Unit 5 (Spinal Cord, Spinal Nerves, and Spinal Reflexes) Flashcards
Describe the structure and function of the spinal cord
Ok so you’ve got two branches: the ventral root, and the dorsal root and they have neurons that relay information from your body to your brain or the other way around
spinal nerve contains both sensory + motor neurons, and this is called “mixed nerves”
Ventral Root
a branch of spinal nerves, part of the spine’s anatomy, and they contain axons of motor neurons
Dorsal Root
a branch of spinal nerves, part of the spine’s anatomy, and they contain axons of sensory neurons; and also dorsal root ganglions contain cell bodies of senosroy neurons
Describe the location of the cervical, thoracic, lumbar, and sacral regions of the spinal cord
Top to bottom: cervical, thoracic, lumbar, and then sacral spinal nerves
Conus Medullaris
Terminal end of the spinal cord
Filium Terminale
a slender strand of fibrous tissue, extends from the inferior tip of the conus medullaris
Cauda Equine
bundle of nerves that projects from the inferior end of spinal cord, it’s made up of um bar and sacral spinal nerves
Arrangement of spinal cord
Top to bottom: cervical enlargement, lumbar enlargement, conus medullaris., and then filum terminale
White matter
contains mostly myelinated and some unmyelinated axons; each column contains tracts of fasciculi (bundles of axons relaying info up + down spinal cord)
you have 1) Ascending tracts, and 2) Descending tracts
Ascending Tracts
In white matter, carries info up TO the brain
Descending Tracts
In white matter, carries motor commands DOWN to the spinal cord
Enlargements
of the spinal cord; two made up of segments of grey matter
Cervical Enlargement
supplies nerves to the shoulders and upper limbs
Lumbosacral enlargement
innervates structures of the pelvis and lower limbs
Grey Matter
contains neuron cell bodies, and unmyelinated axons; it’s greatest in segments of the spinal cord dedicated to the sensory and motor control of limbs
Spinal Meninges
they’re specialized membranes that isolate spinal cord from its surroundings, and their jobs are to protect the spinal cord, carry blood supply, and they’re continuous w/cranial meninges
we have three: 1) dura, 2) arachnoid, and 3) pia
Dura Mater
Spinal meninge, the layer that forms the outermost/superficial layer covering the spinal cord; it’s made up of dense collagen fibers
Epidural Space
between the dura and walls of vertebral canal, and it is a region that contains aerolar tissue, blood vessels, and a protective padding of adipose tissue
Arachnoid Mater
the middle meninges layer, comes into contact w/inner dura; made up of a delicate network of collagen fibers; contains subarachnoid space
Subarachnoid Space
between the arachnoid membrane + outer surface of pia mater, FILLED w/CSF (cerebral spinal fluid)
Pia Mater
the subarachnoid space between the arachnoid epithelium and innermost meninges layer; a meshwork of elastic + collagen fibers that are firmly bound to underlying tissue
Tract
a bundle of axons relaying info up and down the spinal cord
Illustrate the anatomy of spinal nerves including each layer of connective tissue and the location of blood vessels
ok so you’ve got the 1) Epinerium, 2) Perinerium, 3) Endonerium
Epinerium
outer layer, contains blood vessels
Perinerium
middle layer, divides nerves fascicles (axon bundles)
Endonerium
inner layer, surrounds individual axons
Four major nerve plexus
Cervicle, brachial, lumbar, and sacral
Cervicle Plexus
innervates. neck, thoracic cavity, and diaphragmatic muscles
Brachial Plexus
innervates pectoral girdle + upper limbs
Lumbar Plexus
innervates anterior pelvic girdle + lower limbs
Sacral Plexus
innervates posterior pelvic girdle + lower limbs
Sensory Nuclei
Somatic: skin, muscles, and bone
Visceral: internal organs/structures
Motor Nuclei
Somatic: skeletal muscles
Visceral: autonomic nervous system
Reflex
autonomic responses to stimuli coordinated within CNS
Reflexive
1) arrival of stimulus
2) activity of a sensory neuron
3) information processing in the CNS
4) activation of motor neuron
5) response by peripheral effector
Withdrawal Reflexes
move body part away from stimulus (pain or pressure usually)
Postsynaptic Reflexes
1) more complicated than monosynaptic reflexes
2) interneurons controls more than one muscles group
3) involve EPSPs or IPSPs
Explain how the brain can impact spinal cord-based reflexes
reflexive behaviors are automatic, but processing centers in the brain can facilitate/inhibit reflex motor patterns based in spinal cord
ex: urination + defecation
trip and fall w/o or w/a valuable item in hand
blocking normal reflex- think Dr. Luckey + snake bite
Contrast the different classifications of reflexes
there’s 1) development, 2) response, 3) complexity of circuit, and 3) processing site
Development reflexes
Innate reflexes: genetically determined, formed at birth; also Acquired Reflexes: learned
innate examples: coughing, eating, blinking
acquired examples: riding a bike, driving a car
Response Reflexes
Somatic Reflexes: control skeletal muscle contractions and and include superficial and stretch reflexes; also Visceral (Autonomic Reflexes): control actions of smooth and cardiac muscles, glands, and adipose tissue
somatic examples: touching a hot plate and moving away
visceral examples: fight-or-flight response
complexity of circuit reflexes
monosynaptic: one synapse
polysynaptic: multiple synapse (two to several hundred)
processing sute reflexes
spinal reflexes: processing in spinal cord
cranial reflexes: processing in the brain
