peripheral nerves Flashcards
what is a neuron vs a nerve
- neuron: cordlike organ of PNS
- nerve: bundle of myelinated and un-myelinated peripheral axons enclosed by connective tissue, contain BV, (mitochondria must receive oxygen)
what is a plexus and examples of spinal nerves
plexi: network, grouped spinal nerves
- ventral rami of spinal nerves join one another to form a network
cervical: C1-C4
- S (neck, ear, back of head, shoulders)
- M (anterior neck muscles)
- phrenic (C3-C5, diaphragm)
brachial: complex, C5-C8 and T1, upper limb
- branches: roots (5), trunks (3 - upper, middle, lower), divisions (3 posterior 3 anterior), cords (3 - lateral medial posterior), 5 terminal branches
- 5 branches = axillary, musculocutaneous, median, ulnar, radial
lumbar: L1-L4, thigh, abdominal wall, psoas major (femoral / obturator)
sacral: L4-S4, buttock, lower limn, pelvic structures, perineum (sciatic, tibial common fibular)
what are the spinal nerve roots
- connection between nerve and spinal cord
- dorsal root (top): sensory afferent fibres, dorsal root ganglia, from peripheral receptors to CNS
- ventral root (bottom): motor efferent fibres, ventral horn, innervate skeletal, CNS to effector organ
- unite: to form spinal nerve, after emerging from its intervertebral foramina, further branches into a small dorsal ramus and larger ventral ramus
what are the sympathetic pathways
- paired system of nerves and ganglia (around 23), run lateral to vertebral bone and spinal cord
- pre / post ganglionic and ganglia
- pre: neurons in spinal cord (T1-L2), white ramus communicans
- synapse: between pre and neuronal cell body in ganglia
- post: join correspondant spinal nerve through gray ramus communicans
what is the radial nerve
- features: brachial plexus (largest),
- location: arm (upper and fore)
- innervates: posterior arm muscles (triceps brachii. anconeus, supinator brachioradialis)
- contraction: extensor muscles, supinate forearm, abduct thumb
- damage: wrist drop, superficial, inability to extend hand, improper use of clutch
what is the musculocutaneous nerve
- features: brachial plexus
- location: upper arm, sensory info from forearm
- innervates: biceps brachii, brachialis, coracobrachialis, skin of forearm
what is the ulnar nerve
- features: brachial plexus
- location: medially along ulna, continues to hand
- innervates: intrinsic muscles of hand
- contraction: flexion of wrist and fingers
what is the median nerve
- features: brachial plexus
- location: doesn’t branch in arm, descends into forearm
- innervates: anterior forarm, lateral palm, flexors (wrist and fingers), intrinsic of thumb
- contraction: pronate forarm, oppose thumb
what is the axillary nerve
- features: brachial plexus
- location: posterior to humerus, around scapula
- innervates: deltoid, teres minor, sensory from skin / shoulder
what is the femoral nerve
- features: lumbar plexus
- location: under inguinal ligament, anterior compartment
- innervates: quadriceps, extensors of knee
what is the sciatic nerve
- features: sacral plexus, longest / thickets in body
- location: posterior compartment, L4–S4
- innervates: hamstrings, adductor magnus (flexors of knee), buttock, lower limb, pelvic structures, and perineum
what is the tibial nerve
- features: sacral plexus
- location: posterior compartment of leg
- innervates: muscles of back of thigh, leg, and foot
what is the common fibular nerve
- features: sacral plexus
- location: anterolateral compartment of leg
- innervates: biceps femoris, lateral compartment of lower leg, tibialis anterior, extensor muscles of toes
what are disorders of the PNS
- shingles: herpes zoster, viral infection, stem from childhood, stress
- coldsores: herpes simplex 1, common, mouth / lips, trigeminal / facial nerve
- genital herpes: herpes simplex 2, viral, sexual contact
what are spinal reflexes
- reflex: protect, survive, learned activities
- stereotyped, fast, required stimuli, don’t go to brain
- acquired (inborn, intrinsic)
- learned (practice / repetition)
- pathway: stimuli, receptor, sensory neuron, integration centre, motor neuron effector
