Spinal cord/nerves Flashcards
Protecive structures of spinal cord
vertebral column and meninges (continuous with cranial meninges)
- epidural space = adipose tissue
- dura mater = dense collagen
- arachnoid mater w/ subarachnoid space for CSF
- Pia mater : denticulate ligament and filum terminale
Where are the two enlargements?
cervical and lumbar
what are the two middle crevices called?
What are the white areas around the horns called?
Ventral/Anterior median fissure
Dorsal/Posterior median sulcus
Funiculi
Spinal nerves: numbers for each section
C1-C8 = cervical T1-T12 = Thoracic L1-L5 = Lumbar S1-S5 =Sacral CO1 = coccygeal
Connective tissue coverings of spinal nerves
endoneurium = around individual fibers perineurium = bundles of nerve fibers (fasicle) epineurium = around multiple fasicles
Rami
- Dorsal rami sense and motorize dorsal side of body (mixed nerves)
- Ventral rami make up plexuses everywhere except T2-T12
Cervical Plexus
C1-C5
-Includes phrenic nerve = innervates diaphragm
Brachial Plexus
- C5-T1
- Shoulders and upper limbs
- roots merge into trunks which divide into divisions which merge into cords which divide into nerves
- axillary, radial, ulnar, musculocutaneous, median, long thoracic
- Injuries cause issues with arm
Lumbar Plexus
L1-L4
- anterolateral abdominal wall, external genitals, and part of lower limb
- femoral nerve and obturator nerve
Sacral Plexus
L4-S4
- Butt, perineum, and lower limb
- Sciatic nerve
Coccygeal Plexus
S4-CO1
-small area of skin in coccygeal region
Dermatome
area of skin that provides sensory input to CNS via one pair of spinal nerves or the trigeminal nerve
4 types of somatic sensations
tactile, thermal, pain, and proprioceptive
Tactile sensations
touch, pressure, vibration, itch, tickle
-In skin: Meissner’s corpuscle, hair root plexus, Merkel Disc, Ruffini corpuscles, Pacinian corpuscles, and free nerve endings
mechanoreceptor thermoreceptor photoreceptor chemoreceptor nociceptor
- touch, pressure, vibration, and stretch
- temp
- light (retina)
- smell, taste, change in blood chem
- pain
Exteroreceptor
- stimuli outside body
- skin and most special sense organs
Interoreceptor
- visceroceptors
- internal stimuli from blood and viscera
- tissue stretch, temp, chem changes
- often unnoticed by person
prprioceptors
inform brain of one’s movements and body part location
Speed of sensory receptor adaptation
- Fast ones (phasic)= pressure, touch, smell, and temp –> send signals only at beginning and end of stimulus
- Slow (tonic) = pain, body position, of chem composition of blood
Pain
- warns of actual or impending tissue damage
- stimuli includes potassium, ATP, acids and bradykinin
- impulses travel up fibers that release glutamate and substance P
- Some pain is blocked by endogenous opiods (endorphis)
Visceral and Referred pain
Visceral = stimulation of visceral organ receptors –> vage aching, gnawing, burrowing –> activated by stretchig, ischemia, chems, muscle spasms
Referred = perceived as coming from somewhere else –> impulse travels along same nerve, so brain assumes stimulus is coming from common somatic region
Somatic Sensory Pathways
- First order neuron = somatic receptor to brain stem/ spinal cord
- Second order neuron = brain stem/ spinal cord to thalamus (decussate)
- Third order neuron = thalamus to primary somatosensory area of cortex
Posterior Column Medial Lemniscus Pathway
- senses touch, pressure, vibration, and proprioception from everything except face
- 1st neuron cell body in dorsal root ganglion –> travels up and synapses at either gracile or cuneate nucleus in medulla
- 2nd neuron decussates and synapses at thalamus
- 3rd neuron goes to primary somatosensory area
Anterolateral (spinothalamic) pathway
- senses pain, temp, itch, and tickle from everywhere except face
- 1st cell body in dorsal root ganglion –> snapses immediately in posterior grey horn
- 2nd neuron immediately decussates and travels up opposite column to thalamus
- 3rd neuron goes to primary somatosensory area
Trigeminothalamic Pathway
-somati sensation of face, oral cavity, nasal cavity, and teeth
-1st neuron body in trigeminal ganglion –> synapses in pons or medulla
-2nd neuron decussates and synapses in thalamus
03rd neuron goes to primary somatosensory region
Somatic Motor Pathways
- upper motor neurons to lower motor neurons to skeletal muscles
- neural circuits involving basal ganglia and cerebellum regulate upper motor neurons
Direct vs indirect motor neuron pathways
Direct
- originates in cerebral cortex
- corticospinal = to lmbs and trunk
- corticobulbar = to head
Indirect = originates in brainstem
Lateral Corticospinal pathway
- most of the motor stuff
- upper neuron in cerebral cortex –> crosses in pyramids –> lateral corticospinal tract –> anterior gray horn
- lower motor neuron goes out anterior root to innervate skeletal muscle
- distal limbs (forearms and hands)
Anterior Corticospinal Pathway
- upper motor neuron in cerebral cortex –> doesn’t cross at pyramids –> anterior corticospinal tract –> crosses and synapses at anterior gray horn
- lower neuron exits and innervates muscle
- trun kand posterior limbs
Corticobulbar pathway
- facial and hypoglossal nerves
- partially decussates –> upper right cranial nerve splits and innervates right and left facial nerve/hypoglossal nerve
- stroke/ bell’s palsy
