Neuroscience Quiz on Brain Structure

Objectives

• Outline the development of the Central Nervous System (CNS)
• List the functions of the brain
• Discuss surface anatomy of the brain
• Describe the regions of the Brain
• Describe the protection of the CNS
• Discuss the anatomy and physiology of the Spinal Cord

Introduction

• The central nervous system (CNS) consists of the brain and spinal cord.
• The brainstem connects the brain to the spinal cord.

Parts of the brain...the cerebrum

• Taking up 7/8ths of the brain's weight, the cerebrum governs all sensory and motor activity.
• This includes sensory perception, emotions, consciousness, memory, and voluntary movements.
• It is divided into the left and right hemispheres.

Central Nervous System (CNS)

• CNS develops from the ectoderm surface to produce the embryonic neural tube.
• The neural tube becomes the brain and spinal cord.
• The opening of the neural tube becomes the ventricles.
• Four chambers within the brain are filled with cerebrospinal fluid.

Brain Overview

• Functions of the brain:
  • Makes decisions
  • Interprets sensations
  • Coordinates muscular movements
  • Determines perception
  • Stores memory
  • Reasoning
  • Regulates visceral activities
  • Determines personality

Surface anatomy

• Gyri (sing gyrus): Elevated ridges, entire surface
• Grooves separate gyri
• Sulci are shallow grooves (sing sulcus)
• Deeper grooves are fissures

Surface anatomy Cont'd

• Longitudinal: separates the cerebral hemispheres
• Transverse: separates cerebrum from cerebellum
• Corpus callosum: connects cerebral hemispheres

Regions of the Brain

• Cerebral hemispheres
• Diencephalon
• Brainstem
• Cerebellum

Lobes of the Cerebrum

• Five (5) lobes bilaterally:
  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe
  • Insula (buried deep in lateral sulcus)

Cerebral hemispheres

• Divided by longitudinal fissure into right & left sides.
• Central sulcus divides frontal from parietal lobes.

Lateral sulcus

• Separates temporal lobe from parietal lobe.
• Parieto-occipital sulcus divides occipital and parietal lobes.

Cerebral cortex

• Executive functioning capability.
• Gray matter: Neuron cell bodies, dendrites, associated glia, blood vessels and short unmyelinated axons.
• 100 billion neurons with an average of 10,000 contacts each.
• No fiber tracts (would be white).
• 2-4 mm thick (about 1/8 inch).
• Brodmann areas (historical: 52 structurally different areas given)

Cerebral cortex

• All the neurons are interneurons.
• By definition confined to the CNS.
• Three kinds of functional areas:
  • Motor areas: movement
  • Sensory areas: perception
  • Association areas: integrate diverse information to enable purposeful action.

Motor Areas (pre-central sulcus)

• Primary motor area
  • Frontal lobes
  • Control voluntary muscles
• Broca's area
  • Anterior to primary motor cortex
  • Usually in left hemisphere
  • Controls muscles needed for speech
• Frontal eye field
  • Above Broca's area
  • Controls voluntary movements of eyes & eyelids

Sensory Areas (post-central sulcus)

• Cutaneous sensory area - Parietal lobe: Interprets sensations on skin
• Visual area - Occipital lobe: Interprets vision
• Auditory area - Temporal lobe: Interprets hearing

Association Areas

• Regions that are not primary motor or primary sensory areas.
• Widespread throughout the cerebral cortex.
• Analyze and interpret sensory experiences.
• Provide memory, reasoning, verbalization, judgment, emotions.
• Frontal lobe association areas: concentrating, planning, complex problem-solving
• Parietal lobe association areas: understanding speech, choosing words to express thought
• Temporal lobe association areas: interpret complex sensory experiences, store memories, patterns
• Occipital lobe association areas: analyze and combine visual images and sensory experiences

Functions of the Cerebrum

• Interpreting impulses
• Initiating voluntary movements
• Storing information as memory
• Retrieving stored information
• Reasoning
• Seat of intelligence and personality

The Cerebrum

• The cortex is divided into 4 lobes: frontal lobe specializes in motor activity, personality, and speech; parietal lobe is where language, temperature, pressure, and touch are interpreted; temporal lobe contains centers for hearing, smell, and language input; occipital lobe specializes in vision.

Functions of the Cerebral Lobes

• Frontal lobes: Association areas carry on higher intellectual processes, concentrating, planning, complex problem solving. Motor areas control movements of voluntary skeletal muscles.
• Parietal lobes: Sensory areas provide sensations of temperature, touch, pressure, and pain.
• Temporal lobes: Sensory areas are responsible for hearing, association areas interpret sensory experiences, and remember visual scenes.
• Occipital lobes: Sensory areas are responsible for vision, association areas combine visual images with other sensory experiences.

Homunculus – “little man"

• Body map: human body spatially represented.
• Where on cortex: upside down.

Hemisphere Dominance

• The left hemisphere is dominant in most individuals
• Dominant hemisphere controls:
  • Speech
  • Writing
  • Reading
  • Verbal skills
  • Analytical skills
  • Computational skills
• Nondominant hemisphere controls:
  • Nonverbal tasks
  • Motor tasks
  • Understanding and interpreting musical and visual patterns
  • Provides emotional and intuitive thought processes

Diencephalon

• Sits on top of the brain stem and is enclosed by the cerebral hemispheres.
• Made of three parts:
  • Thalamus
  • Hypothalamus
  • Epithalamus

Diencephalon Cont'd

• Thalamus: Gateway for sensory impulses heading to cerebral cortex; sensory relay station; receives all sensory impulses (except smell); channels impulses to appropriate part of cerebral cortex for interpretation.
• Hypothalamus: Maintains homeostasis by regulating visceral activities (like HR, BP, temperature, H₂O & electrolyte balance, hunger, thirst, sleep & wakefulness); links nervous and endocrine systems.
• Epithalamus: Forms the roof of the third ventricle; houses the pineal body (an endocrine gland) that produces melatonin signaling nighttime sleep; includes the choroid plexus which forms cerebrospinal fluid.

Brainstem

• Three parts:
  • Midbrain
  • Pons
  • Medulla Oblongata

Midbrain

• Between diencephalon and pons
• Contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain.
• Cerebral aqueduct: bundles of nerve fibers.
• Corpora quadrigemina: centers for visual and auditory reflexes.

Pons

• Rounded bulge on underside of brainstem
• Between medulla oblongata and midbrain.
• Helps regulate rate and depth of breathing.
• Relays nerve impulses – longitudinally & ventrally.

Medulla Oblongata

• Enlarged continuation of spinal cord
• Conducts ascending and descending impulses between brain and spinal cord.
• Contains cardiac, vasomotor, and respiratory control centers.
• Contains various nonvital reflex control centers like coughing, sneezing, swallowing, and vomiting.

The Cerebellum

• The cerebellum is the second largest part of the brain.
• It contains nerve fibers that connect it to every part of the central nervous system.
• It coordinates voluntary and involuntary patterns of movements.
• It also adjusts muscles to automatically maintain posture

Cerebellum

• Inferior to occipital lobes
• Posterior to pons and medulla oblongata
• Two hemispheres
• Vermis connects hemispheres
• Cerebellar cortex (gray matter)
• Arbor vitae (white matter)
• Cerebellar peduncles (nerve fiber tracts)
• Integrates sensory information concerning position of body parts.
• Coordinates skeletal muscle activity.

Functions of cerebellum

• Smooths, coordinates, and fine-tunes bodily movements.
• Helps maintain body posture.
• Helps maintain equilibrium.
• Gets info from cerebrum re: movements being planned
• Gets info from inner ear re: equilibrium
• Gets info from proprioceptors (sensory receptors) informing where the parts of the body actually are.
• Using feedback, adjustments are made
• Also some role in cognition.
• Damage can cause ataxia, incoordination, wide-based gait, overshooting and proprioception problems.

Major Parts of the Brain

• Detailed breakdown of each part and its functions (Cerebrum, Basal nuclei, Diencephalon, Brainstem, Cerebellum).

Functional Brain Systems

• Networks of distant neurons that function together.
• Limbic system
• Reticular formation

The Limbic System

• Consists of:
  • Portions of frontal lobe
  • Portions of temporal lobe
  • Hypothalamus
  • Thalamus
  • Basal nuclei (motor control)
  • Other deep nuclei
• Functions:
  • Controls emotional experiences
  • Produces feelings like rage, anger, pleasure
  • Survival behaviors
  • Interprets sensory impulses associated with smell.

Limbic System Cont'd

• Called the "emotional" brain
• Essential for flexible, stable, and adaptive functioning
• Links different areas so integration can occur
• Processes emotions & allocates attentional resources.
• Necessary for emotional balance and adaptation to environmental demands (including fearful situations).
• Enables meaningful connections with others by interpreting facial expressions and responding appropriately.

Reticular formation

• Runs through central core of medulla, pons, and midbrain
• Reticular activating system (RAS) keeps the cerebral cortex alert and conscious.
• Some motor control.

Lifespan Changes

• Brain cells begin to die before birth.
• Over average lifetime, brain shrinks 10%.
• Most cell death occurs in temporal lobes.
• By age 90, frontal cortex has lost half its neurons.
• Number of dendritic branches decreases.
• Decreased levels of neurotransmitters.
• Fading memory.
• Slowed responses and reflexes.
• Increased risk of falling.
• Changes in sleep patterns that result in fewer sleeping hours.

Protection of the Central Nervous System

• Scalp and skin
• Skull and vertebral column
• Meninges
• Cerebrospinal fluid
• Blood brain barrier

Meninges

• Cover and protect CNS.
• Protect blood vessels.
• Contains CSF.
• Forms partitions in the skull.

Menignes

• Dura mater: 2 layers of fibrous connective tissue (periosteal and meningeal)
• Arachnoid mater: deep to arachnoid is subarachnoid space filled with CSF; Superiorly ,forms arachnoid villi - CSF valves.
• Pia mater is delicate and clings to brain following convolutions

Dura mater - dural partitions

• Falx cerebri (in longitudinal fissure)
• Falx cerebelli (runs vertically along vermis of cerebellum)
• Tentorium cerebelli (sheet in transverse fissure between cerebrum & cerebellum)

Ventricles

• Central cavities expanded, filled with CSF (cerebrospinal fluid).
• Lined by ependymal cells (these cells lining the choroid plexus make the CSF).
• Continuous with each other and central canal of spinal cord.
• Lateral, Third, and Fourth ventricles

Cerebrospinal Fluid

• A colorless fluid produced in the ventricles of the brain.
• Surrounds the brain and spinal cord cushioning them from injury.
• Maintained at a level of around 1/2 - 2/3 cup.
• Secreted by the choroid plexuses of ventricles.
• Filtration of plasma from capillaries through ependymal cells (electrolytes and glucose).
• Circulates in ventricles, central canal, and subarachnoid space.

Lateral ventricles, Third ventricle, Fourth ventricle

• Details of their locations and structures.

Spinal Cord

• Extends downward through vertebral canal.
• Begins at the foramen magnum and terminates at the first and second lumbar vertebrae (L1/L2) interspace.
• Below the interspace is the cauda equina (collection of spinal nerves).
• Enlargements occur in the cervical and lumbar regions.

Spinal Cord Anatomy

• Exterior white matter - conduction tracts
• Internal gray matter - mostly cell bodies
• Dorsal (posterior) horns
• Anterior (ventral) horns
• Central canal filled with cerebrospinal fluid
• Meninges cover the spinal cord
• Nerves leave at the level of each vertebra
• Dorsal root: associated with the dorsal root ganglia - collections of cell bodies outside the central nervous system.
• Ventral root

Functions of Spinal Cord

• Conduit for nerve impulses to and from the brain and brainstem.
• Center for spinal reflexes.

Tracts of the Spinal Cord

• Ascending tracts conduct sensory impulses to the brain while descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands
  • Detailed list of named tracts

Traumatic Brain Injuries (TBI)

• Concussion: Slight or mild injury, bleeding or tearing of nerve fibers. Recovery likely with some memory loss.
• Contusion: More severe TBI, nervous tissue destruction, may compress and kill brain tissue.
• Cerebral edema: Swelling from the inflammatory response.

Cerebrovascular Accident (CVA)

• Commonly called a stroke
• The result of a ruptured blood vessel supplying a region of the brain.
• Brain tissue supplied with oxygen from that blood source dies.
• Loss of some functions or death may result.

Alzheimer's Disease

• Progressive degenerative brain disease.
• Mostly seen in the elderly, but may begin in middle age.
• Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons.
• Victims experience memory loss, irritability, confusion and ultimately, hallucinations and death.

Types of Sleep

• Slow wave (Non-REM): Person tired, decreasing activity of reticular system, restful, dreamless, reduced blood pressure and respiratory rate, ranges from light to heavy.
• Rapid eye movement (REM): Paradoxical sleep, some areas of brain active, heart and respiratory rates irregular, dreaming occurs.

Memory

• Short-term memory (Working memory): Closed neuronal circuit, circuit is stimulated over & over. When impulse flow ceases, memory does not unless it enters long-term memory via long-term memory consolidation.
• Long-term memory: changes in structure or function of neurons, increases synaptic transmission.

Blood-Brain Barrier

• Tight junctions between endothelial cells of brain capillaries, instead of the usual permeability
• Includes the least permeable capillaries of the body
• Highly selective transport mechanisms excluding many potentially harmful substances, while allowing nutrients, O2, and CO2.
• Not a barrier against uncharged, lipid-soluble molecules; allows alcohol, nicotine, and some drugs including anesthetics.

References

• List of all cited resources.

Test your knowledge of brain anatomy and functions in this neuroscience quiz. Explore questions that cover the divisions of the brain, the role of different lobes, and the functions of the cerebellum. Perfect for students of psychology and biology!