Anatomy and Physiology II with Lab (D313)

Comprehensive Study Notes: SCIE 1012 D313 Anatomy and Physiology II with Lab

1. The Nervous System

Definition: Neurons are specialized cells responsible for transmitting electrical and chemical signals throughout the body.

Key Components:

• Cell Body (Soma): Contains the nucleus and organelles.

• Dendrites: Branch-like extensions that receive signals from other neurons.

• Axon: A long fiber that transmits electrical impulses away from the cell body.

• Myelin Sheath: A fatty layer (produced by Schwann cells in PNS and oligodendrocytes in CNS) that insulates axons, speeding up signal transmission.

• Nodes of Ranvier: Gaps in the myelin sheath where action potentials "jump" (saltatory conduction).

Types of Neurons:

1. Sensory (Afferent) Neurons: Carry signals from sensory receptors to the CNS (e.g., touch, temperature).

2. Motor (Efferent) Neurons: Transmit signals from CNS to muscles/glands (e.g., muscle contraction).

3. Interneurons: Facilitate communication between neurons within the CNS.

Example: When you touch a hot stove, sensory neurons send a signal to your spinal cord, interneurons relay the message, and motor neurons trigger muscle withdrawal (reflex arc).

Central Nervous System (CNS)

• Components: Brain and spinal cord.

• Function: Integration and command center; processes sensory input and coordinates responses.

Peripheral Nervous System (PNS)

• Components: All nerves outside the CNS (cranial and spinal nerves).

• Divisions:

  • Somatic Nervous System: Controls voluntary movements (e.g., skeletal muscles).

  • Autonomic Nervous System (ANS): Regulates involuntary functions (e.g., heartbeat, digestion).

    • Sympathetic: "Fight or flight" (increases heart rate).

    • Parasympathetic: "Rest and digest" (slows heart rate).

Clinical Connection: Multiple sclerosis (MS) is an autoimmune disease where the immune system attacks the myelin sheath in the CNS, disrupting nerve signaling.

2. The Endocrine System

The endocrine system is a complex network of glands and organs that produce, store, and release hormones into the bloodstream. These hormones act as chemical messengers that regulate various bodily functions, including growth, metabolism, mood, sexual function, and even stress response.

Definition: Hormones are biochemical substances that help control the activity of cells and organs in the body. They are produced by various glands in the endocrine system and travel through the bloodstream to target organs, where they initiate a specific response.

Example:

• Insulin: Produced by the pancreas, insulin regulates blood glucose levels by facilitating the uptake of glucose into cells, where it can be used for energy. This process is vital for maintaining a stable blood sugar level.

1. Glands:

   • Pituitary Gland: Often referred to as the "master gland," the pituitary gland produces hormones that control other endocrine glands, including the thyroid, adrenal glands, and gonads.

   • Thyroid Gland: Regulates metabolism, growth, and development by producing hormones such as thyroxine (T4) and triiodothyronine (T3).

   • Adrenal Glands: These glands, located on top of the kidneys, produce hormones like adrenaline and cortisol, which are essential for the body's response to stress.

   • Pancreas: As mentioned, the pancreas releases insulin to lower blood sugar levels and glucagon to raise blood sugar levels.

   • Gonads (Ovaries and Testes): These glands produce sex hormones such as estrogen, progesterone, and testosterone, which are responsible for regulating reproductive functions and secondary sexual characteristics.

   • Parathyroid Glands: These small glands produce parathyroid hormone (PTH), which regulates calcium and phosphate balance in the body.

2. Feedback Loops:

   • Negative Feedback: This is the most common type of feedback loop in the endocrine system. It works to maintain homeostasis (balance). For example, when blood sugar levels rise after eating, insulin is released to lower it. When blood sugar levels drop, insulin secretion decreases, preventing hypoglycemia.

     • Example: The regulation of thyroid hormone levels. If the thyroid produces too much hormone, the pituitary gland detects the increased levels and reduces the release of thyroid-stimulating hormone (TSH), which in turn lowers thyroid hormone production.

   • Positive Feedback: In contrast, positive feedback amplifies a change. A classic example of this is the release of oxytocin during childbirth. Oxytocin stimulates uterine contractions, which in turn stimulate the release of more oxytocin, amplifying the contractions until the baby is born.

3. Disorders of the Endocrine System:

   • Diabetes Mellitus: This is a condition where the body has problems regulating blood sugar. There are two main types:

     • Type 1 Diabetes: The immune system attacks and destroys insulin-producing cells in the pancreas. This leads to a lack of insulin and high blood sugar levels.

     • Type 2 Diabetes: In this condition, the body becomes resistant to insulin, or the pancreas doesn't produce enough insulin, leading to elevated blood sugar levels.

   • Hypothyroidism: This occurs when the thyroid gland doesn’t produce enough thyroid hormones, leading to symptoms like fatigue, weight gain, and depression.

   • Hyperthyroidism: This is when the thyroid produces too much hormone, which can lead to weight loss, anxiety, and rapid heart rate.

   • Cushing's Syndrome: Caused by excess cortisol production, usually from an adrenal gland tumor or prolonged use of corticosteroid medication. It can result in weight gain, high blood pressure, and muscle weakness.

   • Addison's Disease: This occurs when the adrenal glands do not produce enough cortisol and aldosterone, leading to symptoms like fatigue, weight loss, and low blood pressure.

3. Cardiovascular System

The cardiovascular system, also known as the circulatory system, is responsible for transporting blood, nutrients, gases, and wastes throughout the body. The heart is the central organ in this system, functioning as a pump to ensure the continuous flow of blood through two main circulatory routes: pulmonary and systemic circulation.

1. Heart Chambers:

   • Atria (Receiving Chambers): There are two atria in the heart—right atrium and left atrium. These chambers receive blood from the body and lungs.

     • The right atrium receives deoxygenated blood from the body through the superior and inferior vena cava.

     • The left atrium receives oxygenated blood from the lungs through the pulmonary veins.

   • Ventricles (Pumping Chambers): The heart has two ventricles—right ventricle and left ventricle—that pump blood to the lungs and the rest of the body, respectively.

     • The right ventricle pumps deoxygenated blood into the lungs through the pulmonary artery for oxygenation.

     • The left ventricle pumps oxygenated blood into the aorta and throughout the body to deliver oxygen and nutrients to tissues and organs.

2. Blood Pathway:

   • Pulmonary Circulation:

     • This is the route that carries deoxygenated blood from the heart to the lungs and back. The right side of the heart (right atrium and right ventricle) is responsible for this circulation.

     • Blood flows from the right atrium to the right ventricle, then is pumped through the pulmonary artery to the lungs, where it picks up oxygen and releases carbon dioxide.

     • Oxygenated blood returns to the left atrium via the pulmonary veins.

   • Systemic Circulation:

     • This pathway carries oxygenated blood from the heart to the body and back. The left side of the heart (left atrium and left ventricle) handles this circulation.

     • Oxygen-rich blood flows from the left atrium to the left ventricle, which then pumps it into the aorta, the main artery of the body.

     • The blood is distributed through various arteries to the organs and tissues. Once the oxygen is delivered, the blood returns to the right atrium via veins, such as the superior and inferior vena cava.

An electrocardiogram (ECG) is a diagnostic tool that measures the electrical activity of the heart. It provides valuable information about the heart's rhythm, electrical conduction, and potential abnormalities. The ECG records the heart's electrical impulses through the following waves:

• P Wave: Represents atrial depolarization, which causes the atria to contract and push blood into the ventricles.

• QRS Complex: Represents ventricular depolarization, which causes the ventricles to contract and pump blood to the lungs or the body.

• T Wave: Represents ventricular repolarization, when the ventricles relax and prepare for the next contraction.

The ECG is crucial for detecting arrhythmias, heart attacks, and other cardiac conditions.

The cardiac cycle refers to the sequence of events that occur during one complete heartbeat, including the contraction (systole) and relaxation (diastole) of the heart's chambers:

• Systole (Contraction Phase): The ventricles contract, pumping blood into the pulmonary artery (from the right ventricle) and the aorta (from the left ventricle). The atria are in diastole during this time, filling with blood.

• Diastole (Relaxation Phase): The heart chambers relax, allowing the atria to fill with blood from the veins. As the atria contract, blood flows into the ventricles, preparing for the next systole.

This cycle repeats continuously, ensuring a steady flow of blood through the heart, lungs, and body.

• Heart disease: Including heart attack and heart failure.

• Stroke: High blood pressure can damage blood vessels in the brain, leading to an increased risk of stroke.

• Kidney disease: The kidneys' blood vessels can be damaged, affecting their function.

Hypertension can be managed with lifestyle changes (e.g., a healthy diet, exercise, stress management) and medications, such as diuretics, ACE inhibitors, or beta-blockers, which help control blood pressure.

4. Respiratory System

The respiratory system is responsible for the exchange of gases—primarily oxygen and carbon dioxide—between the atmosphere and the blood. This system ensures that oxygen is supplied to the body’s tissues and carbon dioxide is removed. The primary organs involved in this system include the lungs, diaphragm, trachea, and bronchi.

Breathing, also known as ventilation, involves the movement of air into and out of the lungs. The process of breathing is divided into inspiration (inhaling) and expiration (exhaling), and it is governed by the principles of pressure and volume changes in the thoracic cavity, particularly in relation to the diaphragm and chest wall.

1. Inspiration (Inhalation):

   • Mechanism: When you inhale, the diaphragm (a dome-shaped muscle below the lungs) contracts and moves downward, while the intercostal muscles (muscles between the ribs) contract, expanding the rib cage outward. This increases the volume of the thoracic cavity.

   • Pressure and Volume Changes: As the volume inside the lungs increases, the pressure inside the lungs decreases relative to the external atmospheric pressure. This causes air to flow into the lungs from the outside environment, as air moves from areas of higher pressure to lower pressure.

2. Expiration (Exhalation):

   • Mechanism: During expiration, the diaphragm relaxes and moves upward into its dome shape, and the intercostal muscles relax, causing the rib cage to return to its normal position.

   • Pressure and Volume Changes: As the thoracic cavity’s volume decreases, the pressure inside the lungs increases. When the pressure inside the lungs becomes higher than the pressure of the outside air, air is pushed out of the lungs.

The primary function of the respiratory system is to facilitate gas exchange, particularly oxygen (O₂) and carbon dioxide (CO₂), between the air in the lungs and the blood.

1. Alveolar Exchange:

   • The alveoli, tiny air sacs in the lungs, are the site where gas exchange occurs. Oxygen from the inhaled air passes through the thin walls of the alveoli and enters the capillaries, where it binds to hemoglobin in red blood cells.

   • At the same time, carbon dioxide, which is a waste product of cellular metabolism, moves from the blood into the alveoli to be exhaled out of the body.

2. Oxygen Transport:

   • Oxygen is transported via the blood from the lungs to the tissues. It binds to hemoglobin in red blood cells, which carries it throughout the body to be used by cells for metabolic processes.

3. Carbon Dioxide Removal:

   • Carbon dioxide is transported from the tissues to the lungs in three main forms: dissolved in plasma, bound to hemoglobin, and in the form of bicarbonate ions (HCO₃⁻). Once in the lungs, carbon dioxide is expelled during expiration.

COPD is a group of progressive lung diseases that cause difficulty breathing. It primarily includes chronic bronchitis and emphysema. COPD is typically caused by long-term exposure to irritants like cigarette smoke or air pollution.

1. Chronic Bronchitis: Characterized by inflammation and excess mucus production in the bronchi (airways), which leads to narrowed airways and difficulty expelling air.

2. Emphysema: Involves the destruction of the alveolar walls, reducing the surface area available for gas exchange. This leads to difficulty absorbing oxygen and expelling carbon dioxide.

Symptoms of COPD:

• Chronic cough

• Shortness of breath, especially during physical activity

• Wheezing

• Increased mucus production

Management: COPD is chronic and progressive, but treatment focuses on symptom management and slowing the progression of the disease. This may include smoking cessation, medications (bronchodilators, steroids), and oxygen therapy.

Spirometry is a common test used to measure lung function and diagnose respiratory conditions, including COPD, asthma, and restrictive lung diseases. It measures the volume and flow of air that can be inhaled and exhaled, providing insights into how well the lungs are working.

Key Spirometry Measurements:

• Forced Vital Capacity (FVC): The total amount of air that can be forcefully exhaled after taking a deep breath.

• Forced Expiratory Volume in 1 second (FEV₁): The amount of air that can be exhaled in the first second of a forced exhalation.

• FEV₁/FVC Ratio: This ratio helps diagnose obstructive lung diseases like COPD. A lower ratio suggests obstruction, as in COPD, where the lungs cannot expel air as efficiently.

Interpretation of Results:

• A normal FEV₁/FVC ratio is around 70% to 80%.

• A reduced ratio (often less than 70%) indicates obstructive diseases, like COPD or asthma.

Spirometry is essential in monitoring respiratory conditions, assessing lung health, and determining the appropriate treatment.

5. Renal System

The renal system, also known as the urinary system, is responsible for filtering blood, removing waste products, maintaining fluid balance, and regulating electrolytes, including sodium, potassium, and calcium. The kidneys, the primary organs of this system, play a key role in maintaining homeostasis.

The nephron is the functional unit of the kidney, and each kidney contains approximately one million nephrons. The nephron filters blood, reabsorbs essential nutrients, and secretes waste products into the urine. The nephron consists of several key structures:

1. Filtration (Glomerulus):

   • The process of filtration begins in the glomerulus, a network of capillaries within the renal corpuscle. Here, blood enters through the afferent arteriole and is filtered by the glomerular membrane.

   • Filtration occurs as blood pressure forces water, small molecules (like glucose, electrolytes, and amino acids), and waste products (like urea) from the blood into the Bowman's capsule, a cup-shaped structure surrounding the glomerulus. Larger molecules, such as proteins and blood cells, are too large to pass through the filtration membrane and remain in the blood.

   • This initial filtrate, often referred to as glomerular filtrate, contains water, salts, glucose, amino acids, and waste products, but lacks large proteins and blood cells.

2. Reabsorption (Proximal Convoluted Tubule):

   • After filtration, the filtrate enters the proximal convoluted tubule (PCT), where the process of reabsorption begins.

   • The PCT reclaims vital nutrients like glucose, amino acids, and vitamins and also reabsorbs about 65-70% of the filtered sodium, potassium, and water back into the blood via the surrounding capillaries (peritubular capillaries).

   • This process ensures that essential substances are returned to the body while waste products are kept in the filtrate for excretion.

3. Further Reabsorption and Secretion (Loop of Henle, Distal Convoluted Tubule, and Collecting Duct):

   • In the loop of Henle, water and salts are reabsorbed, with the descending limb being permeable to water and the ascending limb to salts. This helps create a concentration gradient that allows the kidneys to concentrate urine.

   • The distal convoluted tubule (DCT) further fine-tunes the reabsorption of sodium, potassium, and calcium ions and plays a role in acid-base balance by regulating hydrogen ions.

   • The collecting duct finalizes water and salt reabsorption under the influence of hormones like antidiuretic hormone (ADH), which controls the amount of water reabsorbed. This allows the kidneys to adjust urine concentration based on the body’s hydration status.

One of the critical functions of the kidneys is to maintain the body’s acid-base balance by regulating the pH of the blood, which is normally around 7.4. The kidneys help manage pH through several mechanisms:

1. Bicarbonate (HCO₃⁻) Reabsorption:

   • The kidneys reabsorb bicarbonate ions (HCO₃⁻) from the filtrate in the proximal tubule and distal tubule, which helps buffer the blood and maintain a stable pH.

2. Hydrogen Ion (H⁺) Secretion:

   • The kidneys also secrete hydrogen ions (H⁺) into the urine. This process primarily occurs in the proximal tubule and distal tubule. The secretion of hydrogen ions removes excess acid from the blood, helping to maintain the proper pH balance.

3. Ammonia Production:

   • The kidneys can produce ammonia (NH₃), which combines with hydrogen ions to form ammonium (NH₄⁺), a form of excretion that removes acid from the body without significantly affecting the pH of the urine.

These mechanisms allow the kidneys to regulate the acid-base status of the body, ensuring that the blood’s pH remains within a narrow, optimal range for proper cellular function.

Kidney failure, or renal failure, occurs when the kidneys lose their ability to function properly. This can happen suddenly (acute kidney failure) or gradually (chronic kidney failure). The kidneys are responsible for filtering blood, balancing electrolytes, maintaining fluid levels, and regulating pH, so kidney failure has serious consequences for the body.

1. Acute Kidney Failure:

   • This type of kidney failure develops suddenly and is often caused by conditions that decrease blood flow to the kidneys, such as severe dehydration, heart failure, or shock, or by obstruction of the urinary tract (e.g., kidney stones).

   • Symptoms include decreased urine output, swelling, nausea, and confusion. Acute kidney failure can be reversible if treated promptly.

2. Chronic Kidney Disease (CKD):

   • Chronic kidney disease is a gradual loss of kidney function, often due to long-term conditions like hypertension (high blood pressure) or diabetes.

   • In CKD, the kidneys slowly lose their ability to filter waste, regulate fluid balance, and maintain electrolyte levels, which can lead to dangerous complications.

   • The disease progresses through stages, and in the final stage, called end-stage renal disease (ESRD), dialysis or a kidney transplant is needed to perform the kidneys' function.

Symptoms of kidney failure include:

• Fatigue and weakness

• Swelling in the legs, ankles, or feet (edema)

• Shortness of breath

• Decreased urine output

• Nausea and vomiting

Treatment options for kidney failure vary depending on the type and stage of failure:

• Dialysis: This treatment uses a machine to filter waste products from the blood when the kidneys are no longer able to do so.

• Kidney Transplant: In cases of end-stage renal disease, a kidney transplant may be necessary, where a healthy kidney from a donor is surgically implanted into the patient.