MSK Lecture 5

Components of the Nervous System

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

Central Nervous System (CNS) Components

Brain and spinal cord

Peripheral Nervous System (PNS) components

Nerves, ganglia, somatic components, and autonomic components

Somatic Components of the PNS

Cranial nerves and spinal nerves

Autonomic Components of the CNS

Innervation of glands, smooth muscle of viscera, and blood vessels

What is the primary focus of MSK physiotherapy?

The peripheral nervous system (PNS)

What are somatic nerves made up of?

Cranial and spinal nerves

How many pairs of the cranial nerves are there?

12 pairs

How many pairs of spinal nerves are there?

31 pairs

Spinal Nerves

Either bring sensory information to the brain for interpretation, or carry motor information to the muscles to create muscle contraction/movement

Afferent (Sensory) Nerves

Carry information from the periphery to the CNS (touch, pain, proprioception, pressure, temperature, etc.)

Dermatome

Areas of nerve distribution, areas supplied by a specific nerve root level

Efferent (Motor) Neurons

Carry information to the muscles from the brain/spinal cord

Plexuses

Spinal nerves forming complex intersections of afferent and efferent nerves

Examples of plexuses

Brachial and lumbosacral

Myotome

Certain movements are primarily innervated by a specific nerve root

Neuromuscular control

Complex coordination of movement, it is more complex than contracting a single muscle and generating force, it requires efficient use and coordination of multiple systems to create: force, stability, and mobility

Beyond our ability to generate strength and maintain mobility, input is required from:

Proprioception, perception, and balance (postural control)

Pain

Refers to the subjective experience of actual or impending harm (SUBJECTIVE), primary driver resulting in someone seeking treatment

Nociception

Refers to neural encoding of future or actual tissue damage (noxious stimuli), physiological process

Research exists that shows pain can exist without what?

Nociceptive stimuli, examples: phantom pain, or perceiving pain that “isn’t really there”, fibromyalgia

Acute or subacute pain

Normal, physiological, and predicted response. Driven by chemical, thermal or mechanical stimuli. It is an evolutionary response for protection. Follows a predictable physiological pathway from stimulus to recovery (dependent on type of stimulus, severity, etc). Following tissue damage, response is usually mechanical followed by chemical in nature

Chronic or persistent pain

Abnormal response, does not serve protective or biological purpose, complex relationship between physiology and psychology, often relieved with rest

Somatic Pain

Related to the body (not blood vessels, organs, or nerves)

Viscerogenic Pain

Referred from organ systems and blood vessels

Neuropathic Pain

Relating to the nervous system (burning, tingling, numbness)

Referred Pain

Pain felt in an area not directly related to the pathology site

Radicular Pain

Relating to the spinal nerves

Radiculpathy

What happens to the nerves and causes radicular pain

Overview of Pain Pathway Process

Transduction (pain sensed, i.e. the finger), transmission (travels along the nerve endings and crosses over to the opposite side of the spinal cord to go to the brain), perception (stimuli perceived by the brain), modulation (tries to control the effects of the pain response)

Transduction of Pain

The nociceptive system requires strong stimulation before activating, activation will come from either mechanical (pressure or pinch), heat or chemical stimuli. Any tissue that contains free nerve endings involved with nociception is capable of being a source of “pain”

The action potential arising from nociceptors can be transported by what types of nerve fibers?

A-delta fibers and C fibers, both are first order neurons

Transmission of Pain

Transmitted by A-delta fibers and C fibers

A-Delta Fibers

Small, myelinated nerve fibers with a high conduction speed, the fast pain impulse is a signal telling the subject that a threat is present. A rapid, sharp, lancing pain reaction, and nearly instantaneous/reflexive response.

What kind of pain is referred to as first pain?

A-delta fibers

C Fibers

Small unmyelinated nerve fibers with a low conduction speed, respond to stimulus of higher intensity. Slow, dull, aching pain.

Referred to as second pain

C fibers

Pain Perception

Conscious awareness of pain (interpretation of pain)

What factors influence the interpretation of pain?

Cultural preferences, male and female roles, life experiences including past pain experiences (influences future pain experiences), and current expectations

Modulating Pain

Occurs before, during, or after pain is perceived

How do we modulate pain?

Altering speed signal (meditation/mindfulness), creating more input than the brain can decipher (rub it, which is a non-noxious sense of touch), desensitize or habituation stimulus (pain interrupting signal), and stimulating the release of natural pain killers (norepinephrine and endogenous opioids)