Human Systems Function and Interactions

There are 11 organ systems in humans

Nervous System - coordinates the body’s response to changes in internal and external

environments• Contains brain, spinal cord, and nerves• It is the fast-acting control system of the body;

responds to internal and external changes by activating appropriate

muscles and glands. • Neurons – nerve cells

• Neurotransmitters help messages go from neuron to neuron

• Two parts – peripheral which has sensory and motor neurons that

sends messages to and from sense organs, muscles and other organs; central – includes brain and spinal cord which is the control center of body

Integumentary System – acts as a barrier against infection and injury; helps regulate

body temperature

• Consists of the hair, skin, and nails.• Forms the external body covering; protects

deeper tissues from injury synthesizes vitamin D; and is the site of cutaneous receptors (pain, pressure, ect.) and sweat and oil glands

• Skin - largest organ in the body• Outermost layer – epidermis (contains keratin

and melanin); has nonliving cells• Underneath layer – dermis; has living cells and

blood vessels; also has sweat and oil glands

Respiratory System – provides for the exchange of oxygen and carbon dioxide

• Contains the nasal cavity, pharynx, larynx, trachea, and lungs.

• Keeps blood constantly supplied with oxygen and removes carbon dioxide

• Diaphragm helps move air into and out of lungs

• Gas exchange takes place in the alveoli

Digestive System – converts food into simpler substances the body can use

• Contains the mouth, esophagus, liver, stomach, small intestine, and large intestine

• Breaks down food into absorbable units that enter the blood for distribution to the body cells; indigestible food is eliminated as feces

• Begins in the mouth• Most chemical digestion occurs in small

intestine• Water absorbed in the large intestine (colon)• Food passes through the system in 12 to 24

hours

Excretory System – eliminates wastes and helps maintain homeostasis

• Contains the kidneys, ureters, urinary bladder, and urethra

• Eliminates nitrogenous wastes from the body; regulates water, electrolyte, and acid-base balance of the blood

• Where liquid waste is eliminated• Three organs in the body are specialized for

excretion: lungs, skin and kidney• Major organ of excretion is the kidney

Skeletal System – supports the body and helps protect internal organs; allows

movement; stores minerals and makes red blood cells

• Consists of bones and joints• provides a framework the muscles to use to cause

movement• Place where red blood cells made• Where bones connect there are joints (5 kinds – ball and

socket (shoulder); pivot (neck); hinge – finger, elbow, knee); gliding (wrists and ankles); saddle (thumb)

• Ligaments – hold bones together• Tendons – attach muscle to bone

Muscular System – works with skeleton to provide voluntary movement; helps

circulate blood and move food

• allows manipulation of the environment, locomotion, and facial expression; maintains posture; produces heat

• 3 types of muscles – smooth (blood vessels and digestive organs); cardiac – (heart); skeletal (attached to bones)

Circulatory System – brings oxygen, nutrients and hormones to cells;

removes wastes; helps fight infection; helps regulate body

temperature

• Contains the heart and blood vessels• The blood vessels of the cardiovascular system transport

blood, which carries oxygen, carbon dioxide, nutrients, and wastes; the heart pumps blood

• Heart pumps blood throughout body through blood vessels• Heart has 4 chambers: blood flows from right atrium(upper

chamber) to right ventricle (lower chamber) to left atrium to left ventricle

• Arteries – carry blood away from the heart• Veins – carries blood back to the heart• Capillaries – tiny vessels that allow the exchange of

materials between blood and other parts of the body• Red blood cells – carry oxygen helped by hemoglobin• 2 loops: pulmonary circulation – blood goes to lungs where

it is oxygenated; systemic circulation blood goes throughout body

Endocrine System – controls growth, development and metabolism; helps

maintain homeostasis

• Hormones – substances secreted by cells to regulate the activity of other body cells

• Endocrine glands – secrete hormones directly into the blood

Reproductive System – produces egg and sperm

• Includes the penis, testes, ductus deference and prostate gland in the males, and the ovaries, fallopian tubes, uterus, and vagina in the female

• The overall function of the reproductive system is to produce offspring

• In females, helps nurture and protect developing embryo

Immune System – protects the body from disease

• Lymphatic structures also collect fluid lost from blood vessels and returns it to the circulatory system

• The lymphatic system contains the lymphatic vessels, lymph nodes, spleen, and thymus

• The lymphatic system picks up fluid leaked from blood vessels and returns it to the blood and houses white blood cells (lymphocytes) involved in immunity

• To function properly, it must detect a wide variety of agents, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue

• Pathogens are microscopic organisms that can harm the body

• Nonspecific defenses do not trigger specific pathogens (skin and mucus membranes)

• Disorders of the immune system can result in autoimmune diseases, inflammatory diseases and cancer

Human Systems, Homeostasis and

Feedback Inhibition

• Every cell in your body is both an independent unit and an interdependent part of a larger community (the entire organism)

• The broadest levels of organization within multicellular organisms are cells, tissues, organ, and organ systems

• The eleven organ systems of the human body work together to maintain homeostasis in the body as a whole

There are four types of tissue in the human body:

• Epithelial – glands and tissues that cover internal and external body surfacesGlands are structures that make and secrete a

particular product (ex. sweat, tears, hormones)

• 2 kinds of gland in the human bodyExocrine glands- release substances into ducts

(ex. sweat, tears, digestive juices)Endocrine glands – release substance into

bloodstream that target cells in another part of the body (ex. hormones)

• Connective – provide support for the body and connects its parts

• Nervous – transmits nerve impulses throughout the body

• Muscle – along with the bones enables a body to move

Homeostasis is the process where the body keeps internal conditions relatively constant despite changes

in external conditions• Your body has the ability to regulate literally

trillions of cells in nearly constant activity, and keep everything in your body running smoothly.

• Nearly every organ system plays a role in maintaining a constant internal environment

• Communication within the body is essential for maintaining homeostasis

• Communication is accomplished chiefly by the nervous and endocrine systems. The nervous system uses electrical impulses delivered by nerves to communicate, and the endocrine system uses blood borne hormones

• A nonliving example of this is the heating system of a house–When the temperature drops below a set

point the thermostat turns the furnace on and then when the temperature rises above the set point the furnace turns off– The furnace only runs when needed – this is

an example of feedback inhibition

• Feedback inhibition (negative feedback) – a process in which a stimulus produces a response that opposes the original stimulus

• Systems controlled by feedback inhibition are generally fully automated and very stable

• Feedback inhibition is what biological systems (like the human body) use to achieve homeostasis

• The cellular environment responds to feedback from its own activities by switching on and off as needed

• The part of the brain that works like a thermostat to regulate and maintain a stable body temperature is the hypothalamus

• The hypothalamus does this by sending chemical messages that either speed up or slow down cellular activity

The body must also regulate the levels of glucose and glycogen in

the blood