Topic 19 -peripheral nervous system Flashcards
cranial nerves all 12 pairs
1 olfactory 2 optic 3 oculomotor 4 Trochlear 5 Trigeminal 6 Abducens 7 Facial 8 Vestibulocochlear 9 Glossopharyngeal 10 Vagus 11 Accessory 12 Hypoglossal
which cranial nerves are associated with the forebrain
1 olfactory
2 optic
which cranial nerves are associated with the midbrain
3 oculomotor
4 trochlear
which cranial nerves are associated with the pons
5 trigeminal
6 abducens
7 facial
8 vestibulocochlear
which cranial nerves are associated with medulla oblongata
9 glossopharyngeal
10 vagus
11 accessory
12 hypoglossal
2 pairs of cranial nerves are only Sensory
sensory
1 olfactory
2 optic
1 pair of cranial nerves is mainly sensory
sensory
8 vestibulocochlear
9 pairs of cranial nerves are
mixed nerves
- carry both sensory + motor neurons
- motor neurons ⇒ cell bodies in brainstem nuclei
- sensory neurons ⇒ cell bodies in ganglia of PNS
- e.g. trigeminal (V)
- motor function = chewing
- sensory function = conveys general sensations (touch, pressure, pain, temperature etc) from face to CNS
Spinal nerves
- 31 pairs = all mixed nerves
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
spinal nerves exit at
exit via intervertebral foramina (except 1st - between atlas + occipital bone
each spinal nerve has two points of attachment to spinal cord:
a) Dorsal Root
- sensory; cell bodies in dorsal root ganglion
b) Ventral Root
- autonomic and somatic motor neurons; cell bodies in ventral or lateral horn
- spinal nerve = joining of dorsal + ventral roots
- immediately divides into branches = rami:
a) dorsal ramus
innervates skin + muscles of back
b) ventral ramus
- forms thoracic nerves (T2 - T12) OR further branch + join up forming nerves plexuses (= nerve networks)
c) rami communicantes
- connect ventral ramus to sympathetic trunk
- contain autonomic nerve fibres (neurons)
cervical plexus
C1-C5
phrenic (innervates diaphragm)
brachial plexus
C5-C8, T1
Axillary, radial,ulnar, median, musculocutaneous
Lumbar plexus
L1-L4
femoral
Sacral
L4-S4
sciatic => divides into tibial and common fibular
Peripheral Nervous system: Sensory (Afferent) Division
consists of
stimulus -> receptor -> CNS
Receptors
First order Neurons
Receptors
detect changes in environment classified by location type of stim received structure of receptor
receptors classified by location
i) exteroceptors
- stimulus in external environment = receptors at body surface e.g. touch, most special senses)
ii) interoceptors
- stimulus in internal environment (in viscera, blood vessels etc)
iii) proprioceptors
- located in joints, skeletal muscles etc
- monitor body position (stretch receptors, muscle spindles) – balance + movement
receptors classified based on type of stim received
i) mechanoreceptor- mechanical stimuli (e.g. pressure, touch, hearing)
ii) thermoreceptors- temperature
iii) chemoreceptors- chemical
iv) photoreceptors- light
v) nociceptors - pain`
receptors based on structure
i) free nerve endings - terminal dendrites of unipolar sensory neurons e.g. pain, root hair plexus
ii) encapsulated nerve endings - terminal dendrites enclosed in CT
e. g. Meissner’s + Pacinian corpuscles
First Order Neurons = sensory neurons
Cell bodies where
Axon terminates where
- unipolar neurons attached to or associated with receptor
- axon located in cranial/spinal nerves to CNS
- cell bodies in:
a) sensory ganglia of cranial nerves
b) dorsal root ganglia of spinal cord-
axon terminals in:
a) brain nuclei
b) dorsal horn of spinal cord
Peripheral system: Motor (efferent) Division
CNS => effector (E)
2 subdivisions
somatic
autonomic
Somatic peripheral nervous system
- effector = skeletal muscle
- consists of lower motor neurons (= motor neurons):
= single multipolar neuron:
a) cell body in ventral horn of spinal cord to effector
b) cell body in motor nuclei of brain stem to effector (e.g. facial motor nucleus for cranial nerve VII)
Autonomic division of nervous system
- effector = smooth muscle, cardiac muscle, glands
- 2 successive multipolar neurons from CNS to effector:
a) preganglionic neuron - myelinated
- cell body in brain stem or lateral horn of spinal cord
b) postganglionic neuron - unmyelinated
- cell body in autonomic ganglion (outside CNS)
2 subdivisions of autonomic nervous system
a) Sympathetic (SNS)
b) Parasympathetic (PSNS)
Differences between SNS and PSNS for Cell body of preganglionic neuron
SNS: lateral horn T1 => L2
PSNS: Brain stem S2=>S4
Differences between SNS and PSNS for Autonomic ganglia
SNS: Trunk (either side of column) OR collateral (ant to vert column or close to large abdominal arteries)
PSNS: terminal (at or in organ/effector wall)
Differences between SNS and PSNS for Postganglionic neurons
SNS: long axons
PSNS: Short axons
Adrenal medulla= modified postganglionic neurons of SNS
Differences between SNS and PSNS for Functions
SNS: flight or fight
PSNS: Rest and digest
Differences between SNS and PSNS for exit CNS (nerves)
SNS: mainly as thoracic nerves
PSNS: mainly 80% via vagus (cranial nerve X)
