a&p exam 2
How does a hormone affect cells?
Hormones act as chemical messengers that travel through the bloodstream to target cells. They bind to specific receptors on or inside target cells, triggering a series of biological responses, such as enzyme activation, gene expression changes, or cellular metabolism alterations.
What are cell receptors?
Cell receptors are proteins found on the surface of cells or inside the cell that bind to specific molecules (such as hormones, neurotransmitters, or other signaling molecules). The binding of a hormone to its receptor induces a cellular response.
What controls most hormone concentrations?
Most hormone concentrations are controlled by feedback mechanisms, typically negative feedback, where the output of a hormone reduces the stimulus for further hormone production (e.g., the hypothalamic-pituitary-endocrine gland axis). Positive feedback is less common but amplifies the response, like during childbirth with oxytocin.
What is the effect of a steroid hormone binding to a receptor in a target cell?
Steroid hormones pass through the cell membrane and bind to intracellular receptors, forming a hormone-receptor complex. This complex enters the nucleus and binds to DNA, influencing gene expression and protein synthesis, affecting cell function.
What is meant by the terms upregulated and downregulated cell?
Upregulation refers to an increase in the number of receptors on a cell, making it more sensitive to a hormone. Downregulation refers to a decrease in receptor number, reducing sensitivity to a hormone.
Actions of Specific Hormones:
Growth Hormone (GH):
GH stimulates growth, cell reproduction, and regeneration. It promotes protein synthesis, enhances lipolysis (fat breakdown), and increases the production of insulin-like growth factor (IGF) from the liver.
Antidiuretic Hormone (ADH):
ADH regulates water balance by increasing water reabsorption in the kidneys, thus concentrating urine and decreasing water loss.
Triiodothyronine (T3) and Thyroxine (T4):
These hormones increase the metabolic rate, regulate growth and development, and influence the function of many organ systems, including the heart and digestive system.
Parathyroid Hormone (PTH):
PTH increases blood calcium levels by stimulating osteoclast activity in bones, enhancing calcium reabsorption in the kidneys, and activating vitamin D in the kidneys to increase calcium absorption from the intestines.
Adrenocorticotropic Hormone (ACTH):
ACTH stimulates the adrenal cortex to produce cortisol, which plays a key role in the body’s stress response and regulates metabolism.
Melatonin:
Melatonin regulates sleep-wake cycles (circadian rhythms) by promoting sleep and responding to light conditions.
Pituitary Gland and Hypothalamus:
Hormones released by the Anterior Pituitary:
The anterior pituitary releases:
Growth hormone (GH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Prolactin
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Hormones released by the Posterior Pituitary:
The posterior pituitary releases:
Antidiuretic hormone (ADH)
Oxytocin
Target cells for hypothalamic releasing hormones:
The target cells are located in the anterior pituitary, where these hormones trigger the release of pituitary hormones.
Diabetes and Related Conditions:
What is diabetes insipidus?
Diabetes insipidus is a condition where the kidneys are unable to conserve water due to insufficient ADH, leading to excessive urination and thirst.
Actions of Cortisol:
Cortisol, a steroid hormone, increases glucose production, suppresses the immune system, helps the body respond to stress, and regulates metabolism.
Actions of Insulin and Glucagon:
Insulin lowers blood glucose by promoting its uptake into cells for energy and storage as glycogen.
Glucagon raises blood glucose levels by stimulating the liver to release stored glucose.
Cause of Type 1 Diabetes Mellitus:
Type 1 diabetes is caused by an autoimmune destruction of insulin-producing beta cells in the pancreas.
Cause of Type 2 Diabetes Mellitus:
Type 2 diabetes is caused by insulin resistance and eventual beta-cell dysfunction, often linked to obesity and poor lifestyle choices.
Effects of Diabetes Mellitus:
Chronic high blood sugar can lead to complications such as cardiovascular disease, kidney damage, nerve damage, and impaired wound healing.
Blood Cells and Blood Disorders:
Describe an RBC (Red Blood Cell):
RBCs are biconcave, disc-shaped cells that lack a nucleus. Their primary function is to transport oxygen from the lungs to tissues and return carbon dioxide to the lungs for exhalation.
How are RBC levels regulated?
RBC production is regulated by erythropoietin (EPO), a hormone released from the kidneys in response to low oxygen levels. This stimulates the bone marrow to produce more RBCs.
Effects of Hypoxemia:
Hypoxemia (low oxygen levels in the blood) stimulates the release of erythropoietin (EPO) to increase RBC production.
What is a hematocrit?
Hematocrit is the percentage of blood volume that is occupied by red blood cells. A normal hematocrit is typically around 40-45%.
How long do RBCs live?
RBCs live about 120 days. Afterward, they are broken down in the spleen, liver, and bone marrow.
How are RBCs broken down?
The spleen and liver filter old RBCs. Hemoglobin is broken down into heme (which is converted to bilirubin) and globin (which is broken down into amino acids).
Normal pH of blood:
The normal pH of blood is approximately 7.35-7.45.
Structure of Hemoglobin:
Hemoglobin is a protein composed of four subunits, each containing a heme group that can bind one molecule of oxygen.
Underlying Cause of Sickle Cell Disease:
Sickle cell disease is caused by a genetic mutation in the hemoglobin gene, leading to the production of abnormal hemoglobin (HbS), which causes RBCs to sickle under low oxygen conditions.
Antigens in Type O, A, B, and AB blood:
Type O: No A or B antigens; anti-A and anti-B antibodies.
Type A: A antigens; anti-B antibodies.
Type B: B antigens; anti-A antibodies.
Type AB: Both A and B antigens; no anti-A or anti-B antibodies.
Rh-negative individual:
An individual who is Rh-negative lacks the Rh antigen on their RBCs. They can develop antibodies against Rh-positive blood if exposed.
Describe a Blood Platelet:
Platelets are small, disc-shaped cell fragments involved in blood clotting. They help form a blood clot by sticking to damaged blood vessel walls.
Petechiae:
Petechiae are small, red or purple spots on the skin caused by minor bleeds under the skin.
Blood Clot Formation Steps:
Vascular spasm occurs to constrict blood vessels.
Platelet plug formation occurs when platelets stick to the damaged site and release chemicals that attract more platelets.
Coagulation occurs with the activation of clotting factors, leading to fibrin formation and blood clot formation.
Blood Clot Breakdown Steps:
After clot formation, plasminogen is activated to plasmin, which dissolves fibrin and breaks down the clot.
Substances that dissolve blood clots:
Tissue plasminogen activator (tPA) and streptokinase are commonly used to dissolve blood clots.
Prothrombin Time:
Prothrombin time (PT) measures how long it takes for blood to clot, used to evaluate clotting disorders and the effectiveness of anticoagulant therapy.
Pulmonary Embolism:
A pulmonary embolism is a blockage in one of the pulmonary arteries in the lungs, usually caused by a blood clot.
Cardiovascular System:
Frank-Starling Law of the Heart:
The Frank-Starling law states that the heart will pump more blood if the heart muscle is stretched more (due to increased venous return), up to a point.
Cardiac Output Formula:
Cardiac Output (CO) = Stroke Volume (SV) × Heart Rate (HR).
Primary Function of the Cardiovascular System:
The primary function is to transport oxygen, nutrients, and hormones to tissues and remove waste products.
Function of the Systemic Circuit:
The systemic circuit carries oxygenated blood from the heart to the body and returns deoxygenated blood to the heart.
Structure of the Heart:
The heart consists of four chambers: two atria and two ventricles. It pumps blood to the lungs (pulmonary circuit) and the rest of the body (systemic circuit).
Name and Location of the Valves:
The atrial-ventricular valves (tricuspid on the right side, bicuspid/mitral on the left side) control blood flow between the atria and ventricles.
The semilunar valves (pulmonary valve, aortic valve) control blood flow from the ventricles into the pulmonary artery and aorta.
Best Positioning for Stethoscope:
Mitral valve: Over the apex of the heart, near the 5th intercostal space.
Aortic valve: Over the right second intercostal space near the sternum.
Blood Flow Pathway:
Blood flows from the vena cava → right atrium → right ventricle → pulmonary artery → lungs (for oxygenation) → pulmonary veins → left atrium → left ventricle → aorta → systemic circulation → vena cava.
Chambers Containing Oxygen-Poor Blood:
The right atrium and right ventricle contain oxygen-poor blood.
Layers of the Heart Wall and Pericardium:
Heart wall: Epicardium (outer layer), myocardium (muscle layer), endocardium (inner lining).
Pericardium: Outer fibrous layer, inner serous layer (visceral and parietal layers).
Cardiac Conduction Pathway:
The pathway of electrical conduction in the heart is as follows:
Sinoatrial (SA) Node: Located in the right atrium, it initiates the electrical impulse, setting the heart rate.
Atria: The impulse travels through the atria, causing atrial contraction.
Atrioventricular (AV) Node: The electrical impulse pauses briefly here, allowing the ventricles to fill with blood.
Bundle of His (AV Bundle): Carries the impulse into the interventricular septum.
Right and Left Bundle Branches: Spread the impulse to the right and left ventricles.
Purkinje Fibers: Conduct the impulse throughout the ventricles, leading to ventricular contraction.
ECG Waves:
P Wave: Represents atrial depolarization (the electrical impulse moving through the atria).
QRS Complex: Represents ventricular depolarization (the electrical impulse moving through the ventricles).
T Wave: Represents ventricular repolarization (the ventricles returning to their resting state after contraction).
Vagus Nerve and Sympathetic Stimulation:
Vagus Nerve Stimulation (Parasympathetic):
Stimulating the vagus nerve releases acetylcholine, which slows the heart rate by decreasing the electrical activity in the SA node.
This results in bradycardia (slower heart rate).
Sympathetic Stimulation:
Sympathetic nerve stimulation releases norepinephrine, which increases heart rate and contractility by stimulating the SA node and increasing the strength of each contraction.
This leads to tachycardia (faster heart rate).
Terms:
Tachycardia:
An abnormally high heart rate, usually greater than 100 beats per minute.
Bradycardia:
An abnormally low heart rate, typically less than 60 beats per minute.
Flutter:
A rapid but regular heart rhythm, especially in the atria, leading to a very fast heart rate.
Fibrillation:
A disorganized and ineffective electrical activity of the heart, either in the atria (atrial fibrillation) or ventricles (ventricular fibrillation), leading to ineffective heart function.
Infarction:
Tissue death due to a lack of blood supply, commonly referred to as a myocardial infarction (heart attack).
Blood Vessels Holding the Greatest Volume of Blood:
The venous system holds the greatest volume of blood in the body. Veins act as reservoirs because they have a larger lumen and thinner walls compared to arteries, allowing them to store more blood.
Key Terms in Cardiovascular Physiology:
End-Diastolic Volume (EDV):
The volume of blood in the ventricles at the end of diastole (just before the heart contracts).
Stroke Volume (SV):
The volume of blood ejected by the heart with each beat. It is the difference between EDV and end-systolic volume (ESV).
Venous Return:
The volume of blood returning to the heart from the body’s tissues. It is a key determinant of EDV and preload.
Total Peripheral Resistance (TPR):
The resistance to blood flow in the systemic circulation, primarily influenced by the diameter of arterioles.
Preload:
The degree of stretch of the ventricles at the end of diastole. It is influenced by venous return and determines the force of the next contraction (Frank-Starling mechanism).
Plasma Proteins and Osmotic Pressure:
Plasma proteins (especially albumin) contribute to the osmotic pressure of blood. They help maintain the fluid balance between blood vessels and tissues by attracting water into the blood vessels, preventing excessive fluid loss from the bloodstream.
Blood Pressure in the Large Systemic Arteries:
Blood pressure in the large systemic arteries is greatest during systole when the ventricles contract and pump blood into the arteries (the systolic pressure). The lowest pressure occurs during diastole when the heart is at rest (the diastolic pressure).
Major Arteries Branching off the Aorta:
The major arteries that branch off the aorta include:
Brachiocephalic artery (on the right side, which further divides into the right subclavian and right common carotid arteries)
Left common carotid artery
Left subclavian artery
Major Arteries of the Arm:
Subclavian artery (becomes the brachial artery)
Brachial artery (branches into the radial and ulnar arteries)
Function of the Papillary Muscles:
Papillary muscles are located in the ventricles and attach to the chordae tendineae of the heart valves (particularly the mitral and tricuspid valves). Their function is to contract during ventricular systole to prevent the valves from inverting and allowing backflow of blood.
Atherosclerosis:
Atherosclerosis is the buildup of fatty deposits (plaques) on the inner walls of arteries, which can lead to reduced blood flow, increased risk of clots, heart attacks, and strokes.
Control Center for Cardiovascular System:
The medulla oblongata in the brainstem is the control center for the cardiovascular system. It regulates heart rate, blood vessel dilation, and blood pressure via the autonomic nervous system (sympathetic and parasympathetic branches).
Effect of Reduced Venous Return:
A reduced venous return means less blood is returning to the heart, which can result in a lower end-diastolic volume (EDV) and stroke volume (SV), leading to a decrease in cardiac output.
Inspiration and Venous Blood Return:
During inspiration (breathing in), the diaphragm moves downward, which decreases thoracic pressure and helps draw blood from the veins into the heart (particularly into the right atrium), aiding venous return.