the central nervous system. cns –cns: brain and spinal cord –necessary for the maintenance of...

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. 216-236

• Not expected to be known:

the central nervous system. cns –cns: brain and spinal cord –necessary for the maintenance of...

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