the spinal cord and spinal nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · the...

35
Chapter 13 – Spinal Cord and Spinal Nerves 1 Chapter 13 The Spinal Cord and Spinal Nerves 2 SECTION 13-1 The brain and spinal cord make up the central nervous system, and the cranial nerves and spinal nerves constitute the peripheral nervous system

Upload: truongthuy

Post on 07-May-2018

271 views

Category:

Documents


6 download

TRANSCRIPT

Page 1: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

1!

Chapter 13!The Spinal Cord and Spinal Nerves!

2!

SECTION 13-1 !The brain and spinal cord make up the central nervous system, and the cranial nerves and spinal nerves constitute the peripheral nervous system!

Page 2: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

2!

3!

Grouping of Neural Tissues (1 of 3)!White matter!•  Myelinated (and unmyelinated) neuron processes!•  Schwann cells in PNS!•  Oligodendrocytes in CNS!

Gray matter!•  Nerve cell bodies and dendrites!•  Unmyelinated axons!•  Neuroglia (e.g. astrocytes)!

Nerve!•  Bundle of nerve fibers (axons) outside the CNS!•  Has associated CT layers!

4!

Grouping of Neural Tissue (2 of 3)!

Ganglion!•  Collection of nerve cell bodies outside of the

CNS!•  E.g. Dorsal root ganglion!

Nucleus!•  Collection of nerve cell bodies with a

common function found inside the CNS!•  In brain or spinal cord!•  Unmyelinated!•  E.g. Basal nuclei!

Page 3: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

3!

5!

Grouping of Neural Tissue (3 of 3)!

Columns are major regions of cord!•  E.g., posterior columns!

Tracts are bundles of axons with common:!•  Structural characteristics (e.g. axon diameter,

myelinated or not)!•  Function/direction!•  E.g., spinothalamic tract!

Ascending tracts (in cord) = sensory!Descending tracts (in cord) = motor!Horns!•  Major areas of gray matter in spinal cord!

6!

SECTION 13-2 !The spinal cord is surrounded by three meninges and conveys sensory and motor information!

Page 4: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

4!

7!

Gross Anatomy of the Spinal Cord Figure 13-2!

8!

Spinal Cord Functions/Anatomy!

Spinal cord functions:!•  Convey sensory information to brain!•  Convey motor information to PNS!•  Reflexively integrate sensory and motor info!

Gross anatomical features:!Length!•  Extends from medulla to L1−L2 in adults!•  16 to 18 in. long!•  About 0.5 in. diameter!

Page 5: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

5!

9!

Spinal Cord Gross Anatomy (1 of 2)!

Enlargements:!Regions where cord is

thicker!•  Cervical enlargement!

Fibers to and from arms!•  Lumbar enlargement!

Fibers to and from legs!Conus medullaris!•  Tapered end of the

cord!•  About L1 or L2!

E

E E

10!

Spinal Cord Gross Anatomy (2 of 2)!

Filum terminale!•  Fibrous extension of pia mater!•  Forms part of coccygeal ligament!

Coccygeal ligament!•  Dura mater + filum terminale (pia)!•  Attaches conus medullaris to coccyx!

Cauda equina (“horse’s tail”)!•  Nerves arising from lower portion of cord!•  Descend in spinal canal!•  Exit spinal canal as spinal nerves!

Page 6: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

6!

11!

Conus Medullaris, Filum Terminale!

Gray’s anatomy!www.bartleby.com/107/illust661.html!

Conus medullaris!

Filum terminale -!Intradural portion!(pia)!

Filum terminal - !extradural portion!(coccygeal ligament)!1st coccygeal!

vertebra!

Dura mater!

Subarachnoid!space!

2nd sacral vertebra!

1st lumbar!Vertebra!

12!

Spinal Tap, Spinal Nerves!Spinal tap!•  Deliver anesthetics, sample CSF fluid or

pressure, etc.!•  Done between L3 and L4 or L4 and L5!

(Cord not present here)!Spinal nerves contain two roots! Spinal nerves are mixed nerves!•  Ventral root - motor !•  Dorsal root - sensory !•  Dorsal root ganglion!

Sensory cell bodies (unipolar neurons)!

Page 7: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

7!

13!

Gross Anatomy of the Spinal Cord Figure 13-2b!

motor!

sensory!

mixed!

14!

The Spinal Meninges Figure 13-3a!

Page 8: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

8!

15!

Spinal Meninges and Associated Structures!

Continuous with cranial meninges at F. magnum!Functions:!•  Provide support, stability, shock absorption!

!!Epidural space:!•  Between dura mater and walls of vertebral

canal!•  Contains adipose, areolar CT, blood vessels!•  Cushions cord!

16!

Dura Mater!

Dura mater = “tough mother”!•  Not firmly attached to bone (as in cranium)!•  Dense irregular CT!•  Inner lining of simple squamous EPI!•  Tubular portion runs from F. Magnum to S2!

Fuses to form coccygeal ligament (with filum terminale) that extends to coccyx!Fuses with CT coverings of spinal nerves!

Subdural “space”!•  Probably not present in life!

Page 9: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

9!

17!

Arachnoid Membrane!

Arachnoid = “spider-like” = refers to trabeculae!•  Avascular!•  Simple squamous EPI + CT trabeculae!

Collagen + elastin fibers form trabeculae!•  EPI adheres to dura across “subdural space”!•  Extends with dura to end of intradural portion

of filum terminale, so roots of nerves making up the cauda equina are in subarachnoid space!

Subarachnoid space!•  Contains cerebrospinal fluid (CSF)!

18!

Pia Mater!

Pia mater = “soft” or “delicate” mother!•  Adheres to surface of brain and cord!•  Delicate collagen and elastin fibers!•  Highly vascular!•  Runs to coccyx as filum terminale (with dura,

forms coccygeal ligament)!Denticulate (dentate) ligaments (Fig. 13-5)!•  Formed from pia mater!•  Extend through arachnoid to attach to dura!•  Suspend cord within subarachnoid space!

Page 10: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

10!

19!

The Spinal Cord and Spinal Meninges!

Figure 13-3b!

Note orientation compared to that in Figure 13-5!

20!

SECTION 13-3 !Gray matter is the region of integration and command, and white matter carries information from place to place!

Page 11: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

11!

21!

Sectional Organization of Cord Figure 13-5b!

Note orientation compared to that in Figure 13-3!

22!

Internal Anatomy of the Cord!

•  Ventral (anterior) median fissure !(A fissure is larger than a sulcus.)!

•  Dorsal (posterior) median sulcus !(smaller than fissure)!

•  Gray commissures!Commissure = axons crossing from one side of

the body to the other!Gray = gray matter!

•  Central canal!Contains CSF!

Page 12: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

12!

23!

Gray Matter in the Cord see Figure 13-5a!Nuclei - collections of cell bodies with a similar

function!Ventral (anterior) gray horns!•  Somatic motor nuclei!•  Efferent information to skeletal muscles!

Lateral gray horns!•  Visceral (autonomic) motor nuclei!•  Only in thoracic and lumbar segments!

Dorsal (posterior) gray horns !•  Sensory area (next slide and see slide #63)!•  Somatic and autonomic (visceral) nuclei!

24!

Sectional Organization of Cord Figure 13-5a!

Note interneurons in dorsal horns e.g., slide #63!

Page 13: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

13!

25!

White Matter – Columns and Tracts!

Columns:!•  Large collections of fibers conveying

information to or from the brain!•  Have similar origin and similar destinations!

Tracts:!•  Collections of fibers within a column!•  Carry same type of information in the same

direction to the same destination!

26!

Examples of Columns and Tracts!

Posterior columns!•  Sensory (ascending)!

Spinothalamic tracts!•  Sensory (ascending)!

Corticospinal tracts!•  Motor (descending)!•  Voluntary movements!

Vestibulospinal tracts!•  Motor (descending)!•  Automatic (involuntary) movements!

Note that the name usually tells you the direction of information

flow.!

Page 14: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

14!

27!

Sensory Columns and Tracts Figure 15-4!

Note organization and direction. Do not try to memorize locations.!

Posterior column pathway

Spinothalamic pathway

28!

Motor Columns and Tracts Figure 15-8!

Lateral corticospinal tract

Vestobulospinal tract

Anterior corticospinal tract

Note organization and direction. Do not try to memorize locations.!

Page 15: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

15!

29!

SECTION 13-4 !Spinal nerves form plexuses that are named according to their level of emergence from the vertebral canal!

30!

Spinal Nerves!

Spinal nerves are mixed nerves!•  Contain both sensory and motor fibers!

Exist in 31 pairs!Exit vertebral canal via intervertebral foramina!•  Named for where they exit vertebral column!

Cord stops at level of L2!•  Nerves exiting below this level form the cauda

equina!

Page 16: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

16!

31!

Spinal Nerve Categories Figure 13-9!Pairs of spinal nerves:!! 8 cervical !

•  (C1 exits between atlas and occipital bone)!

12 thoracic! 5 lumbar! 5 sacral! 1 coccygeal!31 pairs!

32!

Peripheral Nerve Anatomy Figure 13-6!

Connective tissue coverings!1. Epineurium!•  Surrounds entire nerve!

2. Perineurium!•  Delineates fascicles

(bundles)!3. Endoneurium!•  Surrounds individual

nerve fibers!

Does this terminology seem familiar?!

Page 17: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

17!

33!

Rami (Branches) of Spinal Nerves!

Ramus = “branch”; plural = rami!1. Dorsal ramus!•  Information to and from skin, skeletal muscles

of back•  Somatic and visceral, both motor and sensory!

!2. Ventral ramus!•  Information to and from ventrolateral body

surface, body wall and limbs•  Somatic and visceral, both motor and sensory!•  Form plexuses or thoracic (intercostal) nerves!

34!

Nerve Roots and Rami modified from Fig. 13-3b!

Dorsal!

Ventral!

Dorsal root!Dorsal root

ganglion!

Ventral root! Denticulate ligament!

Sympathetic chain ganglion!

Ventral ramus!

Dorsal ramus!

Rami communicantes!

Page 18: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

18!

35!

Rami Communicantes (much more in Ch. 16)!

3.  Rami communicantes!•  Communicate between ventral rami and

sympathetic ganglia!•  Visceral sensory and visceral motor!•  Information to and from interoceptors, smooth

muscle, visceral organs, glands!3a. White ramus!

•  Myelinated preganglionic fibers!3b. Gray ramus!

•  Unmyelinated postganglionic fibers!Gray and white rami unite at sympathetic ganglia!

•  Form sympathetic nerves!

36!

Thoracic nerves

Thoracic (Intercostal) Nerves!

•  Formed by ventral rami of T2 - T12 spinal nerves!

•  Go directly to innervated structures.!

•  Most axons from these segments do NOT join plexuses!

Page 19: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

19!

37!

Distribution of Sensory Nerve Fibers Fig. 13-8a!

Exteroceptors in skin are:!•  Ambient

temperature!•  Pain!•  Light touch,

pressure!

38!

Distribution of Motor Nerve Fibers Fig. 13-8b!

Page 20: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

20!

39!

Dermatomes Figure 13-7!

Dermatome = specific region of skin innervated by a single pair of spinal nerves.!!!Clinically important for diagnoses of specific neuropathies.!

40!

Nerve Plexuses!

Plexus = “network”!Formed from ventral rami only!•  T2 - T12 do not participate in plexuses!

Plexuses are formed by nerve fibers from different spinal nerves.“During development, small skeletal muscles

innervated by different ventral rami fuse to form larger muscles with compound origins. The anatomical distinctions between the component muscles may disappear, but separate ventral rami continue to control each part of the compound muscle.” p. 439!

Page 21: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

21!

41!

Peripheral Nerves and Nerve Plexuses!

Figure 13-9!

Cervical plexus!Brachial plexus!

Lumbar plexus!

Sacral plexus!

42!

Brachial Plexus – 1 Figure 13-11a!

Page 22: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

22!

43!

The Brachial Plexus – 2 See your copy of Netter!

Netter Plate 416

Pick a ventral ramus and

follow branches to a

B.P. nerve

44!

Brachial Plexus – 3 Figure 13-11b!

Page 23: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

23!

45!

SECTION 13-5!Interneurons are organized into functional groups called neuronal pools!

46!

The Organization of Neuronal Pools!

Figure 13-13!

e.g. Sympathetic

division pathway!

e.g. retina! e.g. reticular activating

system!

Page 24: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

24!

47!

SECTION 13-6 !Reflexes are rapid, automatic responses to stimuli!

Yay, the coolest part of the chapter!!

48!

Spinal Reflexes!

Definition:!•  Unconscious, rapid, stereotyped responses

to a stimulus !•  Involve a reflex arc!

!Advantages of reflexes. Why important?!

1.  Fast response!•  Don’t have to think about it!

2.  Predictable!•  Absence indicates damage to N.S.!

Page 25: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

25!

49!

Reflex Arc – 1!

Spinal cord is the integrating center.!Components of a Reflex Arc:!1. Sensory receptor!•  Responds to stimulus!•  Generates signal to be sent to integrator!

2. Sensory neuron!•  Cell body in dorsal root ganglion!•  Carries info to integrating center!•  Info enters via dorsal root!

50!

Reflex Arc – 2!

3. Integrating center = spinal cord!•  Usually involves interneurons!

Polysynaptic reflex (most reflexes)!•  May not involve interneurons!

Monosynaptic reflex!4. Motor neuron!

•  Transmits impulses to muscle or gland!5. Effector!

•  Muscle or gland that responds to motor neuron!

•  Effects a change in controlled variable!

Page 26: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

26!

51!

Events of a Reflex Arc Figure 13-14a!

52!

Classification of Reflexes Figure 13-15!

Page 27: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

27!

53!

Types of Spinal Reflexes!

“Wiring diagrams”!•  Ipsilateral!•  Contralateral!•  Intersegmental!

Reflex responses initiated by:!1. Changes in muscle length!

•  Stretch reflex - e.g. patellar reflex!

2. Changes in tendon tension!•  Golgi tendon reflex!

3. Pain!•  Flexor reflex, crossed extensor reflex!

54!

1. Muscle Spindle (Stretch) Reflex!

Responds to changes in muscle length•  A.K.A. knee-jerk or patellar reflex!•  A monosynaptic reflex!

Receptor (muscle spindle) located in muscle!Cord sends excitatory message to the muscle

being stretched!•  Adjusts stretch of muscle!•  Adjust muscle tone at rest!•  Prevents overstretch!

Page 28: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

28!

55!

The Patellar (Knee-jerk) Reflex Figure 13-17!

= excitatory synapse!+

+

56!

Muscle Spindles – 1!Intrafusal fibers!•  Specialized muscle cells!•  Surrounded by extrafusal (“normal”)

muscle fibers !•  (Extrafusal fibers innervated by alpha

motor neurons)!•  Innervated by both motor and sensory

neurons!A. Gamma motor neurons (γ motor

neurons)!•  Innervate ends of intrafusal fibers!•  Contraction adjusts sensitivity of

spindle

Page 29: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

29!

57!

Muscle Spindle – Intrafusal Fibers – 2!B.  Sensory innervation of intrafusal fibers!•  Innervate center of intrafusal fibers!

(no actin or myosin here)!•  Synapse in cord with motor neurons that

innervate extrafusal fibers in the same muscle!•  Collaterals inform brain of degree of spindle

stretch!Function to adjust muscle tone!

1.  Stretch → ↑ AP frequency → stimulate extrafusal fibers → ↑ muscle tone!

2.  Compress → ↓ AP frequency → ↓ stimulation of extrafusal fibers → ↓ muscle tone!

58!

Intrafusal Fibers From 7th edition!

Note that gamma afferent fires!to some degree even at normal length.!

*

*

Page 30: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

30!

59!

2. (Golgi) Tendon Reflex!

Function:!•  Senses changes in muscle tension (via tendon

tension)!•  Receptor located in tendon (Golgi tendon

organ)!•  Prevents injury to tendons!•  Ipsilateral reflex!•  Sends inhibitory message to muscle under

tension!

60!

Golgi Tendon Organ!

https://humanphysiology2011.wikispaces.com/11.+Muscule+Physiology!

Page 31: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

31!

61!

3. Flexor Reflex – a.k.a. Withdrawal Reflex!

Characteristics – responds to PAIN1. Polysynaptic!2. Ipsilateral!3. Intersegmental!

•  Synapses occur within multiple cord segments!

•  Activates several muscle groups!(i.e. stimulates more than one effector)!

4.  Reciprocal innervation!(i.e. flexors and extensors)!

62!

Flexor Reflex – a.k.a. Withdrawal Reflex – 2!

Mechanism:!1.  Stimulate pain-sensitive sensory neuron!2.  Message sent to cord!3.  Activate interneurons!4.  Relay to several segments!5.  Several flexors activated, extensors inhibited!

Page 32: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

32!

63!

Flexor Reflex – 3 Figure 13-14!

Be able to draw this! !See study guide.!

++

+

_

indicates excitatory synapse indicates inhibitory synapse+_

Back to #23!

64!

Study Guide – Flexor (withdrawal) reflex!Winter 2017

Study Guide and Potential Essay questions for Chapter 13 – Spinal Cord and Spinal Nerves Unless a question asks only for a list or a diagram, answer all questions in complete sentences. Part of your grade depends upon your ability to communicate your ideas in a lucid manner.

1. Clearly diagram the structure and function of a Flexor (Withdrawal) Reflex. Include ALL diagrammatic information shown in Figure 13-14 AND label your diagram with the following

ADDITIONAL terms:

*** This question will be on the exam that covers the part of Chapter 13 about reflexes. *** Anterior and posterior sides of spinal cord motor neuron cell bodies (label both) axon collaterals to other segments of spinal cord pain receptor dorsal horn sensory neuron cell body dorsal root white matter dorsal root ganglion ventral horn gray matter ventral root interneuron cell bodies (label both) arrow(s) indicating info flow in reflex arc • Use an arrow or arrows to indicate the flow of information through this reflex arc. Label your arrow.

• Use appropriate symbols to label all synapses as excitatory ( + ) or inhibitory ( - ).

• CLEARLY indicate all synapses involved like this: o------------< o----------< (CLEAR labeling is a major part of this.) • Because you are adding information to the figure, you will need to construct your own key. You

may use the one in the text as a backbone (pun intended) for your key. Be sure to define any abbreviations that you use and remember that I want you to label the synapses.

• Please note: You will not be graded on the beauty of your artwork, only for the clarity of your

diagram. I don’t care if you can draw a frying pan or a human hand. Your goal is to show me that you understand the flexor reflex.

• Final note: While you may add color to enhance your diagram if you wish, DO NOT rely on color to

differentiate between cell types. A black and white photocopy of your diagram should be as easy to read as a color version. You are being graded on clarity, not beauty. Pretty colors will not earn you points; relying solely on color will cost you points.

Terms Be familiar with the bold face terms in the parts of the chapter that we covered. Be able to define and describe the physiological significance of: afferent and efferent neurons, alpha motor neurons, arachnoid (membrane), ascending tract, cauda equina, central canal, cervical enlargement, columns (white matter), commissure, contralateral reflex,

Page 33: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

33!

65!

Crossed Extensor Reflex!

Characteristics:!1. Polysynaptic!2. Contralateral!3. Reciprocal innervation!

•  Activates flexors on one side! Inhibits extensors on this side!•  Activates extensors on the other side! Inhibits flexors on this side!

4. Intersegmental!

66!

Crossed Extensor Reflex – 2 Figure 13-18!

Mechanism:!1.  Pain!2.  Sensory info to cord!3.  Contract flexors on

one side, extensors on other side!!

+ - -+

+ +

Page 34: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

34!

67!

Flexor and Crossed Extensor Reflexes!

Comparison Figures 13-19, -20 from 9th edition!

68!

SECTION 13-8 !The brain can affect spinal cord-based reflexes!

Page 35: The Spinal Cord and Spinal Nerves - rnrausch.comrnrausch.com/25x/pdf/252/chapter_13_2x.pdf · The Spinal Cord and Spinal Nerves! 2! ... • In brain or spinal cord! ... Spinal Cord

Chapter 13 – Spinal Cord and Spinal Nerves!

35!

69!

Integration and Control of Spinal Reflexes!

Higher centers can modify spinal reflexes!•  Inhibit or facilitate reflex patterns!

Continuous inputs (IPSP, EPSP) to neurons !involved in reflexes!

•  Allows a few neurons from brain to control complex motor functions!

e.g. Walking, running based on spinal reflexes! Modified by higher centers!

Example: decerebrate cat!