Transcript ANPS 019 Beneyto 12-02

Autonomic Nervous System & Hypothalamus
SOMATIC
NERVOUS
SYSTEM
Cell bodies in central
nervous system
Peripheral nervous system
Neurotransmitter Effector
at effector
organs
Effect
Single neuron from CNS to effector organs
ACh
Stimulatory
Heavily myelinated axon
Skeletal muscle
SYMPATHETIC
PARASYMPATHETIC
AUTONOMIC NERVOUS SYSTEM
Two-neuron chain from CNS to effector organs
NE
ACh
Lightly myelinated Ganglion
preganglionic axons
ACh
Unmyelinated
postganglionic axon
Epinephrine and
norepinephrine
Adrenal medulla
Blood vessel
ACh
Lightly myelinated
preganglionic axon
Unmyelinated
Ganglion postganglionic
axon
ACh
Stimulatory
or inhibitory,
depending
on neurotransmitter
and receptors
on effector
Smooth muscle
organs
(e.g., in gut), glands,
cardiac muscle
December 2, 2013
Chapter 13: 508
Chapter 15: 575 - 587
Dr. Diane M. Jaworski
249
• Why do we need somatic and autonomic
nervous systems?
• How do the somatic and autonomic nervous
systems differ?
• How do the sympathetic and parasympathetic
nervous systems differ?
• How does the hypothalamus control
homeostasis?
250
Why do we need somatic and autonomic nervous systems?
The Somatic Nervous System (SNS) operates under conscious control to
promote muscle contraction. Thus, muscles move only when instructed to!
Would you want to constantly have to tell your heart to beat, lungs to breath,
blood vessels to constrict or dilate to maintain blood pressure, sweat glands to
cool you off, plus having to think about your food being moved through your
digestive tract and urine filling your bladder? How would you be able to do
anything else?? What would happen to all these activities if you fell
asleep?????
The Autonomic Nervous System (ANS) operates automatically without
conscious instruction. The ANS modulates visceral effectors in the cardiovascular, respiratory, digestive, urinary, and reproductive systems. These
systems always maintain a basal level of activity. Thus, we need to have one
nervous system division to increase activity (Sympathetic NS) and another
nervous system division to decrease activity (Parasympathetic NS). Both
systems work together to maintain homeostasis.
251
How do the somatic and autonomic nervous systems differ?
Somatic Nervous
System
Conscious cortical control
of motor activity = voluntary
Myelinated innervation of
skeletal muscles by
lower motor neurons (LMN)
Only one synapse – on muscle
Active only when stimulated
Acetylcholine input to target
Output is excitatory
252
© McKinley et al. A & P 2013
Autonomic Terminology
•
Preganglionic neurons - visceral motor neurons located in brainstem and
spinal cord, synapse in autonomic ganglion, use acetylcholine
•
Axons of ganglionic neurons are called postganglionic axons
– Cell body in autonomic ganglia
– innervate visceral effectors:
cardiac muscle
glands
blood vessels
smooth muscle
adipose tissues
253
© McKinley et al. A & P 2013
Autonomic
Nervous
System
Involuntary control of visceral function
Unmyelinated innervation of smooth
and cardiac muscle, glands, and
internal organs
One synapse in PNS within ganglion
One synapse on target
Excitatory and inhibitory modulation
of intrinsic target activity
Utilizes multiple neurotransmitters
and receptors
254
© 2005 Pearson Education
How do the somatic and autonomic nervous systems
differ?
- Conscious control
- One neuron
- One neurotransmitter (ACh)
- Involuntary
- Two neurons
- Two neurotransmitters
(ACh & NE)
- Myelinated axon innervates effector
- Innervate skeletal muscle
- Only active when stimulated
- Unmyelinated axon innervates effector
- Innervates viscera
- Always active, modulate activity 255
Somatic and autonomic nervous systems use different
neurotransmitters
One neurotransmitter, acetylcholine (ACh)
Is always excitatory
Just like the somatic nervous system, the pre-ganglionic neuron in
the CNS releases ACh. The post-ganglionic neuron releases either
ACh or norepinephrine. Depending on the receptor activated, the
effect is excitatory or inhibitory.
256
Sympathetic
versus
Parasympathetic
Nervous System
257
© Purves et al. Neuroscience 2008
Sympathetic = "fight, flight, and stress”
Think “E” - exercise, excitement,
emergency, embarrassment
Readies the body for crisis: increases
alertness & stimulates tissue metabolism
Parasympathetic = "rest and digest”
Think “D” – digestion, defecation
(pooping), diuresis (peeing)
Notice that almost all organs get dual
innervation from both divisions. However,
both divisions do not normally innervate
organs equally. Also, those organs
without dual innervation (e.g., adrenal
medulla, arrector pili muscle, sweat
glands, and most blood vessels receive
only sympathetic innervation) are
regulated by increasing or decreasing the
firing rate of sympathetic innervation.
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© McKinley et al. A & P 2013
Notice that the Sympathetic &
Parasympathetic axons originate
in different regions of the CNS
Sympathetic = thoracolumbar
Parasympathetic = craniosacral
*
Vagus (CN X), which accounts
for 75% of parasympathetic
innervation, originates in the
brainstem, but innervates organs
at all spinal cord levels
No parasympathetic innervation
of cutaneous effectors (blood
vessels, sweat glands, arrector
pili muscles) and blood vessels in
skeletal muscles.
Remember that TWO output neurons
are involved in autonomic reflexes –
one in the CNS and one in the PNS
Let’s see how this organization differs in the Sympathetic & Parasympathetic NS
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Sympathetic Nervous System
Preganglionic
Postganglionic
Eye
Blood vessels and
sweat glands of head
Salivary glands
Blood vessels
Heart
Spinal cord
Right
Left
Cardiac and
pulmonary
plexuses
Superior cervical ganglion
Middle cervical ganglion
Inferior cervical ganglion
Postganglionic axons
to skin, blood vessels
T1
T1 T1
T2
T2
T3
T3
T4
T4
T5
T5
T6
T6
T7
T7
T8
T8
T9
T9
T10
T10
T11
T11
T12
T12
L1
L1
L2
L2 L2
L3
Lung
Celiac ganglion
Greater thoracic
Liver and
splanchnic nerve
gallbladder
Stomach
Spleen
Lesser
thoracic
splanchnic
nerve
Least thoracic
splanchnic
nerve
Adrenal medulla
Kidney
Ureter (proximal)
Pancreas
Superior
mesenteric
ganglion
Inferior
mesenteric
ganglion
Large intestine
Small intestine
Rectum
Ureter (distal)
Lumbar splanchnic
nerves
L4
L5
Hypogastric plexus
Bladder
S1
S2
Sympathetic
trunk ganglia
Ovary
© McKinley et al. A & P 2013
Vas deferens
Seminal vesicle
Sacral
splanchnic
nerves
Prostate
Uterus
Testis
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Sympathetic Division
Preganglionic neurons exit the thoracolumbar spinal cord (T1 to L2) and
synapse on post-ganglionic neurons in the paravertebral ganglia or
sympathetic ganglionic chain located close to the spinal cord. Thus, the
preganglionic axon is very short.
Preganglionic axons are short
Postganglionic axons are very long
© McKinley et al. A & P 2013
261
Sympathetic Division
Preganglionic axons branch to synapse with several postganglionic neurons.
The postganglionic axon then has to travel a long distance to the target
organ. In some cases, the axons travel along the walls of blood vessels to
get to their target.
262
Sympathetic Division
Wow, that’s a pretty complicated system to respond to emergencies!!!
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Sympathetic Division
Some preganglionic fibers synapse in diffuse ganglion (collateral ganglion)
located close to the organs that the postganglionic fibers will innervate (e.g.,
digestive, urinary, reproductive systems).
Other preganglionic fibers
pass through the ganglia
without synapsing.
They terminate directly on
the adrenal medulla &
stimulate the secretion of
epinephrine/adrenaline
(80%) &
norepinephrine/noradrenali
ne (20%).
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Parasympathetic Nervous System
Preganglioni
c
Postganglionic
Ciliary ganglion
Lacrimal gland
Pterygopalatine
ganglion
CN III
CN
VII
CN
IX
Pon
s
Parotid salivary
gland
Submandibular salivary
gland
Sublingual salivary gland
Submandibular
ganglion
Otic ganglion
Hear
t
CN X
Cardiac plexus
Trachea
Pulmonary
plexus
Esophageal plexus
Lung
Esophagus
Liver
Gallbladde
r
Stomach
Abdominal aortic
plexus
Spleen
Spinal
cord
Kidney
Ureter
Pancreas
Small intestine
Hypogastric
plexus
Testis
Ovary
Descending colon
Rectum
S
2
S
3
S
4
Pelvic splanchnic
nerves
Bladder
Penis
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Uterus
Vagina
© McKinley et al. A & P 2013
Parasympathetic Division
Ciliary
ganglion
CN III
Lacrimal
gland
CN VII
Pterygopalatine
ganglion
CN IX
CN X
Referred to as the Craniosacral division:
Stimulates visceral activity, conserves
energy/promotes sedentary activities
Eye
Nasal
mucosa
Submandibular
ganglion
Otic ganglion
Submandibular
and sublingual
glands
Parotid gland
Cranial nerves III (pupil dilation), VII (saliva,
tearing, nasal secretions), IX (saliva), X (saliva)
Heart
Cardiac and
pulmonary
plexuses
Lung
Sacral cord (S2, 3, 4) to innervate bladder,
bowel & reproductive organs
Celiac
plexus
The Vagus nerve provides the major
parasympathetic innervation to the heart, lungs,
esophagus, stomach, pancreas, liver, small
intestine, and upper half of the large intestine.
Liver and
gallbladder
Stomach
Pancreas
S2
Large
intestine
S4
There is no parasympathetic innervation to
limbs, skin or blood vessels.
Small
intestine
Pelvic
splanchnic
nerves
Inferior
hypogastric
plexus
Wow, that was a lot easier than the
Sympathetic Division!!
Rectum
Urinary
bladder
and ureters
Genitalia (penis, clitoris, and vagina)
Preganglionic
Postganglionic
CN
Cranial nerve
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Parasympathetic
Nervous System
Preganglionic neurons located in
brainstem and sacral spinal cord
Preganglionic axons are long since
parasympathetic ganglia are located
close to target organ and branch
very little to give finer control
Postganglionic axons are short
© McKinley et al. A & P 2013
© 2005 Pearson Education
267
ANS Neurotransmitters
• All preganglionic
fibers release ACh
• Parasympathetic:
postganglionic fibers
release ACh
• Most Sympathetic
postganglionic fibers
release
Norepinephrine
(noradenaline)
Exception: sweat glands
release ACh
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© 2005 Pearson Education
Parasympathetic Pathway
Sympathetic Pathways
Preganglionic axon
releases ACh.
Ganglionic neuron
cell body and
dendrites always
contain receptors
for ACh.
ACh
ACh
ACh
Nicotinic
receptors
Nicotinic
receptors
Nicotinic
receptors
ACh
ACh
NE
Postganglionic axon
releases ACh or NE.
Muscarinic
receptors
Target cells contain
either ACh receptors
(bind ACh) or NE
receptors (bind NE).
© McKinley et al. A & P 2013
Target cell
Muscarinic
receptors
Target cell
(e.g., sweat glands
and blood vessels
in skeletal muscle)
Adrenergic
receptors
Target cell
(e.g., most other
body structures)
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All pre-ganglionic CNS neurons
release ACh that binds to nicotinic
ACh receptors
- on muscles (somatic NS)
- in parasympathetic ganglion
- in sympathetic ganglion
- in the adrenal gland
ACh binding to nicotinic receptors
is ALWAYS STIMULATORY!
ANS Neurotransmitter
Receptors
Post-ganglionic parasympathetic
neurons release ACh that binds to
muscarinic ACh receptors on
target tissues (inhibitory or
excitatory)
Post-ganglionic sympathetic
neurons release
norepinephrine/epinephrine that
binds to  &  adrenergic
receptors on target tissues (NE
targets  receptors & epinephrine
targets  receptors). More info in
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What happens to the organs in response to these stimuli?
Sympathetic
Heart rate?
Increase
Parasympathetic
Decrease
Blood pressure?
Decrease
Breathing rate?
Increase
Increase
Decrease
Pupil size?
Gut motility?
Increase
Decrease
Decrease
Increase
Fill in the info above with “increases” or “decreases”
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Drugs of abuse
• Sympathomimetic (mimics the sympathetic NS) : high BP,
tachycardia (speeding heart rate), anxiety, hyperthermia,
pupil dilation, sweating
– Cocaine blocks reuptake of norepi, epi, and dopamine
• Cholinergic (ACh stimulants) – mushrooms (muscarine)
– SLUDGE: Salivate, Lacrimate, Urinate, Defecate,
Emesis (vomiting) and other gastrointestinal effects,
bradycardia (slow heart rate)
• Anticholinergics– many antihistamine drugs, tricyclic
antidepressants
– Hot as a hare
– Blind as a bat
– Dry as a bone
– Red as a beet
– Mad as a hatter
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Enteric Nervous System
• Third division of
Autonomic NS
• Contains same neurotransmitters as found
in the brain
• Allows for complex
visceral reflexes to be
coordinated locally
The enteric nervous system will be
discussed in ANP20 with the digestive system
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Autonomic
Integration
• Medulla Oblongata
– Contains nuclei involved in:
• salivation
• swallowing
• digestive secretions
• peristalsis (visceral movements)
• urinary function
– Regulated by hypothalamus
• Hypothalamus
- Highest command center for
autonomic homeostatic control (other
than the cerebral cortex!)
© McKinley et al. A & P 2013
© 2005 Pearson Education
Cranial
Nerves
Spinal
Nerves
275
Hypothalamus maintains homeostatic
setpoints
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The Hypothalamus is
part of the Diencephalon
• Lies below thalamus
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External Structures of the Hypothalamus
Mamillary bodies:
- process olfactory and other
sensory information
-
control reflexive eating
movements:
In the movie Awakenings the
people who were “frozen” ate
using the reflex centers here
and the swallowing centers in
the medulla
• Infundibulum:
– connects hypothalamus to pituitary
gland
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The Hypothalamus
is made of many small
nuclei (neuron clusters)
Each individual
nucleus has a unique
function
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The hypothalamus regulates the
endocrine system via the pituitary
Hypothalamus makes
Releasing Factors to stimulate
the Pituitary Gland
Pituitary Gland makes
Stimulating Factors to stimulate
glands to make hormones
Endocrinology will be discussed
in greater detail in ANP20
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The Hypothalamus Regulates
Circadian (daily) Rhythms: Sleep
Melatonin maintains sleep
“Biologic
Clock” is the
suprachiasmatic
nucleus
Regulation of
Pineal Gland
(melatonin)
Melatonin is only made at night
You wake up when your melatonin
level drops enough to activate the
reticular activating system 281
The Hypothalamus Regulates
Water Balance
• Regulates kidney function (retain water)
• Supraoptic nucleus secretes antidiuretic hormone
(ADH)
• Damage to supraoptic nucleus results in diabetes
insipidus = pee more + drink more
• “Thirst Center”
– Stimulates drinking behavior
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The Hypothalamus Regulates Food Intake
• “Satiety Center” regulates fullness, suppresses
eating behavior
• “Feeding Center” stimulates food consumption
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Responds to peripheral signals
– Leptin from fat cells - inhibit feeding
– Ghrelin from stomach - stimulate feeding
– Insulin from pancreas - inhibit feeding
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Genetics contribute to Obesity
285
Environmental Factors contribute as well
286
The Hypothalamus Regulates
Body Temperature
• Preoptic area of hypothalamus is the site of the
body’s “thermostat”
• Initiates sweating (to reduce body heat)
• Initiates shivering (to increase body heat)
Thermoregulatory sweating is
regulated by hypothalamus
Emotional sweating is
regulated by the limbic system
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The Hypothalamus
controls the ANS
Hypothalamic neurons send
axons down the brainstem
and spinal cord to synapse
in areas controlling :
Cardiovascular
function
(heart rate, blood pressure)
Respiration
Digestion
Reproductive Activity
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Much more…
The Hypothalamus regulates MANY behaviors
via its interaction with the limbic system
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