The Central Nervous System

The Central Nervous System

CNS CNS: brain and spinal cord
Necessary for the maintenance of homeostasis Contains 1011 neurons Contains 1014 synapses Responsible for everything we perceive, do, feel, and think

The Brain BRAIN MATTER AND CEREBROSPINAL FLUID CEREBRUM
a- Cerebral hemispheres a1- Lobes a2- Basal ganglia (nuclei) b- Brain stem b1-Diencephalon b1-1- Thalamus b1-2- Hypothalamus b2- Midbrain b3- Pons b4- Medulla oblongata c- Limbic system d- Reticular formation CEREBELLUM

Cerebrum Five paired lobes within two hemispheres
Gray matter in cortex and in deeper cerebral nuclei White matter inside Higher functions are performed by the brain

Brain matter What is gray and white matter?
Gray matter: neurons and unmyelinated axons White matter: myelinated axons

Protection and Coverings
Cranial bones Meninges - 3 layers: - Dura mater, Arachnoid, and pia mater Between dura mater and arachnoid: subdural space In between arachnoid and pia mater, in subarachnoid space: cerebro-spinal fluid (CSF)

Meninges

Meningitis

CSF Cushion the brain Provide a constant IF environment About 150 ml
Produced by the ependymal cells of the choroid plexus, in the ventricle Resorbed by the arachnoid granulations Continuously produced and continuously resorbed Composition slightly different from plasma

Cerebrospinal fluid circulation

CSF circulation

Hydrocephalus A blockage of CSF circulation will trigger an accumulation of CSF in the ventricle This will result in hydrocephalus

Hydrocephalus

Blood supply CNS comprises 2% of body weight (3–4 pounds)
Receives 15% of blood supply High metabolic rate Brain uses 20% of oxygen consumed by body at rest Brain uses 50% of glucose consumed by body at rest Depends on blood flow for energy

Energy supplies Depends on aerobic glycolysis
Requires glucose and oxygen No glycogen stores Fatty acids not used for energy Ketones used during extreme conditions

Brain structure

Cerebrum Two hemispheres
Surface have gyri, grooves(sulci) and fissures Two fissures: longitudinal (falx cerebri and cerebelli) and transverse (tentorium cerebelli) Corpus callosum

Cerebrum Cerebral cortex
- Lobes: 1 frontal, 1 parietal, 1 occipital, and 2 temporal and insula – surface is gray matter - Basal nuclei (or ganglia)- gray matter deep inside white matter.

Frontal lobe Voluntary motor control Personality
Concentration, planning, decision making Verbal communication

Frontal lobe : Motor area

Language Broca’s aphasia: due to damage in the Broca’s area of the brain. Speech slow and poorly articulated Wenicke’s aphasia: due to damages to Wernicke’s area produces a rapid speech without meaning. Comprehension destroyed

Speech areas

Parietal lobes Sensory interpretations Understanding speech
Formulating words to express thoughts and emotions Interpretations of textures and shapes

Sensory areas

“Small brain”

Temporal lobes Interpretation of auditory sensations
Memory of auditory and visual experiences

Occipital lobe Perception of vision Vision recognition
Focusing and eye movement

Memory Short and long term memory
Several regions of the brain involved, especially temporal lobe, hyppocampus Short  long term memory: medial temporal lobe Long term memory independent of temporal lobe Memory acquisition possible due to synapse changes

Basal Nuclei Mass of neurons located deep into the white matter
Help control of voluntary movement

Basal Nuclei

Diencephalon

Diencephalon Thalamus:4/5 of diencephalon Below lateral ventricles
Relay center through which sensory informations (except smell) pass, on the way to the cortex Many nuclei

Diencephalon: Hypothalamus and pituitary gland
Below thalamus Neural centers for many functions: - hunger, thirst, body temperature regulation - controls pituitary gland - contribute to sleep regulation, emotions (fear, anger, pain, pleasure..), sexual arousal

Hypothalamus

Midbrain Between diencephalon and pons Several nuclei:
- corpora quadrigemina: visual and auditory reflexes - red nucleus: motor coordination - nigrostriatal system (from substancia nigra- basal ganglia) motor coordination (involved in Parkinson’s disease) - cerebral peduncles: ascending and descending fiber tracts

Midbrain

Pons Between midbrain and medulla oblongata
Several nuclei associated with cranial nerves (V, VI, VII, and VIII) Respiratory centers: apneustic and pneumotaxic centers Communicates with cerebellum and medulla oblongata, and midbrain

Medulla oblongata Between pons and spinal cors
Numerous nuclei controlling cranial nerves (VIII,IX,X,XI, and XII), and vital functions: vasomotor, cardiac, respiratory, sneezing, swallowing centers Passageway for sensory and motor fibers Fibers “decussate” or cross over

Medulla oblongata

Cerebral lateralization
The cerebral cortex controls movement of the contralateral side Sensations project to the contralateral side of the parietal lobes The two hemispheres communicate through the corpus callosum Left side: language and analysis Right side: visual spatial tasks

Medulla oblongata

Limbic system Emotion & motivation Mesh of neurons around the brain
Connect to hypothalamus Involved in control of: - aggression, fear, feeding, sex and goal-directed behavior

Reticular formation Complex network of nuclei and nerve fibers in medula, pons, midbrain, diencephalon Reticular Activating System (RAS): maintain a state of alert consciousness

Cerebellum “small brain”
Fibers from cerebellum red nucleus  thalamus  cerebral cortex Other tracts connect cerebellum to pons, midbrain, medulla Receives input from proprioreceptors (from muscles, tendon)  coordinates movement, control equilibrium

Cerebellum

Readings Chp. 9, p Not expected to be known:

The Central Nervous System

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