Lectures 12 & 13 Flashcards
three branches of the PNS once exiting the vertebral column
dorsal root ganglion, dorsal ramus, ventral ramus
types of axons in the spinal cord
- 50% sensory (afferent)
- 40% postganglionic sympathetic (autonomic efferent)
- 10% motor (voluntary efferent)
purpose of myelinated vs unmyelinated axons
myelinated: motor, touch, pressure and propreoception
unmyelinated: pain, temperature
3 main arteries in the spine
- posterior spinal artery
- radicular arteries
- anterior spinal artery
(image 3)
spinal levels
- cervical (8)
- thoracic (12)
- lumbar (5)
- sacral (5)
- coccygeal (none)
which is longer, the spinal cord or the vetebral canal? (image 4)
vertebral canal, spinal cord ends at L2 but nerve roots extend further via cauda equina
3 spinal nerve groups (image 5)
- brachial plexus (C5 - T1) M + S to upper limbs
- intercostal nerves (T1 - T12) M + S to body wall
- lumbosacral plexus (L2 - S4) M + S to lower limbs
types of sensation
quantitative
- mechanoreception (touch and pressure)
- propreoception (location)
qualitative
- thermoreception (temperature)
- nocioception (pain)
what do free nerve endings sense?
pain and temperature
what do corpuscles sense?
pressure and touch
what senses propreoception in muscles?
muscle spindles (eg: tendon organ)
differences in the afferents for each type of sensory nerve
nocioception + thermoreception
- small, little myelin
mechanoreception
- medium, light-heavy myelin
propreoception
- large, heavy myelin
Monosynaptic reflex arc
stimulus (in kneecap for example) lengthens the muscle splindles, sends message to afferent neuron, sends message to motor(efferent) neurons (contracts quad and relaxes hamstring) also sends message to thalamus
Crossed-extensor reflex
painful stimulus activates nociceptor (afferent), withdrawal relflex triggered by motor neurons (efferent) activates both sides of the body (eg: lifting leg requires muscle contraction in both legs), also sense message to thalamus
hypergalesia
painful stimuli feel more intense than they should
