1. Peripheral Nervous System
Spinal Cord
Reflexes
Peripheral Nervous System

2. Spinal Cord Anatomy
Extends from the foramen magnum of the skull to the first or second lumbar vertebra
Provides a two-way conduction pathway from the brain to and from the brain
31 pairs of spinal nerves arise from the spinal cord
Cauda equina is a collection of spinal nerves at the inferior end

3. Spinal Cord Anatomy

4. Spinal Cord Internal Anatomy

5. Spinal Cord Internal Anatomy

6. Spinal Cord Input/Output

7. Spinal Nerves
31 left-right pairs of spinal nerves emerge from the cord at regular intervals (called segments). Except for the first cervical pair the spinal nerves leave the vertebral column from the intervertebral foramen between adjoining vertebrae – the first pair leaves between the skull and the first cervical vertebrae .
Cervical – 8 pairs, C1-C8
Thoracic – 12 pairs, T1-T12
Lumbar – 5 pairs, L1-L5
Sacral - 5 pairs, S1-S5
Coccygeal – 1 nerve pair

8. Cervical Plexus

9. Brachial Plexus

10. Lumbar Plexus

11. Sacral plexus

12. Dermatomes

13. Sensory and Motor Tracts

14. Reflex Arc

15. Stretch Reflex

16. Tendon Reflex

17. Withdrawal Reflex

18. Crossed Extensor Reflex

19. Peripheral Nervous System (PNS)
somatic (SNS)
sensory
motor
autonomic (ANS)
motor parasympathetic
sympathetic

20. PNS: Autonomic Nervous System
Motor subdivision of the PNS
Consists only of motor nerves
Also known as the involuntary nervous system
Regulates activities of cardiac and smooth muscles and glands
Two subdivisions
Sympathetic division
Parasympathetic division

21. PNS: Differences Between Somatic and Autonomic Nervous Systems
Somatic Nervous System
Autonomic Nervous System
Nerves
One-neuron; it originates in the CNS and axons extend to the skeletal muscles served
Two-neuron system consisting of preganglionic and postganglionic neurons
Effector organ
Skeletal muscle
Smooth muscle, cardiac muscle, glands
Subdivisions
None
Sympathetic and parasympathetic
Neurotransmitter
Acetylcholine
Acetylcholine, epinephrine, norepinephrine

22. PNS: Differences Between Somatic and Autonomic Nervous Systems
Central
nervous system
Peripheral nervous system
Effector organs
Somatic nervous system
Sympathetic
division
Autonomic
nervous
system
Parasympathetic
KEY:
Preganglionic
axons
(sympathetic)
Postganglionic
Myelination
(parasympathetic)
Acetylcholine
Epinephrine and
norepinephrine
Blood
vessel
Adrenal medulla
Ganglion
Norepinephrine
Skeletal
muscle
Smooth muscle
(e.g., in stomach)
Glands
Cardiac

23. PNS: Parasympathetic Division
Preganglionic neurons originate from the craniosacral regions:
The cranial nerves III, VII, IX, and X
S2 through S4 regions of the spinal cord
Due to site of preganglionic neuron origination, the parasympathetic division is also known as the craniosacral division
Terminal ganglia are at the effector organs
Neurotransmitter: acetylcholine

24. PNS: Sympathetic Division
Preganglionic neurons originate from T1 through L2
Ganglia are at the sympathetic trunk (near the spinal cord)
Short pre-ganglionic neuron and long post-ganglionic neuron transmit impulse from CNS to the effector
Neurotransmitters: norepinephrine and epinephrine (effector organs)

25. Parasympathetic
Eye
Salivary
glands
Heart
Lungs
Cervical
Stomach
Thoracic T1
Pancreas
Liver and
gall-
bladder L1
Lumbar
Bladder
Genitals
Pelvic
splanchnic
nerves
Sacral nerves (S2 – S4)
Adrenal
gland
Liver
and gall-
Sympathetic
Skin
Brain stem
Cranial
ganglia

26. PNS: 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
Parasympathetic—“housekeeping” activites
Conserves energy
Maintains daily necessary body functions
Remember as the “D” division
digestion, defecation, and diuresis

27. Peripheral Nervous System
Flow to the CNS
Flow out of the CNS

28. Peripheral Nervous System
Integration occurs at many locations along the pathway.
stimulus - environmental change
sensation - awareness of stimulus
perception - interpretation of the
meaning of the stimulus

29. Sensory Modalities General senses: somatic and visceral Special senses
smell,hearing/equilibrium
taste, vision, and hearing

30. Classification of Sensory Receptors
Structural classification
Type of response to a stimulus
Type of stimuli they detect

31. Structural Classification of Receptors

32. Classification by Location
1. Exteroceptors
2. Interoceptors
3. Proprioceptors

33. Classification by Stimuli Detected
1. Mechanoreceptors
2. Thermoreceptors
3. Photoreceptors
4. Chemoreceptors
Nociceptors
Osmoreceptors

34. Adaptation
Adaptation - generator potential or receptor potential decreases in amplitude during a maintained stimulus.
Rapidly adapting - e.g. pressure, touch, smell
Slowly adapting - e.g. pain, body position

35. Somatic Sensations Tactile Pain Thermal Proprioceptive
touch, pressure,vibration, itch and tickle
Pain
fast and slow
Thermal
warm and cold
Proprioceptive
muscle spindles, tendon organs, joint receptors

36. Sensory Receptors

37. Pain Sensations Nocicceptors = pain receptors
Free nerve endings found in every tissue of body except the brain
Stimulated by excessive distension, muscle spasm & ischemia
Tissue injury releases chemicals such as kinins, or prostaglandins
Little adaptation occurs

38. Types of Pain Fast Pain (acute) Slow Pain (chronic)
occurs rapidly after stimuli (0.1 sec)
sharp pain like needle puncture or cut
not felt in deeper tissues
Slow Pain (chronic)
begins more slowly & increases in intensity
aching or throbbing pain of toothache
in superficial and deep tissues

39. Referred Pain
Visceral pain felt just deep to the skin overlying the stimulated organ or in a surface far from the organ
Skin area & organ are served by same segment of the spinal cord.

40. Pain Relief - Analgesia
Aspirin and ibuprofen block formation of prostaglandins that stimulate nociceptors
Novocaine blocks conduction of nerve impulses along pain fibers
Morphine lessens the perception of pain in the brain

41. Receptors - Summary

42. Stages of Sleep
Nonrapid eye movement (NREM)
Rapid eye movement (REM)

43. Learning and Memory
Learning is the ability to acquire new information or skills through instruction or experience.
Memory is the process by which information acquired through learning is stored and retrieved.
Immediate memory- recall for a few seconds.
Short-term memory- temporary ability to recall.
Long-term memory- more permanent.
Memory consolidation.