Spinal Cord and Spinal Nerves Flashcards
Explain how spinal nerves are named
-named with letter corresponding to the region they are in (cervical, thoracic, lumbar, sacral, coccygeal) and a number
Number of pairs of spinal nerves attached to cervical area
8; (C1- C8)
Number of pairs of spinal nerves attached to thoracic (intercostal) area
12; (T1- T12)
Number of pairs of nerves attached to lumbar area
5; (L1- L5)
Number of pairs of nerves attached to sacral area
5; (S1- S5)
Define plexus
places where the nerves coming out are connected/ networked to each other
Name, locate, and identify the area supplied by the cervical plexus
C1-C5; neck
Name, locate, and identify the area supplied by the brachial plexus
C5-T1; shoulder
Name, locate, and identify the area supplied by the lumbar plexus
L1-L4; lower back
Name, locate, and identify the area supplied by the sacral plexus
L4-S4; hip/ butt
PROCESS
- sensory neurons come in; cell bodied are concentrated in posterior or dorsal root ganglion that anchor to spinal cord and provide pathways for axon of sensory neuron to come into spinal cord; sensory neuron goes into dorsal root of grey matter (non myelinated) and relays immediately with motor neuron (sometimes stimulates interneuron in between)
- motor response goes back through interior grey horn and comes out through anterior root
Define reflex and explain the differences between spinal reflexes and cranial reflexes
-reflex: fast, unplanned sequences in response to stimulus; involuntary, automatic response
- spinal reflexes: sensory signal goes to spinal cord and reroutes right back out from motor nerve to muscle
- ex. patellar reflex: stretching stimulates sensory receptor -> sensory neuron excited -> goes back to spinal cord, within integrating center (spinal cord), sensory neuron activates motor neuron -> motor neuron excited -> effector (same muscle) contracts and relieves the stretching
- cranial reflexes: goes to brain
- ex. pupillary reflex arc: light shines into eye -> light signal goes to brain through optic nerve -> signal comes back through nerves to stimulate muscle to contract
Explain the difference between somatic reflexes and autonomic (visceral) reflexes
- somatic reflexes: involve skeletal muscle and happen without your control (ex patellar reflex)
- autonomic reflexes: smooth or cardiac muscle (ex. pupillary reflex)
Define reflex arc (reflex circuit) and describe 5 components of a reflex arc
- sensory receptor: responds to stimulus by producing a generator or receptor potential
- sensory neuron: axon conducts impulses from receptor to integration center (spinal cord)
- integrating center: one or more regions within CNS that relay impulses from sensory to motor neurons)
- motor neuron: axon conducts impulses from integrating center to effector
- effector: muscle or gland that responds to motor nerve impulses
Ipsilateral, contralateral, and crossed extensor reflex
-ipsilateral: stimulus and response happen on same side (ex patellar reflex- the leg that gets struck is the same leg that jerks)
- contralateral: stimulus on one side and response on other side
(ex. pupillary reflex- iris in other eye also constricts
-crossed extensor reflex: ex step on tack and foot draws away (ipsilateral) and left leg immediately extends to maintain balance
Monosynaptic and polysynaptic
- mono: only one CNS synapse/ only one connection
- ex. sensory to motor neuron (patellar reflex)
- poly: multiple CNS synapses; goes through interneurons
- ex. sensory to inter, inter to motor (stepping on tac)
Describe the flexor (withdrawal) reflex, and explain why it would be described as intersegmental, ipsilateral, and polysynaptic
-ex when something is hot, remove hand right away
Meninges
-around brain and spinal cord
-dura mater: tough outer layer
(subdural space)
-arachnoid mater: middle layer
(sub arachnoid space - CSF)
-pia mater: inner layer (right on spinal cord)
Distinguish between sensory (ascending) and motor (descending) tracts and explain how most tracts are named
- sensory tracts go up spinal cord to brain
- motor tracts go from the brain down spinal cord
- named based on where they’re found and what they do (usually indicates position, beginning and end of tract)
Be able to identify the names of major sensory and motor tracts (such as spinothalamic and corticospinal tracts) and briefly describe their functions
- sensory tracts: spinothalamic, spinocerebellar
- spinothalamic = transmits pain, temp, and touch to thalamus
- motor tracts: corticospinal, rubrospinal, reticulospinal,, tectospinal
- corticospinal= from cerebral cortex to spinal cord; movement tract
Rami
branches that form first coming off of spinal nerves
dorsal ramus
- innervates deep muscles and skin of dorsal trunk (muscles and skin of back)
- ex. when bending over
ventral ramus
-innervates upper and lower limps and lateral and ventral trunk (all of core muscles, chest, arms, legs, etc)
meningeal ramus
-do short reroutes and come right back into vertibrae as well as blood vessels providing to spinal cord and meninges
ramus comminicans
-autonomic (loop with ganglion)
