1. CENTRAL & PERIPHERAL NERVOUS SYSTEMS

2. Structural Divisions of Nervous System
Central Nervous System (CNS)
Brain, Spinal Cord
Peripheral Nervous System (PNS)
Cranial Nerves
Spinal Nerves

3. CNS – Brain Four Major Brain Regions: Cerebrum Diencephalon Brainstem
Cerebellum

4. CNS – Cerebrum Cerebrum Largest, Superior Two Hemispheres
Separated By Longitudinal Fissure
Connected by Corpus Callosum (myelinated axons)
Two Layers: Outer Cortex (gray matter) &
Inner White matter

6. Cerebrum continued Cerebral Cortex
Neuron Cell Bodies & Unmyelinated processes
Gyri (ridges) & Sulci (grooves)
White Matter (Myelinated axons)
Nuclei (gray matter imbedded in white)
Neurons in CNS are MULTIPOLAR; each has tens of thousands of dendrites. Each Neuron makes anywhere from 1,000 to 10,000 synapses with other neurons. A sand grain sized piece of gray matter contains 100,000 neurons & 1 billion synapses!
Spontaneous smiles produced by basal nuclei. Forced smiles are produced by (motor) cortex which controls voluntary, skilled movements. Smiling requires very complex sequence of movements & involuntary control by basal ganglia results in better smile.
The cerebral cortex is 6 layers of cells thick.

7. Basal Nuclei – 4 masses of gray matter with complex functions (in movement).

8. Lobes of Cerebrum Each Cerebral Hemisphere has 5 Lobes:
Frontal – Personality, concentration, problem solving, voluntary control of skeletal muscle
Parietal – Skin sensation, speech & language, expression of thought
Temporal – Hearing, smell
Occipital – Vision
Insula – Bodily self-awareness; sense of disgust to smells, contamination, mutilation
Insula: not well understood; some language function (rhyme recognition, sound sequences), upset stomach, full bladder, behavioral influences on cardiovascular (heart briefly stops when startled)

11. CNS - Diencephalon Diencephalon Enclosed by Cerebrum
Between Cerebrum & Brainstem
Epithalamus
Thalamus
Hypothalamus

12. Diencephalon: Epithalamus
Superior to Thalamus & Third Ventricle
Contains the Pineal Gland, Produces Hormones
Habenular nuclei located here involved in emotional responses to odors

13. Diencephalon: Thalamus
“Relay station” for all sensory impulses to cerebral cortex
Consists of 2 lobes (may be joined by “Intermediate Mass” (a bridge of gray matter)
Third ventricle is superior & medial to thalamus
Thalamus sensory information passes to sensory cortex; only a small portion allowed to pass on.
Intermediate mass contains no fibers; is a projection of gray matter. In 30% of people, the 2 intermediate masses do not join.
Mammillary bodies process sensory info including olfactory sensations. Also nuclei involved in eating, chewing, licking, swallowing.

14. Basal Nuclei – 4 masses of gray matter with complex functions (in movement).

15. Diencephalon: Hypothalamus
Below thalamus
Controls pituitary function
Controls regulatory functions
Helps regulate body temperature
Feeding/Thirst
Body temp is regulated by adjusting blood flow & sweat gland activity

17. CNS - Brain Stem Between Diencephalon & Spinal Cord Three parts:
Midbrain
Colliculi – visual & auditory nuclei
Pons – Below midbrain; joins cerebellum to brainstem
Medulla Oblongata – Below Pons, Regulates heartbeat & breathing; has role in consciousness; joins brain & spinal cord
Midbrain directs reflexive responses to visual & auditory stimuli (coordinates head, eyes, & trunk movements). Also helps maintain consciousness.
Pons – tracts & relay centers joining cerebellum to brainstem. Also nuclei involved in somatic & visceral motor control.
Medulla – relays sensory info to thalamus & other parts of brainstem. Also contains major centers that regulate autonomic function (i.e. Heart rate, BP & digestion), and reflexes (vomiting, swallowing, sneezing, coughing, hiccupping).

20. CNS - Cerebellum Inferior to Cerebrum, Posterior to Brain Stem
Joined to brainstem by Pons
Two hemispheres with convoluted surfaces
Outer Gray Matter
Arbor Vitae (Inner, Branching White Matter)
Provides involuntary coordination of body movements
Automatic processing center.
2 primary functions: adjusts postural muscles of the body & programs & fine-tunes movements controlled at conscious & subconscious levels (compares motor commands with your sense of body position and makes any adjustments necessary to make movements smooth).

21. We really don’t know how the brain translates patterns of nerve activity into conscious experience (e.g. pain, pleasure or color)

22. Protection of the CNS CNS Protected by: Bone Skull (Brain)
Vertebrae (Spinal Cord)
Meninges (C.T. membranes)
Cerebrospinal Fluid (CSF)
Blood-Brain barrier (harmful substances in blood)

23. CNS – Meninges Meninges - CT Membranes between Bone & CNS Dura Mater
Outer, Tough, Fibrous, Double
Extends down vertebral cavity, beyond end spinal cord
Dural Sinuses – Veins between layers
Dural Folds – Innermost layer extents into fissures
Epidural Space – Between walls of vertebral cavity & Dura of spinal cord

25. CNS – Meninges Arachnoid Mater Thin, Spidery, Middle
Extends past spinal cord
Subdural Space – Between Dura & Arachnoid
Subarachnoid Space – Between Arachnoid & Pia; Contains CSF
Pia Mater
Innermost, Delicate
Attached to Surface of Brain & Spinal Cord
Highly Vascular

29. CNS - Brain Ventricles Ventricles
Cavities within Brain, Filled with CSF
Continuous with Subarachnoid Space & Central Canal of Spinal Cord
Lateral – Largest Two, within Cerebral Hemispheres
Third – Narrow, Midline, Diencephalon
Fourth – Brain Stem, Continuous with Central Canal of Spinal Cord

30. Fig. 8.36

31. CNS - Cerebrospinal Fluid (CSF)
Secreted by Choroid Plexuses (capillaries & ependymal cells in ventricles)
Clear, Similar to Blood Plasma
Most CSF produced by Lateral Ventricles
Circulates through Ventricles, Subarachnoid Space, Central Canal
Supports, Absorbs Shocks, Provides Nutrients
Sample via Spinal Tap (Subarachnoid Space, L-4)
CSF produced at a rate of about 500ml/day.

33. Spinal Tap

34. CNS – Spinal Cord Protected by Bone, Meninges, CSF Vertebral Cavity
Extends from Medulla Oblongata (Through Foramen Magnum) to L2
16-18 inches
Two Enlargements (Limb Control):
Cervical (Shoulder & Arms)
Lumbar (Pelvis & Legs)
The lumbar enlargement is also called the lumbosacral enlargement.

36. CNS – Spinal Cord continued
Outer White Matter – Bundles of Myelinated Axons
Ascending Tracts or Pathways
Sensory
Descending Tracts or Pathways
Motor

37. CNS – Spinal Cord continued
Inner Gray Matter
Neuron Cell Bodies (somas) & unmyelinated processes
Dorsal Gray Horn – Interneuron Somas
Ventral Gray Horn – Somas of Motor Neurons
Central Canal in Gray Commissure
Lateral gray horns contain cell bodies of motor neurons of the ANS

39. Peripheral Nervous System - PNS
Consists of:
Peripheral Nerves:
Cranial Nerves
Spinal Nerves & Nerve Plexuses
Ganglia
Sensory Receptors
Carries Sensory Information & Motor Commands

40. PNS – Nerves Bundles of Axons Sensory, Motor or Mixed CT Reinforced
Endoneurium – Surrounds each axon
Perineurium – Around each fascicle (group of axons)
Epineurium – Tough, Fibrous C.T. around Nerve
Entire nerves are either sensory, motor, or mixed in function; the individual neurons within the nerve determine the overall function of the nerve. Each neuron can transmit in only one direction (i.e afferently or efferently).

41. PNS – Cranial Nerves
Twelve Pairs
Function:
Sensory
Motor
Mixed

42. PNS – Spinal Nerves 31 Pairs: 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral
1 Coccygeal
All are Mixed; both Sensory (Afferent) & Motor (Efferent)
Attach to Spinal Cord by Ventral & Dorsal Root

43. Fig. 8.21

45. Reflex Arcs Simple Pathway May not involve brain Results in Reflex
Fast, Predictable
Automatic motor response
Five Components:
Receptor
End of dendrite of sensory neuron (or more complex)
Responds to specific stimuli
Sensory Neuron (Receptor to CNS)

46. Reflex Arcs continued Interneuron CNS Gray Matter
Usually one but may be 0 or >1
Transmits, Inhibits, or Reroutes to Motor Neuron
Motor Neuron (CNS to Effector)
Effector
Muscle or Gland; responds to motor impulse
Response is Reflex (e.g. knee jerk, secretion of digestive juices, pain withdrawl)

48. Types of Reflexes Somatic reflexes: Involuntary (Autonomic) reflexes:
Skeletal muscle
Involuntary (Autonomic) reflexes:
Smooth muscle
Heart and blood pressure
Glandular secretion
Digestive system regulation