Transcript Figure 14.17b

Figure 14.17b
1
Table 14.5
2
Figure 14.18
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Concept 14.4
Reflexes
and
SNS Reflex Arcs
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Reflexes

somatic reflexes involve contraction of skeletal
muscles
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
autonomic reflexes

not consciously perceived

responses of smooth muscle, cardiac muscle, and
glands
reflex arc

pathway followed by nerve impulses that produce
reflex
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may be monosynaptic or polysynaptic
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Reflexes

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
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
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SNS Reflex Arc Components
sensory receptor
1.
•
dendrite or associated sensory structure
sensory neuron
2.
•
axon and axon terminals
integrating center
3.
•
interneuron(s) that relay impulses
motor neuron
4.
•
5.
•
impulse triggered by integrating center
effector
body part that responds to impulse
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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
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Figure 14.20
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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
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Flexor Reflexes

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Triggered by painful AKA withdrawal reflex
Polysynaptic or intersegmental reflex arc
1.
pain-sensitive sensory neuron stimulated
2.
impulse propagates into spinal cord
3.
sensory neuron activated interneuron and signal
sent to several segments
4.
several motor neurons activated and motor
impulse propagates toward several NMJs
5.
ACh released into synaptic cleft causes flexor
muscles to contract withdrawing body part from
painful stimulus
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Figure 14.21
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Flexor Reflexes

reciprocal innervation occurs as in stretch reflex
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Concept 14.5
ANS Reflexes
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ANS versus SNS
SNS
produces voluntary movements
in response to consciously perceived sensory input


ANS
produces involuntary movements in



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
cardiac muscle
smooth muscle
glands
in response to unconscious sensory input
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ANS Reflex Arcs
regulates activity of smooth, cardiac muscle, and
many glands




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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
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ANS Divisions
sympathetic division
parasympathetic division

most organs have dual innervation by both
sympathetic and parasympathetic divisions

transmit opposing nerve impulses
enteric division

enteric plexuses

network of neurons that extend throughout GI tract
walls

contain

sensory neurons
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interneurons

motor neurons
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Figure 14.22a
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Figure 14.22b
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Table 14.6
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Concept 14.6
Anatomy of the ANS
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Components of ANS

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Preganglionic Neurons
Autonomic Ganglia
Postganglionic Neurons
Effectors
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Preganglionic Neurons
cell body in CNS

sympathetic division
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
parasympathetic division
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in gray matter segments T1-T12, L1 and L2
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
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Figure 14.23
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Figure 14.24
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Ganglia


Sympathetic ganglia
sympathetic trunk ganglia
vertical row on either side of vertebral column
prevertebral ganglia
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celiac ganglion
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superior mesenteric ganglion
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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
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




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Figure 14.25
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Autonomic Plexuses
many lie along major arteries
may contain sympathetic ganglia and axons of
autonomic sensory neurons
often named after associated artery
thoracic plexuses
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cardiac plexus
pulmonary plexus
abdominal and pelvic plexuses
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celiac plexus
superior and inferior mesenteric plexus
hypogastric plexus
renal plexus
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Figure 14.25
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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




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end at prevertebral ganglion
synapse with postganglionic neurons there
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Figure 14.26
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Postganglionic Neurons
Sympathetic 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
simultaneously
Parasympathetic effectors

preganglionic neurons pass to terminal ganglia near or within a
visceral effector

can be localized to single effector

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Concept 14.7
ANS Signal Transmission
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ANS Signal Transmission
Classification based on neurotransmitter released

Cholinergenic neurons
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release acetylcholine
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Adrenergenic neurons
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release norepinephrine
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Cholinergenic neurons
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release acetylcholine
preganglionic
both sympathetic and parasympathetic
sympathetic postganglionic that innervate most sweat glands
all parasympathetic postganglionic neurons
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Adrenergenic neurons
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
release norepinephrine
most sympathetic postganglionic neurons
receptors
bind both neurotransmitter norepinephrine and hormone epinephrine
four classifications
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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
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Figure 14.27a
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Figure 14.27b
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Figure 14.27c
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Table 14.7
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Concept 14.8
Sympathetic and
Parasympathetic Responses
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Sympathetic



1.
2.
3.
4.
5.
6.
7.
8.
dominates during extreme physical or emotional stress
favors activities that can support high production of ATP and high
physical activity
fight or flight response
pupil dilation
increased heart function
dilation of airways
reduced blood flow to viscera
increased blood flow to heart, skeletal muscles, liver and
adipose tissue
increased glycogen and fatty acid breakdown
release of glucose from liver
inhibition of processes not essential for emergency response
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Parasympathetic
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

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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
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Table 14.9 pt 1
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Table 14.9 pt 2
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Table 14.8
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Concept 14.9
ANS Reflex Arcs
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Autonomic Reflexes
Components:
1.
2.
3.
4.
5.
Receptor
Sensory neuron
Integrating center
Motor Neuron
Effector
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Hypothalamus

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control and integration center of ANS
receives sensory input regarding

visceral function

olfaction
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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
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End Chapter 14
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