spinal cord pathways

pathway

series of neurons that relay signals between the brain and part of the body

tracts

components within the brain, the cord, and individual neurons within spinal nerves

decussate

to cross over to the other side of the brain

Contralateral

crosses over to opposite side

Ipsilateral

same side

what are the types of conduction pathways

sensory pathway

motor pathways

sensory pathways

2 or 3 neurons are used to relay the signal from receptors to the brain

general sense receptors

primary, secondary, or tertiary neurons

motor pathways

2 or more somatic motor neurons are used to relay the signal from the brain to the effectors

neurons are either upper or lower

direct- 1 upper and lower

indirect- many upper and 1 lower

what are the types of neuron pathways in the sensory pathways

posterior columns pathway (somatosensory)

spinothalamic pathway (somatosensory)

spinocerebellar pathway

posterior columns pathway

receives information from skin(proprioceptive) and within joints(tactile)

what are the different neurons and functions in posterior columns pathway

1st order- signal from somatosensory receptors--> brainstem

2nd order--> medulla oblongata-->thalamus

---> always decussates in the medulla

3rd order-- thalamus--> primary somatosensory cortex

--> conscious perception of input here

anterolateral pathway

crude sensations of touch and pressure

pain and temperature

what are the different neurons and function in anterolateral pathway

1st order--> receptors in skin--> spinal cord posterior horn

2nd order--> thalamus (lateral or anterior spinothalamic)

---> decussates in cord gray matter

3rd order neuron--> thalamus--> somatosensory cortex

spinocerebellar pathway

Carries proprioceptive information to the cerebellum

subconscious postural info to maintain balance and posture

what are the neurons in the spinocerebellar pathway

1st order--> proprioceptors--> posterior horn of spinal cord

2nd order--> posterior horn of spinal cord--> cerebellum

---> some 2nd order are contralateral and some are ipsilateral

what is the differences between the spinocerebellar pathway and the other pathways?

2nd order goes to the cerebellum not thalamus

no 3rd order neuron

some fibers decussates

somatic motor tracts

CNS transmits motor commands in response to sensory info, descending tracts

motor commands are delivered by

direct pathways (conscious)

indirect pathways (subconscious)

direct pathways

two neuron path between brain and skeletal muscle

conscious control of skeletal muscle

indirect pathways

more than two neuron pathways and skeletal muscle; multiple upper neurons

neurons take a complicated route to spinal cord

subconscious skeletal muscle activity (relfexive)

what are the different types of somatic motor pathways: direct pathways

corticospinal pathway

corticospinal pathway

lateral corticospinal tract

anterior corticospinal tract

lateral corticospinal pathway

upper neuron- primary motor cortex--> anterior horn of cord

---> decussates in medulla oblongata

lower neuron- anterior horn--> skeletal muscle

anterior corticospinal pathway

upper neuron- primary motor cortex--> anterior horn of cord

--> decussates in anterior white commissure of cord

lower neuron- anterior horm--> skeletal muscle via anterior root

posterior roots

contain sensory neurons; posterior root ganglion contains cell bodies of those neurons

anterior roots

motor neurons

nerve plexus

network of interweaving anterior rami of spinal nerves

occur bilaterally, then split into multiple names nerves

what are the types of nerve plexus

cervical plexus

brachial plexus

lumbar plexus

sacral plexus

thoracic anterior rami

motor to intercostal muscles, abdominal muscles

sensory

what are the major branches of brachial plexus sensory areas

axillary nerve, median nerve, musculcutaneous nerve, radial nervem ulnar nerve

major branches of lumbar plexus

femoral nerve(motor)

obturator nerve (motor)

sacral plexus

sciatic nerve

---> does not split until knee but distinct regions above knee

what are the major divisions of the sciatic nerve

tibial divison

common fibular nerve

deep fibular nerve

superficial fibular nerve

dermatomes

segments of skin supplied by a single spinal nerve

some overlap in innervated region

can help localize damage to one or more spinal nerves

involved in referred visceral pain