Central nervous system

The Brain

There are four major regions of the brain.  

  • Cerebrum (rest of brain, largest area)

The cerebrum includes motor areas, sensory areas, and association areas.

Functions: higher thoughts, initiating skeletal muscle movements, sensations, complex processing

The cerebrum is divided into the left and right hemispheres along the longitudinal fissure.

Gyri and sulci (raised ridges and troughs) increase the surface area of the cerebrum.


  • Diencephalon (center)

The diencephalon is the most superior portion of the brainstem, divided into the thalamus, hypothalamus, and epithalamus.

Functions: processing centers, relay station, regulating autonomic function via hormones


  • Brainstem (midbrain, pons, medulla oblangata)

The brainstem contains the midbrain, pons, and medulla oblongata.

Functions: cranial nerve nuclei, autonomic functions like respiratory & heart rate


  • Cerebellum (little brain in the back)

Functions: fine motor coordination, balance


Thalamus: Relays sensory information to the appropriate sensory cortex


epithalamus & pineal gland: Regulates day/night cycles via pineal gland (melatonin) and makes CSF


Hypothalamus

Controls body temperature & other homeostatic mechanisms via the pituitary gland


Midbrain

Creates dopamine in substantia nigra


Pons

  • Respiration

  • Nuclei of cranial nerves


Medulla oblongata

  • Respiratory rate 

  • Cardiac function


Conus medullaris

Latin for the medullary cone. This structure is the inferior tapered end of the spinal cord. It is generally found at the L1-L2 region.

  • Nerves branching out of this structure to innervate lower regions form the cauda equina

  • Damage to the medullary cone can cause hyperreflexia, back pain, bowel and bladder dysfunction, sexual dysfunction, loss of sensation, and weakness in the legs.


Conus medullaris

Latin for the medullary cone. This structure is the inferior tapered end of the spinal cord. It is generally found at the L1-L2 region.

  • Nerves branching out of this structure to innervate lower regions form the cauda equina

  • Damage to the medullary cone can cause hyperreflexia, back pain, bowel and bladder dysfunction, sexual dysfunction, loss of sensation, and weakness in the legs.


Filum terminale

This extension of the pia mater connects the spinal cord to the coccyx (tailbone), stabilizing the spinal cord.


White matter consists of axons and oligodendrocytes, while the gray matter consists of neurons and unmyelinated fibers. 

white matter has acsending and descending tracks

Gray matter includes dorsal horns and carries sensory in and out of spinal cord


Ventral root: motor information,

Dorsal root: Afferent signals, sensory information, includes ganglion


In the brain:  

  • The white matter is deep. 

  • Gray matter is superficial. 

    • Gray matter makes up the cerebral cortex. 

In the spinal cord:

  • The white matter is superficial.

  • Gray matter is deep.



The meninges form the protective covering of the brain and spinal cord. It is comprised of three layers:

  • dura mater;

  • arachnoid mater; and

  • pia mater.


The spaces between these layers include:

  • epidural space: The space between the dura materand the skull

  • subdural space: The space between the dura materand the arachnoid mater

  • subarachnoid space: The space between the arachnoid mater and the pia mater


Cerebrospinal fluid circulates through the:

  • Ventricles, or open spaces within the brain

  • Subarachnoid space

  • Central canal of spinal cord