week 3 Flashcards
anticholinergic drug example and side effects
amitriptyline
constipation, dry mouth, dry eyes, tachycardia, urinary retention, agitation, confusion,
what is the difference between unipolar and multipolar neurons?
Unipolar/pseudounipolar:
Sensory neurons
Have cell body in the PNS
Have only one projection of dendrites
Multipolar:
Motor neurons
Have cell body in the CNS
Have multiple projections of dendrites
how many pairs of spinal nerves are there?
31:
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
where are spinal nerves present?
in the intervertebral foramen
how are spinal nerves named?
cervical named according to the vertebra BELOW
C8 comes between C7 and T1 vertebrae
cervical onwards named according to vertebra ABOVE
explain spinal nerves, roots, rootlets, horns etc
Dorsal and ventral rootlets come from the ‘H’ region of the spinal cord.
all motor axons originate from the anterior horn
all sensory axons pass to the posterior horn
The rootlets converge to form larger structures called roots:
* Ventral roots –> motor (and so technically come OFF of the spinal cord)
* Dorsal roots --> sensory (and so technically go INTO the spinal cord)
Dorsal roots have a dorsal root ganglion. These contain the cell bodies of primary afferent neurons.
The dorsal and ventral roots then converge to form a spinal nerve. This has both motor and sensory elements.
The spinal nerve divides into a ventral and dorsal ramus (plural rami). These are mixed – have both motor and sensory nerve fibres.
* The posterior rami is smaller and supplies the posterior body wall * The anterior rami is larger and supplies the anterolateral body wall
what do spinal nerves supply their body segment with?
general sensory supply
somatic motor supply to skeletal muscles
sympathetics to skin, arteriole smooth muscle
what part of the spinal nerve are nerve plexuses formed of?
the anterior rami
name the 4 bilateral nerve plexuses, their nerve roots and what they supply
cervical plexus: C1-4
posterior scalp, neck and diaphragm
brachial plexus: C5-T1
upper limb
lumbar plexus: L1-4
lower limb
sacral plexus L5-S4
lower limb, gluteal region and perineum
describe the sympathetic chain
Control centres in the brain send signals down the spinal cord. These travel in the sympathetic chain: two chains on either side of the vertebrae across its entire span. It is also known as the prevertebral chain.
The sympathetic information traveling in the chain can only exit via the lateral horn (T1-L2). This is why sympathetic innervation is also known as thoracolumbar outflow.
information exits the lateral horn via a ventral root, then enters the sympathetic chain via a white ramus communicantes. if there is a synapse within the chain, the info leaves the chain via a gray ramus communicans to rejoin the spinal nerve
what happens to neurons that pass through the sympathetic chain without synapsing?
Greater/lesser/least/lumbar/sacral splanchnic nerves then travel to and synapse at prevertebral ganglia in the abdomen. these are nerve networks around the abdominal aorta and its branches (coeliac plexus, aortico-renal plexus, sup/inf mesenteric plexuses)
travel directly to the adrenal medulla and synapse with chromaffin cells
describe the sympathetic innervation of the heart
- Presynaptic axons synapse in T1 or travel up to synapse at cervical paravertebral ganglia (symp chain)
- Post synaptic axons go to via cardiopulmonary splanchnic nerves to the SA and AV nodes and the myocardium
Note: this is an exception to the concept that splanchnic nerves do not synapse in the sympathetic chain
describe the sympathetic innervation of the lungs
- Presynaptic axons synapse in the upper thoracic paravertebral ganglia
- Post synaptic axons go via cardiopulmonary splanchnic nerves to the bronchiolar smooth muscles and mucous glands
what are the ganglia that splanchnic nerves synapse on for each region of the gut’s sympathetic innervation?
foregut: coeliac ganglion
midgut: superior mesenteric ganglion
hindgut: inferior mesenteric ganglion
nerve roots for greater, lesser and least splanchnic nerve
Greater splanchnic nerve = T5-9
Lesser splanchnic nerve = T10-11
Least splanchnic nerve = T12