PNS Flashcards
_____ branches of peripheral nerves supply the skin and subcutaneous tissues; ______ branches supply the muscles, tendons, and joints.
Cutaneous; muscular
What do anterior rami supply? What do posterior rami supply?
Anterior (for plexuses) = Supply anterior/lateral trunk and extremities
Posterior = Supply skin and muscles at and around the spine
What is the function of movement of nerves?
- Helps maintain the health of nerves
- Promotes blood flow in a nerve
- Promotes movement of axoplasm
What does the motor component of cutaneous branches of peripheral nerves innervate?
- blood vessels
- sweat glands
- m’s that make hair stand up
What does the motor component of muscular branches of peripheral nerves innervate?
- skeletal muscle
2. blood vessels in muscle
What does the sensory component of muscular branches of peripheral nerves innervate?
- joint receptors
- GTOs
- muscle spindles
- pain receptors in m’s
(Kinesthesia, proprioception, pain)
What can happen with excess lengthening of neural tissue?
Tensile stress develops in neural structures; Excessive stretch can damage connective structures and axons
What happens when peripheral nerves are at rest? when they are lengthened?
Axons wrinkle within the endoneurium;
With lengthening of a nerve:
1.Tubes of endo-, peri- and epineurium stretch
2. Axons unwrinkled
3. Fascicles glide relative to each other
Provides cutaneous sensory information from the posterior scalp to the clavicle.
Innervates the anterior neck muscles and diaphragm.
Cervical plexus:
C1-C4
Deep to SCM
Entire upper limb is innervated by the branches.
Brachial plexus:
C5-T1
Between anterior and middle scalene m’s, deep to the clavicle and into the axillary region
Branches innervate the skin and muscles of the anterior and medial thigh
Lumbar plexus:
L1-L4
Forms in psoas major
Innervates the posterior thigh and most of the leg and foot; contains parasympathetic axons.
Sacral plexus:
part of L4 – S4
Dermatomes: Face – Remainder of head – Nipple line – Umbilicus –
Face - Trigeminal (CN5)
Remainder of head – C2
Nipple line – T4
Umbilicus – T10
Dermatomes of UE: C4 – C5 – C6 – C7 – C8 – T1 –
C4 – top of shoulder C5 – shoulder and lateral arm C6 – lateral forearm and first 2 digits C7 – Middle digit C8 – 4th and 5th digits T1 – Medial arm and forearm
Dermatomes of LE: L2 – L3 – L4 – L5 – S1 – S2, S3, S4
L2 – anterolateral thigh
L3 – anteromedial thigh and knee
L4 – anteromedial shin
L5 – anterolateral shin and top of foot to big toe
S1 – small toe, lateral foot, sole and calf
S2, S3, S4 perineal region
Where are disc herniations most common? what nerve roots are involved?
Cervical and lumbosacral;
Nerve root involved usually corresponds to the lower of the adjacent two vertebrae
Even without an action potential, the presynaptic terminal continuously releases small amounts of Ach, one vesicle at a time; This produces small depolarizations in the muscle. What is the small depolarization called?
Miniature End Plate Potentials (MEPPS)
What is the fiction of mEPPs? What does the loss of mEPPs indicate and produce?
Function - promote muscle health
If there are no mEPPs:
- Nerve is injured
- Muscle atrophy (fast and drastic, as in LMN injury)
autoimmune disease that damages ACh receptors at the neuromuscular junction; Repeated use of a muscle leads to increasing weakness.
Myasthenia gravis
causes blocks the release of ACh from the motor axon; Produces acute, progressive weakness, with loss of stretch reflexes; sensation remains intact
Botulism
Disorder intrinsic to muscle;l Paresis; Often more proximal than distal weakness; NOT due to dysfunction of the nervous system
Myopathy
i.e., muscular dystrophy
Disorders of peripheral nerves
neuropathy
What are the sensory changes seen in neuropathies?
- Include decreased or lost sensation.
- Abnormal sensations include the following:
Hyperalgesia
Dysesthesia
Paresthesia
Allodynia
What are the autonomic changes seen in neuropathies?
Single nerve: Signs are usually observed only if the nerve is completely severed.
Many nerves: Problems may include difficulty regulating blood pressure, heart rate, sweating, bowel and bladder functions, and impotence.
What are the motor changes seen in neuropathies?
- paresis or paralysis
- If the muscle is denervated, electromyogram (EMG) recordings show no activity for +/-1 weeks after the injury.
- Muscle atrophy progresses rapidly
- Fibrillations
What are the trophic changes seen in neuropathies?
- Changes that occur in the denervated tissues: Skin becomes shiny, Nails become brittle, Subcutaneous tissues thicken
- Changes in blood supply, sensation and lack of movement: Ulceration of cutaneous and subcutaneous tissues, Poor healing of wounds, Increased risk of infection, Neurogenic joint damage
Involves a single nerve and is considered a focal dysfunction
Mononeuropathy
Involves several nerves and is multifocal (i.e., asymmetrically involves individual nerves); Individual nerves are affected, producing a random, asymmetrical presentation of signs
Multiple mononeuropathy
Involves many nerves and is a generalized disorder that typically has a distal and symmetrical presentation
Polyneuropathy
- Hallmark signs include symmetrical involve-ment of sensory, motor, and autonomic fibers, often progressing from distal to proximal
What are the three categories of mononeuropaties?
- Traumatic myelinopathy - Neurapraxia
- Traumatic axonopathy - Axonotmesis
- Severance - Neurotmesis
Refers to the loss of myelin limited to the site of injury; interfere with the function of large-diameter axons; cause is focal compression of a peripheral nerve (can be due to repeated mechanical stimuli)
Traumatic myelinopathy
- recovers
With recovery from traumatic myelinopathy, what is the difference you see in schwaan cells as they regenerate?
They come back much shorter
Disrupts axons and Wallerian degeneration; occurs distal to the lesion; affect all sizes of axons; reflexes, somatosensation, and motor functions are significantly reduced or absent; regenerating axons are able to reinnervate appropriate targets because myelin and connective tissues remain intact
Traumatic axonopathy
- recovers
Occurs when nerves are physically divided by excessive stretching or a laceration; Axons and connective tissue are completely interrupted; If proximal and distal nerve stumps are apposed and scarring does not interfere, some sprouts enter the distal stump and are guided to their target tissue in the periphery
Severance
- results in immediate loss of sensation and/or m paralysis
- poor recovery
What may cause multiple mononueropathy?
vasculitis
What are causes of polyneuropathy?
Cause can be toxic, metabolic, or autoimmune.
- Most common causes include diabetes, nutritional deficiencies secondary to alcoholism, and autoimmune diseases
- Variety of therapeutic drugs, industrial and agricultural toxins, and nutritional disorders can cause polyneuropathy
The most common inherited polyneuropathy; Generally causes paresis of muscles distal to the knee with resulting foot drop, step-page gait, frequent tripping, and muscle atrophy; in progression, muscle atrophy and paresis affect the hands; Onset typically occurs in adolescence or in young adults but varies with the type
Charcot-Marie-Tooth disease
What are the causes of diabetic polyneuropathy?
- vascular changes
- metabolic changes
- usually distal symmetrical polyneuropathy
What part of the nerve is injured in diabetic polyneuropathy? what functions are predominantly affected?
axons and myelin sheaths;
Sensory neurons: Decreased sensations, Pain, Paresthesias, Dysesthesias
What type of exercises may enhance sensory and motor recovery? what may delay functional recovery/
Enhance - endurance exercise
Delay - resistance training
