NEUROANATOMY

Hathaway FiocchiJuly, 2010

Study Tips Course objectives Power points Handbook Anatomy 1 powerpoints to review the

basics In Dr. G’s folder: “Nervous System (2

lectures)” Make sure to go over Dr. Lannings ppts

because she added some stuff!

Intro to Neurobio What is the point of all this?

Neuroanatomic diagnosis

Two questions to answer in this course: Is the nervous system involved in producing

the observed dysfunction? Where is the nervous system damaged? =

neuroanatomic diagnosis

Blood supply to the brain Circle of Willis

Vertebral aa. contribute to 1 Basilar a. Internal Carotid aa. (2)

Rete Mirabile When you don’t have major blood supply from

the internal carotid Cow, Cat, Pig

Blood supply to the spinal cord 1 ventral spinal a. 2 Dorsal spinal aa.

Meninges

Meninges 3 layers:

Dura mater Most external Thickest Well innervated Falx cerebri

Arachnoid: Middle layer Arachnoid trabeculae Arachnoid granulations: CSF drainage

Pia mater: Innermost, closely adhered to the nervous tissue Highly vascular Assoc. with denticulate ligament of the spinal cord

Spaces Epidural space

Mainly potential space in brain Fat and vessel filled space in spinal cord

Used for injections Subdural space

Potential space in both brain and spinal cord Subarachnoid space

Interdigitated with arachnoid trabeculae Contains CSF Sites in the brain for tapping and sites on spinal

cord

Meninges Cranial vs. Caudal Pia mater is same in the brain and spinal cord Arachnoid

Specialized enlarged areas around the brain = cisterns Cerebellomedullary cistern is preferred site for CSF

collection in small animals and in large animals under anesthesia

Dura Mater Outer and inner layer of the dura are closely adhered

NO epidural space around the brain = potential space Big epidural space in the spinal cord = injections Dural reflections compartmentalize the brain and

reduce movement falx cerebri: midline of the cerebrum

3 Layers

3 Spaces

Cranial Meninges and Spaces

Spinal MeningesPia MaterArachnoidDura MaterWhere does an Epidural go?

Caudal Meninges Filum terminale: Terminus of the spinal

cord Caudal ligament: Attachment of filum

terminale to last vertebral foramen Lumbospinal cistern: for CSF tap in

caudal meninges-in the subarachnoid space around the filum terminale

Epidural space is full of fat and vessels and can be used for injections--carefully!Can you label the:

Dura, Arachnoid, Pia, Filum terminale, Caudal ligament and Lumbospinal Cistern?

Meninges and Spaces con’t.

What space is used for collection of CSF?- Subarachniod space

What space is used for injections?

- Epidural spaceIn both cranial and caudal meninges?

No, caudal only—why?

CSF production, drainage

CSF: is an ultrafiltrate of blood Produced by: ependymal cells of the choroid

plexuses within the ventricles Drained by: arachnoid granulations—one way

valve system moves CSF into dural sinuses Dural sinuses are valve-less system

Functions Water-jacket Lymphatics Transport hypothalamic hormones within brain CO2 concentration monitoring

Ventricles Vestiges of the neural tube within the

brain tissue and spinal cord Lined with special glial cells called

ependymal cells of the choroid plexuses which help produce and circulate the CSF within the ventricles

Ventricles all connected and CSF flows from cranial to caudal until the 4th ventricle

Flow of CSF through the ventricles: Lateral 3rd 4th arachnoid space (meninges) or central canal

Ventricles

Try to superimpose these 2 views in your head to understand the relationship of the ventricles in the brain

Regeneration of nervous tissue Damage to the cell body = death

Except: olfactory neurons which regenerate! Damage to axons of the CNS = minimal

regeneration at best Damage to axons of the PNS = more success

To muscles and viscera! 3 types of injury to an axon

Stretch related Lacerations Compression (mechanical or vascular)

Extent of regeneration depends on the number and severity of axons damaged

Which of the following injuries has the best chance of regeneration? Damage to axon in CNS Damage to cell body in CNS Damage to axon in PNS

Anatomy of the Brain = wet lab

Occipital Lobe

Temporal Lobe

Parietal Lobe

Frontal Lobe

Pyriform Lobe

Olfactory bulb

Cerebellum

Brain Stem

Optic Nerve

Cerebrum Highest function of the CNS

Seat of consciousness and cognitive functions Receives all sensory information that reaches conscious perception—not reflexes! Divided into 2 hemispheres: left and right Each hemisphere has 5 lobes

Occipital Lobe

Temporal Lobe

Parietal Lobe

Frontal Lobe

Pyriform Lobe

5 Lobes of the Cerebral Cortex

Occipital lobe:- Perception of visual stimuli- Damage causes cortical blindness - Reflex arcs are still intact

Temporal lobe: - Processing of hearing- Input from each ear goes to BOTH left and right temporal lobe- MOST is contralateral- Damage to one lobe does NOT result in deafness even in just one ear

Parietal lobe:- Perception of sensory information to create a 3D map of the world/body in space- Damage causes hemineglect

Frontal Lobe - Contains the sensory and motor cortices - Initiation of movement - Damage manifests in a delay of initiating movement or inappropriate initiation- Lesion is contralateral to the side of manifestation

Pyriform Lobe:- Perception of olfaction - Associated with the Limbic system- Complete damage is Anosmia

Cerebrum: Major functions Sensory input

Olfaction to pyriform (olfactory bulbs are technically considered part of the pyriform lobe)

Auditory to temporal lobe Vision to occipital lobe Frontoparietal region for contralateral somatosensory input Somatic sensation = the senses of touch, pressure, pain,

temperature Association cortex: cognition and decision

making Motor output from the motor cortex in the

frontal lobe

Damage to Cerebrum Clinical signs of Cerebrum dysfunction

Disturbances of consciousness Paresis of voluntary movement

What is paresis? Disturbances of sensory function,

perception and seizures

Limbic System Limbic “Lobe” is a collection of cortical and

subcortical structures functionally linked by their role in emotion and survival drives. What is a collection of cell bodies in the CNS called? What is a collection of cell bodies in the PNS called?

Nuclei involved in the limbic system Hippocampus Cingulate gyrus Hypothalamus Amygdala Parts of thalamus

Limbic structures All components of the limbic system assign

emotional and autonomic responses to sensory experiences

Hypothalamus – regulates autonomic functions and basic survival behaviors Hunger, Satiety, Thirst, Temp, Osmoregulation, Circadian

rhythms Amygdala – emotional memory formation; short

term Assigning a fear response to a noxious stimuli

Hippocampus – converts short term memory to long term memory

Sample quiz question:match structure with function

Limbic structure FunctionA. Hippocampus 1. Memory formationB. Hypothalamus 2. Circacian Rhythm regulationC. Amygdala 3. Osmoregulation

4. Satiety Center

*****ARAS**** Maintains consciousness!

Receives collaterals from all sensory input and dictates the level of arousal in the cerebral cortex

Shapes selective attentions Pressure on hindbrain causes most common loss

of consciousness Early compression miosis Increased compression mydriasis

Canine Narcolepsy could be from a receptor mutation here that decreases excitatory inputs from ARAS which would normally maintain consciousness

What else comes from the hindbrain????

ARAS VOCAB BAR: Bright Alert Responsive Input from the cerebrum keeps you

“awake” ALERT: normal response to environmental stimuli OBTUNDED: Withdrawn and unwilling to perform

normally DEMENTED: Animal is responsive, but the responses

are abnormal STUPOROUS: Patient unresponsive except to noxious

stimuli COMATOSE: Patient unresponsive to both

environmental and noxious stimuli

Oink! Are you obtunded?

Seizure

A seizures is a cortical event characterized by abnormal neuronal discharge that is both excessive and hypersynchronized

Can be caused by both excessive excitation or decreased inhibition

Stages of Seizures Prodrome (see Lanning’s ppt): early indicator of

disorder Aura: period of altered behavior Ictus: synchronized, hyperactive firing of neurons is

occurring Associated with a loss of consciousness Alterations of sensation: hallucinations Disturbances of autonomic function: salivation,

tachycardia Alterations of muscle tone associated with

involuntary movements Post-ictus: period of confusion and restlessness Inter ictus (see Lanning’s ppt) periords between

seizures

Seizure vocab Primary Focus: restricted area of the cortex

when the seizure begins

Kindling: spreading or reinforcement of the tendency to seize

Mirror focus is when seizure spreads to the contralateral side across the corpus callosum by commissural fibers

Seizure vocab Focal seizure or partial seizure: the seizure is

confined to one part of the cerebrum, there are no convulsions Focal motor seizure = chewing-gum fit

Focal seizure with secondary generalization: neurons outside the focus are recruited Usually within the limbic system Produces behavioral or emotional seizures

Simple-partial seizure = term for seizure that does not affect consciousness

Seizure vocab Generalized seizure: spreads rapidly to both

hemispheres, can have convulsions with loss of consciousness Petit mal = no convulsions Seizures with convulsions and loss of

consciousness: Grand mal AKA tonic-clonic AKA major motor Ictus is collapse, extensor rigidity, opisthotonus, apnea all

characteristics of the tonic phase Clonic phase: period of alternation between flexion and

extension of the limbs with violent chewing or vocalization “Paddling” Increased autonomic = salivation, urination, defecation

can also occur

Cranial Nerve ReviewWhich cranial nerves have Parasympathetic innervation?

What cranial nerves are tested with the gag reflex?

What cranial nerve can regenerate its cell bodies?

III, VII, IX, X

IX and X

I