Weighs 1.5 Kg

100 Billion neurons

Recieves 20% CO 

750 ml/min

54 ml/100 gm/min

Activity below 15 ml/100 gm/min will cause brain activity to cease 

1-10 mmHg

Pressures > 20 mmHg requires treatment 

Causes linear change in CBF 20-60 mmHg

4% change in CBF for each 1 mmHg change in PaCO2

Decreases CBF and CMRO2

5% for each 1 degree C change 

Process of formation of the neural tube from the ectoderm

Neural plate--> starts to fold in 3rd week after fertilization--> cells alongside the tube escape union and form the neural crest

Alar Plate= dorsal part of the neural tube; sensory

Basal Plate= ventral part of the neural tube; motor 

Week 5 post conception arches form that protect the spinal cord

Neural arches are at first seperate and later fuse midline to form the vertebral spines

Failure to unite results in spina bifida 

Prosencephalon= forebrain

Mesencephalon= midbrain

Rhombencephalon= hidbrain 

Telencephalon--> Cerebral cortex & Corpus Striatum 

Diencephalon--> Thalamus & Hypothalamus

Metencephalon--> pons & cerebellum 

Myelencephalon--> medulla oblongata 

Medulla

Pons

Midbrain

Reticular Formation

(Responsible for all basic vital life functions) 

Pathway for ascending and descending nerve tracts

Center for HR, breathing, Swallowing, vomiting 

Pyramids are descending tracts involved in conscious control of skeletal muscle 

Inferior portion of the pyraminds decussates to control the opposite side of the body

 contains ascending and descending nerve tracts

Relay between cerebrum & cerebellum 

Reflex centers sleep & respiratory centers which work with the medulla 

contains ascending and descending nerve tracts

Visual reflex center; part of auditory pathway 

Scattered throughout the brainstem and controls cycic activity

Sleep wake cycles 

Control of muscle movement, tone, balance

Regulates intentional movement

Involved in learning motor skills 

3 large tracts: Superior, Middle, Inferior peduncle 

2 hemispheres divided by a primary fissure into anterior and posterior lobes 

2nd largest structure of the brain 

2 prominent enlargements protruding from the anterior surface of the medulla

Functions in balance, coordination, and modulation of sound from the inner ear 

Smallest region of the brainstem 

Contains ascending and descending nerve tracts, visual reflex center, part of a auditory pathway

Contains Corpora Quadrigemina --> each mound is called a colliculus 

2 Superior involved in visual

2 Inferior involved in hearing and recieving their input from the skin and cerebrum 

Connects the cerebellum to the midbrain 

Major sensory relay center 

Influences mood and movement 

Largest part of diencephalon

Provides crude awareness 

Two thalami face one another across the slot-like 3rd ventricle 

Separated from the lentiform nucleus by the internal capsule 

Largest part of diencephalon 

Contain nuceli responding to olfactory stimulation and contains pineal body 

Pineal body plays role in controlling onset of puberty

May influence sleep wake cycle and other biorhythms 

Posterior portion of diencephalon, thin roof over 3rd venticle

Inside lining of the roof lies the choroid plexus- CSF production 

Major control center for maintaining homeostasis and regulating nerve function

"temp control" 

Smallest portion of diencephalon, located below the thalamus

Forms the floor of the 3rd ventricle

Contains the corticospinal tract/pyramidal tract which originates in the cortex

CST is the most important pathway in the CNS 

Mediates voluntary movement

Extends the entire vertical length of the CNS which makes it vulnerable to disease/trauma in the cerebral hemisphere or brainstem on one side and to spinal cord disease or trauma on the other side 

Hemispheres are divided by a longitudinal fissure, connected by the corpus callosum 

characterized by numerous folds and grooves 

80% of brain's mass

Higher mental function takes place: conscious perception, thought and conscious motor activity, can override most other systems

Located in the inferior cerebrum

Control of muscle activity and posture

Largely inhibit unintentional movement when at rest 

Located in cerebrum and diencephalon 

Autonomic reponse to smell, emotion, mood, memory, and other such function 

Inferior aspect of the diencephalon 

Attached to the hypothalamus via infundibulum

Supported by the sella turcia

Circle of Willis surrounds it providing it with a rich blood supply 

Divided into anterior (adenohypophysis) and posterior (neurohypophysis) 

Midbrain

Short section of brain stem between diencephalon and pons

Aquduct of Sylvius (connects the 3rd and 4th ventricles) 

Corpora quadrigemina

Cerebral peduncles

Red nucleus

Substania nigra 

Superior Colliculi- visual hand eye coordination

Inferior Colliculi- auditory reflexes

Cerebral Peduncles- reflex coordination motor fibers 

Surface of brain is composed of sulci and gyri which increase the surface area of the brain

Sulci: inward furrows

Deepest sulci: lateral sulcus (Sylvian fissure) and central sulcus (Rolandic fissure) combo divides the hermisphere into 4 lobes 

Gyri: outward ridges of the brain surface 

Frontal 

Parietal

Occipital 

Temporal 

5th Lobe Limbic Lobe 

Medial portion of the hemisphere and contains the hippocampus, fornix, and amygdala 

Function includes regulation of emotion, empathy, self awareness and assitance in motor control. Also pain judged by a degree

Receives and evaluates input for smell and hearing and plays an important role in memory. Separated from the rest of the cerebrum by a lateral fissure

Anterior and inferior portions are referred to as the "pyschic cortex" and is assocaited with brain functions as abstract thought and judgment 

The gray matter on the outer surface of the cerebrum is the cortex and clusters of gray matter deep inside the brain are nuclei 

The thickness of the cortex isnt uniform and ranges from 2-3 layers in primative parts and 6 layers in more advanced regions 

Consists of fiber tracts that connect areas of the cortex to other parts of the CNS 

White matter between cortex and nuclei

Contains association fibers, commissural fibers, projection fibers 

"Long and Short"

Connect areas of the cerebral cortex within the same hemisphere 

Transverse Fibers 

Connect one hemisphere to the other 

Corpus callosum is the largest group

Efferent and afferent 

Between the cerebrum and other parts of the brain form internal capsule 

Crucial for memory formation along with the amygdala.

Involved with retrieval of memory like recalling someone's name

Lesion in the temporal lobe that affects the hippocampus can prevent the brain from moving information from short-term to long term memory  

The part of the brain that aids in the storage of past memories 

Involved with the emotional overtone of that memory

Covers the subarachnoid space which contains the CSF that helps cushion the brain and cord 

Arachnoid space between arachnoid and pia mater 

Brain recieves blood from the internal carotids (anterior circulation) and verterbral arteries (posterior circulation)

Vertebral arteries form the basilar artery which divides at the pons into the two posterior cerebral arteries 

The basilar artery and in the internal carotids both contribute to the circle of willis 

Blood supply to the forebrain is derived from the 2 internal carotids and from the basilar 

Each interal carotid enters the SA space by way of the roof of the cavernous sinus 

Continuation of the internal carotid

Recieves 60-80% of carotid BF

Supplies 2/3 of the lateral surface of the brain 

Terminal branches of the basilar artery

Generally supplied by the posterior cerebral arteries, however about 25% of population the internal carotid persists as the primary source of blood by way of large posterior communicating artery 

Posterior Cerebral Arteries

Posterior Communicating Arteries

Internal Carotid Arteries

Anterior Communicating Arteries 

Aorta

Brachiocephalic Trung 

Common Carotid

Internal Carotid

Circle of Willis 

Aorta

Subclavian

Vertebral

Basilar 

Drain the thalamus and choroid plexus

The 2 internal cerebral veins unite beneath the corpus callosum to form the great cerebral vein of Galen 

Drain out through jugular 

700-850 mL/min

Autoregulation: the capacity of a tissue to regulate its blood supply

Most rapid source of autoregulation is the intraluminal pressure within the arterioles 

2nd most rapid is hydrogen ion concentration in the CNS (CO2 causes dilation) 

Tight junctions around capillaries which are only permeable to lipid soluble and very small molecules 

Sodium is pumped in and potassium is pumped out

ECF that bathes neuron accounts for 15% of the brain's total volume 

Resides in the specialized ependymal cells that line the ventricles/choroid plexus

Cillia repaced by microvilli

Cells are bonded by tight junctions

Epithelium contains numerous enzymes involved in transport of ions and metabolites 

Starts at the foramen magnum 

Ascending fibers= afferent= sensory

Descending fibers= efferent= motor

Spinal reflex arcs take sensory impulse into the cord and go right back out to the motor neuron and allows very quick action to take place 

Grey matter is on the inside and the white matter is on the outside 

C1= atalas= holds head up

C2= axis= rotates head on it 

Cervial: C1-C7, 8 crainal nerves

Thoracic: T1-T12, 12 thoracic vertebrae

Lumbar: L1-L5, 5 lumbar vertebra

Sacral: S1-S5, 5 sacral vertebrae 

2 verterbrals give off anterior and posterior spinal branches

Anterior branches fuse and form the anterior spinal artery 

Posterior spinal arteries descend along the line of attachment of the dorsal nerve roots on each side

Radiculospinal bracnhes from the verterbrals and from the intercostals 

Artery of Adamkiewicz is the largest radiculospinal artery 

Supplies the lower 2/3 of the anterior cord

Originated between T9-T11

Damage to this artery the patient is at risk for postoperative paraplegia with incontinence 

Anterior and Posterior Spinal Veins

Drain outward along the nerve roots

Obstruction to venous outflow will result in inflammaiton of the spinal cord eith progressive loss of function 

32 nerve roots sheathed by the pia mater and float in CSF

33 vertebra house and protect the cord

Extradural veins have no valves and reflux of blood from the segmental veins territories 

Adult level of spinal cord ending (L1-L2) does not occur until 3 weeks post birth 

Lumbosacral roots are often affected by lumbar spinal stenosis where the vertebral canal is narrowed d/t prolapsing disks or boney osteophytes 

95% of immediately above or below L5 

Choroid Plexus

Lateral Ventricles

Intraventricular Foramen of Monroe

Third Ventricle

Aquaduct of Sylvius

Fourth Ventricle

Foramen of Magendie & Luschka

Central Spinal Canal

SA Space

Reabsorbed by the arachnoid villi 

Functional and structural units of the nervous system

Generate and conducte electrical changes (nerve impulses)

Form a shell or cortex on the surface of the cerebral and cerebellar hemisphere

Nuclei are clusters of neurons buried within the white matter 

Nerve glue (connective tissue of the nervous system)

Provide nourishment and support for neurons 

Outnumber neurons 5:1

Schwann Cells

Oligodendrocytes

Astrocytes

Ependymal Cells

Satellite Cells 

Form the myelin sheath around the peripheral axons

NOT found in CNS, only PNS 

Tightly couples

No synaptic delay

Modulation is not possible

Function to ensure synchronus activity

1 m/sec

All contain Na and K and produce action potential 

Conduction is slower

thicker the fiber the faster the conduction 

100 m/sec

Myelin sheath provides insulation for the axon

Nodes of Ranvier cause intrerruption, saltatory conduction

Much faster rate