Exam 1 Week 2 Flashcards
What is the structure of the body that is specialized for sound detection?
What are the parts of this structure
- *what parts conduct sound
- *what parts detect sound
EAR
3 PARTS
- OUTER EAR
- funnel shaped structure of cartilage and skin that leads to tympanic membrane
- DIRECTS SOUND (pressure waves in air) toward tympanic membrane
- helps to detect source of sound - MIDDLE EAR
- air filled chamber that contains bones (ossicles) that link tympanic membrane to cochlea
- also contains skeletal muscles that dampen sounds
- middle ear is linked to nasopharync by AUDITORY TUBE (allow for equilibrium of air pressure on inner side of tympanic membrane
- common middle ear infection is OTITIS MEDIA - INNER EAR
- fluid filled chamber in petrous part of temporal bone
- contains cochlea for hearing
- contains vestibular apparatus for gravity detection
* *both innervated by CN VIII - vestibulocochlea
- *Outer and middle ear CONDUCT SOUND
- *Inner ear DETECT SOUND (sensorineural part/cochlea - in petrous part of temporal bone)
1) How can the functioning of inner ear be tested independently
- what is test called?
2) Damage to inner ear called?
3) Damage to middle ear called?
- Clinical test; Inner ear detects transmitted vibrations and can be tested independently by VIBRATIONS TRANSMITTED DIRECTLY THROUGH BONE
- called WEBER TEST; tuning fork on cal various directly causes bone to vibrate, conducted to COCHLEA BY BONE and PERCEIVED AS SOUND by patient - SENSORINEURAL HEARING LOSS - damage to inner ear (independent of outer and middle ear)
- CONDUCTIVE HEARING LOSS - damage to middle ear (tympanic membrane, auditory ossicles/bones)
The ear is composed of 3 parts which are the outer, middle and inner ear. Identify the respective parts of the outer ear
- elastic cartilage covered with skin
- functions to REFLECT SOUND WAVES
- has 4 parts ? (Why can you safely pierce a part of this structure?)
- tube from auricle to the tympanic membrane
- posterior to parotid and TMJ
- anterior to mastoid process
- AURICLE (pinna)
- 4 parts: helix, antihelix, tragus and lobule
- can safely pierce and suspend decorative metal objects from LOBULE - because cartilage does not extend into lobule - EXTERNAL AUDITORY MEATUS
- Outer 1/3rd consist of elastic cartilage (contains hairs, sebaceous glands and ceruminous glands- produce cerumen/ear wax which is insect repellant) *PROTECT TYMPANIC MEMBRANE
- Inner 1/3rd is composed of bone lined with skin
- What is the curvature of the external auditory meatus (children vs adult)
- What is the innervation of the outer ear
* *patient with Bell’s palsy have what sensation
- External auditory meatus is STRAIGHT IN CHILDREN and CURVED AND CURVED ANTERIORLY in adults
**In adults, auricle is pulled up and back to insert otoscope
- Sensory innervation of outer ear is complex and derived from CN: V, VII, IX, X
* Patient with Bell’s palsy can have the sensation of ear ache (pain in outer ear) - somatic sensory (precise sensation)
Identify the part of the ear
- cavity in the petrous portion of the temporal bone that is hard to visualize
- lies below the middle cranial fossa
- *What makes up the boundaries of this part of the ear
1. Separate tympanic cavity from middle cranial fossa
2. Jugular foramen below
3. Opening of auditory tube
4. Leads to mastoid air cells
5. Has oval and round window
5. Tympanic membrane
MIDDLE EAR (Tympanic cavity)
BOUNDARIES
- ROOF - tegmen tympani; thin plate of petrous part of temporal bone that separates tympanic cavity from middle cranial fossa
- FLOOR - jugular foramen lies below cavity; rupture of internal jugular vein can result in hemorrhaging into the tympanic cavity
- ANTERIOR WALL - has opening of auditory tube (posterior 1/3rd of tube is in bony canal, anterior 2/3rd is cartilage)
- POSTERIOR WALL - leads to mastoid air cells in mastoid process (opening is called ADITUS); canal for facial nerve (CN VII) courses in posterior wall (after passing from medial wall)
- MEDIAL WALL - lateral wall of inner ear
* OVAL WINDOW (fenestra vestibuli) - attachment of stapes
* ROUND WINDOW (fenestra cochlea) - other end of coiled cochlea - LATERAL WALL - Tympanic Membrane e
Summarize the main points of otitis media
- Very common MIDDLE EAR INFECTION in children
- Middle ear is the dead space cavity that opens to NASOPHARYNX
- Infection can spread from upper respiratory system - Spread of infection from respiratory system can damage auditory ossicles which lead to HEARING LOSS
- Prolonged infection in Tympanic cavity can spread through tegmen tympani to brain
* *Tx is tympanostomy - tube through tympanic membrane
What happens to the occurrence of otitis media with age?
What 2 factors contribute to this?
**Occurence DECLINES with age of child (rapidly after age 5)
- cranial growth is associated with a change in orientation of the auditory tube (from horizontal to angled inferiorly)
- increase in the size of the lumen
Identify the structure(s) of the middle ear
- link tympanic membrane to oval window and cochlea
- anchored by ligaments
- amplify effect of vibration
AUDITORY OSSICLES
From lateral to medial
- Malleus (hammer)
- Incus (anvil)
- Stapes (stirrup)
- ossicles amplify effect of vibration
- tympanic membrane has 15-20 tines greater area than footplate of stapes (area of oval window); this increases force per unit area and helps transmit sound vibrations from air to fluid in inner ear (impedance matching)
What is seen in otoscope view of tympanic membrane
What is a branch of VII that carry taste to anterior 2/3rd of tongue
- *In OTOSCOPE VIEW - there is a broad attachment of malleus to tympanic membrane
- handle/malleus is attached to upper half of tympanic membrane
- malleus is supported by ligaments linking it to wall of tympanic cavity
- part of tympanic membrane surrounding handle is tense (pars tense)
- upper end is less tense (pars flaccida)
**CHORDA TYMPANI - branch of VII (carry taste fibers to ANTERIOR 2/3rd of tongue)
Identify the muscles of the middle ear
-what is their role?
**paralysis of muscles result in what?
DAMPEN SOUND
1. TENSOR TYMPANI MUSCLE Origin - canal in anterior wall Insertion - handle of malleus Nerve - V3 Action - TENSES/TIGHTENS tympanic membrane (prevent damage to inner ear)
- STAPEDIUS MUSCLE
Origin - posterior wall (landmark is pyramid)
Insertion - neck of stapes
Nerve - VII (facial nerve)
**Both muscles act to DAMPEN MOVEMENTS OF OSSICLES (decrease intensity of sound)
- *Paralysis of muscles produces HYPERACOUSIA (sound seem too loud)
- damage to facial nerve
What is the SENSORY innervation of the MIDDLE EAR
_ what innervates mastoid air sinus and auditory tube (give rise to what?)
- *VISCERAL SENSORY (GVA) from tympanic plexus of CN IX (GLOSSOPHARYNGEAL)
- imprecise sensation, branch of IX that enter tympanic cavity (exit via jugular foramen)
- IX Nerve Forms
1. Tympanic plexus that also innervates (VISCERAL MOTOR) the mastoid air sinus and auditory tube which can give rise to
2. Lesser petrosal nerve; VISCERAL MOTOR (parasympathetic) to parotid gland
Identify the nerve
- leaves posterior cranial fossa via internal auditory meatus (enters facial canal))
- what are the 3 branches
FACIAL NERVE
- GREATER PETROSAL NERVE
- VISCERAL MOTOR parasympathetic to lacrimal gland, mucous glands of nose and palate (visceral sensory to nasopharynx) - STAPEDIAL NERVE
- BRANCHIOMOTOR to stapedius - CHORDA TYMPANI
- Taste to anterior 2/3 of tongue
- Parasympathetics to submandibular, sublingual salivary glands
Identify;
- branch of VII (facial nerve)
- no function in middle ear
- provides taste to anterior 2/3 of tongue
- Parasympathetics to submandibular ganglion - leaves facial canal and passes through tympanic cavity and crosses over upper end of handle of malleus before exiting via petrous panic fissure
**damage lead to what?
CHORDA TYMPANI
**If tympanic membrane is pierced - Damage CHORDA tympani and lose taste to anterior tongue on that side
The neck is compartmentalized into what 3 compartment
- VERTEBRAE AND MUSCLES which support and move head and neck
- VISCERA and rostral continuation GU and respiratory systems
- Blood vessels and nerve (CAROTID SHEATH)
- POSTERIOR compartment
- ANTERIOR compartment
- LATERAL compartment
The posterior compartment of the neck is composed of vertebrae and muscles that support and move head and neck respectively.
What are the types of muscles in the different orientation to vertebrae
- Posterior to vertebrae
- Lateral to vertebrae
- Anterior
- Posterior side
- muscles are continuations of muscles of back (deep muscles) and suboccipital region - Lateral side
- scalene muscles; flex neck LATERALLY - Anterior side
- Prevertebral muscles ; directly anterior to vertebrae; FLEX head and neck
What is the anterior compartment of the neck composed of (2)
- VISCERAL - in lower part of neck; trachea, thyroid gland and esophagus
- PHARYNX - in upper part of neck; pharynx. Pharynx is a tube composed of muscles and facia that is continuous anteriorly with the oral and nasal cavities; the esophagus and the larynx open into the pharynx
The lateral compartment of the neck is lateral and posterior to the pharynx
**what is contained here? (What is in this content? What is not?)
CAROTID SHEATH
Contents
- Carotid arteries (common and internal carotid arteries)
- Internal jugular veins
- Vagus nerve
Not in carotid sheath
1. Sympathetic chain (posterior to carotid sheath)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
**2 are not attached to hyoid bone
- STERNOCLEIDOMASTOID
Action
Nerve
- Sternocleidomastoid (2 heads)
Action
- On both sides; flex neck
- Singly; rotate head so face is directed to opposite side
Nerve Accessory nerve (XI)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- 2 muscles are not attached to hyoid bone
2. Scalenus anterior and Scaleus mediums
Action
Flex neck and elevate rib 1
Nerve
Branches of ventral rami of cervical spinal nerves
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
*There are 4 Infrahyoid muscles
- Omohyoid
(Muscle has 2 bellies connected by an intermediate tendon)
Action
Depresses hyoid bone
Nerve
Ansa cervicalis
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Infrahyoid muscles
2. Sternohyoid
Action
Depresses hyoid bone
Nerve
Ansa cervicalis
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Infrahyoid muscles
3. Sternothyroid
Action
- Depresses thyroid cartilage
- indirectly depresses hyoid bone, larynx
Nerve
Ansa cervicalis
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Infrahyoid muscles
4. Thyrohyoid
Action
- Depresses hyoid bone
- Elevates larynx
Nerve
C1 via branch hitch-hiking with hypoglossal nerve (XII)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Suprahyoid muscles
1. Digastric (has two bellies)
Action
- Elevates hyoid bone
- Depresses mandible
Nerve
Posterior belly - facial nerve (VII)
Anterior belly - trigeminal nerve (V3)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Suprahyoid muscles
2. Stylohyoid
Action
Elevates hyoid bone
Nerve Facial nerve (VII)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Suprahyoid muscles
3. Mylohyoid
Action
- Elevates hyoid bone
- Raises floor of mouth during swallowing
Nerve Trigeminal nerve (V3)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
- There are 4 Suprahyoid muscles
4. Geniohyoid
Action
- Elevates hyoid bone
- Draws hyoid forward
Nerve
C1 via branch hitch-hiking with hypoglossal nerve (XII)
The muscles of neck and head are divided into:
- muscles not attached to hyoid (2)
- Infrahyoid muscle (4)
- Suprahyoid muscle (4)
- Muscles of pharynx (4)
*There are 4 muscles of pharynx. 3 are circular muscles. 1 is Longitudinal
Name all
CIRCULAR 1. Superior constrictor Action : constrict pharynx Nerve : X 2. Middle constrictor Action: constrict pharynx Nerve: X 3. Inferior constrictor Action: constrict pharynx Nerve: X
LONGITUDINAL
4. Stylopharyngeus
Action: Raises pharynx and pull wall laterally
Nerve: IX
What is the most important landmark in neck for diagnosis and procedures?
*what vessels is between 2 heads of this muscle and why is it important
- what is anterior to muscle?
- what are the lateral mass anterior to the muscle
**what is located deep to sternocleidomastoid
STERNOCLEIDOMASTOID
- important landmark in diagnosis and procedures in neck
**INTERNAL JUGULAR VEIN can be accessed and catheterized between sternal and clavicular heads of sternocleidomastoid (VENOUS CATHETERIZATION)
- *Thyroid gland and jugular chain of lymphatics are located ANTERIOR to sternocleidomastoid
- BRANCHIAL CLEFT CYSTS are lateral masses anterior to sternocleidomastoid
**Deep cervical chain of lymph nodes are located deep to sternocleidomastoid
What is used to diagnose neck masses?
- lateral neck mass
- midline mass
- Use STERNOCLEIDOMASTOID to diagnose neck masses
- BRANCHIAL CYST or (fistula = channel) are lateral neck masses located anterior to sternocleidomastoid
- *This is different form THYROGLOSSAL duct cysts
- this will be MIDLINE MASSES
- Cyst = pocket
- Fistula = channel
What is the SECOND most important landmark in neck? Why?
SCALENUS ANTERIOR AND SCALENUS MEDIUS
- second muscle of neck not attached to hyoid
It contains:
- BRANCHIAL PLEXUS and subclavian artery pass between scalenus anterior and scalenus medius
- PHRENIC NERVE (nerve to diaphragm) passes anterior to scalenus anterior
* Phrenic nerve come from C3,C4,C5 and cause diaphragm to contract
Identify bone
- located in anterior part of neck
- free floating (no bony attachment)
- attached to skull and skeleton only by muscles and ligaments
What ligament;
- Like bone to styloid process
- Like bone to thyroid cartilage
- *What are the parts of the bone?
- *what attach to body of bone?
HYOID BONE (U shape)
- STYLOHYOID LIGAMENT: links hyoid to styloid process of temporal bone
- THYROHYOID MEMBRANE : links hyoid to thyroid cartilage
PARTS
- Body (central part)
- Greater and lesser horns (Cornu)
- *All INFRAHYOID and SUPRAHYOID muscles (except sternothyroid) attach to body of hyoid)
- *Greater horns can be palpated in neck above thyroid cartilage and used as landmarks to locate surrounding structures
What anchors tongue and floor of mouth and also support larynx
*Why is this important?
HYOID BONE
- muscles which move hyoid bone produce movements of larynx and tongue (as occur during swallowing and talking)
- contraction of muscles can stabilize position of hyoid bone (e.g in movement of tongue)
Identify the muscles
-all act to DEPRESS the hyoid bone
INFRAHYOID MUSCLES
4 muscles
- OMOHYOID (SUPRASCAPULAR notch to hyoid bone) -Greek for shoulder (2 bellies) - intermediate tendon linked to clavicle and rib 1
- STERNOHYOID - manibrium/sternum and clavicle to hyoid
- STERNOTHYROID - manubrium to thyroid cartilage
- THYROHYOID - thyroid cartilage to hyoid (ALSO ELEVATES LARYNX)
Identify the muscles
-all act to ELEVATE the hyoid bone
SUPRAHYOID MUSCLES
4 muscles
- DIGASTRIC - 2 bellies/2 cranial nerves ; insert to hyoid via INTERMEDIATE TENDON
* also OPENS MOUTH - STYLOHYOID - styloid process of temporal bone to hyoid; tendon splits to surround digastric tendon
- MYLOHYOID - forms muscular floor of mouth (ELEVATES floor of mouth in swallowing)
- GENIOHYOID - elevates and pulls hyoid forward
* *Important in swallowing
Identify the group of nerves of the neck
-formed from ventral primary rami of spinal nerves C2-C4, which emerge from posterior border of sternocleidomastoid (near its mid-point)
**Most branches are cutaneous
CERVICAL PLEXUS
- Lesser Occipital nerve (C2) -innervates skin behind ear and skin of upper lateral neck
- Great auricular nerve (C2,C3) - innervates skin over parotid gland and skin located inferior to ear
- Transverse Cervical nerve (C2,C3) - innervates skin of anterior neck
- Supraclavicular nerves (C3, C4) - innervates skin of lower lateral neck and shoulder
- Phrenic nerve - (C3,4,5) provides MOTOR innervation to the diaphragm, crosses anterior to scalenus anterior muscle
- Nerves emerge from posterior border of sternocleidomastoid
- Important for anesthesia for suturing neck
Identify the nerve of the neck
- fibers from C1 join Hypoglossal Nerve (XII)
- some leave and join fibers of C2 and C3 to form the nerve
- other fibers continue with XII to innervate thyrohyoid and geniohyoid
(Looks like XII innervates neck muscles; actually C1-C3 do)
*CN XII receives hitchhiking fibers
ANSA CERVICALIS
- fibers from anterior RAMUS of C1 join the hypoglossal nerve (CN XII) as “hitchhiking fibers”
- some fibers leave the XII in the neck and descend down and join other nerves of anterior rami of C2 and C3
- all of this form a loop called ANSA CERVACALIS
- some fibers leave the AC and innervate neck muscles
- other fibers of C1 travel further with the XII
- those fibers then leave the XII to innervate thyrohyoid and geniohyoid muscles
- the result is that XII has branches that look like they innervate neck muscles, but THEY DON’T
- only fibers from C1-C3 actually innervate those muscles
Identify the artery of the head and neck
- At root of neck; artery passes laterally toward arm, posterior to scalenus anterior
- becomes AXILLARY artery at rib 1
**Scalenus anterior muscle divides this artery into what 3 parts
SUBCLAVIAN ARTERY
PART 1 (medial to scalenus anterior)
1. Vertebral artery (ascends into neck and enters foramina transversaria of vertebrae C1-C6)
2. Internal thoracic artery (descends into thorax posterior to sternum)
3. Thyrocervical trunk - branches into;
A. Inferior thyroid
B. Transverse (or superficial) cervical artery
C. SUPRASCAPULAR arteries
PART 2 (posterior to scalenus anterior)
1. Costocervical trunk - branches;
A. Superior intercostal artery supply first two intercostal spaces with posterior intercostal arteries
B. Deep cervical artery - to deep neck muscles
PART 3 (Lateral to scalenus anterior) NO BRANCHES
Identify the arteries to neck and head
-arise from aorta on left, brachiocephalic artery on right; it ascends into neck and divides at level of upper border of thyroid cartilage (vertebral level C4) into internal and external arteries
CAROTID ARTERIES
- Internal carotid artery ascends to skull without branching
- External carotid branches supply face and scalp; branches are (from inferior to superior)
Identify the 8 branches of external carotid artery.
3 branches
- branches from anterior side of external carotid
- branches from posterior side of external carotid
- terminal branches of external carotid
Branches from anterior side of external carotid
- SUPERIOR THYROID ARTERY - descends to thyroid (gives off superior laryngeal a. Which courses to larynx)
- ASCENDING PHARYNGEAL ARTERY - ascends to pharynx
- LINGUAL ARTERY - tongue
- FACIAL ARTERY - below then on surface of mandible
Branches from posterior side
- OCCIPITAL ARTERY - supplies posterior scalp
- POSTERIOR AURICULAR ARTERY - supplies posterior ear and adjacent scalp
Terminal branches - external carotid ends when it divides to;
- SUPERFICIAL TEMPORAL ARTERY - arise opposite external auditory meatus; ascends to supply scalp and temporalis muscle
- MAXILLARY ARTERY - many/15 branches
What is the major cause of ischemic stroke of the brain
CAROTID ARTERY STENOSIS
-MRI and CT angiography are the principal diagnostic tools for diagnoses and surgical intervention (Carotid Endarterectomy)
Most arterial branches have accompanying veins (venue comitantes); branching pattern is variable
**What are the 6 branches
- SUPERFICIAL TEMPORAL and MAXILLARY VEINS - unite to form RETROMANDIBULAR vein (RM)
- RETROMANDIBULAR vein - divides at angle of mandible into anterior (AD) and posterior divisions (PD)
- Anterior division - joins facial vein to form COMMON FACIAL VEIN which drains to INTERNAL JUGULAR VEIN
- Posterior division - joins POSTERIOR AURICULAR VEIN to form EXTERNAL JUGULAR VEIN drains to SUBCLAVIAN VEIN
- Anterior jugular vein - forms from small veins below mandible; descends to join EXTERNAL JUGULAR VEIN above clavicle
The fascia of the neck are divided to 2 layers. Identify them
A.
- loose CT below dermis
- in neck generally thin and hard to demonstrate
- contains platysma and superficial veins
B.
- layers of CT
- one layer completely surrounds neck
- other layers form tubes contained within that layer
- SUPERFICIAL FASCIA
- DEEP CERVICAL FASCIA
- Investing layer of deep cervical fascia - surrounds neck, splits around sternocleidomastoid, trapezius, Supra and infrahyoid muscle
- Prevertebral layer - surround vertebral column, muscles of neck, (Prevertebral, lateral vertebral, suboccipital muscle)
- Pretracheal layer - surround trachea, esophagus and thyroid continues to thorax
- Carotid sheath - surrounds common and internal carotid, internal jugular and X vagus (Not sympathetic chain)
- *Retropharyngeal space - between pretracheal and pre vertebral layers - infection from head (tonsillitis) can spread to mediastinum
- *INFECTIONS TEND TO REMAIN LOCALIZED WITHIN THE CAROTID SHEATH
Identify the problem
- can be difficult to diagnose (no external swelling)
- life threatening because can block airway
RETROPHARYNGEAL ABSCESS
- Infection in Retropharyngeal space can spread unimpeded to thorax (mediastinum)
- George Washington may have died of this
The lymphatics of head and neck are described as 3 groups of lymphatics and nodes
Name all
2 are arranged as rings; drain to chain
- Superficial ring of nodes - drains areas adjacent to their location; consist of submental, submandibular, Buccal, parotid, retroauricular and occipital nodes
- Deep ring - consist of Retropharyngeal and Pretracheal nodes
- Deep cervical chain - chain of nodes along internal jugular vein; receive lymph vessels from all nodes of head and neck
- Jugular lymph trunk - efferent lymph vessels from deep cervical nodes drain into THORACIC DUCT (on left), RIGHT LYMPHATIC DUCT (on right); these drain into brachiocephalic veins (at junction of internal jugular and subclavian veins)
Neck Part 2
**The thyroid gland has 2 lobes inferior to and on sides of thyroid cartilage? What are they called
**WHAT is the laryngeal prominence of thyroid cartilage called?
**What is located below cricoid cartilage?
**When present, what is often attached to hyoid bone by fibrous strand?
**Left and right LATERAL LOBES (cover common carotid artery)
**Adam’s apple
**ISTHMUS - located below cricoid cartilage
**PYRAMIDAL LOBE - attached to hyoid bone by fibrous strand
Summary Thyroid gland composed of - 2 lateral lobes -central isthmus - pyramidal lobe (sometimes present above isthmus)
The thyroid gland is very vascular. Identify 2 branches from the external carotid artery and thyrocervical trunk
that supply the thyroid gland
1.
Come from external carotid that course with superior laryngeal n.
- Come from course with recurrent laryngeal n.
- SUPERIOR THYROID CAROTID ; courses with superior army gear nerve
- INFERIOR THYROID ARTERY come from thyrocervical trunk and course with recurrent laryngeal nerve (located in groove btw trachea and esophagus)
Why must care be taken during thyroid surgery
Why?
What is affected?
Care taken not to damage RECURRENT LARYNGEAL NERVES (when lighting inferior thyroid artery)
- paralyze all muscles of larynx on one side (except cricothyroid muscle)
- patient has only HOARSE VOICE OR WHISPER
The thyroid glands have lots of veins. Name 3 veins that supply the thyroid glands
- *What is the large vein that can be in front of (anterior to) the trachea that can cause bleeding in tracheotomy.
- how can bleeding be avoided?
- SUPERIOR THYROID VEIN - vein follows superior thyroid artery
- MIDDLE THYROID VEIN - veins drain into internal jugular vein
- INFERIOR THYROID VEIN - left and right veins can join together and enter LEFT BRANCHIOCEPHALIC vein
- *INFERIOR THYROID VEINS course anterior to trachea, if large can cause extensive bleeding in tracheotomy
- *emergency access to trachea, bleeding avoided by CRICOTHYROTOMY
Identify the glands
- 4 very small bodies (2 on each side) located posterior to thyroid gland or within gland;
- position is very variable
PARATHYROID GLANDS
- superior parathyroid gland
- Inferior parathyroid gland
Identify
- there are three (3) cervical ganglia (superior, middle, inferior)
- all 3 ganglia send gray rami to cervical spinal nerves
- Most of head and neck is supplied by superior cervical ganglion
- Superior cervical ganglion sends postganglionic fibers via unnamed branches to form a plexus on carotid arteries and their arterial branches
SYMPATHETIC TRUNK
- *Sympathetic chain;
- directly anterior to vertebrae
- Not to be confused with Vagus X nerve
- deep to (not in) carotid sheath
**Sympathetics to most of head are form superior cervical ganglion
Identify
- Follows left margin of esophagus, enters left brachiocephalic vein (at junction of internal jugular and subclavian veins)
- Right recurrent laryngeal nerve courses under subclavian artery; left recurrent laryngeal under aorta; both ascend in groove between trachea and esophagus
- Thoracic duct at root of neck
2. Recurrent laryngeal nerve
What are the triangles of the neck?
**what muscle divides the neck into the 2 triangles?
STERNOCLEIDOMASTOID muscle divides the neck into 2 triangles :
- ANTERIOR TRIANGLE - (anterior to muscle) containing structures related to carotid arteries
- POSTERIOR TRIANGLE - (posterior to muscle), containing structures related to subclavian artery, cervical and brachial plexus
The sternocleidomastoid muscle divides the neck to anterior and posterior triangle.
- *Identify the boundaries of the posterior triangle
- anterior
- posterior
- inferior
- superficial
- deep
*what nerve divide the posterior triangle into inferior/careful and superior/carefree zone
- ANTERIOR - Sternocleidomastoid
- POSTERIOR - Trapezius
- Inferior - Clavicle
- SUPERFICIAL cover - superficial fascia, platysma and investing layer
- DEEP - (floor) covered by Prevertebral layer of fascia
- **The ACCESSORY NERVE is considered to divide the posterior triangle into clinically ‘careful’ zone (inferior) and ‘carefree’ zone (superior)
- *BRACHIAL plexus is the careful zone
NOTE
Subclavian vein is not within posterior triangle
The sternocleidomastoid muscle divides the neck to anterior and posterior triangle.
**Identify the boundaries of the anterior triangle
ANTERIOR - midline of neck
POSTERIOR - Sternocleidomastoid
SUPERIOR - lower margin of mandible
**Subdivided to smaller triangles
CONTENTS
- carotid sheath; common carotid dividing into internal and external carotid arteries
- numerous branches of external carotid
- Veins; Internal jugular vein
- Nerves; Hypoglossal nerve and descending branch of ansa cervicalis, Accessory and vagus nerves
- Lymphatics =; Deep cervical chain of lymph nodes
In cervical vertebra; articular facets are angles superiorly and medially to permit for what movements?
- FLEXION-extension
- In C1, superior articular facets about occipital condyles- joint permit FLEXION and extension and no rotation - Rotation
- Right of atlas rotates on dense of C2
- C1-C2 joints permit rotational movement of head ‘no’
- Does not permit flex-extend
Identify 3 ligaments of vertebrae
- strong band on anterior side
- weaker, narrower band
- yellow elastic bands connecting laminae
- ANTERIOR LONGITUDINAL LIGAMENT - strong band on anterior side
- POSTERIOR LONGITUDINAL LIGAMENT - weaker, narrower band
- LIGAMENTA FLAVA - yellow elastic bands connecting laminae
The craniovertertebral joints are specialization of joints between vertebrae
- Identify joint between atlas (vertebra C1) and occipital bone
- movements are FLEXION-extension of the neck (nodding the head in ‘yes movement) - Joint between atlas (C1) and axis (C2)
- movement is rotation of atlas on axis (shaking head in ‘no’ movement)
- ATLANTO-OCCIPITAL JOINT
2. ATLANTO-AXIAL JOINT
IDENTIFY
- stabilize joints and protect medulla and spinal cord
- some prevent excessive movement
- some are extensions of ligaments of spinal column
**Identify the 4 types
**What fuse to DURA
LIGAMENTS of Craniovertebral joint
- Anterior Atlanta-occipital membrane (C1 - Occipital) = anterior longitudinal ligament
- Membrane tectoria (C2-Occipital) = posterior longitudinal ligament
- Post Atlanto-occipital membrane (C1 - Occipital) = LIGAMENTUM flava
- Cruciate ligament
**Posterior Atlano-occipital Membrane and membrane tectoria fuse to DURA
The ligaments of craniovertebral joints help stabilize and protect medulla. Identify the 4 ligaments
1- extension of anterior longitudinal ligament
2 - extension of posterior longitudinal ligament
3 - extension of LIGAMENTA flava
4 - composed of 3 parts
5. -From dens to occipital bone
- Anterior Atlanta-Occipital membrane = extension of anterior longitudinal ligament - extends from atlas (C1) to occipital bone
- Membrana Tectoria = extension of posterior longitudinal ligament of spinal column - extends from axis to occipital bone, posterior to cruciate ligament
- Posterior Atlanto-Occipital membrane = extension of LIGAMENTA flava - extends from atlas (C1) to occipital bone
- Cruciate (cruciform or cross) ligament - composed of;
- Transverse ligament of atlas
- Superior band to occipital bone
- Inferior band to body of C2 - Atlas “check” ligaments - extending laterally from dens to occipital bone
- prevents excessive rotation of head
There are 4 ligaments of cranial-vertebral joints. The cruciate ligament is one of them and include 3 parts
*Identify
- Transverse band within vertebral canal which is attached to INNER SIDE OF ATLAS (C1)
- holds dens of axis (C2) against inner aspect of anterior arch of atlas - Upper extensions from transverse ligament of atlas to occipital bone superiorly
- Lower extensions from transverse ligament of atlas to body of the axis inferiorly
**A tear in the cruciate ligament lead to what?
- Transverse ligament of atlas
- Superior band to occipital bone
- Inferior band to body of C2
**Tear of cruciate ligament of atlas Can allow dens to be driven into spinal cord (result in QUADRIPLEGIA) or medulla (resulting in DEATH)
Describe the process of hanging someone
- most cervical vertebrae have articular facets that permit extension-FLEXION and rotational movements
- the joint between the atlas and axis is specialized and permit ONLY ROTATIONAL MOEVEMENT (Joint C1-C2)
- IN ACCURATE HANGING; a large knot is placed posterior to the joint btw C1 and C2 and weight of body forcibly flexes the joint (TYPICALLY FRACTURING C2- result in instantaneous death)
- IN INNACURATE HANGING; knot is placed behind other cervical joints resulting in FLEXION of neck, prolonged agony and death by strangulation. Similar fractures occur after trauma (e.g automobile accidents)
The suboccipital region in the suboccipital triangle are bounded by muscles.
- what are the boundaries
- Inferior
- medially
- laterally
- Inferiorly - Obliquus capitis inferior
- Medially - Restuc capitis posterior major
- Laterally - Obliquus capitis superior
There are 4 muscles that make up the suboccipital muscles
- RECTUS Capitis Posterior Major
Attachments
Action
Nerve
Attachment
C2 - occipital bone
Action
- extends head
- rotates skull in unilateral action
Nerve
Suboccipital n. (Dorsal ramus of C1)
There are 4 muscles that make up the suboccipital muscles
- RECTUS Capitis Posterior Minor
Attachments
Action
Nerve
Attachment
C1 - occipital bone; Dura mater
Action
Extends head
Nerve
Suboccipital n. (Dorsal ramus of C1)
There are 4 muscles that make up the suboccipital muscles
- Obliquus Capitis Inferior
Attachments
Action
Nerve
Attachments
C2 - C1
Action
Rotates head
Nerve
Suboccipital n. (Dorsal ramus of C1)
There are 4 muscles that make up the suboccipital muscles
- Obliquus Capitis Superior
Attachments
Action
Nerve
Attachment
C1 - Occipital bone
Action
Extends head
Nerve
Suboccipital n. (Dorsal ramus of C1)
Identify the nerves of suboccipital region
- dorsal ramus of C1 spinal nerve
- MOTOR to suboccipital region
- dorsal ramus of C2 spinal nerve
- SENSORY to skin of back of head and neck
- Suboccipital nerve
2. Greater Occipital nerve
Identify the arteries of the suboccipital region
- Branch of external carotid artery; pierces fascia of trapezius muscle to supply back of head and suboccipital region
- Ascends neck through foramina transversaria of vertebrae C1-C6 and enters skull through foramen magnum
- passes through suboccipital triangle
- OCCIPITAL ARTERY
2. VERTEBRAL ARTERY
The insertion of what muscle to DURA may form anatomical basis for relief of tension headaches by neck massage
Insertion of RECTUS CAPITIS POSTERIOR MINOR
Identify
- sound generator
- consist of cartilage that are connected by membranes and ligaments and moved by muscles
**How are sounds extensively modified?
LARYNX - sit above trachea
2 functions
-sound production
-prevent objects from entering respiratory system (closes off respiratory system - allows increase in abdominal pressure)
** sounds are extensively modified in speech and singing by RESONANCE of PHARYNX, NASAL CAVITY and ORAL CAVITY
The larynx consists of cartilages that are connected by membranes and ligaments and moved by muscles
*Identify the 6 cartilage in larynx
- Thyroid cartilage
- Cricoid cartilage
- Arytenoid cartilage
- Corniculate cartilage
- Cuneiform cartilage
- Epiglottis cartilage
There are 6 cartilage that make up the larynx in part
Identify first 3
- Shield shaped cartilage; has horns (cornua) projecting from upper and lower edges; have SYNOVIAL HINGE JOINTS with cricoid cartilage
- Complete ring of cartilage resting on first tracheal cartilage; has narrow arch (anterior part) and broad lamina (posterior part)
- Two pyramidal shaped cartilages that rest above lamina of cricoid; have SYNOVIAL JOINT with cricoid cartilage that allow for SWIVEL AND SLIDING movements
- THYROID CARTILAGE
- CRICOID CARTILAGE
- ARYTENOID CARTILAGE
There are 6 cartilage that make up the larynx in part
Identify LAST 3
- Two small nodule shaped cartilages that articulate with spices of the arytenoid cartilages, give attachment to aryepiglottic folds
- Two small rod shaped cartilages in aryepiglottic folds
- Left shaped cartilage posterior to root of tongue; connected to body of hyoid bone and back of thyroid cartilage
- COMICULATE CARTILAGE
- CUNEIFORM CARTILAGE
- EPIGLOTTIC CARTILAGE
There are structural and functional ligaments of larynx
How many structural ligaments of larynx are there. Name them and what is the overall function ?
- Links THYROID CARTILAGE to HYOID BONE;
- Links CRICOID TO THYROID CARTIAGLE
- Links CRICOID TO FIRST TRACHEAL CARTILAGE
- Links ARYTHNOID TO EPIGLOTTIS
- Links EPIGLOTTIS TO THYROID CARTILAGE
There are 5 structural ligaments of larynx that hold larynx, hyoid and trachea together
- Thyrohyoid membrane (thickened medial part called median thyrohyoid ligament)
- Cricothyroid membrane (thickened medial and anterior part called median cricothyroid ligament)
- Cricotracheal ligament
- Quadrangular membrane (lower free edge is called vestibular ligament)
- Thyroepiglottic ligament
Identify the functional ligament of larynx
- elastic membrane forming vibrating lips
- arises from entire upper edge of arch of cricoid
- attaches anteriorly to thyroid cartilage
- POSTERIORLY to vocal processes of arytenoid cartilages
- upper free edges are thickened to form vocal ligaments
*8What is the opening between vocal ligaments called?
CONUS ELASTICUS
*opening between vocal ligaments is called RIMA GLOTTIDIS
What are the 2 functions of the CONUS ELASTICUS
- SOUND PRODUCTION - when the vocal ligaments are brought close together, air forced through rima glottidis causes ligaments to vibrate producing sound
- CLOSING RIMA GLOTTIDIS - when vocal ligaments are pressed tightly together the rima glottidis is closed
- this regents upward movement of the diaphragm when the abdominal muscles contract
- contraction of the abdominal muscles increases pressure in the abdominal-pelvic cavity (this is useful in childbirth, micturition, defecation etc)
The muscles of the larynx are divided into extrinsic and intrinsic muscles.
- Extrinsic muscles of larynx
- move entire larynx
- active during swallowing
- SUPRAHYOID muscles elevate larynx
- INFRAHYOID muscles depress larynx - Intrinsic muscles of larynx
- mostly well named for their origins and insertions
- change pitch by changing tension in vocal ligament; increase tension raises pitch, decreased tension lowers pitch
- open and close rima glottidis
There are 6 muscles of the larynx
- CRICOTHYROID
Attachment
Action
Nerve
Attachment
Cricoid cartilage to thyroid cartilage
Action
- Tenses vocal fold
- Raises pitch of sound
Nerve
External Laryngeal n. (X)
There are 6 muscles of the larynx
- THYROARYTENOID
Attachments
Thyroid cartilage to arytenoid cartilage
Action
- Relaxes vocal fold
- Decreases pitch of sound
Nerve
Recurrent Laryngeal n. (X)
There are 6 muscles of the larynx
- POSTERIOR CRICOARYTENOID
Attachments
Cricoid cartilage to Arytenoid cartilage
Action
- Abducts vocal folds
- Opens rima glottidis
Nerve
Recurrent laryngeal n (X)
There are 6 muscles of the larynx
- Lateral CRICOARYTENOID
Attachments
Cricoid cartilage to arytenoid cartilage
Action
- ADducts vocal folds
- Closes rima glottidis
Nerve
Recurrent Laryngeal n. (X)
There are 6 muscles of the larynx
- Arytenoid (transverse arytenoid)
Attachment
Arytenoid cartilage to Arytenoid cartilage of opposite side
Action
- Adducts vocal folds
- Closes rima glottidis
Nerve
Recurrent laryngeal n. (X)
There are 6 muscles of the larynx
- Aryepiglottic muscle
Attachment
Arytenoid cartilage to epiglottic cartilage
Action
- Pulls down epiglottis during swallowing
Nerve
Recurrent laryngeal n. (X)
The recurrent laryngeal n. (X) innervating the laryngeal muscles is specifically called what nerve?
INFERIOR LARYNGEAL NERVE
What are the 3 folds and 2 areas associated with the larynx
FOLDS
- VOCAL (True Vocal) FOLDS - overlie vocal ligaments
- VESTIBULAR (False Vocal) folds - overlie vestibular ligaments
- ARYEPIGLOTTIC FOLDS - overlie upper edge of quadrangular membrane
AREAS
- VESTIBULE - inlet above false vocal folds
- VENTRICLE - between false and true vocal folds; laryngeal sinus is lateral extension of ventricle
What is the innervation of the larynx
Branches of VAGUS NERVE
A. Superior Laryngeal nerve
- Internal laryngeal nerve - visceral sensory to larynx above vocal folds
- External laryngeal nerve - BRANCHIOMOTOR to cricothyroid muscle
B. Recurrent Laryngeal nerve - visceral sensory to larynx below vocal folds; BRANCHIOMOTOR to all other muscles of larynx
What is the blood supply to the larynx (2)
- Superior laryngeal artery - from superior thyroid artery
2. Inferior laryngeal artery - from inferior thyroid artery
What is the lymphatics of the larynx
- Superior deep cervical nodes - drain larynx above vocal folds
- Inferior deep cervical nodes - drain larynx below vocal folds
When their is obstruction of larynx, what procedure is done to remove object
-which is safe (less bleeding)
- CRICOTHYROTOMY
- emergency cut made through the cricothyroid membrane to pen air passage - TRACHEOTOMY
- preferred to cut into trachea because he thyroid veins overlie the trachea
Identify the structure
- fibromuscular tube that forms a common, superior end of both respiratory and digestive system
- continuous inferiorly with trachea and esophagus
- anterior with oral and nasal cavities
- has layers like GI tract
PHARYNX
- Larynx and esophagus open into pharynx
- pharynx is a tube of muscles and fascia that opens to nasal and oral cavities
- *Acts to propel food in swallowing
- voluntary phase
- involuntary phase 1,2,3 = muscles of pharynx propel food down to esophagus
Pharynx acts to propel food in swallowing.
- What separates the pharynx and the oral cavity?
- what is the sensation of pharynx and oral cavity
PLATOGLOSSAL ARCH
- Pharynx - Visceral (imprecise sensation - you gag if poked)
- Oral cavity - Somatic (Precise sensation)
**Palatoglossal arch - site of oropharyngeal membrane
The pharynx is a muscular tube that opens to oral and nasal cavities (larynx and trachea) and is continuous with esophagus
- Identify the 4 layers of pharynx from internal to external ?
- what do they correspond to?
Correspond to layers of GI tract:
- MUCOSA - epithelial lining
- SUBMUCOSA = connective tissue layer
- MUSCULAR LAYER composed of inner circular (sphincters) and outer longitudinal layers (tube)
- ADVENTITIA = Buccopharyngeal fascia = part of pre tracheal fascia of neck
Recall; the horizontal view of the neck should the 3 compartment of the neck.
*WHich compares have the following respectively
- Vertebrae and muscles
- Viscera and rostral continuation GI and resp systems
- Blood vessels and nerve - Carotid sheath
- POSTERIOR COMPARTMENT
- Vertebrae and muscles which support and move head and neck - ANTERIOR COMPARTMENT
- VISCERA and rostral continuation GI and respiratory systems - LATERAL COMPARTMENT
- Blood vessels and nerve (CAROTID SHEATH)
The following description is the location of what?
- extends from base of skull SUPERIORLY to level of cricoid cartilage
- INFERIORLY; posterior to nasal cavity, oral cavity and larynx
- ANTERIOR; to vertebrae C1 to C6
- MEDIAL; to carotid sheath and cranial nerves IX-XII
PHARYNX
Identify the group of muscles
- all insert on midline fibrous RAPHE POSTERIORLY
- all serve to propel food to esophagus during swallowing by CONSTRICTING PHARYNX
CIRCULAR MUSCLES OF PHARYNX
-overlap each other somewhat
FUNCTION; constrict pharynx during swallowing to propel food inferiorly into esophagus and aid in closing off nasal from oral pharynx by contacting soft palate
*All constrictors insert to PHARYNGEAL RAPHE which is a median fibrous band on posterior aspect of pharynx
**Longitudinal muscles of pharynx (stylopharyngeus) are important in swallowing
The muscles of pharynx are divided into circular and longitudinal muscles. There are 3 circular muscles of pharynx called constrictors
- Superior constrictor
Attachments
Action
Nerve
Attachments Pterygomandibular raphe (Ct band continuous anteriorly with BUCCINATOR muscle TO pharyngeal raphe
Action
Constrict pharynx
Nerve
Vagus X nerve
The muscles of pharynx are divided into circular and longitudinal muscles. There are 3 circular muscles of pharynx called constrictors
- Middle constrictor
Attachments
Action
Nerve
Attachments
Hyoid bone to pharyngeal raphe
Action
Constrict pharynx
Nerve
Vagus X nerve
The muscles of pharynx are divided into circular and longitudinal muscles. There are 3 circular muscles of pharynx called constrictors
- Inferior constrictor
Attachments
Action
Nerve
Attachments
Thyroid and cricoid cartilages to pharyngeal raphe
Action
Constrict pharynx
Nerve
Vagus X nerve
The muscles of pharynx are divided into circular and longitudinal muscles. There are 3 circular muscles of pharynx called constrictors . There is 1 longitudinal muscle
- Stylopharyngeus
Attachments
Action
Nerve
Attachments
Temporal bone -styloid process to thyroid cartilage
Action
Raises pharynx and pulls walls laterally
(When swallowing)
Nerve
IX (GLOSSOPHARYNGEAL)
What do gaps between constrictor muscles allow for?
*where are all the 3 gaps
Allow vessels, nerves and muscles to pass into the interior of the pharynx
- Gap between superior constructor and base of skull
- Gap between superior and middle constrictor
- Gap between middle and inferior constrictor muscles
The gaps between the constrictor muscles all for passage of nerve, vessels and muscle to interior of pharynx
- *Identify the gaps
1. Passage of auditory tube into pharynx and LEVATOR veil palatini muscle
2. Passage of stylopharyngeus muscle and GLOSSOPHARYNGEAL nerve CN IX
3. Passage of internal laryngeal nerve (branch of vagus) and superior laryngeal artery (branch of superior thyroid artery)
- Gap btw Superior constrictor and skulll
- LEVATOR veil palatini muscle
- Auditory tube - Gap btw superior and middle constrictor
- GLOSSOPHARYNGEAL N (IX)
- Stylopharyngeus muscle - Gap btw middle and inferior constrictor
- Superior laryngeal artery
- Internal laryngeal nerve
The divisions of the pharynx are located relative to nasal and oral cavities and larynx
Name the 3
- Nasopharynx
- Oropharynx
- Laryngopharynx
There are 3 divisions of pharynx
Identify
LOCATION Superior; to soft palate Posterior; to nasal cavity Anterior; to occipital bone Inferior; to sphenoid *superior border is body of sphenoid
WHat are the contents ?
-what is common in children and how will it affect to breathing
NASOPHARYNX
Contents
- Pharyngeal tonsil (lymphoid tissue in submucosa of roof and posterior wall of nasopharynx)
- Opening of Auditory tube
**ADENOIDS is an enlargement of the pharyngeal tonsil that is COMMON IN CHILDREN ; enlarged pharyngeal tonsils can INTERFERE WITH BREATHING and gives characteristic NASAL VOICE
There are 3 divisions of pharynx
Identify
LOCATION
Superior boundary; soft palate
Inferior boundary; upper border of epiglottis
Posterior to palatoglossal arch
*what are the contents
OROPHARYNX
**Palatoglossal arch is mucosal fold covering Palatoglossal muscle; forms boundary between oral cavity and oropharynx
CONTENTS
- Palatine tonsils
- Glossoepiglottic folds - folds of mucosa from posterior tongue to epiglottis; there is one medial glossoepiglottic fold and two lateral folds
A child comes into the ED choking and mum says popcorn got stuck in throat.
- *What is the first place that food can get stuck
- *what is second place
- VALLECULAE (Latin for little ditches)
- in OROPHARYNX
- 2 depressions of mucous membrane between medial and lateral glossoepiglottic folds
- *Food or foreign objects can lodge in valleculae
- PIRIFORM recess
- in LARYNGOPHARYNX
**Foreign bodies or food can lodge in valleculae or PIRIFORM recess; patient cannot localize object and can complain that ‘something is stuck in my throat’ because innervation of pharynx is VISCERAL SENSORY (IMPRECISE LOCALIZATION)
There are 3 divisions of pharynx
Identify
LOCATION
- btw upper border of epiglottis superiorly and lower border of cricoid cartilage inferiorly
-communicates inferiorly with esophagus and anteriorly larynx
*what are the contents?
LARYNGOPHARYNX
Contents
1. PIRIFORM recess - deep trench in mucous membrane in anterolateral wall of laryngopharynx, lateral to laryngeal inlet
What is the innervation of the pharynx
- Motor
- Sensory
*What is exception?
- Motor
- BRANCHIOMOTOR (SVE) ; all muscles of pharynx are innervated by the PHARYNGEAL BRANCH OF VAGUS (X)
*exception is STYLOPHARYNGEUS - innervated by IX- GLOSSOPHARYNGEAL
- Sensory
- Visceral sensory (GVA) ;
a. NASOPHARYNX - facial nerve (VII)
B. OROPHARYNX - GLOSSOPHARYNGEAL (IX)
C. LARYNGOPHARYNX - Vagus (X)
What is the blood supply and lymphatics of the pharynx
- ARTERIES from ascending pharyngeal, facial, maxillary, and lingual arteries
- VEINS drain to pharyngeal plexus which drains to internal jugular vein
- LYMPHATICS to deep cervical nodes
- Why is there a nervous system?
2. Define a reflex?
- The nervous system rapidly generates appropriate reactions to sensory stimuli
- A reflex is defined as a STEREOTYPED MOTOR RESPONSE to a specific sensory stimulus
A reflex is a stereotyped motor response to a specific sensory stimulus.
*What does a typical reflex consist of? (3)
- SENSORY RECEPTOR - detects stimulus (afferent arm of reflex arc)
- INTERNEURONS - (most often) receive inputs from sensory receptors and synapse on motor neurons; effects on motor neurons can be excitatory or inhibitory; not present in monosynaptic reflexes
- MOTOR NEURONS - (efferent arm of reflex arc) produce muscle contraction, motor response
**Reflexes often have effects in more than one muscle; the muscles may all be at the same joint; sometimes the muscles are at different joints in the same limb or in the opposite limb
Reflexes are valuable tools for clinical evaluation of?
Elavuation of NERVOUS SYSTEM FUNCTION
- For reflex to occur, all elements must be functional and pathways must be intact
- If reflexes are ABSENT, a physician can DIAGNOSE where the PATHWAY is INTERRUPTED
- If reflexes are ABNORMAL, can diagnose where function is COMPROMISED
*** Reflexes can be used to test nervous system function, locate site of lesion
How are reflexes evaluation? (2)
Identify
- enhanced reflexes
- abnormal rapid muscle contractions
- Amount (size, magnitude) of motor response
- Latency (time to elicit motor response)
- Changes in reflexes are clinical signs
- HYPER-REFLEXIA; enhanced reflexes, in some disease processes, damage can enhance reflex responses
- CLONUS; series of abnormal, rapid alternating contractions and relaxations of muscle produced by single stimulus
**How do you rate stretch (deep tendon) reflexes?
0 - absent 1 - diminished 2 - normal 3 - brisk, hyper-reflexive 4 - hyper-reflexic, pathologic
Give example of reflex that is protective and relatively constant?
- Protective and relatively constant reflex; PUPILLARY LIGHT REFLEX
- light shone in eye causes pupillary to constrict ; protective reflex that limitslight entering eye (protects photoreceptors)
- STIMULUS (afferent arm) - light in eye; sensory neurons (photoreceptors in retina) detect light; sensory signals in OPTIC NERVE (CN II detects light)
- RESPONSE (efferent arm) - Occulomotor nerve (CN III, innervates pupillary constrictor muscle)
***Connection is present at all times
What are some reflexes that are constant under same circumstances ?
Reflex relatively constant under the same controlled circumstances; e.g MONOSYNAPTIC STRETCH REFLEX (DEEP TENDON REFLEX)
-can be tested in a number of muscles; activate muscle spindles (response is consistent is pt is relaxed)
**REFLEXES CAN BE MODULATED by the CNS -reflexes can be changed or blocked in some behaviors
A reflex is stereotyped motor response to a specific sensory stimulus
**What are more complex responses to sensory stimuli?
Give example
Why is this different from reflexes
AUTOMATIC REACTIONS - more complex responses to sensory stimuli
E.g maintaining balance
Differ from reflexes:
- Complexity - many muscles activated
- Duration - responses last longer
- Influenced by different types of sensory inputs (e.g postural response changed by wearing a backpack)
Give 3 examples of how Somme reflexes in their complexity form part of automatic reactions?
- MAINTAINING BALANCE when standing and walking
(muscle spindles) - REGULATING MUSCLE TENDONS - not damage muscles or insertions (Golgi tendon organs)
- Stepping on a nail - AVOID PAINFUL STIMULI
(Cutaneous, nociceptive (pain) receptors)
**Automatic reactions differ from reflexes in duration and complexity (number of muscles activate) ; they can also be influenced by different types of sensory inputs (e.g wearing a backpack)
Other ‘reflexes’ actually represent triggering of more complex behaviors by sensory signals
*SOme behaviors are produced by?
Give examples
PATTERN GENERATORS
- some ‘reflexes’ trigger activities produced by pattern generators
- group of interneurons that are interconnected and produce activities in motor neurons and can generate rhythmic behaviors
Examples
- Palmar grasp
- Moro reflex - arm extend
- STepping reflex - actually eliciting a motor neuron
- Plantar grasp
- Placing reflex
- Tonic neck reflex - extend ipsilateral arm, flex opposite arm
There are 3 classical spinal reflexes that each have a specific sensory stimulus and motor response
Identify all 3
- STRETCH REFLEX
- produced by activating muscle spindles; contributes to maintaining postural stability
- countering sudden loads - AUTOGENIC INHIBITION
- produced by activating Golgi tendon organs; aids in regulating muscle tension
- prevents damage to tendon, bone - FLEXION REFLEX
- produced by activating cutaneous, pain afferents - avoid obstacle or painful stimulus (stepping on nail)
What is terminology used to describe a reflex
- Muscle that contains sense organ
- Muscle that produces similar action
- Muscle that produces opposite action
- Muscle of opposite arm or leg
- HOMONYMOUS MUSCLE
- muscle that contains or is associated directly with the sense organ producing the reflex - SYNERGIST MUSCLE
- muscle that produces a similar motor action (movement) - ANTAGONIST MUSCLE
- muscle that produces the opposite motor action (movement) - CONTRALATERAL MUSCLE
- muscle of opposite limb (leg or arm)
SUMMARY TABLE
Identify how muscle type is affected by the 3 classic spinal reflexes
- HOMONYMOUS muscle = muscle that contains sense organ
*Stretch reflex (muscle spindle)
EXCITE
*Autogenic Inhibition (Clasped knife) Golgi tendon organ
INHIBIT
*Flexor Reflex (Cutaneous sense organs)
EXCITE flexor
SUMMARY TABLE
Identify how muscle type is affected by the 3 classic spinal reflexes
- SYNERGIST muscle = muscle that produces similar action
*Stretch reflex (Muscle spindle)
EXCITE
*Autogenic inhibition (Clasped knife) - Golgi tendon organ
INHIBIT
*Flexor Reflex (cutaneous sense organs)
EXCITE other flexors
SUMMARY TABLE
Identify how muscle type is affected by the 3 classic spinal reflexes
- ANTAGONIST MUSCLE = muscle that produces opposite action
*Stretch reflex (Muscle spindle)
INHIBIT
*Autogenic inhibition (Clasped knife) - Golgi tendon organ
EXCITE
*Flexor Reflex (cutaneous sense organs)
INHIBIT extensor
SUMMARY TABLE
Identify how muscle type is affected by the 3 classic spinal reflexes
- CONTRALATERAL MUSCLE = muscle that produces opposite action
*Stretch reflex (Muscle spindle)
NO EFFECT
*Autogenic inhibition (Clasped knife) - Golgi tendon organ
NO EFFECT
*Flexor Reflex (cutaneous sense organs)
EXCITE extensor
SUMMARY TABLE
- Reflexes have what effect in muscle and SYNERGIST (muscles that produce same action)
- Reflexes have what effect in antagonist muscles
*SAME EFFECT
- OPPOSITE EFFECT
- flexor reflexes have opposite effect in other leg
Identify reflex
- Stimulus - fast stretch of muscle
- Sense organ excited - muscle Spindle Ia and II sensory neurons
- Primary response - muscle that is stretched CONTRACTS RAPIDLY
STRETCH REFLEX (Aka myotatic reflex, deep tendon reflex)
Group Ia - MONOSYNAPTIC connections with alpha motor neurons (fastest reflex known, delay at synapse about 1 msec)
Group II - make;
- MONOSYNAPTIC connections - direct to motor neuron
- POLYSYNAPTIC connections to motor neurons (through interneurons)
What are other components of stretch reflex?
- EXCITE SYNERGIST MUSCLES (brachialis)
- spindle afferents also make excitatory MONOSYNAPTIC connections with SYNERGIST muscles - INHIBIT ANTAGONIST MUSCLES (triceps)
- RECIPROCAL INHIBITION
- spindle activity also excites interneurons that make inhibitory synapses on motor neurons to antagonist muscles (polysynaptic)
Identify the 3 components that state muscle tonus (under stretch reflex)
**What is the clinical testing of stretch reflex
MUSCLE TONUS
- Because connection is monosynaptic, ongoing activity in muscle spindles is important in determining firing of alpha motor neurons at rest
- Eliminating activity of spindles can decrease motor neuron firing producing decreased tonus
- Increased sensory activity can increase tonus
- *Clinical testing of stretch reflex: TENDON TAP
1. Tendon tap elicits twitch because it excites almost all muscle spindles simultaneously
2. Excitation converges upon motor neuron
In general, decrease stretch reflexes can indicate what?
Increased stretch reflexes indicate what?
Decreased stretch reflexes - Lower motor neuron disorders
Increased stretch reflexes - Upper motor neuron syndromes
Identify cell type under Stretch reflexes
- interneurons that receive excitatory inputs from recurrent branches of motor neurons and make inhibitory synapses upon the same motor neurons
RENSHAW CELLS
*These circuits can limit motor neuron firing; inhibition can dampen or reduce reflexes
What feed back loop do muscle spindle form and why?
NEGATIVE FEEDBACK LOOP
- Perturbation produces increase in length (stretch) which excites spindle which
- Excites motor neuron, which excites muscle which decreases length
Identify the reflex type
- STIMULUS (clinical test) ; Large force on tendon (pull on muscle when resisted
- RESPONSE: muscle tension decreases (clasped knife reflex)
- SENSORY RECEPTOR; Golgi tendon organ Ib
- SYNAPSES; Poly-synaptic (via interneurons)
- EFFECT ON MUSCLE ; Inhibit HOMONYMOUS (same) muscle
- OTHER EFFECTS; also inhibit sygernist; excite antagonist muscles
- FUNCTION; protective, prevent damage to tendon
AUTOGENIS INHIBITION
Inverse myotatic reflex
Identify the reflex type
- STIMULUS (clinical test) ; Sharp, painful stimulus (as in stepping on nail)
- RESPONSE: Limb is rapidly withdrawn from stimulus
- SENSORY RECEPTOR ; cutaneous (skin) and pain receptors
- SYNAPSES ; Poly-synaptic (via interneurons)
- EFFECT ON MUSCLE : Excite flexor muscle
- OTHER EFFECTS ; also inhibits extensors of same limb; excite extensors and inhibit flexors of opposite limb (crossed extensor reflex)
- FUNCTION; protective, withdraw from painful stimuli; cross extension supports posture when leg is lifted
- FUNCTION
FLEXOR REFLEX
Identify reflex type
STRETCH REFLEX
- STIMULUS
- RESPONSE
- SENSORY RECEPTORS
- SYNAPSES
- EFFECT ON MUSCLE
- OTHER EFFECTS
- FUNCTION
- Rapid stretch of muscle (test ; tap on muscle tendon)
- Stretched muscle contracts rapidly (e.g knee jerk)
- Muscle spindle primary Ia and secondary II sensory neurons
- Ia- Monosynaptic
II- Monosynaptic (weak) and POLYSYNAPTIC - Excite HOMONYMOUS (same) muscle
- Also excite sygernist and inhibit antagonist muscles (reciprocal inhibition)
- Aid in maintaining posture, counter sudden loads
In testing stretch reflex muscles
- *what signal levels are tested
1. Biceps
2. Triceps
3. Intrinsic hand muscles (e.g interosseous)
4. quadriceps (knee jerk or patellar reflex)
5. Gastrocnemius, soleus (ankle jerk or Achilles’ tendon reflex)
- C5,6
- C6,7
- C7,8
- L3,4
- S1,2
What is the test and clinical sign of babinski reflex
BABINSKI
Test
- stroke sole of foot
Clinical sign
Normal - FLEXION (Plantar FLEXION) of big toe
UMN damage - EXTENSION (dorsiflexion)) of big toe
Identify the reflex
Stimulus - large force exerted by pulling on muscle tendon (muscle is strongly contracted)
Sense organ excited - golgi tendon organ (Ib afferent)
Primary response - muscle attached to tendon RELAXES
AUTOGENIC INHIBITION
- *Synapses - polysynaptic
- Ib afferent makes an excitatory synapse upon an interneurons; the interneurons makes an inhibitory synapse upon the motor neuron from the same muscle in which the tendon organ is located
What are 2 other effect sof AUTOGENIC inhibition
- Inhibits SYNERGIST muscles
- GTO makes excitatory synapse on interneurons; interneurons makes inhibitory synapse on motor neurons to SYNERGIST muscle - Excites antagonist muscles
- GTO makes excitatory synapse on interneurons; interneurons makes excitatory synapse on motor neurons to antagonist muscle
**CLASPSED KNIFE REFLEX : in upper motor neuron lesions, tonus increases, resistance to stretch increases; if sufficient force is applied, limb resistance suddenly decreases (like pocket knife snapping shut)
Name 2 functions of AUTOGENIC inhibition
- Regulating muscle tension - forces developed BY contractions of muscles are automatically controlled so that they do not cause damage to tensions (e.g lifting heavy object)
- Regulation of force during other behavior is more complex (e.g walking)
- connections for AUTOGENIC inhibition may be inactivated during walking
- Effects of golgi tendon organs can then become excitatory via other interneurons
Identify the reflex
- Stimulus - painful or noxious stimulus (stepping on nail)
- Sense organ excited - Cutaneous resistors, pain receptors (nociceptors)
- Primary response - protective withdrawal of limb
FLEXOR REFLEX
*Synapses - polysynaptic; cutaneous afferents make excitatory synapses upon interneurons; the interneurons (one or more in pathway) make excitatory synapses upon motor neurons to flexor muscles
What are the other effects of flexor reflex
- Excite sygernist muscles - excite other flexors in same leg
- Inhibit antagonist muscles - inhibit extensors in same leg
- CROSSED EXTENSION REFLEX - excite extensors and inhibit flexors in opposite leg
What is the function and clinical Changes of flexor reflexes
FUNCTION
- protective (e.g stepping on nail)
- the net effect of these connections is that very rapid adjustments are made so that one leg is lifted rapidly and the other supports the weight of the body
CLINICAL CHANGES
- Flexor Reflexes can change after lesions, disease processes e.g babinski reflex - seen in UMN lesion
- direction of movement changes from flexing toe to extending toe is UMN lesion
What is the usefulness of pattern generators in spinal cord and brainstem
A. Spinal cord contain pattern generators which a re networks of interneurons that generate patterned motor activities
B. Walking - walking is though to be produced by pattern generators
- after spina cord lesion, rear limbs of animals and legs of humans can walk on treadmills (if body is supported)
- led to new therapies for patients with spinal cord injuries
**Stepping reflex - in infants probably represent activation of the pattern generator for walking
Infants don’t learn to walk, they learn to maintain balance while walking
A set of barriers separate the CNS from the rest of the body.
- Identify the barriers ?
- Why is it essential?
- How is each barrier created?
- Arachnoid space
- Choroid plexus epithelium
- CNS capillary endothelium
* extracellular environment is essential for the normal function and health of the CNS
*Each barrier is created by tight junctions between the edges of the cells forming the barrier
*What membrane surround the entire CNS, separating it from the rest of the body
**what barriers (2) maintain separation between blood and the CNS
- ARACHNOID MEMBRANE
- blood vessels penetrate the arachnoid to supply the CNS
- *2 Barriers
1. Blood-brain barrier
2. Blood-CSF barrier - both maintain separation between blood and the CNS
What is responsible for the secretion of CSF and ISF
**CSF is secreted by what in whic barrier?
**Cells forming BBB and BCB secrete the extracellular fluids of the CNS
- Blood - CSF barrier: CSF (cerebrospinal fluid)
- Blood -Brain barrier : ISF
(interstitial fluid)
- *CSF
- fills space between the brain and the skull (SUBARACHNOID SPACE)
- fill space within the brain (VENTRICLES)
- secreted by CHOROID PLEXUS
What is a folded structure located within the ventricles (fluid filled spaces) of the brain
**what are the 3 layers
CHOROID PLEXUS
- Scanning EM of choroid plexus shows;
1. Villi (ridges and valleys) - Villi/folds of choroid plexus helps to increase the surface area for secretion
2. Individual epithelial cells
3 cell layers of choroid plexus
- The choroid epithelium
- The endothelium (capillary wall)
- Supporting layer
IN CHOROID PLEXUS,
1. The apical Membrane surface of choroid plexus epithelial cell faces into what?
- Apical surface is covered with?
Function? - Apical borders are joined by?
Function? - Basolateral surfaces face?
- VENTRICLE
- MICROVILLI
- expand surface area for secretion of CSF - TIGHT JUNCTIONS
- prevent diffusion through spaces between cells
4 INTERIOR OF VILLUS
- blood vessels (choroid plexus capillaries)
CSF is formed from blood (secreted by choroid plexus). Secretion requires transport across 3 layers of choroid plexus.
Identify each layer
- Outermost layer. The edges of the cells are connected by tight junctions which form a tight barrier surrounding the entire choroid plexus
- Innermost layer. Capillaries resemble the general capillaries found throughout the body
- Between 2 layers. Consist of pial cells and extracellular matrix
- CHOROID EPITHELIUM
- CHOROID ENDOTHELIUM
- endothelial layer is relatively thin; there are gaps (fenestrations) between the edges of the individual endothelial cells and pinocytotic vesicles (involved in bulk transport across the endothelium) - SUPPORTING LAYER
NO direst role in secretion
What layers of the choroid plexus have a role in formation of CSF from blood plasma
**which layer doesn’t contribute to secretion
LAYERS FOR SECRETION
- Choroid capillary endothelium
- Choroid plexus epithelium
NO SECRETION
1. Supporting layer (btw outer and inner layer)
Identify the pathways of transport through the inner layer of choroid plexus
(3)
**Movement of what is restricted
CAPILLARY ENDOTHELIUM
-most small molecules (ions, glucose, water) easily move from plasma into spaces inside the choroid plexus villi by;
- PARACELLULAR TRANSPORT
- diffusion through gaps that are btw edges of cells (fenestrations) - PINOCYTOSIS (vesicle mediated transport)
- endocytosis from the inside of the capillary and exocytosis on the outside of the capillary - TRANSCELLULAR TRANSPORT
- lipid soluble cells only
- diffusion through the endothelial cell membranes, If compound is lips soluble
- *Movement of LARGE MOLECULES (proteins) across the capillary endothelium is limited and movement of blood cells is normally prevent
- CSF has very low protein conc (NO BLOOD CELLS)
- presence of protein indicated disease/abnormal condition
Identify pathways of transport through outer layer of choroid plexus
EPITHELIAL CELL LAYER
- Tight junctions create blood-CSF barrier
- restrict diffusion of water, ions etc (only by membrane transport proteins)
- transport occurs through epithelial cell membranes (Only lipid soluble stuff can diffuse) - Transporters in epithelial cell membranes
- create CSF by secretion
- regulate composition of CSF
+ CSF and plasma composition are different
**The basolateral and apical surfaces of choroid plexus epithelial cells have important structural and functional specialization that are essential for secretion of CSF
BASOLATERAL - contain interdigitations
APICAL - contain tight junctions and microvilli. These increase surface area available for transport
**Basolateral and apical membrane contain diff transport proteins. These mediate the transport of ions, water and other small molecules
What is the normal composition of Brian extracellular fluid
The ion compositions of CSF and plasma are different
**Difference means that the CSF formation does not occur simply by passive diffusion of plasma and must involve ACTIVE TRANSPORT
- CSF and plasma are mostly Na+, Cl- and H20
- CSF has 35% less K+, Mg2 than plasma
- CSF has about 50% less Ca2+ than plasma
- CSF normally contains lower glucose and virtually no protein
In comparison of CSF and plasma
- what is more stable over time
- stability is essential for what?
- CSF composition is more stable than plasma over time
- plasma ion concentrations vary (after a meal, during strenuous exercise) - Stable CSF ion concentrations are essential for normal neuronal function
- altered ion concentrations affect membrane and action potentials, synaptic transmission
There are transport mechanism in choroid plexus epithelial cells that are responsible for creating and maintaining the blood-brain and blood-CSF barriers
**Identify the 3 most important proteins involved in distribution of specific ion transporters
Under what?
- Na+K+ ATPase
- Aquaporins
- Carbonic Anhydrase
Specific transport functions
- Apical membrane
- Na+K+ATPase (main transport)
- KCC4 (co transport)
- aquaporins (water channels) - Basolateral membrane
- Na+HCO3- (co transport)
- aquaporins - Carbonic anhydrase /intracellular compartment
- *CSF secretion is Derived by ion transport
- water follows ions by osmosis
Apical membrane transport functions
- CSF formation occurs across the apical membrane which faces into the ventricles
- Sodium is exported by activity of Na+/K+ATPase
- Chloride is moved into the ventricular space primarily by K+Cl- cotransport (KCC4) as well as anion channels permeable to both Cl- and HCO3-
- Potassium transport by K-Cl cotransport, K+ permeable channels
- Most K+ transported out across apical membrane is returned by Na-K-ATPase
- HCO3- transport by Na+ dependent transporter and diffusion through anion channels
- CSF pH regulated by HCO3- and H+ transport
- Water moves through aquaporins
Summary of apical membrane transport functions
- Consequences of apical membrane transport
- Na+ and Cl- form bulk of ions in CSF
- Low K+ in CSF - Net ion movement increases ventricle osmotic pressure
- water drawn into ventricle by high osmotic pressure - END RESULT: formation of CSF (Na+, Cl-, H20 etc) in ventricles at choroid plexus apical surface
Basolateral membrane transport functions
- Maintain intracellular ion concentrations to sustain CSF secretion
- Sodium loading by Na+HCO3- cotransport
- Chloride loading by anion exchange (Cl-/HCO3- countertransport)
- water moves through aquaporins
Intracellular functions
- Carbonic anhydrase maintains intracellular HCO3- concentration
- continuous CSF secretion requires all transport mechanisms
- loss of mechanism decreases rate of secretion
What is the major monovalent ions of CSF. What results in their net movement
Na+ AND Cl-
- the segregation of specific transporters to either the apical or basolateral membranes of the epithelial cells results in net movement of primarily Na+ and Cl- from the interior of the choroid plexus into the ventricles
- the transport of these ions into the ventricles raises the osmotic pressure within the ventricles and driving osmosis
Transport mechanisms for CSF secretion
-transport of divalent ions
- Choroid plexus transports many other substances
- DIVALENT CATIONS (Ca2+, Mg2+), glucose, nucleosides, vitamins - Entry into CNS requires;
- specific membrane transporters in apical and basolateral membranes
OR
- high lipid solubility
**distinct transport mechanisms for these ions must be present in basolateral and apical membranes
- What does the rate of CSF secretion depend on?
- What drug will reduce the rate of CSF secretion
- Inhibitor of NaKATPase
- Inhibitor of carbonic anhydrase
- The rate of CSF secretion depends on the coordinated activity of all ion transporters in the apical and basolateral membranes
- A drug which inhibits any transporter involved in ion traffic across the choroid plexus epithelium will reduce the rate of CSF secretion
Drugs affecting CSF formation:
- OUABAIN ; inhibitor of Na+K+ATPase
- ACETAZOLAMIDE; carbonic anhydrase inhibitor
CSF and ISF
- CSF secreted by choroid plexus fills ventricles
- ISF fills extracellular spaces
- No tight junctions between ependymal cells lining ventricles
- NO BARRIER; free exchange btw ventricle, extracellular spaces
- ISF and CSF compositions are virtually identical - Choroid plexus forms about 60% of CSF
- surgical removes reduces rate of CSF formation by about 60% - CNS CAPILLARIES form remaining CSF
- capillary secretion contributes to ISF
+ ISF exchanges with fluid in ventricles
The choroid plexus accounts for roughly 2/3rd of the CSF production.
**The remainder of the CSF is formed by?
CNS capillary endothelial cells
Structural specializations
- CNS CAPILLARIES are secretory structures
- luminal, abluminal membranes contain transporters - TIGHT JUNCTIONS create blood-brain barrier
- NO pinocytosis
- No paracellular transport (no fenestrations)
The structural and functional specializations of the brain capillaries endothelium are induced by ?
- TROPHIC FACTORS secreted by astrocytes induce capillary specialization
- astrocyte “foot processes” surround CNS capillaries
- astrocytes do not directly contribute to blood brain barrier (no tight junctions)
What are the similar structures in the endothelial versus epithelial cells
- Similar transport functions in CNS capillary endothelial cells and choroid plexus epithelial cells
1. ABLUMINAL membrane of endothelial cells = APICAL membrane of epithelial cells
2. LUMINAL membrane of endothelial cells = BASOLATERAL membrane of epithelial cells
What are the consequences and significance of Blood-brain and blood-CSF barriers
- Blood-brain and blood-CSF barrier protect CNS
- keep damaging/toxic substances out
- maintain stable extracellular environment - BUT blood-brain and blood-CSF barriers also exclude potentially beneficial substances (e.g drugs)
- e.g, dopamine vs L-DOPA for treatment of Parkinson’s disease - For many substances, entry into brain (relative extraction) is strongly correlated with lipid solubility (oil/water partition coefficient)
- Drugs with high lipid solubility easily enter CNS
- Drugs with LOW LIPID SOLUBILITY are largely excluded from CNS
- Some compounds enter CNS FASTER than expected from lipid volubility
- substrates for transport into CNS
- transport increases entry into CNS - Some compounds enter CNS SLOWER than expected from lipid solubility
- substrates for transport out of CNS
- transport decreases entry into CNS
Identify the problem
- disturbance of the normal fluid balance between different fluid compartments
- increased volume in one of these compartments due to increased water content
Identify all types
EDEMA
- Vasogenic; blood vs interstitial space
- Osmotic: blood vs interstitial space
- Hydrostatic: blood vs interstitial space
- Cytotoxic: extracellular vs intracellular space
- Interstitial: ventricular vs interstitial space
Identify edema type
- BLOOD-BRAIN BARRIER DISRUPTION
- head injury, hemorrhage, infarct, infection (meningitis) - Plasma proteins leak into interstitial space, raise ISF osmotic pressure
- CSF protein concentration elevated - Water drawn from plasma into interstitial space
- increased interstitial volume raises intracranial pressure (ICP)
VASOGENIC EDEMA
Identify problem
- Compress vasculature, decrease blood flow to brain
- Brain shift/herniation
ELEVATED ICP
Identify edema type(s)
- Plasma osmolarity too low (hyponatremia, water intoxication)
- water is drawn across blood-brain, blood-CSF barriers into CNS - Malignant hypertension (sudden, large increase in blood pressure)
- high blood pressure forces fluid from plasma across blood-brain, blood-CSF barriers into CNS
- OSMOTIC EDEMA
- HYDROSTATIC EDEMA
***Elevated intracranial pressure
Identify edema type
- CELLULAR ENERGY (ATP) DEPLETION
- caused by interruption of normal blood/oxygen supply - Failure of active transport, loss of osmotic balance across cell membrane
- intracellular osmotic pressure increases, water drawn into cells, cell volume expands
CYTOTOXIC EDEMA
Identify edema type
- ABNORMAL CSF FLOW
- obstructed flow between ventricles or outflow through arachnoid villi, over-secretion of CSF - Increased pressure in ventricles forces CSF into brain interstitial space
- fluid accumulates in interstitial space, ventricles expand
INTERSTITIAL EDEMA
What part of the ear have key functions in auditory and vestibular senses
INNER EAR
- specialized sensory receptors called hair cells transducer both auditory and vestibular sensory stimuli into electrical signals
- differences in the organs containing the hair cells cause vestibular receptor cells to respond to linear and rotational acceleration (whereas auditory receptor cells respond to sound pressure waves)
Describe how the sensory transduction processes in auditory vestibular hair cells
Vestibular hair cells
- Hair cells are ciliated
- cilia are oriented from short to tall - Specialized APICAL and BASOLATERAL membranes
- Apical membrane:
- sensory transduction zone
- one kinocilium (vestibular hair cells only), several stereocilia
* *Auditory hair cells are similar to vestibular hair cells except they lack a kinocilium - Basolateral membrane;
- resting potential
- synaptic transmission zone (synapse with CN VIII afferents)
- *Vestibular hair cells have specialized apical and basolateral membranes
- *The cilia of both auditory and vestibular hair cells are arranged from shortest to tallest
Sensory transduction in hair cells
-hair cells transducer movement (bending of their cilia) into a change in membrane potential
Hair cell function What direction during -depolarization -hyperpolarization -no change
- Receptor potential (graded) created by bending cilia
- Directionally sensitive
- towards kinocilium/tallest stereocilium; DEPOLARIZATION
- away from kinocilium/tallest stereocilium; HYPERPOLARIZATION
- perpendicular to kinocilium/tallest stereocilium: NO CHANGE
In sensory transduction in hair cells,
- What does bending of cilia do to ion channels?
- Bending of cilia pulls open mechanically gated ion channels
- channels are located in stereocilia
- mechanically linked to adjacent cilium - Mechanically-gated CATION channel
- bending towards kinocilium pulls channels open
- bending away from kinocilium closes channels
- K+/Ca2+ permeable (cations)
Sensory transduction in hair cells
- Bathing apical membrane
- Bathing basolateral membrane
- Driving force for K+
- Basolateral membrane creates what resting potential
- What allow inward current flow
- Influx of positive charge creates what?
- Extracellular fluid (endolymph) bathing APICAL membrane:
- high K+, low Na+ (atypical extracellular fluid: resembles intracellular fluid) - Extracellular fluid (perilymph) bathing BASOLATERAL membrane:
- low K+, high Na+ (standard extracellular fluid) - Driving force for K+:
- INWARD ACROSS APICAL MEMBRANE
- outward across basolateral membrane - Basolateral membrane creates NEGATIVE resting potential
- Opening of mechanically-gated channels on stereocilia allows inward current flow (K+ and Ca2+)
- Influx of positive charge creates capacitive current which DEPOLARIZES basolateral membrane
DO Hair cells generate action potentials
Describe terminal release
- Depolarization of basolateral membrane opens voltage-gated Ca2+ channels
- Ca2+ influx triggers transmitter release
- No voltage-gated Na+ channels in hair cells
- no action potentials in hair cells - Hair cells DO NOT generate action potentials
- transmitter release is graded and proportional to membrane potential - HAIR CELLS RELEASE GLUTAMATE AT REST
- bending towards kinocilium INCREASES rate of release
- bending away from kinocilium DECREASES rate of release - Afferent firing is proportional to glutamate release
Vestibular hair cells are contained in what 2 types of sensory organ
**Auditory cells are contained where?
- OTOLITH ORGANS (utricle, saccule)
- hair cells respond to LINEAR ACCELERATION - SEMICIRCULAR CANALS (ampullae)
- hair cells respond to ANGULAR ACCELERATION
- *AUDITORY HAIR CELLS are contained in the ORGAN OF CORTI
- hair cells respond to SOUND PRESSURE WAVES
Identify the sensory organ
- *Contain sensory epithelium (MACULA) composed of:
- vestibular hair cells
- support cells
- gelatinous layer
- fibrous layer containing otoconia (otoliths)
OTOLITH ORGANS (Utricle, Saccule)
- Otoconia are heavier than surrounding fluid
- Head tilt changes relative direction of gravitational acceleration and head (OTOLITH)
- otoconia shift relative to the sensory epithelium
- shear force bends hair cell cilia - Any other head movement which creates LINEAR ACCELERATION (or deceleration) also induces bending of cilia
What is the hair orientation in OTOLITH organs
- Orientation
- adjacent hair cells have similar orientation
- hair cell orientation changes gradually across much of macular, but abruptly at striola - All potential directions of linear acceleration are represented
- Utricule most sensitive to acceleration in horizontal plane
- Saccule most sensitive to acceleration in the Sagittarius plane - Maculae on each side of the head are paired (mirror images)
- LINEAR ACCELERATION in any direction always depolarizes one subpopulation of hair cells, but hyperpolarizes a second subpopulation
Identify sensory organ
- Each canal contains swelling (ampulla)
- ampulla contains a sensory epithelium (CRISTA) - Hair cell cilia extend into gelatinous mass (cupula)
- Canals are filled with fluid (endolymph)
SEMICIRCULAR CANALS
- Because of inertia and circular container holding endolymph, during ANGULAR ACCELERATION of head
- endolymph lags behind canal
- cupula and cilia embedded in it are bent - Hair cells within each ampulla share same orientation
- Semicircular canals are paired
7.
- How is each semicircular canal paired
- Each semicircular canal is paired with a second canal in same plane
- left vs right horizontal
- left anterior vs. right posterior
- right anterior vs left posterior - Rotation of head causes opposite changes hair cell membrane potentials and afferent firing rates in paired semicircular canals
* *Hair cells in the canal towards which the head is rotating are depolarized - Semicircular canals respond to angular acceleration, not velocity
- Output adapts during constant VELOCITY rotation
Adaptation during constant velocity rotation
- At beginning of rotation to left, endolymph lags
- hair cells to LEFT are depolarized, afferents on LEFT increase firing rate
- hair cells to RIGHT are hyperpolarized, afferents on RIGHT decreases firing rate - If rotation continues at constant velocity, friction between endolymph and canal gradually imparts motion to the fluid
- as endolymph begins to rotate, bending of hair cell cilia decreases
- as receptor potentials (both depolarizing and hyperpolarizing) decrease, afferent firing rates return towards unstimulated level - With continued rotation, endolymph eventually reaches same velocity as head
- cilia are no longer bunt, hair cell membrane potential and afferent firing rates return to rest (unstimulated level) - If rotation suddenly stops;
- endolymph keeps moving (inertia)
- hair cell cilia Bend in opposite direction
- afferent firing changes in opposite direction
- subjective perception is rotation in opposite direction
Auditory function overview
**How does auditory sensory transduction occur?
- Auditory sensory transduction occurs through bending of cochlear hair cell cilia (inner ear)
- Outer, middle ear have important roles in processing and transmitting sound to inner ear
**vibration - pressure waves -(air)- ear - vibration (basilar membrane); bend hair cell cilia
Outer ear function (3)
- AMPLIFICATION ; outer ear acts as funnel and resonator (10 dB boost)
- LOCALIZATION; pinna aids in determining elevation
- VERTICAL sound localization - CONDUCTION DEAFNESS:
- obstruction in auditory canal decreases conduction to middle ear
- air conduction is impaired, but bone conduction is normal
Middle ear function (4)
-what is resistance to movement
- IMPEDANCE MATCHING
- impedance = resistance to movement
- impedance of fluid (perilymph) is greater than air, so more force is required to move fluid - 2 features of middle ear increases force
- surface area difference between tympanic membrane and oval window (20:1)
- bones of middle ear function as lever - RESULT; low force, large distance movements of tympanic membrane are converted to high force, small distance movements to oval window
- Impaired function of middle ear produces CONDUCTION DEAFNESS
- damage to tympanic membrane
- fluid in middle ear (infection, allergy etc)
- otoslerosis (abnormal bone growth in middle ear)
Inner ear function: overview
- At border of middle and inner ears, pressure waves are converted into fluid waves
- Fluid waves distort the basilar membrane
- Distortion (movement) of basilar membrane causes bending of auditory hair cell cilia, hair cell receptor potential, and change in afferent nerve firing)
Basilar membrane function
- Function is easiest to visualize if cochlea is uncoiled
- Basilar membrane is narrower and stiffer at one end, wider and looser at opposite end
- Perilymph (fluid) is incompressible
- Inward movement of oval window causes downward movement of basilar membrane
- Downward movement of basilar membrane is relieved by outward movement of round window
Basilar membrane function
- Oval window
Frequency changes
- oval window moves in and out in sync with peaks and troughs of sound waves
- causes rapid, oscillating deformation of basilar membrane (traveling wave)
- because of physical differences along basilar membrane, it resonates at different frequencies along its length - HIGH FREQUENCY sounds cause large deformation near base of cochlea
- large amplitude movement of basilar membrane at base dissipates energy of fluid wave
- traveling wave dies out - MEDIUM FREQUENCY sound created fluid wave which travels further along the basilar membrane
- resonant frequency of basilar membrane arches sound frequency between base and apex
- large amplitude movements of middle region of basilar membrane dissipate energy
- traveling wave dies out - Fluid waves created by LOW FREQUENCY sound travel to apex before dissipating
- RESULT: basilar membrane is tuned for maximal movement at specific locations
Auditory hair cell function: sensory transduction
- Hair cell cilia contract tectorial membrane
- Hair cell sonata are embedded in basilar membrane
- Tectorial membrane moves up and down with basilar membrane e
- PIVOT POINTS for tectorial and basilar membrane are on different axes
- shearing created by movement of the two membranes (unequal lateral displacement with pivot)
- hair cell cilia are bent
Neuronal Integration,
Basic patterns of organization
- Patterns of organization
- Nervous system is composed of many individual systems
- Large neural systems are built from smaller units
- These small units consist of a few basic patterns of neuronal connection - Information encoding
* Frequency coding
- conversion from amplitude modulated (graded potentials) to frequency modulated signals (all or none potentials)
The basic patterns of neuronal connectivity functions to support different concepts
- Identify
- axon from single neuron branches many times, forming synaptic contacts with multiple target cells
- Allows recruitment of many cells, and promotes the smooth coordination of effectors by amplification of the signal
- common at input stages
**Give example
DIVERGENCE
E.g Spinal reflexes (flexion reflex; flexor and crossed extensor)
The basic patterns of neuronal connectivity functions to support different concepts
- Identify
- a single target cell integrates diverse information from many presynaptic neurons
- common in the output stages of the N.S
- consecutive stages allow a single neuron to intergrate many sources of information into a final output
CONVERGENCE
E.g
Spinal Interneuron output is influenced by converging inputs
What fine tune signaling in neuronal systems
**what are the 5 types
INHIBITORY CIRCUITS
- Most neurons in CNS are spontaneously active
- constant stream of excitatory synaptic input causes firing
- INHIBITORY CIRCUITS suppress firing, fine tune firing patterns
Types
- Presynaptic inhibition
- Disinhibition
- Lateral inhibition
- Feedback inhibition
- Feedforward inhibition
There are 5 types of inhibitory circuits
*Identify
- Can be used to gate information flow
- to inhibit a reflex
- to inhibit pain sensation
- PRESYNAPTIC INHIBITION
E.g
Descending axons can inhibit the transmission of information from somatosensory receptors to follower neurons, gating the transmission of sensory information
There are 5 types of inhibitory circuits
- Identify
2. Inhibition of an inhibitory neuron - can be postsynaptic or presynaptic
- ha net exciting effect (analogous to double - negative in grammar: double-negative = positive)
- DISINHIBITION
There are 5 types of inhibitory circuits
- Identify
3. Interneurons create inhibitory receptive field adjacent to excitatory receptive field
FUNCTION: enhance contrast
- LATERAL INHIBITION
**SURROUND INHIBITION: variation of lateral inhibition, inhibitory receptive field completely surrounds excitatory receptive field
**CONTRAST ENHANCEMENT by lateral inhibition
There are 5 types of inhibitory circuits
- Identify
4. Requires a RECURRENT PATHWAY - useful for self-regulation, to control duration of activity in a circuit
- found throughout CNS
- FEEDBACK INHIBITION
There are 5 types of inhibitory circuits
*Identify
5. Required a DIVERGENT PATHWAY
- useful for controlling antagonistic pathways
E.g reflex pathways controlling antagonistic muscles
- FEEDFORWARD INHIBITION
What do reverberating circuit allow for
**what can cause seizures
- Reverberating circuits allow for persistent activity in a system:
- can allow a response to outlast a stimulus
- can allow information to be stored (as a short term memory) - Runaway excitation in these circuits in the brain can cause seizures
- local feedback inhibitory connections normally prevent runaway excitation
Identify concept
- Rhythmically alternating activity can be created by several types of neural circuits
- pattern generators in spinal cord produce rhythmic, alternating movements during walking
CENTRAL PATTERN GENERATORS
E.g alternating activity produced by reciprocal inhibitory connections
Information encoding
**identify all 4 zones
All neuronal cells have the same elements
- Input zone
- INTEGRATION (TRIGGER) zone
- Conduction zone
- Output zone
Information encoding
Identify the zone
- signals consist of GRADED POTENTIALS (synaptic or receptor potentials)
- graded potential encode signal strength by amplitude (amplitude modulation)
- INPUT ZONE
Information encoding
Identify the zone
2.
Graded potentials are converted to all-or-none potentials (action potentials)
- signal strength becomes encoded by FREUENCY MODULATION (frequency coding)
- conversion from amplitude modulated to frequency modulated signals occurs in this zone
INTERGRATION ZONE (trigger zone) **Voltage -gated ion channels present in integration zone affect conversion of amplitude to frequency modulated signals
What happens when integration zone contains only voltage- gated sodium and potassium channels
If integration zone contains only voltage-gated Na and K channels;
Action potential frequency is STABLE OVER TIME, and is directly proportional to amplitude
What happens when integration zone also contains T-type Voltage -gated calcium channels
BURST FIRING occurs over a range of subthreshold membrane potentials
- T-type calcium channels activate at membrane potentials below action potential THRESHOLD
- T-type calcium channels are open TRANSIENTLY; inactivate rapidly
How does T-type calcium channels affect central pattern generators
- Rhythmically alternating activity created by a pattern generator circuit
- T-type calcium channels in neurons A and B can make rhythmic activity self-sustaining
- SOme antiepileptic drugs inhibit T-type calcium channels
- e.g ethosuximide (absence seizures)
- What happens if integration zone also contains SLOW calcium-activated potassium channels
- What happens if integration zone also contains FAST calcium-activated potassium channels
- FIRING RATE GRADUALLY ADAPTS
- SPIKE REPOLARIZATION AND UNDERSHOOT ARE ENHANCED
- *More rapid spike repolarization causes quicker recovery from inactivation for voltage-gated sodium channels
- decreased duration of absolute refractory period
- faster rate of action potential firing
