Internal anatomy of the spinal cord and functions of gray and white matter
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152 Terms
Where is the anterior (ventral) median fissure located?
On the anterior midline of the spinal cord
What is the main function of the anterior median fissure?
Separates the left and right halves of the spinal cord
Where is the posterior (dorsal) median sulcus located?
On the posterior midline of the spinal cord
What is the main function of the posterior median sulcus?
Helps divide the spinal cord into left and right sides
Where is gray matter located in the spinal cord?
In the central, butterfly‑shaped region
What is the main function of gray matter?
Contains neuron cell bodies for processing and integrating information
Where is white matter located in the spinal cord?
Surrounding the gray matter
What is the main function of white matter?
Contains myelinated axons that conduct signals up and down the spinal cord
Where is the central canal located?
In the centre of the gray matter
What is the main function of the central canal?
Contains cerebrospinal fluid for nutrient transport and cushioning
Where does gray matter vary in size?
Across cervical, thoracic, lumbar, and sacral regions
What is the functional significance of this variation?
Reflects differing numbers of neurons needed to supply each body region
Where are the cervical spinal cord segments located?
In the upper spinal cord region
What is the function of cervical gray matter?
Supports innervation of upper limbs and diaphragm
Where are the thoracic spinal cord segments located?
In the mid‑spinal region
What is the function of thoracic gray matter?
Supports trunk and autonomic functions
Where are the lumbar spinal cord segments located?
In the lower spinal cord region
What is the function of lumbar gray matter?
Supports lower limb innervation
Where are the sacral spinal cord segments located?
In the lowest spinal cord region
What is the function of sacral gray matter?
Supports pelvic organ and lower limb innervation
Where is the gray commissure located?
In the central region of the spinal cord surrounding the central canal
What is the main function of the gray commissure?
Allows axons to cross from one side of the CNS to the other
Where is the central canal located?
At the centre of the gray commissure
What is the main function of the central canal?
Contains cerebrospinal fluid for cushioning and nutrient transport
Where are the posterior (dorsal) gray horns located?
Posterior region of the spinal cord gray matter
What is the main function of the posterior gray horns?
Contain sensory nuclei that receive incoming sensory information
Where are the anterior (ventral) gray horns located?
Anterior region of the spinal cord gray matter
What is the main function of the anterior gray horns?
Contain somatic motor nuclei that control skeletal muscles
Where are the lateral gray horns located?
Lateral region of gray matter in thoracic and upper lumbar segments
What is the main function of the lateral gray horns?
Contain autonomic motor nuclei for involuntary control of smooth muscle, cardiac muscle, and glands
Where are sensory nuclei located in the spinal cord?
Within the posterior gray horns
What is the function of sensory nuclei?
Process incoming sensory information from peripheral receptors
Where are somatic motor nuclei located?
In the anterior gray horns
What is the function of somatic motor nuclei?
Control voluntary skeletal muscle activity
Where are autonomic motor nuclei located?
In the lateral gray horns
What is the function of autonomic motor nuclei?
Regulate involuntary functions of organs and glands
Where are the sensory nuclei located?
In the posterior (dorsal) gray horns
What is the main function of the sensory nuclei?
Receive and process incoming sensory input from peripheral receptors
Where do sensory neuron axons enter the spinal cord?
Through the dorsal root
What is the function of the dorsal root in sensory pathways?
Transmits sensory information into the CNS
Where is the dorsal root ganglion located?
On the dorsal root just before it enters the spinal cord
What is the main function of the dorsal root ganglion?
Contains the cell bodies of sensory neurons
Where are the somatic motor nuclei located?
In the anterior (ventral) gray horns
What is the main function of the somatic motor nuclei?
Contain lower motor neuron cell bodies that control skeletal muscles
Where do lower motor neuron axons exit the spinal cord?
Through the ventral root
What is the function of the ventral root in somatic pathways?
Transmits voluntary motor commands to skeletal muscles
Where are the autonomic motor nuclei located?
In the lateral gray horns (thoracic and upper lumbar segments)
What is the main function of the autonomic motor nuclei?
Contain preganglionic neuron cell bodies for involuntary control of smooth muscle, cardiac muscle, and glands
Where do preganglionic autonomic axons exit the spinal cord?
Through the ventral root
What is the function of these autonomic axons?
Carry outgoing autonomic motor signals to peripheral ganglia
Where are spinal reflexes integrated?
In the gray matter of the spinal cord
What is the main function of spinal reflex integration?
Receive sensory input, interpret it, and generate rapid motor output
Where does a reflex arc begin?
At a sensory receptor
What is the function of the receptor in a reflex arc?
Detects a stimulus and initiates the reflex
Where does sensory information travel in a reflex arc?
Along a sensory neuron into the spinal cord
What is the function of the sensory neuron?
Transmits the stimulus to the integration centre
Where is the integration centre located?
Within the gray matter of the spinal cord
What is the function of the integration centre?
Processes sensory input and determines the motor response
Where does motor output leave in a reflex arc?
Through a motor neuron
What is the function of the motor neuron?
Delivers the reflex command to an effector
Where is the effector located?
In skeletal muscle, smooth muscle, or glands
What is the function of the effector?
Produces the reflex response
Where are somatic reflexes integrated?
In the spinal cord gray matter
What is the function of somatic reflexes?
Produce involuntary skeletal muscle contractions (e.g., patellar reflex)
Where are autonomic reflexes integrated?
In the spinal cord gray matter
What is the function of autonomic reflexes?
Produce involuntary responses in smooth muscle, cardiac muscle, or glands
Where is white matter located in the spinal cord?
Superficial to the gray matter
What is the main function of white matter?
Conducts ascending sensory and descending motor signals
Where is the anterior white commissure located?
At the front of the spinal cord between the white columns
What is the function of the anterior white commissure?
Allows axons to cross from one side of the CNS to the other
Where are the white columns located?
In the posterior, lateral, and anterior regions of the spinal cord
What is the function of the white columns?
Organise axon tracts that carry information up and down the spinal cord
Where are ascending tracts located?
In the white matter columns of the spinal cord
What is the main function of ascending tracts?
Conduct sensory input from the body to the brain
Where are descending tracts located?
In the white matter columns of the spinal cord
What is the main function of descending tracts?
Conduct motor output from the brain to the body
Where are the posterior white columns located?
Posterior region of the spinal cord white matter
What is their main function?
Carry fine touch, vibration, light pressure, and proprioception
Where are the lateral white columns located?
On the lateral sides of the spinal cord white matter
What is their main function?
Carry pain, temperature, proprioception, and some motor pathways
Where are the anterior white columns located?
Anterior region of the spinal cord white matter
What is their main function?
Carry crude touch, deep pressure, and some motor pathways
Where is the anterior white commissure located?
At the front of the spinal cord between the anterior white columns
What is its main function?
Allows axons to cross from one side of the CNS to the other
Where is the fasciculus gracilis located?
In the posterior white columns
What sensory information does the fasciculus gracilis conduct?
Fine touch, vibration, light pressure, proprioception from lower body
Where is the fasciculus cuneatus located?
In the posterior white columns
What sensory information does the fasciculus cuneatus conduct?
Fine touch, vibration, light pressure, proprioception from upper body
Where is the lateral spinothalamic tract located?
In the lateral white columns
What sensory information does the lateral spinothalamic tract conduct?
Pain and temperature
Where is the anterior spinothalamic tract located?
In the anterior white columns
What sensory information does the anterior spinothalamic tract conduct?
Crude touch and deep pressure
Where is the anterior spinocerebellar tract located?
In the lateral white columns
What sensory information does the anterior spinocerebellar tract conduct?
Proprioception to the cerebellum
Where is the posterior spinocerebellar tract located?
In the lateral white columns
What sensory information does the posterior spinocerebellar tract conduct?
Proprioception to the cerebellum
Where are descending tracts located?
In the white matter columns of the spinal cord
What is the main function of descending tracts?
Conduct motor output from the brain to skeletal muscles
Where is the lateral corticospinal tract located?
In the lateral white columns
What motor output does the lateral corticospinal tract conduct?
Somatic motor control of limb muscles