Lab Spinal Nerves And Spinal Reflexes Flashcards
Where do spinal nerves originate?
- from the spinal cord
- pass through an intervertebral foramen, as they exit the vertebrae
- exception: Between skull and C1 and sacrum group (sacral foramina)
31 pairs if spinal nerves, form 5 groups:
- cervical nerves 1-8
- thoracic nerves 1-12
- lumbar nerves 1-5
- sacral nerves 1-5
- coccygeal nerves 1 pair
Divisions of spinal nerves as they branch towards the periphery of the body:
- roots
- rami
- plexuses
Roots
- attached directly to the spinal chord
* join to form spinal nerves
Two roots:
- dorsal root: carries sensory (afferent) info to dorsal horn of the spinal cord
- ventral root: carries motor (efferent) responses to the effector organ
Rami (branching)
•after leaving the spinal cord spinal nerve forms 2 sometimes 3 branches called rami
2 ramus
- dorsal ramus
* ventral ramus
Dorsal ramus
- sensory and motor nerve fibers
* motor: innervate most if the deep muscles of the dorsal trunk, responsible for movement of the vertebral column
Ventral ramus: distributed two ways-
- Thoracic region- form intercostal nerves, extend along inferior margin of each rib
- innervate the intercostals muscles and skin over the thorax - Plexus: remaining from the 5 major plexuses
- Communicating rami: form thoracic and upper lumbar spinal cord regions, carry axons associated with the synaptic division if ANS
- connect to synaptic chain ganglia
Plexus
Intricate networks of spinal nerves in a braid like structure
5 plexuses of the spinal nerves
•cervical •brachial •lumbar •sacral •coccygeal *then branch off plexuses to reach all parts of trunks and limbs
3 types of nerve calls that carry information between the spinal cord and peripheral nerves:
Somatic motor neurons
Autonomic motor neurons
Sensory neurons
Somatic motor neurons
Control contraction of skeletal muscles in the neck, trunk and limbs
Sensory neurons
Detect skin sensations and muscle position or stretch (proprioception)
Autonomic motor neurons
These motor neurons form pathways leading to internal organs of the head, chest and abdomen
Name the two upper plexuses of the spinal cord
Cervical plexus
Brachial plexus
Name the three lower plexuses of the spinal cord
Lumbar plexus
Sacral plexus
Coccygeal plexus
Cervical plexus
- composed of ventral rami of cervical nerves C1-4
- controls actions of head neck shoulders
- receives sensory info from the skin in these areas
Brachial plexus
- arises from the ventral rami of cervical nerves 5-8 (C5-T1)
- controls arm, forearm and hand
- receives sensory info from skin in these areas
- most complex plexus
- 3 trunks, 2 divisions, 3 cords
Lumbar plexus
- from ventral rami of lumbar nerves 1-4 (L1-4)
- ventral rami form anterior and posterior divisions
- then branch to form peripheral nerves
Sacral plexus
- is lumbar 5 and sacral 1-3 spinal nerves
- ventral rami of these nerves form anterior and posterior divisions
- lead to peripheral nerves
Coccygeal plexus
•composed of ventral rami from sacral nerves 4 and 5, and the coccygeal nerves
What four plexuses arise from or originate from the ventral rami?
Cervical plexus
Brachial plexus
Lumbar plexus
Coccygeal plexus
3 divisions of the autonomic nervous system ANS
•sympathetic
•parasympathetic
•enteric
( all control actions of the internal organs)
Arrangement of cells
•nerve cells originate in brain or spinal cord
•pass to internal organs via cranial or spinal nerves
•pathway to organs is a two cell circuit
-w/ a junction between cells forming a ganglion
Parasympathetic pathways
- originate in cranial nerves (III, VII, IX, X) of the brain
* or in sacral region S2-4 (pelvic splanchnic nerves)
Parasympathetic pathways: cell bodies of preganglionic neurons located in the brain stem and sacral regions of the spinal cord (craniosacral):
Usually involve activating vegetative functions
Ex digestion
Dedication
Urination
Vagus nerve
Cranial nerve
•extends from brain into chest and abdomen to control internal organ functions
•joins with sympathetic nerves to form plexuses around stomach and heart
Pelvic nerves
Originated from spinal nerves S2-4
•pass through ventral rami
•then form nerves leading to pelvic organs
Sympathetic pathway (fight or flight)
Originate from spinal nerves T1-L2
•motor nerves pass through spinal nerves to form special nerves
•or end in ganglion, in one of two chains of ganglia that parallel spinal cord
Cell bodies of sympathetic pthwy preganglionic neurons located in the thoracic and upper lumbar regions (thoracolumbar):
Usually involve with preparing body for physical activity
Main nerves of sympathetic pathways
Sympathetic
Splanchnic
Spinal reflexes
- involuntary automatic predictable response to stimuli
- purpose: self preservation
- somatic: removal from painful stimuli
- autonomic: blood pressure
Reflex pathways (arcs)
- a functional unit composed of a series of nerve cells
* follow a specific pathway to and from the spinal cord
General pathway
- info travels into and out of spinal cord in one direction only
- impulse pathway may either pass upwards towards the brain or downward to activate other muscle groups
Reflex pathway components
1 sensory receptor 2 sensory neuron 3 interneuron 4 motor neuron 5 effector organ
Somatic motor and sensory nerve pathways: cervical 1-4
Plexus: cervical
Peripheral nerves: phrenic
- muscles and skin of the head neck and shoulder
- diaphragm
Somatic motor and sensory nerve pathways: cervical 5-8
Thoracic 1
Plexus: brachial
Peripheral nerves:axillary, musculocutaneous, median, radial, ulnar
•muscles and skin of the shoulder arm,forearm, arm forearm and hand
Somatic motor and sensory nerve pathways: thoracic 2-12
- no plexus
- peripheral nerves: intercostals
- muscles between the ribs; skin of the chest and abdomen
Somatic motor and sensory nerve pathways: lumbar 1-4
•Plexus: lumbar
•peripheral nerves: lliohypogastric-
muscles and skin of the abdomen and buttocks
llioinguinal- skin and muscles of external genitals and abdomen wall genitofemoral- external genitals
femoral- skin and muscles if the anterior hip and thigh
obturator-muscles and skin of the median thigh
•
Somatic motor and sensory nerve pathways: lumbar 5, sacral 1-3
•plexus: sacral
•peripheral nerves: **sciatic- tibial: posterior thigh and leg, muscles and skin
median and lateral planter: posterior and planter foot, skin and muscles
Common peroneal fibular: superficial and deep peroneal: anterior leg and foot, skin and muscles
**pudendal: perineum and external genitals skin and muscles
Somatic motor and sensory nerve pathways: sacral 4-5, coccygeal
Plexus: coccygeal
•nerves: coccygeal
•perineum and coccyx skin and muscles
Patellar reflex test
Femoral nerve
Triceps brachii reflex test
Radial nerve
Autonomic motor nerves: Sympathetic division
- communicating rami
- superior and inferior cervical ganglia
- chain ganglia
- organ plexuses (esophagus, heart, stomach)
Autonomic motor neurons, parasympathetic division
Vagus nerve
Organ plexuses