The document summarizes several key aspects of the nervous system, including: 1) The reticular formation is involved in motor control, awake/sleep cycles, and damage results in permanent coma. The cerebellum coordinates voluntary muscle movements. 2) The meninges provide protection to the brain and spinal cord. Cerebrospinal fluid acts as a cushion. Ventricles circulate this fluid through the brain and spinal cord. 3) The nervous system develops during the first month of embryonic development and continues maturing after birth through myelination.

1. THE NERVOUS SYSTEM
(Part two)

2. ReticularFormation
 Diffuse mass of gray matter along the brain
stem
 Involved in motor control of visceral organs
 Reticular activating system plays a role in
awake/sleep cycles and consciousness
 Damage here results in a permanent coma

3. ReticularFormation

4. Cerebellum
 large, cauliflower-like structure located dorsally to the
pons and medulla and inferiorly to the occipital lobe of
the cerebrum (separated by transverse fissure);
 note pattern of white matter (within gray matter) = "arbor
vitae";
 coordinates all voluntary muscle movements
(subconsciously); skilled movements, posture,
equilibrium (i.e. balance).

5. Cerebellum

6. ProtectionoftheCentralNervous System
 Scalp and skin Cerebrospinal
fluid
 Skull and vertebral Blood brain
barrier column
 Meninges
Figure 7.16a

7. Meninges
 Dura mater
Double-layered external covering the brain
Periosteum – attached to surface of the
skull
Meningeal layer – outer covering of the
brain and continues as the dura matter of
the spinal cord
Folds inward in several areas that
attaches the brain to cranial cavity

8. Meninges
 Arachnoid layer
 Middle layer that is web-like
 Pia mater
 Internal layer that clings to the surface of the brain
following every fold
Subarachnoid space filled with cerebrospinal
fluid
 Arachnoid villi – projections of arachnoid
membrane protruding through the dura matter

9. CerebrospinalFluid
 Similar to blood plasma composition
 Less protein, more vitamin C, different ions
 Formed by the choroid plexus
 Forms a watery cushion to protect the brain
 Circulated in arachnoid space, ventricles, and
central canal of the spinal cord

10. Ventriclesand Location of the Cerebrospinal
Fluid
Figure 7.17a

11. Ventriclesand Location of the Cerebrospinal
Fluid
Figure 7.17b

12. Blood BrainBarrier
 Includes the least permeable capillaries of the body
– only H2O, glucose, and essential amino acids get through
 Excludes many potentially harmful
substances
 Useless against some substances
Fats and fat soluble molecules
Respiratory gases
Alcohol
Nicotine
Anesthesia

13. TraumaticBrainInjuries
 Concussion
 Slight brain injury – dizzy or lose consciousness briefly
 No permanent brain damage
 Contusion
 Nervous tissue destruction occurs - does not regenerate
 If cortex is damaged, coma for hours or life
 Cerebral edema
 Swelling from the inflammatory response
 May compress and kill brain tissue

14. Cerebrovascular Accident(CVA)
 Commonly called a stroke
 The result of a clot or a ruptured blood vessel supplying
a region of the brain
 Brain tissue supplied with oxygen from that blood
source dies
 Loss of some functions or death may result

15. Alzheimer’sDisease
 Progressive degenerative brain disease
 Mostly seen in the elderly, but may begin in
middle age
 Structural changes in the brain include abnormal
protein deposits and twisted fibers within
neurons
 Victims experience memory loss, irritability,
confusion and ultimately, hallucinations and
death

16. SpinalCord
 Extends from the medulla
oblongata to the region of
T12
 Below T12 is the cauda equina
(a collection of spinal nerves)
 Enlargements occur in the
cervical and lumbar regions

17. SpinalCordAnatomy
 Internal gray matter - mostly cell bodies that surround the
central canal of the cord
Dorsal (posterior) horns
Anterior (ventral) horns
Contains motor neurons of the somatic nervous
system, which send their axons out the ventral root
Together they fuse to form the spinal nerves
Nerves leave at the level of each vertebrae

18. SpinalCordAnatomy
 Cell bodies of sensory neurons, whose fibers enter the
cord by the dorsal root, are found in an enlarged area
called the dorsal root ganglion
 Damage to this area causes sensation from the body area
served to be lost

19. SpinalCordAnatomy
 Exterior white mater – conduction tracts
 Posterior, lateral, and anterior columns
 Each contains a number of fiber tracts make up of axons
with the same destination and function

20. SpinalCordAnatomy
 Central canal filled with cerebrospinal
fluid

21. CranialNerves
 12 pairs of nerves that mostly serve the head and neck
Numbered in order, front to back – names reveal structures they
control
 Most are mixed nerves, but three are sensory only
 Optic, olfactory, and vestibulocochlear

22. Distribution of Cranial Nerves

23. Olfactory Nerve (sensory only)
 Exits cranium through: Olfactory foramina of
cribriform plate of ethmoid
 Distribution: Nasal mucosa
 Functions: Transmits olfactory data to brain

24. OpticNerve(sensoryonly)
 Exits cranium through: Optic foramen in orbits
 Distribution: Eye
 Functions: Transmits visual data to brain
 Special: The optic nerve is not, technically, a nerve;
it is a tract of white matter extending from the brain
to the retina of the eye, which is also
developmentally a part of the brain.

25. Oculomotor Nerve (motor only)
 Exits cranium through: Superior orbital fissure
 Distribution: Most extrinsic eye muscles;
ciliary muscle; muscles of iris
 Functions: Moves eyeball; accommodates lens;
constricts pupil; controls eyelid

26. TrochlearNerve(motoronly)
 Exits cranium through: Superior orbital
fissure
 Distribution: Superior oblique muscle of eye
 Functions: Angular movement of eyeball

27. TrigeminalNerve(sensoryandmotor)-three
branches
1. Ophthalmic branch
 Exits cranium through: Superior orbital fissure
 Distribution: Eye
 Functions: Cutaneous sensation to eyeball, initiates
blinking reflex

28. Maxillary branch
▸ Exits cranium through: Foramen rotundum
▸ Distribution: Maxilla
▸ Functions: Cutaneous sensation to maxillary region,
upper lip, lateral nose, conjunctiva, lower eyelid,
maxillary teeth, and cheek
TrigeminalNerve(sensoryandmotor)-three
branches

29. Mandibular branch
▸ Exits cranium through: Foramen ovale
▸ Distribution: Mandible, temporomandibular joint, muscles
of mastication and swallowing, tensor tympani
▸ Functions: Cutaneous sensation to mandible, lower lip,
mandibular teeth, oral mucosa, and temporomandibular
joint; controls muscles of mastication, contributes to
swallowing and dampening of sound
TrigeminalNerve(sensoryandmotor)-three
branches

30. AbducensNerve(motoronly)-also called
Abducentnerve
 Exits cranium through: Superior orbital
fissure
 Distribution: Lateral rectus muscle of eye
 Functions: Moves eyeball laterally

31. FacialNerve(sensoryandmotor)
▸ Exits cranium through: Stylomastoid foramen
▸ Distribution: Anterior 2/3 of tongue; salivary and
lacrimal glands; muscles of face, scalp, and neck
▸ Functions: Facial expression, secretion of tears and
saliva, gustation, closing eyes, facial sensation,
kissing, licking, whistling, sucking, moving lips to
speak

32. VestibulocochlearNerve(sensoryonly)
▸ Exits cranium through: Internal auditory meatus
▸ Distribution: Semicircular canals and cochlea of ear
▸ Functions: Transmits data from senses of hearing
and equilibrium to brain

33. GlossopharyngealNerve(sensoryandmotor)
▸ Exits cranium through: Jugular foramen
▸ Distribution: Posterior 1/3 of tongue,
pharyngeal muscles, parotid gland
▸ Functions: Speech, salivation, swallowing,
gustation

34. VagusNerve(sensoryandmotor)
▸ Exits cranium through: Jugular foramen
▸ Distribution: Epiglottis, pharyngeal muscles, smooth
muscles of thorax and GI tract, cardiac muscle, GI glands;
only cranial nerve with distribution inferior to neck
▸ Functions: Gustatory and somatic sensation from pharynx
and epiglottis, swallowing, coughing, voice production,
gagging, smooth muscles actions of GI tract, secretions of
GI glands, slowing heart rate

35. AccessoryNerve(motoronly)- two branches
▸ Exits cranium through: Jugular foramen
▸ Distribution:
 Cranial branch: muscles of pharynx, larynx, and soft palate
 Spinal branch: Sternocleidomastoid and trapezius
muscles
▸ Functions:
 Cranial branch: Swallowing
 Spinal branch: Movement of head and shoulders

36. HypoglossalNerve(motoronly)
▸ Exits cranium through: Hypoglossal canal
▸ Distribution: Muscles of tongue
▸ Functions: Speech, swallowing, movement of
tongue

37. SpinalNerves
 There is a pair of spinal nerves at the
level of each vertebrae for a total of 31
pairs
 Spinal nerves are formed by the
combination of the ventral and dorsal
roots of the spinal cord
 Spinal nerves are named for the region
from which they arise

38. ▸ The naming of spinal nerves is based on the segment
in which they are located.
▸ There are 8 pairs of cervical nerves, 12 pairs of
thoracic nerves (T1–T12), 5 pairs of lumbar nerves
(L1–L5), 5 pairs of sacral nerves (S1–S5), and 1 pair of
coccygeal nerves (Co1).

39. SpinalNerves
Figure 7.22a

40. Anatomy of SpinalNerves
o Spinal nerves divide
soon after leaving the
spinal cord
o Dorsal rami – serve the
skin and muscles of the
posterior trunk
o Ventral rami – forms a
complex of networks
(plexus) for the anterior,
which serve the motor
and sensory needs of
the limbs

41. Examples of Nerve Distribution
Figure 7.23

42. AutonomicNervous System
 The involuntary branch of the nervous
system
 Consists of only motor nerves
 Divided into two divisions
 Sympathetic division – mobilizes the body
Parasympathetic division – allows body to
unwind

43. DifferencesBetween Somaticand Autonomic
Nervous Systems
 Nerves
Somatic – one motor neuron – axons extend all the way
to the skeletal muscle they serve
postganglionic nerves
 Effector organs
Somatic – skeletal muscle
Autonomic – smooth muscle, cardiac muscle, and glands

44. DifferencesBetween Somaticand Autonomic
Nervous Systems
 Neurotransmitters
 Somatic – always use acetylcholine
Autonomic – use acetylcholine, epinephrine, or
norepinephrine

45. Comparison of Somatic and
Autonomic Nervous
Systems

46. Anatomy of the
Parasympathetic Division
 Originates from the brain stem and S2 –S4
 Neurons in the cranial region send axons out in
cranial nerves to the head and neck organs
 They synapse with the second motor neuron in a
terminal ganglion
 Terminal ganglia are at the effector organs
 Always uses acetylcholine as a
neurotransmitter

47. Anatomy of the Sympathetic
Division – thoracolumbar division
 Originates from T1 through L2
 Preganglionic axons leave the cord in the ventral root,
enter the spinal nerve, then pass through a ramus
communications, to enter a sympathetic chain
ganglion at the sympathetic chain (trunk) (near the
spinal cord)
 Short pre-ganglionic neuron and long postganglionic
neuron transmit impulse from CNS to the effector
 Norepinephrine and epinephrine are neurotransmitters
to the effector organs

48. Sympathetic Pathways
Figure 7.26

49. Anatomy of the
Autonomic
Nervous System

50. Autonomic Functioning
 Sympathetic – “fight-or-flight”
Response to unusual stimulus
Takes over to increase activities
Remember as the “E” division =
exercise, excitement, emergency, and
embarrassment

51. Autonomic Functioning
 Parasympathetic – housekeeping
activites
Conserves energy
Maintains daily necessary body functions
Remember as the “D” division - digestion,
defecation, and diuresis

52. Development Aspects of the
Nervous System
 The nervous system is formed during the first
month of embryonic development
 Any maternal infection can have extremely
harmful effects
 The hypothalamus is one of the last areas of
the brain to develop – contains centers for
regulating body temperature

53. Development Aspects of the
Nervous System
 No more neurons are formed after birth, but
growth and maturation continues for several
years largely due to myelination
 The brain reaches maximum weight as a
young adult