chapter one

Neurophysiology
Chapter One Outline

Neuroanatomy

I. Important terms & directions:
1. anterior or rostral: means toward the head (beak) or front of the brain
2. posterior or caudal: means toward the tail or back of the brain
3. dorsal or superior: is the back & top of the head
4. ventral, inferior, basal: this surface faces the ground in four legged animals
5. ipsilateral: refers to structures on the same side
6. contralateral: refers to structures on the opposite side
7. distal: farther from the point of origin (farther from the midline of body)
8. proximal: nearest the point of origin (nearer the midline of body)
9. lateral: away from he midline of the body
10. medial: toward the midline of the body
11. afferent: axons extending toward a group of cells
12. efferent: axons extending away from a group of cells

II. slicing
1. transversely, giving us cross or frontal sections
2. parallel to the ground giving us horizontal sections
3. perpendicular to the ground (parallel with the neuroaxis) giving us sagittal
sections

Cerebral Cortex:

I. general information:
1. outer most layer of the brain & about 3 mm thick.
2. It is convoluted (wrinkled)
3. 90% of cerebral cortex is called neocortex
4. The convulsions consist of
A. sulci (small grooves)
B. fissures (large grooves)
C. gyri (the bulges).
5. The cerebral cortex consists of cell bodies mostly
7. Brodmann divided the cortex (i.e., Brodmann’s map)(Kingsley p. 14)

II. sulci & fissures:
Kingsley p. 12: lateral view
1. central sulcus (Rolondic fissure): divides the frontal from the parietal lobe
2. precentral sulcus: runs parallel to the central sulcus
3. postcentral sulcus: also runs parallel with the central sulcus
4. inferior temporal sulcus:
5. superior temporal sulcus:
6. lateral fissure: divides temporal lobe from frontal & parietal lobes
B. insular cortex (insula) lies at the bottom of this fissure
a. operculum: cortex that surround the insula

Kingsley p. 4, 10, 11: dorsal & medial views
7. longitudinal fissure: divides the two hemispheres (p.10)
A. falx cerebri: dural tissue inside the fissure (p. 4)
B. corpus callosum at the bottom of the fissure (p. 11)
8. calcarine sulcus: on the medial surface (p.11)
9. parieto-occipital sulcus: mostly on the medial surface (p. 11)
10. cingulate sulcus: on the medial surface (p.11)
A. this is above the cingulate gyrus (cingulate)
a. cingulate is continuous with parahippocampal gyrus (p. 11)
11. sulcus of the corpus callosum: on the medial surface (p. 11)

Kingsley p. 13: ventral view
12. collateral sulcus: on the ventral surface
A. parahippocampal gyrus is medial to this sulcus
B. occipitotemporal gyrus is lateral to this sulcus
13. rhinal sulcus: a short sulcus on the ventral surface
A. parahippocampal gyrus (anterior part) is medial to this sulcus
    a. cortex that hugs the brainstem
    b. part of parahippocampal gyrus is called the uncus
    c. anterior portion of the gyrus is often called entorhinal cortex
    d. pyriform cortex=entorhinal cortex + uncus
14. Olfactory sulcus: on the ventral surface
A. mostly concealed by the olfactory bulb
B. gyrus rectus is medial to the olfactory sulcus
C. orbital gyrus is lateral to the olfactory sulcus

III. basic lobes:
Kingsley p. 11, 12, 13: lateral & medial views
1. occipital lobe: This is the most posterior cortex (p. 12)
A. contains the primary visual cortex
B. parieto-occipital sulus: separates parietal & the occipital lobes (p. 11)
C. calcarine sulcus: divides this in two (p.11)
2. parietal lobe:
A. rostral to the occipital lobe, caudal to the central sulcus, & dorsal to the
lateral sulcus
3. temporal lobe: is under the temples (p. 12)
A. the area ventral to the lateral fissure
B. uncus (part of the parahippocampal gyrus) (p.11, 13)
a. amygdala and hippocampus are below this cortex
4. frontal lobe is under the forehead (p. 12 & 13)
A. it is divided into superior, middle, & inferior frontal gyri (p.12)
B. gyrus rectus: seen on ventral surface (p.13)
C. olfactory tract & bulb: seen on ventral surface (p.13)
5. limbic lobe (of Broca): or limbic cortex.
C. consists of the cingulate gyrus & parahipppocampal gyrus

IV. White matter: this refers to myelinated axons
Terms used to refer to groups of myelinated axons include:
A. tracts B, fibers C. lemniscus D. fasciculus
E. column F. peduncle G. stria H. capsule
1. e.g., internal capsule (IC)connects the cortex with subcortical areas
      (Kingsley p. 15, 286, 287, 290;
    A. axons leave the cortex forming the corona radiata
    B. descending fibers terminate in the midbrain (i.e., cerebral peduncle)
    C. medial to IC is the thalamus and caudate N. Laterally the putamen &
        globus pallidus

V. Gray matter: this refers to neuron cell bodies and dendrites
Terms used for a group of neuron cell bodies in the CNS include:
    A. a nucleus
    B. lamina
    C. layer

A group of cell bodies (gray matter) in the PNS is called a ganglion (plural ganglia). One exception is the basal ganglia

Diencephalon:

I. gross features:
1. observable only from the ventral side (Kingsley p. 20)
A. just caudal to the optic chiasm
2. the medial surface of the diencephalon forms the 3rd ventricle
(Kingsley p. 174, 175 & 290)
3. fornix conceals the dorsal surface of the diencephalon (Kingsley p. 18)
A. fornix: fibers extending from hippocampus & curling over the thalamus
& ending to the mamillary bodies (Kingsley p. 290)
4. internal capsule: is just lateral to the diencephalon (Kingsley p. 290)

II. components of the diencephalon
1. thalamus: largest component of the diencephalon
   A. interthalamic adhesion: connects the thalami (Kingsley p. 174)
   B. dorsal surface forms the central part of the floor of the lateral ventricles
        (Kingsley p. 290)
   C. it is divided into several nuclei
      a. some nuclei receive sensory input then send it to the cortex
          e.g., lateral geniculate body: receives info. from the retina
          e.g., medial geniculate body: receives auditory info.
      b. some are involved in memory, emotion, & sleep

2. subthalamus: ventral to the thalamus (Kingsley p. 290)

3. epithalamus: dorsomedial to the thalamus (adjacent to roof of 3rd vent.)
     (Kingsley p. 16, 18, & 290)
   B. it includes the pineal gland:
   C. it includes the habenula:
   D. it includes the stria medullaris: tract forming a roof over the 3rd
        ventricle (on dorsal & medial part of the thalamus)

4. hypothalamus: between the 3rd ventricle & the subthalamus
     (Kingsley p. 492)
   A. neurohypophysis: posterior pituitary (outgrowth of the hypothalamus)
   B. anterior pituitary is not part of the brain
   C. infundibulum: connects the hypothalamus to the pituitary
   D. mamillary bodies: most caudal part of the hypothalamus
       (Kingsley p. 20, 490, 491)

brainstem

I. brainstem = myelencephalon + metencephalon (together called the
hindbrain) + mesencephalon (midbrain) cerebellum not included
1. this is the entry point for most of the cranial nerves
2. reticular formation (RF): occupies the central core of the brainstem

II. brainstem parts in a bit more detail
1. myelencephalon: medulla oblongata
   A. ventral view of medulla (Kingsley p. 20)
     a. ventral surface: ventral median fissure & ventral lateral fissure
         & medullary pyramids between these two
     b. ventrolateral surface: bump on each side called inferior olive
     d. cranial nerves IX, X, & XII exit from the medulla

   B. dorsal view of medulla (Kingsley p. 16)
     a. dorsal intermediate sulcus separates 2 ridges
       ?one ridge created by the fasciculus gracillis (more medial)
       ?the other ridge created by the fasciculus cuneatis (more lateral)
     b. dorsal median sulcus separates the gracile fasciculi
     c. area postrema: V shaped area on the ventral surface

2. metencephalon: pons with cerebellum attached on the dorsal surface
      (cerebellar peduncles attach these two)
   A. pons ventral view (Kingsley p. 20)
     a. a big bulge called the basis of the pons
     b. cranial nerve V exit from the ventrolateral surface
     c. cranial nerves VI VII & VIII exit from the junction of pons & medulla
   B. pons dorsal view: cerebellum strapped on by the cerebellar peduncles

3. mesencephalon: midbrain (brainstem rostral to the hindbrain & caudal to
    the forebrain)
A. midbrain ventral view (Kingsley p. 20)
    a. cerebral peduncles (axons extending to the cerebral cortex)
      ?interpeduncular fossa: space between the peduncles
B. midbrain dorsal view (Kingsley p. 16)
    a. tectum (little hills): corpora quadrigenina
     ?superior colliculi:
     ?inferior colliculi:
C. Inside the midbrain (tegmentum): (Kingsley p. 242)
    a. rostral end of the RF:
    b. periaqueductal gray:
    c. red nucleus:
    d. substantia nigra:

Spinal Cord

The spinal cord is protected by vertebrae, meninges, & a cushion of CSF

I. meninges & ligaments (Kingsley p. 4, 26
1. pia mater: innermost layer of meninges
2. dura mater: forms a tube from the sacral vertebra to the foramen magnum
3. arachnoid layer: this lies against the inner surface of the dura
A. subarachnoid space filled with fluid is below this membrane
4. epidural space exist between the dura and the wall of the spinal canal
5. the cord is suspended by the denticulate ligament

II. Fissures, sulci, & position of the roots (Kingsley p. 24, & 168)
Dorsal side:
1. dorsal median sulcus: as in the medulla
2. dorsal roots (axons) enter here
Ventral side:
1. ventral medial fissure: as in the medulla
2. ventral roots (axons) exit here

III. size, segments, & roots of the cord: (Kingsley p. 24, 26, 27)
1. There are 31 pairs of spinal nerves.
A. divided into cervical (8), thoracic (12), lumbar (5), sacral levels (5), &
cocygeal (1)
B. Each dorsal & ventral root is broken into a series of rootlets (p. 24)
2. The cord ends in adults opposite the first & second lumbar vertebrae.
3. the lowest part of the cord is called the conus medullaris
4. Filum terminale is a slender filament in the middle of the cauda equina.
5. the dorsal & ventral roots join just distal to the dorsal root ganglia to
form a spinal nerve
7. the spinal cord is enlarged in two areas to innervate the limbs (King p. 26)
A. a cervical enlargement
B. lumbar enlargement
8. lumbar puncture: a procedure to obtain a sample of CSF (p. 26)

peripheral nervous system (PNS):

I. PNS is broken into 2 basic parts
1. somatic nervous system:
A. brings in sensory information to CNS (afferents).
B. connects the voluntary muscles with the CNS (efferents).

2. autonomic nervous system (self governing): controls smooth muscle, cardiac muscle, & glands. (Kingsley p. 473)

The autonomic nervous system (ANS) has 2 systems
A. sympathetic division: associated with expenditure of energy
    a. preganglionic cells found in thoracic & lumbar regions of spinal cord.
    b. axons synapse in the spinal sympathetic ganglia (postganglionic cell)
    c. sympathetic ganglia neurons send axons to target organs.
B. parasympathetic division: increasing the bodies stored energy
    a. preganglionic parasympathetic cells are found in two regions
      (1) the cranial nerve nuclei
      (2) the sacral area of the spinal cord.
    b. the preganglionic fibers synapse very close to the target organ
        (ganglia are close to the target & postganglionic fibers are quite short)

II. arrangement & ensheathment of the PNS
1. groups of axons are arranged in nerves and 3 tissues surround
these nerves
A. epineurium: an entire nerve is surrounded by an epineurium
B. perineurium: this membrane surrounds each independent fascicle
C. endoneurium: this surround individual nerve fibers

Meninges:

Meninges: this is the protective sheath that covers the CNS

I. dura matter (hard mother): the outer layer, it is thick, tough, & unstretchable.
    It lines the skull.
2. cerebral dura has 2 layers (Kingsley p. 4)
    A. meningeal layer & endosteal layer (this adheres to the skull)
    B. the layers may divide to form a cavity or sinus
    C. fused layers form a dural fold or septum.
         ?falx cerebri: between the cerebral hemispheres
         ?tentorium cerebelli: fold between cerebellum & cerebral hemispheres
3. spinal dura
    A. endostreal blends into the membrane on the vertebra (periosteum)
    B. meningeal layer is not attached to the bone (epidural space)

II. arachnoid layer: the middle layer
1. beneath this you have the arachnoid trabeculae
A. cisterns are wide spots in this web-like space

III. pia matter (pious mother): the inside layer, it is attached to the CNS

Blood supply to the brain

Arteries:
I. the brain is supplied by 2 pairs of arteries (Kingsley 31, 32, 33)
1. carotid arteries divide into
    A. middle cerebral artery:
    B. anterior cerebral artery:
2. vertebral arteries: supplies much of the brain stem
    A. they converge to form the basilar artery
      a. basilar artery has many branches (Kingsley. p. 31) & spits
          to form the post. cerebral arteries (Kingsley p. 33)
    B. parts of the spinal cord are perfused by branches of these arteries
         (Kingsley p. 31)
      a. ventral spinal artery:
      b. dorsal spinal arteries:
3. Circle of Willis: arterial blood from the above 2 systems mix by way of
      communicating arteries (Kingsley p. 31)
    A. posterior communicating artery:
      a. anterior communicating artery completes the circle
    B. communicating arteries are normally small but they can expand

II. spinal cord circulation:
    A. some comes from branches of the vertebral arteries (mentioned above)
    B. many of the spinal nerves carry arteries with them, these arteries divide
         into radicular arteries (Kingsley p. 24)

Venous drainage:
I. spinal cord
1. veins usually follow the arteries
2. an epidural venous network runs the length of the cord (King. p. 24)
II. the brain (Kingsley p. 38)
1. veins usually are closely associated with arteries
2. sinuses are sometimes formed (where dural layers separate)
    A. transverse sinuses: a pair at the back of the skull (Kingsley p. 5) Several
         sinuses drain into these
       a. superior sagittal sinus: on longitudinal fissure
       b. canernous sinus drains into this system
       c. straight sinus drains into this system
       d. inferior sagittal sinus: on inferior surface of the falx cerebri
       e. great cerebral vein of Galen:
    B. the transerse sinuses become the sigmoid sinus which drains into the
         internal jugular vein

Abnormalities in the vascular system
I. arteriovenous malformations: abnormal tangle of blood vessel
1. hemorrhaging can occur because these vessels are weak
II. aneurysm: a balloon-like swelling in the wall of an artery

Ventricular System

I. Ventricles are chambers in the brain (CNS is hollow) (Kingsley p. 44)
1. four hollow interconnected chambers where CSF circulates through
    A. lateral ventricles: one of these in each cerebral hemisphere.
    B. third ventricle: located in the midline of the brain diencephalon
    C. fourth ventricle: located in the midline of the brainstem
2. ventricle connections
    A. the 3rd and 4th ventricles are connected by the cerebral aqueduct.
    B. Interventricular foramen connect the lateral ventricles to the 3rd
    C. ventricles connect to the subarachnoid space thru apertures associated
         with the 4th ventricle
4. cerebrospinal fluid (CSF) is produced in the ventricles & circulates
    A. CSF is secreted by called choroid plexus
    B. CSF is reabsorbed into the venous blood by way of arachnoid villi

II. problems with CSF & intracranial pressure
1. hyrocephalus: enlargement of brain ventricles 2 types
   A. noncommunicating hydrocephalus: due to a blockage of CSF
         circulation.
   B. communicating hydrocephalus: excess production or too little
         reabsorption

2. increased intracranial pressure can be due to hematomas, tumors or
swelling of brain tissue after trauma.

Barriers in the nervous system

I. Blood-Brain Barrier (BBB): Some chemicals that may be found in the blood stream are not found in brain tissue.
1. components of the BBB
    A. capillaries in the CNS have no pores
    B. tight junctions between cells
    C. glial cell (astrocytes) processes pack tightly around capillaries

2. In certain areas of the CNS the BBB is weaker & allows chemicals to pass
    A. these organs have specialized receptors & other properties that allow
         certain chemicals to pass
    B. they are the interface between the nervous & endocrine systems e.g.,
      a. neurohypophysis:
      b. median eminence:
    C. others are involved in regulating chemicals in our bodies (Kingsley p.48)
      a. e.g., area postrema (controls vomiting) & subfornical organ

II. blood-CSF barrier: prevents blood molecules from mixing with CSF

III. CSF & brain: no real barrier here pia cells do not make tight junctions

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