The Human Brain: Structure, Function, and Clinical Significance
The Hemispheres of the Cerebrum
Left and Right Hemispheres
The cerebrum is divided into two hemispheres, the left and right hemispheres.
Neural Cortex
The gray matter on the surface of the cerebrum is called the neural cortex.
Functions of the Cerebrum
True: Conscious thoughts, sensation, intellect, intelligence, rationalization, and complex movement all originate in the cerebrum.
True: The highest level of information processing occurs in the cerebrum.
True: The cerebrum controls higher mental functions.
Size and Weight of the Brain
Cerebrum: The largest part of the brain.
True: There is no correlation between brain size and intelligence.
Larger: Male brains are typically larger compared to females.
3 pounds: The average weight of the human brain is about 3 pounds.
97%: The human brain contains almost 97% of the body’s neural tissue.
Primary Vesicles
Prosencephalon, Mesencephalon, Rhombencephalon: Three primary vesicles of the developing brain.
Fissures and Sulci
Longitudinal Fissure: Separates the right and left cerebral hemispheres.
Deep Grooves: Fissures are deep grooves.
Deep: The longitudinal fissure is a deep groove.
Deep: Sulci are deep grooves.
True: Sulci separate the frontal and parietal lobes from the temporal lobe, and the parietal lobe from the occipital lobe.
Lobes of the Brain
Parietal Lobe: The cerebral area posterior to the central sulcus.
Insula: The region of the cerebral cortex that is medial and deep to the temporal lobe.
True: The two hemispheres have different functions, but their structures are alike.
Sensory and Motor Pathways
True: Each cerebral hemisphere receives sensory information from and sends motor commands to the opposite side of the body.
Fiber Tracts in the Cerebrum
Gray matter: In the cerebrum, myelinated axons originate from the gray matter.
True: Association fibers connect structures within a single cerebral hemisphere.
True: Commissural fibers connect structures between the hemispheres.
Commissural fibers, Association fibers, Projection fibers: Myelinated axons in the cerebrum form tracts of fibers classified into three groups.
True: Projection fibers connect the cerebral cortex to the diencephalon, brainstem, cerebellum, and spinal cord.
Surface Area of the Brain
True: Folds in the surface of the brain increase surface area.
Lobes and Their Location
Lateral Sulcus: Separates the frontal lobe from the temporal lobe.
Frontal, Parietal, Occipital, Temporal: The four lobes of the cerebrum.
Lateral Sulcus: The insula is located deep within the lateral sulcus.
4: Grooves separate the cerebrum into four lobes.
Cerebrum: The lobes are located in the cerebrum.
Internal Capsule and Basal Nuclei
Projection: The internal capsule is a collection of projection fibers.
Neural: The corpus callosum is a collection of neural fibers.
True: In the cerebrum, the gray matter is organized into the neural cortex and nuclei.
False: Gray matter in the periphery of the cerebrum forms the cerebral cortex. Gray matter inside the cerebrum forms the nuclei.
True: Nuclei are clusters of cell bodies. The basal nuclei are involved in subconscious activities. The basal nuclei are involved in the coordination of learned movement patterns.
True: Basal nuclei are involved in the subconscious control of skeletal muscle tone.
Components of the Basal Nuclei
Caudate nucleus and Lentiform nucleus: The basal nuclei include the caudate nucleus and lentiform nucleus.
Globus pallidus and Putamen: The lentiform nucleus consists of the globus pallidus and putamen.
Functional Areas of the Cerebral Cortex
Frontal Lobe: Location of the primary motor area, responsible for voluntary movement.
Parietal Lobe, Postcentral Gyrus: Location of the somatosensory association area, responsible for processing sensory information from the body.
Parietal Lobe, Postcentral Gyrus: Location of the primary sensory area, responsible for receiving sensory input from the body, including touch, temperature, and pain. Skeletal muscles are controlled by the motor cortex, not the sensory areas.
Sensory Receptors
Retina: Location of sight receptors.
True: Cortical regions that interpret sensory information or coordinate motor responses are called association areas.
True: Visual information comes from sight receptors in the retina.
Cochlea: Location of sound receptors, responsible for auditory information.
Temporal Lobe: The olfactory cortex, responsible for processing smell, is located in the temporal lobe.
Sensory Cortices
Temporal Lobe: The auditory cortex and olfactory cortex are located in the temporal lobe.
Insula: The gustatory cortex, responsible for taste, is located in the insula.
Occipital Lobe: The visual cortex is located in the occipital lobe.
Occipital Lobe: Damage to the occipital lobe can cause loss of vision.
Prefrontal Cortex and Broca’s Area
Frontal Lobe: The prefrontal cortex is located in the frontal lobe.
Complex behaviors: The prefrontal cortex is involved in complex behaviors, such as planning, decision-making, and personality.
Frontal Lobe: Broca’s area is located in the frontal lobe.
Speech production, language processing: Broca’s area is involved in speech production and language processing.
Cerebellum
Cerebellum: Oversees the postural muscles of the body and makes rapid adjustments to maintain balance and equilibrium.
Cerebellar Cortex: The neural cortex that covers the cerebellum is called the cerebellar cortex.
True: In the cerebellum, gray matter is organized into the cerebellar cortex and cerebellar nuclei. The cerebellum is an autonomic processing center.
True: The cerebellum adjusts postural muscles. The cerebellum fine-tunes conscious and subconscious movements.
Neural Cortex
Cerebrum and Cerebellum: A neural cortex is found on the surface of both the cerebrum and cerebellum.
Parts of the Cerebellum
Vestibulocerebellum, Spinocerebellum, Cerebrocerebellum: Three parts of the cerebellum.
True: Cerebellar hemispheres are separated by the vermis.
Ataxia
Loss of full bodily movements: Ataxia is the loss of full bodily movements.
True: The cerebellum can be permanently damaged by stroke or temporarily affected by drugs or alcohol.
Ataxia: Disturbance in motor control resulting from cerebellar damage.
Corpora Quadrigemina
Two Superior and Two Inferior Colliculi: The corpora quadrigemina consist of two superior and two inferior colliculi.
Pons and Medulla Oblongata
Directly superior to the medulla and anterior to the cerebellum: Location of the pons.
Brainstem, anterior to the cerebellum: Location of the medulla oblongata.
Autonomic Nervous System
Receive sympathetic innervation via sympathetic preganglionic fibers: Collateral ganglia receive sympathetic innervation.
Abdominopelvic: Collateral ganglia contain neurons that innervate tissues and organs in the abdominopelvic cavity.
Organs Innervated by Ganglia
Stomach, Liver, Gallbladder, Pancreas, Spleen: Organs innervated by the celiac ganglia.
Small Intestine and proximal part of the Large Intestine: Organs innervated by the superior mesenteric ganglia.
Large Intestine, Kidney, Urinary Bladder, Sex organs: Organs innervated by the inferior mesenteric ganglia.
Adrenal Medulla
Epinephrine and Norepinephrine: Neurotransmitters released by the adrenal medulla.
Parasympathetic Nervous System
Parasympathetic: The parasympathetic division of the autonomic nervous system functions during “rest and digest.”
Vagus Nerves: Almost 75% of all parasympathetic outflow travels along the vagus nerves.
Neurotransmitters
Acetylcholine (ACh): Neurons that release acetylcholine are called cholinergic neurons.
Ventricles of the Brain
Lateral Ventricles, Third Ventricle, Fourth Ventricle: Cavities of the cerebral hemispheres and brainstem.
Cranial Meninges
Dura mater, Arachnoid mater, Pia mater: Three cranial meninges.
Cerebrospinal Fluid Flow
Mesencephalic Aqueduct (or Cerebral Aqueduct): Links the third and fourth ventricles.
Interventricular Foramina: Lateral ventricles communicate with the third ventricle via the interventricular foramina.
Septum Pellucidum: The wall that separates the lateral ventricles.
Cushion the brain within the skull and serve as a shock absorber for the central nervous system: Function of cerebrospinal fluid (CSF).
Dura Mater
Outermost layer, connective tissue, cranial cavity: Layers of the dura mater.
Folded inner layer of the dura mater: Location of the dural sinuses.
Falx Cerebri: The dural fold that projects into the longitudinal fissure between the cerebral hemispheres.
Mesencephalic Aqueduct
Aqueduct of Sylvius, Cerebral Aqueduct: Other names for the mesencephalic aqueduct.
Dural Folds
Falx Cerebri, Tentorium Cerebelli: Two main dural folds.
Choroid Plexus
Ependymal cells: Specialized ependymal cells form the secretory component of the choroid plexus.
Secrete CSF into ventricles, remove waste products from CSF, adjust the composition of CSF: Functions of the choroid plexus.
Cerebrospinal Fluid Absorption
Subarachnoid Space: Cerebrospinal fluid enters the blood circulation at the arachnoid granulations in the subarachnoid space.
Venous Circulation: Absorption at the arachnoid granulations returns CSF to the venous circulation.
Blood-Brain Barrier
Isolates CNS neural tissue from the general circulation: Function of the blood-brain barrier.
Is a dynamic and functional neurovascular unit comprised of endothelial cells, astrocytes, and pericytes: Characteristics of the blood-brain barrier.
Hydrocephalus
A condition in which fluid accumulates in the brain: Definition of hydrocephalus.
Cranial Nerves
Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, Hypoglossal: The 12 cranial nerves.
Sensory, Motor, or Mixed: Cranial nerves can be sensory, motor, or mixed.
12: There are 12 pairs of cranial nerves.
Smell: Damage to the olfactory nerve (cranial nerve I) would impair the sense of smell.
Bell’s Palsy
Paralysis of the nerve that supplies the facial muscles on one side of the face: Definition of Bell’s palsy.
Bell’s Palsy: A condition resulting from inflammation of the facial nerve (cranial nerve VII).
Eye Muscles
Oculomotor, Trochlear, Abducens: Cranial nerves that innervate the eye muscles.
Vestibulocochlear Nerve
Hearing and Equilibrium: Sensations carried by the vestibulocochlear nerve (cranial nerve VIII).
Electroencephalogram
is a printed record of the Brains electrical activity