1

Figure 14.17b

2

Table 14.5

3

Figure 14.18

4

Concept 14.4 Reflexesand SNS Reflex Arcs

5

Reflexes

somatic reflexes involve contraction of skeletal muscles

autonomic reflexes not consciously perceived responses of smooth muscle, cardiac muscle, and

glands reflex arc

pathway followed by nerve impulses that produce reflex

may be monosynaptic or polysynaptic

6

Reflexes fast involuntary, unplanned sequence of

actions that occurs in response to a particular stimulus

some present from birth some are learned or acquired cranial reflex

integration occurs in brain spinal reflex

integration occurs in spinal cord SNS reflexes are always excitatory

7

SNS Reflex Arc Components

1. sensory receptor• dendrite or associated sensory structure

2. sensory neuron• axon and axon terminals

3. integrating center• interneuron(s) that relay impulses

4. motor neuron• impulse triggered by integrating center

5. effector• body part that responds to impulse

8

9

Stretch Reflexes Triggered by tapping on tendons attached to muscles

at elbow, wrist, knee, and ankle joints Monosynaptic

1. muscle spindles detect slight stretch

2. muscle spindle generates impulse(s) to sensory neuron to posterior root of spinal nerve

3. sensory neuron synapses with motor neuron in gray matter of spinal cord

4. strong enough impulse triggers AP of motor neuron

5. ACh at NMJ triggers contraction of skeletal muscle

10

Figure 14.20

11

Stretch Reflexes

Monosynaptic reflexes are called ipsilateral reflexes propagate into and out of the same side of

spinal cord reflex helps prevent injury by preventing

overstretching of muscles reciprocal innervation

polysynaptic reflex arc to antagonistic muscles operates at the same time

three neurons and two synapses

12

Flexor Reflexes

Triggered by painful AKA withdrawal reflex Polysynaptic or intersegmental reflex arc

1. pain-sensitive sensory neuron stimulated2. impulse propagates into spinal cord3. sensory neuron activated interneuron and signal

sent to several segments4. several motor neurons activated and motor

impulse propagates toward several NMJs5. ACh released into synaptic cleft causes flexor

muscles to contract withdrawing body part from painful stimulus

13

Figure 14.21

14

Flexor Reflexes

reciprocal innervation occurs as in stretch reflex

15

Concept 14.5 ANS Reflexes

16

ANS versus SNSSNS produces voluntary movements in response to consciously perceived sensory input

ANS produces involuntary movements in

cardiac muscle smooth muscle glands

in response to unconscious sensory input

17

ANS Reflex Arcs

regulates activity of smooth, cardiac muscle, and many glands

continual flow of nerve impulses from autonomic sensory neurons in visceral organs and blood vessels propagates into integrating centers of CNS

impulses in autonomic motor neurons propagate to various effector tissues

can excite or inhibit activities of effector tissues ANS activity is regulated by hypothalamus and brain stem of

CNS

18

ANS Divisionssympathetic divisionparasympathetic division most organs have dual innervation by both

sympathetic and parasympathetic divisions transmit opposing nerve impulsesenteric division enteric plexuses

network of neurons that extend throughout GI tract walls

contain sensory neurons interneurons motor neurons

19

Figure 14.22a

20

Figure 14.22b

21

Table 14.6

22

Concept 14.6 Anatomy of the ANS

23

Components of ANS

Preganglionic Neurons Autonomic Ganglia Postganglionic Neurons Effectors

24

Preganglionic Neurons

cell body in CNS sympathetic division

in gray matter segments T1-T12, L1 and L2 parasympathetic division

in nuclei of four cranial nerves in brain stem in gray matter segments S2-S4

small-diameter myelinated fiber extends to an autonomic ganglion synapses with postganglionic neuron

25

Figure 14.23

26

Figure 14.24

27

Ganglia Sympathetic ganglia

sympathetic trunk ganglia vertical row on either side of vertebral column

prevertebral ganglia celiac ganglion superior mesenteric ganglion inferior mesenteric ganglion

Parasympathetic ganglia terminal ganglia located close to or actually within wall of visceral organ longer than most axons of sympathetic preganglionic

neurons

28

Figure 14.25

29

Autonomic Plexuses

many lie along major arteries may contain sympathetic ganglia and axons of

autonomic sensory neurons often named after associated artery thoracic plexuses

cardiac plexus pulmonary plexus

abdominal and pelvic plexuses celiac plexus superior and inferior mesenteric plexus hypogastric plexus renal plexus

30

Figure 14.25

31

Postganglionic Neurons

Sympathetic neurons connect with postganglionic neurons by

synapse with first ganglion it reaches may ascent or descent to higher or lower

ganglion before synapsing with postganglionic neurons

without synapsing it may continue through sympathetic trunk ganglion

end at prevertebral ganglion synapse with postganglionic neurons there

32

Figure 14.26

33

Postganglionic NeuronsSympathetic effectors some preganglionic sympathetic axons directly innervate adrenal

medullae each has many axon collaterals single sympathetic preganglionic fiber may synapse with 20 or

more postganglionic neurons example of divergence explains why responses affect almost entire body

simultaneouslyParasympathetic effectors preganglionic neurons pass to terminal ganglia near or within a

visceral effector can be localized to single effector

34

Concept 14.7 ANS Signal Transmission

35

ANS Signal Transmission

Classification based on neurotransmitter released Cholinergenic neurons

release acetylcholine Adrenergenic neurons

release norepinephrine

36

Cholinergenic neurons

release acetylcholine preganglionic

both sympathetic and parasympathetic sympathetic postganglionic that innervate most sweat glands all parasympathetic postganglionic neurons

37

Adrenergenic neurons

release norepinephrine most sympathetic postganglionic neurons

receptors bind both neurotransmitter norepinephrine and hormone epinephrine four classifications

alpha 1, alpha 2, beta 1, and beta 2 alpha 1 and beta 1 are generally excitatory receptors alpha 2 and beta 2 are generally inhibitory receptors

38

Figure 14.27a

39

Figure 14.27b

40

Figure 14.27c

41

Table 14.7

42

Concept 14.8 Sympathetic and Parasympathetic Responses

43

Sympathetic dominates during extreme physical or emotional stress favors activities that can support high production of ATP and high

physical activity fight or flight response

1. pupil dilation

2. increased heart function

3. dilation of airways

4. reduced blood flow to viscera

5. increased blood flow to heart, skeletal muscles, liver and adipose tissue

6. increased glycogen and fatty acid breakdown

7. release of glucose from liver

8. inhibition of processes not essential for emergency response

44

Parasympathetic

enhances rest and digest activities favors activities that can support body functions that conserve and

restore energy during times of rest and recovery SLUDD

salivation lacrimation urination digestion defecation

three decreases heart rate diameter of airways diameter of pupils

45

Table 14.9 pt 1

46

Table 14.9 pt 2

47

Table 14.8

48

Concept 14.9 ANS Reflex Arcs

49

Autonomic Reflexes

Components:1. Receptor2. Sensory neuron3. Integrating center4. Motor Neuron5. Effector

50

Hypothalamus control and integration center of ANS receives sensory input regarding

visceral function olfaction gustation blood, temperature, osmolarity, and substance

concentration emotions from limbic system

output via reticular formation to brain stem spinal cord

posterior and lateral control sympathetic activities anterior and medial control parasympathetic activities

51

End Chapter 14