THE CENTRAL NERVOUS

SYSTEMForebrain, Midbrain, Hindbrain and

Spinal Cord

Shaddae PalmerNastassaja Lewis

WHAT IS THE CNS?The Central Nervous System is

essentially the brain and the spinal cord. The CNS receives sensory information from the nervous system and controls the body’s responses.

The Brain Spinal Cord

The Forebrain The Midbrain The Hindbrain

ANATOMICAL SUBDIVISIONS OF THE BRAIN

Major Division Ventricle Principal Structures

Forebrain • Lateral

• Third

(Basal ganglia, limbic system and cerebral cortex(Thalamus and Hypothalamus)

Midbrain Cerebral aqueduct TectumTegmentum

Hindbrain • Fourth • Cerebellum, Pons and Medulla Oblangata

THE BRAIN

THE FOREBRAIN (PROSENCEPHALON)

There are two major sub-divisions of the forebrain,

the diencephalon the telencephalon

The diencephalon contains the thalamus and hypothalamus which is responsible for motor control, relaying sensory information between brain regions and controlling autonomic functions.

The telencephalon is also know as the cerebrum. This is the largest part of the forebrain.

The cerebrum covered by a layer of tissue (cerebral cortex) consists of the left and right hemisphere. They are connected by a bond of fibers known as the Corpus Callosum (facilitates communication between the two hemispheres).

Each hemisphere of the cerebrum is also composed of four lobes (frontal, parietal,

occipital and temporal).

The frontal lobe- responsible for body movement and executive functions.

The Parietal lobe- specialized for touch and perception also sensitive to pressure and pain

The temporal lobe- the prime site of hearing, understanding language and storing memories

Occipital Lobe- Specialized for vision at the back of the cerebral cortex

FUNCTIONS OF THE CEREBRUM Determining personality and intelligence Perceiving Thinking Producing and Understanding Language Interpretation of Sensory Impulses Motor Function Planning and Organization Touch and Senation

THE MIDBRAIN (MESENCEPHALON) It is located between the forebrain and

the hindbrain and is responsible for regulating sensory processes. It consists of the tectum and tegmentum.

The tectum is the dorsal (roof) part of the midbrain; includes the superior and inferior colliculi.

superior colliculi (ka lik yew lee) Protrusions on top of the midbrain; part of the visual system

inferior colliculi Protrusions on top of the midbrain; part of the auditory system.

The midbrain is also involved in the control of body movement. Dopamine producing neurons can also be found in the midbrain. Damage to this area can lead to Parkinson's disease.

THE HINDBRAIN This surrounds the fourth ventricle and

consists of two major divisions; the metencephalon and the myelencephalon.

The METENCEPHALON includes the pons and the cerebellum.

Cerebellum- also called the “little brain”, it has two hemispheres covered by the cerebellar cortex and has a set of deep cerebellar nuclei. These nuclei receive projections from the cerebellar cortex and then send projections out of the cerebellum to other parts of the brain.

Each hemisphere of the cerebellum is attached to the dorsal (back)structure of the pons by bundles of axons which includes the superior, middles and inferior (cerebellar peduncles).

Damage to the cerebellum impairs our walking, standing and co-ordinated movements. Examples include a musician playing a guitar or a dancer doing balanced movements.

It receives visual, auditory, vestibular (control, balance) and somatosensory information (conscious perception of things that affect our body) . Also, information about individual muscle movements being directed towards the brain. It integrates all this information and modifies the motor outflow creating a co-ordinating and smoothing effect on the movements.

Damage to the cerebellum results in jerky, poorly co-ordinated, exaggerated movements. Extensive damage to cerebellar makes it even impossible to stand.

> Pons(means bridge)- is a large bulge

in the brain stem and lies between the mesencephalon and the medulla oblongata. The pons contain in its core, a portion of the reticular formation (region in the brain stem that is involved in multiple tasks) which includes nuclei that are important to sleep and arousal. It also contains a large nucleus that relays information from the cerebral cortex to the cerebrum.

The MYLENCEPHALON only contains one major structure which is the medulla oblongata(oblong marrow). It is the most caudal(near the tail) portion of the brain stem and its lower border is the rostral end (front end) of the spinal cord.

It contains part of the reticular formation that control vital functions such as regulation of the cardiovascualar system, respiration and skeletal muscle tonus.

THE SPINAL CORD This is a long conical structure approximately as

thick as our little finger. It principal function is to distribute motor fibers to the effective organism of the body(glands and muscles and to collect somatosensory information to be passed on to the brain.

The spinal cord also has a certain degree of autonomy (independence) from the brain and is protected by the vertebral column which is composed of twenty four individual vertebrae of the cervical(neck),thoracic(throat),lumber regions(lower back) and the fused vertebrea that make up the sacral and coccygeal portions of the column(located in the pelvic area).

The spinal cord passes through a hole in each of the vertebrea(spinal foramens). It is about two-thirds long as the vertebral column and the rest of the space is filled my a mass of spinal roots composing the cauda equina (horse’s tail).

In early embryotic development the spinal cord and the vertebral column are the same length but as development begins the vertebral column grows faster then the spinal cord.

SUMMARY The brain consist of three major

divisions the midbrain he forebrain and the hind brain.

Development begins from early in the embryonic life