The Nervous System

Neurons• A neuron consists of two major parts:

Cell Body

The central cell body contains the neuron's nucleus, associated cytoplasm, and other organelles.

Nerve Processes

Nerve processes are "finger-like" projections from the cell body that are able to conduct and transmit signals. There are two types:

Axons - typically carry signals away from the cell body. Axons are covered with a lipid layer known as the myelin sheath , which insulates the axon.

Dendrites - typically carry signals toward the cell body.

Neurons usually have one axon (can be branched however). Axons usually terminate at a synapse through which the signal is sent to the next cell, most often through a dendrite.

Unlike axons, dendrites are usually more numerous, shorter and more branched.

Structure of the Nervous System• The nervous system is divided into the peripheral nervous system (PNS) and

the central nervous system (CNS)

The PNS consists of sensory neurons running from stimulus receptors that inform the CNS of the

stimuli motor neurons running from the CNS to the muscles and glands - called

effectors - that take action.The peripheral nervous system is subdivided into the sensory-somatic nervous

system (control movement of skeletal muscles) and the autonomic nervous system (further divided into parasympathetic & sympathetic system)

The CNS consists of the spinal cord - the brain

PERIPHERAL NERVOUS SYSTEM

CENTRAL NERVOUS SYSTEM

The Circulatory System

Transportation system by which oxygen and nutrients reach the

body's cells, and waste materials are carried away.

Parts of the Circulatory System

• Divided into three major parts:– The Heart – The Blood – The Blood Vessels

The Blood Vessels

• The cardiovascular system has three types of blood vessels:

• Arteries (and arterioles) – carry blood away from the heart

• Capillaries – where nutrient and gas exchange occur

• Veins (and venules) – carry blood toward the heart.

Circulation

• Travels through pulmonary arteries to lungs where it gets fresh oxygen and becomes bright red

• Blood from lungs through pulmonary veins back to the heart's left side pump

• Pumped out into the body

The Heart

• Size of your fist • Thick muscular walls • Divided into two pumps • Each pump has two chambers • Upper chamber - atrium receives blood

coming in from the veins • Lower chamber - ventricle squeezes blood out

into the arteries

The Immune System

• Lymphatic system• Defence system

• Inside your body there is an amazing protection mechanism called the immune system. It is designed to defend you against millions of bacteria, microbes, viruses, toxins and parasites (pathogens) that would love to invade your body

THE LYMPHATIC SYSTEM

• A network of vessels and nodes throughout the body

• Lymph is a pale, yellow interstitial fluid (similar to blood plasma)

LYMPH

• Lymph serves to maintain fluid balance in the body

• Lymph nodes contain lymphocytes and macrophages (phagocytic monocytes) which serve to trap & destroy bacteria

LYMPH NODES