Homeostasis and the Organization of the Animal Body

Homeostasis u Homeostasis (“steady state”) – Maintenance of nearly constant internal conditions – Snakes are cold-blooded (ectothermic or poikilothermic) u. Heat & thus their body temperature is absorbed from environment – Humans are warm-blooded (endothermic or homeothermic) u. Body temperature is generated internally

Feedback Systems u Homeostasis is controlled by feedback u Feedback loops used by organisms to help maintain homeostasis & have 3 major components: – Receptors - respond to various stimuli to which organism may be exposed – Control center - decides to which stimuli organism should respond to & what is the right response – Effectors - receive instructions from control center

Homeostasis u A. Negative feedback is used to u u u Slow down, shut off, or reverse a physiological process & Return it to an optimal condition B. Positive feedback enhances or intensifies a process

signal (temperature to control center) Negative feedback signal to turn off effector signal to turn on effector thermometer (sensor) heater (effector) heat output decreases signal to control center nerve signal to turn off effector nerve signal (temperature) to control center heat output increases hypothalamus (control center) nerve endings (sensor) heat output (shivering) decreases Positive feedback nerve signal to control center signal to turn on effector Skeletal muscles (effector) hypothalamus (control center) uterine muscles (effector) uterus output level increases stretch receptors in cervix (sensor) nerve signal to turn on effector heat output (shivering) increases oxytocin release (signal to turn on effector) output level (contraction) increases

Circulation and Respiration

II. Circulatory systems u A. Circulatory system basics • • • 1. 2. 3. Fluid—blood Channels—vessels A pump—the heart

III. The vertebrate circulatory system u A. Functions • • 3. • • • 1. Transport of O 2 and CO 2 2. Distribution of nutrients Transport of waste 4. Distribution of hormones 5. Regulation of body temperature 6. Protection of the body against blood loss

The vertebrate circulatory system B. The heart 1. Structure a. Atria b. Ventricles

aorta pulmonary artery (to left lung) superior vena cava pulmonary artery (to right lung) left atrium pulmonary veins (from right lung) pulmonary veins (from left lung) atrioventricular valve right atrium semilunar valves atrioventricular valve right ventricle inferior vena cava descending aorta (to lower body) left ventricle ventricular septum heart muscle

The vertebrate circulatory system u Function • a. The cardiac cycle • • • 1) Systole—period of ventricle contraction 2) Diastole—relaxation of all the chambers followed by contraction of the atria

Oxygenated blood from lungs enters left ventricle. Deoxygenated blood from body enters right ventricle. Oxygenated blood is pumped to the body. (a) Atria contract, forcing blood into the ventricles. Deoxygenated blood is pumped to the lungs. Blood fills the atria and begins to flow passively into the ventricles. (b) Then the ventricles contract, (c) The cycle ends as forcing blood through arteries the heart relaxes. to the lungs and the rest of the body.

III. The vertebrate circulatory system u Function • b. Coordination of heart activity • 1) Atrioventricular and semilunar valves • 2) The sinoatrial node (SA node) • 3) The atrioventricular node (AV node)

aorta pulmonary artery (to left lung) superior vena cava pulmonary artery (to right lung) left atrium pulmonary veins (from right lung) pulmonary veins (from left lung) atrioventricular valve right atrium semilunar valves atrioventricular valve right ventricle inferior vena cava descending aorta (to lower body) left ventricle ventricular septum heart muscle

sinoatrial (SA) node atrioventricular (AV) node excitable fibers

The vertebrate circulatory system. Coordination of heart activity 4) Influences on heart rate a) Parasympathetic nervous system decreases heart rate b) Sympathetic nervous system increases heart rate c) Hormones

The vertebrate circulatory system u C. Blood • 1. Functions • • a. Transport of nutrients, gases, hormones, wastes b. Immune response

The vertebrate circulatory system • 2. Composition • a. Plasma— 55% to 60% • 1) 90% water • 2) Molecules of dissolved proteins, hormones, nutrients, gases, ions, and urea as a waste • b. Red blood cells—erythrocytes • 1) 99% of the total cellular component in the blood • 2) Carry oxygen bound to hemoglobin from the lungs to the tissue and buffer CO 2 carried from the tissues • c. White blood cells—leukocytes • 1) 1% of the total cellular component of blood • 2) Five white blood cell types • d. Platelets • 1) Cellular fragments from megakaryocyte in the bone marrow • 2) Function in blood clotting

platelets trapped red blood cell fibrin network

The vertebrate circulatory system u D. Blood vessels • 1. Arteries and arterioles • • a. Thick walls, smooth muscle with elastic tissue to withstand high pressure b. Carry blood away from the heart • 2. Capillaries • • a. Tiniest vessels; thin, single-cell thick for easy diffusion b. Exchange of materials between blood and body cells • 3. Venules and veins • • a. One-way valves in thin-walled vessels surrounded by thin layer of smooth muscle giving low resistance to blood flow, which is assisted by skeletal muscle b. Returns blood to the heart

capillaries arteriole venule capillary endothelium connective tissue (external layer) artery smooth muscle (middle layer) connective tissue endothelium (inner layer) vein

Red blood cells must pass through capillaries in single file. Capillary walls are thin and permeable to gases, nutrients, and cellular wastes.

III. The vertebrate circulatory system • 4. Distribution of blood flow • • a. Regulated by muscular walls of the arterioles b. Influenced by autonomic nerves, hormones, and other chemicals released from nearby tissues

jugular vein carotid artery aorta superior vena cava inferior vena cava lung capillaries pulmonary artery heart liver kidney intestine femoral vein femoral artery

valve open valve closed relaxed muscle contraction compresses vein valve closed

(b) (a) endothelium smooth muscle cholesterol in blood fatty core fibrous cap plaque

Heart Attack (Myocardial Infarction) A heart attack (myocardial infarction) occurs when heart muscle is damaged or destroyed because it does not get enough oxygen-rich blood to sustain life. Just as the heart supplies oxygen and nutrients to other parts of the body, blood vessels called coronary arteries supply needed blood to the heart. If one or more coronary arteries or the blood vessels that feed blood into the major arteries are blocked or narrowed, the heart muscle is deprived of oxygen. If the oxygen supply is cut off for more than several minutes, the heart cells suffer permanent injury or death.

Lymphatic system u 1. Structure • a. Complex network of thin-walled vessels • b. In proximity to the capillary network • c. Composed of cells with openings between them that act as one-way valves

(a) superior vena cava thoracic duct enters vein to vena cava thymus heart spleen thoracic duct lymph vessels lymph nodes valve prevents backflow white blood cells (b) lymph node

Lymph is transported into larger lymph vessels. interstitial fluid Blood capillaries leak fluid filtered from blood plasma. Interstitial fluid enters through valvelike openings between lymph capillary cells.

Lymphatic system • 2. Functions • • • a. b. c. Removal of excess fluid Transport of fats from the intestine Cellular body defense

The respiratory system u A. Functions of the respiratory system • 1. Works in conjunction with the circulatory system • 2. Provides oxygen for cellular respiration

Respiratory systems and gas exchange u A. Interrelated with circulatory system u B. Mechanisms of gas movement • 1. Bulk flow from areas of higher pressure to areas of lower pressure • 2. Simple diffusion at the tissue or lung level

1. Gases move in and out of the lungs by breathing. 2. O 2 and CO 2 are exchanged in the lungs by diffusion. right atrium alveoli (air sacs) left atrium right ventricle left ventricle 3. Gases dissolved in blood are transported by the circulatory system. 4. O 2 and CO 2 are exchanged in the tissues by diffusion.

VII. Human respiratory system u A. The conducting portion • 1. Carries air to the lungs • 2. Warms and moistens air moving through it • 3. Cilia that line the trachea, bronchi, and bronchioles filter dust particles

(a) nasal cavity pharynx epiglottis branch of pulmonary vein larynx esophagus trachea bronchiole alveoli branch of pulmonary artery bronchioles pulmonary artery pulmonary vein (b) capillary network

VII. Human respiratory system u B. Gas exchange portion • • • 1. The alveoli have an enormous surface area 2. Capillaries surround the alveoli 3. The mechanism of gas exchange and transport • • a. Oxygen and hemoglobin b. Carbon dioxide and bicarbonate ions

interstitial fluid capillary fluid layer alveolar cell nucleus air in alveolus alveolar membrane capillary cell nucleus red blood cell plasma capillary wall

VII. Human respiratory system u C. Mechanics of breathing • 1. Inspiration—active inhalation of air • • a. Diaphragm and rib muscles contract, making the chest cavity larger b. Chest expansion causes the lungs to expand; vacuum draws in air • 2. Expiration—passive exhalation of air when muscles are relaxed

air moves in ribcage expands air moves out lungs expand diaphragm contracts downward (a) Inhalation ribcage contracts lungs compress diaphragm relaxes upward (b) Exhalation

VII. Human respiratory system u D. Control of respiration • 1. Description of breathing • 2. Regulation of breathing by carbon dioxide