1. ANP1106 Anatomy & Physiology II, Part 2 F Feiner, PhD, MD Friday, March 20 Reflex Activity The Autonomic Nervous System. Overview Kaitlyn Weaver and Andrew Poje (2014) Ty Cobb (1914) Posted March 20, 12:30 PM Ty Cobb (1886-1961) /Detroit Tigers

2. o The Reflex Arc o Muscle Spindles and Tendon Organs o Stretch Reflex o Tendon Reflex o Flexor and Crossed Extensor Reflexes o Superficial Reflexes 2  Reflex Activity (Ch 13, pp 513-519) o Comparison of Somatic and Autonomic Nervous Systems o ANS Divisions  Autonomic Nervous System, Overview (Ch 14, pp 524-527) Lecture Content

3. 3 Organization of the Peripheral Nervous System Figure 13.1 [Sensory receptors] [Motor Endings]

4. 4 Peripheral Nervous System PART 4. Reflex Activity

5. 5 The Reflex Arc o Inborn (Intrinsic) Reflex Rapid predictable motor response to a stimulus Unlearned, unpremeditated, involuntary, built in Prevent having to think about maintaining posture, avoiding pain and controlling visceral activities May (eg drop pot of splashed hot water) or may not (eg change in BP) be aware of reflex response  Two Types of Reflexes o Learned (Acquired) Reflex Results from practice/repetition (eg driving a car) o No clear distinction: inborn reflexes can be modified

6. 6 Components of a Reflex Arc o Site of stimulus  1 -  Receptor o Afferent impulse  CNS  2 - Sensory neuron o 1 (monosynaptic-shown) or more (polysynaptic) links between  and   3 - Integration center o Efferent impulse  effector organ  4 - Motor neuron o Muscle fiber/gland cell contracts/secretes  5 -  Effector Figure 13.15

7. One monosynaptic link and one polysynaptic link between sensory neuron  and motor neurons   Knee-Jerk Reflex 7 o Integration center more complex Added component: interneuron in one branch Sensory neuron  branches   Integration center Components of a Reflex Arc

8. 8 Spinal Reflexes  Somatic actions mediated by spinal cord o In fact, continuous facilitating signals from brain required for normal spinal reflexes o Exaggerated, distorted or absent reflexes indicate pathology of specific higher cortical regions (see below) Pull arm away before pain is felt Awareness of surroundings may govern action o No direct involvement of higher brain centres o But, brain “advised” - can facilitate / inhibit / adapt

9. 9 Antagonistic Pairs of Muscles  Flexing / extending of opposing muscles When hamstring contracts, quadriceps relaxes When quadriceps contracts, hamstring relaxes o Hamstring and quadriceps muscles oppose each other, ie are antagonistic: Tendons attach muscle to bone Hamstring (relaxed)

10.  Physiological: reciprocal inhibition insures Figure 13.18a Patellar/Knee-Jerk Stretch Reflex/1 of quads hamstrings reflex muscle contraction 10 o Stand up  Knees begin to buckle constant muscle length  Quads lengthen...

11.  Clinical: Test Sensory & Motor Connections and Spinal reflex muscle contraction Patellar/Knee-Jerk Stretch Reflex/2 Cord Functioning Figure 13.18b 11 o Tapping kneecap (patella) stretches quadriceps...

12. 12 Muscle Spindles and Tendon Organs  Muscle Spindle o Mediates a stretch reflex, a feedback loop that controls rate of muscle lengthening Muscle lengthens: detects change Output to spinal cord, which relays back a signal to o Protective: maintains constant muscle length o Sensory proprioceptor within muscle fiber - measures its length the muscle, causing it to contract (spinal reflex) o Overriding messages from CNS can tell muscle to continue to lengthen Muscle lengthens then contracts Spinal cord Source

13. Muscle Spindles and Tendon Organs  Tendon Organ 13 Spinal cord Source Muscle and tendon lengthen then shorten inside tendon o Sensory proprioceptor within tendon - measures its tension o Mediates a stretch reflex, a feedback loop that controls amount of tension on tendon Muscle lengthens: force transmitted to tendon Output to spinal cord, which relays back a signal to the muscle, causing it to stop lengthening (spinal reflex) detects increase o Shutdown of muscle contraction protective – prevents tendon from being pulled off bone

14. 14 Muscle Spindle  Muscle spindle anatomy: o Capsule Intrafusal (inside) o Sensory Nerves: Anulospiral (I o ) o Motor Nerves: γ Efferent to muscle spindle α Efferent to extrafusal muscle fibers o Muscle fibers: Extrafusal (outside) Flower spray(II o ) Sensory fiber (to tendon organ) Noncontractile Figure 13.16 (See below)

15. 15 Muscle Lengthens / Muscle Spindle Stretched Figure 13.17a

16. 16 Muscle Shortens / Muscle Spindle Slackened Figure 13.17b

17. Tendon Organ / Tendon Reflex  Diametric opposite of the stretch reflex Figure 13.19 17 o Reciprocal activation of antagonist prevents muscles / Report muscle tension tendons from tearing o Also insure smooth onset/termination muscle contract n

18. 18 The Flexor and Crossed-Extensor Reflexes  Flexor (aka Withdrawal) Reflex o eg R arm withdrawn with finger-prick/attacker grab  Crossed-Extensor Reflex o Opposite response on contralateral side to eg push away attacker or maintain balance  Descending signals from brain can override all reflexes

19. Superficial Reflexes  Tests for intact corticospinal tract & cord-level structures o Plantar reflex Draw blunt object upward along lateral aspect plantar surface of foot Abnormal response: Babinski sign. Tows spread apart, big toe upgoing. Sign of an upper motor neuron lesion. Normal in infants normal response is plantar reflex : Normal response: toes remain together and curl downward 19

20. o Abdominal reflex Stroke skin of abdomen towards umbilicus Normal response: umbilicus moves towards stimulus Checks integrity of ventral rami from T 8 to T 12  Tests for intact corticospinal tract & cord-level structures 20 Figure 13.8a Superficial Reflexes  

21. Homeostatic Imbalance  Clinical Importance of Stretch Reflexes nerve damage/ventral horn injury III o syphilis (tabes dorsalis): dorsal horn injurydorsal horn injury eg Chronic diabetes, neurosyphilis, coma o Hypoactive/absent reflexes: peripheral 21 decades after infection, paresthesias (morbid cutaneous sensations/ formication ),ataxia, deafness, visual impairment, dementia [ref]—rarely seen today because of penicillin [ref]

22. 22 o Hyperactive: corticospinal tract lesions reduce reciprocal inhibition eg cerebrovascular accident (‘CVA, stroke’)  Clinical Importance of Stretch Reflexes Homeostatic Imbalance

23. 23 ANS Overview “Exquisitely sensitive to changes in internal environment, balancing competing demands for resources under ever changing conditions”

24. 24 Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) division Motor (efferent) division Somatic nervous system Autonomic nervous System (ANS) Sympathetic division Parasympathetic division Place of ANS in the (Highly Integrated) Nervous System *** *** There are sensory nerves in the ANS!

25. 25 The Autonomic Nervous System  Principle system that stabilizes our internal environment o Motor neurons that innervate smooth/cardiac muscle and glands Respond to sensory signals from visceral (internal) organs o General functions: Ensures optimal support for body activities Shunts blood to ‘needy’ areas Speeds up/slows down heart (  HR,  HR) Blood pressure (BP), body temperature (T)   or   Stomach secretions   or   o Mostly without our awareness, attention or control o Aka involuntary nervous system or general visceral motor system

26. 26 Motor Neurons: Somatic v ANS Figure 14.2 26

27. 27 Motor Neurons: Somatic v ANS

28. 28 ANS DIVISIONS o Rest / Digest: Maintenance: digestion / elimination Minimizes body energy use BP/HR low normal GI actively digesting Pupils constricted /lenses accommodated (close vision)  Parasympathetic Nervous System

29. 29 ANS DIVISIONS Mobilize body during activity o Fight or Flight: HR/BP/respiration rate   Dry mouth Cold/ sweaty skin Dilated pupils Constricts blood vessels: shunts blood to heart/skeletal muscles Provides energy: bronchioles dilate, more glucose from liver  Sympathetic Nervous System

30. 30  Usually, both divisions serve same visceral organ o Parasympathetic: D igestion, D efecation, D iuresis o Sympathetic: E xercise, E xcitement, E mergency o Homeostasis: dynamic antagonism / counterbalancing ANS DIVISIONS

31. 31 Next Lecture – Wed March 25  The Autonomic Nervous System, Part 2: o Anatomy, Physiology, Homeostatic Imbalances (Ch 14, pp 527-539) Mastering A&P Assignment #6 (PNS) will be posted today at ~5 pm and is due by Thursday Mar 26 at 11:59 pm