Principles of Health Science 2012

Central Nervous System

There are two main divisions of the nervous system:•The Central Nervous System•The Peripheral Nervous System

Divisions of the Nervous System

The Central Nervous System consists of the brain and spinal cord.The Brain:• Is a mass of nerve tissue• Is protected by membranes and the cranium or skull

1. Cerebrum•Largest and highest section of the brain•Outer part is arranged in folds called convolutions and separated into lobes•These lobes are named for the skull bones that surround them•Frontal•Parietal•Temporal•Occipital

Divisions of the Brain

Two Hemispheres-the right side-the left side Are

connected by the corpus callosum.

Is responsible for:•Reasoning•Thought•Memory•Speech•Sensation (parietal lobe)•Sight (occipital lobe)•Smell (temporal lobe)•Hearing (temporal lobe)•Voluntary movement (frontal lobe)

Cerebrum

Cerebrum

•Section below the back of the cerebrum•Responsible for coordination of muscles, balance and posture, and muscle tone

2.Cerebellum

• Located between the cerebrum and midbrain

3. Diencephalon

•Contains two structures: thalamus and hypothalamus•Thalamus acts as a relay center and directs sensory impulses to the cerebrum•Hypothalamus regulates and controls:•Autonomic nervous system•Temperature•Appetite•Water balance•Sleep•Constriction and dilation of blood vessels•Also involved with emotions such as anger, fear, pleasure, pain, and affection

Diencephalon

•Located below the cerebrum at the top of the brain stem•Responsible for conducting impulses between brain parts and for certain eye reflexes

4. Midbrain

•Located below the midbrain in the brain stem•Responsible for conducting messages to other parts of the brain and for certain reflex actions including:•Chewing•Tasting•Production of saliva•Assisting with respiration

5. Pons

•Lowest part of the brain stem•Connects with the spinal cord•Responsible for regulating:•Heartbeat•Respiration•Swallowing•Coughing•Blood Pressure

6. Medulla Oblongata

Divisions of the Brain

• Continues down from the medulla oblongata

• Ends at the first or second lumbar vertebra

• Surrounded and protected by the vertebrae

Responsible for many reflex actions

• Carries sensory (afferent) messages up to the brain

• Carries motor (efferent) messages from the brain to the nerves that go to muscles and glands

 

7. Spinal Cord

Cross Section of Spinal Cord

Spinal Cord

•Three membranes•Cover and protect the brain and spinal cord

8. Meninges

1. Dura mater: thick, tough outer layer2. Arachnoid membrane: middle delicate weblike layer3. Pia mater:

*Innermost layer*Closely attached to the brain and spinal cord

*Contains blood vessels that nourish the nerve tissue

Three Layers of Meninges:

Four hollow spaces located in the brain

9. Ventricles

•Connect with each other and with the space under the arachnoid membrane, the subarachnoid space• Filled with a fluid called cerebrospinal fluid• Fluid circulates continually between the ventricles and through the subarachnoid space•Serves as a shock absorber to protect the brain and spinal cord•Carries nutrients to some parts of the brain and spinal cord•Helps remove metabolic products and wastes•Produced by special structures called choroids plexuses in the ventricles of the brain•After circulating, it is absorbed into the blood vessels of the dura mater and returned to bloodstream through special structures called arachnoid villi

Ventricles