Anatomy Flashcards
What does the telencephalon form?
Cerebral hemispheres
What does the diencephalon form?
Thalamus, hypothalamus
What does the mesencephalon form?
Midbrain
What does the metencephalon form?
Pons, cerebellum
What does the myelencephalon form?
Medulla oblongata
What is the brainstem?
Midbrain, pons and medulla oblongata
What are the most numerous cells in the CNS?
Glial cells
What roles are astrocytes involved in?
Support, maintaining the BBB, environmental homeostasis
What do oligodendrocytes produce?
Myelin in the CNS (not PNS)
Describe oligodendrocytes
Numerous branches that extend to produce internodes of myelin around axons. Round nucleus
What are microglia?
Cells of similar lineage to macrophages (haemopoietic origin)- immune monitoring and antigen presentation
What is the appearance of microglia in a resting state?
Elongated nucleus and have a number of short spiny cell processes
What is the appearance of microglia in an activated state?
Become rounder and take on a similar appearance to macrophages
What can activate microglia?
Bacteria infection
What are the 4 major types of glial cells?
Astrocytes, oligodendrocytes, microglia, ependymal cells
Describe ependymal cells
Ciliated cuboidal/columnar epithelium that lines the ventricles
What is a folium?
Equivalent to a gyrus in the cerebral hemispheres
What makes up the grey matter?
Huge numbers of neurons, cell processes, synapses and support cells
What makes up the white matter?
Medullary centre- axons (most myelinated) and their support cells
Where is the parietal lobe located?
Posterior to central sulcus, superior to lateral sulcus, and anterior to a line from parieto-occiptal sulcus to the preoccipital notch
Where is the occipital lobe located?
Posterior to a line from the parieto-occipital sulcus to the preoccipital notch
Where is the temporal lobe located?
Inferior to the lateral sulcus and posteirorly by a line from the parieto-occipital sulcus and the preoccipital notch
What role does the insular lobe have?
Patient’s experience of pain
What are the 3 meningeal layers?
Dura mater
Arachnoid space
Pia mater
What is contained within the arachnoid mater?
Subarachnoid space containing CSF
Where is the enteric nervous system found?
In digestive system from oesophagus to rectum
Where are the neurons of the ENS found?
Largely in two plexuses in the walls of the gut (myenteric plexus between outer layers of smooth muscle, submucosal plexus in submucosa)
What is the T4 spinal nerve segment identified by?
Male nipple
What is the T10 spinal nerve segment identified by?
Umbilicus
What does the C2-4 segment supply?
Posterior scalp, neck and shoulder
What does the C5-T1 segment supply?
Upper limb
What does the L2-Co1 segment supply?
Lower limb, gluteal region and perineum
What are nerve plexuses?
Networks of intertwined anterior rami
What makes up the cervical plexus?
C1-4 anterior rami
What does the cervical plexus supply?
Posterior scalp, neck wall and diaphragm
What makes up the brachial plexus?
C5-T1 anterior rami
What does the brachial plexus supply?
Upper limb
What does the lumbar plexus supply?
Lower limb
What makes up the lumbar plexus?
L1-4 anterior rami
What makes up the sacral plexus?
L5-S4 anterior rami
What does the sacral plexus supply?
Lower limb, gluteal region and perineum
What is the myotome of each spinal nerve?
The skeletal muscles supplied with motor innervation by both the anterior and posterior ramus of that spinal nerve
Where does the sympathetic tract exit the spinal cord?
T1-L2 spinal nerves
Where do sympathetic fibres synapse in the CNS?
Lateral horn of grey matter
What structure does the presynaptic sympathetic axon pass through from the spinal nerve to reach the paravertebral ganglion?
Rami communicans
What type of axons come from the anterior horn of the spinal cord?
Motor axons
What type of axons come from the posterior horn of the spinal cord?
Sensory axons
What is the tapered cone-shape in which the spinal cord terminates?
Conus medullaris
What does the conus medullaris continue as?
A thin connective tissue cord called the filum terminale
What is the filum terminale anchored to?
The dorsum of the coccyx
What is the ribbon of tissue on the lateral aspects of the cord which hold it in the canal?
Denticulate ligament
What is the denticulate ligament formed from?
Pial and arachnoid tissue
Where does the denticulate ligament attach?
To the dura at points along the length of the cord
What is the white matter of the spinal cord conventionally described as being made up of?
Posterior, lateral and anterior fasciculi
What is the grey matter of the spinal cord divided into?
Left and right posterior and anterior horns
What parts of the grey matter surround the central canal?
Dorsal and ventral commisures
What is found at spinal segments T1 to L2 which contains the preganglionic sympathetic neurons?
A smaller lateral horn
What is the arterial supply of the spinal cord?
Three major longitudinal arteries
Segmental arteries
Radicular arteries
What are the three major longitudinal arteries that supply the spinal cord?
One anterior and two posterior that originate from the vertebral arteries. Run along length of the cord
What are the segmental arteries derived from?
Vertebral, intercostal and lumbar arteries
Where do the radicular arteries travel?
The dorsal and ventral roots
Describe the venous drainage of the spinal cord
Follows a similar pattern to the supply, with both longitudinal and segmental veins
What is the epidural space?
The space between the dura and bone in the spinal canal
What does the epidural space contain?
Adipose tissue and the anterior and posterior epidural venus plexuses
What does the dorsal pathway control?
Fine touch and conscious proprioception (particularly from the upper limb)
Where do the fibres in the dorsal pathway cross?
Medulla
What does the STT control?
Pain, temperature, deep pressure
What does the corticospinal tract form on the anterior surface of the medulla?
Visible ridges referred to as pyramids- hence pyramidal tract
What can a CVA of the internal capsule result in?
A lack of descending control of the corticospinal tract which results in spastic paralysis with hyperflexion of the upper limbs- referred to as decorticate posturing
What is a general rule regarding fibres originating from the pons and medulla?
Fibres from pons facilitate extensor movements and inhibit flexor movements, while those from medulla to the opposite
Where is the cerebellum located?
Posterior and inferior cerebral hemispheres
What is the cerebellum attached to the brainstem by?
3 stalks termed peduncles:
Superior, middle and inferior cerebellar peduncle
What are the 3 layers of the cerebellar cortex?
Molecular layer (outer) Purkinje cell layer (middle) Granular layer (inner)
What type of neuron projects to the cerebellum?
Afferent
Where do the important afferents to the cerebellum mainly arrive from?
Spinal cord (somatic proprioceptors and pressure receptors) Cerebral cortex (via pons) Vestibular apparatus (via vestibular nuclei)
Where do the afferent neurones mainly project to in the cerebellum?
Granule cell layer
What is the only output from the cerebellum?
Via the axons of Purkinje cells which mainly synapse on neurons of deep cerebellar nuclei- contribute to motor tract function of brainstem/cord
Where do most efferent axons of the deep cerebellar nuclei cross and synapse?
Midline and synapse in the thalamus- fibres than sent to the motor cortex
Cerebellar hemispheres influence what side of the body?
Ipsilateral
What can a unilayeral hemispheric lesion result in?
Disturbance of coordination in limbs. Can result in intention tremor and unsteady gait in the absence of weakness or sensory loss
What does bilateral cerebellar dysfunction result in?
Slowed, slurred speech, bilateral incoordination of arms and a staggering, wide based gait (cerebellar ataxia)
What does acute alcohol exposure cause in the cerebellum?
Bilateral cerebellar hemisphere dysfunction and presents with cerebellar ataxia
What will a midline cerebellar lesion cause?
Disturbance of postural control, but preserved limb coordination
What are the functions of the basal ganglia?
Facilitate purposeful movement
Inhibit unwanted movements
Role in posture and muscle tone
What are the components of the basal ganglia?
Striatum Corpus striatum Lenticular nucleus Subthalamic nucleus Substantia nigra
What makes up the lenticular nucleus?
Putamen
Globus pallidus
What makes up the corpus striatum?
Caudate nucleus
Putamen
Globus pallidus
What makes up the striatum?
Caudate nucleus, putamen
What is the pathology of Parkinson’s?
Degeneration of dopaminergic neurons of the substantia nigra
How do the basal ganglia work with the motor cortex to enhance normal movement?
There is a direct pathway between them which enhances outflow of the thalamus, thusly enhancing the desired movement
What issues the command to move?
Pyramidal neurones (under voluntary control)
How do the basal ganglia work with the motor cortex to suppress unwanted movement?
An indirect pathway inhibits the outflow of thalamus
What side of the body do unilateral lesions of the basal ganglia affect?
Contralateral
What do lesions of the basal ganglia cause?
Changes in muscle tone
Dyskinesias: Tremor, chorea, myoclonus
What is the pathology of Huntington’s?
Progressive degeneration of the basal ganglia and cerebral cortex
What do the extrinsic back muscles do?
Move the upper limb
What are the main extrinsic back muscles?
Trapezius
Lattimus dorsi
Levator scapulae
Rhomboids (major and minor)
What do the intrinsic back muscles do?
Maintain back posture and move the spine
What are the main intrinsic back muscles?
Erector spinae (superficial) Transversospinalis (deep)
What makes up erector spinae?
3 vertically arranged muscle groups located just lateral to the spine
What do all the erector spinae muscle fibres attach inferiorly by?
A common tendon to the sacrum & the iliac crest
What do individual erector spinae muscle fibres attach superiorly to?
Via a tendon either:
a rib (between angle and tubercle)
a transverse process of a vertebra
a spinous process of a vertebra
Where is transversospinalis located?
Within the deep grooves between the transverse and spinous processes
Where do the inidividual muscle fibres of transversospinalis attach between?
A vertebra and the skull
A vertebra and a rib
One vertebra and another
A vertebra and the sacrum
What is extension of the spine a function of?
The intrinsic back muscles
What is spine flexion a function of?
Psoas major and rectus abdominus
What are the functions of the spine?
Support weight of the head and trunk in upright posture
Protect spinal cord (and nerves)
Allow movements
What are the pain signals of facet joints and IV discs transmitted via?
Posterior rami
What do the facet joints join?
Articular processes of 2 adjacent vertebrae
Where along the spine will you not find IV discs?
Between C1-2 and fused sacrum and coccyx
What ligaments run along the spine?
Ligamentum flavum Posterior longitudinal ligament Anterior longitudinal ligament Supraspinous ligament Interspinous ligament
What does the ligamentum flavum connect?
Adjacent laminae posterior to spinal cord
Where do the anterior and posterior longitudinal ligaments attach?
To the anterior and posterior aspects of all vertebral bodies and intervertebral discs respectively
What do the anterior and posterior longitudinal ligaments prevent?
Over extension and over flexion of the spine respectively
What does the supraspinous ligament connect?
Tips of spinous processes
What does the interspinous ligament connect?
Superior and inferior surfaces of adjacent spinous processes
What do all cervical vertebrae have in the transverse process?
A foramen for vertebral arteries
What does C1 have instead of a body or spinous process?
An anterior and posterior arch
Where are the atlanto-occipital joints between?
The occipital condyles and the superior articular facets of the atlas
What type of joints are the atlanto-axial joints?
Synovial (3)
Where are the atlanto-axial joints located?
2 between the inferior articular facets of atlas and superior articular facets of axis
1 between anterior arch of atlas and odontoid process of axis
What are the main movements of the atlanto-axial joints?
Rotations
What foraminae are present in the sacrum instead of intervertebral foraminae?
Anterior and posterior sacral foraminae
Where is local anaesthetic injected in caudal anaesthesia to anaesthetise the sacral spinal nerve roots of the cauda equina?
Sacral hiatus
Where is the spinal cord located?
From C1-L2. Continuous with medulla oblongata at foramen magnum
What is located in the L1 dermatome?
Groin
What is located in the L2 dermatome?
Anterior thigh
What is located in the L3 dermatome?
Anterior knee
What is located in the L4 dermatome?
Medial malleolus
What is located in the L5 dermatome?
Dorsum of foot
What is located in the S1 dermatome?
Heel
What is located in the S2 dermatome?
Posterior knee
What is located in the S3 dermatome?
Buttock
What is located in the S4 dermatome?
Perineum
What is located in the S5 dermatome?
Perianal skin
What happens when a dermatome is tested for sensory function (T10 example)?
Stimulation in anterior aspect of right T10 dermatome
AP generated by receptors in segment
AP continues along axons to anterior ramus
Then to T10 spinal nerve
Then to T10 posterior root
Then to T10 posterior rootlets
Then to posterior horn of spinal cord
What are the spinal nerve root levels of the femoral nerve?
L2,3,4
What supplies the neck and scalp skin posteriorly?
Posterior rami of spinal nerves C2-8
What supplies the skin of the neck anterolaterally?
Named sensory branches of the cervical plexus (anterior rami of C1-4 spinal nerves)
Describe lesser occipital nerve
Spinal nerve C2
Skin posterior to external ear
Describe great auricular nerve
Spinal nerve C2,3
Skin over the angle of the mandible & some of the external ear
Describe transverse cervical
Spinal nerve C2,3
Skin over anterior neck
Describe the supraclavicular nerves
Spinal nerve C3,4
Skin over the clavicle and shoulder tip
What supplies the upper anterolateral trunk wall?
Intercostal nerves (anterior rami of spinal nerves T2-11)
What supplies the lower anterolateral trunk wall?
Iliohyogastric & the iliolingual nerves (formed from bifurcation of anterior ramus of L1 spinal nerve)
What supplies the T12 dermatome of the trunk?
The subcostal nerve (anterior ramus of T12 spinal nerve)
What are the posterior parts of the back dermatomes supplied by?
Posterior rami
Describe the axillary nerve
C5,6
Badge patch
Describe the supraclavicular nerves
C3,4
Anterior arm, shoulder
Describe the radial nerve
C5,6,7,8,T1
Lateral arm
Posterior hand
Describe the cutaneous branch of the musculocutaneous nerve
C5,6,7
Inferolateral arm
Describe the ulnar nerve
C7,8,T1
Medial hand
Describe the median nerve
C5,6,7,8,T1
Lateral hand
What supplies the anatomical snuff box?
Cutaneous branches of the radial nerve
What happens when a named nerve is tested for sensory function (femoral nerve function)?
Stimulation in area innervated by femoral nerve
AP generated by receptors in that area (L2 dermatome)
AP continues along axons weaving through lumbar plexus
AP continues to L2 anterior rami
AP continues to L2 spinal nerve
AP continues to L2 posterior root
AP continues to L2 posterior rootlets
AP continues into posterior horn of spinal cord
What do the cervical plexus motor axons supply?
Neck postural and strap muscles
Diaphragm
What do the brachial plexus motor axons supply?
Muscles of the upper limb
Extrinsic back muscles
What do the T2-L3 motor axons supply?
Postural back muscles
Intercostal muscles
Anterolateral abdominal wall muscles
Through what nerves are the anterolateral abdominal wall muscles supplied?
Thoracoabdominal, subcostal, iliohypogastric and iliolingual nerves
What do the lumbosacral plexus motor axons supply?
Lower limb muscles
Perineal skeletal muscles
What innervates the muscles of facial expression?
CNVII
What innervates the muscles of mastication?
CNV3
What innervates the muscles of the tongue?
CNXII
What innervates the muscles of the soft palate?
CNX/pharyngeal plexus
What innervates neck postural muscles?
Posterior rami of cervical spinal nerves
What innervates the strap muscles?
Cervical plexus
What innervates the diaphragm?
Phrenic nerve (C3,4,5)
What innervates sternocleidomastoid & trapezius?
CNXI
What innervates the muscles of the pharynx?
CNX
What innervates the intrinsic muscles of the larynx ?
CNX
What inervates the intercostal muscles?
Intercostal nerves
What innervates the anterolateral abdominal wall muscles?
Thoracoabdominal nerves
What innervates erector spinae and transversospinalis groups?
Posterior rami of spinal nerves
What innervates deltoid and teres minor?
Axillary nerve
What innervates the anterior compartment of the arm?
Musculocutaneous nerve: C5,6,7
Biceps brachii
Brachialis
Coracobrachialis
What innervates the anterior compartment of the forearm and hand muscles?
Median nerve: (C5), C6,7,8,T1
Muscles of the anterior compartment of forearm:
The pronator muscles (Teres & Quadratus)
Flexor carpi radialis
Palmaris longus
Flexor digitorum superficialis
Lateral half of flexor digitorum profundus
Flexor pollicis longus
Muscles of the hand:
Thenar muscles
Lumbricals 1&2
What dos the radial nerve innervate in the upper limb (motor)?
Muscle of the posterior compartment of arm: Triceps brachii
Muscles of the posterior compartment of forearm: Brachioradialis
Supinator
ALL the extensors of the carpus & digits
Abductor pollicis longus
What does the ulnar nerve innervate in the upper limb(motor)?
Muscles of the anterior compartment of forearm:
Flexor carpi ulnaris
Medial half of flexor pollicis longus
Adductor pollicis
Muscles of the hand:
Hypothenar muscles, Lumbricals 3&4
& ALL the interossei (dorsal & palmar)
What does the femoral nerve innervate in the lower limb (motor)?
Quadriceps femoris, sartorius and pectineus
What does the sciatic nerve innervate in the lower limb (motor)?
Tibial part: L4-S3 muscles of the posterior compartment of leg: true hamstrings - semimembranosus semitendinosus long head of biceps femoris muscles of the posterior compartment of leg: gastrocnemius soleus plantaris popliteus tibialis posterior flexors of the digits (digitorum & hallucis longus) muscles of the sole of the foot: ALL intrinsic muscles of the sole of the foot common fibular part: L4-S2 short head of biceps femoris
What does the obturator nerve (L2-4) innervate in the lower limb (motor)?
All of the medial compartment of thigh All adductors (Brevis/longus/magnus) and gracilis
What does the common fibular nerve innervate in the lower limb (Motor)
Superficial fibular branch:
muscles of the lateral compartment of leg:
fibularis longus & brevis
Deep fibular branch: muscles of the anterior compartment of leg: fibularis longus & brevis muscles of the dorsum of the foot: extensor digitorum brevis (EDB) extensor hallucis brevis (EHB)
What is tested in shoulder joint movement?
Abduction: C5 deltoid
Adduction: C7 Pectoralis major and latissumus dorsi
What is tested in elbow joint movement?
Flexion: C5,6 Biceps brachii
Extension: C7,8 triceps brachii
Pronation: C6 pronator teres and quadratus
Supination: C8 supinator
What is tested in wrist joint movement?
Flexion: C6,7 (flexors of carpus)
Extension: C7,8 (extensors of carpus)
What is tested in finger joint movement?
Flexion: C8 (flexors of digits)
Extenson: C7 (extensors of digits)
Abduction: T1 (palmar interossei)
Adduction: T1 (dorsal interossei)
What is tested in hip joint movement?
Flexion: L2,3 (psoas major)
Extension: L5,S1 (gluteus maximum and hamstrings)
What is tested in knee joint movement?
Flexion: L5,S1 (hamstrings)
Extension: L3,4 (quadriceps)
What is tested in ankle joint movement?
Dorsiflexion: L4,5 (tibialis anterior)
Plantar flexion: S1,2 (gastrocnemius/soleus)
Inversion: L4 (tibialis anterior and posterior)
Eversion: L5,S1 (fibularis longus and brevis)
What happens when a spinal nerve myotome is tested for motor function (L3 spinal cord segment)?
APs generated by voluntary intention in primary somatosensory cortext
Conducted via UMN axons of corticospinal tract
Continues along axons to anterior horn L3 spinal cord
UMN synapse with L3 LMN stimulating AP
AP continues along axons to L3 spinal nerve
Then to either L3 posterior or anterior ramus
APS via L3 anterior rami often weave through the lumbar plexus via named nerve
Then reach NMJ of supplied muscle
What happens in the spinal cord reflex of the knee jerk?
Briskly tap the patellar tendon (ligament) with a tendon hammer
The tap applies stretch to the quadriceps muscle fibres via the quadriceps tendon
The quadriceps muscle spindles (stretch receptors) initiate APs in the anterior rami axons within the femoral nerve
These sensory APs are conducted to the dorsal horn of, predominantly, spinal cord segment L4
The axons then pass into the anterior horn to synapse upon the LMNs that supply quadriceps
The APs conducted via the LMN axons in the femoral nerve reach the quadriceps neuromuscular junctions
The muscle contracts to bring about extension of the knee joint
What are descending tracts important in regarding muscle contractions?
Modulating reflex contractions
What can loss of descending controls, such as with a UMN lesion e.g. CVA, result in?
Increased stretch reflexes and spasticity
What reflexes are tested?
Biceps Brachii- C5(6) Triceps Brachii- C7 Brachioradialis- C6 Knee Jerk- L4 Ankle Jerk- S1
Where do cranial nerves exit the brain?
Anteriorly except CN IV
What are the sensory cranial nerves?
1,2,8
What are the motor cranial nerves?
3,4,6,11,12
What cranial nerves are mixed motor and sensory?
5,7,9,10
What will motor components of cranial nerves be associated with?
Motor nuclei
Where will the soma of sensory nerve cells be found?
In ganglia outside of the CNS (analogous to the DRGs for the spinal nerves)
What is the only sensory modality that does not synapse in the thalamus prior to reaching the cortex?
CN 1
Where are the nuclei for CN 3,4,6 found near?
Midline of the brainstem
Where is the nucleus of the oculomotor nerve located?
Superior colliculus of the midbrain
What type of nerve fibres are contained within CNIII?
Somatic motor + p.symp
Where is the nucleus of the trochlear nerve located?
Inferior colliculus of the midbrain
What type of nerve fibres are contained within CNIV?
Somatic motor
Where is the nucleus of the abducens nerve located?
In the pons at the floor of the 4th ventricle
What type of nerve fibres are contained within CNVI?
Somatic motor
What type of nerve fibres are contained within CNXII?
Somatic motor
Where is the nucleus of the hypoglossal nerve located?
Medulla
Where does the spinal accessory nerve arise from?
Cervical spinal cord
What are the functions of CNV5?
Somatosensation of face:discriminative touch, vibration, pain, temperature
Proprioception of chewing
Motor control- muscles of mastication, tensor tympani, mylohyoid, ant. belly of digastric, tensor veli palatini
Where is the trigeminal nerve sensory nucleus located?
From midbrain down to upper 2 segments of spinal cord- 3 parts, separated by function
What is the function of the mesencephalic nucleus of CNV?
Proprioception info from chewing muscles
What is the function of the pontine trigeminal nucleus of CNV?
Principle nucleus- discriminative touch, vibration
What is the function of the spinal nucleus of CNV?
Pain, temperature
What is unusual about the mesencephalic nucleus?
It is the only site in the CNS where the cell bodies of primary afferent neurons live inside the CNS
Where is the motor nucleus of CNV located?
Pons
What are the functions of CNVII?
Motor (muscles of mastication, stapedius)
Parasymp. innervation to pterygopalatine and submandibular ganglia
Taste (anterior 2/3 of tongue via c. tympani).
What are the functions of CNIX?
Tactile sense, pain and temperature from the posterior tongue, pharyngotympanic tube and upper pharynx.
Taste (posterior 1/3 of the tongue).
Parasympathetic fibres to the otic ganglion (parotid gland).
Motor (one muscle: stylopharyngeus)
What are the functions of CNX?
Tactile sense, pain and temperature from the pharynx, larynx, trachea, oesophagus and thoracic and abdominal viscera.
Taste (epiglottis)
Parasympathetic innervation to ganglia serving thoracic and abdominal viscera.
Motor (striated muscle of the pharynx and larynx) (cranial accessory contributes to this function).
Where is the facial nerve nucleus located?
Caudal pons (3 parts)
What are the 3 parts of the facial nerve nucleus?
Facial motor nucleus
Sup. salivatory (ps)
Solitary nucleus (taste)
Where is the glossopharyngeal nerve nucleus located?
Upper medulla (4 components)
What are the 4 components of the glossopharyngeal nerve nucleus?
Solitary nucleus (taste) Commissural (visceral) Inferior salivatory (ps) Nucleus ambiguous (stylopharyngeus muscle)
Where is the vagus nerve nucleus located?
Upper medulla (4 components)
What are the 4 components of the vagus nerve nucleus?
Solitary nucleus (taste)
Commissural (visceral)
Dorsal motor nucleus (ps)
Nucleus Ambiguus (motor)
What nucleus is shared by CN VII, IX and X?
Solitary nucleus (taste and visceral sensory information)
What nucleus is shared by CN VII, IX?
Inf. and Sup. Salivatory nuclei (parasympathetic efferents to ganglia of salivary glands and pterygopalatine ganglion)
What nucleus is shared by CN IX and X (and cranial part of XI?
Nucleus ambiguus (motor efferents to muscles of pharynx and larynx)
What shape do the solitary and commissural nucleus form?
V shape
What is the corticobulbar tract?
Part of the pyramidal tract that is motor to cranial nerves
Where does the input to CN’s containing parasymp efferents (VII, IX, X) mainly come from?
Hypothalamus whose efferents reach the preganglionic autonomic neurons both directly and via synapses in the reticular formation
What is the reticular formation?
A network of loosely aggregated cells with cell bodies, axons and dendrites intermingling in the central core of the brainstem.
What are the functions of the reticular formation?
Integrate cranial nerve reflexes
Participate in conduction and modulation of pain.
Influence voluntary movement
Regulate autonomic activity.
Integrate some basic functions, like respiration and sleep
Activate the cerebral cortex: major component of the Ascending Reticular Activating System
Where do CN VI, VII, VIII exit?
At the pontomedullary junction
What is the extracranial part of CNI?
Within olfactory mucosa in nasal cavity
What is the cranial foramina of CNI?
Cribriform plate of ethmoid bone-anterior cranial fossa
What is the intracranial part of CNI?
Olfactory nerves synapse in olfactory bulb
Then pass though the olfactory tract to cortical areas
What is the extracranial part of CNII?
Neurons of retina travel posteriorly via optic nerve from posterior hemisphere of eye through orbit
What is the cranial foramina of CNII?
Optic canal in middle cranial fossa
What is the intracranial part of CNII?
Travels around pituitary stalk to optic chiasm to form optic tract. Connects with diencephalon
How is CNI tested?
Ask patient to smell familiar smell while covering contralateral nostril
How is CNII tested?
Acuity (Snellen) Colour (Ishihara plates-colour blindness) Fields (quadrants) Reflexes (corneal, pupillary light) Fundoscopy
What is the extracranial part of CNIII?
Passed through SOF into orbit (parasymps synapse in ciliary ganglion)
What is the cranial foramina of CNIII?
SOF
What is the intracranial part of CNIII?
Connects at midbrain
Travels towards orbit in lateral wall of cavernous sinus
What is the extracranial part of CNIV?
Passed through SOF into orbit
What is the cranial foramina of CNIV?
SOF
What is the intracranial part of CNIV?
Connects with midbrain. Travels towards orbit in lateral wall of the cavernous sinus
What is the extracranial part of CNVI?
Passed through SOF into orbit
What is the cranial foramina of CNVI?
SOF
What is the intracranial part of CNVI?
Connects at pontomedullary junction. Travels towards orbit within cavernous sinus
What is the extracranial part of CNVIII?
Axons from cochlear and vestibular apparatus
What is the cranial foramina of CNVIII?
IAM in posterior cranial fossa
What is the intracranial part of CNVIII?
Travels posteromedially from the IAM to the pontomedullary junction.
What is the extracranial part of CNXI?
Axons supply sternocleidomastoid (SCM) on deep surface, then continue across the posterior triangle to supply trapezius and (SCM)
What is the cranial foramina of CNXI?
Jugular foramen In posterior cranial fossa
What is the intracranial part of CNXI?
Connects with cervical spinal cord. Ascends through foramen magnum then travels towards jugular foramen
How is CNXI tested?
Ask patients to shrug shoulders
Ask them to turn head to flex neck and turn towards opposite side
Where do the cutaneous nerves of the cervical plexus pass deep to?
Midpoint of the posterior border of SCM, but not trapezius
What is the extracranial part of CNXII?
Desends lateral to carotid sheath
At level of hyoid turns anteriorly towards lateral aspect of tongue
Supplies most muscles of tongue
What is the cranial foramina of CNXII?
Hypoglossal canal (pcf)
What is the intracranial part of CNXII?
Connects via many rootlets lateral to the pyramids of medulla oblongata. Passes anteriorly to hypoglossal canal
What does CN XII innervate?
All -glossus muscles except palatoglossus (genio/stylo/hyoglossus and intrinsic tongue muscles)
How is CNXII tested?
Ask patient to stick tongue straight out
If both CNXII’s are functioning normally the tongue tip remains in the midline on protrusion
If unilateral CNXII pathology tongue points towards side of injury
Which division of CNV is sensory and motor?
V3-mandibular
What is the extracranial part of CNV?
Sensory axons from all 3 divisions course, from superficial and deep structures, posteriorly, towards their foramen
What is the cranial foramina of CNV?
V1-SOF
V2-Foramen rotundum
V3-Foramen ovale
What is the intracranial part of CNV?
Inferior to edge of tentorium cerebelli between posterior and middle cranial fossa. Connects with pons
What does CNV1 supply?
- The upper eyelid
- The cornea (corneal reflex)
- All the conjunctiva
- Skin of the root/bridge/tip of the nose
What does CNV2 supply?
- The skin of the lower eyelid
- The skin over the maxilla
- The skin of the ala of the nose
- The skin/mucosa of the upper lip
What does CNV3 supply (superficial sensory)?
- Skin over the mandible and temporomandibular joint
apart from the angle of the mandible – supplied by C2,3 spinal nerves
What is the deep sensory territory of CNV1?
Bones & soft tissues of the orbit (except the orbital floor & lower eyelid)
Upper anterior nasal cavity
Paranasal sinuses (except the maxillary sinus)
Anterior & posterior cranial fossae
What is the deep sensory territory of CNV2?
Lower posterior nasal cavity
Maxilla & maxillary sinus
Floor of the nasal cavity/palate
Maxillary teeth & associated soft tissues (gingivae & mucosae)
What is the deep sensory territory of CNV3?
Middle cranial fossa Mandible Anterior 2/3rds of the tongue Floor of the mouth Buccal mucosa Mandibular teeth & associated soft tissues
What does CNV3 supply (motor)?
Masseter Temporalis Medial pterygoid Lateral pterygoid Tensor veli palatine Tensor tympani
How is the sensory component of CNV tested?
Ask patient to close eyes
Brush skin in each dermatome with cotton wool
Ask patient to tell you when they feel skin being touched
Compare 2 sides
How is the motor component of CNV tested?
Palpate strength of contraction of masseter and temporalis by asking patient to clench teeth
Ask patient to open their jaw against resistance
What is the extracranial part of CNVII?
Most somatic motor axons pass into the parotid gland then into 1 of the 5 branches that supply the muscles of facial expression
What is the cranial foramen of CNVII?
Temporal bone- IAM (in), stylomastoid foramen (out)
What is the intracranial part of CNVII?
Directly into IAM in the pcf. Connects anterolateral to pontomedullary junction
What does the chorda tympani do?
Taste buds of anterior 2/3 tongue
Parasymp supply to submandibular/lingual glands
What supplies stapedius?
CNVII
What are the muscles of facial expression?
Frontalis, orbicularis oculi, elevators of lips, orbicularis oris
How can the motor function of CNVII be tested?
Raise eyebrows
Close eyes tightly
Smile
Puff out cheeks and hold air
What types of nerve make up CNIX?
Special sensory (Taste), Sensory, Motor, Visceral afferent and Parasympathetic
What is the intracranial part of CNIX?
Directly towards jugular foramen in pcf. Connects with lateral aspect of superior medulla oblongata
What is the extracranial part of CNIX?
Descends towards pharynx and mouth to stylopharyngeus, parotid gland, pharyngeal mucosa, carotid body and sinus, posterior 1/3 of tongue
What is the cranial foramen of CNIX?
Jugular foramen
What does CNIX provide the general sensory supply of?
The posterior 1/3rd of the tongue
The mucosa of most of the nasopharynx and oropharynx
The mucosa of some of the laryngopharynx (some overlap with CN X territory)
The palatine tonsil
The eustachian tube
The middle ear cavity
What does CNIX provide the special sensory supply of?
Vallate papillae of posterior 1/3 tongue
What does CNIX provide the visceral afferent supply of?
Carotid sinus baroreceptors and carotid body chemoreceptors
What does CNIX provide the somatic motor supply of?
Stylopharyngeus
What does CNIX provide the parasym supply of?
Parotid gland
What nerve axons form the afferent limb of the gag reflex?
CNIX
What is the cranial foramen of CNX?
Jugular foramen
What is the intracranial part of CNX?
Directly towards jugular foramen in pcf. Connects with lateral aspect of medulla oblongata, immediately inferior to CNIX
What is the extracranial part of CNX?
Axons supply lots of structures between palate and midgut
What types of nerve are involved in CNX?
Sensory, Motor, Visceral afferent and Parasympathetic
Where does CNX travel within the neck?
Within the carotid sheath, posterior to and between the common carotid artery and IJV
Where do the recurrent laryngeal nerves curve under?
Left: arch of aorta
Right: right subclavian artery
What branches of CNX exist in the abdomen?
Both CNs X pass onto stomach surface Celiac and superior mesenteric ganglia Splenic branches Pancreatic branches Foregut branches Midgut branches Renal branches
Where do the very last ps axons of CNX pass to?
The splenic flexure of the colon
How is CNX tested?
Patient says ‘ah’ (palate muscles)
Uvula goes to functioning side if unilateral pathology
Patient swallows water (pharyngeal muscles)
Larynx movement, splutter may suggest abnormality
Listen to speech (laryngeal muscles)
Hoarseness may indicate abnormality
What are the 5 layers of the scalp?
Skin Connective tissue Aponeurosis Loose connective tissue Pericranium
Where are the named arteries of the scalp located?
Layer 2- connective tissue
What do the scalp arteries form just deep to the skin?
An anastomotic network
Where does the middle meningeal artery course over?
The deep aspect of the pterion
What are the layers of the meninges?
Dura mater- tough/fibrous. Sensory from CNV, enclodes dural venous sinuses
Arachnoid mater- arachnoid granulations (reabsorb CSF)
Subarachnoid space
Pia mater- adherent to brain and vessels entering or leaving brain
What is the diaphragm sellae?
A tough sheet of dura mater forming a roof over the pituitary fossa
What is the tentorium cerebelli?
Tough sheet of dura mater tenting over cerebellum
Attaches to ridges of petrous temporal bones
Central gap to permit the brainstem to pass through
What is the falx cerebri?
Midline structure made of dura mater
Attaches to deep aspect of skull: crista galli of ethmoid bone anteriorly
internal aspect of sagittal suture
internal occipital protruberane of occipital bone posteriorly
Separates hemispheres
What is the venous drainage of the brain?
Facial vein
Ophthalmic veins
Cavernous sinuses
Cerebral veins
Drain into superior and inferior sagittal sinuses
They drain into the sigmoid sinuses which drains into the IJV
What is the arterial supply to the brain?
Vertebral arteries
Internal and external carotids
What contains arterial branches supplying the brainstem and cerebellum?
Circle of Willis
Where is the circle of Willis located?
Inferior to midbrain, closely related to pituitary stalk and optic chiasm, within the subarachnoid space
Where is CSF reabsorbed?
Dural venous sinuses via arachnoid granulations
Where can the subarachnoid space be accessed?
Via LP at L3/4 or L4/5 IV disc levels
Where does the subarachnoid space end?
At the level of the S2 part of the sacrum
What causes hydrocephalus?
Excessive production, obstruction to flow or inadequate reabsorption leads to an increased CSF volume
What may cause an extradural haemorrhage?
Ruptured MMA- trauma to pterion
What may cause a subdural haemorrhage?
Torn cerebral veins- falls in elderly
What may cause a subarachnoid haemorrhage?
Ruptured circle of Willis (berry) aneurysm
Congenital aneurysm
In epidural anaesthesia and an LP, where does the catheter/needle pass through?
Both through: supra-, then interspinous ligaments Ligamental flavum Epidural space (fat and veins) Needle continues on to: Through dura and arachnoid mater to obtain CSF
What can result in an epidural haematoma compressing spinal cord and cauda equine?
Damage to the extradural venous plexus
Where is the needle for an LP most safely inserted?
Where the SA space surrounds the cauda equine, not spinal cord
Where the vertebrae are not fused
When should a LP not be performed?
In cases of raised ICP
Describe the fibres superior to the cochlear nuclei
Some are crossed and some are not, therefore input above this level is essentially bilateral
What are the superior olivary nucleus and nucleus of lateral lemniscus important in?
Sound localisation and as relays for stapedial and tensor tympany reflexes
What type of organisation is present in the auditory cortex?
Tonotopic- low frequency at anterolateral part, high frequency at posteromedial part
What happens if Broca’s area is damaged?
Patient’s have difficulty in producing language, often using few words and only saying the most important words in a sentence. Don’t usually have difficulty comprehending language. Known as Broca’s, motor or expressive aphasia
What happens if Wernicke’s area is damaged?
Patient’s have difficulty comprehending language. These patients can manifest defects ranging from words out of order to meaningless words.
Known as Wernicke’s, sensory or receptive aphasia
What does maintenance of equilibrium use information from?
Vision, proprioception, vestibular apparatus
What areas of the brain receive vestibular input?
Posterior insula, region of parietal lobe just posterior to the postcentral gyrus and midway between apex of brain and lateral fissure
What do the superior colliculi provide output to?
Nuclei of CNIII, IV and VI, and motor nucleus of VII, and spinal cord
Where does the lower visual field project to?
The gyrus superior to the calcarine sulcus
Where does the upper visual field project to?
The gyrus inferior to the calcarine sulcus
Where does the macula project to?
The posterior pole of the visual cortex and occupies a much greater proportion of the cortex relative to the size of the visual field it covers
What roles do the visual cortex and frontal eye fields have in eye movement?
Visual cortex- provides for movements in response to visual stimuli, such as tracking moving objects
Frontal eye fields- control movements of command, as in movements that are independent of moving visual stimuli
What does the accommodation reflex require input to?
Oculomotor and Edinger-Westphal nucleus from the visual cortex
