The human nervous system. Sky blue is PNS; yellow is CNS.
Schematic diagram showing the central nervous system in yellow, peripheral in orange
The formation of the spinal nerve from the posterior and anterior roots
3D Medical Animation still shot of Lumbosacral Plexus
Dissection of a human brain with labels showing the clear division between white and gray matter.
Spinal nerve
Diagram of the columns and of the course of the fibers in the spinal cord. Sensory synapses occur in the dorsal spinal cord (above in this image), and motor nerves leave through the ventral (as well as lateral) horns of the spinal cord as seen below in the image.
Typical spinal nerve location
Different ways in which the CNS can be activated without engaging the cortex, and making us aware of the actions. The above example shows the process in which the pupil dilates during dim light, activating neurons in the spinal cord. The second example shows the constriction of the pupil as a result of the activation of the Eddinger-Westphal nucleus (a cerebral ganglion).
Scheme showing structure of a typical spinal nerve
1. Somatic efferent.
2. Somatic afferent.
3,4,5. Sympathetic efferent.
6,7. Autonomic afferent.
A map over the different structures of the nervous systems in the body, showing the CNS, PNS, autonomic nervous system, and enteric nervous system.
Cervical nerves
Schematic image showing the locations of a few tracts of the spinal cord.
Lumbar plexus and branches
Reflexes may also occur without engaging more than one neuron of the CNS as in the below example of a short reflex.
Plan of sacral and pudendal plexuses
Diagram depicting the main subdivisions of the embryonic vertebrate brain, later forming forebrain, midbrain and hindbrain.
Areas of distribution of the cutaneous branches of the posterior divisions of the spinal nerves. The areas of the medial branches are in black, those of the lateral in red
Development of the neural tube
A portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots.
Distribution of the cutaneous nerves. Ventral aspect.
Distribution of the cutaneous nerves. Dorsal aspect.
The spinal cord with dura cut open, showing the exits of the spinal nerves.
The spinal cord showing how the anterior and posterior roots join in the spinal nerves.
A longer view of the spinal cord.
Projections of the spinal cord into the nerves (red motor, blue sensory).
Projections of the spinal cord into the nerves (red motor, blue sensory).
Schematic diagram of cervical plexus.
Cerebrum. Inferior view. Deep dissection.
Cerebrum. Inferior view. Deep dissection.
Spinal nerves. Spinal cord and vertebral canal. Deep dissection.

The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS).

- Peripheral nervous system

The spinal nerves are part of the peripheral nervous system.

- Spinal nerve

Microscopically, there are differences between the neurons and tissue of the CNS and the peripheral nervous system (PNS).

- Central nervous system

For the rest of the body, spinal nerves are responsible for somatosensory information.

- Peripheral nervous system

From and to the spinal cord are projections of the peripheral nervous system in the form of spinal nerves (sometimes segmental nerves ).

- Central nervous system

These pathways have both afferent and efferent fibers and, this way, they are responsible for conduction of sensory information from these pelvic organs to the central nervous system (CNS) and motor impulses from the CNS to the pelvis that control the movements of these pelvic organs.

- Spinal nerve
The human nervous system. Sky blue is PNS; yellow is CNS.

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Overall

The spinal cord (in yellow) connects the brain to nerves throughout the body.

Spinal cord

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Long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column .

Long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column .

The spinal cord (in yellow) connects the brain to nerves throughout the body.
Part of human spinal cord. 1 – central canal; 2 – posterior median sulcus; 3 – gray matter; 4 – white matter; 5 – dorsal root + dorsal root ganglion; 6 – ventral root; 7 – fascicles; 8 – anterior spinal artery; 9 – arachnoid mater; 10 – dura mater
Diagram of the spinal cord showing segments
A model of segments of the human spine and spinal cord, nerve roots can be seen extending laterally from the (not visible) spinal cord.
Spinal cord seen in a midsection of a five-week-old embryo
Spinal cord seen in a midsection of a 3 month old fetus
Spinal cord tracts.
Spinal Cord Sectional Anatomy. Animation in the reference.
Diagrams of the spinal cord.
Cross-section through the spinal cord at the mid-thoracic level.
Cross-sections of the spinal cord at varying levels.
Cervical vertebra
A portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots.
The spinal cord with dura cut open, showing the exits of the spinal nerves.
The spinal cord showing how the anterior and posterior roots join in the spinal nerves.
The spinal cord showing how the anterior and posterior roots join in the spinal nerves.
A longer view of the spinal cord.
Projections of the spinal cord into the nerves (red motor, blue sensory).
Projections of the spinal cord into the nerves (red motor, blue sensory).
Cross-section of rabbit spinal cord.
Cross section of adult rat spinal cord stained using Cajal method.
An overview of the spinal cord.
Sagittal section of pig vertebrae showing a section of the spinal cord.
The base of the brain and the top of the spinal cord
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Cerebrum.Inferior view.Deep dissection
Cerebrum.Inferior view.Deep dissection
Spinal cord. Brachial plexus. Cerebrum.Inferior view.Deep dissection.
Spinal cord. Brachial plexus. Cerebrum.Inferior view.Deep dissection.
Spinal cord
Medulla spinalis of 8-week-old human embryo

The brain and spinal cord together make up the central nervous system (CNS).

Human spinal cord svg.svg spinal cord is the main pathway for information connecting the brain and peripheral nervous system. Much shorter than its protecting spinal column, the human spinal cord originates in the brainstem, passes through the foramen magnum, and continues through to the conus medullaris near the second lumbar vertebra before terminating in a fibrous extension known as the filum terminale.

The nerve roots then merge into bilaterally symmetrical pairs of spinal nerves.

The human vertebral column and its regions

Vertebral column

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Part of the axial skeleton.

Part of the axial skeleton.

The human vertebral column and its regions
Numbering order of the vertebrae of the human spinal column
Anatomy of a vertebra
A thoracic spine X-ray of a 57-year-old male.
Lateral lumbar X-ray of a 34-year-old male
The spinal cord nested in the vertebral column.
3D Medical Animation still shot of Spina Bifida
Diagram showing normal curvature of the vertebrae from childhood to teenage
Surface projections of organs of the torso. The transpyloric line is seen at L1
A vertebra (diameter 5 mm) of a small ray-finned fish

The spinal nerves leave the spinal cord through these holes.

The spinal cord is part of the central nervous system that supplies nerves and receives information from the peripheral nervous system within the body.

Nerves (yellow) in the arm

Nerve

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Nerves (yellow) in the arm
Cross-section of a nerve
Micrograph demonstrating perineural invasion of prostate cancer. H&E stain.

A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.

A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system.

Nerve cells (often called neurons) are further classified as sensory, motor, or mixed nerves.