Peripheral Nervous System, Pain Flashcards
What are the functions of the peripheral nervous system (PNS)?
Serves as the communication system of the body.
Sends sensory information to the brain (afferent).
Transmits motor commands from the brain to the body (efferent).
How many pairs of cranial and spinal nerves are in the PNS?
Cranial Nerves: 12 pairs (11 are part of the PNS; the second is part of the CNS).
Spinal Nerves: 31 pairs, corresponding to vertebral segments.
What is the difference between dermatomes and myotomes?
Dermatome: Area of skin supplied by a single spinal nerve.
Myotome: Group of muscles controlled by a single spinal nerve.
What are the two main divisions of the PNS?
Somatic Nervous System: Voluntary, conscious control.
Autonomic Nervous System: Involuntary, regulates internal processes.
What are the subdivisions of the autonomic nervous system?
Parasympathetic: Rest and digest; cranio-sacral nerves.
Sympathetic: Fight or flight; thoraco-lumbar nerves.
Why does the central nervous system (CNS) not regenerate well?
Lack of a supportive environment for nerve regeneration.
Presence of inhibitory molecules and glial scarring.
What is Wallerian degeneration and regeneration in nerve injury?
Wallerian Degeneration: Breakdown of the axon distal to the injury.
Regeneration: Growth of the axon toward the target tissue, facilitated by Schwann cells in the PNS.
What are the key structural components of a nerve?
Epineurium: Outer layer surrounding the entire nerve.
Perineurium: Surrounds bundles of nerve fibers (fascicles).
Endoneurium: Encloses individual nerve fibres.
What is the vagus nerve, and why is it significant?
A cranial nerve in the PNS.
Extends to vital organs from the neck to the colon.
Plays a role in autonomic control, especially the parasympathetic system.
How do parasympathetic and sympathetic systems differ in function?
Parasympathetic: Maintains body at rest, promotes digestion and relaxation.
Sympathetic: Prepares body for stress, increases heart rate, and redirects blood to muscles.
How does the International Association for the Study of Pain (IASP) define pain?
“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
What are the key components of the pain pathway?
Stimulus: Activation of nociceptors.
Transmission: Signal travels via sensory neurons.
Spinal Response: Reflex responses may occur.
Registration: Brain processes the signal.
Modulation: Brain and spinal cord adjust the pain signal.
What are the types of sensory neurons involved in pain transmission?
Aδ fibers: Small/medium diameter, myelinated; transmit fast pain
.
C fibers: Small diameter, non-myelinated; transmit slow pain.
Aβ fibers: Large diameter, myelinated; transmit mechanical stimuli.
What is the pain gate theory?
Ascending inhibition: Aβ fibers (e.g., rubbing) inhibit pain transmission.
Descending inhibition: Brain signals (e.g., relaxation) suppress pain by releasing endorphins and encephalins, closing the pain gate.
What factors affect the pain gate?
Other impulses: Pressure (Aβ fibers) can close the gate.
State of mind: Anxiety opens the gate, relaxation closes it.
Central control: Past experiences and memories influence pain perception.
Endorphins/Encephalins: Increase with exercise or acute trauma, closing the gate.
What are the types of pain?
Acute Pain: Short-term, linked to injury or tissue damage.
Chronic/Persistent Pain: Lasts beyond healing time, may lack an identifiable cause.
Nociceptor Pain: Related to tissue damage.
Neuropathic Pain: Caused by nerve damage.
Nociplastic Pain: Due to dysfunctional nociceptive processing.
What are common psychosocial factors that influence pain?
Fear Avoidance: Misinterpreting pain, leading to avoidance and hypervigilance.
Catastrophizing: Exaggerated negative thoughts about pain (e.g., “I can’t bend because of my spine”).
Pain Behaviours: Observable actions like guarding, bracing, or grimacing.
What are “red flags” for back pain that indicate serious pathology?
Cauda equina symptoms (bladder/bowel dysfunction, saddle anesthesia).
Age <20 or >55 with back pain onset.
History of cancer, significant trauma, weight loss, or widespread neurology.
Constant, night, or bilateral pain.
What are “yellow flags” for chronic pain?
Negative attitudes and beliefs about pain.
Maladaptive behaviors (e.g., avoidance, overcompensation).
Family or workplace stress.
Emotional factors like anxiety or depression.
How do cognitive functional therapy (CFT) and cognitive behavioral therapy (CBT) help in managing chronic pain?
Reconceptualize Pain: Change faulty thoughts and movements.
Coping Skills: Train patients to manage pain effectively.
Behavioral Practice: Gradual exposure to activities.
Relapse Prevention: Strategies to maintain progress.
