1. THE NERVOUS SYSTEM

2. Divisions of the nervous system
Afferent
Sensory information from receptors to CNS
Efferent
Motor commands to muscles and glands
Somatic division
Voluntary control over skeletal muscle
Autonomic division
Involuntary regulation of smooth and cardiac muscle, glands
Central Nervous System
Brain and spinal cord
Peripheral Nervous System
All neural tissue outside CNS

3. Neuronal Organization: CNS
Two kinds of neural tissue found in both brain and spinal cord:
1. Gray matter
2. White matter

4. Neuronal Organization: CNS
Gray matter = unmyelinated neurons + neuroglia
-forms the outer layer of the cerebrum = neural or cerebral cortex
also forms nuclei deep in the brain = clusters of neuronal cell bodies in CNS
collections of nuclei can form a center (higher brain function)

5. Neuronal Organization: CNS
2. White matter = myelinated axons of neurons
cell bodies are found in the gray matter
axons are bundled together to form White matter tracts
conduct nerve impulses from gray region to gray region
Brain – three types of tracts (commisural, association, projection)
Spinal cord - two types: sensory and motor tracts (ascending and descending)

6. Figure 15.1 Major Divisions of the Brain
Major Regions of the Brain
Figure Major Divisions of the Brain

7. Cerebrum Cerebrum = largest portion of the brain
-left and right cerebral hemispheres divided by the longitudinal fissure
-hemispheres connected by the corpus callosum

8. many gyri and sulci have specific names e.g. Central sulcus
between the frontal and parietal lobes
-cerebral cortex is folded into ridges and grooves
-grooves = sulci
-sulci divide the cerebrum into lobes
-ridges = gyri (gyrus)
-specific gyri are for the processing of sensation, area of voluntary movement, speech, all thought processes -called motor and sensory areas

9. Cerebrum -cerebrum contains three categories of white matter tracts:
commissural – join areas between hemispheres
e.g. corpus callosum, anterior & posterior commissures
b. association – joins areas within a hemisphere
c. projection – joins cerebrum to brain stem

10. Gray Matter Nuclei: Basal Ganglia
modifies motor commands that have originated from the cerebral cortex
comprised of several nuclei including the:
1. caudate nucleus: role in posture and limb movement
2. putamen: precedes or anticipates body movements
3. globus pallidus: regulates muscle tone for movements
4. substantia nigra: role in eye movements
high concentration of dopanergic neurons

11. Diencephalon thalamus: 80% of the diencephalon
paired oval masses of gray matter organized into nuclei, interspersed with white matter
major relay station for most sensory impulses from the SC & brain stem
relays motor information from cerebellum into the cerebrum
relays nerve impulses to and from different areas of the cerebrum, the brain stem & cerebellum

12. Diencephalon hypothalamus
control of the ANS – role in regulating smooth & cardiac muscle contraction
hormone production – oxytocin and anti-diuretic hormone (ADH)
regulates emotional and behavioral patterns – rage, aggression, pain and pleasure + sexual arousal
4. regulates eating & drinking
5. controls body temp

13. Diencephalon
epithalamus – consists of the pineal gland and habenular nuclei
-pineal gland – part of the endocrine system
-secretes the hormone melatonin
-increased secretion in dark
-promote sleepiness and helps set the circadian
rhythms of the body (awake/sleep period)
subthalamus – works with the cerebrum and cerebellum to control body
movements

14. BRAIN STEM comprised of three structures: midbrain pons
medulla oblongata

15. Medulla Oblongata inferior most part of the brain stem
made up of white matter tracts and gray matter nuclei
white matter - sensory/ascending and motor/descending tracts
nuclei regulate autonomic functions
nuclei are known as reflex centers for regulating heartbeat and BP (cardiovascular center), respiration (respiratory center), plus vomiting, coughing, sneezing, hiccupping and swallowing
-associated with 5 pairs of
cranial nerves
VIII IX X XI
XII

16. Pons “bridge” connection from cerebrum to cerebellum
consists of multiple nuclei and tracts
nuclei control both somatic (voluntary) and visceral (involuntary) motor responses

17. MIDBRAIN
relay station between the cerebrum and the spinal cord, and between the cerebrum and cerebellum
extends from the pons to the diencephalon – as cerebral peduncles
white matter motor tracts through the pons into the SC
white matter sensory tracts up into the thalamus
cerebral
peduncle
pons
medulla
oblongata

18. MIDBRAIN Posterior portion = tectum
cerebellar
peduncle
corpora
quadrigemina
median
eminence
pineal
gland
thalamus
medulla
oblongata
Posterior portion = tectum
-midbrain also connects the cerebrum to cerebellum via cerebellar peduncles
-white matter tracts (motor & sensory)
-Corpora quadrigemina = superior & inferior colliculi
-reflex centers for eye movement, head and neck movement (protection), pupil size and eye tracking

19. Cerebellum divided into hemisphere with lobes - like the cerebrum
anterior and posterior lobes
has a superficial layer of gray matter called the cerebellar cortex - like the brain
deep to this gray matter are tracts of white matter and gray matter nuclei – like the cerebrum
evaluates and coordinates involuntary and voluntary motor activities initiated by the cerebrum and corrects problems by sending info back to the cerebrum
regulates posture & balance
uses sensory data and stored memories – “muscle memory”

20. The Limbic System called the emotional brain
involved in linking olfaction and memory to basic emotional behaviors
main components:
1. limbic lobe: includes the hippocampus (within the parahippocampal gyrus), the cingulate gyrus, the insula and the dentate gyrus
2. amygdala: integration center between the limbic system, cerebrum and various sensory systems
3. olfactory bulbs
4. mammillary bodies of the hypothalamus
5. fornix - tract of white matter that connects the hippocampus to the hypothalamus
fibers end at the mammillary bodies
6. hypothalmic nuclei
other areas
olfactory tract
amygdala
hippocampus
anterior thalmic nuclei
fornix
mamillary body
parahippocampal gyrus
hypothalmic nuclei
corpus callosum
cingulate gyrus

21. Protection: The Cranial Meninges
Cranium is covered with protective membranes = meninges
Cranial meninges are continuous with spinal meninges
3 layers: 1. outer, fibrous dura mater –comprised of an outer endosteal layer and and inner meningeal layer
large spaces for the circulation of blood can be found between these two layers = sinuses
e.g. superior sagittal sinus
2. middle arachnoid mater
3. inner, thin pia mater
the dura mater forms sheets (falx) that separate the cerebrum into hemispheres and the cerebellum from the cerebrum

22. Cranial Meninges there are spaces between these membranes
A. subarachnoid space: between the arachnoid and pia maters
large veins run through the subarachnoid space - e.g. cerebral veins
B. subdural space: between the arachnoid and the dura mater
potential space in the cranial region
C. epidural space – between the dura mater and the vertebral canal in the spinal column

23. Protection: CSF brain contains fluid-filled chambers = Ventricles
2 lateral ventricles, 1 third ventricle, 1 fourth ventricle
connects to the central canal which runs into the spinal canal
These chambers contain cerebrospinal fluid
made by specialized cells in the ventricles – choroid plexus (ependymal cells)

24. Flow of CSF
CSF continually circulates - ventricles and central canal to subarachnoid space
CSF is gradually reabsorbed into the blood through fingerlike projections into the dural venous sinuses = arachnoid granulations (arachnoid villi)

25. The blood supply to the brain
Arterial blood reaches brain via internal carotid and the vertebral arteries
both give rise to the Circle of Willis
made up of communicating arteries and cerebral arteries
the posterior communicating and cerebral unite to form the basilar artery
the basilar the formed from the union of the vertebral arteries
Venous blood leaves via internal jugular veins

26. Spinal Cord length in adults = 16 to 18 inches
31 segments – each with a pair of spinal nerves
Cervical and lumbar enlargements
cervical = C4 to T1, nerves to and from upper limbs
lumbar = T9 to T12, nerves to and from lower limbs
Cervical
and lumbar
enlargements

27. Spinal Cord Tapers to conus medullaris at lumbar area
fragments into a cauda equinae as it runs through the sacral canal
dorsal & ventral roots of lowest spinal nerves
filium terminale arises from the conus medullaris
extension of the pia mater that anchors the SC to the coccyx

28. Histology of the Spinal Cord
Central gray matter
Contains cell bodies of neurons and glial cells + unmyelinated axons
Gray matter projections are horns
Peripheral white matter
Myelinated and unmyelinated axons
Organized as tracts or columns

29. Histology of the Spinal Cord
Organization of Gray Matter
1. Posterior gray horns
sensory neurons entering the cord
2. Anterior gray horns
somatic motor neuronal cell bodies
3. Lateral gray horns
visceral motor neuronal cell bodies
Gray commissures
axons of interneurons crossing cord
Organization of White matter
Anterior, lateral and posterior white columns
tracts of myelinated neuronal axons
ascending = sensory information
descending = motor information

30. White matter tracts