Bio
20B April 19, 2007 Respiratory Continued Circulatory System Endocrine System (Freeman Fig. 44-12a graph) relationship between: how much oxygen is stored (saturated) on hemoglobin and partial pressure of oxygen in blood within tissue. If hemoglobin only has 20% of oxygen, the other 80% is in the tissues. At a low partial pressure of oxygen in blood within tissues, there is a low amount of oxygen stored in hemoglobin. At a high partial pressure of oxygen in blood within tissues, there is a higher amount of oxygen stored in hemoglobin. The S curve means that it is cooperative binding. The Bohr Effect: As the pH levels drop, it is easier for hemoglobin to dump oxygen into the tissues (Freeman Fig. 44-12a graph) The Heart o Muscle Fibers of the Heart: Myocardium (highly specialized) Atrial muscle Ventricular muscle Contract like skeletal muscle but: the duration of relaxation between contractions is longer (prevents lethal constant contraction state) Special excitatory, conductive muscle serves as pacemaker Ventricles are more muscular than atria Left ventricle is more muscular than the right Left ventricle has to deliver blood at high pressure Because of this muscle arrangement, the Heart rotates slightly when it pumps o Specialized electrical conducting areas of the Heart & Self Regulation of Heart Rate (Campbell Fig. 42.7) Sino-Atrial (SA) node (pacemaker) Sets the rate and timing at which cardiac muscle cells contract Atrium contracts Atrio-Ventricular (AV) node Impulses from the SA node travel to the AV node At the AV node, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract Ventricles contract A-V bundle Purkinje fibers o ECG Wave Form (Electrocardiogram) P-wave: atrial depolarization QRS Waves: ventricular depolarization T-wave: repolarization of ventricles Depolarization leads to contraction Campbell Fig. 42.6
Circulation o Invertebrates have an open circulatory system blood pumped by arteries but "oozes" back to heart o Vertebrates have a closed circulatory system (more efficient) Heart, arteries, and veins Represents a major evolutionary advancement Campbell Fig. 42.4 Fish have a single circuit with a two chambered heart Amphibians (three chambers), Reptiles, Mammals, and Birds have two circuits (all but amphibians have four-chambered hearts) Reptiles have a shunt in which they can by-pass the lungs and send blood straight to the rest of the body. o Structure of blood vessels depends on its job (Freeman Fig. 44.15b) Arteries dampen blood pressure (muscular and elastic) Veins transport blood back to the heart under much lower pressure Capillaries are the smallest blood vessel (Freeman Fig. 44.15b) Deliver blood to tissues so they are very thin and facilitate gas exchange between blood and tissues Campbell Fig. 42.8 Arteries have more smooth muscle Veins have valves because they have less pressure but still must maintain flow to the heart o Blood Pressure Systolic pressure: pressure of blood pumping out to the body (high number and when ventricles are contracting) Diastolic pressure: pressure of system in between heart beat (lower number) High number is when the blood just starts to go through and the person can hear the blood, low number is when they don't hear the blood anymore Freeman Fig. 44.23 o Special Structures Pre-capillary sphincters (Campbell Fig. 42.11) Restrict blood flow Increased regulation Vaso-dilate (open up) Vaso-constrict (closed up) Blood Flows in veins (Campball Fig. 42.9) Valves (no backflow) Muscular action o Marine Mammals are masters of controlled circulatory system (shunting blood to the most needed places when swimming under water) Skin and appendages will have least blood, most blood will go to brain, heart and needed organs o Pattern of Blood Flow in the Heart
Heart > Aorta (out to body) > Arteries >Arterioles > Capillaries > Venules > Veins > Vena Cava > Heart (Red is oxygenated, blue is deoxygenated, note change in arrow size, corresponds to size of vessel) Venous Return when blood is going back to heart o The Effects of Exercise on the cardiovascular system 5 main effects of training Change in heart size (Depends on type of exercise) o Endurance athletes ventricular increase cavity (more left than right), normal wall thickness o Non-Endurance athletes normal cavity but increased ventricular wall thickness (left ventricle more than right) o Can become grossly oversized and lead to complications Decreased resting heart rate (years of training) Increased stroke volume (amount of blood pumped with each heart beat) Increased blood volume (# of RBCs and plasma) and hemoglobin concentration, helps carry more oxygen in RBCs Changes in skeletal muscle Endocrine System (Chemical Signals in Animals) o How the Body talks to itself using chemical signals called hormones o Key Concepts What are hormones? Where do they come from? How do they function? Examples of hormonal regulation o Overview: The Body's Long-Distance messengers/regulators Animal hormones are: Chemical signals Secreted into the circulatory system from glands or organs Effective at low concentrations Hormones reach all parts of the body Only target cell that are equipped to respond o Regulating Physiology by Two Systems Animals have two systems of internal communication and regulation Nervous system (next lecture) Endocrine system Nervous system conveys high-speed electrical signals along specialized cells called neurons Endocrine system secretes hormones that coordinate slower but longer-acting responses o Overlap Between Endocrine and Nervous Regulation
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Both systems function together in maintaining Homeostasis Development Reproduction Specialized nerve called known as neurosecretory cells release neurohormones into the blood Both endocrine hormones and neurohormones function as longdistance regulators of many physiological processes Chemical Signaling in Animals (Freeman Fig. 47.1) Autocrine signals: act on the same cell that secretes them Paracrine signals: diffuse locally and act on neighboring cells Endocrine signals: are hormones carried between cells by blood or other body fluids Neural signals: diffuse a short distance between neurons Neuroendocrine signals: are released from neurons but act on distant cells Pheromones: are released into the environment and act on a different individual Hormones can have a profound effect on the body, one mice given human growth hormone grew much larger than a mouse from the same litter The structure and function of hormones Hormones are secreted chemical signals that travel to target cells They are effective at extremely low concentrations Slower response compared to nervous system Their action is amplified through changes in gene expression or activation of enzymes Effective at regulating homeostasis (e.g. metabolism and metabolic fuels) Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses Hormones convey information via the bloodstream to target cells throughout the body Three major classes of molecules functions as hormones in vertebrates o Water soluble (target something outside of a cell) Proteins and peptides Amines derived from amino acids o Lipid soluble (can go through cell membrane [lipid bilayer]) Steroids Signaling Target Sites Using Hormones Signaling by any of these hormones involves three key events Reception (binds to target site Signal transduction Response
Where the hormone binds to the receptor depends on its characteristics Water soluble Lipid soluble o Freeman Fig. 47.3 Polypeptides Secretin Not lipid soluble; binds to receptors on surface of target cell Amino Acid Derivatives Epinephrine Most not lipid soluble; binds to receptors on surface of target cells Steroids Cortisol Lipid soluble o What happens next? Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm or a change in gene expression The same hormones may have different effects on target cells that have Different receptors for the hormone Different signal transduction pathways Different proteins for carrying out the response o The Human Endocrine System Overview Freeman Fig. 47.4 Hypothalamus o CRH, ADH, oxytocin Pituitary Gland Thyroid Gland (metabolism) o Thyroxine and calcitonin Adrenal Gland o Epinephrine, cortisol, and aldosterone Kidneys o Erythropoietin (EPO) Testes o testosterone