix to make it strong, and a good blood supply, which makes capable of repair
Compact bone is highly organised into osteons to make columnar Haversian systems – this gives it strength.
Spongy bone is less organised, with more spaces – this makes it lighter. The spaces are filled with red bone marrow which make blood cells
Cartilage has relatively few cells and lots of matrix. The matrix has more protein than minerals so it is strong and slightly elastic. It has less of a blood supply, so is slower to heal.