Brain anatomy notes

MAJOR DIVISIONS OF THE BRAIN
A. FOREBRAIN
 Also known as the PROSENCEPHALON
 The forebrain is split into 2 divisions, namely the telencephalon and diencephalon
 Highest form of mental activity is found in the prefrontal lobe
CEREBRUM
 Largest part of the brain
 LONGITUDINAL FISSURE: divides cerebrum into left and right hemispheres
 CORPUS CALLOSUM: connection between the left and right hemispheres

HEMISPHERES
 Most conspicuous features on the surface of each hemisphere:
o GYRI: numerous folds which greatly increase the surface area of the cortex
o SULCI: intervening grooves
 Left hemisphere – controls right side of the body
o Math, analytic, and speech
 Wernicke’s area: parietal lobe; comprehension/where words are heard and processed
 Bronca’s area: frontal lobe; speech/where words are formulated
 Right hemisphere – controls left side of body
o Music, art, and abstract ideas

TELENCEPHALON
 Contains the left and right cerebral hemisphere
 A major component of the telencephalon is the cerebral cortex, which is further divided into four lobes
a. Frontal – voluntary motor functions, motivation, aggression, mood, and olfactory perception
b. Parietal – principal center for receiving and consciously perceiving most sensory information (touch, pain,
temperature, and balance)
 CENTRAL SULCUS: or FISSURE OF ROLANDO; separates the frontal and parietal lobes
c. Occipital –visual input; not distinctly separate from other lobes
d. Temporal – olfactory and auditory sensations, memory
 “Psychic cortex”: anterior and inferior portions of the temporal lobe that are associated with
functions such as abstract thought and judgement
 LATERAL FISSURE: separates the temporal lobes from the rest of the cerebrum
o LATERAL SULCUS: or SYLVIAN FISSURE; separates the frontal and parietal lobes
superiorly from the temporal lobe inferiorly
 INSULA/FIFTH LOBE: found deep within the lateral fissure; for visceral sensation

DIENCEPHALON
 The part of the brain between the brainstem and the cerebrum, therefore this is also known as the
INTERBRAIN
 Contains the THALAMUS, HYPOTHALAMUS, and EPITHALAMUS

a. Thalamus
- Largest part of the diencephalon
- Consists of a cluster of nuclei and is shaped like a yo-yo
- INTERTHALAMIC ADHESION: is found in the center of the “yo-yo” and connects these 2 lateral
parts
- Influences mood and registers and unlocalized, uncomfortable perception of pain

PATHWAY OF THE PROCESSES OF THE THALAMUS
1. Sensory input ascends through the spinal cord and brainstem and projects to the thalamus
2. Ascending neurons will then synapse with thalamic neurons
3. Thalamic neurons will send their axons to the cerebral cortex
4. Cerebral cortex will then process the sensory input


b. Hypothalamus
- Most inferior part of the diencephalon
- Contains several small nuclei – maintains homeostasis

, - Involved in the control of body temperature, hunger, thirst, and the secretion of hormones from the
pituitary gland
- Sensations (sexual pleasure, rage, fear, relaxation after a meal) and emotional responses are
related to hypothalamic functions
- INFUNDIBULUM: a funnel-shaped stalk that extends from the floor of the hypothalamus to the
pituitary gland
- MAMILLARY BODIES: form externally visible swellings on the posterior portion of the
hypothalamus and are involved in emotional responses to odors and in memory

c. Epithalamus
- Small area superior and posterior to the thalamus
- Consists of a few small nuclei
- Involved in the emotion and visceral response to odor, and the pineal gland
- PINEAL GLAND: endocrine gland that may influence the onset of puberty and may play a role in
controlling some long-term cycles that are influenced by the light-dark cycle

B. MIDBRAIN
 Also known as the MESENCEPHALON
 Smallest region of the brainstem
 Contains involved in coordinating eye movements and controlling pupil diameter and lens shape
 The rest of the midbrain consists of ascending tracts from the spinal cord to the cerebrum and descending tracts
from the cerebrum to the spinal cord or cerebellum
 Is divided into anterior and posterior parts

CEREBRAL PEDUNCLES
 Anterior part

CORPORA QUADRIGEMINA
 also known as COLLICULI – four mounds (“quadri-” = four)
a. 2 SUPERIOR COLLICULI: vision
b. 2 INFERIOR COLLICULI: auditory

 SUBSTANTIA NIGRA: a black nuclear mass which is part of the basal nuclei and is involved in regulating
general body movements

C. HINDBRAIN
 Also known as the RHOMBENCEPHALON
 Contains the cerebellum, pons, and medulla oblongata
 Assists in the regulation of autonomic functions, maintaining balance and equilibrium, movement coordination,
and the relay of sensory information
CEREBELLUM
 “little brain”
 Second largest part of the brain
 Responsible for movement and balance
 CEREBELLAR PEDUNCLES: large connections that attach cerebellum to the brainstem; provides routes
of communication between cerebellum and other parts of the CNS
o The gyri of the cerebellum is much smaller compared that of the cerebrum

PONS
 Immediately superior to the medulla oblongata
 Contains ascending and descending nerve tracts as well as several nuclei
 Serves as a functional bridge between the cerebrum and cerebellum (resembles an arched footbridge)
 Controls the intensity of breathing
a. APNEUSTIC RESPIRATION – inspiration
b. PNEUMOTAXIC RESPIRATION – expiration
 Swallowing, balancing, chewing, and salivation
MEDULLA OBLONGATA
 Most inferior portion of the brainstem; continuous with the spinal cord
 Most posterior part of the hindbrain
 Extends from the foramen magnum to the pons