Midterm Exam Weeks 1-3 Flashcards
bones of the skull
- neurocranium
- viscerocranium
- skull foramina
- skull fossae
accessory bones of the skull
- ossicles
- hyoid bones
neurocranium (braincase)
- frontal (1)
- parietal (2)
- occipital (1)
- temporal (2)
- ethmoid (1)
- sphenoid (1)
***8 bones total
viscerocranium (facial skeleton)
- maxillae (2)
- palatine bones (2)
- nasal bones (2)
- inferior nasal conchae (2)
- zygomatic bones (2)
- lacrimal bones (2)
- vomer (1)
- mandible (1)
***14 bones total
how many bones total in the skull
22 bones
functions of the neurocranium
- surround and protect the brain
- articulates with the vertebral column
functions of the viscerocranium
- supports and protects the entrances to digestive and respiratory tracts
functions of the accessory bones of the skull
7 bones used for hearing and muscle attachment
external features of the neurocranium
- external acoustic meatus
- mastoid process
- styloid process
- zygomatic process
external acoustic meatus
opening in ear canal (entrance)
mastoid process
attachment site for neck muscles
zygomatic process
forms cheek bones
anterior view of the neurocranium
- frontal bone
- parietal bones (2)
- sphenoid bone
- temporal bones (2)
- ethmoid bone
lateral view of the neurocranium
- frontal bone
- parietal bones (2)
- occipital bone
- sphenoid bone
- temporal bones (2)
- ethmoid bone
- external acoustic meatus
- mastoid process
- styloid process
- zygomatic process
superior view of the neurocranium
- frontal bone
- parietal bones (2)
- occipital bone
- temporal bones (2)
inferior view of the neurocranium
- sphenoid bone
- temporal bone
- zygomatic process
- styloid process
- mastoid process
- mandibular fossa
- occipital bone
mandibular fossa
articulates with the mandible
- joins the mandible to the skull
features of the occipital bone
- foramen magnum (passage of the spinal cords)
- occipital condyle (articulation with atlas C1)
ethmoid bone
unpaired bone that forms part of the orbital wall, nasal cavity/septum
perpendicular plate
extends down into the nasal cavity and divides the nasal cavity into left/right
features of the ethmoid
- crista galli
- superior nasal concha
- middle nasal concha
- cribriform plate
crista galli
perpendicular projection of the ethmoid bone
- acts as an anchoring point for the meninges
cribriform plate
rough base beside the crista galli
- branches of CN1 pass through it
sphenoid bone
unpaired bone that forms part of the eye orbit and base of skull
***looks like owl
features of the sphenoid bone
- greater wing
- lesser wing
- body
- pterygoid process (attachment for muscles of mastication)
- sella turcica
lesser wings vs greater wings
lesser wings are smaller and superior to the greater wings
sella turcica
fossa within the sphenoid bone
- holds pituitary glands
skull foramina
allows for passage of nerves and blood vessels
sphenoid bone - skull foramina
- optic canal (CN II)
- superior orbital fissure (CN III, IV, V1, VI)
- inferior orbital fissure
- foramen rotundum (CN V2)
- foramen ovale (CN V3)
- foramen spinosum
- foramen lacerum
temporal bone - skull foramina
- carotid canal (internal carotid artery)
- internal acoustic meatus (CN VIII)
other features of the skull foramina
- hypoglossal canal (occipital bone)
- CN XII - jugular foramen (occipital + temporal)
- CN IX, X, XI
sutures
boundaries between skull bones
- fibrous, immovable joints
1. sagittal
2. squamous
3. coronal
4. lamboid
sagittal suture
separates the two parietal bones
squamous suture
separates temporal bones from others
coronal suture
separates frontal bones from parietal
lamboid suture
separates the occipital from parietal
cranial fossae
floor of the cranial cavity divided into 3 fossae
1. anterior
2. middle
3. posterior
anterior cranial fossa
frontal lobe of brain
- contains the frontal, ethmoid, & sphenoid bones
middle cranial fossa
temporal lobes of the brain
- contains the sphenoid & temporal bones
posterior cranial fossa
cerebellum
- contains the occipital & temporal bones
bones in orbit
- zygomatic
- sphenoid
- maxillae
- ethmoid
- frontal
- lacrimal
- palatine
maxilla vs. mandible
maxilla: upper jaw
mandible: lower jaw
features of the mandible
- ramus
- body
- angle
- condylar process (articulation with skull)
- coronoid process
temporomandibular joint (TMJ)
only moveable joint of skull that has articulation between:
1. condylar process
2. mandibular fossa
inferior view of the facial skeleton
- zygomatic bones (2)
- zygomatic arch
- maxillae (2)
- incisive foramen (transmits nerves to the mouth)
- palatine bones (2)
- vomer
the hard palate
- palatine process of the maxilla
- palatine bones
palatine bones
extend up to make wall of the nasal cavity
vomer
sits on top of maxilla and palatine bones
accessory bones of the skull
- ossicles
- hyoid bone
ossicles
small bones involved in hearing, housed in the temporal bone
- 3 in each middle ear
1. malleus
2. incus
3. stapes
hyoid bone
“floating bone” located in the neck
- has important attachment site for tongue and muscles involved in swallowing
features of the hyoid bone
- lesser horn (cornu)
- greater horn (cornu)
- body
what are the two cell types the NS is comprised of
- neurons
- neuroglia
major components of the NS
- brain
- spinal cord
- cranial nerves (off brain)
- spinal nerves (off spinal cord)
- ganglia
- sensory receptors
central nervous system
brain and spinal cord
peripheral nervous system
- cranial nerves and spinal nerves
- ganglia and sensory receptors
nerve
bundle of axons located outside the brain and spinal cord
cranial nerves
- 12 pairs of nerves (I-XII)
- emerge from base of the brain
spinal nerves
- 31 pairs of nerves
- emerge from the spinal cord
ganglia
- clusters of neuron cell bodies
- located outside the CNS
***communication
sensory receptors
- monitor changes in the environment
- skin, eyes, nose, muscles, etc.
***detect changes
sensory function of the NS (input)
- sensory receptors detect internal and external stimuli
- sensory (afferent) neurons transmit information to the CNS (through a ganglion)
integrative function of the NS (control)
- perception (conscious awareness) of stimuli
- interneurons analyze and integrate sensory information
motor function of the NS (output)
- initiate actions in effector organs (muscles, glands)
- motor (efferent) neurons respond to integration
neurons in the somatic nervous system
- somatic sensory neurons
- somatic motor neurons
somatic sensory neurons
- convey information TO the CNS FROM sensory receptors
for integration
somatic motor neurons
- convey information FROM the CNS TO skeletal muscles muscular contraction
somatic nervous system
regulates voluntary control of skeletal muscles
autonomic nervous system
regulates involuntary control
1. sympathetic NS
2. parasympathetic NS
sympathetic nervous system (SNS)
- INCREASE in activity and metabolic rate
- fight-or-flight response
Ex. increase HR, dilate pupils
parasympathetic nervous system (PNS)
- DECREASE in activity and metabolic rate
- rest-or-digest response
Ex. decrease HR, constrict pupils
neurons
- form complex processing networks
- transfer and process information
neuroglia
- smaller and more abundant than neurons
- support, nourish, and protect neurons
- do not participate in transfer of information
***create homeostatic environment
cerebrum (telencephalon)
initiates and manages conscious thoughts and actions
- located at the front of the brain
- consists of 2 hemispheres separated by a fissure
actions: read, write, & speak
encephalon (cerebrum)
the largest and more anterior part of the brain
structures of the cerebrum
- white matter
- gray matter
- cerebral hemispheres
- gyrus
- sulcus
cerebral cortex
- outer layer
- covers cerebrum
white matter vs gray matter
white: internal
gray: external, comprises the cerebral cortex
gyrus vs sulcus
gyrus: ridges
sulcus: lines
features of the cerebrum
- longitudinal fissure
- corpus callosum
longitudinal fissure
separates right and left cerebral hemispheres
- stops at the corpus callosum
corpus callosum
connects right and left cerebral hemispheres
frontal lobe
largest lobe, anterior
1. planning
2. decision making
3. mood
temporal lobe
inferior
1. hearing and speaking
parietal lobe
supero-posterior
1. responding to stimuli from environment
2. proprioception
occipital lobe
posterior
1. vision
insular lobe (insula)
autonomic responses
- under parietal
fossae of the brain
- anterior fossa - frontal lobe
- middle fossa - temporal lobe
- posterior fossa - brainstem and cerebellum
lobe divisions of the cerebrum
- central sulcus
- parieto-occipital sulcus
- lateral sulcus
central sulcus
frontal and parietal
- travels transversely, middle of cerebrum
parieto-occipital sulcus
parietal and occipital
lateral sulcus
frontal and temporal
***thumb of glove
cerebellum features
- folia (gray matter)
- arbor vitae (white matter)
cerebellum functions
- coordinates voluntary movements
- regulates posture and balance
cerebellum structure
- cerebellar hemispheres
- cerebellar peduncles (information highway)
- vermis (connects hemispheres)
cerebellum orientation
- falx cerebri
- falx cerebelli
- tentorium cerebelli
- transverse fissure
cerebellar ataxia
uncoordinated movements due to lesion/damage to cerebellum
SCALP
S: skin
C: connective tissue
A: aponeurosis
L: loose connective tissue
P: periosteum
scalp proper
3 superficial layers:
1. skin
2. connective tissue
3. aponeurosis
***all connected, they move together
aponeurosis
- frontalis (raise eyebrows)
- epicranial aponeurosis
- occipitofrontalis
- occipitalis (retract skull)
function of aponeurosis
helps prevent stretching of the scalp
deep scalp
- loose connective tissue
- periosteum
loose connective tissue
emissary veins in loose connective tissue provide a infection pathway into the cranial vault
periosteum
metabolically supportive layer
meninges
3 layers of tissue to provide protection and support to CNS
1. dura mater
2. arachnoid mater
3. pia mater
***superficial to deep
dura mater
- thick layer of meninges deep to calvarium (skull cap)
- encloses dural venous sinuses
dural venous sinuses
major structures that drain the cranial vault
three invaginations of the dura mater within the cranial vault
- falx cerebri (midsaggital)
- falx cerebelli (midsaggital)
- tentorium cerebelli (transverse)
falx cerebri
on longitudinal fissure
tentorium cerebelli
separates cerebrum from inferior cerebellum
2 layers of dura mater
- periosteal layer (superficial)
- meningeal layer (deeper)
***these layers split to help form the dural venous sinuses
2 spaces of dura mater
- epidural space
- subdural space
***potential spaces
epidural space of the scalp
between skull and dura mater
subdural space of the scalp
between dura mater and underlying arachnoid mater
arachnoid mater
- sits deep to the dura, on dura mater
- contains subarachnoid space
subarachnoid space of the scalp
between the arachnoid and pia mater
- contains CSF
***very real space
cerebrospinal fluid (CSF)
helps metabolically and physically support brain
metabolic support of the CSF
exchanges medium (electrolytes and metabolites)
physical support of the CSF
buoyancy and cushion (so brain floats)
arachnoid granulations
drain CSF through the dura mater into the dural venous sinuses
arachnoid trabeculae
gives support to the arachnoid mater
pia mater
closely covers cortical sulci and gyri
- contains subpial space
subpial space
exists between pia and cortex
***potential space
spinal meninges
3 layers of tissue providing protection and support to spinal cord
1. dura mater
2. arachnoid mater
3. pia mater
dura meninges and archanoid meninges
cover the spinal nerve roots
denticulate ligaments (from pia mater)
connect to the dura for cord stability
(very thin ligaments)
epidural space of the spinal menginges
contains fat and venous plexuses
*** real space
subarachnoid space of the spinal menginges
contains CSF
subdural and subpial spaces of the spinal menginges
potential spaces
ventricles
4 cavities within the brain responsible for deep CSF flow
- 2 lateral ventricles
- third ventricle
- fourth ventricle
3 major horns of the lateral ventricles
- anterior horns
- inferior horns
- posterior horns
other features of the lateral ventricle
- body
- atrium
- interventricular foramen
atrium of the lateral ventricle
connects inferior and posterior horn with the anterior
interventricular foramen of the lateral ventricle
communication foramen that carries CSF
lateral ventricles
associated with the telencephalon
third ventricle
associated with the thalamus and hypothalamus (diencephalon)
features of the third ventricle
- roof
- anterior wall
- lateral walls x2
- posterior wall
- floor
- interthalamic adhesion
interthalamic adhesion
band of tissue passing directly through the third ventricle
- connects the bilateral masses of the thalamus
cerebral aqueduct
connects the third and fourth ventricles, passing through the midbrain into the pons
- moves fluid
fourth ventricle
associated with the pons (myelencephalon)
3 apertures:
- 2 lateral and 1 medial
lateral aperatures
foramina of luschka
medial aperatures
foramina of magendie
central canal
continues all the way down the spinal cord
- provides metabolic support (nourishment) to the deep spinal cord
hydrocephalus
abnormal enlargement of the ventricles caused by a buildup of CSF
choroid plexus
collection of ependymal cells found on the walls of all 4 ventricles
- produces cerebrospinal fluid, which flows into the ventricles
ventricular flow
- lateral ventricle
- interventricular foramen
- third ventricle
- cerebral aqueduct
- fourth ventricle
3 pathways after the fourth ventricle: - foramina of luschka
- central canal
- foramen of magendie
cisterns (small subarachanoid spaces)
CSF flows into these and then along the outer corticies of the cerebrum and cerebellum (providing nutrients)
cranial CSF flows
- choroid plexus
- lateral ventricle
- interventricular foramen
- third ventricle
- cerebral aqueduct
- fourth ventricle
- median/lateral aperatures
- subarachnoid cisterns
- bathes superficial brain
- arachnoid granulations
- dural venous sinuses
***or stop at 6 and go to central canal
three branches off the aorta
- brachiocephalic trunk (right side)
- left common carotid artery (ascend to brain)
- left subclavian artery (under clavicle)
brachiocephalic trunk
bifurcates into…
1. right common carotid artery
2. right subclavian artery
4 major arteries to the brain
- common carotid artery splits into the internal carotid artery
- subclavian artery splits into vertebral artery
vertebral artery
runs through the vertebral foramina of the cervical vertebrae
arteries coming through the skull
- internal carotid artery passes through the carotid canal
- vertebral artery passes through the anterior foramen magnum
basilar artery
- joined by an anastomose of the right and left vertebral arteries
- sits in basilar groove of pons
- gives off pontine arteries to supply the pons
posterior cerebral arteries
x2 (supply their respected hemisphere - left/right)
formed by bifurcation of the basilar artery at superior border of pon
- supply the posterior cerebral cortex
circle of willis
anastomosis of arteries providing major cerebral blood supply
circle of willis - the flows
- basilar artery
- posterior cerebral arteries
- posterior communicating arteries
- internal carotid arteries
- middle cerebral arteries
- anterior cerebral arteries
- anterior communicating artery
posterior communicating artery
connects internal carotid artery with posterior cerebral artery
steps of the circle of willis
- basilar artery bifurcates into posterior cerebral arteries
- internal carotid gives off anterior cerebral and middle cerebral arteries
- also ICA gives off posterior communicating artery
- anterior cerebral arteries are connected by anterior communicating artery
purpose of the circle of willis
maintains cerebral blood flow through the brain in case of a clot or something
venous drainage
consists of dural venous sinuses that drain the inner structures of the cranial vault
superior sagittal sinus
lies along mid-sagittal plane, in falx cerebri
confluence of sinuses
- superior sagittal sinus
- confluence of sinuses
- 2 transverse sinuses
transverse sinuses
sit in the tentorium cerebelli
- becomes sigmoid sinus when exiting tentorium cerebelli
sigmoid sinus
drains into the internal jugular vein via jugular foramen
cavernous sinus
venous plexus sitting lateral to body of the sphenoid bone
- drains the eye, parts of the cerebral cortex, and pituitary gland
what is the cavernous sinus pierced by?
internal carotid artery
***only venous sinus that is pierced by another artery (CS)
3 parts of the diencephalon
- epithalamus (above)
- thalamus
- hypothalamus (below)
thalamus
major relay centre of senses except for smell
- autonomic activities
parts of the thalamus
- interthalamic adhesion
- third ventricle
- internal capsule
interthalamic adhesion
joins left and right halves of the thalamus
hypothalamus
- controls body activities
- produces hormones and regulates homeostasis
- regulates emotions & circadian rhythms
infundibulum
connects pituitary gland to the hypothalamus
parts of the epithalamus
- habenular nuclei
- pineal gland
habenular nuclei
sense of smell and emotional response to odors
pineal gland
secretes melatonin
- on third ventricle
3 structures on the brainstem
- midbrain
- pons
- medulla oblongata
medulla oblongata
- continuation of superior spinal cord
- forms inferior brainstem
- contains sensory (ascending) and motor (descending) tract that connects spinal cord to brain
pyramids on the medulla
anterior aspect of white matter
- 90% of axons cross to opposite side = decussation of pyramids
- this allows for contralateral control
pons
superior to medulla, and anterior to cerebellum
- contains a control centre for respiration
midbrain
- extends upward from pons to diencephalon
- involved in the auditory and visual pathway
***connects the 3rd and 4th ventricles
features on the midbrain
- superior colliculi
- inferior colliculi
superior colliculi
vision
inferior colliculi
audition
what system are the cranial nerves a part of
peripheral nervous system
12 cranial nerves
I Olfactory
II Optic
III Oculomotor
IV Trochlear
V Trigeminal
VI Abducens
VII Facial
VIII Vestibulocochlear
IX Glossopharyngeal
X Vagus
XI Accessory
XII Hypoglossal
sensory cranial nerves
contain axons of sensory neurons
- I, II, VIII
motor cranial nerves
contain axons of motor neurons
- III, IV, VI, XI, XII
mixed cranial nerves
axons of sensory and motor neurons
- V, VII, IX, X
I Olfactory Nerve (S) - Function
olfaction/smell
I Olfactory Nerve (S) - Skull Exit
cribriform plate
II Optic Nerve (S) - Function
vision/sight
II Optic Nerve (S) - Skull Exit
optic canal
III Oculomotor Nerve (M) - Function
movement of the eyeballs
III Oculomotor Nerve (M) - Skull Exit
superior orbital fissure
IV Trochlear Nerve (M) - Function
movement of the eyeballs
IV Trochlear Nerve (M) - Skull Exit
optic canal
V Trigeminal Nerve (S&M) - Function
Sensory: innervation to the face
Motor: innervation to muscles of mastication
V Trigeminal Nerve (S&M) - Skull Exits
- ophthalmic branch (V1) exits at superior orbital fissure
- maxillary branch (V2) exits at foramen rotundum
- mandibular branch (V3) exits at foramen ovale
VI Abducens Nerve (M) - Function
movement of the eyeballs
VI Abducens Nerve (M) - Skull Exit
superior orbital fissure
what are the 3 cranial nerves that move the eyeballs
- III Oculomotor Nerve
- IV Trochlear Nerve
- VI Abducens Nerve
VII Facial Nerve (S&M) - Function
Sensory: taste for anterior 2/3 of tongue
Motor: control muscles of facial expression
VII Facial Nerve (S&M) - Skull Exit
stylomastoid foramen (between mastoid and styloid process on temporal bones)
VIII Vestibulocochlear Nerve (S) - Function
hearing and equilibrium
VIII Vestibulocochlear Nerve (S) - Skull Exit
internal acoustic meatus
X Vagus Nerve (S&M) - Function
autonomic regulation (HR, digestion, breathing)
X Vagus Nerve (S&M) - Skull Exit
jugular foramen
XI Accessory Nerve (M) - Function
innervation of trapezius and sternocleidomastoid muscles
XI Accessory Nerve (M) - Skull Exit
foramen magnum
XII Hypoglossal Nerve (M) - Function
- speech
- manipulation of food
- swallowing
XII Hypoglossal Nerve (M) - Skull Exit
hypoglossal foramen
Mnemonic to remember S&M
Some
Say
Money
Matters
But
My
Brother
Says
Big
Brains
Matter
More
protective structures of the spinal cord
- vertebral column
- spinal meninges
- CSF (shock absorbing tissue)
vertebral column
surrounds spinal cord
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 fused sacral
- 4 fused coccygeal
spinal meninges
- dura mater (outermost)
- arachnoid mater (middle)
- pia mater (innermost)
***all continuous with their corresponding cranial mater
structures in the spinal meninges
- epidural space
- subdural space
- subarachnoid space
- denticulate ligaments
epidural space of the spinal cords
between vertebral canal and dura mater
- cushion of fat & CT for protection
subdural space
between dura and arachnoid mater
subarachnoid space
between arachnoid and pia mater
- contains shock absorbing CSF
denticulate ligaments
suspend spinal cord in dural sheath
- triangle shaped membranes
- anchor the spinal cords
cervical enlargement
- C4-T1
- supplies upper extremities
lumbosacral enlargement
- T9-T12
- supplies lower extremities
spinal cord external anatomy
- conus medullaris
- filum terminale
- cauda equina
conus medullaris
located between L1-L2
- determines the termination of the spinal cord
filum terminale
- extension of the pia mater
- attaches the spinal cord to the coccyx
cauda equina
- lumbar, sacral and coccygeal spinal nerves
- “horses tail”
lumbar puncture
samples CSF
internal structure of the spinal cord
- posterior median sulcus (narrow groove)
- anterior median fissure (wider groove)
- central canal
- grey matter (surrounded by the white matter)
- white matter
central canal
extends entire length of spinal cord and contains CSF
grey matter of spinal cord
- posterior horn (sensory)
- lateral horn
- anterior horn (motor)
white matter of spinal cord
- posterior funiculus
- lateral funiculus
- anterior funiculus
sensory vs motor
sensory= ascending
motor= descending
which part of the brainstem surrounds the cerebral aqueduct?
midbrain
central nervous system (CNS)
- brain
- brainstem
- spinal cord
peripheral nervous system (PNS)
nerves and ganglia outside the CNS
*** cranial and spinal nerves
somatic nervous system
- includes both sensory and motor neurons
- voluntary
somatic sensory neurons (afferent)
convey input from
1. receptors for somatic senses
2. receptors for special senses
***information from the outside to brain
somatic motor neurons (efferent)
innervate skeletal muscles
***information from the brain to outside
autonomic nervous system
involuntary
1. regulates cardiac & smooth muscle, and glandular tissue
autonomic motor neurons
regulate visceral activities by exciting or inhibiting activities in effector tissues
somatic sensory vs. visceral sensory
somatic: carries signals from receptors in skin, muscles, bones and joints (DIRECT)
visceral: carries signals mainly from organs in the thoracic and abdominal cavities (PRE AND POST)
which sensory response is not a part of the somatic sensory division?
taste
the 3 general sensory receptors
- free nerve endings
- encapsulated
- proprioceptors
free nerve endings of sensory neurons (functional class)
- nociceptors (pain)
- thermoreceptors (heat and cold)
- mechanoreceptors (pressure)
- chemoreceptors (chemical change)
free nerve endings of sensory neurons (body location)
most body tissues; most dense in connective tissue
modified free nerve endings - Merkel discs (functional class)
mechanoreceptors (light pressure)
modified free nerve endings - Merkel discs (body location)
deepest layer of epidermis (most superficial layer of the skin)
hair follicle receptors (functional class)
mechanoreceptors (hair deflection)
hair follicle receptors (body location)
in and surrounding hair follicles
tactile (meissner’s) corpuscles (functional class)
mechanoreceptors (light pressure, discriminative touch, vibration of low frequency)
tactile (meissner’s) corpuscles (body location)
- hairless skin
- particularly nipples
- external genitalia
- fingertips
- eyelids
lamellar (pacinian) corpuscles (functional class)
mechanoreceptors (deep pressure, stretch, vibration of high frequency)
lamellar (pacinian) corpuscles (body location)
- dermis and hypodermis
2.fingers - soles of feet
- external genitalia
- nipples
ruffini corpuscles (functional class)
mechanoreceptors (deep stretch and stretch of tendons)
ruffini corpuscles (body location)
- deep in dermis
- hypodermis
- joint capsules
muscle spindles (functional class)
mechanoreceptors (muscle stretch)
muscle spindles (body location)
skeletal muscles - particularly those of the extremities
tendon organs (functional class)
mechanoreceptors (tendon stretch)
tendon organs (body location)
tendons
free nerve endings
- free nerve endings of sensory neurons
- modified free nerve endings (merkel discs)
- hair follicle receptors
encapsulated sensory receptors
- tactile (meissner’s) corpuscles
- lamellar (pacinian) corpuscles
- ruffini corpuscles
proprioceptors sensory receptors
- muscle spindles
- tendon organs
features of the spinal cord
- posterior horn (thoracic)
- anterior horn (upper lumbar)
- lateral horn (sacral)
- central canal
- white matter
purpose of spinal nerves
- communication system between brain and various body parts
- essential for voluntary and involuntary actions
- highway for sensory and motor integrations
- important for rapid automatic responses through reflexes
anatomy of the spinal cord
- epineurium (outermost and superficial)
- perineurium (surround axons)
- endoneurium
***all provide structural support, protection, and organization to the nerves
how many pairs of spinal nerves are there?
31 pairs
segments of the 31 spinal nerves
- 8 pairs of cervical nerves
- 12 pairs of thoracic nerves
- 5 pairs of lumbar nerves
- 5 pairs of sacral nerves
- 1 pair of coccygeal nerves
what pairs of nerves leave the spinal cord above their vertebrae level?
pairs 1-7
dorsal root
connects the spinal nerves to the spinal cord
- contains axonal processes of sensory neurons arising from the POSTERIOR horn
- contains the dorsal root ganglion
dorsal root ganglion
- enlargement of the dorsal root
- cluster of cell bodies of sensory neurons
- functions as sensory relay stations by processing and modulating sensory signal before reaching the CNS
where do the spinal nerve and DRG lie within?
the intervertebral foramina
ventral root
- contains axonal processes of motor neurons whose cell bodies are located in ANTERIOR horn
what does each spinal nerve branch into?
- dorsal ramus
- ventral ramus
properties of both the dorsal and ventral rami
- contain both sensory and motor fibres
- exit the vertebral column through intervertebral foramina
- supply the entire somatic region of the body
dorsal rami
supplies dorsum of neck and back
ventral rami
- supplies anterior and lateral regions of neck and trunk
- supplies all regions of the limbs
***much thicker than the dorsal rami
nerve plexuses
formed by the ventral rami when they do not travel directly to their target tissues and instead branch out to form these complex networks
4 primary nerve plexuses function
travel to specific target tissues, such as muscles, skin, and organs, to facilitate motor control and sensory perception
the 4 primary nerve plexuses from ventral rami
- cervical plexus
- brachial plexus
- lumbar plexus
- sacral plexus
cervical plexus spinal nerves
C1-C4
cervical plexus supplies:
sensory and motor innervation to:
- neck
- portions of the head
brachial plexus spinal nerves
C5-T1
brachial plexus supplies:
sensory and motor innervation to:
- shoulder
- upper limbs
lumbar plexus spinal nerves
L1-L4
lumbar plexus supplies:
nerves to the:
- lower back
- abdominal wall
- part of the lower limb
sacral plexus spinal nerves
L4-S5
sacral plexus innervation:
- buttocks
- pelvic structures
- remainder of lower limb
the path from the spinal cord
- nerves originate from the spinal cord through 2 roots
- dorsal roots
- ventral roots
- dorsal and ventral roots unite outside the spinal cord to form a spinal nerve (motor/sensory fibres)
- the spinal nerve branches into 2 rami
- dorsal rami
- ventral rami
dorsal roots
carrying sensory information into the spinal cord
ventral roots
carrying motor information away from the spinal cord
dorsal rami
branches that supply the dorsal parts of the body, including the skin and muscles
ventral rami
larger branches that supply the ventral parts of the body and form complex nerve plexuses
***has both motor and sensory information
dermatomes
- sections of skin innervated by a single spinal nerve
- motor and sensory innervation for those specific areas
important dermatomes
- T4 nipples
- T10 umbillicus (belly button)
motor reflex arc
- neural pathway that mediates rapid involuntary actions
- integrates sensory inputs and motor inputs
- physiological & neural response against potential harmful stimuli
anatomy of the motor reflex arc
- sensory receptor
- sensory neuron (afferent)
- dorsal root ganglion
- dorsal root
- posterior horn
- interneurons
- anterior horn
- motor neuron
- effector muscle
autonomic nervous system (ANS)
involuntary (unconscious) motor (efferent) branch of NS that innervates smooth and cardiac muscle, viscera and glands
other word for ANS
visceral motor system
examples of unconscious processes from ANS
- heart rate
- respiration
- sweating
sympathetic vs. parasympathetic
sympathetic: increases HR; active in times of stress
parasympathetic: decreases HR; active in relaxed conditions
functions of sympathetic NS
- increases HR
- stimulates metabolism
- downregulates digestive activity
- dilates blood vessels in skeletal muscle
functions of parasympathetic NS
- decreases HR
- promotes relaxation
- stimulates digestive secretions and increase gut motility
- dilates blood vessels in GI tract
neurons
highly specialized cells that carry electrical signals
myelin sheath
lipid-rich sheath that surrounds some nerve cell axons
- acts as an insulating layer (increases velocity of the signals)
somatic NS
- voluntary control
- one neuron between CNS and target to innervate skeletal muscle
autonomic NS
- involuntary control
- two neuron chain between CNS and target
- preganglionic neuron synapses to the postsynaptic neuron
location of preganglionic neuronal cell bodies
brainstem or spinal cord
location of postganglionic neuronal cell bodies
autonomic ganglion
preganglionic vs postganglionic
preganglionic: myelinated
postganglionic: unmyelinated
ganglion
collection of neuronal cell bodies found in the PNS
DRG: sensory ganglion in SNS
autonomic ganglia
function as relay stations between preganglionic and postganglionic neurons of the ANS
autonomic outflow of sympathetic
thoracolumbar (T1-L2)
autonomic outflow of parasympathetic
cranio-sacral
cranial nerves:
- CN III - oculomotor
- CN VII - facial
- CN IX - glossopharyngeal
- CN X - vagus
***carry sympathetic information
sacral regions: S2-S4
sympathetic ganglia
- preganglionic: short because they need a fast response (ForF)
- postganglionic: long
rami communicans
connection between the spinal nerve and sympathetic truck
- dorsal and ventral root form spinal nerve
- white + grey ramus communicans
sympathetic outflow
- originates in lateral horn on SC, from segments T1-T12
- pregang neuron exit SC via ventral horn and root to enter spinal nerve
- pregan neuron enters sympathetic chain via white ramus communicans “on ramp”
3 main routes for pregang neurons upon entering sympathetic chain - sympathetic outflow
- synapse within the chain at same level
- change level within the chain and then synapse
- formation of a splanchnic nerve
1st route for pregang entering sympathetic chain
pregang neuron synpases with postgang neuron at same level, and exits via grey ramus, travelling with spinal nerve to target
ex. sympathetic innervation of blood vessels and sweat glands of the body wall and limbs
white ramus communicans vs. grey ramus communicans
white: myelinated (on ramp)
grey: unmyelinated (off ramp)
same level upon entering sympathetic chain
- pregang neurons located between T1-T12
nerves target:
1. body wall
2. ab and thoracic viscera
3. limbs
dermatomes
strip of skin supplied by a spinal nerve
2nd route for pregang entering sympathetic chain
change level: pregang neuron fiber can ASCEND or DESCEND within the sympathetic chain
- runs from T1-L2
- occurs before synapse
change level: ascending nerves target
- head/neck
- thoracic viscera
- upper limbs
change level: descending nerves target
- abdominopelivic viscera
- lower limbs
autonomic plexuses
network of intersecting fibres that supply organs
- postgang contributes to
1. cardiac plexus (heart)
2. pulmonary plexus (lungs)
3rd route for pregang entering sympathetic chain
formation of a splanchnic nerve
splanchnic nerves
associated with abdominoplevic viscera
- form when autonomic fibres do not re-join spinal nerve, instead they form a splanchnic nerve
how are splanchnic nerves formed
pregang fibres bypass the sympathetic chain completely and synapse in a peripheral (prevertebral) ganglion near target organ
where do splanchnic nerves originate
thoracic and lumbar vertebral levels
sets of paired splanchnic nerves
- greater splanchnic (T5-T9)
- lesser splanchnic (T10-T11)
- least/lumbar splanchnic (T12-L2)
where does the greater splanchnic nerve synpase
celiac ganglion
where does the lesser splanchnic nerve synapse
superior mesenteric ganglion
where does the least/lumbar splanchnic nerve synapse
inferior mesenteric ganglion
sympathetic outflow pathways summary
- pregang neuron synapses in sympathetic region, postgang axon exits to re-join spinal nerve at SAME LEVEL to innervate target
- pregang neuron ASCENDS/DESCENDS within sympathetic chain before synapsing, postgang axon exits via spinal nerve above or below original spinal level
- pregang neuron passes through sympathetic chain without synapsing, forming a splanchnic nerve, this synapses in prevertebral ganglion
parasympathetic nervous system targets
- viscera of head and neck
- ab and thoracic viscera
- pelvic viscera
parasympathetic ganglia
preganglionic: long
postganglionic: short
cranial outflow- parasympathetic
pregang cell bodies synapse on ganglia in or near effector organ
- axons travel through cranial nerves III, VII, IX, X
cranial outflow - head and neck
pregang neurons leave brainstem from parasympathetic nuclei and synapse on postgang neuron within parasympathetic ganglia
- CN III, VII, IX - synapse on 4 different ganglia
example of cranial outflow - head and neck
parasympathetic innervation of salivary glands
- CN VII synapses at submandibular ganglion and innervates submandibular galnds
CN VII cranial outflow
- synapses at submandibular ganglion and innervates submandibular and sublingual gland
- synapses at pterygopalatine ganglion and innervates lacrimal gland
CN III cranial outflow
synapses at ciliary ganglion and innervates the eye
cranial outflow: thoracic and abdominal viscera
- pregang neurons leave the brainstem vis CN X, which contribute to autonomic plexuses
- pregang neurons synapse on ganglia within or close to target organ
CN X cranial outflow
synapses at intra-mural ganglion and innervates:
1. cardiac and pulmonary plexus
2. celiac plexus
3. superior hypogastric plexus
sacral outflow: distal GI tract and pelvic viscera
- pregang neuronal cell bodies located in spinal segments S2-S4
- axons travel via pelvic splanchnic nerves which contribute to autonomic plexuses
- pregang nerves synapse within ganglia in or near effector organ to supply targets
pelvic splanchnic nerves supply
inferior hypogastric plexus
visceral afferent fibres
conduct sensory information from autonomic targets to the CNS
- are not considered sympathetic or parasympathetic
visceral reflex arcs
are the simplest functional units in the ANS
- consist of sensory nerve (visceral afferent) and visceral motor neurons
example of visceral reflexes
shinning a light in the eye triggers a visceral reflex that constricts the pupils
enteric nervous system
third division of the ANS
- network of neurons located in the walls of the digestive tract
- receives regulatory signals via sympathetic and parasympathetic divisions