Nervous, Circulatory, Respiratory Systems

Objectives

• Describe the structure of a neuron
• Compare different types of blood vessels
• Describe blood, blood components, and BP
• Explain how breathing rate is regulated

Nervous system includes

• brain
• spinal cord
• central nervous system
• peripheral nervous system

Nervous Tissue

• Neurons - structural and functional units. Transmit nerve impulses.
• Glial cells - provide support (eg, nutrients) for neurons

Neuron

• Cell body contains nucleus & organelles
• Dendrites receive nerve impulses
• Axon transmits nerve impulses

Myelin Sheath

• Surrounds axon
• Myelin is a lipid that insulates
• Myelin made by Schwann cells (glial)

Neuron Types

• Sensory carry impulses from tissue to SC and brain
• Motor carry impulses from brain and SC to muscles and glands
• Interneurons carry impulses between sensory and motor

Blood Vessels

• Arteries carry blood away from heart
• Veins carry blood toward heart
• Capillaries connect veins and arteries

Blood Vessels

• Constrict or dilate in response to endocrine or nervous system
• Change amount of blood flow to different organs
• Help maintain homeostasis (eg, lose or conserve body heat)

Blood Pressure

• Force exerted by circulating blood on walls of blood vessels
• Highest on arteries
• Lowest on veins
• When BP is checked, is is measuring arterial pressure

Blood

• Fluid connective tissue
• Transports gases and hormones
• Controls body's pH
• Fluid part is called plasma (yellow-golden)

Blood Cells

• RBCs contain hemoglobin & carry O2 
• White are larger but fewer.  Immune defense
• Platelets are involved in clotting.

Blood Type

• ABO type
• Rhesus 

Respiratory System

Inhaling results from the contraction of the diaphragm, a large, sheet-like muscle below the lungs. Larger chest volume decreases internal pressure, allowing air to rush into the lungs.

When the diaphragm relaxes, pressure increases, forcing air out.

Diaphragm contractions are controlled by the brain stem through the automatic nervous system.

The brain stem monitors the level of CO2 in the blood. When levels are too high, it signals the diaphragm to contract more often. This keeps pH within a narrow range.

Excretory System

Excretion is the process of removing waste and excess water from the body and is one of the ways of maintaining homeostasis.

Organs

• Kidneys (main ones) control amount of water lost in urine
• Large intestine eliminates solid waste
• Liver breaks down excess amino acids and toxins
• Skin eliminates excess water and salt via sweating
• Lungs exhale water vapor and carbon dioxide