2. The Nervous System Two Parts: Central Peripheral Brain and spinal cord
Nerves

3. General Functions Detect internal and external changes
Collect sensory information and make decisions that motor functions carry out
Respond to external/internal stimuli

4. Neuron Structure A Neuron includes:
Cell body
Dendtrites
Axon
Dendrites and the cell body provide receptor surfaces.
A single axon arises from the cell body and may be enclosed in a myelin sheath and a neurilemma.

5. Neuron Structure Schwann Cells
Wind tightly around axons; made up of myelin
Nodes of Ranvier
Gaps between schwann cells

6. Function of Neurons
Sensory (afferent neurons) = carry nerve impulses from peripheral body parts to brain or spinal cord
Interneurons = lie within brain or spinal cord; direct incoming sensory info to appropriate parts for processing and interpretation
Motor (efferent neurons) = multipolar and carry nerve impulses out of brain or spinal cord to effectors; contract muscles, secrete hormones, etc

7. Nerve Impulse
Unmyelinated fibers conduct impulses over their entire surfaces.
Myelinated fibers conduct impulses more rapidly.
Nerves with larger diameters conduct faster than those with smaller diameters.

8. Neuroglial Cells Fill spaces Support neurons
Provide structural framework
Produce myelin
Carry on phagocytosis.

9. Types of Neuroglial Cells
Microglial cells
Support neurons and phagocytize bacterial cells and cellular debris
Oligodendrocytes
Form myelin within the brain and spinal cord

10. Types of Neuroglial Cells
Astrocytes = found between neurons and blood vessels; help regulate concentrations of nutrients and ions within tissue
Ependymal cells = cover specialized brain parts (choroids plexuses) and form inner linings that enclose spaces within the brain (ventricles) and spinal cord (central canal)

11. The Synapse A junction between two neurons
Impulse passes junction via neurotransmitters

12. Synaptic Transmission
Impulses usually travel from a dendrite to a cell body, then along the axon to a synapse.
Axons have synaptic knobs at their distal ends, which secrete neurotransmitters

13. Neurotransmitters
After being released, neurotransmitters are decomposed or removed from synaptic clefts.

14. Types of Nerves Nerves are cord-like bundles of neurons and neuroglia
Nerves can be classified as:
Sensory nerves = carry impulses to brain or spinal cord
Motor nerves = carry impulses to muscles or glands

15. Meninges Bone and meninges surround the brain and spinal cord.
Consist of the dura mater, arachnoid mater, and pia mater

16. Meninges Dura Mater outermost layer
white fibrous connective tissue and blood vessels
surrounds the spinal cord and brain

17. Meninges Arachnoid Mater Middle layer
Thin, weblike membrane that lacks blood vessels

18. Meninges Pia Mater Thin
Contains many nerves and vessels that nourish underlying cells of brain and spinal cord

19. Cerebrospinal Fluid
Occupies the space between the arachnoid and pia maters.
Sub-Arachnoid Space

20. Spinal Cord Structure
Composed of 31 segments, each of which gives rise to a pair of spinal nerves
Has a cervical enlargement and a lumbar enlargement.
Cervical = supplies nerves to upper limbs
Lumbar = supplies nerves to lower limbs

21. Spinal Cord Structure Two Grooves Anterior median fissure (deep)
Posterior median sulcus (shallow)

22. Functions of Spinal Cord
Provides two-way communication system between the brain and other body parts.
Ascending tracts carry sensory impulses to the brain.
Descending tracts carry motor impulses to muscles and glands.

23. The Brain The brain is subdivided into the: Cerebrum Cerebellum
Brain Stem

24. Structure of the Cerebrum
Two Hemispheres
Connected by Corpus Callosum
Deep bridge of nerve fibers

25. Structure of the Cerebrum
Cerebrum Surface:
Convolutions (gyri) = ridges on brain
Sulcus = shallow groove
Fissure = deep groove

26. Structure of the Cerebrum
Cerebral Cortex
Thin layer of gray matter near the surface.
Covers convolutions and dips into sulci and fissures
Contains nearly 75% of all neuron cell bodies in the nervous system

27. Structure of the Cerebrum
White Matter
Interneurons
Located underneath cerebral cortex
Makes up bulk of cerebrum

28. Structure of the Cerebrum
4 Lobes
Frontal
Parietal
Temporal
Occipital

29. Functions of Cerebrum Provides higher brain functions Motor Functions:
control movements
Sensory Functions:
interpret impulses that arrive from sensory receptors, producing feelings or sensations
Association Functions:
analyze and interpret sensory experiences and oversee memory, reasoning, verbalizing, judgement, and emotion

30. Association Areas of Cerebrum

31. Ventricles and Cerebrospinal Fluid
Ventricles are interconnected cavities within the cerebral hemispheres and brain stem.
Choroid plexuses in walls of ventricles secrete cerebrospinal fluid

32. Diencephalon A group of structures that include the following:
Thalamus, Hypothalamus, Pituitary Gland, Pineal Gland, and Optic Tract
Make up Limbic System
Produces emotions and modifies behavior

33. Diencephalon Structure
Thalamus
Central relay station for incoming sensory impulses
Channels impulses to appropriate regions of the cortex for interpretation

34. Diencephalon Structure
Hypothalamus
Maintains homeostasis
Regulates
heart rate
body temp
water/electrolyte balance
controls hunger/body weight
sleep
hormone secretion

35. Diencephalon Structure
Pituitary Gland
Master Gland
All the other endocrine glands depend on its secretions for stimulation
Pineal Gland
Controls circadian rhythm

36. Diencephalon Structure
Optic Tract
Includes optic nerves and optic chiasma (where nerve fibers cross over)
Infundibulum
Behind optic chiasma to which pituitary gland is attached

37. Brain Stem
Made up of 3 Parts:
Midbrain
Pons
Medulla Oblongata

38. Brain Stem Structure Midbrain Pons
Reflex centers associated with eye and head movements
Pons
Help regulate breathing

39. Brain Stem Structure Medulla Oblongata
Transmits all ascending and descending impulses
Signal cross over here

40. Brain Stem Structure Medulla Oblongata Visceral Control
Cardiac center – alter heart rate
Vasomotor center – controls constriction and dilation of blood vessels
Respiratory center – acts with pons to regulate breathing

41. Cerebellum Two hemispheres Functions
Coordination of skeletal muscle movements
Maintenance of equilibrium

42. Peripheral Nervous System
Nerves that branch out from the CNS and connect it to other body parts.

43. Peripheral Nervous System
Two Parts:
Somatic = cranial, spinal nerves that connect CNS to skin and skeletal muscle; oversees conscious activities
Autonomic = connect CNS to viscera (organs) controls unconscious activities

44. Somatic Nervous System
Cranial Nerves
12 pairs of nerves that emanate from the nervous tissue of the brain.  
Exit/enter the cranium through openings in the skull.

45. Somatic Nervous System
Numbers of Spinal Nerves
8 pair of Cervical
12 pair of Thoracic
5 pair of Lumbar
5 pair of Sacral
1 pair of Coccyx

46. Somatic Nervous System
Spinal Nerves
Originate from spinal cord
Mixed nerves that provide 2-way communication between spinal cord and upper and lower limbs, neck, and trunk

47. Spinal Nerves Two Parts: Dorsal Root Ventral Root
Sensory (afferent root of spinal nerve)
Ventral Root
Motor (efferent root of spinal nerve)

48. Spinal Nerves
The lumbar, sacral, and coccyx nerves descend beyond the end of the cord, forming a structure called the Cauda Equina which means horse’s tail.

49. Autonomic Nervous System
Functions without conscious effort
Regulates the visceral activities that maintain homeostasis

50. Autonomic Nervous System
Two Divisions:
Parasympathetic
respond to ordinary conditions
Sympathetic
responds to stressful
and emergency conditions