Anatomy of muscles and nerves

Question 1

Describe the functions of muscles

Answer 1

•	Movement
      –	Skeleton
      –	Intestines
      –	Heart & blood vessels
•	Static support
•	Heat production

Question 2

Briefly describe the 3 types of muscle and their primary functions

Answer 2

• Skeletal - attached to skeleton, locomotion, voluntary
• Cardiac - heart and blood circulation, involuntary
• Smooth - walls of vessels and organs, moves substances and restricts flow, involuntary

Question 3

Describe the epimysium, fascicles, perimysium and endomysium.

Answer 3

Enclosing each muscle is a layer of connective tissue known as the epimysium; enclosing each fascicle is a layer called the perimysium, and enclosing each muscle fiber is a layer of connective tissue called the endomysium.

Question 4

Define unipennate and multipennate muscles

Answer 4

The fibers in unipennate muscles are all oriented at the same (but non-zero) angle relative to the axis of force generation

The fibers in multipennate muscles are arranged at multiple angles in relation to the axis of force generation, and are the most general and most common architecture.

Question 5

Describe the spinal nerves

Answer 5

• 31 pairs in total
• 8 cervical nerves (C1–C8)
• 12 thoracic nerve (T1 -T12)
• 5 lumbar nerves (L1-L5)
• 5 sacral nerves (S1-S5)
• 1 coccygeal nerve
• Named after associated vertebrae
• 1st spinal nerves exits between skull and C1

Question 6

Describe the differences between the somatic and autonomic signalling pathway

Answer 6

• In the somatic pathway, the motor fibres are not synapsing (CNS -> muscle)
• In the autonomic pathway, the motor fibres do synapse at a ganglion before reaching the target area

Question 7

Describe the site of spinal outflow for the sympathetic and parasympathetic nervous system

Answer 7

o Sympathetic - thoracolumbar

o Parasympathetic – craniosacral (top and bottom)

Question 8

Describe the relative location of the ganglia in the sympathetic and parasympathetic nervous system

Answer 8

o Sympathetic – close to spinal cord

o Parasympathetic – close to target

Question 9

Define a dermatome and a myotome

Answer 9

• A skin area innervated by the sensory fibres of a single nerve root is known as a dermatome.
• A group of muscles primarily innervated by the motor fibres of a single nerve root is known as a myotome.

Question 10

Define the origin and insertion of a muscle

Answer 10

• Origin - proximal or medial attachment

* Insertion - distal or lateral attachment

Question 11

Describe the innervation of axial and appendicular muscles

Answer 11

• Appendicular (limb) muscles are supplied by nerve plexuses, ie. nerves containing mixed fibres from more than one spinal nerve.
• Axial (trunk) muscles are supplied segmentally, ie. by separate nerves that have not mixed with others.

Question 12

What is Hiltons law?

Answer 12

o The nerve supplying the muscles extending directly across and acting at a given joint also innervates the joint.
o A sensory nerve supplying a joint also supplies the skin overlying the joint.

Question 13

What is compartment syndrome?

Answer 13

Compartment syndrome is an acute medical problem following injury or surgery in which increased pressure (usually caused by inflammation) occurs within a compartment

Question 14

What are the distinguishing histological features of skeletal muscle?

Answer 14

1. Long, slender (up to 30cm!)
2. Multinucleate; peripherally located nuclei
3. Abundance of mitochondria
4. Cross striations (actin & myosin filaments)
5. Arranged into fascicles (=bundles) by connective tissue

Question 15

What are the distinguishing histological features of smooth muscle?

Answer 15

• Found in organs and vessels
• Devoid of cross striations
• Shorter fibre length than skeletal muscle
• Centrally-situated cigar-shaped nuclei

Question 16

What are the distinguishing histological features of cardiac muscle?

Answer 16

• Cross-striated, but involuntary.
• Single (central) rounded nucleus.
• Cells are often branched.
• The region where the ends of the cells are connected to another cell is called an intercalated disc.
• The intercalated disc contains gap junctions.
• Gap junctions allow the muscle cells to be electrically coupled, so that they beat in synchrony.

Question 17

Primary functions of ligaments and tendons

Answer 17

• Ligaments bind bone to bone, “like to like”, vital for stabilising joints
• Tendons bind bone to muscle, vital for movement

Question 18

What signals are found in the dorsal and ventral roots?

Answer 18

• Dorsal root = sensory

* Ventral root = motor

Question 19

What dermatome are the nipples in?

Answer 19

T4

Question 20

What dermatome is the umbilicus found in?

Answer 20

T10

Question 21

What dermatome is the sternomanubrial joint found in?

Answer 21

T2

Question 22

Which spinal nerves form the brachial plexus?

Answer 22

Brachial: C5 - 8, T1

Question 23

Which spinal nerves form the lumbosacral plexus?

Answer 23

L1-S5

Question 24

Describe the aponeurosis

Answer 24

Aponeurosis – flat, thin broad tendons found on the anterior of the abdominal oblique muscles.

Question 25

Describe the differences between synergist and fixator muscles

Answer 25

• Synergist muscles – perform or help perform the same set of joint motions as the agonist, i.e. assists movement of the joint
• Fixator/stabilising muscles – stabilise the joint so the joint can move efficiently without risk of dislocation

Question 26

Describe the structure of a sphincter

Answer 26

• Sphincters – muscle fibres are arranged circularly and thickened around the wall of a structure (usually a tube). They are mostly composed of smooth (involuntary) muscle within the body, but are also composed of skeletal muscle (voluntary) when controlling the flow of fluids to the outside of the body. The involuntary muscle is usually the deeper of the two.

Question 27

Whats the primary function of the diaphragm?

Answer 27

Diaphragm – when relaxed has a dome shape, contracts during inhalation, causing the dome to flatten and the lungs pull in air. Primary function is to increase the volume of the thoracic cavity during inhalation.