Basic features of the nervous system

Sagittal Plane:  

 Slicing the brain parallel to the neuraxis and perpendicular to the ground

Coronal plane

 Slicing the brain parallel to the forehead to make front and back sections.

Horizontal plane

Slicing the brain parallel to the ground, to make top and bottom sections.

Neuroaxis

imaginary line drawn through the central nervous system from the spinal cord to the front of the brain.

Rosita and caudal

Rostral is towards the face and caudal is away from the face. These terms are mostly used to describe the brain.

Anterior posterior

Following the neuraxis, anterior is towards the front and posterior is towards the back.

Dorsal ventral

Relative to the neuraxis, dorsal is toward the back and ventral is toward the belly.

Lateral, medial

Lateral is towards the side of the body whereas medial is towards the middle of the body.

Ipsilateral Contralateral

Ipsilateral refers to structures located on the same side of the body. Contralateral refers to structures on the opposite sides of the body.

Meninges

• Definition: Meninges are protective membranes encasing the central nervous system (CNS) and parts of the peripheral nervous system (PNS).

• Main Functions: Provide structure and support to the nervous system.

 

Meninges = Layers of connective tissue covering nervous

system to provide structure and protection

 

3 layers of meninges in the central nervous system:

• Dura mater

• Arachnoid membrane

• Pia mater

 

• The peripheral nervous system only has the dura and pia mater layers which are fused together and cover nerves (forming a protective sheath)

 

Dura mater

• Forms the outer layer of meninges

• Durable, Thick, tough, and flexible

• Dura= Durable

Arachnoid Membrane

• Forms the middle layer

• Soft and spongy

• Beneath dura mater

Pia mater

• Shaped to the brains surface

• Thin and delicate

subarachnoid space.

• In between the arachnoid
  membrane and the pia mater is the subarachnoid space.

 

• It is is filled with Cerebrospinal
  Fluid (CSF)
  produced by the ventricular system

Ventricular System and Cerebrospinal Fluid

cerebrospinal fluid (CSF) A clear fluid, similar to blood plasma, that fills the ventricular system of the brain and the subarachnoid space surrounding the brain and spinal cord.

 

Cerebrospinal Fluid

 two main jobs:

1. Shock absorber - CSF allows the brain to float,  reducing its  net weight and protecting it during impacts, such as hitting the head.

2. Material exchanger - helps provide nutrients to the brain and remove waste

 

Ventricular System

• Ventricles are small, hollow interconnected  spaces / chambers in the brain

• The ventricles are connected to one another and produce, store and circulate the cerebrospinal fluid

 

Choroid Plexus:

•  is made from a highly vascular tissue called the choroid plexus found in all the ventricles.

 

Choroid Plexus:

• Vascular tissue that extends into the ventricles.

• Primary role is to produce cerebrospinal fluid.

• 👉 “Choroid = CSF factory”

 

• After production, CSF is transported from the lateral ventricles onwards, and released into subarachnoid space

 

• Flow of CSF:

  • CSF is first produced in:

  • Lateral Ventricles (contains choroid plexus)

  • Then flows to:

  • Third Ventricle (more CSF produced)

  • Fourth Ventricle (additional CSF production)

  • Finally released into the subarachnoid space.

 

• Flow of CSF:

• CSF Flow (step-by-step)

  1. CSF is made in lateral ventricles

  2. Flows to third ventricle

  3. Goes through cerebral aqueduct

  4. Enters fourth ventricle

  5. Leaves into subarachnoid space (around brain & spinal cord)

  6. Gets reabsorbed into blood via arachnoid granulations

Absorption of CSF

• CSF eventually reabsorbed into the blood supply through:

  • Arachnoid Granulations:

  • Sections within the ventricular system facilitating the reabsorption process.

• arachnoid granulation Small projections of the arachnoid membrane through the dura mater into the superior sagittal sinus; CSF flows through them to be reabsorbed into the blood supply.