BPK105 Final

What are the functions of the urinary system?

• excretion

• regulation of blood volume and pressure

• regulation of blood solute concentrations

• regulation of extracellular fluid pH

• regulation of red blood synthesis

• regulation of vitamin D synthesis

What are the pressures that influence filtration at the glomerulus?

• glomerular capillary pressure - outward pressure from blood pressing on the fenestrated capillary walls, forces fluid and solutes out of the blood into the glomerular capsule. This pressure is higher than that in other capillaries of the body due to the smaller diameter of the efferent arteriole compared to that of the afferent arteriole and glomerular capillaries

• capsular pressure - inward pressure that opposes filtration, due to pressure from the filtrate fluid in the capsular space

• colloid osmotic pressure - inward pressure that opposes filtration, due to the osmotic pressure of plasma proteins in the glomerular capillaries. Through osmosis, these proteins draw fluid back into the glomerular capillary from the glomerular capsule. The colloid osmotic pressure is greater at the end of the glomerular capillary than at its beginning because there is a higher protein concentration at the end of the glomerulus

Describe reabsorption in the proximal convoluted tubule

• site of the majority of reabsorption

• have numerous microvilli, which dramatically increases the surface area available for reabsorption

• reabsorption of most solutes is linked to the diffusion of sodium into the cells of the proximal convoluted tubule

• this concentration gradient is established by active transport of sodium out of the proximal tubule

• this movement of sodium into these cells is responsible for the transport of many other solutes from lumen of the proximal convoluted tubule into cytoplasm of tubule cells

Describe reabsorption in the ascending and descending loops of Henle

• reabsorption of water into the descending limb:

  • epithelial tissue in the majority of deciding limb is simple squamous epithelial tissue, meaning that it is highly permeable to water

• reabsorption of solutes, but not water in ascending limb:

  • still has simple squamous but it has become impermeable to water, however it is still permeable to solutes, which exit the ascending limb, thereby again reducing concentration of filtrate

Describe reabsorption in the distal tubule and collecting duct

• some solutes (potassium and hydrogen) are not reabsorbed until the distal or collecting duct

• reabsorption of these solutes is generally under hormone control

• they are not always permeable to water, but hormones can change that

• reabsorption of water occurs thought osmosis when ADH is present

How is urine concentration influenced by aldosterone?

Stimulates an increase in the reabsorption of sodium and chloride. Water follows from filtrate into blood. So increase solute, decrease water content.

How is urine concentration influenced by ADH?

Promotes water conservation in kidneys by increasing permeability of distal convoluted tubule and collecting duct to water. So more water is reabsorbed and produces a small volume of concentrated urine.

How is urine concentration influenced by ANH?

Decreases sodium reabsorption in kidney. Therefore, sodium remains in tubules of nephron, water moves by osmosis into tubules of the the nephron toward sodium. This increases urine volume while reducing blood volume and pressure.

List the body fluid compartments and their approximate volumes and ion composition for an adult female

• total body water = 50

• intracellular fluid = 35

• plasma = 5

• extracellular fluid interstitial = 10

• total = 15

intracellular fluid has a high concentration of ions, such as potassium, magnesium, phosphate, and sulphate than extracellular. Lower concentration of sodium, calcium, chloride, and HCO3- than extracellular. Alsho has higher protein concentration.

Describe homeostatic regulation of blood volume and its effects on urine volume and concentration.

When blood volume is outside of normal range, ADH release is increased or decreased, this affects water reabsorption, which effects blood volume and blood pressure.

What is skeletal muscle?

• striated

• involved in movement

• voluntarily control

• motor neurons send electrical signals to muscle through neuromuscular junction that causes contraction

• specialized proteins within the muscle are stimulated to utilize the energy in ATP to slide past one another, producing force

What is smooth muscle?

• surrounds digestive organs and blood vessels

• involuntarily contracts

• spindle shaped, one nucleus

• not striated

What is cardiac muscle?

• involuntary and regulate by hormones and nervous system

• cells are electrically connected by junctions, allowing muscles to contract together as a unit for effective pumping

• long, striated

• one nucleus

• intercalated disks

What is a motor unit?

• consists of a single motor neuron and all the muscle fibres it innervates

• an AP in neuron of a motor unit causes contraction of all the muscle fibers in that unit

• motor units in different muscles contain different number of muscle fibres to regulate output strength, e.g. you have smaller motor units in your eyes, compared to your legs

Differentiate between slow and fast-twitch muscle fibers

• slow-twitch (type I):

  • contract slower

  • better-developed blood supply

  • more mitochondria

  • more fatigue resistant (breaks down ATP slowly)

  • contains large amounts of myoglobin

• fast-twitch (type II):

  • have myosin heads with a fast form of the enzyme that breaks down ATP, which allows their cross-bridges to release and form more rapidly

  • less well-developed blood supply

  • little myoglobin and mitochondria

  • large deposits of glycogen

  • well adapted to produce small amounts of ATP quickly without O2

  • comes in two forms: type II (rely on ATP production with and without ATP) and type Ix (rely exclusively on ATP production without O2)

How does exercise adapt muscles?

• increase size and capacity of both types of muscles fibres so that they perform more efficiently

• intense exercise that requires ATP production without O2 (e.g. weightlifting) increases mass of fast-twitch

• intense exercise in which ATP is produced with O2 (e.g long distance running) increases slow-twitch

• muscle size increase = hypertrophy

How does ATP production change as exercise progresses?

• at onset, small ATP reserve is quickly depleted

• direct production of ATP adenylate kinase and creatine kinase occurs, but this also rapidly deleted after ~15 seconds

• anaerobic respiration predominates

• fast-twitch muscle fibers break down glucose into intermediate lactate, which can be shuttled to adjacent slow-twitch to make ATP or be secreted into blood for uptake by other tissues to make new glucose

What are the functions of the digestive system?

1. ingestion and mastication

2. propulsion and mixing

3. digestion and secretion

4. absorption

5. elimination

What are the roles of the mucosal and submucosal layers?

• inner mucosal layer interacts with food bolus as it moves through the tract, it is designed to resist abrasion (esophagus) or secreted products to facilitate digestion (stomach, small intestine) and absorption (small intestine)

• submucosal layer contains connective tissue that surrounds nerves and blood vessels, this layer houses important components that control rate of digestion in response to presence of different food products

How does swallowing occur?

• skeletal muscles in tongue form a bolus of food and push it against roof of mouth and onto back of mouth

• bolus of food contacting back of mouth stimulates the reflexive closure of the larynx by the epiglottis and contraction of the pharyngeal constrictor muscles

• as food moves down esophagus, there is a wave of relaxation that precedes the bolus and a wave of contraction that follows the bolus of food, squeezing it through the esophagus into the stomach

What does the stomach secrete?

1. hydrochloric acid - proceeds ~2.0 pH in stomach, acid kills microorganisms and activates pepsin

2. pepsin - breaks covalent bonds of proteins to form smaller peptide chains

3. mucus - lubricates epithelial cells of stomach wall and protects them from the damaging effect of acidic chyme and pepsin

4. intrinsic factor - binds with vitamin B12 and makes it more readily absorbed in small intestine

What are the regions of the stomach?

• the esophagus opens into the cardiac part

• left of the cardiac part is the fundus

• largest part is the body

• the body narrows to form the pyloric part which ones into the small intestine

How are stomach secretions regulated?

1. cephalic phase - controlled by CNS, begins before bolus enters stomach, neruons