Exam 4 Review:  Chapter 12:  Gross Anatomy of the Brain

 

cerebrum - The two cerebral hemispheres which form the bulk of the brain have a surface consisting of folds = gyri and grooves = sulci and fissures; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter; each hemisphere is divided into five lobes, the frontal lobe, the temporal lobe, the parietal lobe, the occipital lobe and the insula; the cerebrum is the seat of consciousness where all forms of sensory information are received and interpreted and where voluntary commands are issued to skeletal muscles; it is also the location for emotional processing and higher thought processes including learning, problem solving, memory, etc.

 

cerebral cortex - The gray matter on the surface of the cerbrum which is from 2 - 4 mm thick and is subdivided into six cellular layers; the cerebral cortex is the seat of consciousness where all forms of sensory information are received and interpreted and where voluntary commands are issued to skeletal muscles; it is also a location for emotional processing and higher thought processes including learning, problem solving, memory, etc.

 

 

gyrus / gyri = convolution(s) - The folds of gray matter which form the cerebral cortex; having the gray matter distributed in folds and grooves increases the surface area of the cortex to facilitate diffusion of nutrients, respiratory gases, and wastes between the nervous tissue and the adjacent cerebrospinal fluid and the blood stream.

 

fissure - The larger deeper grooves on the surface of the cerebral hemispheres which tend to be partial dividers of the hemisphere into its specific lobes; these grooves also increase the surface area of the brain surface which makes room for more gray matter and also provides access to the blood supply in the nearby pia mater and subarachnoid space.

 

sulcus / sulci - The smaller shallower grooves on the surface of the cerebral hemispheres which divide the surface of each hemisphere into its specific convolutions = gyri; having the gray matter distributed in folds and grooves increases the surface area of the cortex to facilitate diffusion of nutrients, respiratory gases, and wastes between the nervous tissue and the adjacent cerebrospinal fluid and the blood stream.

 

longitudinal fissure - The deep groove which separates the left and right hemispheres of the cerebral cortex and it is occupied by the superior and inferior venous sagittal sinuses which are housed within an extension of the dura mater.

 

cerebral hemispheres - The right and left halves of the cerebrum which are subdivided into 5 lobes:  frontal, parietal, temporal, occipital, and insula; the two hemispheres are anatomically and functionally asymmetrical with the contralateral hemisphere having slightly enlarged parietal and occipital lobes, the differences is related largely to which hand is dominant (handedness); their tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.

 

lobe - The anatomic subdivision of a cerebral hemisphere, with the boundary usually marked by a slightly deeper sulcus or an even deeper fissure; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.

 

 

 

frontal lobe - The anterior lobe of the cerebral hemisphere named for the overlying frontal bone, this lobe receives and interprets olfactory sensation, initiates voluntary commands to skeletal muscles; it is also a main location for personality traits and higher thought processes including learning, problem solving, memory, etc.; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.   [National Public Radio has produced a short history of the frontal lobotomy procedure.  If you're interested, click here.]  [Recent research (2012) at UCLA reveals gene activity differences that give insight into how the human cortex evolved increased sophistication of information compared to our nearest relative, the chimpanzee.  If you're interested, click here.]

 

temporal lobe - The inferior lateral lobe of the cerebral hemisphere named for the overlying temporal bone, this lobe receives and interprets auditory sensation and equilibrium sensation; it is also a main location for coordination of auditory and visual aspects of language; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.

 

parietal lobe - The superior lateral lobe of the cerebral hemisphere named for the overlying parietal bone, this lobe receives and interprets cutaneous and somatic sensations and taste; it is also a main location for general association areas; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.

 

occipital lobe - The posterior lobe of the cerebral hemisphere named for the overlying occipital bone, this lobe receives and interprets visual sensation; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.

 

insula - The lobe of the cerebral hemisphere which is located deep within the lateral cerebral fissure under the parietal, frontal, and temporal lobes;  it is a location for visceral and autonomic function, including taste; its tissues consist of surface gray matter and some embedded nuclei of gray matter and various expanses of white matter.

 


olfactory bulbs - The enlarged ventral projections of the frontal lobes, adjacent to the cribiform plate of the ethmoid bone, where the olfactory nerves begin.

 

 


 

 

diencephalon - The connection between the cortex and the brain stem which consists of the thalamus, hypothalamus, epithalamus and pineal gland, and third ventricle; it contains a variety of ascending and descending white fiber tracts as well as gray matter organized into nuclei which function in regulating internal homeostasis, in memory processing and in emotional response.

 

 


 

 

brain stem - The distal portion of the the brain, extending from the diencephalon to the spinal cord, and connecting to the cerebellum by several pairs of cerebellar peduncles, the brain stem consists of the reticular formation, midbrain, pons, and medulla oblongata; it contains major ascending and descending white fiber tracts, is the origin for several pairs of cranial nerves, and contains gray matter nuclei involved in regulating internal homeostasis, e.g., state of arousal (asleep versus awake), respiratory rate, heart rate, vasomotor tone, and coordination of swallowing, vomiting, coughing, sneezing, and hiccupping.

 

midbrain - The upper portion of the brain stem, connecting the diencephalon to the pons, which contains the cerebral aquaduct which connects the 3rd and 4th ventricles; it contains major ascending and descending white fiber tracts, and contains gray matter nuclei involved in the reflex movements of the head and trunk in response to visual, auditory and other stimuli.

 

pons - The "bridge" between the midbrain and the medulla oblongata consists of gray matter nuclei, including the pneumotaxic area and apneustic area which help control breathing rate, and white fiber tracts.

 

medulla oblongata - The lower portion of the brain stem, connecting the pons to the spinal cord and the location of the pyramids; it contains major ascending and descending white fiber tracts and the location where most such tracts, sensory and motor,  cross from right to left within the CNS; and it contains gray matter nuclei involved in the regulation of heart rate, vasomotor tone, respiratory rate, and coordination of swallowing, vomiting, coughing, sneezing, and hiccupping.

 

pyramids - The visible features of the ventral surface of the medulla oblongata which contain the largest descending white fiber motor tracts to skeletal muscles and the site where these fibers cross over from right to left or vice versa (crossing to the contralateral side is called called decussation in the brain stem).

 

decussation of the pyramids - The routing pathway within medulla oblongata where the largest descending white fiber motor tracts to skeletal muscles cross over from right to left sides of the body and vice versa.

 

 


 

 

cerebellum - The mass of nervous tissue inferior to the occipital lobes (separated from them by the transverse fissure) and posterior to the medulla and pons which consists of two hemispheres connected by a central vermis; cerebellar gray matter is found on the surface and within the white matter ("arbor vitae") and this gray matter is involved in (1) the subconscious movement and coordination of skeletal muscles for skilled movements, for posture and balance, (2) the sense of equilibrium, and (3) contributes to emotional states.

 


 

cranial nerves - The series of twelve pairs of nerves which originate in various portions of the brain and exit the skull through specific foramina to serve the tissues and structures of the head and neck and certain thoracic and abdominal viscera.  Click here for a PowerPoint review of the twelve cranial nerves.

 

List

1. The four main parts, the largest subdivisions, of the brain as described in your textbook and describe the basic functions of each part.

cerebrum - The cerebrum, the two cerebral hemispheres, is the seat of consciousness where all forms of sensory information are received and interpreted and where voluntary commands are issued to skeletal muscles; it is also the location for emotional processing and higher thought processes including learning, problem solving, memory, etc.
diencephalon - The connection between the cortex and the brain stem  (contains the thalamus, hypothalamus, epithalamus, and pineal gland); it contains a variety of ascending and descending white fiber tracts as well as gray matter organized into nuclei which function in regulating internal homeostasis, in memory processing and in emotional response.

brain stem - The brain stem consists of the reticular formation, midbrain, pons, and medulla oblongata; it contains major ascending and descending white fiber tracts, is the origin for several pairs of cranial nerves, and contains gray matter nuclei involved in regulating internal homeostasis, e.g., state of arousal (asleep versus awake), respiratory rate, heart rate, vasomotor tone, and coordination of swallowing, vomiting, coughing, sneezing, and hiccupping.

cerebellum - The two hemispheres of this structure are involved in (1) the subconscious movement and coordination of skeletal muscles for skilled movements, for posture and balance, (2) the sense of equilibrium, and (3) contributions to emotional states.

2a. Three parts of the:  (a) diencephalon and the functions of each part.
 

epithalamus - A thin mass of nervous tissue (gray and white matter) forming the roof of the third ventricle, and including the pineal gland*; its gray matter is involved in emotional and visceral responses to odors and its white fibers form a link between the limbic system and other parts of the brain.

[*Note:  the pineal gland - A small organ situated beneath the back part of the corpus callosum in the roof of the third ventricle of the brain which secretes the hormone melatonin; in the human it appears to play a role in sleep-wake cycles and may contribute to the regulation of the onset of puberty.]

thalamus - A pair of large ovoid masses of gray matter situated in the posterior part of the diencephalon on either side of the third ventricle which process sensory impulses (except olfaction) by gating out irrelevant sensory information while directing relevant information to the cerebral cortex and it is also important in motor control; it is divided into two major part: dorsal and ventral, each of which contains many nuclei.

hypothalamus - The part of the brain which lies below the thalamus, forming the major portion of the ventral region of the diencephalon and which functions to regulate bodily temperature, water balance, carbohydrate and fat metabolism among other metabolic processes, and autonomic activities and also contributes to the regulation of internal homeostasis by neurosecretory functions which control the activity of the pituitary gland.

 

2b. Three parts of the:  (b) brain stem and the functions of each part.

 

midbrain - The upper portion of the brain stem, it contains major ascending and descending white fiber tracts, and contains gray matter nuclei involved in the reflex movements of the head and trunk in response to visual, auditory and other stimuli.

pons - The "bridge" between the midbrain and the medulla oblongata consists of gray matter nuclei, including the pneumotaxic area and apneustic area which help control breathing rate, and white fiber tracts.

medulla oblongata - The lower portion of the brain stem, it contains major ascending and descending white fiber tracts and the location where most such tracts, sensory and motor,  cross from right to left within the CNS; and it contains gray matter nuclei involved in the regulation of heart rate, vasomotor tone, respiratory rate, and coordination of swallowing, vomiting, coughing, sneezing, and hiccupping.

 

3. Five lobes of the cerebral hemisphere and their locations.

 

frontal lobe anterior in the cranial cavity, deep to the frontal bone
temporal lobe lateral, inferior in the cranial cavity, deep to the temporal bone

parietal lobe

lateral, superior in the cranial cavity, deep to the parietal bone

occipital lobe

posterior in the cranial cavity, deep to the occipital bone
insula central in the cranial cavity, deep to the other cerebral lobes

 

Sketch and label

2. A frontal section of the brain illustrating hemispheres, commissures, areas of gray and white matter and types of fiber tract connections.

Note:  The definitions below are to remind you what structures are to be identified and labeled in your sketch.

 

cerebral hemispheres - The right and left halves of the cerebrum which are subdivided into 5 lobes:  frontal, parietal, temporal, occipital, and insula; the two hemispheres are anatomically and functionally asymmetrical with the contralateral hemisphere having slightly enlarged parietal and occipital lobes, the differences is related largely to which hand is dominant (handedness).

 

association fibers - The various interneuron processes (axons and dendrites) which transmit nerve impulses between the various gyri and nuclei within a single cerebral hemisphere.

 

commissural fibers - The various interneuron processes (axons and dendrites) which transmit nerve impulses from the various gyri and nuclei within a single cerebral hemisphere to corresponding locations in the opposite hemisphere; e.g., many of the fibers in the corpus callosum and anterior and posterior commissures.

 

projection fibers - The various interneuron processes (axons and dendrites) which transmit nerve impulses from the various gyri and nuclei within the cerebral hemispheres to various locations in other parts of the brain and spinal cord; e.g., the various ascending and descending tracts of white matter connecting the cerebrum to the rest of the CNS.

gray matter - nerve cell bodies, dendrites, and axon terminals or bundles of unmyelinated axons and neuroglia organized into functional groupings within the Central Nervous System; in the spinal cord, gray matter forms an H-shaped inner core, surrounded by white matter; in the brain a thin outer shell of gray matter (cortex) covers the cerebral hemispheres.  (Additional regions of gray matter are found deep in the brain where the are referred to as nuclei, or with diminishing frequency, ganglia.)

white matter - aggregations of myelinated axons spatially organized into functional tracts (white matter) within the Central Nervous System.