Chapter 14: Spinal Cord & Spinal Nerves

what is the difference for adults in the length of vertebrae

the spinal cord is shorter than the vertebral canal

what are the 5 spinal cord subdivisions?

cervical (8), thoracic (12), lumbar (5), sacral (5), coccygeal (1)

what are two important features of the spinal cord? hint: it is in between the butterfly shapes at both ends

• posterior median sulcus

• anterior median fissure

what are the spinal cord meninges

vertebra - epidural space, dura mater

subdural space, arachnoid mater, subarachnoid mater, pia mater

sensory pathways …

ascend up to the brain from the sensory receptors, they are afferent

motor pathway…

descend from brain to the muscles or glands (the effectors), these are efferent

what does it mean to decussate?

to cross over from one side of the nervous system to the other, there are contralateral (different) pathways and ipsilateral (same side) pathways.

where is the primary neuron and what does it do?

The primary neuron is located in the sensory ganglia and it is responsible for transmitting sensory information from the periphery to the central nervous system.

where is the secondary neuron and what does it do?

The secondary neuron is typically located in the spinal cord or brainstem and it relays sensory information from the primary neuron to the thalamus or other brain regions for further processing.

where is the tertiary neuron do and where is it located?

The tertiary neuron is located in the thalamus and it transmits sensory information from the secondary neuron to the appropriate cortical areas for perception.

what kind of neurons do motor pathways have?

upper and lower

what are the upper motor neurons and what do they do

Upper motor neurons are located in the brain and are responsible for conveying impulses to lower motor neurons in the spinal cord to initiate voluntary movement. They excite or inhibit lower motor neurons

what are the lower motor neurons and what do they do?

Lower motor neurons are located in the spinal cord and directly innervate skeletal muscles, facilitating voluntary movements by transmitting impulses from upper motor neurons. They are always excitatory.

what are direct pathways responsible for?

Direct pathways are responsible for producing voluntary/conscious muscle movements by transmitting signals from the cerebral cortex directly to lower motor neurons.

what do indirect pathways do?

Indirect pathways are responsible for regulating automatic/subconscious movements and modulating muscle tone by routing signals through various brainstem nuclei and spinal cord interneurons before reaching lower motor neurons.