This document discusses cerebral blood flow and brain metabolism. It begins with an outline of the topics to be covered, which include cerebral blood flow, vascular anatomy, the blood brain barrier, cerebrospinal fluid, factors regulating blood flow, problems with blood flow and metabolism, and brain metabolism problems. It then goes on to describe the vascular anatomy that supplies blood to the brain, including the internal and external carotid arteries and vertebral arteries. It also discusses the circle of Willis, microcirculation in the brain, the blood brain barrier, cerebrospinal fluid, and factors involved in regulating cerebral blood flow such as blood pressure, vascular resistance, autoregulation, and metabolic mediators.
Physiology of Neuromodulation and neuromodulators. Difference between neuromodulation and synapse. Recent advances in neuromodulation, clinical application of neuromodulation.
A brief overview of the physiology of the neuromuscular junction.It includes a video towards the end sourced from the internet with the copyright watermarks intact.
Physiology of Neuromodulation and neuromodulators. Difference between neuromodulation and synapse. Recent advances in neuromodulation, clinical application of neuromodulation.
A brief overview of the physiology of the neuromuscular junction.It includes a video towards the end sourced from the internet with the copyright watermarks intact.
Review of Nervous System, Unconsciousness, and CVA. The Nursing Core FunctionsAyinla Kazeem
This presentation was made at several sessions of Mandatory Continuing Professional Development Programme for Nigerian Nurses in Kwara State, and have undergone series of editing till date. While still working on the final editing to totally conform with global standard of practice, I deemed it necessary to share it in this forum.
Sex linked describes the sex-specific patterns of inheritance and presentation when a gene mutation is present on a sex chromosome rather than a non-sex chromosome. In humans, these are termed X-linked recessive, X-linked dominant and Y-linked.
Connexins (Cx) (TC# 1.A.24), or gap junction proteins, are structurally related transmembrane proteins that assemble to form vertebrate gap junctions. An entirely different family of proteins, the innexins, form gap junctions in invertebrates.[1] Each gap junction is composed of two hemichannels, or connexons, which consist of homo- or heterohexameric arrays of connexins, and the connexon in one plasma membrane docks end-to-end with a connexon in the membrane of a closely opposed cell. The hemichannel is made of six connexin subunits, each of which consist of four transmembrane segments. Gap junctions are essential for many physiological processes, such as the coordinated depolarization of cardiac muscle, proper embryonic development, and the conducted response in microvasculature. For this reason, mutations in connexin-encoding genes can lead to functional and developmental abnormalities.
Eicosanoids are signaling molecules made by the enzymatic or non-enzymatic oxidation of arachidonic acid or other polyunsaturated fatty acids (PUFAs) that are, similar to arachidonic acid, 20 carbon units in length. Eicosanoids are a sub-category of oxylipins, i.e. oxidized fatty acids of diverse carbon units in length, and are distinguished from other oxylipins by their overwhelming importance as cell signaling molecules. Eicosanoids function in diverse physiological systems and pathological processes such as: mounting or inhibiting inflammation, allergy, fever and other immune responses; regulating the abortion of pregnancy and normal childbirth; contributing to the perception of pain; regulating cell growth; controlling blood pressure; and modulating the regional flow of blood to tissues. In performing these roles, eicosanoids most often act as autocrine signaling agents to impact their cells of origin or as paracrine signaling agents to impact cells in the proximity of their cells of origin. Eicosanoids may also act as endocrine agents to control the function of distant cells.
Ecosystem is system formed by the interaction of a community of organisms with their physical environment.
Ecosystem can be natural or artificial.
Ecosystem has both abiotic and biotic components.
Ecosystem has primary, secondary and tertiary function.
Human social systems and ecosystems are complex adaptive systems
Ergonomics is the study of people in their working environment.
Cushing's syndrome is the pool of signs and symptoms due to extended exposure to glucocorticoids such as cortisol.
Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a round red face, a fat lump between the shoulders, weak muscles, weak bones, acne, and fragile skin that heals poorly.
Women may have more hair and irregular menstruation. Occasionally there may be changes in mood, headaches, and a chronic feeling of tiredness.
Usual onset: 20 – 50 years
According to UNESCO Constructivism is learning theory which places the learner at the center of the educational process on the understanding that the learner actively constructs knowledge rather than passively receiving it.
According to Brader - Araje and Jones (2002), Constructivism can be defined as “the idea that development of understanding requires the learner to actively engage in meaning-making”.
Electroencephalography (EEG): an electrophysiological monitoring method to re...Habtemariam Mulugeta
Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical activity of the brain.
It is typically noninvasive, with the electrodes placed along the scalp, although invasive electrodes are sometimes used, as in electrocorticography.
EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain.
As Hall says; “To look at and listen to self is often too difficult without the help of a significant figure (nurturer) who has learned how to hold up a mirror and sounding board to invite the behaver to look and listen to himself. If he accepts the invitation, he will explore the concerns in his acts and as he listens to his exploration through the reflection of the nurse, he may uncover in sequence his difficulties, the problem area, his problem, and eventually the threat which is dictating his out-of-control behavior.”
The musculoskeletal system consists of the muscles, tendons, bones and cartilage together with the joints
The primary function of which is to produce skeletal movements
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
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Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
How to Give Better Lectures: Some Tips for Doctors
Cerebral Blood Flow & Brain Metabolism.pptx
1. “Cerebral Blood Flow & Brain Metabolism”
College of Health Sciences
School of Medicine
Department of Medical Physiology
P.by: Habtemariam Mulugeta
ID No. GSR/2895/14
1
4. 4
Objectives
After completing this session, students should be able to:
Describe briefly about Cerebral Blood Flow.
Explain about Regulation of Cerebral Blood Flow.
Differentiate the Factors affecting Cerebral Blood Flow.
Appreciate the Problems of Cerebral Blood Flow.
Familiarize with the Brain Metabolism.
Habtemariam M.
4
5. 5
Introduction
5
Skull is a closed structure.
Most of it's content is brain tissue while some of it is
blood and CSF.
Brain occupies 2% of the total body weight.
Cerebral Vasculature has unique Anatomy &
Physiology.
Brain is highly vulnerable to disruption in blood flow.
Habtemariam M.
Monro-Kellie doctrine
Figure 1 – The intracranial components and
their respective volumes
6. 6
Cont.
Blood Supply
750 ml/min
55 ml/100 gm/min
14% of total Cardiac output
Habtemariam M.
6
Oxygen Supply
46 ml/min
3.3 ml/100 gm/min
18.4% of total O2 consumption
CBF: is the blood movement to the brain.
Supplies Oxygen, glucose and nutrients.
Remove CO2, Lactic acid & metabolites.
7. 7
CBF & Vascular Anatomy
The left and right common carotid arteries supply most of the blood to the
head and neck.
They travel parallel immediately lateral to either side of the trachea.
At the superior border of the thyroid cartilage, each artery divides into:
External Carotid Artery that supplies structures external to the skull
Internal Carotid Artery that supplies internal skull structures.
Habtemariam M.
7
9. 9
Internal Carotid Artery (ICA)
arise from common carotid arteries (neck)
branches only after it enters the skull through the carotid canal
Once inside the skull, it forms multiple branches, including:
Anterior and Middle cerebral arteries, which supply the brain
Ophthalmic arteries, which supply the eyes.
Habtemariam M.
9
10. 10
Cont.
Internal carotid arteries and their branches: are considered as anterior
circulation of brain.
Anterior cerebral arteries: are connected by anterior communicating artery.
ICA near its termination: is connected to posterior cerebral artery (PCA) by
Posterior communicating artery.
Habtemariam M.
10
11. 11
Vertebral Arteries:
Emerge from the first part of subclavian artery.
1. Pre-vertebral parts: begin in the root of the neck
2. Cervical parts: in transverse foramina of C1-C6 vertebrae.
3. Atlantic parts: perforate dura, arachnoid & enter through foramen
magnum.
4. Intracranial parts: at pons form basilar artery.
Habtemariam M.
11
12. 12
Cont.
Basilar artery: at the clivus in pontocerebellar cistern ventral to pons & ends
by branching in to two posterior cerebral arteries.
Vertebrobasilar arterial system & branches: are considered as posterior
circulation of the brain.
Habtemariam M.
12
14. 14
Anterior Cerebral Artery: most of medial, superior surface & frontal pole.
Middle Cerebral Artery : most of lateral surface & temporal pole.
Posterior Cerebral Artery: most of inferior surface & occipital Pole.
Habtemariam M.
14
Cerebral Arteries:
16. 16
Cerebral Arterial Circle
Circle of Willis.
is important anastomosis of arteries around
the sella turcica.
roughly pentagon-shaped & on ventral
surface of brain.
Its various components give numerous small
branches to supply the brain.
Habtemariam M.
16
Figure 5 – Inferior View of Circle of
Willis
17. 17
It is formed by:
posterior cerebral arteries
posterior communicating arteries
Internal carotid arteries
anterior cerebral arteries
anterior communicating arteries
Function:
equalizes blood pressure in the brain
can provide collateral channels should
one vessel become blocked
Normally no crossing over of blood from
one side to the other
17
Habtemariam M.
Cont.
19. 19
Collateral Circulation
In a normal individuals there is no net flow of blood across these
communicating arteries.
But to maintain patency and prevent thrombosis there is to-and-fro
flow of blood.
Their importance appears when a pressure gradient develops.
Habtemariam M.
19
20. 20
Cont.
Second collateral flow appears in surface connections that bridge pial
arteries
They bridge major arterial territories:
ACA – PCA, ACA- MCA, MCA – PCA
They are called leptomeningial pathways or equal pressure pathways.
Habtemariam M.
20
21. 21
Cerebral Microcirculation
Capillary density in grey matter is 4 times higher than white matter.
Pre-capillary vessels divide and reunite to form anastomotic circle called as Circle of
Duret.
They are highly tortuous and irregular.
Velocity of RBC’s is higher in these capillaries.
To facilitate transfer of substrate and nutrients RBC’s have to traverse longer distance
via these capillaries
Habtemariam M.
21
22. 22
Cont.
The brain capillaries are much less “leaky” than are capillaries in other
portions of the body.
Capillaries in the brain are surrounded by “glial feet,” which provide
physical support to prevent overstretching of the capillaries in the event
of exposure to high pressure.
Habtemariam M.
22
23. 23
Cont.
Cerebral capillaries:
are non-fenestrated & with tight junctions
between endothelial cells, except the capillaries
in choroid plexus which are fenestrated.
Few vesicles in endothelial cells
Limited diffusion & vesicular transport
Surrounded by end feet of astrocytes; induce
tight junctions in endothelial cells
Anatomic basis for BBB.
Habtemariam M.
23
Figure 7 - Cerebral capillary
24. 24
Blood Brain Barrier (BBB)
Continuous non-fenestrated capillaries make up BBB.
Tight junctions between capillary endothelial cells.
Paucity of the vesicles in the endothelial cytoplasm.
Presence of numerous carrier-mediated & active transport mechanisms in cerebral
capillaries.
The blood-CSF barrier is due to tight junctions in choroid plexus endothelial cells.
The capillaries in choroid plexus are fenestrated with no tight junctions.
Habtemariam M.
24
25. 25
Cont.
Properties of BBB
Only few substances can freely diffuse through BBB.
CO2, O2, water & free forms of steroid hormones.
H+ & HCO- only slowly penetrate the BBB.
Proteins, polypeptides & protein bound forms of hormones do not cross BBB.
Glucose is transported by GLUT1 transporter.
Active transporters are also present
various ions (Na+ - K+ -2Cl- co transporter )
thyroid hormones, organic acids, choline, nucleic acid precursors, amino acids etc.
Habtemariam M.
25
26. 26
Significance of BBB
It maintains the homeostasis in CNS.
Protects the brain from endogenous & exogenous toxins.
Prevents the escape of neurotransmitters into general circulation.
Habtemariam M.
26
27. 27
Circumventricular Organs
The parts of the brain which have fenestrated capillaries and thus no BBB.
The circumventricular organs provide a window for the interaction of brain with blood.
Posterior pituitary with Median Eminence
Area Postrema
Organum Vasculosum of Lamina Terminalis (OVLT)
Subfornical Organ (SFO)
Anterior pituitary & Pineal Gland
Habtemariam M.
27
28. 28
Cerebrospinal Fluid (CSF)
clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of
all vertebrates.
Produced by specialized ependymal cells in the choroid plexus of the ventricles of the brain
Absorbed in the arachnoid granulations.
There is about 125 mL of CSF at any one time, and about 500 mL is generated every day.
occupies the subarachnoid space and the ventricular system around and inside the brain and
spinal cord.
Habtemariam M.
28
29. 29
Cont.
There is also a connection from the subarachnoid space
to the bony labyrinth of the inner ear via
the perilymphatic duct where the perilymph is
continuous with the CSF.
The ependymal cells of the choroid plexus have
multiple motile cilia on their apical surfaces that beat to
move the CSF through the ventricles.
Habtemariam M.
29
Figure 8 - MRI showing pulsation of CSF
30. 30
Cont.
A sample of CSF can be taken from
around the spinal cord via lumbar
puncture.
CSF circulates within the ventricular
system of the brain.
Habtemariam M.
30
Figure 9 - Distribution of CSF
31. 31
Cont.
CSF is derived from blood plasma and is largely similar to it except
that CSF is nearly protein-free compared with plasma and has some
different electrolyte levels.
Due to the way it is produced, CSF has a higher chloride level than
plasma, and an equivalent sodium level.
Habtemariam M.
31
32. 32
Significance of CSF
1. Buoyancy: The actual mass of the human brain is about 1400–1500 grams; however, the net
weight of the brain suspended in CSF is equivalent to a mass of 25-50 grams.
2. Protection: CSF protects the brain tissue from injury when jolted or hit, by providing a fluid
buffer that acts as a shock absorber from some forms of mechanical injury.
3. Prevention of brain ischemia: The prevention of brain ischemia is aided by decreasing the
amount of CSF in the limited space inside the skull. This decreases total intracranial pressure
and facilitates blood perfusion.
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33. 33
Cont.
4. Homeostasis: allows for regulation of the distribution of substances between
cells of the brain, and neuroendocrine factors, to which slight changes can cause
problems or damage to the nervous system.
5. Clearing waste: allows for the removal of waste products from the brain, and is
critical in the brain's lymphatic system, called the glymphatic system.
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34. 34
Venous Drainage of the Brain
thin-walled & valveless.
Pierce arachnoid & meningeal
layer of dura (subdural space)
end in the nearest dural venous
sinuses ultimately IJVs.
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Figure 10 – MRI Venography of Brain
35. 35
Cont.
Superior Cerebral Veins:
are on superolateral surface of the brain
drain into the superior sagittal sinus.
Inferior & Superficial Middle Cerebral Veins:
from inferior, postero-inferior & deep aspects of cerebrum
drain into cavernous, straight, transverse & superior petrosal sinus.
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36. 36
Cont.
The Great Cerebral Vein:
is a single, midline vein formed inside the brain by the union of two
internal cerebral veins;
merges with inferior sagittal sinus to form straight sinus.
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37. 37
Cont.
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Figure 11 - Venous Drainage of the Brain
Internal Jugular Veins
Cerebral Venous sinuses
Cerebral Veins
Venous Drainage:
38. 38
Cerebral Blood Supply
Brain accounts for 2% of body weight yet requires 20% of resting oxygen
consumption.
O2 requirement of brain is 3 – 3.5 ml/100gm/min & in children it goes
higher up to 5 ml/100gm/min.
That’s why brain requires higher blood supply 55ml/100gm/min is the rate
of blood supply.
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39. 39
Cont.
Brain is having the highest energy requirement by mass.
Even though brain constitutes less than 2% of body weight, the adult brain receives
15% of resting cardiac output and uses 20% of the total energy produced by the body.
In children, up to 50% of the energy consumption of the body is being accounted for
by the brain.
Much of this energy allocation is devoted to activities connected to neural signaling
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42. 42
Cerebral Perfusion Pressure
It is the net pressure gradient causing blood flow to the brain.
CPP = MAP – CVP
CVP = ICP
CPP = MAP – ICP
CPP is directly related to CBF: {Increase CPP causes increase CBF}
Any factor affecting MAP or ICP will affect the CBF.
CBF is maintained normal over a wide range of MAP by ‘Autoregulation.’
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43. 43
Role of ICP in maintaining CBF
The volume of blood, spinal fluid, and brain in the cranium at any time must
be relatively constant (Monro–Kellie doctrine).
Increase ICP Decrease CBF
Decrease ICP Increase CBF
Cushing’s reflex
ICP Decrease CBF VMC ischemia Increase sympathetic discharge
Increase BP Increase CBF
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45. 45
Cont.
Contrary to the key assumptions behind the Hagen-Poiseuille law, it is not strictly
followed:
normal blood flow is not continuous but pulsatile,
blood vessels are not rigid and branchless tubes,
if the rate of flow is continuously increased, there comes a point when resistance to
flow increases sharply and the flow ceases to be laminar, instead forming a turbulent
pattern,
cerebrovascular autoregulation
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46. 46
Cerebral Vascular Resistance (CVR)
CVR = (8.η.L)/(π.r4)
Resistance of the cerebral circulation is subject to dynamic changes in the
contractile state of vascular smooth muscle (VSM).
Most resistance at the level of the penetrating precapillary arterioles.
However, up to 50% of total CVR arises from smaller pial arteries (150 to 200
μm in diameter) and arteries of the circle of Willis.
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47. 47
Autoregulation
Maintains constant blood flow to the brain despite wide fluctuations in CPP.
It is the inherent property of resistance vessels.
Increase BP vasoconstriction
Decrease BP vasodilation
Maintains blood flow in the range of 50 – 150 mm Hg CPP.
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48. 48
Cont.
Proposed mechanisms include:
Myogenic Mechanism: Intrinsic changes in vascular smooth muscles (VSM) tone.
Endothelial Mechanism: the release of a variety of vasoactive substances from the
endothelium.
Neurogenic Mechanism: periadventitial nerves in response to changes in transmural
pressure.
Metabolic Mechanism: metabolic activity of astrocytes and neurons for regulating CBF.
Pure changes in perfusion pressure involve myogenic response in VSM (Bayliss effect).
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50. 50
Cont.
Venous physiology:
Venous system contains most of the cerebral blood volume.
Slight change in vessel diameter has profound effect on intracranial blood
volume.
Less smooth muscle content
Less innervation than arterial system
But evidence of their role is less.
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51. 51
Cont.
Pulsatile perfusion: myogenic response bring a change in perfusion pressure.
Cardiac output (CO): may be responsible for improved CBF.
Rheological factors:
Related with blood viscosity.
Hematocrit has main influence on blood viscosity.
Flow is inversely related with hematocrit.
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52. 52
Metabolic & Chemical Regulation
Cerebral metabolic demand is the main regulator of cerebral blood flow,
It occurs automatically, probably in response to the abundance or deficit of various local
factors - mainly metabolic byproducts and metabolic substrates:
Carbon dioxide concentration in the brain parenchyma
Low oxygen
pH of the blood
When cerebral metabolic demand is high – CBF will be higher at any given Perfusion
Pressure because CVR will decrease.
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53. 53
Cont.
CO2: (Hypercapnia) - promotes increased CBF at any given perfusion pressure.
PaCO2 exerts profound effects on CBF, range of 30 to 50 mm Hg.
At normal conditions CBF has linear relationship with CO2.
For every 1 mm Hg change of PaCO2 CBF changes by 2–4%.
When alterations in PaCO2 have been sustained for 3 to 5 hours, there is an adaptive
return of CBF toward baseline levels.
Hypercapnia combined with hypoxia has a magnified effect on CBF.
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54. 54
Cont.
1. Change of periarteriolar pH leads to a change in NO synthase activity;
2. NO synthase catalyzes intracellular cGMP production;
3. cGMP acts as a second messenger to affect a change in intracellular ionized Ca+2 availability
4. The upshot of all this is a decreased CVR
5. If the resistance is decreased but the pressure difference remains the same, the flow
increases.
6. The increase in flow is by about 1-2ml/100g/min for every 1mmHg increase in CO2.
Conversely, blood flow decreases as CO2 decreases.
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56. 56
Cont.
Hydrogen ions: induce cerebral vasodilation in proportion to their concentration in the
cerebral blood.
Any substance that increases the acidity of the brain, and therefore the H+ concentration,
increases CBF; such substances include lactic acid, pyruvic acid, and other acidic compounds
that are formed during the course of metabolism.
CO2 combines with water to form carbonic acid, which partially dissociates to form H+
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57. 57
Cont.
Oxygen:
Elevated inspired O2 concentrations elicit CVR and decrease CBF.
Within physiological range PaO2 has no effect on CBF.
Hypoxia is a potent stimulus for arteriolar dilatation.
At PaO2 50 mmHg, CBF starts to increase and at PaO2 30 mm Hg, it doubles.
Hypoxia elicits VSM relaxation by inhibiting sarcoplasmic Ca2+ uptake and stimulating
the production of EDRF.
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59. 59
Neural control
The cerebral circulation has dense sympathetic innervation.
Under certain conditions, SNS stimulation can cause marked constriction of the
large and intermediate-sized cerebral arteries.
Under many conditions in which the SNS is moderately activated.
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60. 60
CBF Problems
Stroke: a blood clot blocks the flow of blood in your cranial artery.
Cerebral hypoxia: part of the brain doesn’t get enough oxygen.
cerebral hemorrhage: internal bleeding in the cranial cavity.
Cerebral edema: swelling that occurs due to an increase of water in your
cranial cavity.
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61. 61
Brain Metabolism
Resting conditions -brain metabolism:
accounts for 15% of the total metabolism of the body.
about 7.5 times the average metabolism of the remainder of the body.
Most neuronal activity depends on the second-by-second delivery of glucose and oxygen from
the blood.
Glucose delivery to the neurons its transport through cell-membrane of the neurons does not
depend on insulin.
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62. 62
Cont.
Glucose is the obligatory energy substrate for brain and it is almost entirely oxidized to CO2 and H2O.
• Normal values for cerebral metabolic supply and demand:
• Cerebral blood flow: 50ml per 100g of tissue, per minute.
• Cerebral DO2: 150-300ml/min (Hb of 150)
• CMRO2: Cerebral Metabolic Rate of Oxygen: 3.8ml/100g/min
• Cerebral oxygen extraction ratio (CO2ER): 35-25%
• Jugular bulb venous saturation (SjvO2): 55-75%
• Cerebral glucose consumption: 6.3mg glucose per 100g per minute
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63. 63
Cont.
CMRO2 = CBF × 1.39 × Hb × [ (SaO2 - SjvO2) + (0.03 × [PaO2 - PvO2]/100) ]
Metabolic substrate:
The brain normally consumes glucose and oxygen, and its RQ is 1.0
Alternative substrates include ketones, lactate, mannose, and others
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64. 64
Cont.
Ketone bodies are metabolites that replace glucose as the main fuel of the
brain in situations of glucose scarcity, including prolonged fasting,
extenuating exercise, or pathological conditions such as diabetes.
Lactate is formed predominantly in astrocytes from glucose or glycogen in
response to neuronal activity signals.
Lactate and pyruvate can sustain synaptic activity in vitro.
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65. 65
Cont.
Mannose can sustain normal brain function in the absence of glucose.
It crosses the BBB and in two enzymatic steps is converted to fructose-6-
phosphate, a physiological intermediate of the glycolytic pathway.
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66. 66
Cont.
Glucose, which is taken up by facilitated diffusion via GLUTs, can
either be stored as glycogen (in the brain, the major glycogen stores
are found in the astrocytes) or metabolized in the glycolytic pathway.
The final product of glycolysis is pyruvate, which is either transferred
into mitochondria, where it is metabolized in the citric acid cycle, or
converted to lactate.
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67. 67
Cont.
Conversion of pyruvate to lactate is catalyzed by the oxidoreductase
lactate dehydrogenase (LDH), which reduces pyruvate to lactate and
oxidizes NADH + H+ to NAD+
The reaction is reversible, allowing cells to either produce or consume
lactate, depending on their metabolic profile.
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68. 68
Glycolytic Pathway of Brain Metabolism
1. The Astrocyte to Neuron Lactate Shuttle.
2. Astrocytes take up glucose from the blood capillaries via glucose transporters (GLUTs).
3. In astrocytes, glucose is either stored as glycogen or metabolized to pyruvate in the
glycolysis.
4. Pyruvate is then converted to lactate by the oxidoreductase lactate dehydrogenase (LDH)
isoform 5 (LDH5).
5. The lactate is transferred from astrocytes to neurons by MCT1, MCT2, and MCT4 in
cotransport with a proton.
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69. 69
Cont.
6. MCT transport activity was found to be facilitated by interaction with the CAII and CAIV,
which catalyze the equilibrium of H+, HCO3– and CO2 both intra- and extracellularly, and
by the activity of the electrogenic sodium-bicarbonate cotransporter NBCe1.
7. In neurons, lactate is converted back to pyruvate by LDH1 and transferred into mitochondria
for aerobic energy production in the TCA.
8. In addition, glucose is directly taken up into neurons where it can either serve as energy
source in the glycolysis or is shuttled into PPP for production of NADPH and cellular
building blocks like ribose-6-phosphate.
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71. 71
Factors affecting cerebral metabolic rate
Table 1 - Factors which Influence the Cerebral Metabolic Rate
Increase Decrease
Vascular abnormalities Acute stages of haemorrhagic stroke Ischaemic stroke, Chronic cerebrovascular
disease
Infectious processes Fever, systemic infection Encephalitis or meningitis, Neurosyphilis
Neoplasia Glioma Paraneoplastic cerebellar degeneration
Drugs Ketamine, Amphetamine General anaesthetics
Neurological disorders Seizure Post-ictal state, Eclampsia
Physiological phenomena Stress, Anxiety, Hyperventilation Normal sleep
Trauma Traumatic brain injury
Endocrine and metabolic disorders Hepatic encephalopathy, Hypoglycaemia,
Uraemia, Myxoedema Habtemariam M.
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72. 72
Brain Metabolism Abnormalities
The brain metabolic diseases are classified:
Intoxication Disorders
Energy Production Disorders
Disorders of the Biosynthesis & Breakdown of Complex Molecules
Neurotransmitter Defects
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74. 74
Summary
Habtemariam M.
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CBF is the blood flow to the brain.
Supplies oxygen, glucose and nutrients.
Removes CO2, lactic acid & metabolites.
Cerebral vasculature has unique physiology & anatomy.
Brain is highly vulnerable to disruption in blood flow.
The brain normally consumes glucose and oxygen, alternative substrates include
ketones, lactate, mannose, and others
75. 75
Acknowledgement
Firstly, I would like thanks Our Lord and Savior Jesus Christ Son of the
true Living God, Son of Theotokos.
Next my deepest gratitude goes to my instructor Dr. Abebaye Aragaw who
gave me this chance to prepare and present on “Cerebral Blood Flow.”
Finally, I would like to thank my classmates & the entire audience for
listening me attentively.
Habtemariam M.
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76. 76
References
Atlas of Human Anatomy (Netter Basic Science) 7th Edition
Monro A. Observations on the structure and functions of the nervous system. Edinburgh: William Creech;
1783.
Wright BL, Lai JT, Sinclair AJ (August 2012). "Cerebrospinal fluid and lumbar puncture: a practical
review". Journal of Neurology. 259 (8): 1530–45.
Guyton & Hall, Medical text book of Physiology, 13th ed.
Chapter 52 (pp. 580) Cerebral protection by Victoria Heaviside and Michelle Hayes
McCullough, Jock N., et al. "Cerebral metabolic suppression during hypothermic circulatory arrest in
humans." The Annals of thoracic surgery 67.6 (1999): 1895-1899.
Owen, O. E., et al. "Brain metabolism during fasting." The Journal of clinical investigation 46.10 (1967):
1589-1595.
SCHEINBERG, PERITZ, and HAROLD W. JAYNE. "Factors Influencing Cerebral Blood Flow and
Metabolism A Review." Circulation 5.2 (1952): 225-236.
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Monro-Kellie doctrine or the Monro-Kellie hypothesis: the relationship between the contents of the cranium and intracranial pressure, states that the sum of volumes of brain, cerebrospinal fluid (CSF) and intracerebral blood is constant.
An increase in one should cause a reciprocal decrease in either one or both of the remaining two.
The doctrine is fundamental to our understanding of the negative effect of raised intracranial pressure on the brain.
Circulation of brain was first described by Thomas Willis in 1664.
The four main arteries & their branches supply blood to the brain:
the left and right internal carotid arteries
the left and right vertebral arteries
external carotid artery Has several branch:
Superior thyroid artery
Ascending pharyngeal artery
Lingual artery
Facial artery
Occipital artery
Posterior auricular artery
Terminal branch:
Maxillary artery,
Superficial temporal artery
the cervical part in the neck has no branch
at cranial base, enter carotid canals with venous plexuses & carotid plexuses of sympathetic nerves.
The basilar artery travels immediately anterior to the pons and extends many branches prior to subdividing into the posterior cerebral arteries, which supply the posterior portion of the cerebrum.
Cerebral Arteries: branch of internal carotid artery
is formed between four arteries
i.e 2 vertebral & 2 internal carotid arteries
Limited flow through anastomotic site
Tortuous: Highly complex or intricate and occasionally devious
The level of blood flow to the gray matter is therefore four times as great as that to the white matter, matching the much higher metabolic needs of gray matter.
The glia limitans, or the glial limiting membrane, is a thin barrier of astrocyte foot processes associated with the parenchymal basal lamina surrounding the brain and spinal cord
Fenestrated having perforations, apertures, or transparent areas
Posterior pituitary Neurohypophysis): secretes the oxytocin & vasopressin in general circulation.
Area postrema: act as chemoreceptor trigger zone that initiates vomiting in response to chemical changes in plasma and AT-II acts on it to produce neutrally mediated increase in BP.
Median eminence: site of entry of hypothalamic hypophysiotropic hormones in to portal hypophysiotropic circulation.
SFO/OVLT: AT-II acts to increase water intake. . AT-II acts on it to produce neurally mediated increase in BP.
subarachnoid space (between the arachnoid mater and the pia mater)
CSF sample use: This can be used to test the intracranial pressure, as well as indicate diseases including infections of the brain or the surrounding meninges.
The ventricles are a series of cavities filled with CSF.
In 1914, Harvey Cushing demonstrated that the CSF was secreted by the choroid plexus.
The brain exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight, which would cut off blood supply and kill neurons in the lower sections without CSF.
CSF protects the brain tissue from injury when jolted or hit
4. For example, high glycine concentration disrupts temperature and BP control, and high CSF pH causes dizziness and syncope.
5. Metabolic waste products diffuse rapidly into CSF and are removed into the bloodstream as CSF is absorbed.
When this goes awry, CSF can be toxic, such as in amyotrophic lateral sclerosis, the commonest form of motor neuron disease.
IJV = Internal Jugular Vein ( Right & Left )
There are two sets of jugular veins: external and internal.
The left and right external jugular veins drain into the subclavian veins. The internal jugular veins join with the subclavian veins more medially to form the brachiocephalic veins.
Finally, the left and right brachiocephalic veins join to form the superior vena cava, which delivers deoxygenated blood to the right atrium of the heart.
Venography is an x-ray examination that uses an injection of contrast material to show how blood flows through your veins.
Vein sinus = A wide channel containing blood; does not have the coating of an ordinary blood vessel
In common usage, "sinus" usually refers to the paranasal sinuses.
Sinus is Latin for "bay", "pocket", "curve", or "bosom". In anatomy, the term is used in various contexts.
Sinuses in the body
Paranasal sinuses
Maxillary: cavities are located on either side of the nostrils (cheekbone areas).
Ethmoid: cavities which are located between the eyes.
Sphenoid: are located behind the eyes and lie in the deeper recesses of the skull.
Frontal: cavities which can be found above the eyes (more in the forehead region).
Dural venous sinuses
Anterior midline
Cavernous
Superior petrosal
Inferior petrosal
Central sulcus
Inferior sagittal
Superior sagittal
Straight
Confluence of sinuses
Lateral
Transverse
Sigmoid
Inferior
Occipital
Arterial sinuses
Carotid sinus
Organ-specific spaces
Costodiaphragmatic recess (lung/diaphragm sinus, also known as phrenicocostal sinus)
Renal sinus (drains renal medulla)
Coronary sinus (subdivisions of the pericardium)
Lymphatic spaces
Subcapsular sinus (space between the lymph node and capsule)
Trabecular sinuses (space around the invaginations of the lymphatic capsule)
Medullary sinuses (space between the lymphatic cortex and efferent lymphatic drainage)
vein of Galen = The Great Cerebral Vein
Cerebellum: is drained by superior & inferior cerebellar veins, which drain into transverse and sigmoid sinuses.
Cerebral viens cerebral venous sinuses IJV
15% resting Cardiac Output for Brain.
The normal cerebral blood flow in an adult averages
50 to 65 ml/100 g, or about 750 to 900 ml/min
Physiological considerations: Brain has high metabolic rate
(Rengachary, S.S. and Ellenbogen, R.G.,editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005)
Marked local fluctuations in CBF with local activity, but total CBF relatively constant.
CVR is inversely related to CBF.
CPP is directly related to CBF.
Blood Flow, Q = ΔP/Rv
CBF = CPP/CVR = ΔP(π.r4)/(8.η.L)
CVR = (8.η.L)/(π.r4)
Any factor affecting MAP (e.g. hemorrhage)
Working from Ohm's law (I = V/R), pressure is the product of resistance and flow:
Q = (Pa- Pv) / R
Central venous pressure (CVP) is the blood pressure in the venae cavae, near the right atrium of the heart.
CVP reflects the amount of blood returning to the heart and the ability of the heart to pump the blood back into the arterial system.
VMC = Vasomotor Center
The Cushing reflex is a physiological nervous system response to acute elevations of intracranial pressure (ICP), resulting in the Cushing triad of widened pulse pressure (increasing systolic, decreasing diastolic) bradycardia, and irregular respirations.
vasopressor response, the Cushing effect, the Cushing reaction = Harvey Williams Cushing (1869–1939), an American neurosurgeon.
Q = flow rate (volume/time); ΔP = pressure difference (mm Hg); R = resistance to flow (mm Hg x time/volume); r = inside radius of the vessel, L = vessel length, and η = blood viscosity
When ICP is constant, CPP varies directly with MAP. Hemodynamics is the study of blood flow.
Laminar Flow, type of fluid (gas or liquid) flow in which the fluid travels smoothly or in regular paths, in contrast to Turbulent Flow, in which the fluid undergoes irregular fluctuations and mixing.
The Hagen–Poiseuille equation describes the relationship between pressure, fluidic resistance and flow rate, analogous to voltage, resistance, and current, respectively, in Ohm's law for electrical circuits ( V = R I ). Both electrical resistance and fluidic resistance are proportional to the length of the device.
Analogy: An inference that if things agree in some respects they probably agree in others.
CVR = Cerebral Vascular resistance
Cerebral Autoregulation: is homeostatic process that regulates and maintains CBF constant and matched to cerebral metabolic demand across a range of blood pressures.
Endothelial Mechanism: NO, endothelial-derived hyperpolarizing factor = (EDHF), Prostacyclin = PGI2 , eicosanoids, and the endothelins
Bayliss effect or Bayliss myogenic response is a special manifestation of the myogenic tone in the vasculature. The Bayliss effect in vascular smooth muscles cells is a response to stretch.
This is especially relevant in arterioles of the body. When blood pressure is increased in the blood vessels and the blood vessels distend, they react with a constriction; this is the Bayliss effect.
Stretch of the muscle membrane opens a stretch-activated ion channel. The cells then become depolarized and this results in a Ca2+ signal and triggers muscle contraction. It is important to understand that no action potential is necessary here; the level of entered calcium affects the level of contraction proportionally and causes tonic contraction. The contracted state of the smooth muscle depends on the grade of stretch and plays an important part in the regulation of blood flow.
The myogenic mechanism is how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow constant within the blood vessel.
Myogenic response refers to a contraction initiated by the myocyte itself instead of an outside occurrence or stimulus such as nerve innervation.
Most often observed in (although not necessarily restricted to) smaller resistance arteries, this 'basal' myogenic tone may be useful in the regulation of organ blood flow and peripheral resistance, as it positions a vessel in a pre-constricted state that allows other factors to induce additional constriction or dilation to increase or decrease blood flow.
Pulsatile perfusion lowers cerebral vascular resistance (CVR).
Pulsatile flow can be defined as flow with a periodic pressure fluctuation wave traveling along the flow path.
Myogenic response refers to a contraction initiated by the myocyte itself instead of an outside occurrence or stimulus such as nerve innervation.
CBF = CPP/CVR
CPP = MAP − ICP
MAP = [1/3× (SBP −DBP)] + DBP
total peripheral resistance = MAP = CO x TPR, where CO stands for cardiac output, and MAP stands for mean arterial pressure
Central venous pressure (CVP) is the blood pressure in the venae cavae, near the right atrium of the heart. CVP reflects the amount of blood returning to the heart and the ability of the heart to pump the blood back into the arterial system.
Rheology is the study of the flow of matter, primarily in a liquid or gas state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force.
Lactate
Potassium
cerebral metabolic demand is high = substrate levels are low, metabolite levels are high,
cerebral metabolic demand is stable and perfusion pressure is changing, the same mechanisms ensure that blood flow remains constant and matched to demand.
CO2 is considered to be the most important physiologic variable in chemo-regulation.
beyond a CO2 of 55-60 mmHg, CBF autoregulation becomes significantly impaired within a physiologically normal range of BP.
Increased CO2 increased H+ Increased No synthesis cGMP
4. decreased CVR: decreased Ca2+ = smooth muscle relaxation
Obviously, this is undesirable if your brain is swollen and/or perfusion-compromised. Hence the neurointensivists' obsession with maintaining a stable (low-normal) CO2 in patients with various intracranial catastrophes.
Figure - cerebral blood flow with a stable perfusion pressure as CO2 increases
Carbon dioxide combines with water to form carbonic acid, which partially dissociates to form hydrogen ions.
Conversely, a fall in PaO2 results in vasodilation.
strenuous exercise or states of enhanced circulatory activity,
SNS impulses can constrict the large and intermediate-sized arteries and prevent the high pressure from reaching small blood vessels. - – important mechanism for preventing cerebral vascular hemorrhage.
sympathetic nervous system = SNS
Stork affect speech, movement, and memory.
Cerebral hypoxia: don’t have enough oxygen in your blood even if there’s enough blood flow……. confused or lethargic
Drowning, choking, suffocation, high altitudes, pulmonary diseases, anemia
cerebral hemorrhage include abnormally formed blood vessels, bleeding disorders, and head injuries
Most tissues of the body can go without oxygen for several minutes. During this time, the cells obtain their energy through anaerobic metabolism.
Because of the high metabolic rate of the brain, anaerobic breakdown of glycogen cannot supply the energy needed to sustain neuronal activity.
Under Normal Conditions, Most Brain Energy Is Supplied by Glucose Derived From the Blood
Delivery of oxygen
CMRO2: Cerebral Metabolic Rate of Oxygen: 3.8ml/100g/min
where
CBF is cerebral blood flow in ml/100g
1.39 is the oxygen-carrying capacity of haemoglobin
Hb is the haemoglobin concentration
SaO2 is the arterial oxygen saturation
SjvO2 is the jugular bulb oxygen saturation: measure of oxygen delivery and extraction to the brain
0.03 is the dissolved oxygen content, per ml of blood, per mmHg
PaO2 - PvO2 is the difference in partial pressures between arterial and venous blood
Because of their limited permeability across the BBB, they cannot substitute for plasma glucose to maintain brain function.
However, mannose is not normally present in the blood and cannot therefore be considered a physiological substrate for brain energy metabolism.
(thereby lactate production results in the consumption of protons).
Anaesthesia (eg. propofol or thiopentone) *** Amphetamines are synthetic stimulant drugs, which means they speed up the workings of the brain.
Hypothermia progressively depresses the CNS, decreasing CNS metabolism in a linear fashion as the core temperature drops.
At core temperatures less than 33°C, brain electrical activity becomes abnormal; between 19°C and 20°C, an electroencephalogram (EEG) may appear consistent with brain death.
Encephalitis is inflammation of the active tissues of the brain caused by an infection or an autoimmune response
Uremia is a buildup of toxins in your blood.
Myxedema = severely advanced hypothyroidism. It's a condition that occurs when your body doesn't produce enough thyroid hormone.
Intoxication organic acid and amino acid metabolism disorders.
Energy production primary lactic acidosis and fatty acid oxidation disorders.
Biosynthesis => Lysosomal and peroxisomal disorders
neurotransmitter pyridoxine-dependent epilepsy.