Brain Structure and Functions Quiz

Brain

• Brain and spinal cord develop from ectodermal neural tube
• Gyri = folds/convolutions (singular = gyrus)
• Fissures = deep grooves
• Inner mass = cerebral white matter
• Association tracts - conduct impulses between gyri in the same hemisphere
• Commissural tracts - conduct impulses between gyri in one hemisphere to another
• Projection tracts - conduct impulses to lower parts of the CNS
• White matter connected by a bundle of transverse white fibers = corpus callosum (connects the two hemispheres)
• Gray matter contains unmyelinated neurons, white matter contains myelinated neurons

Brain Organization

• Brain Stem - continuation of spinal cord; medulla oblongata, pons, midbrain
• Cerebellum - second largest part of brain; coordinates subconscious movements, contributes to muscle tone, posture, and balance
• Diencephalon - gives rise to the thalamus, hypothalamus, and epithalamus
• Cerebrum - newest and largest part of brain; perception, thought, imagination, judgment, decision-making occur in cerebral cortex

Brain Organization – Functions of Each Part

• DIENCEPHALON: Thalamus, Hypothalamus, Pineal gland (part of epithalamus), Midbrain, Pons, Medulla Oblongata
• CEREBELLUM
• CEREBRUM

Lobes of the Cerebrum

• Precentral gyrus: Anterior to central sulcus in anterior lobe; primary motor area of cerebral cortex
• Postcentral gyrus: Posterior to central sulcus in parietal lobe; primary somatosensory area of cerebral cortex
• Parieto-occipital sulcus: Separates parietal lobe from posterior-most occipital lobe
• Lateral cerebral sulcus (fissure): Separates frontal lobe from two laterally placed temporal lobes

The Cerebral Cortex - Functional Areas

• Brodmann's areas = numbered regions of cortex mapped to specific cognitive functions
• Sensory areas: Receive and interpret incoming sensory impulses; parietal lobe-touch, proprioception, pain, temperature, visual, auditory, taste, smell, etc.; occipital lobe-vision; temporal lobe-hearing, smell, etc.
• Motor areas: Mostly located in frontal lobe; control executions of voluntary movements
• Association areas: Interpret meaning of incoming sensory info; memory, emotions, reasoning, judgment, personality, intelligence; located between sensory and motor areas

The Cerebrum Details

• Brodmann's areas are numbered cortical tissue regions (cerebral cortex)
• Primary somatosensory area (Parietal lobe), visual area (Occipital lobe), auditory area (Temporal lobe)
• Primary motor area controls voluntary muscle contractions
• Motor cortex has a homunculus map (more cortical area for muscles involved in skilled, complex movement)

Association Areas Details

• Somatosensory: Determines exact shape/texture of object, relates present and past sensory experiences.
• Visual: Relates present and past visual experiences, recognizes and evaluates.
• Facial Recognition: Stores information about faces to recognize people.
• Auditory: Recognizes sound (speech, music, noise).
• Orbitofrontal Cortex: Identifies odors and discriminates among different orders.
• Wernicke's Area: Interprets spoken words and contributes to verbal communication by adding emotional content.
• Common Integrative Area: Integrates sensory interpretations forming thoughts (personality, intellect, complex learning).
• Prefrontal Cortex: Makeup of personality, intellect, complex learning abilities, recall, initiative, judgment, foresight, reasoning, conscience, intuition, future planning.
• Premotor Area: Causes specific muscle groups to contract, memory bank for such movements.

The Diencephalon

• Located near midline of brain, above midbrain
• Thalamus, Hypothalamus, epithalamus (pineal gland)
• Diencephalon surrounds the 3rd ventricle; acts as a relay station
• Also regulates body rhythms, emotions, secretes hormones

Thalamus

• Pair of oval masses of gray matter, on either side of 3rd ventricle roof.
• Serves as "relay stations" for all sensory impulses (except smell)
• Nuclei for hearing, vision, taste, somatic sensations (touch, pressure, vibration, temperature, pain), voluntary motor actions, arousal, emotions, and memory.
• Registers conscious recognition of pain, temperature, light touch & pressure.

Hypothalamus

• Located below the thalamus
• Regulates many body functions (homeostasis)
• Control center & integrator of Autonomic Nervous System.
• Connection between Nervous & Endocrine systems.
• Detects changes in body and releases regulating factors (hormones).
• Involved in emotions (rage, aggression, pain, pleasure); body temperature regulation, hunger/satiety, thirst, and diurnal rhythms (sleep/wake).

Pineal Gland

• Located at midline of epithalamus in 3rd ventricle (looks like a tiny pine cone)
• Secretes melatonin involved in diurnal cycles (sleepiness)

The Pons

• Superior to medulla
• "Bridges" or connects spinal cord with brain and other brain regions.
• (Peduncle) A stem-like connecting part.
• Relays nerve impulses related to voluntary skeletal movements from cerebral cortex to cerebellum.
• Contains pontine respiratory group (pneumotaxic & apneustic areas)

The Medulla Oblongata

• Posterior side = 2 prominent nuclei (gracilis & cuneatus) containing sensory tract cell bodies.
• Crossing over of sensory pathways (nuclei) occurs here.
• Scattered nuclei (gray matter) form reflex centers: Cardiovascular center (heart rate/vasoconstriction), Medullary rhythmicity area (respiration), and non-vital reflexes (swallowing, coughing, vomiting, sneezing, hiccupping).
• Contains olive (fine motor control, equilibrium, & posture).

The Midbrain

• Separated into tectum and tegmentum (roof and floor).
• Tectum- Regulates auditory and visual reflexes. Contains corpora quadrigemina (4 rounded elevations): Superior colliculi (eye, head, neck movements), and Inferior colliculi (head, trunk movements).
• Tegmentum- Contains nuclei that receive & send information via cranial nerves.

The Cerebellum

• Second largest part of the brain ("little brain").
• Covered in gyri and sulci (folds).
• Responsible for comparing cerebrum info with sensory feedback from periphery (through spinal cord).
• Controls subconscious skeletal muscle movements (muscle tone, posture, balance).
• Receives sensory impulses from proprioceptors and visual receptors to adjust muscle contractions.
• Involved in equilibrium (balance).

Circulation and the CNS

• Has a privileged blood supply - contents of blood cannot simply pass through CNS.
• Blood Brain Barrier - specialized structure.
• Brain is ~2% of total body weight but uses ~20% of total oxygen.
• Blood flows to brain via common carotid arteries and branch into internal carotid and vertebral arteries (merge to form basilar artery)
• Circle of Willis – composed of R and L carotid arteries & branches of basilar artery creating a confluence of arteries, allowing for perfusion.

Protective Coverings

• Cranial dura mater - two layers (external periosteal & internal meningeal).
• Extensions of dura mater form hard, non-compliant membranes:
  • Falx cerebri - separates two cerebral hemispheres.
  • Falx cerebelli - separates two cerebellar hemispheres
  • Tentorium cerebelli - separates cerebrum from cerebellum

Choroid Plexus

• Capillary networks in the ventricles.
• Capillaries covered with ependymal cells, joined by tight junctions.
• CSF (Cerebrospinal Fluid) formed by filtration of blood plasma through these cells.
• Blood Brain Barrier (BBB) allows certain substances into CSF excluding harmful ones (astrocytes may be involved).

CSF (Cerebrospinal Fluid)

• Circulates through ventricles via foramina to subarachnoid space then absorbed into arachnoid villi/granulation.
• CSF leaves the 4th ventricle via 1 median & 2 lateral apertures (spinal cord).
• CSF gets reabsorbed into arachnoid villi into blood sinuses (superior sagittal sinus).
• CSF produced & reabsorbed at about the same rate as choroid plexuses.
• Clear, colorless, contains water, glucose, proteins, urea, ions, few WBC, total volume 80-150 mL (480 mL produced/reabsorbed daily).
• CSF is protective & nourishes CNS (nutrients & waste removal). Functions in circulation, homeostasis, and protection.

Causes of Neurological Deficits

• Cerebrovascular accident (CVA) (stroke): Blood circulation blocked, brain tissue dies.
• Ischemic stroke, TIA (transient ischemic attack), hemorrhagic stroke (greatest risk factor is hypertension)
• Neurodegenerative diseases (Alzheimer's, Parkinson's, Huntington's, ALS, Creutzfeld-Jacob, multiple sclerosis)
• Developmental disorders (Autism spectrum disorder (ASD), Attention Deficit Hyperactivity Disorder).

Cranial Nerves

• 12 cranial nerves serve head and neck.
• Cranial nerve X - A (Autonomic) functions in thoracic/superior abdominal cavities. Special senses, general senses.
• Allows directed tests for forebrain & brain stem structures.

Cranial Nerves and Tests:

• Olfactory (CN I): Coffee/mint smells (anosmia)

• Optic (CN II): Snellen chart

• Oculomotor (CN III): Gaze control

• Trochlear (CN IV): Gaze control

• Trigeminal (CN V): Sensory discrimination

• Facial (CN VII): Taste differentiation

• Vestibulocochlear (CN VIII): Rinne, Romberg test

• Glossopharyngeal (CN IX): Taste differentiation, gag reflex

• Vagus (CN X): Repeating consonant sounds

• Spinal accessory (CN XI): Shoulder shrug

• Hypoglossal (CN XII): Tongue protrusion

Sensory Exam

• Somatic senses (skin, muscles, tendons, conscious perception of body interactions)
• Visceral senses (organs, homeostatic regulation through autonomic nervous system)

Motor Exam

• Skeletomuscular system includes upper and lower motor neurons (activation for voluntary movement).
• Motor exam evaluates function of neurons and muscles (tone, passive range of motion/resting tension, muscle bulk, strength, agonists vs antagonists)

Mental Status

• Level of alertness, awareness, degree of interaction, orientation (place/time), following commands.
• Differences from baseline are noted.
• Orientation and memory (awareness of time, amnesia (anterograde, retrograde), episodic, procedural, short term memory).
• Language & Speech (understand language, fluency/coherency, prosody).

Coordination Test

• Tests for proper cerebellar function (separate set of tests w/ walking).
• Subtests target: Appendicular/axial musculature (posture & gait)
• Appendicular (Tremor check, Check reflex, Finger-to-nose/alternation of muscle movements, rapid alternating movements, speech consonants)
• Axial musculoskeletal musculature (posture & gait)
• Cerebellum (helps with smooth, coordinated body movement.)

Gait

• Can be separate part of neurological exam or subset.
• Ataxia requires multiple levels of the nervous system to be intact.

Test your knowledge on the anatomy and functions of the brain, including key components such as the corpus callosum, cerebellum, and various lobes. This quiz will cover important areas involved in sensory processing and speech comprehension. Perfect for students studying neuroscience or human anatomy.