Introduction to Muscular and Nervous Systems

Question 1

List the components of the muscular system

Answer 1

Skeletal muscle tissue and associative tissue elements form the muscular system of the body

Question 2

Describe the skeletal muscle structure

Answer 2

Microscopically, skeletal muscles are composed of muscle fibres or cells, that contain microfibirls, composed of the contractile thick and thin filaments or myofilaments.
Each muscle fibre is surrounded by a layer of connective tissue known as the endomysium.
Bundles of 10 to 100 or more muscle fibres or fascicles are surrounded by the connective tissue, perimysium. The whole muscle is encircled by the epimysium.

Muscles attach to bone or other tissues via these two connective tissue elements:
1. connective tissue directl unites with the periosteum of bone or the joint capsule
2. connective tissue elements fuse together to form: - cord like tendon e.g. Achilles tendon, and sheet-like aponeurosis e.g. external obique aponeurosis

Note: when a muscle or tendon passes over or around the edge of a bone it is usuallt separated from the bone by a bursa – often associated with joints– that reduces friction during movement.

When a tendon is subject to friction it may devleop a sesamoid bone that will increase the mechanical advantage of the muscle e.g. patella bone embedded in the quadriceps femoris muscle

Question 3

Describe the anatomy of a myofibril

Answer 3

Sarcomeres are arranged horizontally along a myofibril

Question 4

Describe the basic formation of a sarcomere

Answer 4

The sarcomere spans from z line to z line.
The sarcomere consists of two major structures:
- thin filament including actin, and other molecules
- thick filament including myosin
- during muscle contraction multiple sarcomeres work together to shorten the muscle in an independent and repeated asynchronous pattern through excitation-contraction coupling
- M band
- Z line

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Question 5

List and describe the nine steps of excitation contraction coupling

Answer 5

1. Efferent - motor neuron releases chemical that attaches to receptor on the sarcolemma
2. Action potential depolarises transverse- tubule (T-tubule)
3. Calcium is released into sarcomere
4. Calcium binds to special complex on a myofilament, allowing muscle contraction to happen
5. Actin and myosin join together, energy is released and produces cross-bridge movement
6. Muscle shortens when actin-myosin bond is broken, resulting in sliding of thick and thin filaments
7. Crossbridge actions continue in presence of high calcium of high calcium concentrations
8. Whene efferent stimulation stops, calcium moves back to holding space
9. Muscle contraction inhibited without calcium and remains in relaxed state

Question 6

Provide examples of muscles to demonstrate the names of muscles to interpret their structure and function

Answer 6

e.g.
Abductor pollicis brevis - abduct: to move away from, pollex = thumb, brevis= short – a short muscle that moves the thumb away from the middle finger
Flexor digitorum profundus - flexum = bent, digitus = digit, profundus = before bottom – a deep muscle that flexes the digits
Sphincter pupillae

Question 7

Names of muscles that describe the direction of their muscle fibres, relative to the midline of the body

Answer 7

• transversus abdominis: fibres run perpendicular to the midline
• oblique/fibres run diagonally at an angle, to the midline e.g. internal oblique
• rectus abdominis - fibres run straight along the midline

Question 8

Names of muscles that contain the location of the muscle

Answer 8

• tibialis anterior: muscle near the tibia
• biceps brachii: muscle in the arm
• frontalis: external to the frontal bone

Question 9

Names of muscles that indicate their relative size

Answer 9

• gluteus maximus
• gluteus minimus
• extensor digitorum longus
• adductor brevis
• gluteus medius (relative to nearby muscles)

Question 10

Names of muscles that indicate the number of attachments

Answer 10

• biceps
• triceps
• quadriceps: in this case, the number of muscles on a group

Question 11

Name of muscles that indicate shape

Answer 11

• deltoid: triangular shape
• ## serratus: saw-toothed shape

Question 12

Names that indicates attachment sites

Answer 12

• sternocleidomastoid

Question 13

Names of muscles that suggest their principal action

Answer 13

• pronator quadratus
• ## flexor carpi radialis

Question 14

Describe principles of muscle action

Answer 14

Muscles with the same function at a joint are typically located together in the same muscle compartment, innervated by the same nerve, with common arterial supply and venous drainage

Most skeletal muscle cross at least one joint, and are usually attached to the articulating bones that form the joint, thus when the muscle contracts, it drawser4one articulating bone toward the ohter, producing movement at the joint.

Origini s usually the stationary bone, insertion is usuallt the movable bone, with the belly in between. Attachment is more accurate

Anterior=flexors
Posterioir=extensors
mEDIAL= ADDUCTORS
ABDUCTORS= LATERAL
MEDIALANTEIOR WITH DIAGNOAL FIBRES AER MEDIAL ROTATORS
LATERL POSTERIOR WITH DIAGONAL FIBRES ARE LARERAL ROTATORS

EXCEPTIONS - KNEE AND ANKLE JOINTS FOR FLEX.EXEND

Digits in hands and foot that are medial/lateral

Question 15

Briefly describe nervous system organisation

Answer 15

The nervous and endocrine sstems are the control systems of the human body resposnsible fore maintaining homeostasis and thus health.
The nervous system does this via nerve impulses i.e. action potentials, and responds rapidly.

The endocrine system, on the other hand, uses hormones and responds more slowly.

The nervous system is primarily composed of nervous tissue. Nervous tissue consists of neurons or nerve cells, to receive and transmit impulses, and neuroglia or glia/glial cells, to assist the propagation of the nerve imppulse and provide nutrients to the neuron

The nervous system can be divided into two parts: the central nervous system (CNS) and peripheral nervous system (PNS). The PNS can be further divided into the somatic nervous system (SNS) and the autonomic nervous system (ANS). The nervous systems have three basic functions:

1. To sense changes internal and external to the body
2. To process (integrate) this sensory information
3. To initiate a response

Question 16

Describe the neurons of the PNS and their classification

Answer 16

Neurons

Neurons are functionally classified based on the type of information carried and the direction in which the nerve impulses are transmitted.

Sensory (afferent) neurons transmit sensory nerve impulse from receptors in the skin, sense organs, muscles, joints and viscera into the CNS. Higher order sensory neurons carry sensory signals from lower levels of the spinal cord and brain to higher brain regions.

Motor (efferent) neurons convey motor nerve impulses from the CNS to effectors (muscles or glands).

All other neurons that are not specifically sensory or motor are termed interneurons, and are numerous.

Question 17

Describe the structural subdivisions of the PNS

Answer 17

The peripheral nervous system (PNS) has two main structural subdivisions:

Somatic nervous system (SNS)
(Commonly called the voluntary nervous system)

In this system information from the periphery travels to the central nervous system (CNS) along afferent sensory nerves, and responses travel directly to skeletal muscles along effector motor nerves.

Autonomic nervous system (ANS)
(Commonly called the involuntary nervous system)

This system also contains sensory and motor components. However, information from the CNS travels to smooth muscles, cardiac muscles, and glands along a two-neuron efferent pathway [+].

Question 18

Describe the functional subdivisions of PNS

Answer 18

Functional subdivisions of PNS

There are two functional subdivisions of the PNS:

Sensory or afferent division: Sensory nerves carry information towards the CNS (brain or spinal cord) in response to stimulation such as pain, pressure, or stretch. 
Motor or efferent division: Motor nerves carry information away from the CNS to skeletal muscle fibers to bring about an appropriate response to the stimulus. 

Information needs to travel from one part of the body to another.

Neurons carrying sensory information to the spinal cord have their cell bodies in the dorsal root ganglia.
Neurons carrying information from the spinal cord to skeletal muscles have their cell bodies in the ventral horn of the spinal cord. 

Somatic nerve fibers running to and from the periphery are collected together into bundles called peripheral nerves.

Question 19

Define the dorsal root ganglia

Answer 19

Neurons carrying sensory information to the spinal cord have their cell bodies in the dorsal root ganglia.

Question 20

Define ventral horn

Answer 20

Neurons carrying information from the spinal cord to skeletal muscles have their cell bodies in the ventral horn of the spinal cord.

Question 21

Describe the somatic nervous system

Answer 21

Somatic Nervous System

The somatic nervous system (conscious, voluntary) consists of motor neurons from the CNS that innervate skeletal muscles and sensory neurons that convey information from somatic sensory receptors in the head, trunk and limbs to the CNS.

The somatic senses include touch, pressure, vibration, temperature, pain, proprioception:

        i. Mechanoreceptors detect tactile sensations (touch, pressure and vibration).

        ii. Thermoreceptors are free nerve endings that respond to warm and cold stimuli.

        iii. Nociceptors and free nerve endings are the receptors for pain sensations.

        iv. Muscle spindles monitor changes in skeletal muscle length.

        v. Golgi tendon organs monitor the force and extent of skeletal muscle contraction.

Note: the structural tissues that give the body its shape and external form (i.e. bones, muscles, skin) are collectively known as the somatic structures.

Question 22

Describe the autonomic nervous system

Answer 22

The autonomic nervous system (unconscious, involuntary) consists of motor neurons from the CNS that innervate smooth muscle, cardiac muscle and glands (of organs and blood vessels) and sensory neurons that convey information from autonomic sensory receptors located in the viscera/organs to the CNS. The autonomic (visceral) senses arise from the receptors in the internal organs. A variety of sensory receptors exist in the viscera of the body to detect changes in temperature, pH, organ distention, blood gas levels etc.

The motor part of the autonomic nervous system is further divided into the sympathetic nervous system and parasympathetic nervous system.

Question 23

Define the term dorsal root

Question 24

Define the term ventral root

Question 25

Define the terms dorsal and ventral rami

Question 26

Explain how the spinal cord assembles and organises information

Question 27

Explain the concept of spinal cord segments

Question 28

Explain how the spinal cord assembles and organises information

Question 29

Describe the anatomical relations of the spinal cord and spinal nerves

Question 30

Explain the relationship between spinal nerves, peripheral nerve plexuses, and named peripheral nerves

Question 31

List the three main morphological types of neurons, describe and contrast their features

Question 32

Label the components of a reflex arc

Question 33

Discuss, compare and contrast the structures of the thoracic and abdominal walls

Question 34

Compare the vascular supply of the abdominal and thoracic walls

Question 35

Compare the innervation of the abdominal and thoracic walls

Question 36

List and briefly describe the features of the three different muscle fibres types

Question 37

Label the features in this synovial joint

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Question 38

List the muscles of the abdominal wall from anterior to posterior

Answer 38

• external oblique
• internal oblique
• transversus abdominus
• rectus abdominus

Question 39

List the intercostal muscles

Answer 39

external intercostals, internal intercostals, innermost intercostals

Question 40

List the musccles of the anterior thorax