Transcript Nerves

PERIPHERAL & AUTONOMIC
NERVOUS SYSTEMS
Leonardo Da Vinci, The Battle of Anghiari
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
The Peripheral Nervous System
• The PNS
– Is the nervous system outside the brain & spinal cord
– Provides vital links to the body & outside world
– Nerves allow the CNS to receive info & initiate action
• Sensory inputs & motor outputs
– Categorized as
• Somatic or visceral
• General or special
Functional Organization of the PNS
Central nervous system (CNS)
Peripheral nervous system (PNS)
Sensory (afferent) division
Somatic sensory
General: Touch, pain,
pressure, vibration,
temperature, and
proprioception in
skin, body wall, and
limbs
Visceral sensory
General: Stretch,
pain, temperature,
chemical changes,
and irritation in
viscera; nausea and
hunger
Special: Hearing,
equilibrium, vision
Special: Taste, smell
Motor (efferent) division
Somatic nervous
system
Motor innervation of
all skeletal muscles
Sympathetic
division
Autonomic
nervous system
(ANS)
Motor innervation
of smooth muscle,
cardiac muscle,
and glands
Parasympathetic
division
Basic Structural Components of PNS
• Sensory receptors  pick up stimuli from
inside or outside body (we’ll cover later)
• Nerves & ganglia
– Nerves  bundles of peripheral axons
– Ganglia  clusters of peripheral neuronal cell
bodies
• Motor endings  axon terminals of motor neurons
– Innervate effectors (muscle fibers & glands)
The Cranial Nerves – Yes you
have to know them…
• Attach to brain & pass through foramina of
the skull
• Numbered I–XII (1-12)
• Cranial nerves I & II attach to the forebrain
– All others attach to brain stem
• Primarily serve head & neck structures
– The vagus nerve (X) is the only cranial nerve
that extends into abdomen
The Cranial Nerves
Filaments of
olfactory nerve (I)
Frontal lobe
Olfactory bulb
Olfactory tract
Optic nerve (II)
Optic chiasma
Optic tract
Oculomotor (III)
Trochlear (IV)
Temporal lobe
Infundibulum
Facial (VII)
Trigeminal (V)
Vestibulocochlear (VIII)
Abducens (VI)
Glossopharyngeal (IX)
Cerebellum
Medulla oblongata
Vagus (X)
Accessory (XI)
Hypoglossal (XII)
The Cranial Nerves
Cranial nerves
Sensory function
Somatic
sensory
(SS)
Somatic
motor
(SM)
Visceral motor:
parasympathetic
(VM)
III Oculomotor
SM
VM
IV Trochlear
SM
I Olfactory
II Optic
V Trigeminal
VI Abducens
Visceral
sensory
(VS)
Motor function
Smell
Vision
General
SM
SM
Odessa
Ofelia
O’Conner
Takes
Tests
Amazingly!
The Cranial Nerves
Cranial nerves
VII Facial
VIII Vestibulocochlear
IX Glossopharyngeal
X Vagus
Sensory function
Motor function
Somatic
sensory
(SS)
Visceral
sensory
(VS)
Somatic
motor
(SM)
Visceral motor:
parasympathetic
(VM)
General
General;
taste
SM
VM
Hearing;
equilibrium
General
General
Some
General;
taste
General;
taste
SM
VM
SM
VM
XI Accessory
SM
XII Hypoglossal
SM
Fiesty
Victor
Gets
Very
Agitated
Here…
I ) Olfactory Nerves
• Sensory nerves of smell
II) The Optic Nerves
• Sensory nerve of vision
III) The Oculomotor Nerves
• Innervates 4 extrinsic eye muscles
Table 14.2 (3 of 12)
IV) The Trochlear Nerves
• Innervates the superior oblique muscle (an
extrinsic eye muscle)
The Trigeminal Nerves
• Largest of the cranial nerves
– Has 3 divisions
• Ophthalmic
• Maxillary
• Mandibular
• Cell bodies of sensory neurons located in
the trigeminal ganglion
• Mandibular division contains motor fibers
that innervate the chewing muscles
V) The Trigeminal Nerves
VI) The Abducens Nerves
• Abducts the eyeball  innervates lateral rectus
muscle
VII) The Facial Nerves
• Innervates muscles of facial expression
VIII) The Vestibulocochlear Nerves
• Sensory nerve of hearing & balance
IX) The Glossopharyngeal Nerves
• Innervates structures of the tongue & pharynx
X) The Vagus Nerves
• A mixed sensory
& motor nerve
– “Wanders” into
thorax & abdomen
– Parasympathetic
innervation of
organs
XI) The Accessory Nerves
•
•
•
Unique among cranial nerves
Accessory nerves come from ventral rootlets of spinal cord
Do not arise from the brainstem
XII) The Hypoglossal Nerves
• Runs inferior to the tongue
– Innervates the tongue muscles
The Spinal Nerves
• 31 pairs  contain thousands of nerve fibers
Formula  C8, T12, L5, S5, Cx1 = 31
• Connect to spinal cord
• Named for region of vertebral column
–
–
–
–
–
8 pairs cervical nerves (C1–C8)
12 pairs thoracic nerves (T1–T12)
5 pairs lumbar nerves (L1–L5)
5 pairs sacral nerves (S1–S5)
1 pair coccygeal nerves (Cx1)
Spinal Nerves – Posterior View
Cervical plexus
Brachial plexus
Cervical
nerves
C1 – C8
Cervical
enlargement
Intercostal
nerves
Thoracic
nerves
T1 – T12
Lumbar
enlargement
Lumbar plexus
Sacral plexus
Cauda equina
Lumbar
nerves
L1 – L5
Sacral
nerves
S1 – S5
Coccygeal
nerve
Co1
Spinal Nerves
• Branch into dorsal ramus & ventral
ramus
– Dorsal & ventral rami contain sensory and
motor fibers
• Rami communicantes connect to the
base of the ventral ramus
– Lead to the sympathetic chain ganglia
Spinal Nerves
Sensory axon
and cell body
Dorsal root
Dorsal root
ganglion
Dorsal
ramus
Nerves
Spinal
nerve
Ventral
ramus
Axon of
motor
neuron
Ventral
root
Neuromuscular
junction
Sensory receptors in
skin (e.g., free nerve
endings of sensory
neuron)
Spinal Nerves
White matter
Gray matter
Ventral root
Dorsal & ventral
rootlets of spinal
nerve
Dorsal root
Dorsal root
ganglion
Dorsal ramus
of spinal nerve
Ventral ramus
of spinal nerve
Spinal nerve
Rami communicantes
Sympathetic trunk
ganglion
Innervation of the Back
• Dorsal rami
– Innervate back muscles
– Follow a neat, segmented pattern
• Innervate a horizontal strip of muscle & skin
– In line with emergence point from the vertebral column
Innervation of the Anterior
Thoracic & Abdominal Wall
• Thoracic region
– Ventral rami arranged in simple, segmented
pattern
– Intercostal nerves  supply intercostal
muscles, skin, & abdominal wall
Introduction to Nerve Plexuses
& Peripheral Nerves
• Nerve plexus  a network of nerves!
• Branch from ventral rami (except T2–T12)
– Branch & join with one another
– Form nerve plexuses
• In cervical, brachial, lumbar, & sacral regions
– Primarily serve the limbs
– Fibers from ventral rami criss-cross
The Cervical Plexus
• Buried deep in the neck
– Under the sternocleidomastoid m.
• Most are cutaneous nerves
• Some innervate muscles of the anterior
neck
• Phrenic nerve  the most important
nerve of the cervical plexus
-Innervates diaphragm, mediastinal pleura &
pericardium  Control of breathing!
The Cervical Plexus
Ventral rami
Segmental
branches
Hypoglossal
nerve (XII)
Lesser occipital
nerve
Greater auricular
nerve
Transverse
cervical nerve
Ansa cervicalis
Ventral
rami:
C1
C2
C3
C4
Accessory nerve (XI)
Phrenic nerve
Supraclavicular
nerves
C5
The Brachial Plexus &
Innervation of the Upper Limb
• Brachial plexus lies in the neck & axilla
• Formed by ventral rami of C5–C8
• Cords give rise to main nerves of upper limb
Major terminal
branches
(peripheral nerves)
Cords
Divisions
Trunks
Anterior
Musculocutaneous
Lateral
Median
Medial
Ulnar
Upper
Posterior
Roots
(ventral
rami)
C5
C6
Anterior
Middle
C7
Posterior
Radial
C8
Posterior
Anterior
Lower
Axillary
Posterior
T1
(c) Flowchart summarizing relationships within the brachial plexus
Innervation of the Upper Limb
• Musculocutaneous 
– Innervates the biceps brachii & brachialis m.
• Median 
– Innervates anterior forearm muscles & palm
• Ulnar 
– Innervates intrinsic hand muscles & skin of
hand
Innervation of the Upper Limb
• Radial 
– Largest branch of the brachial plexus
– Innervates muscles of the posterior upper
limb
• Axillary
– Innervates the deltoid & teres minor m.
Major Nerves of the Upper Limb
Axillary nerve
Humerus
Radial nerve
Musculocutaneous nerve
Ulna
Radius
Ulnar nerve
Median nerve
Radial nerve (superficial branch)
Dorsal branch of ulnar nerve
Superficial branch of ulnar nerve
Digital branch of ulnar nerve
Anterior
divisions
Posterior
divisions
Muscular branch
Digital branch
Median nerve
Major Nerves of the Upper Limb
Axillary nerve
Branches of axillary nerve
Radial nerve
Ulnar nerve (cut)
Median nerve (cut)
Posterior cutaneous nerve
Deep radial nerve
Superficial branch of radial nerve
Anterior
divisions
Posterior
divisions
The Lumbar Plexus &
Innervation of the Lower Limb
• Lumbar plexus
– Arises from L1– L4
– Main branches innervate the anterior thigh
• Femoral nerve  innervates anterior thigh
muscles
• Obturator nerve  innervates adductor muscles
The Lumbar Plexus & Nerves
Iliohypogastric
Ilioinguinal
Femoral
Lateral femoral
cutaneous
Obturator
Anterior femoral
cutaneous
Saphenous
(c) Distribution of the
major nerves from
the lumbar plexus
to the lower limb
The Sacral Plexus
• Arises from spinal nerves L4–S4
• Caudal to the lumbar plexus
• Often considered with the lumbar plexus
– Lumbosacral plexus
The Sacral Plexus & Innervation
of the Lower Limb
• Sciatic nerve  the largest nerve of the
sacral plexus
– Actually 2 nerves in one sheath
• Tibial nerve  innervates most of the posterior
lower limb
• Common fibular (peroneal) nerve  innervates
muscles of the anterolateral leg
The Sacral Plexus & Nerves
Superior gluteal
Inferior gluteal
Pudendal
Sciatic
Posterior femoral
cutaneous
Common fibular
Tibial
Sural (cut)
Deep fibular
Superficial fibular
Plantar branches
(c) Distribution of the
major nerves from
the sacral plexus
to the lower limb
A Case Study…
• Black lab hit in car accident
– Initial inability to walk or move limbs
– Hospitalized for 1 week
– Regained motor control of lower limbs
& front right limb
– However, front left limb completely
paralyzed - no sensation or motor control
• What spinal nerves, plexus(es) or peripheral
nerves were likely damaged?
• Damage to:
– Left spinal nerves C5-C8
– Left Brachial plexus
– Peripheral nerves: axillary,
musculocutaneous, radial,
median, & ulnar
Innervation of the Skin: Dermatomes
• Dermatome  an area of skin innervated
by cutaneous branches of a single spinal
nerve!
– Important diagnostic implications
• Upper limb
– Skin is supplied by nerves of the brachial
plexus
• Lower limb
– Lumbar nerves  anterior surface
– Sacral nerves  posterior surface
Map of Dermatomes
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
C2
C3
C4
C5
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T2
C6
C5
C6
C7
L1
C8
L2
T12
S2
S3
T2
C6
C6
C5
L1
C7
C8
L2
S1
L4
S2
S3
S4
S5
C6
C7
C8
S2
S1
L1
L3
L5
L4
C7
C8
L2
S1 S2
L3
C6
T11
T12
L1
L3
L5
L2
L5
L4
L3
L5
L5
L4
S1
S1
L4
L5
(a) Anterior view
L4
L5
S1
(b) Posterior view
Disorders of the PNS
• Shingles (Herpes zoster)
– Viral infection
– Inside of neuron cell bodies of
peripheral nerves – breaks out &
affects skin of that region - dermatome
– Stems from childhood chicken pox
– Often brought on by stress
– Mostly experienced by those over age 50
Varicella zoster virus (chicken pox) can become dormant in the nerve cell bodies and less frequently in non-neuronal
satellite cells of dorsal root, cranial nerve or autonomic ganglion, without causing any symptoms. Years or decades after
a chickenpox infection, the virus may break out of nerve cell bodies and travel down nerve axons to cause viral infection of
the skin in the region of the nerve. The virus may spread from one or more ganglia along nerves of an affected segment and
infect the corresponding dermatome causing a painful itching rash. Although the rash usually heals within 2-4 weeks,
some sufferers experience residual nerve pain for months or years, a condition called postherpetic neuralgia. Exactly how
the virus remains latent in the body, and subsequently re-activates is not understood.
Disorders of the PNS
• Migraine headache
– Relates to sensory innervation of cerebral
arteries
• Arteries dilate & compress & irritate sensory nerve
endings
• Myasthenia gravis
– Progressive weakening of skeletal muscles
– Autoimmune disorder
– Antibodies destroy acetylcholine receptors
Disorders of the PNS
• Carpal Tunnel syndrome
– Swelling/inflammation & compression of the median
nerve of the wrist
due to repetitive,
non-ergonomic
movements
– Pain, discomfort,
tingling, loss of
feeling
The PNS Throughout Life
• Spinal nerves form late in week 4
• Each of the 31 pairs of spinal nerves:
– Sends motor fibers to an individual myotome
– Sends sensory fibers to overlying band of skin
• During week 5, nerves reach the organs
they innervate
The Autonomic Nervous System
(Ch 15)
The Autonomic Nervous System
• Autonomic nervous system (ANS)
– General visceral motor part of the PNS
– ANS has 2 divisions:
• Parasympathetic
• Sympathetic
• Innervates:
• Smooth muscle
• Cardiac muscle
• Glands
The ANS
• The ANS  a system of motor neurons
– Regulates visceral functions including:
•
•
•
•
Heart rate
Blood pressure
Digestion
Urination
Comparison of Autonomic &
Somatic Motor Systems
• Autonomic nervous system
– Chain of 2 motor neurons
• Preganglionic neuron
• Post-ganglionic neuron
– Conduction is slower than somatic nervous
system:
• Thinly myelinated or unmyelinated axons
• Motor neuron synapses in a ganglion
Divisions of the ANS
• Sympathetic & Parasympathetic
– Chains of 2 motor neurons
• Innervate mostly the same structures
• Cause opposite effects!
–Sympathetic division mobilizes the body during
extreme situations  Fight or Flight!
–Parasympathetic division controls
routine maintenance functions
 Rest & Digest
Divisions of the ANS
• Sympathetic  “fight, flight, or fright”
– Activated during EXTREME situations
• Exercise
• Excitement
• Emergencies
Divisions of the ANS
• Sympathetic responses help us respond to
dangerous situations
– Increase heart rate & breathing rate
– Increase blood & oxygen to skeletal muscles
– Dilates pupils & airways
– Sweating
– Motility of the digestive tract & urinary tracts
is inhibited – don’t need to digest or urinate now!
Divisions of the ANS
• Parasympathetic division
– Active when the body is at rest
– Concerned with conserving energy
– Directs “housekeeping” activities
•
•
•
•
Heart rate & breathing are at low-normal levels
Gastrointestinal tract digests food
Urination/defecation, etc.
Pupils are constricted
Anatomical Differences in Sympathetic
& Parasympathetic Divisions
Parasympathetic
• Issue from different
regions of the CNS:
Eye
Brain stem
Salivary
glands
Heart
– Sympathetic  also
called thoracolumbar
division
– Parasympathetic 
also called the
craniosacral division
Sympathetic
Eye
Skin*
Cranial
Sympathetic
ganglia
Salivary
glands
Cervical
Lungs
Lungs
T1
Heart
Stomach
Thoracic
Stomach
Pancreas
Pancreas
L1
Liver
and gallbladder
Lumbar
Adrenal
gland
Liver and
gallbladder
Bladder
Bladder
Genitals
Genitals
Sacral
Anatomical Differences in Sympathetic
& Parasympathetic Divisions
• Length of postganglionic fibers:
– Sympathetic  long postganglionic fibers
– Parasympathetic  short postganglionic fibers; long
preganglionic fibers
• Branching of axons:
– Sympathetic axons  highly branched
• Influences many organs
– Parasympathetic axons  less branching
• Localized effect (more precise output)
• Location of ganglia  differ between both
Anatomical Differences in Sympathetic
& Parasympathetic Divisions
• Neurotransmitter released by
postganglionic axons:
– Sympathetic
• Release Norepinephrine (NE) (adrenergic)
– Parasympathetic
• Release Acetylcholine (ACh) (cholinergic)
Differences Between Sympathetic &
Parasympathetic Divisions
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
NE
ACh
Unmyelinated
postganglionic axon
Lightly myelinated
Ganglion
preganglionic axons
Epinephrine and
ACh
norepinephrine
Adrenal medulla
PARASYMPATHETIC
AUTONOMIC NERVOUS SYSTEM
Two-neuron chain from CNS to effector organs
Blood vessel
ACh
Lightly myelinated
preganglionic axon
Unmyelinated
Ganglion postganglionic
axon
ACh
Smooth muscle
(e.g., in gut), glands,
cardiac muscle
Stimulatory
or inhibitory,
depending
on neurotransmitter
and receptors
on effector
organs
The Parasympathetic Division
• Cranial outflow
– Comes from the brain
– Innervates
• Organs of the head, neck, thorax, & abdomen
• Sacral outflow
– Comes from the sacral region
– Innervates
• Remaining abdominal & pelvic organs
Parasympathetic Division – Cranial Outflow
CN III
CN VII
CN IX
CN X
Ciliary
ganglion
Eye
Lacrimal
gland
Nasal
mucosa
Pterygopalatine
ganglion
Submandibular
ganglion
Otic ganglion
Submandibular
and sublingual
glands
Parotid gland
Heart
Cardiac and
pulmonary
plexuses
Lung
Preganglionic
Postganglionic
CN
Cranial nerve
Parasympathetic Division – Sacral Outflow
Celiac
plexus
Liver and
gallbladder
Stomach
Pancreas
S2
Large
intestine
S4
Small
intestine
Pelvic
splanchnic
nerves
Inferior
hypogastric
plexus
Urinary
bladder
and ureters
Preganglionic
Postganglionic
CN
Rectum
Cranial nerve
Genitalia (penis, clitoris, and vagina)
The Sympathetic Division
• Basic organization
– Issues from T1–L2
– Preganglionic fibers form the lateral gray
horn of the spinal cord
– Supplies visceral organs & structures of
superficial body regions
– Contains more ganglia than parasympathetic
Sympathetic Pathways to the
Body Periphery
• Innervate
– Sweat glands
– Arrector pili muscles
– Peripheral blood vessels
Sympathetic Pathways
Eye
Lacrimal gland
Nasal mucosa
Pons
Sympathetic trunk
(chain) ganglia
T1
Superior
cervical
ganglion
Middle
cervical
ganglion
Inferior
cervical
ganglion
Blood vessels;
skin (arrector pili
muscles and
sweat glands)
Salivary glands
Heart
Cardiac and
pulmonary
plexuses
Lung
Greater splanchnic nerve
Lesser splanchnic nerve
Celiac ganglion
L2
Liver and
gallbladder
Stomach
White rami
communicantes
Superior
mesenteric
ganglion
Spleen
Adrenal medulla
Kidney
Sacral
splanchnic
nerves
Lumbar
splanchnic
nerves
Inferior
mesenteric
ganglion
Small
intestine
Large
intestine
Rectum
Preganglionic
Postganglionic
Genitalia (uterus, vagina, and
penis) and urinary bladder
Sympathetic Trunk Ganglia
• Located on both sides of the vertebral
column
• Linked by short nerves into sympathetic
trunks
• Sympathetic trunk ganglia  also called
– “Chain ganglia”
Sympathetic Trunk Ganglia
• Joined to ventral rami by white & gray
rami communicantes
• Fusion of ganglia  fewer ganglia than
spinal nerves
• Fusion of ganglia most apparent in
cervical region
– Superior, middle, & inferior cervical ganglia
Sympathetic Trunk Ganglia
Spinal cord
Lateral horn
(visceral
motor zone)
Dorsal root
Dorsal root
Ventral root
Dorsal root ganglion
Rib
Dorsal ramus of
spinal nerve
Ventral ramus of
spinal nerve
Gray ramus
communicans
White ramus
communicans
Sympathetic
trunk ganglion
Sympathetic
trunk
Ventral ramus
of spinal nerve
Ventral root
Sympathetic
trunk ganglion
Sympathetic trunk
Skin (arrector
pili muscles
and sweat
glands)
Gray ramus
communicans
White ramus
communicans
Thoracic
splanchnic nerves
1 Synapse at the same level
To effector
Blood vessels
(a) Location of the sympathetic trunk
Splanchnic nerve
Collateral ganglion
(such as the celiac)
Skin (arrector
pili muscles
and sweat
glands)
Blood vessels
Target organ
in abdomen
(e.g., intestine)
To effector
2 Synapse at a higher or lower level
3 Synapse in a distant collateral
ganglion anterior to the vertebral
column
(b) Three pathways of sympathetic innervation
Autonomic Nerves, Plexuses & Ganglia
Superior cervical
ganglion
Middle cervical
ganglion
Stellate ganglion
Sympathetic
cardiac nerves
Aortic arch
Sympathetic
trunk ganglia
Esophagus
Thoracic
splanchnic
nerves
Adrenal
(suprarenal)
gland
Kidney
Lumbar
and sacral
splanchnic
nerves
Left vagus nerve
Cardiac branches
of the vagus
Trachea
Thoracic spinal
nerves (ventral rami)
Cardiac plexus
Pulmonary plexus
on the bronchus
Aorta
Vagus nerve
Esophageal plexus
Diaphragm
Stomach with
vagus nerve
Celiac ganglion
and plexus
Superior mesenteric
ganglion and plexus
Aortic plexus
Inferior mesenteric
ganglion and plexus
Superior hypogastric
plexus
Inferior hypogastric
(pelvic) plexus
Pelvic sympathetic
trunk
Role of Adrenal Medulla in the
Sympathetic NS
• Major organ of the sympathetic nervous
system
• Is the largest sympathetic ganglia
• Secretes great quantities of norepinephrine &
epinephrine
• Stimulated to secrete by preganglionic
sympathetic fibers
The Adrenal Medulla
Sympathetic trunk
Spinal cord:
Ventral
T8–L1
root
Thoracic
splanchnic
nerves
Kidney
Adrenal
medulla
Adrenal gland
Epinephrine and
norepinephrine
Adrenal
medulla cells
Capillary
A Map of Referred Pain
Heart
Lungs and
diaphragm
Liver
Gallbladder
Appendix
Heart
Liver
Stomach
Pancreas
Small intestine
Ovaries
Colon
Kidneys
Urinary
bladder
Ureters
-Visceral pain – detected by visceral
sensory neurons
-No pain results when visceral
organs are cut
-Visceral pain results from chem.
irritation or inflammation
-Visceral pain often perceived to
be of somatic origin
 Phenomenon of referred pain
Central Control of the ANS
Communication at
subconscious level
Cerebral cortex
(frontal lobe)
Limbic system
(emotional input)
Hypothalamus
Overall integration
of ANS, the boss
Brain stem
(reticular formation, etc.)
Regulation of pupil size,
respiration, heart, blood
pressure, swallowing, etc.
Spinal cord
Urination, defecation,
erection, and ejaculation
reflexes
The ANS Throughout Life
• Efficiency of the ANS declines with age
– Constipation due to reduced mobility of GI tract
– Dry eyes due to reduced tear formation
– Fight or flight reaction still intact, but may be
slower to respond
Questions…?
What’s Next?
Lab: PNS & ANS; & Review
Next week: Spring Break!
Mon 4/8 Lecture: no class  study!
Mon 4/8 Lab at 8:00 pm: Lab Exam 3
(You will have sub – Andrew Allen)
Extra…..
Baroreceptor Reflex
Increased blood pressure
1 Baroreceptors in
carotid sinus are
stimulated.
2 Sensory impulses
are carried on visceral
sensory fibers in the
glossopharyngeal
nerves (CN IX).
3
2
4
1
3 Integration occurs in
cardiac center of
medulla oblongata.
4 Efferent pathway via
the vagus nerves (CN X)
5 Parasympathetic
stimulation of heart
decreases heart rate.
Blood pressure decreases
5