The brain is the neurological center of an organism.
Distinguish between the cerebellum, cerebral cortex, and brain stem regions of the brain
The brain is protected by the thick bones of the skull, suspended in cerebrospinal fluid, and isolated from the bloodstream by the blood-brain barrier.
The brain stem consists of the midbrain, pons, and medulla.
Each of the two hemispheres is divided into four separate lobes: the frontal (control of specialized motor control, learning, planning, and speech); parietal (control of somatic sensory functions); occipital (control of vision); and temporal lobes (control of hearing and some speech).
The seahorse-shaped hippocampus is responsible for memory.
The amygdala controls mood and emotions and is the center for danger identification and self-preservation.
The cortex is divided into three functional categories: sensory, motor, and association.
The upper part of the brain, divided into the two cerebral hemispheres. In humans, it is the largest part of the brain and the seat of motor and sensory functions, as well as higher mental functions such as consciousness, thought, reason, emotion, and memory.
of the hypothalamus
interfere with several vegetative functions and some behaviors, such as sexuality, combativeness, and hunger.
The human brain is the center of the human nervous
system. It has the same general structure as the brains of other
mammals, but is larger than expected on the basis of body size when compared to other primates.
Estimates for the number of neurons (nerve cells) in the human brain range from
80 to 120 billion. Most of the expansion comes from the cerebral cortex,
especially the frontal lobes,
which are associated with executive
functions such as self-control, planning, reasoning, and abstract
Despite being protected by the thick bones of the
skull, suspended in cerebrospinal fluid, and isolated from the bloodstream by
the blood-brain barrier, the human brain is susceptible to many types of damage
and disease. This includes degenerative disorders
such as Parkinson's disease, multiple sclerosis, and Alzheimer's disease. A
number of psychiatric conditions, such as schizophrenia and depression, are
thought to be associated with brain dysfunction, although the nature of such
brain anomalies is not well understood.
The cerebral hemispheres form the
largest part of the human brain and are situated above most other brain structures. They are covered with a cortical
layer and have a convoluted
topography. The cerebral cortex is essentially a sheet of neural tissue folded
in a way that allows a large surface area to fit within the confines of the
skull. Anatomists call each cortical fold a sulcus and the smooth area between folds a gyrus. As a rule, the smaller the cerebrum,
the less convoluted the cortex. The cortex of a rat or mouse is almost
completely smooth. The cortex of a dolphin or whale, on the other hand, is more
convoluted than the cortex of a human.
The left and right hemispheres of the cerebral cortex are nearly symmetrical. The hemispheres are connected by the corpus callosum, the largest white-matter
structure in the brain. Anatomists
conventionally divide each hemisphere
into four lobes: the frontal (control of specialized motor control,
learning, planning, and speech),
parietal (control of somatic sensory functions), occipital (control of
vision), and temporal lobes
(control of hearing and some speech).
The division into lobes does not
actually arise from the structure of
the cortex itself. Instead, each section is named after the skull bone that covers it. The borders between lobes are placed beneath the sutures
that link the skull bones together. The only exception is the border between
the frontal and parietal lobes, which is shifted backward from the corresponding
suture to the central sulcus. This deep fold marks the line where the primary
somatosensory cortex (main sensory receptive
area for the sense of touch) and primary motor
cortex (one of the principal areas of the brain involved in motor function) come together. Functionally, the cortex is
commonly described as comprising three parts: sensory, motor, and association
The cerebrum is attached to a stalk-like structure called the brain stem, which consists
of the midbrain, pons, and medulla. At the rear
of the brain beneath the cerebrum and behind the brainstem is the cerebellum. This structure has a horizontally-furrowed surface with an appearance that
is distinct from all other brain areas. These same structures are present in other
mammals, although the cerebellum is not so large relative to the rest of the
brain in non-human mammals.
Found deep in the temporal lobe, the seahorse-shaped hippocampus is responsible for memory. The amygdala is a
small, almond-shaped structure deep inside the anteroinferior region of the
temporal lobe. It plays an important role
in the mediation and control of activities and feelings such as love, friendship, affection,
and mood expression. The amygdala is the center for danger identification, a fundamental part of self-preservation.
is perched on top of the brainstem near the center of the brain, with nerve
fibers projecting out to the cerebral cortex in all directions. Its functions includes relaying sensory and motor signals to the cerebral cortex and regulating consciousness, sleep, and alertness. It likely acts as a relay between a variety of subcortical areas and the cerebral
is a small part of the brain located just below the thalamus on both sides of
the third ventricle.
The hypothalamus also plays a role in emotion. Specifically, the lateral
parts seem to be involved with pleasure and rage, while the medial part is
linked to aversion, displeasure, and a tendency toward uncontrollably loud laughing. When the physical symptoms
of emotion appear, the threat they pose
returns to the limbic centers via the hypothalamus, then to the
prefrontal nuclei, increasing anxiety.