The CNS

The cpu of the body

Composed of three regions

·  The Meninges

·  The Spinal Cord

·  The Brain

The Meninges

·  These are the layered membranes that surround the spinal cord and the brain

·  They lie between the boney coverings and the nerves

◦  The spine

◦  The skull

·  There are three layers

·  CFS (cerebrospinal fluid) between the 2 innermost layer

◦  Clear and watery

Meninx # 1 the Dura Mater

·  Dura Mater

◦  Outer most layer

◦  Mostly tough white fiberous connective tissue

◦  Many blood vessels and nerves

◦  Makes a strong tubular sheath that surrounds the spinal cord

◦  Attaches to the skull but not to the spine

Meninx # 2 the Arachnoid mater

·  Thin web-like without blood vessels

·  Spreads across the brain and the spinal chord with out dipping into grooves

The meninx #3 Pia Mater

·  Very thin

·  Lots of nerves and blood vessels

·  Nourishes the brain and spinal chord

·  Snug against the brain and spinal chord

The spinal chord

·  A slender nerve column that passes downward from the brain into the vertebral canal

·  Starts are the foramen magnum and stops at the intervertabral disc the separates the first and second lumbar vertebrae

·  Thirty one segments that give rise to pairs of spinal nerves

The sections of the spinal chord

·  Cervical enlargement – in the neck region – nerves to the upper limbs

·  Lumbar enlargement – in the lower back – nerves to the lower limbs

·  Anterior median fissure and posterior median sulcus - extends the length of the spinal chord (the dip in the front and back)

◦  Divides into right and left side

Sections continued

·  The horns:

◦  Dorsal

◦  Anterior

◦  Lateral

·  Grey matter – the unmyelinated area in the center of the chord

·  White matter – the outside area of the chord

  • Grey commissure – enclosed a central canal which provides nourishment to the spinal cord, connects the 2 sides of the grey matter

The Brain

  • Divided into 4 major regions

◦  Cerebrum – largest, sensory motor functions, and higher mental functions

  • Diencephalon – sensory information
  • Brainstem -connects parts and regulate visceral activites

·  Cerebellum – coordinates voluntary muscular movement.

Cerebrum

  • Two hemispheres – Right and Left

◦  Corpus callosum – nerve fibers that bridge the two hemispheres

  • Surface features

◦  Gyri(us)/convolutions – ridges

◦  Grooves

▪  Sulci (us) – shallow – separates lobes

▪  Fissure – deep - divide brain into hemispheres

  • Cerebral cortex

◦  outermost portion, thin layer coves the gyri and sulci and fissures; 75% neuron cell bodies in the nervous system

Functions of the Cerebrum

  • Specific regions do specific functions

◦  Motor areas – just anterior to the central sulcus – axons criss-cross sides in the brainstem

▪  Broca’s area – motor speech – coordinates mouth, tongue, and larynx muscles

▪  Frontal eye field -voluntary movement of eyes and lids

◦  Sensory areas – scattered about dependent on type, axon criss-cross

▪  Visual in posterior occipital lobe

▪  Cutaneous senses – anterior portion of parietal lobe

▪  Auditory area in temporal lobe

Association Areas

  • Neither primary sensory nor motor area
  • Connected together and with other brain areas

◦  Frontal lobe – higher thinking

◦  Parietal lobe -understanding speech and word choice

◦  Temporal lobe – interpret sensory experiences- used to understand reading and speech

◦  Occipital lobe – visual patterns, combining vision with other senses

◦  General interpretative area – complex thought processing – where all above meet

Ventricles and Cerebrospinal Fluid

  • Ventricles – interconnected cavities in the cerebral hemispheres and the brain stem

◦  Continuous with the central canal of the spinal cord, has cerebrospinal fluid.

◦  Lateral ventricles - 1st and 2nd ventricles

▪  Inside both frontal, temporal, and occipital lobes

◦  3rd ventricle in midline of brain beneath Corpus callosum

◦  4th ventricle – in brainstem anterior to the cerebellum

  • Cerebrospinal fluid – made by choroid plexuses projected into the ventricles

Diencephalon

  • Between the hemispheres and above the midbrain, surrounded by the 3rd ventricle
  • Structures within

◦  Thalamus – major sensory relay station

◦  Hypothalamus -maintains homeostasis

▪  Heart rate/arterial pressure

▪  Body temp

▪  Water and electrolyte balance

▪  Hunger/body weight

▪  Movement and glandular secretions of stomach and intestines

▪  Sleep and wakefulness

▪  Stimulates the pituitary gland

Diencephalon con’t

  • Other parts

◦  Optic tracts and optic chiasma (where optic nerve fibers cross over each other)

◦  Infundibulum – conical process behind optic chiasma – pituitary gland attached here

◦  Posterior pituitary gland – hang from hypothalamus

◦  Mammillary bodies – round structures behind infundibulum

◦  Pineal gland – cone-shaped attached to upper portion of the area

Limbic System

  • Thalamus, hypothalamus, and the basal nucli
  • Used to control emotional experience and expression