Neuroscience Chapter Quiz

Nervous System (Part 2)

• The nervous system is divided into central nervous system (CNS) and peripheral nervous system (PNS)
• The CNS includes the brain and spinal cord.
• The brain lies within the cranial cavity.
• The brain is one of the largest organs of the body.
• The brain is connected to the spinal cord at the foramen magnum.
• The brain is composed of 4 major parts:
  • Cerebrum
  • Diencephalon
  • Brain Stem
    • Midbrain
    • Pons
    • Medulla oblongata
  • Cerebellum

Learning Objectives

• Describe the structures of the meninges
• Describe the flow of cerebrospinal fluid (CSF) in the brain and functions of the CSF
• Name the lobes and principal sulci of the brain
• State the functions of the cerebrum
• Describe the position and functions of the thalamus and hypothalamus
• Describe the position and functions of the midbrain, pons, medulla oblongata, and reticular activating system
• Describe the structure and functions of the cerebellum

Protection of the Brain

• The brain is protected by the cranium and cranial meninges
• The blood-brain barrier (BBB) protects brain cells from harmful substances and pathogens
• Cerebrospinal fluid (CSF) further protects the brain from chemical and physical injury

Meninges

• Three connective tissue layers that enclose the brain:
  • Dura mater (outermost)
  • Arachnoid mater (middle)
  • Pia mater (innermost)

Cerebrospinal Fluid (CSF)

• Circulates in the subarachnoid space, and cushions the brain
• CSF is a clear, colorless liquid that carries oxygen, glucose, and chemicals from the blood to neurons and neuroglia, and removes wastes and toxic substances produced by brain and spinal cord cells.
• CSF is produced in the choroid plexuses in cerebral ventricles.
• Ependymal cells cover the choroid plexus capillaries and form the CSF from blood plasma by filtration and secretion.
• CSF pressure is 120-180 mmH₂O
• The cranial cavity contains 80-150 ml of CSF

Ventricles of the Brain

• There are four ventricles: two lateral ventricles, one third ventricle, and one fourth ventricle
• CSF flows from the fourth ventricle to the central canal of the spinal cord and the central canal within the subarachnoid space, then it reabsorbs through arachnoid villi into the superior sagittal sinus.

Functions of CSF

• Protects the CNS by acting as a shock absorber
• Removes waste products of brain metabolism
• Regulates the extracellular environment of CNS neurons
• Transports hormones and hormone-releasing factors

Cranial Meninges

• Layers of connective tissue that envelop the brain -Skin of scalp -Periosteum -Bone of skull -Periosteal layer -Dura mater -Meningeal layer -Subdural space (potential space) -Arachnoid -Subarachnoid space -Pia mater -Cerebral cortex -White matter

Blood Supply & Blood-Brain Barrier (BBB)

• The brain requires 20% of the body's oxygen supply.
• A 4-minute lack of oxygen leads to permanent damage
• The brain requires a constant supply of glucose.
• The brain is protected by the blood-brain barrier (BBB).
• The BBB allows passage of lipid-soluble materials (e.g., oxygen, carbon dioxide, alcohol, anesthetics), but controls the entry of most harmful materials.
• Created by tight capillaries and astrocytes

Brain: Major Parts

• Forebrain
  • Cerebrum
• Hindbrain
  • Cerebellum
• Brain Stem
  • Midbrain
  • Pons
  • Medulla oblongata
• Diencephalon
  • Thalamus
  • Hypothalamus

Cerebrum

• Largest portion of the brain
• Divided into lobes (frontal, parietal, occipital, temporal).
• Separated by fissures (longitudinal fissure, lateral fissure, parieto-occipital sulcus).
• Contains sulci (shallow grooves) and gyri (folds).
• Provides for reading, writing, speaking, memorising, planning and creating.
• Major gyri include: Precentral gyrus and Postcentral gyrus
• The insula is the fifth lobe nestled within the lateral cerebral sulcus deep to the parietal, frontal, and temporal lobes.

Functional Areas of Cerebral Cortex

• Sensory areas: receive sensory input for perception of conscious awareness/sensation. -Primary somatosensory area (touch, proprioception, pain, temperature) in the postcentral gyrus of the parietal lobe. -Visual area in the occipital lobe (visual perception) -Auditory area in the temporal lobe (auditory perception) -Gustatory area near postcentral gyrus (taste perception) -Olfactory area on medial aspect of temporal lobe (smell perception)
• Motor areas: initiate movements -Primary motor area in the precentral gyrus -Boca's speech area in frontal lobe
• Association areas: complex integration (memory, emotion, reasoning, judgment, personality traits, intelligence). Examples are:
  • Somatosensory association area; Wernicke's area

III. Motor Areas

• Located anterior to the central sulcus
• Primary motor area: precentral gyrus; controls voluntary contractions of specific muscles.
• Broca's speech area interacts with premotor area & primary motor areas to regulate breathing and speech muscles.
• Mostly localized on the left hemisphere in 97% of people.

III. Association Areas

• Consist of large areas of the occipital, parietal, temporal, and frontal lobes.
• Adjacent to sensory and motor areas, and connected via association tracts.
• Integrate and interpret information, including -Somatosensory association area -Wernicke's area

Hemispheric Lateralization

• The two hemispheres are symmetrical with slight anatomical variations.
• Functionally different, with each specialized in certain tasks.
• Left hemisphere is important for spoken and written language, numerical and scientific skills, and reasoning
• Right hemisphere is involved in musical and artistic awareness, spatial and pattern perception, faces recognition, and emotional content of languages..

Memory

• The brain acquires and stores, and retrieves information.
• Brain areas involved in memory: association areas of frontal, parietal, occipital and temporal lobes, parts of the limbic system, and the diencephalon.
• Motor skills involve cerebellum and basal ganglia

Brain Stem

• The midbrain connects the pons to the diencephalon through large tracts: cerebral peduncles.
• The midbrain contains: Substantia nigra (Parkinson's disease), red nuclei (coordinate movements), cranial nerves III & IV (control eye movements), superior and inferior colliculi.
• The pons acts as a bridge, connecting medulla to the midbrain and above. Contains ascending and descending tracts, connecting left and right sides of the cerebellum; contains nuclei for motor control (relay from cerebrum to cerebellum) and breathing control.
• The medulla oblongata is the most inferior portion of the brainstem, containing sensory (ascending) and motor (descending) tracts connecting the spinal cord and other brain parts. It also houses vital nuclei: the cardiovascular center (regulates heart rate and blood pressure), the medullary rhythmicity area (adjusts respiratory rhythm), and other nuclei controlling sensory and reflexes (swallowing, vomiting, coughing, hiccupping, and sneezing). Cranial nerves VIII-XII attach here.

Reticular Formation

• Small clusters of net-like gray and white matter
• Contains ascending (sensory) and descending (motor) tracts.
• Ascending part = reticular activating system (RAS): carries sensory pathways to cerebral cortex; helps to maintain consciousness (wakefulness); Inactivation of RAS → induce sleep.
• Descending function helps regulate muscle tone.

Diencephalon

• Located between the brainstem and cerebrum
• Includes:
  • Thalamus (major relay station for sensory impulses to cerebral cortex; contributes to motor functions; relays nerve impulses between areas of the cerebrum; maintains consciousness)
  • Hypothalamus (lies inferior to thalamus; controls many body activities including homeostasis, works with ANS, regulates body temperature, hormone production, eating, drinking, fluid levels, and circadian rhythms)
  • Subthalamus (contains nerve tracts and nuclei)
  • Epithalamus (contains nuclei responding to olfactory stimulation and contains the pineal gland)

Cerebellum

• Divided into functional sections that are vital for balance and motor control.
  • Flocculonodular lobe
  • Vermis
  • Lateral lobes
• Cerebellar peduncles attach to the brain stem.
• The cerebellum's structure includes two cerebellar hemispheres, a cortex of gray matter, and a tree-like appearance in sagittal sections of white matter and gray nuclei.
• Function: receives sensory input from muscles, joints, tendons, and inner ears to compare actual movements with intended ones, helps produce smooth and coordinated movements, helps perform skilled motor activities, and regulates posture and balance.

Clinical Application: Aging

• Rapid brain growth during the first few years of life due to increased neuron size and neuroglia proliferation, dendritic branch development, and synaptic contact increases.
• From early adulthood, and older age, brain mass declines and synaptic contact decreases, impacting brain function, information processing, and voluntary motor movements decrease.

Test your knowledge on the major parts of the brain and their functions in this Neuroscience chapter quiz. Explore topics such as the meninges, cerebrospinal fluid, and various brain areas involved in sensory and motor functions. Challenge yourself with questions designed to assess your understanding of brain anatomy and physiology.