Cerebrum and CSF Notes

Cerebrum

  • Two things due tomorrow: quiz and activity with three attempts.

  • Today's focus: cerebrum, cerebrospinal fluid (CSF) functions, and unit 4 exam scope.

Unit 4 Exam Scope

  • Excludes the brainstem, except for its role in ascending tracts (e.g., medulla oblongata).

Final Exam

  • Semi-cumulative, with 30-40% cumulative content.

  • Treat as a new unit exam with additional questions.

  • Mainly multiple-choice, with short answers and extensive matching.

  • New material: Chapter 14 content not covered up to unit 4, starting with the brainstem and cranial nerves.

  • Lab exam is a week before the lecture final.

  • Extra student hours during the lecture exam week for final questions.

  • Review PowerPoint will cover keystone ideas for the cumulative part.

Brain Mechanics

  • Brain requires inhibition to control motor movements.

  • Limbic system is responsible for emotions and subjective feelings. The movie Inside Out is inspired by the limbic system.

  • Diencephalon includes structures with "thalamus" in their names.

Cerebrospinal Fluid (CSF)

  • Found in lateral ventricles, third ventricle (near the thalamus), fourth ventricle, and central canal of the spinal cord.

  • Also found under the arachnoid mater, serving as a cushion.

Functions of CSF

  • Buoyancy: Allows the central nervous system to float, preventing the brain from being crushed under its own weight. Human brains are large relative to body size, necessitating CSF for support.

  • Protection: Cushions the brain against jolts/stresses preventing it from striking the cranium.

  • Chemical Stability: Creates the right chemical environment for the CNS to function, regulating ion concentrations (Na+, K+, Cl-). CSF is not stagnant; it rinses away metabolic waste and returns it to the bloodstream, where the kidneys process it.

  • Homeostatic regulation of chemical environment, especially sodium, potassium, and chloride

Brain Barrier System

  • Ensures the CNS is perfused with blood for nutrients and oxygen.

  • Selectively restricts harmful substances from entering the brain.

  • Neurons have high ATP demand, requiring constant blood supply.

  • Interruption of blood flow:

    • 10 seconds: Loss of consciousness.

    • 4 minutes or more: Irreversible brain damage.

Selective Permeability

  • Highly permeable to water, glucose, and lipid-soluble substances (alcohol, caffeine, nicotine, anesthetics).

  • Oxygen and carbon dioxide diffuse easily without transport proteins.

Entry Points

  • General brain tissue via blood vessels.

  • Choroid plexus (for CSF production).

Protection Measures

  • Tight junctions between endothelial cells in brain capillaries.

  • Astrocytes surround capillaries, enhancing security; substances must pass through cells, not between them.

  • Choroid plexus includes tight junctions between ependymal cells, forming the blood-CSF barrier.

Forebrain

  • Includes the cerebrum and diencephalon.

Cerebrum

  • Divided into three layers: gray, white, gray.

    • Cerebral cortex (outer gray matter layer).

    • Cerebral white matter (contains extreme capsule, internal capsule, and corpus callosum).

    • Basal nuclei (deepest layer of gray matter, surrounding the thalamus).

Functions

  • Sensory perception (conscious awareness).

  • Memory.

  • Thought.

  • Judgment (develops last).

  • Voluntary motor actions.

Cerebral Cortex

  • Contains pyramidal cells, interneurons, and glial cells.

  • Responsible for feeling, voluntary movement, communication, memory, understanding, thought, and judgment.

Lobes of the Cortex

  • Five lobes: frontal, parietal, occipital, temporal, and insula.

Functional Regions

  • Sensory Areas: Conscious awareness of sensation (general somatosensory vs. specialized senses).

  • Motor Areas: Planning and initiation of voluntary motor functions (interneurons).

  • Association Areas: Integrating sensory and motor information.

Homunculus

  • Map of sensory and motor function in the brain, showing exaggerated areas for more sensitive or delicate movements.

Parietal Lobe

  • Postcentral gyrus: Primary somatosensory cortex for conscious awareness of cutaneous stimuli.

  • Somatosensory association area: Integrates sensory information from the gyrus.

Temporal Lobe

  • Primary auditory cortex and association cortex: For sense of hearing (audition).

Language Areas

  • Wernicke's area: Understanding of speech.

  • Broca's area: Formation of speech.

Occipital Lobe

  • Primary visual cortex and association cortex: For vision, color, and depth perception. Damage can lead to blindness.

Insula

  • Gustatory (taste) cortex and visceral sensations.

  • Sense of smell is near this area

Frontal Lobe

  • Prefrontal Cortex: Intellect, cognition, recall, judgment, consciousness, reasoning, and personality; develops last.

  • Precentral gyrus location of premotor Cortex: Planning of coordinated motor movement.

  • Primary Motor Cortex (precentral gyrus): Upper motor neurons originate here for descending tracts. Also contains Broca's area (motor speech).

Cerebral White Matter

  • Contains myelinated axons and tracts connecting different parts of the cortex and brain.

Types of Fibers

  • Commissural Fibers: Enable communication between hemispheres; the largest is the corpus callosum.

  • Association Fibers: Connect lobes or gyri within the same hemisphere.

  • Projection Fibers: Connect the cerebrum to lower brain centers and the spinal cord (ascending and descending tracts).

Basal Nuclei

  • Masses of gray matter deep in the white matter, lateral to the thalamus.

    • Work with the cerebral cortex for motor control: starting, stopping, and adjusting the intensity of movements, and suppressing undesired movements.

  • Consist of the caudate nucleus, putamen, and globus pallidus. This pathway is implicated in diseases like Parkinson's.

Limbic System

  • Emotional brain that spans a large distance in the cerebrum, forming a functional brain system.

    • Also responsible for learning and memory centres.

Includes

  • Fornix.

  • Centers for gratification (reward center) and aversion.

  • Cingulate gyrus: Expressing the emotion through gesture and ingraining societal views of gestures.

  • Hippocampus: Centers of our long term memory which is affected by stress.

  • Amygdala: Processes fear and emotional memories and it's an aversion center.

  • Mammillary body: Located in midbrain; part of the limbic system.