Peripheral Nervous System Flashcards
What does the peripheral nervous system consist of?
Nerves (cranial and spinal) Ganglia Outside of the spinal cord
What are the 2 major modalities of the PNS?
Somatic Autonomic
What carries information towards the CNS?
Sensory (afferent) nerves
What carries information away from the CNS?
Motor (efferent) nerves
How many pairs of cranial nerves are there?
12
How many pairs of spinal nerves are there?
31
What is a plexus?
Area where a number of nerve fibres enter and exit under different named nerves Network of interconnecting nerves
What is the function of somatic afferent nerves?
Convey information from skin, skeletal muscle and joints
What is the function of somatic efferent nerves?
Convey information to skeletal muscles
What is a dermatome?
An area of skin that is supplied by a single spinal nerve
What is a myotome?
Group of muscles innervated by a single spinal nerve
What in the function of visceral afferent nerves?
Carry information from the viscera
What is the viscera comprised of?
Thoracic, abdominal and pelvic organs
What can visceral efferent nerves divided into?
Sympathetic Parasympathetic
What is the function of sympathetic efferent nerves?
Innervate the viscera and periphery
What is the periphery comprised of?
Vasculature and sweat glands
What is the function of parasympathetic efferent nerves?
Innervate the viscera only
What is a ganglion?
Collection of cell bodies outside the CNS
What is a nucleus?
Collection of cell bodies inside the CNS
Where of afferent fibres have their cell bodies?
In spinal ganglia
Where fo Visceral efferent nerves synapse?
In the periphery ganglion
How are peripheral nerves arranged?
In fasciculi (bundles)
What are the layers of connective tissue of a spinal nerve?
External vascular layer- epineurium Individual fascicles covered in -perineurium Individual axons covered in- endometrium
How are peripheral nerves classified?
Two systems 1. Conduction velocity A,B,C with A the fastest 2. Axonal diameter (sensory only) I-IV with I the largest
What is the function of sensory receptors?
Detect external or internal infomation
How can sensory receptors be classified?
Source of stimulus Mode of detection
How are sensory receptors further classified under source of stimulus?
External - Exteroceptors (pain, temperature, touch and pressure) Internal - Proprioceptors (movement and joint position) - Enteroceptors (movement through gut and blood pH)
How are sensory receptors further classified under mode of detection?
Chemoreceptors Photoreceptors Thermoreceptors Mechanoreceptros Nociceptros
What is the function of proprioceptors?
Muscle spindles: Detect changes in muscle length Gogli tendon organs: Detect changes in tension in tendons Joint receptors: Detect start and end of movement
What is a neuromuscular junction?
Specialised synapse between a motor neurone and muscle fibre
What is a motor unit?
Single lower motor neurone and all of the muscle fibres it goes to No muscle fibre is innervated by more than one nerve
What is a reflex action?
Involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
What is the function of visceral sensory nerves?
Relay sensory information from the core Pain, fullness, blood pressure T1-L2, S2-S4 and cranial nerves IX and X
What is the function of visceral motor nerves?
Outflow to core and body wall Controls pupil, sweat glands, salivary glands, heart muscle and airways Thoracolumbar (T1-L2) Craniosacral outflow (nerves III, VII, IX and X)
Where do nerves going to the viscera synapse?
On the aorta No synapse in sympathetic trunk
What is the branch that connects the spinal cord to other parts of the body?
Dorsal root ganglion
Label parts A-D
A- Dorsal root
B- Dorsal root ganglion
C- Plexus
D- Ventral root
What must happen for all sensation from a body part to be lost?
Multiple nerves innervate an area
All the nerves supplying a region must be damaged
What is a dermatome?
A localised area of skin that is has its sensation via a single nerve from a single nerve root of the spinal cord
Genrally, how many nerve innervate a muscle ?
2-3 but varies
Give the medical terms for injuries that cause lesions at each of the indicated points
V and W: Strain injury or Prolapse disc
Y and Z: Trauma or Peripheral neuropathy
X- Trauma
What would each of the lesions result in?
V: Loss of sensation
W: Muscle weakness
X: Loss of sensation and Muscle weakness
Y: Complete loss of sensation
Z: Complete loss of movement
What is Sciatica?
Lumbar spinal radiculopathy
What can cause Scaitica?
Nerve compression
Prolapsed disc
Damage to vertebrae
Arthritis
Piriformis syndrome
How do you diagnose Sciatica?
Stretch-raise test
If there is pain explore further
How is Sciatica treated?
Analgesic medication e.g. Ibruprofen
Physiotherapy
Epidural injection to the sacral portion of the spine
If it exacerbates, decompression surgery
Disectomy to repostion the disc
