Blood Supply to the Brain Lecture Notes PDF

10/12/2024 PT 351 PT IN NEUROLOGY (1) Lecture 1 Blood Supply to the Brain Dr. Ali Bani Ahmed PT, DPT, CPT, CKTP, CES, CDNP, PhD 1 Blood Supply to the Brain 2 1 ...

10/12/2024 PT 351 PT IN NEUROLOGY (1) Lecture 1 Blood Supply to the Brain Dr. Ali Bani Ahmed PT, DPT, CPT, CKTP, CES, CDNP, PhD 1 Blood Supply to the Brain 2 1  10/12/2024 Brain Energy Metabolism Brain cells are dependent on glucose and oxygen for energy With adequate oxygen supply, neurons convert glucose into energy (ATP) aerobic glycolysis ❖Brain cells have severely limited storage capacities for either glucose or ATP → The blood must maintain a fairly constant supply of glucose →Normal cerebral blood flow (CBF) is approximately 50-to 60 ml/100g/ min →CBF of less than 10ml/100g/min results in irreversible neuronal injury Anaerobic glycolysis 3 Brain Energy Metabolism Brain cells are dependent on glucose and oxygen for energy [Blood glucose] > 2.5-3 mmol/l (50-60 mg/dl) is essential for brain function [Blood glucose] < 2.5-3 mmol/l ➔ Dizziness and loss of consciousness Exercise is contraindicated if: ❖[blood glucose] > 250 mg/dl ❖[blood glucose] < 70 mg/dl 4 2  10/12/2024 The brain makes up only 2% of total body weight but – Uses more than 10% of the oxygen metabolized by the body – Uses almost 20% of the glucose – Receives almost 20% of the cardiac output www.bme.ogi.edu/.../biophotonics/projects.html 5 Normal blood flow to the brain The central nervous system (CNS) is highly metabolically active Requires 50mL/min of blood for every 100g of tissue – On average, 750 mL volume of blood is necessary every minute! 25mL/100g puts cells in peril 8mL/100g kills neurons in minutes 6 3  10/12/2024 How Long Can Your Brain Survive Without Oxygen? ❖ Brain cells are destroyed after 4 to 6 minutes without oxygen (Astrup J et al 1981) 7 Brain Blood supply Blood is supplied to the entire brain by 2 pairs of arteries: (1) Internal carotid arteries (2) Vertebral arteries. → the right and left vertebral arteries come together at the base of the brain to form a single basilar artery. → The basilar artery joins the blood supply of the internal carotid arteries in a ring at the base of the brain ➔ circle of Willis The circle of Willis provides a safety mechanism...if one of the arteries gets blocked, the "circle" will still provide the brain with blood. 8 4  10/12/2024 Brain Blood supply 9 10 5  10/12/2024 Circle of Willis 11 Where does the brain get its blood? 1. Internal carotids 2. Vertebral arteries These arteries feed the remaining branches of the system For the most part CNS arteries come in pairs, left and right. One notable exception is the basilar artery on the ventral aspect of the pons http://www.csuchico.edu/~pmccaffrey/syllabi/SPPA342/342unit1.html 12 6  10/12/2024 13 Internal Carotids Branches from the common carotid on each side of the neck Enters the skull through the carotid canal Curves around the cavernous sinus and penetrates the dura before dividing into branches 14 7  10/12/2024 Branches of the Internal Carotids Anterior Cerebral – Major artery to medial (and some frontal and parietal) aspects of the cortex – Also supports internal capsule, and some basal ganglia Middle Cerebral – Major artery to the lateral cortex – Several branches, most importantly the lenticulostriate which supply the caudate, putamen, and anterior limb of the internal capsule Opthalmic – Supplies retina and dura Anterior Choroidal – Supplies parts of the internal capsule, thalamus, hippocampus and basal ganglia Anterior Communicating – Small conduit between anterior cerebral arteries Posterior Communicating – Supplies parts of the hypthalamus, thalamus and hippocampus 15 Branches of the Internal Carotids 16 8  10/12/2024 17 18 9  10/12/2024 19 Basilar Artery Supplies cerebellum, brain stem, and occipital lobes Several important branches – Anterior Inferior Cerebellar (AICA) – Pontine (or paramedian) Supplies pontine nuclei, some cranial nerve nuclei, corticopontine, corticobulbar and corticospinal tracts in the pontine area. – Superior Cerebellar Supplies the superior and middle cerebral peduncles, medial and lateral lemnisucus, spinal trigeminal nucles, spinothalmic tract – Posterior Cerebral Supplies most of the midbrain, thalamus, temporal lobe and medial and inferior aspects of the occipital lobe 20 10  10/12/2024 Vertebral Arteries The vertebral artery has two sets of branches: cervical and cranial – Supply the occipital lobes ➔ cranial – Provide segmental vertebral and spinal column blood supply (DEEP MUSCLES OF THE NECK) ➔ cervical Important branches – Anterior Spinal Artery Pyramids, medial lemniscus of medulla, medial longitudinal fasciculus, CN XII and inferior olive – Posterior Inferior Cerebellar Artery (PICA) Spinothalamic and spinocerebellar tracts, descending parts of CN V nuclues ambiguus (i.e. parts of CN IX and X) all in the midbrain, and vermis and inferior cerebellum Classic fodder for tests in medical school, occlusion of this artery produces Wallenberg’s syndrome (disturbed speech, articulation and swallowing) – Posterior Spinal Artery Supplies fasciculus gracilis and cuneatus, spinal trigeminal nucles, inferor cerebellar peduncle and some of the vagus nerve. 21 Vertebral Arteries 22 11  10/12/2024 Results of disrupted flow to the brain Ischemia – insufficient blood flow – Atherosclerotic plaques – Embolus travels and blocks a narrower vessel Hemorrhage – rupture of the vessel and bleeding into the cranial cavity The location of either event and the structures the disrupted vessels feed inform the clinician of what deficits a patient is likely to have. 23 We will discuss pathologies related to different brain arteries when we talk about Stroke (Cerebrovascular accident (CVA)) next week 24 12  10/12/2024 25 13