The Limbic System

1
The Limbic System

• Encircle the upper part of the brain stem.
• Is the main emotional or feelings part of the
  brain.
• Links sensory input to emotions (ex. Recognizing
  angry facial expressions or bad smells followed
  by a physical response).

2
Protection of the Brain

• Bone-
• Done by the skull and the vertebrae.
• Meninges-
• Provides four functions
• 1. Covers and protects the CNS.
• 2. Protects blood vessels.
• 3. Contains cerebralspinal fluid.
• 4. Form partitions in the skull.

3
There are three types of meninges

• 1. Dura Mater-
• Is the strongest of the meninges.
• Made of two layers of fibrous connective tissues.
• It is the most superficial layer.
• Only found in the skull.
• Limits excessive movement of the brain.
• 2. Arachnoid Mater-
• Made of fine elastic connective tissue.
• Is the middle layer of the meninges.
• Subarachnoid space contains cerebralspinal fluid
  and large blood vessels.
• Provides minimal protection.
• 3. Pia Mater-
• Made of delicate connective tissue.
• Full of tiny blood vessels.
• Clings tightly to the brain.
• Full of tiny blood vessels.
• Clings tightly to the brain.

4
Cerebralspinal Fluid

• Found in and around brain and spinal cord.
• Forms a liquid cushion for CNS.
• Helps nourish the brain.
• May carry chemical signals through CNS.
• Similar in composition as blood plasma.
• Volume is 150ml and is replaced about every 8
  hours.
• CSF is filtered from blood from the choroid
  plexures of each of the CNS ventricles.

5
Blood-Brain Barrier

• Capillaries of the CNS are selectively permeable
  to prevent variations in hormones, ions, amino
  acids, etc.
• The hypothalamus has a reduced blood-brain
  barrier so that it can sample and react to the
  activity going on in the body.

6
The Spinal Cord

• Starts at the base of the skull and extends down
  to the first or second lumbar vertebra.
• Provides a two-way conduction pathway.
• Protected by bone, meninges, and cerebralspinal
  fluid.
• Has 31 pairs of spinal nerves.
• Important terms associated with the spinal cord
• 1. Conus Medullaris- inferior cone-shaped end of
  the spinal cord.
• 2. Cervical Lumbar Enlargements- areas that
  supply nerves to limbs.
• 3. Filum Terminale- extension of the pia mater
  that anchors the inferior end of the spinal cord
  to the coccyx.

7
Cross-Section Anatomy of the Spinal Cord

• Gray matter is found in the core of the cord.
• Shaped like the letter H
• Posterior Horn (sensory)- receives impulses from
  sensory receptors from dorsal roots and dorsal
  root ganglia.
• Anterior Horn (motor)- sends axons out to
  effector cells via ventral roots.
• Lateral Horn- found in thoracic and lumbar areas
  of cord. Sends axons out to visceral organs
  (autonomic).
• Gray Commissure- connects the two sides of the
  horn.

8
Cross-Section Anatomy of the Spinal Cord (cont.)

• Dorsal and Ventral Roots fuse to form spinal
  nerves.
• Gray matter of spinal cord can be divided into 4
  zones
• 1. Somatic Sensory
• 2. Visceral Sensory
• 3. Somatic Motor
• 4. Visceral Motor

9
The Peripheral Nervous System

• Is the link between the CNS and the outside
  world.
• Includes all neural structures outside of the
  brain and spinal cord
• A. Sensory Receptors- responds to changes in the
  environment.
• Are modified dendritic endings.
• B. Nerves- consist of parallel bundles of
  peripheral axons enclosed by connective tissue.

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• Nerves (cont.)-
• Axons are surrounded by endoneurium (loose
  connective tissue).
• Bundles of these (fascicles) are wrapped with the
  perineurium (coarser connective tissue).
• All the fascicles are enclosed by the epineurium
  (a tough fibrous sheath).
• Myelin, connective tissue, blood vessels, and
  lymphatic vessels are also part of the nerve
  fibers.
• There are 3 types of nerves
• Sensory- carry impulses to the CNS.
• Motor- carry impulses away from the CNS.
• Mixed- contained both types (most common types)