12 Central Nervous System (1)

Central Nervous System Overview

Chapter Outline

• Introduction to the CNS

• Regions of the Brain

• Functional Brain Systems

• Brain Disorders

• Spinal Cord Structure, Function, and Trauma

Major Regions of the Adult Brain:

• Cerebral Hemispheres

• Diencephalon

• Brain Stem

  -mid brain

  -pons

  -medulla oblongata

• Cerebellum

Ventricles of the Brain

• Spaces containing cerebrospinal fluid (CSF)

• Lined by ependymal cells to help circulate CSF

Cerebrum (not smooth)

Lobes of the Cerebral Cortex:

• Frontal Lobe: Voluntary movement

• Parietal Lobe: Sensory awareness

• Temporal Lobe: Auditory and olfactory processing

• Occipital Lobe: Visual processing

• Insula: Taste and balance

Characteristics:

• Gyri: Ridges on cerebral surface

• Sulci: Shallow grooves

• Fissures: Deep grooves

Major Sulci:

• Longitudinal Fissure: Separates hemispheres

• Transverse Cerebral Fissure: Separates cerebrum and cerebellum

• Central Sulcus: Separates frontal and parietal lobes

Functional Areas of the Cerebral Cortex:

• Motor Areas: Located in the frontal lobe (control voluntary movement)

• Sensory Areas: Found in parietal, insular, temporal, and occipital lobes (conscious awareness of sensation)

• Association Areas: Integrate information across different modalities (integrate diverse information)

• Multimodal Association Areas: Process and integrate multiple sensory inputs

visual - occipital

touch, temp, pressure- parietal

auditory- temporal

olfaction (smell)- temporal

gustation (taste)-insular

vestibular (balance)-insular

Lateralization of Function:

• Left Hemisphere: Language, math, logic

• Right Hemisphere: Visual-spatial skills, intuition, emotion, artistic skills

White Matter of the Cerebrum:

• Types of Fiber Tracts:

  • Commissural Fibers: Connect corresponding parts of different hemispheres

  • Association Fibers: Connect different parts within the same hemisphere

  • Projection Fibers: Connect cortical areas to lower parts of CNS

Basal Ganglia (Nuclei):

• Includes caudate nucleus, putamen, globus pallidus

• Filters inappropriate emotional and motor responses

Diencephalon consists of three paired structures

• Thalamus: Relay station for sensory input to the cerebral cortex

• Hypothalamus: Regulates homeostasis, connects to the pituitary gland

• Epithalamus (Pineal Gland): Secretes melatonin, regulates sleep-wake cycle

Brain Stem Structures and Functions:

• Midbrain: Relays sensory information, controls reflexes

• Pons: Relays impulses between motor cortex and cerebellum, regulates breathing

• Medulla Oblongata: Autonomic reflex centers for cardiovascular and respiratory functions

Cerebellum:

• Function: Coordinates movement, regulates posture and balance

• Arbor Vitae: Tree-like pattern of cerebellar white matter

Limbic System:

• Components: Structures in the diencephalon and some cerebral structures

• Functions: Emotions and memory (via hippocampus)

Reticular Formation:

• Function: Filters repetitive stimuli, regulates sleep and consciousness

Protection of the CNS:

• Meninges: Three protective layers - dura mater, arachnoid mater, and pia mater

• dura mater- Most superficial of the meninges • Limits excessive brain movement

• falx cerebri- Extension of dura mater into the longitudinal fissure • Attached to crista galli

• Tentorium cerebelli- Fold of the dura mater over the cerebellum • In the transverse fissure

• arachnoid mater- Intermediate layer of the meninges • Subarachnoid space contains CSF and large blood vessels • Arachnoid villi protrude into superior sagittal sinus and permit CSF reabsorption

• pia mater- Deepest of the meninges • Contains many small blood vessels • Clings tightly to brain
  
  

• Cerebrospinal Fluid (CSF): Cushions the brain and maintains chemical stability

  formation and circulation of CSF:

  
  1. Produced by choroid plexus of each ventricle

  2. Flows through ventricles into subarachnoid space

  3. Flows through subarachnoid space

  4. Absorbed into dural venous sinuses

• Choroid plexuses

• Hang from roof of each ventricle

• • Clusters of capillaries

• • Lined with ependymal cells

• • Produce and circulate CSF •

• CSF is replaced every 8 hrs.
  
  

• Blood-Brain Barrier: Protects CNS from pathogens and toxins, regulates substance transport

Traumatic Brain Injuries (TBI):

• Types:

  • Concussion: Temporary alteration in brain function

  • Contusion: Permanent damage due to bruising

  • Cerebral Edema: Swelling of the brain, potentially fatal

Alzheimer’s Disease:

• Characterized by: Dementia and emotional changes

• Associated with:

  • Amyloid plaques

  • Neurofibrillary tangles leading to neuron death

• Symptoms: Decreased neural activity, especially in parietal lobes

Spinal Cord Structure and Function:

• Communication: Two-way communication between brain and body

• Components: Cervical and lumbosacral enlargements, cauda equina
  Cauda equina • Collection of nerve roots at inferior end of vertebral canal

  Cervical and lumbosacral enlargements • Nerves that serve upper and lower limbs
  Spinal nerves • Part of the peripheral nervous system (PNS) • 31 pairs of spinal nerves

• Function: Reflex centers; protected by bone, meninges, and CSF

• Gray Matter: Divided into horns for sensory and motor functions

• White Matter: Ascending and descending tracts for brain communication

Spinal Cord Injury:

• Paraplegia: Loss of motion/sensation in lower limbs

• Quadriplegia: Loss in both upper and lower limbs

• transection: Complete severing of the spinal cord, resulting in total loss of function below the level of injury.

Developmental Aspects:

• CNS Development: Influenced by maternal factors; hypoxia can lead to neuron death.

• Aging: Cognitive declines noted, but significant issues generally do not arise until the 80s.