Central Nervous System
The CNS
Unit 10 Synopsis
Wordbytes
-algia
pain
Enceph-
Brain
Nigr-
Black
Cortex
Outer Layer
Cephalo-
Head
Hemi-
Half
Oculo-
Eye
pons
Bridge
Corpus
Body
Hypo-
Under
Mes-
Middle
-phasia
Speech
Epi-
Above
Mes-
Middle
Opti-
Eye
Protection of the CNS
Bones:
The brain is encased by 8 skull bones: frontal, temporal (2), occipital, parietal (2), ethmoid, sphenoid.
The spinal cord is encased by 26 bones that make up the vertebral column,
​
Meninges:
Surrounding the brain and spinal cord are protective layers called the meninges. There are three distinct layers of meninges:
1. Dura Mater- the hard, outermost covering. Translates to " tough mother"
2. Arachnoid Mater- the middle layer that has a web-like appearance. Translates to "spider mother"
3. Pia Mater- the innermost covering. Translates to "tender mother"
​
Spaces between the layers of meninges:
1. Epidural space: between the skull and the dura mater. Location of lumbar puncture or analgesic injection
2. Subarachnoid space: filled with CSF
3. Subdural space: only opened in cases of trauma, such as a brain bleed.
​
​
​
​
Ventricles and the Cerebrospinal Fluid:
Cerebrospinal fluid pathway:
1. CSF is produced in the choroid plexus of the lateral ventricles (1 and 2).
2. CSF will enter the 3rd and 4th ventricles.
3. CSF will then follow one of two pathways:
1. enter the central canal of the spinal cord
2. enter the subarachnoid space of the meninges
​
4. CSF is resorbed in the blood via the arachnoid granulations that project in the dural sinuses.
​
CSF numbers:
Total volume within the spaces above: 150 mL
CSF is replenished every 3-4 hours
Approximately 1 liter is secreted daily
​
CSF functions:
Mechanical protection (e.g. cushioning)
Chemical protection (e.g. hormonal)
​
​
​
​
​
​
​
Brain
The brain is the largest and most complex portion of the nervous system.
Located in the cranial cavity
​
Structure of the Cerebrum
The cerebrum is the largest portion of the brain that is divided into 2 hemispheres. Divided by the longitudinal fissure.
Predominately made of white matter (oligodendrocytes), however, the cerebral cortex is made of gray matter
The corpus callosum is the structure that allows communication between the hemispheres.
The hemispheres are further divided into lobes:
Frontal:
Anterior portion located under the frontal bone.
Involved in personality, decision-making, and voluntary movement
Broca's area: speaking ability
Parietal
Located superiorly, between the frontal and occipital lobes.
Integration and interpretation of sensory information (particularly vision);
Identification of objections and spatial relationships
Wernicke's area: speech interpretation
Temporal
Inferior to the parietal lobe, with the occipital lobe and cerebellum located posteriorly.
Short term memory, speech, hearing, musical rhythm
Occipital
Posterior lobe
Functions in vision
​
Functionally can be divided into three categories:
1. Motor areas that are found in the frontal cortex
2. Sensory areas that function in conscious awareness of sensations within the parietal, occipital, and temporal lobes
3. Association areas within the cerebral cortex that are further divided into:
A. General areas that are not directly involved in motor or sensory function. Involves all lobes
B. Association traits that: analyze and interpret sensory experiences and provide memory, reasoning, verbalizing, judgment, and emotions
Gyri are elevated regions in the brain
Sulci are the shallow depressions
​
The Cerebellum
Cauliflower appearance (Arbor vitae)
Regulated balance and coordination; coordinates voluntary muscle movements and posture
​
The Brain Stem
Further broken down into three parts
1. Medulla Oblongata
Regulates autonomic nervous system functions such as breathing rate, heartbeat, blood pressure (vasoconstriction), and serves as a conduit between the brain and spinal cord
2. Pons
Main connection between the cerebellum and brain stem.
Pneumotaxic area that regulates breathing rate
Reticular formation involved in sleep cycles
3. Midbrain
Inferior colliculus: auditory brain stem pathway
Superior colliculus: combines information about visual space, audition, and somatosensory space.
​
The Diencephalon
1. Thalamus: all sensory information (except olfaction) pass through here before processing.
Determines what information is important to garner attention.
2. Hypothalamus: thermoregulation, hunger, thirst
​
The Limbic System
Emotional response
Includes:
Hypothalamus: see above
Hippocampus: involved in memory and learning
Amygdala: Within the limbic system that controls emotions. Associated with stress, reward pathway, and "fight or flight"
​
Glands:
Pineal gland: regulates sleep cycle
Pituitary gland: master gland that regulates production of a wide variety of other hormones
​
​
Cranial Nerves
Cranial nerves
I. Olfactory (sensory)
II. Optic (sensory)
III. Oculomotor (motor)
IV. Trochlear - controls single muscle of the eye (cross eyes) (motor)
V. Trigeminal - innervates face and jaw muscles (both)
VI. Abducens - stimulates some eye muscles (motor)
VII. Facial - enable facial expressions (both)
VIII. Auditory (sensory)
IX. Glossopharyngeal - tongue and pharynx (both)
X. Vagus - digestion, heart rate, respiration, reflex actions (coughing, sneezing, swallowing) (both)
XI. Spinal accessory - move head and shoulders (motor)
XII. Hypoglossal - swallow and talk (motor)
Lateralization of Function
"Are you left brained or right brained?" This common question, while interesting, is a gross oversimplification of a complex system. The left side has more functioning in languages, whereas the right side is more involved in spatial and nonverbal reasoning. Both sides perform these functions, but overall functioning may be performed more on one side.
​
​
