Physiology Final Cumulative Objectives

Describe the fluid compartments of the body and know their relative sizes in comparison to one another

Intracellular fluid > Interstitial fluid > Plasma

Define homeostasis and describe the meaning of “dynamic equilibrium”

Homeostasis - a “dynamic equilibrium” where levels change over short periods of time, but remain relatively constant over long periods of time near the “set point”

Know the components of a homeostatic reflex arc

Afferent pathway - carry receptor info to control center

Efferent pathway - carry command from control center to effector

How do negative feedback loops preserve homeostasis?

Production of a substance inhibits further production of that substance » return fluctuations in levels to their set point

Define active transport, secondary active transport, and facilitated diffusion. Think of some examples in specific body systems.

• Facilitated diffusion - uses a permeable barrier where flow is down a concentration gradient (ex. sodium flows out of the descending limb)

• Active transport - uses energy to transport against a concentration gradient (ex. Na+/K+ pump)

• Secondary active transport - uses energy from a pre-existing gradient of a different solute to transport against the gradient

Know the three membrane junctions and their functions

1. Gap junctions - allow ions and other molecules to pass

2. Tight junctions - form a barrier

3. Desmosomes - strong attachment

Describe how size and solubility determine whether a substance can cross a membrane by diffusing through the lipid bilayer, or whether it needs to pass through a transport protein

Pass by diffusion » small and nonpolar molecules

Pass by transport protein » ions and water-soluble, larger molecules

Define hyper-, hypo-, and isotonic. Explain how these solutions affect the movement of water across membranes and describe the effect on cell size

Hypertonic - water moves out of cell » crenation/shrivel

Isotonic - water moves in and out of cell » no change

Hypotonic - water moves into cell » lysis/burst

Describe the ligand gated ion channel and how it transduces signals in the cell

• agonist binds and opens channel

• changes membrane potential

  • + ions IN » depolarize cell

  • - ions IN » hyperpolarize cell

  • + ions OUT » hyperpolarize cell

• Ex. nicotinic ACh receptor

Describe the enzyme linked receptor and how it transduces signals in the cell

• receptor that has enzyme activity and phosphorylates target proteins in the cell (kinases)

• Ex. Insulin receptor

Describe the JAK/STAT receptor and how it transduces signals in the cell

• receptor activates janus kinase (JAK) that phosphorylates proteins (STAT)

• STAT proteins often travel to nucleus as transcription factors

• Ex. cytokine receptors

Describe the GCPR and how it transduces signals in the cell

• G protein located on membrane surface with 3 subunits

• Alpha subunit binds GTP and dissociates from beta/gamma subunit

• Alpha subunit activates second messenger molecules

  • Gs - stimulate adenylyl cyclase » more cAMP

  • Gi - inhibits adenylyl cyclase » less cAMP

  • Gq - activates phospholipase C » increase IP3, DAG, and Ca2+

Describe how second messengers like cAMP lead to signal amplification

A first messenger activates a second messenger like cAMP that creates a signal cascade by phosphorylating 100s of enzymes, which then phosphorylate 100s more enzymes » signal amplification

How is resting membrane potential maintained?

Na+ is higher concentration outside of cell » Na+ wants to flow in

K+ is higher concentration inside of cell » K+ wants to flow out

maintained by an electrochemical gradient of both ions

explain how an action potential is generated and how voltage gated Na+ and K+ channels are involved

1. At rest » Na+ and K+ closed

2. Stimulus » Na+ open and flows into cell

3. Peak depolarization » Na+ channel deactivates, K+ open and flows out of cell

4. Voltage falls to hyperpolarization » K+ close, Na+ are resting closed

Describe absolute and relative refractory periods

Absolute - cell is incapable of depolarizing

Relative - cell can depolarize if supplied with a stronger than usual stimulus

helps maintain signals as individuals

Describe how action potentials propagate and how propagation is affected by axon diameter and myelination

Larger diameter and thicker myelination » faster propagation

• Resting membrane is depolarized to threshold by local current of AP

• Once AP propagates down axon, membrane behind AP is refractory and cannot stimulate a second AP

What is the link between Ca2+ and neurotransmitter release?

AP triggers Ca2+ channels to open and flow into axon terminal » Ca2+ in terminal facilitates vesicles fusing into cleft and release NT into synaptic cleft

Define EPSP and IPSP and how they’re different from AP

Excitatory Postsynaptic Potentials (EPSP) - depolarize membrane towards threshold

Inhibitory Postsynaptic Potentials (IPSP) - hyperpolarize membrane away from threshold

can summate into an AP or away from an AP

What are the neurotransmitters and receptors involved in signaling for the sympathetic nervous system?

NE and Epi » Alpha and Beta andregenic receptors

What are the neurotransmitters and receptors involved in signaling for the parasympathetic nervous system?

ACh » Muscarinic receptors

Define the concept of autonomic tone

One division is dominant (SNS or PSNS)

Ex. heart rate has PSNS tone, so resting heart rate is 70 bpm rather than 100 bpm

Define receptor potential and describe how receptor potentials can lead to the generation of an AP in a sensory neuron

Local changes in potential in response to stimuli (stronger stimuli » larger potential)

Summation can lead to an AP

Define adaptation, why it’s important, and why a neuron may be slow or quick adapting

Rapid adaptor - (ex. light touch to skin) quickly adapts to stop firing even with a simuli, when stimulus is removed, we notice removal

Slow adaptor - (ex. more important stimuli) that fires AP as long as the stimulation is present

Describe similarities between the three muscle types: shape/size, striation, and voluntary/involuntary

How does signal travel from a motor neuron to a skeletal muscle fiber? Once it reaches the fiber, how does it cause contraction?

AP arrives to neuromuscular junction » ACh is released and triggers AP in T-Tubules » Ca2+ is released from SR and binds to troponin, moving off of actin binding sites » myosin head binds to binding site and causes a power stroke » muscle contracts

Why does rigor mortis develop after death?

ATP is depleted » muscles cannot relax » body stiffens

Describe the frequency tension relationship in muscles and how it leads to generation of prolonged muscle tension

• Depolarizing muscle with frequent stimuli generates more tension than one twitch

• Successive AP summation » increased muscle tension

• Tetanus - maintained contraction

Describe the length tension relationship

• There is an optimal amount of stretch that allows a maximum tension in muscle fiber

• Over or under stretched muscles are weaker

• Due to overlap of filaments » FRANK STARLING MECHANISM

Describe the process of smooth muscle contraction involving myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP)

• MLCK stays active as long as Ca2+ is present

• MLCP is always active

• When MLCK activity is less than MLCP » smooth muscle relaxes

• Smooth muscle can stay contracted (latch state) if Ca2+ remains elevated in the cytosol

  • Increased Ca2+ = increased MLCK = increased cross bridge

List the chemical classes of hormones. What can we infer about a hormone’s mechanism of action based on its chemical class?

• Amines - derived from tyrosine

  • often GCPR

  • TH, Epi, NE, DA

• Peptides/proteins - large diverse molecules

  • RTK, GCPR, JAK/STAT

  • Angiotensin II, Insulin

  • Prepro delayed activation form

• Steroids - derived from cholesterol

  • act at nuclear receptors to alter gene activity

Define tropic and trophic

Topic - 1st hormone causes secretion of 2nd hormone

Trophic - 1st hormone stimulates growth of the gland that makes 2nd hormone

Describe how the hypothalamus regulates the release of pituitary hormones, and how this mechanism differs from the anterior to posterior pituitary gland.

Anterior: hypothalamus stimulates anterior pituitary to secrete “releasing hormones” which act on 3rd glands

Posterior: hypothalamus creates hormones which are stored in posterior pituitary

Explain how hormone release is regulated between the hypothalamus, pituitary and “third glands” including negative feedback

Hypothalamus » anterior pituitary » 3rd gland

Third gland secretes hormones that create a negative feedback loop

Describe the effects of cortisol on the body and what happens if there is too much or too little

CRH » ACTH » Cortisol

• EFFECTS:

  • Maintains BP through permissive action on smooth muscle catecholamine activity

  • maintains levels of metabolic enzymes

  • keeps immune system in check

  • increases alpha receptors » stronger catecholamine reaction

• Too much = Cushing’s syndrome » weight gain, high blood sugar, immune suppression

• Too little = Addison’s disease » fatigue, low blood sugar, weight loss and low BP

What are the effects of thyroid hormone?

• Metabolic activity

  • increase carb absorption

  • increased fatty acid release from adipose

  • increased Na/K ATPase activity

  • calorigenic

• GH long bone growth

• Permissive effect on fat mobilization in response to Epi

Describe how levels of TH and TSH are related

TSH increases T3/T4.
High T3/T4 = low TSH (negative feedback).
Low T3/T4 = high TSH.

What are the physiological effects of parathyroid hormone?

Low Ca2+ » secrete PTH » increase osteoclasts, absorb Ca2+ in intestine, decrease Ca2+ excretion in kidney

Trace the path of blood flow through the heart, including the chambers and valves

PULMONARY:

• Vena cava » RA » tricuspid » RV » pulmonary valve » pulmonary artery

SYSTEMIC:

• Pulmonary vein » LA » mitral » LV » aortic valve » aorta

Describe SA node, AV node, and other important structural components of the conduction system

• SA node - pacemaker, initiates electrical impulse » atrial contraction

• AV node - delays SA impulse so atrial contraction can finish before ventricular contraction, can act as SA backup if SA fails

• Bundle of His - moves impulses from AV to ventricles

• Purkinje fibers - carry impulse through the ventricles (apex to base)

Explain cardiac action potential and how it differs from the action potential in neurons and skeletal muscle

• unlike nerves and skeletal AP, cardiac AP has a long plateau

• longer AP » depolarization and contraction have the same duration » no tetanus » ventricles have time to fill with blood before being pumped

Identify and explain the significance of the P wave

atrial depolarization

Identify and explain the significance of the QRS complex

Ventricular depolarization

Identify and explain the significance of the T wave

ventricular repolarization

Identify and explain the significance of the P-R interval

AV node delay

Identify and explain the significance of the Q-T interval

duration of ventricular AP

Define cardiac output and how it is regulated by the ANS

• amount of blood pumped (L/min)

• CO = HR (bpm) x SV (mL)

  • SNS = higher HR and SV

  • PSNS = lower HR

Define heart rate and how it is regulated by the ANS

• measured in bpm

• PSNS - CN X, ACh, M receptors, Atria, lower HR

• SNS - thoracic spinal nerves, NE, beta receptors, Atria and ventricles, increase HR

Define stroke volume and how it is regulated by the ANS

• amount of blood ejected by one ventricle per heartbeat

• SNS - increases ejection fraction

  • NE and Epi bind to beta receptor » active cAMP » release Ca2+ » stronger contraction

Explain the significance of the Frank Starling mechanism and how it relates to actin and myosin filaments

*stretch = more efficient contraction*

more blood » more stretch » better alignment of actin-myosin filaments » more cross bridge » stronger contraction » higher SV

Explain how the baroreceptor reflex works to maintain mean arterial pressure (MAP)

• acts as a reflex arc

• MAP (homeostasis) » baroreceptors (receptor to disturbances) » medullary cardiovascular center (control center) » cardiac and smooth muscle (effector) return MAP to set point

Describe the key components that are necessary for the blood to form a clot

Injury » collagen exposed » platelets activate and aggregate » ADP and Thromboxane Az » vasoconstriction & plug forms

• Tissue factor » Factor Xa » Thrombin » converts fibrinogen to fibrin, creates factor XIII that stabilizes clot

Describe the four processes involved in respiration:

1. ventilation

2. gas transport

3. external respiration

4. internal respiration

Define ventilation

breathing

Define gas transport

movement of O2 and CO2 in blood

external respiration

lung O2 » blood

blood CO2 » lungs

Define internal respiration

blood O2 » tissue

cell O2 » blood

Explain how negative intrapleural pressure prevents the lungs from collapsing, and piercing of the chest wall can cause pneumothorax

• negative intrapleural pressure creates suction that holds lungs open

• if chest wall is pierced, air enters the pleural space » pressure equalizes » lung collapses

Explain the relationship between PO2 and hemoglobin saturation

increased PO2 » increased hemoglobin saturation

decreased PO2 » decreased hemoglobin saturation

Describe how hemoglobin saturation curve can shift based on pH, temperature, or 2,3-DPG

• ↓ pH (acidic), ↑ temperature, or ↑ 2,3-DPG → Right shift → ↓ O₂ affinity → more O₂ released to tissues

• ↑ pH (alkaline), ↓ temperature, or ↓ 2,3-DPG → Left shift → ↑ O₂ affinity → less O₂ released

List the ways that CO2 can be transported in blood

1. Carbonic acid (H2CO3) ~ 60%

2. Hb-bound in RBC ~ 30%

3. Dissolved in plasma ~ 10%

List the reaction that converts CO2 to carbonic acid

CO₂​ + H₂​O ↔ H_2​CO_3​ ↔ H⁺ + HCO₃^−​

Describe how chemoreceptors regulate respiration and explain why CO2 is usually the most important driver of ventilation

if CO2 increases » pH lowers (acidic) » fires on chemoreceptors » increases ventilation

Describe the structure of the nephron and the sites of filtration, secretion, and reabsorption

• Filtration: Glomerulus in Bowman's capsule

• Reabsorption: Mainly in proximal tubule, also in loop of Henle, distal tubule, and collecting duct

• Secretion: Proximal & distal tubules, collecting duct

What determines whether a substance is filtered? What determines whether a substance is secreted or reabsorbed?

• Filtered: Based on size and charge—small, unbound solutes (<~70 kDa) pass through the glomerular filtration barrier.

• Reabsorbed: Depends on transporters, concentration gradients, and body needs (e.g., glucose, Na⁺).

• Secreted: Requires active transporters; used to remove excess ions, drugs, or waste (e.g., H⁺, K⁺, creatinine).

Explain how sodium reabsorption, including the role of Lumen Na+ channels and Na+/K+ ATPase.

1. Diffuses from lumen into endothelial cells

2. Actively transported out of cell (Na+/K+ pump) on basolateral side into interstitial fluid to be reabsorbed

Specific channels and transporters on luminal side differ in different regions of the tubule, but pattern remains the same

What hormone increases Na+ reabsorption, and where in the nephron does it take effect?

• aldosterone

• distal tubule and collecting duct

Describe the function of vasopressin and the location where it acts within the nephron

• adds aquaporin channels to collecting duct » creates more concentrated urine

What happens when vasopressin levels are high or low?

High vasopressin » water is reabsorbed » concentrated urine

Low vasopressin » water remains in ducts » dilute urine

Explain the short and long term mechanisms for blood pressure regulation using the autonomic nervous system and renin-angiotensin system

Short-Term (Autonomic Nervous System):

• Sympathetic activation: ↑ heart rate (HR), contractility, and vasoconstriction → ↑ BP

• Parasympathetic activation: ↓ HR → ↓ BP

Long-Term (Renin-Angiotensin System):

1. Renin release (from kidneys) due to low BP, low Na⁺, or sympathetic activation

2. Angiotensin II:

   • Vasoconstriction → ↑ BP

   • Stimulates aldosterone secretion → Na⁺ reabsorption → ↑ blood volume → ↑ BP

   • Stimulates ADH release → water retention → ↑ blood volume → ↑ BP

Explain how the lungs and kidneys can alter the balance of CO2/bicarbonate in the body and how these processes would change in order to compensate for alkalosis or acidosis.

Metabolic » same

• Metabolic acidosis = (low pH) low HCO3, low CO2

• Metabolic alkalosis = (high pH) high HCO3, high CO2

Respiratory » opposite

• Respiratory acidosis = (low pH) high HCO3, high CO2

• Respiratory alkalosis = (high pH) low HCO3, low CO2

Describe the structure and function of the GI tract wall

1. Mucosa: Inner lining with epithelium (secretes enzymes, absorbs nutrients), lamina propria (supports), and muscularis mucosa (helps movement).

2. Submucosa: Connective tissue with blood vessels, lymphatics, and nerves (provides nutrients, regulates secretion).

3. Muscularis externa: Two layers of smooth muscle (circular and longitudinal) for peristalsis and segmentation.

4. Serosa (or adventitia): Outer connective tissue layer (protects and anchors organs)

Describe how the GI wall varies within the major organs of the digestive system

• Esophagus: Thick mucosa for protection against abrasion, mainly stratified squamous epithelium.

• Stomach: Mucosa has gastric glands for acid secretion, muscularis externa has oblique muscle for churning.

• Small intestine: Mucosa has villi and microvilli for nutrient absorption.

• Large intestine: Mucosa contains goblet cells for mucus production (lubrication).

Describe the digestive processes that occur in the stomach

• denaturation of proteins, making enzymes accessible

• peristalsis mixes and breaks up food

• not a lot of absorption

• Glands secretions

  • parietal cells » secrete HCl and intrinsic factors

  • chief cells » secrete pepsinogen

  • g cells » secrete gastrin » stimulates parietal cells

Explain function of gastrin and CCK

• gastrin - stimulates parietal cells » HCl

• CCK - increases pancreatic enzyme secretion for digestion

What are the roles of pancreatic enzymes and brush border enzymes in digestion?

• pancreatic enzymes - digest major molecule classes (carb, fat, protein, NA), activated in sm. intestine lumen

• brush border enzymes - produced by intestine epithelial cells and activate pancreatic enzymes to perform digestion

What steps would a starch molecule go through between ingestion and absorption?

1. Mouth - salivary amylase breaks down alpha bonds in starch; polysaccharides » monosaccharides

2. Stomach - peristaltic mixing of food breaks down

3. Pancreas - pancreatic amylase and brush border enzymes perform majority of absorption

4. Intestines - monosaccharides are absorbed

Describe the effects of insulin on its target cells

1. Increases glucose uptake into cells

2. Promotes glycogenesis in liver and muscle

3. Inhibits gluconeogenesis in liver

4. Stimulates lipogenesis to create adipose fat storage

5. Increases protein synthesis from AA

Describe the homeostatic feedback loop involved in body temperature regulation, including the major effector mechanisms for gaining or losing heat

• Stimulus: Body temp too high or too low

• Sensor: Thermoreceptors in skin & hypothalamus

• Control Center: Hypothalamus compares to 37°C set point

• Effectors:

  • To cool down:

    • Vasodilation (heat loss through skin)

    • Sweating (evaporative cooling)

  • To warm up:

    • Vasoconstriction (retain core heat)

    • Shivering (muscle heat generation)
      
      - Response: Temperature returns to normal → negative feedback stops the response