Arteries if the forebrian
Anterior cerebral artery—
Middle cerebral artery—- branches of the internal carotid artery
Posterior cerebral artery– (Gets blood from vertebral artery too)
Anterior Cerebral Artery
Supplies most of the medial brain
Arches over the corpus callosum
Middle Cerebral Artery
Biggest of the 3
Receives 80% of the internal carotid blood flow
Located along the lateral fissure
2 branches: upper (frontal & parietal) and lower ( temporal & occipital)
Supplies blood to 2/3 of the lateral surface
Lateral striated arteries –> lesion pyramidal tract fibers @ internal capsule.
Posterior Cerebral Artery
25% of the blood flow comes from the internal carotid artery. Other 75% comes from vertebral artery Supplies occipital (medial part) and temporal (inferior part) lobes.
Blood supply to the brain
Vertebral Artery
Posterior inferior cerebellar artery- lateral side of the medulla
Anterior spinal artery- ventral and medial aspects of the medulla
Posterior spinal artery- dorsal and medial aspects of the medulla
Blood supply to the brain
Anterior Inferior Cerebellar Artery
Supplies the lateral sides of the pons and the inner ear ( artery it the inner ear, labyrinthine artery)
Blood supply to the brain
Pontine
Small and striated
Supplies midpons
Blood supply to the brain
Posterior Cerebral
Supplies the midbrain
Venous Drainage
Superficial
Superior brain-superior sagittal sinus
Middle brain-cavernous sinus
Inferior brain-transverse sinus
Venus Drainage
Deep
Great cerebral vein of Galen
Regulation of blood flow
Auto-regulation:
- H+ concentration
- intraluminar pressure
Meninges
Dura mater
Arachnoid membrane
Pia mater
Difference in brain and vertebral canal
Cranial dura
Two layers: Periosteal layer-rich blood supply Meningeal layer-no vascular supply Potential space - located inbetween the two layers Innervated by Trigeminal nerve c1-c3
Folds of the Meningeal layer
Falx Cerebri (longitudinal fissure) Tentorium Cerebelli Falx Cerebelli (separating the cerebellum)
Cranial arachnoid
Space between dura and arachnoid = subdural space Arachnoid trabeculae suspends the brain in the CSF Arachnoid cisterns (found near sinuses, pouches)
Arachnoid granulation
CSF passes through the sinuses (helps get ride of old CSF)
Cranial pia
Follows contours of the brain (right up against the brain! big space between arachnoid and pia)
Spinal dura
One layer
Epidural fat and a plexus of veins separates intro the vertebral periosteum.
Ends at S2
Coccygeal ligament ( filum terminale externa) anchors it to periosteum of cx1 and cx2
Spinal arachnoid
Potential subdural space
Trabeculae suspends the spinal cord
Lumbar cistern L2-S2 ( pouch, elongated roots, cauda equina found within
Spinal pia
Filum terminale
21 (pairs) denticulate ligaments attach to dura from foramen magnum to below tv12
Pia is tightly attached to spinal cord as it is in the brain
Extention-filum terminale interna, has pia and dura inside the dural sac, thicker.
Dural sinuses
Lined with endothelium No valves Collects blood from brain and emissary veins Collects CSF from subarachnoid space Drains into the internal jugular vein Carry deoxygenated blood
Anterior inferior sinuses
Cavernous - sellar tursica,surround pituitary gland
Sphenoparietal - less wing of sphenoid bone
Superior petrosal
Inferior petrosal
Basilar plexus - lies along basic skull, clivous
Posterior superior sinuses
Superior sagittal
Inferior sagittal Both longitudinal fissure
Straight - runs bw tentorium falx Cerebelli
Transverse - runs in sigmoid sinus
Sigmoid
Confluence - all sinuses come together here, creating a whirlpool. Sucks the blood up by creating a vacuum.
Cerebral spinal fluid
Formed by the choroid plexus
- 14-35ml per hour
- 800 ml per day
- 150 ml at any given moment
High sodium, potassium, and chloride
Low in protein, lymphocytes, and epitheliod cells
Cushions the brain and removes waste products
Ventricles
Lateral ventricles (connected through 3rd ven. Through interventricular foramen. 4th bw pons and cerebellum connected to 3rd ven. Through cerebral aqueduct. - anterior horn-frontal lobe - posterior horn-occipital lobe - body-parietal lobe - inferior horn-temporal lobe Interventricular foramen 3rd ventricle Cerebral aqueduct 4th ventricle Central canal
Sensory unit
Stem fiber (axon) and all of its endings (receptors)
Receptive field
- territory from which a sensory unit can be excited
- not the same as a dermatome!!
Dermatome
Strip of skin Innervated by a single spinal nerve
Large amount of overlap by adjacent, small amount of overlap by non-adjacent, more neurons
Sensory transduction
The transformation of a stimulus into an electrical signal
Rapid adapting receptors phasic
(Bursting) respond quickly and maximally
Will stop responding even when stimulus continues.
Slowly adapting receptors tonic
(Continuous) continue to respond to stimulus
Don’t react as strongly as fast but stimulus is still there
Classification by source
Exteroceptor-stimuli from outside environment
Interoceptor-stimuli from internal environment
Proprioceptors- position sense (body position, tense on joints and muscles
Classification by function (modality)
Nociceptor - pain (noctious)
Thermoceptor - temperature
Mechanoceptor - “physical deformation”
Receptor types
No capsules
Free endings - pain - temperature - SA (slow adapting) Follicular ( wraps around follicule, responds to movement of hair) - touch (hair) - RA ( rapid adapting) Merkel cell (hold on to something or pressure) - edge detector - SA Specialized endothelial cells
Receptor types
Capsules
Encapsulated - meissner's RA Ruffini's (deeper, responds to outside forces against you) - shearing (drag) - SA Pacinian (largest receptor visible w/out magnification, deep, several layers of CT) - vibration - RA
Sensory inflammation of joints, muscles, and skin are…
Integrated in the parietal lobe ( major association of awareness)
The brain…
Comprises 2% of the entire body weight
Utilizes 20% of the body’s O2
17% of the cardiac output goes there.
Reticular formation
Net of fibers
Phylogenetically old
- poorly organized
- survival
Cellular regions
Raphe (seam) - midline (median) --> cells secret serotonin (5-HT) Mangocellular/Gigntocellular (big/really big) - paramedian - surrounding the Raphe - central - center of 1/2 brainstem - medial - center of 1/2 brainstem Parvocellular (small) - lateral
Neurotransmitter
Acetylcholine
motor system, excitatory
- influences movement
- peduncleopontine -> found here
Neurotransmitters
Noadrenergic/Norepinephrine
Awareness
- locus coeruleus -> found here
Nucleus of the solitary tract -> found in medulla, sensory area, viseral control
Ven trilateral medulla
Neurotransmitter
Dopamine
Motivation
Decision making
Ventral tegmental area -> found here
* precurserto norepinephrine
Neurotransmitter
Serotonin
Awareness/arousal
Mood
Decrease pain
Raphe nucleus -> found here
Goes everywhere, does everything
Afferent, efferent, autonomic, endocrine, awareness, biorhythms, motor, sensory, limbic, association
Functions
Levels of awareness - ARAS (ascending reticular activation system) > acoustic startle responses > protects from injury by a predator Modulate muscle tone Respiration and cardiac rhythm Pain suppression -> Raphe nucleus helps this Emotion of pain (limbic)
Reticulospinal tract
Medullary -> lateral! movements of limbs
- reticulospinal tract
Pontine reticulospinal tract -> medial affect trunk
Affect motor neurons
* sensory comes in dorsal horn -> blocked by Raphe nucleus