Anatomy and Physiology: Brain
The cranium
The brain is protected by a bony covering called the cranium (which, along with the bones of
the face, make up the skull). Inside the cranium, the brain is surrounded by the meninges. The
meninges is made up of 3 layers of tissue:
Pia mater the layer closest to the surface of the brain
Arachnoid membrane the middle layer of tissue
Dura mater the outer-most layer
The cerebrum the front of the brain
The largest part of the brain located in the front is called the cerebrum. The cerebrum is
responsible for:
Movement
Body temperature
Touch
Vision
Hearing
Judgment
Reasoning
Problem solving
Emotions
Learning
The cerebrum has 2 parts: the right cerebral hemisphere and the left cerebral hemisphere.
They are connected at the bottom and have a deep groove running between them. In general,
the right cerebral hemisphere controls the left side of the body, and the left cerebral
hemisphere controls the right. The right side is involved with creativity and artistic abilities.
The left side is important for logic and rational thinking.
The hemispheres of the cerebrum are divided into lobes, or broad regions of the brain. Each
lobe is responsible for a variety of bodily functions:
Frontal lobes are involved with personality, speech, and motor development
Temporal lobes are responsible for memory, language and speech functions
Parietal lobes are involved with sensation
Occipital lobes are the primary vision centers
The surface of the cerebrum appears wrinkled and is made up of deep grooves (called sulci)
and bumps or folds (called gyri). The outer part of the cerebrum is called gray matter and
contains nerve cells. The inner part is called white matter and contains connections of nerves.
The brainstem the middle of the brain
The brainstem is located in front of the cerebellum. The brainstem is like the hard-drive of a
computer. It is the main control panel for the body that passes messages back and forth
between the brain and other parts of the body. The cerebrum, the cerebellum, and the spinal
cord are all connected to the brainstem. The brainstem has three main parts, the midbrain, the
pons, and the medulla oblongata.
The brainstem controls vital functions of the body, including:
Breathing
Consciousness
Cardiac function
Involuntary muscle movements
Swallowing
Movement of the eyes and mouth
Relaying sensory messages (pain, heat, noise, etc.)
Hunger
The cerebellum the back of the brain
Behind the cerebrum at the back of the head is the cerebellum. In Latin, cerebellum means
little brain. However, the cerebellum contains more nerve cells than both hemispheres
combined. The cerebellum is primarily a movement control center, responsible for:
Voluntary muscle movements
Fine motor skills
Maintaining balance, posture, and equilibrium
Unlike the cerebrum, the left cerebellum controls the left side of the body, and the right
cerebellum controls the right side of the body.
Other important parts of the brain
Ventricular system
The brain is not a solid organ. There are fluid-filled cavities within the brain called ventricles.
The ventricles are important in providing nourishment to the brain. The ventricular system
produces and processes cerebrospinal fluid a clear, watery substance that flows around the
brain and helps cushion and protect it.
Cranial nerves
The brain also contains 12 pairs of cranial nerves each responsible for specific functions in the
body:
Olfactory nerve smell
Optic nerve vision
Oculomotor eye movements, eyelid opening
Trochlear eye movements
Trigeminal facial sensations, chewing
Abducens eye movements
Facial taste, facial expressions
Vestibulocochlear hearing, balance
Glossopharyngeal taste, swallowing
Vagus swallowing, taste
Accessory neck and shoulder muscles
Hypoglossal tongue movement
Pituitary gland
The pituitary gland is located in the center of the brain and is about the size of a dime. The
pituitary gland, often referred to as the master gland, is responsible for a number of
functions including producing hormones for the thyroid and adrenal glands, as well as the
hormones responsible for normal growth and sexual maturation.
