Brain Anatomy: Regions and Functions

Brain Lecture Introduction

• Brain anatomy is closely tied to lab material, requiring students to learn the physical structures and their locations.
• Physiology of the brain is presented in a relatively simple manner, focusing on specific areas and their functions.
• Rote memorization is key for learning brain anatomy and physiology.
• Flashcards and drawings are recommended study tools, especially for kinesthetic learners.

Brain Anatomy: Four Main Regions

• The brain is divided into four main regions: cerebrum, diencephalon, brain stem, and cerebellum.
• Cerebrum is the largest part of the brain, divided into two hemispheres and five lobes.
• Diencephalon is located under the cerebrum and is not visible from the brain's surface without a mid-sagittal section.
• Brain stem connects the brain to the spinal cord.
• Cerebellum is a separate part located at the back of the brain
• Knowing which parts fall into each region is important for both lecture and lab.

Brain Anatomy: Gyri, Sulci, Gray Matter, White Matter

• The brain's surface is folded, with ridges called gyri and depressions called sulci.
• A deep sulcus is called a fissure.
• Gray matter contains neuron cell bodies, dendrites, and unmyelinated axons
• Gray matter is superficial in the brain, forming the cortex
• In the spinal cord the gray matter is located deeper
• A cluster of cell bodies in the brain or spinal cord is called a nucleus
• White matter consists of myelinated axons.
• White matter is deep in the brain
• Tracts are groupings of myelinated axons in the central nervous system

Brain Development: Neurulation

• Neurulation, the process of forming nervous tissue, begins in the third week of embryonic development.
• The notochord causes the neural plate to form, which then becomes the neural tube.
• The neural tube develops into the entire central nervous system.
• The neural plate becomes the neural groove, and cells on the margins of the groove become neural folds.
• Cells at the tip of the neural folds become neural crest cells.
• By the fourth week of development, the neural tube is formed
• Low levels of B12 and folate in the pregnant individual can increase the risk of neural tube defects.
• Neural tube defects result from the neural tube not closing completely.
• Anencephaly is a severe neural tube defect involving complete or substantial absence of the brain, not compatible with life
• Spina bifida occurs when part of the neural tube does not close, specifically the tail end of the spinal cord
• Spina bifida cystica involves a large cyst forming due to the vertebral arch not forming, often resulting in paralysis of the lower limbs.
• Spina bifida occulta is a partial defect of the vertebral arch without a cyst, often not serious and may go unnoticed.

Brain Development: Primary and Secondary Vesicles

• By the end of the fourth week, the neural tube has formed.
• The neural tube develops three distinct regions or primary vesicles: prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain).
• By the fifth week, five secondary vesicles have formed: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.
• The telencephalon becomes the cerebrum.
• The diencephalon becomes more specialized into regions.
• The mesencephalon becomes the midbrain.
• The metencephalon becomes the pons and the cerebellum.
• The myelencephalon becomes the medulla oblongata.
• The midbrain, pons, and medulla oblongata form the brain stem.
• During the second trimester (13-26 weeks), the telencephalon grows around the diencephalon.
• Gyri develop during the second trimester.
• At birth, the brain is enclosed in the cranial cavity, and most gyri and sulci are fully developed.

Brain Protection: Bones, Meninges, CSF, BBB

• The brain is protected by the bones of the skull.
• Meninges are connective tissue layers surrounding the central nervous system.
• From superficial to deep, the meninges are dura mater, arachnoid mater, and pia mater.
• Cerebrospinal fluid (CSF) is found between the arachnoid and pia mater.
• The blood-brain barrier (BBB) protects the brain by limiting what can enter.

The Meninges

• The dura mater is the thick, outer membrane made of dense irregular connective tissue, consisting of two layers
• The arachnoid mater is the middle layer, resembling a spider web with collagen and elastic fibers.
• Small space between Pia and Arachnoid Mater is the subarachnoid space
• Cerebrospinal fluid is located in Subarachnoid Space
• There is a potential space called the subdural space between dura and arachnoid mater
• the innermost layer that cannot be removed, made of areolar connective tissue

Meninges: Spaces, Hematomas, Meningitis

• The potential epidural space is located outside the dura mater.
• An epidural hematoma involves blood pooling in the epidural space and requires immediate treatment.
• A subdural hematoma involves a slower bleed into the subdural space.
• Meningitis is inflammation of the meninges, caused by bacteria, viruses, or fungi and symptoms include fever, headache, stiff neck, and vomiting.
• Untreated meningitis can result in brain damage or death.

Brain: Dural Septa & Ventricles

• Dural septa are partitions formed by the dura mater extending into the cranial cavity between brain parts.
• Key dural septa include the falx cerebri located in the longitudinal fissure of the cerebrum, the tentorium cerebelli over the cerebellum, and the falx cerebelli midline in the cerebellum.
• Superior and inferior sagittal sinuses are found within the falx cerebri, transverse and straight sinuses in the tentorium cerebelli, and the occipital sinus in the falx cerebelli.
• Ventricles are cavities within the brain lined with ependymal cells and filled with cerebrospinal fluid (CSF).
• Ventricles include the two lateral ventricles in the cerebral hemispheres (separated by the septum pellucidum), the third ventricle in the diencephalon, and the fourth ventricle between the pons and the cerebellum.

CSF & the Blood Brain Barrier

• Cerebrospinal fluid (CSF) is a clear, colorless liquid between the arachnoid and pia mater, providing cushioning and transporting nutrients and waste.
• CSF reduces the brain's apparent weight by 95%.
• CSF is made of glucose, water, and salt.
• CSF is recycled into the dural venis sinuses
• Ependymal cells in the choroid plexus, located in the ventricles, continuously form and reabsorb CSF.
• Hydrocephalus results from overproduction or insufficient drainage of CSF, leading to brain tissue distortion.
• The blood-brain barrier (BBB) is made of capillaries covered in astrocytes, regulating substance entry and certain regions, such as the choroid plexus, hypothalamus, and pineal gland, have less effective barriers.

Brain: The Cerebrum

• The cerebrum is the main part of the brain responsible for complex intellectual functions, intelligence, reasoning, thoughts, memories, judgments, voluntary skeletal muscle control, and conscious perception of senses.
• The cerebrum consists of two hemispheres: right and left, separated by the longitudinal fissure; connected by the corpus callosum.
• Hemispheres receive sensation and control motor function from the opposite side of the body.
• The cerebrum has five lobes: frontal, parietal, temporal, occipital, and insula
• Parietal, temporal, and insula are paired lobes

Brain Lobes: Frontal Lobe

• The frontal lobe, located in front of the central sulcus, contains the precentral gyrus, an area where Primary motor control happens
• Motor control includes eye movements for reading and binocular vision.
• Function of frontal lobe includes concentration, verbal communication (Broca area), decision-making
• Planning, judgement, and personality happen in the prefrontal cortex

Brain Lobes: Parietal, Temporal, Occipital, Insula

• Parietal lobes - posterior to the central sulcus, postcentral gyrus processes Ssensory information from the opposite side of the body.
• Parietal Lobes function includes touch, pressure, pain, temperature
• Temporal lobe - hearing (primary auditory cortex and association area) and smell (olfactory cortex)
• In Temporal lobe the Wernicke area comprehends languag
• Occipital lobe - processes Vision (primary visual cortex) and associates / integrates that vision
• Inability to recognize faces depends on this association area
• Insula - deep within the lateral sulcus which is about memory and taste (gustatory cortex)

Brain Disorder: Autism Spectrum Disorder

• Autism Spectrum Disorder (ASD) - characterized by difficulties in social interaction and communication and repetitive behavioral patterns
• Manifestations and severity varies amongst individuals (spectrum)
• Causes - scientifically not well-understood, controversy around factors

Brain: White Matter Tracts, Stroke

• Association tracts - connect regions of the cortex within the same hemisphere, including close areas, and longitudinal tracts, which span the whole hemisphere
• Commissural tracts connect opposite hemispheres; this is what the area called Corpus Collusum does
• Projection tracts - link the cortex to the rest of the brain and spinal cord, crossing over in the brain stem in the internal capsule region of the brain
• right-handed people tend to have right frontal and left occipital protrusions; left-handed people have the opposite
• Left hemisphere = categorical (language, categorizing, analyzing)
• Right hemisphere - representational (abstract relationships, visual-spatial, imagination, comparing senses).
• Lateralization is developed by age five or six
• stroke – medical condition triggered by blocked blood flow to the brain or bleeding in the brain tissue preventing function, can be treated if acted upon within the first 3 hours

Cerebrum: Stroke, Cerebral Nuclei

• Stroke - reduced blood supply to the brain, leading to potential tissue death
• Stroke Symptoms - blurred vision, weakness, headache dizziness, difficulty walking (BE FAST pneumonic = balance (issues), eyes (visual changes), face (drooping), arms (weakness), speech (difficulty), time (call 911)
• Cerebral nuclei - areas in the cerebrum regulating motor output
• Caudate nucleus - part of the area that controls pattern and rhythm of crawling arm-swinging and walking
• Lentiform nucleus (putamen and globus pallidus)- controls and is responsible for subconscious movements and muscle tone
• Claustrum - controls consciousness level
• Amygdala - controls and influences mood and emotions

Brain: Diencephalon

• Diencephalon contains areas called Thalamus, Hypothalamus and Epithalamus
• Epithalamus includes the pineal gland (secretes melatonin and regulates the sleep wake cycle) and habenular nucleus (visceral and emotional responses to odors)
• Thalamus (relay point for sensory information except olfaction)
• Filtering for Sensory information by filtering out and disregarding minor distractions
• Hypothalamus control point for the autonomic nervous system and the endocrine system connects too Pituitary glands using a stock called the infundibulum

Diencephalon: Hypothalamus Cont.

• Hypothalamus function - regulates body temperature, hunger, and thirst, impacts blood pressure,
• Hypothalamus tells the pineal gland to secrete melatonin in order to regulate that sleep wake cycle
• Hypothalamus controls emotional responses

Brain: Brain Stem/Midbrain

• Brain stem connects the cerebrum, diencephalon, and cerebellum to the spinal cord
• Brain stem also contains both ascending and descending tracts of sensory and motor functions
• The three areas in the brain stem structure - midbrain, pons, and medulla oblongata
• The midbrain connects to the cerebellum; contains motor tracts from the primary motor cortex
• The substantia nigra produces dopamine(responsible for for movement emotions Pleasure and Pain responses)
• Two of our cranial nerves originate in Midbrain
• Tectum (superior and inferior colliculi for visual and auditory reflexes turn/ move head to loud noises
• Parkinson’s disease -- related to the destruction of an area of midbrain structure or substantia nigra region thus not being able to produce dopamine

Brain: Pons and Medulla Oblongata

• Pons Contains some of our cranial nerves V-VIII and helps with the communication between different part of the brain stem plus other areas
• Pontine respiratory center (skeletal muscles of breathing
• Superior olivary nuclei (localize sounds)
• Medulla Oblongata (sensory/motor information running through) Contrains pattern (pyramids motor control) Olive: (proprioception) coming from cerebellum helps with what the bodies doing in space,
• The medulla oblongata contains a Cardiovascular center (cardiac and vasomotor); Blood Pressure and Heart beats regulatory
• Respiratory center (breathing rate regulatory) Nuclei (cough, sneeze, vomit, salivate, swallow) Cranial nerves (rest of them)

Brain: Cerebellum & Limbic System

• Cerebellum: located in back little part by the brain and the spinal connection is little smaller has two hemispheres connected by the center area a vermis
• Cerebellum Cortex: outside is gray Matter with the white Matter deep in the arboreal or our tree of like connection
• Cerebellum Functions controls equilibrium and helps to make sure our muscle activities are following the right patterns to do what we want to do
• Planning motor there and helps send out appropriate motor information and correct and get sensory feedback to correct and maintain the best motor control
• Limbic system combines the different areas of different portions of the brain to process experience to a certain emotion
• Hippocampus (long-term memories and location of ability to create new neuron which is special and unique to this brain space for learning

Brain: Amygdala, Reticular Formation, Development

• Amygdala in Limbic System (emotions and memory, especially fear) linked to past stored events with sensory to specific emotion that will create and strong connection between triggers such as smells, certain location, time periods
• Reticular formation = Muscle: tone sensory (reticular activating system, alert/more aware/ and high state of conscious)

Brain: Development and Myelination

• The CNS requires Myelination which happens more frequently right after we are born and we can start to see changes almost a year for the new born and we begin to start refining them by the age to 5 can have fine muscle that are controlled and utilized over and over again
• After 5 there is refinement where we lose or gain depending on if we use a skill
• Sleep: help support Myeliniation along brain development Non-REM sleep (rest) - 75% you sleeping during sleep cycles to renew growth/ conserve energy to begin to work again

Brain: REM Sleep & Cognition

• REM sleep (rapid eye movement = 25 percent = active time Dream consolidates.
• Cognition (mental processes, awareness, knowledge, memory, perception and thinking)
• cognition: with damages to those a lack information to associate, may result in Agnosia (unite you do not recognize or use them appropriately

Memory

• Brain's Memory - different types all important but work with another based on connection and stimulus
• Temporary memory - 3 types -Sensory (few seconds the information sensory imputes and associate with stimuli) -Short term - limit 7 and that may change your information/stimuli (that may last from a few second to a couples hours) to long term Memory from repetition
  • Long term- retrieved or remember the connection is always there in is the basis of learning a study

Brain Language and Cranial Nerves

• Brain = language = area to generate stimuli that will be process by our sensory systems Wernicke = Interpret stimuli area; speaking/ write read understand etc if damage prevent function with language and stimuli
• Cranial Nerves = 12 pair part of the peripheral system with numbers that are roman must use roman numbers to assign which nerve based on functions

Cranial Nerves Pneumonics

• Names of nerves:
• "Old Opie occasionally tries trigonometry and feels very gloomy vague and hypoactive"
• Sensory motor or Both area
• “Some say marry money but my brother says big brains matter more"