Interneurons in SC

Interneurons in the brain

www.prokop.co.uk/

Brain and Cranial Nerves

• a few brain directions• brain anatomy• cranial meninges• ventricles and flow of CSF• dural sinuses and venous flow• head injuries• Brainstem anatomy & function• cerebellar anatomy & function• cerebrum – anatomy & function

• lobes• sensory & motor cortex• limbic system• Blood flow• brain damage• cranial nerves (II, XII, V)

rostral caudal

cerebrum

cerebellumdiencephalon

Brain stem

dorsal

ventral

Anatomical directions and parts of the brain

Posterior = dorsalAnterior = ventral

Corpus callosum

Thalamus Hypothalamus

Diencephalon

Brainstem

Midbrain

Pons

Medulla oblongata

Cerebral cortex

rostral

caudal

cortex

diencephalon

S = skinC = connective tissue **A = aponeurosisL = loose connective tissueP = periosteum

Dura mater• periosteal layer• meningeal layer• sinus (venous blood)

ArachnoidSubarachnoid space (CSF)Arachnoid villusPia mater

anastomosis

Meningitis = viral, bacterial, fungal infection of blood and CSF Viral >> bacterial but bacterial is a medical emergencySymptoms: fever, headache, nausea, vomiting, light sensitivity….People living in close quarters (ie dorms) should get vaccination

Lateralventricles

Central canal

Fourthventricle

Thirdventricle

Cerebral aqueduct Lateral

ventricle

ThirdventricleCerebralaqueduct

Lateralaperture

Fourthventricle

Medianaperture

Ventricles are filled with CSF

Choroid plexus• Ependymal cells• choroid plexus (capillary bed)

Lateral ventricle

Third ventricle

Fourth ventricle

Cerebral aqueduct

1

23

4

56

7

8

Subarachnoid space

Central canal of spinal cord

Arachnoid granulation

“dirty” CSF is resorbed into the venous blood at the sinusesthrough the arachnoid villi

Dural sinuses drain into the:• jugular veins•Vertebral plexus, cavernous sinus, pterygopalatine plexus• scalp infection• occlusion of sinuses• cancer metastasis

Head injuries

Epidural hematoma• arterial bleeding• blow to head• concussion• drowsiness & coma

Subarachnoid hematoma• usually arterial• 70% due to aneurysm• rest are due to trauma• headache, stiff neck & loss of consciousness• blood in CSF

Subdural hematoma• usually venous at cerebral vein – sinus junction• creates space at dural- arachnoid junction• blow to head that jerks the brain (elderly)• trauma often forgotten

Foramen magnum

Loss of consciousnessSeizuresHeadachesDisorientationNausea and/or vomitingWeaknessSlurred speechPersonality changes

Brain stem = diencephalon, midbrain, pons, medulla oblongata

Medulla: controls respiration, heart rate and blood pressure!

Anterior view Dorsolateral view

thalamus

Pons

colliculi

Cerebral peduncle

Medullaoblongata

Brainstem anatomy and function

Thalamus: relay stationfor sensory input to the cortex

Hypothalamus: controls ANS & endocrine system

Diencephalon

T

T

Cerebellar function• coordinates joint movements• coordinates eye – motor movements• aids in planning, learning & storing motor movements• maintains muscle tone and posture• adjusts muscle performance during movement• damage to cerebellum

pons

ALPL

pons

Middle cerebellar peduncle

Damage to cerebellum

• clumsy, awkward gait• difficulty initiating movement• over or undershoot target• problems with coordination• Purkinje cells and alcohol

Fissure > sulcus

• Frontal lobe – cognition and “higher” mental processes, motor• Parietal lobe – receiving & interpreting general sensory & taste• Occipital lobe – visual information• Temporal lobe – hearing, smell, learning, memory, emotions• Insula – taste, hearing, visceral sensory info

Central sulcus

Lateral sulcus

Longitudinal fissure

Visual association area

Primary visual area

Primary somatosensory areaPostcentral gyrus

Somatosensory associationarea

Motor associationarea

Primary motor areaPrecentral gyrus

Broca area: planning speechgenerates motor program for speech Wernicke area: recognition of spoken &

written language

Cuneate fasciculusCorticospinal tract

Primary Sensory & Motor

Areas

Precentral GyrusPrimary motor

Postcentral GyrusPrimary somatosensory

Fig. 15.19(TE Art)rostral

Postcentralgyrus

Frontallobe

Centralsulcus

Primary somatosensory area

Sensory homunculus: body part inproportion to cortical area

Fig. 15.20(TE Art)rostral

Precentral gyrus

Centralsulcus

Vocalizatioin

Primary Motor Area

Motor homunculus: body part inproportion to cortical area

Basal ganglia• help in planning and executing movement• degeneration of BG with Parkinson disease

Prefrontal cortex

Abstract thought, judgement, foresight, responsibilitySense of socially responsible behavior, motivation

Limbic SystemHippocampus, amygdala, tracts, cingulate gyrus, thalamus, hypothalamus, forebrain

• Emotional brain• visceral responses to sensory input• Short term memories into long term memories

thalamus

hypothalamus

hippocampus

amygdala

forebrain

Cingulate gyrus

taste

smell

Prefrontalcortex

hearing

vision

touch

Alzheimer’s

Anterior cerebral

Middle cerebral

Posterior cerebral

vertebral

Internal carotid

Blood supply to the brain - Circle of Willis

Arteriole anastamosis

basilar

Brain damage

How? Where?• head trauma• CVA or stroke• cancer• disease• cardiac arrest• alcohol poisoning • drugs

Coma: profound state of unconsciousness (usually eyes closed, no sleep/wake cycles)alive but unable to respond to environment (some reflexive activity)can be irreversible depending, maybe still be breathing on ownhave electrical activitycan lead to PVS

Persistent Vegetative State: severe brain damage – coma – no detectable awarenessunconscious, unresponsive, unaware (can have arousal & sleep/wake cycles)exhibit some “spontaneous” behaviors (may open & close eyes, grind teeth..)usually irreversible

Brain death: complete & irreversible cessation of brain activityno electrical activity – no CN reflexesincludes cortex & brainstemdefinition has changed (anencephaly)

Terry Shiavo

Cranial nerves

Peripheral nerves that leave at the base of the brain (instead of the spinal cord)Carry sensory & motor information to head, neck and visceraThere are 12 pair of cranial nerves I-XII (each has a name and number)Can use cranial nerves to test brain function

Cranial Nerve II – Optic NerveAn example of a purely sensory cranial nerve

CN II – receives sensory information from the retina relays info to occipital lobe

Cranial Nerve XII – Hypoglossal NerveAn example of a purely motor cranial nerve

CN XII – motor information to tongue muscles responsible for swallowing, speech, chewing

Cranial Nerve V – Trigeminal NerveAn example of a mixed cranial nerve

CN V – carries sensory information from face, teeth, gums, tongue cornea, sinuses, dura mater, test using the corneal blink reflex

CN V – motor to muscles of mastication and tensor tympani

Cranial nerves