Physiology Quiz on ECG and Nervous System

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does the P wave in an ECG represent?

Atrial repolarization

Ventricular depolarization

Ventricular repolarization

Atrial depolarization (correct)

What causes the delay in conduction at the AV node?

Large QRS complex

Small diameter of fibers (correct)

Presence of gap junctions

Rapid propagation of action potentials

Which ECG component is associated with ventricular contraction?

QRS complex (correct)

P wave

T wave

ST segment

What occurs simultaneously with atrial depolarization but is not visible in the ECG?

Atrial repolarization Signup and view all the answers

What does the T wave in an ECG indicate?

Ventricular repolarization Signup and view all the answers

What is the main mechanism through which water gain is regulated in the body?

Thirst mechanism Signup and view all the answers

Which type of water loss accounts for the greatest volume per day?

Urine Signup and view all the answers

Which hormone is also known as antidiuretic hormone (ADH)?

Vasopressin Signup and view all the answers

What is the primary role of the autonomic nervous system?

Regulating involuntary body functions Signup and view all the answers

Which division of the autonomic nervous system is responsible for the body's 'fight or flight' response?

Sympathetic division Signup and view all the answers

What component is NOT part of the peripheral nervous system?

Spinal cord Signup and view all the answers

Which type of afferent carries information we are conscious of?

Somatic afferents Signup and view all the answers

What is a key function of the hypothalamus in relation to the autonomic nervous system?

Controlling involuntary functions Signup and view all the answers

How is water loss through urine quantitatively described in daily terms?

Typically all remaining water Signup and view all the answers

What is the main factor that affects osmotic pressure in a solution?

The total number of dissolved particles Signup and view all the answers

Which statement about osmolarity and osmolality is true?

Osmolality is affected by temperature variations. Signup and view all the answers

If a cell's intracellular fluid (ICF) has an osmolarity of 290 mOsm/L, what will happen if it's placed in a solution with an osmolarity of 250 mOsm/L?

Water will move into the cell, causing it to swell. Signup and view all the answers

What is the normal osmolarity of body fluids?

290 mOsm/L Signup and view all the answers

How many osmoles are formed from 1 mole of CaCl2 in a solution?

3 osmoles Signup and view all the answers

What is the phenomenon called when water moves across a selectively permeable membrane?

Osmosis Signup and view all the answers

What happens to the osmotic concentration when a compound completely dissociates in solution?

It increases based on the number of particles formed. Signup and view all the answers

What type of muscles does the autonomic nervous system (ANS) innervate?

Smooth muscles and cardiac muscles Signup and view all the answers

Which structure is identified as the main integrative center of autonomic nervous system activity?

Hypothalamus Signup and view all the answers

What distinguishes the somatic nervous system from the autonomic nervous system?

SNS is voluntary, while ANS is involuntary. Signup and view all the answers

How many pairs of spinal nerves are present in the human body?

31 pairs Signup and view all the answers

In an autonomic nerve pathway, where is the cell body of the first neuron found?

In the spinal cord or brain Signup and view all the answers

Which of the following functions is NOT directly regulated by the autonomic nervous system?

Skeletal muscle contraction Signup and view all the answers

What regulates the activities of the autonomic nervous system?

Centers in the CNS including the hypothalamus Signup and view all the answers

The efferent division from the central nervous system is responsible for which type of communication?

Motor output to the muscles and glands Signup and view all the answers

What is the role of autonomic afferents in the nervous system?

They send subconscious information about internal organs. Signup and view all the answers

Which of the following best describes the two-neuron chain in the autonomic nervous system?

Involves two neurons, preganglionic and postganglionic Signup and view all the answers

What region of the spinal cord do sympathetic neurons typically originate from?

Thoracolumbar region Signup and view all the answers

Which cranial nerve accounts for approximately 90% of all parasympathetic fibers?

Cranial nerve X Signup and view all the answers

Which of the following statements is true about the autonomic nervous system (ANS) compared to the somatic nervous system (SNS)?

The ANS includes both myelinated and unmyelinated fibers. Signup and view all the answers

What type of effector organs does the autonomic nervous system innervate?

Cardiac muscles and glands Signup and view all the answers

Which of the following characteristics differentiates the sympathetic nervous system from the parasympathetic nervous system?

Functions primarily during stress or emergencies Signup and view all the answers

In terms of myelination, how do the neurons of the somatic nervous system typically differ from those of the autonomic nervous system?

Autonomic neurons are typically unmyelinated compared to somatic Signup and view all the answers

Which of the following pairs of functions correctly matches the divisions of the autonomic nervous system?

Sympathetic - fight or flight Signup and view all the answers

What are the two divisions of the autonomic nervous system primarily known for?

Craniosacral and thoracolumbar Signup and view all the answers

Which of the following organs is mainly influenced by the parasympathetic nervous system?

Digestive organs Signup and view all the answers

How many neurons are typically involved in the pathway of autonomic nervous system signaling?

Two neurons Signup and view all the answers

Study Notes

L1: Homeostasis

Homeostasis is the maintenance of a steady state in the body's internal environment despite changes in the external environment.
Maintaining a stable internal environment is crucial for bodily functions and survival.
Homeostatic mechanisms minimize disturbances to the internal environment.
Equilibrium (balance) is the key concept involved in homeostasis.
Internal environment refers to the fluid that surrounds cells and aids in sustaining life-sustaining exchanges. Extracellular fluid is mainly involved.

Introduction

Anatomy is the study of body structures and their relationships.
Physiology is the study of body functions, including homeostasis.
Pathophysiology studies how physiological processes change in diseases or injuries.

Levels of Organization in the Body

Chemical: Atoms and molecules make up the body.
Cellular: Cells are made of molecules.
Tissue: Consists of similar types of cells.
Organ: Made up of different types of tissues.
Organ system: Multiple organs working together.
Organism: Made up of organ systems.

Concepts of Homeostasis

Homeostasis—a dynamic state.
Based on Greek words: Homeo (unchanging), and Stasis (standing).
Maintains internal factors within narrow limits, despite changes to the environment.

Homeostasis and Body Fluids

Intracellular fluid (ICF): Fluid inside cells.
Extracellular fluid (ECF): Fluid outside cells—two major components
Interstitial fluid: ECF found between cells.
Plasma: ECF within blood vessels.
ECF also encompasses cerebrospinal fluid, lymphatic fluid, synovial fluid, and fluid in the eyes (aqueous and vitreous).
Body cells function best with the correct volume of ECF, blood pressure, concentrations of O2, CO2, nutrients, waste products, electrolytes and pH.

Homeostatically regulated factors

Concentration of nutrients
Concentration of O2 and CO2
Concentration of waste products
pH
Concentrations of water, salt, and other electrolytes
Concentration of hormones
Volume and pressure
Temperature
Many other chemicals

Examples of constancy of the internal environment

Body core temperature: 37°C
Blood pressure: 120/80 mmHg
Arterial Blood: PaO2 100 mmHg; PaCO2 40 mmHg
Blood sugar (glucose): 100 mg/dL (5 mmol/L).
Electrolytes: Na+ = 140 mmol/L, K+ = 4 mmol/L
pH: Blood pH = 7.4, stomach pH = 2-4, small intestinal pH = 8, and urine pH = 6.

Control of Homeostasis

Homeostasis is continually disturbed by:
Physical insults from the external environment (e.g., extreme heat or lack of oxygen).
Changes in the internal environment (e.g., blood glucose levels).
Psychological stress.
In most cases, disruption of homeostasis is mild and temporary, and body cells quickly restore balance.
In some cases, the disruption of homeostasis is intense and prolonged, leading to disease or death.

Homeostasis is maintained by feedback mechanisms

A feedback system (loop): A cycle consisting of events.
The body continually monitors, evaluates and changes the state of the body.
The output of a system feeds back to either reverse or strengthen the effects.
Key components include Receptors, Control Center, and Effectors.
The set point: The normal range of the controlled variable.

Components of a feedback system

Receptor (sensor): Monitors changes in a controlled condition and sends the input to the control center.
Control center (integrating center): Evaluates the input from the receptors and compares it to the set point. Generates the output command.

Effector: Receives the output from the control center and produces a response to bring the controlled condition (variable) back to the set point.

Interactions among the components of a homeostatic control system

Stimulus: produces a change in a variable.
Receptor: detects the change.
Input: information sent from receptor to control center.
Control center: evaluates input and sends output.
Output: information sent from the control center to the effector.
Response of the effector: change in the variable
Balance/Homeostasis: return to normal state.

Types of feedback systems

Negative feedback system: Opposes an initial change to stabilize the system (e.g., BP, body temperature control).
Positive feedback system: Amplifies an initial change (e.g., childbirth).

Homeostatic regulation of blood pressure

Stimulus : High or low blood pressure
Receptors : Baroreceptors in certain blood vessels
Control Center : Brain
Effectors : Heart, Blood vessels
Response : Adjustments to heart rate and blood vessel dilation/constriction

Homeostatic regulation of breathing

Stimulus : Increase in arterial CO₂ or decrease in arterial O₂.
Receptors : Peripheral chemoreceptors in aortic and carotid bodies
Control Centre : Brain stem
Effectors : Respiratory muscles
Outcome : Decrease in arterial CO₂, or increase in arterial O₂.

Homeostatic regulation of blood glucose

Blood sugar high: Release of insulin → Body cells take in glucose → long-term storage in the liver (glycogen).
Blood sugar low: Release of glucagon → Liver converts glycogen into glucose → Released into the blood.

Homeostatic regulation of body temperature

Hypothalamus detects blood temperature
Higher than set point: blood vessels dilate, sweating occurs
Lower than set point: blood vessels constrict, shivering occurs
Body maintains itself between 36-38º C

Control of labor contractions during childbirth

Stimulus: Stretch of the uterus
Receptors: Stretch receptors (cervix),
Control center: Brain,
Effector: Uterine muscles

Feedforward

Feedforward or anticipatory control mechanisms permit the body to predict a change in a regulated variable out of its normal range and initiate a response that can reduce the degree of deviation.
Examples include; Eating increasing insulin secretion before glucose enters circulation, reduces large increase in blood glucose and Anticipatory increases in breathing frequency.

Disruptions in homeostasis

Imbalance occurs when the fine control of a variable falls outside the normal range.
Mild imbalances lead to disorders or diseases.
Severe imbalances can cause death.

Body Fluid Compartments and Fluid Balance

The body contains fluid compartments separated by membranes with selective permeability.
ICF- found inside the cell
ECF- divided into plasma and interstitial fluid. Both ECF and ICF have similar ion composition but different concentrations of proteins.
There are also minor fluid compartments like cerebrospinal fluid, intraocular fluid etc
The percentage of body water varies between individuals; Women have lower water content than men.
The percentage of body water progressively decreases with age.
Various factors determine the distribution of body water into the different compartments.

Minor ECF Compartments

Lymph: The fluid being returned from interstitial fluid to plasma.
Blood flows through lymph nodes for immune defense purposes
Transcellular fluid: Specialized volumes (e.g., synovial fluid, cerebrospinal fluid, intraocular fluid).

Plasma and interstitial fluid

Plasma and interstitial fluid have similar compositions. However, plasma contains notable amounts of proteins that are not found in significant amounts in the interstitial fluid

How fluid moves between different body compartments

Membrane allows water and particles to move between side 1 and side 2 (permeable to both)

Water and solute move until concentrations are equal on both sides.
Dynamic equilibrium occurs, thus the volume on neither side will change.

Membrane allows only water to move between side 1 and side 2 (not permeable to particles)

Water moves from side with high water concentration to side with low water concentration, which is called osmosis..
This movement is controlled by opposing hydrostatic pressure and osmotic pressure.
Osmotic pressure is the amount of pressure needed to stop osmosis.

Osmolarity/osmolality

Osmolarity: Concentration of osmotically active particles per volume of solution, typically in milliosmol/ liter.
Osmolality: osmotically active particles per unit mass of solvent, typically in milliosmol/ kilogram.

Osmosis and Osmotic Concentrations

Osmosis: Net diffusion of water across a selectively permeable membrane. Higher osmolarity pulls water in solution.
Osmotic concentration Proportional to the number of osmotic particles in solution.

Osmolarity

Osmolarity is proportional to the number of osmotic particles per molecule formed when the molecule dissolves.
Osmolarity is typically expressed in mOsm/L(milliosmoles/liter).

Semi permeable membrane separate body fluids into compartments

Tonicity

Tonicity describes the effect that a solution has on cell volume when the solution surrounds the cell.
Hypertonic: A solution with a high osmolarity compared to another solution causes cells to shrink, and loss of water from cells
Hypotonic: A solution with a low osmolarity compared to another solution causes cells to swell, and gain of water into cells.
Isotonic: A solution with the same osmolarity as another solution. This means water moves into and out of cells, but the volume does not change.

Water intoxication

Overhydration, hypotonicity, and cellular swelling can result from excess free water retention within short times.
Marked decrease in extracellular fluid osmolarity and concentration of sodium (hyponatremia).
Consequences: convulsions, coma, and possible death.

Water movement across the plasma membrane

Water can pass through the plasma membrane by either:

Integral membrane proteins (aquaporins).
Through the lipid bilayer via simple diffusion.

Water movement between capillaries and Interstitial fluid

Hydrostatic pressure is higher at the arteriolar end of capillaries.
Oncotic pressure remains the same.
Excess fluid is returned to circulation by lymphatics.

Imbalanced fluid movements

Increased capillary blood pressure (excessive filtration) and reduced reabsorption results in edema.
Reduced concentrations of plasma proteins (decreased colloid osmotic pressure) reduces reabsorption, resulting in edema.

Daily Water gain and Loss

Sources of water gain: ingested foods, ingested fluids, metabolic water and other factors.
Sources of water loss: GI tract, lungs, skin and kidneys.

Water steady state (water balance)

Amount ingested = amount eliminated.
Sources of water gain: metabolism (200-300 ml), intake (foods and drinks from environment- 2.2 liters/day)
Sources of water loss: insensible water (skin and lungs), urine output and fluid loss from feces
Rate of water balance is determined either via osmosis or other factors.

Regulation of body water loss

Kidney (lecture 13).

L3: Autonomic Nervous System

The autonomic nervous system is a part of the peripheral nervous system that regulates involuntary bodily activities.
It is critical for homeostasis in that it has a significant control over heart rate, blood pressure, digestion, secretion, and body temperature.
Comprised of three divisions; sympathetic, parasympathetic, and enteric nervous systems are described to provide a framework from the function and interactions of the three nervous systems.
The central nervous system contains the centers for coordinating activity of the nervous system.
Afferent division receives input from the CNS while Efferent division sends instructions from the CNS to the effector organs.

General organization of the nervous system

Central nervous system (CNS), and Peripheral nervous system (PNS)
Afferent and Efferent nervous system (Input to CNS and Output from CNS, respectively).
Somatic, Autonomic and Enteric nervous systems are described with the locations, neurons, and effector organs for each.

Organization of the peripheral nervous system

Sensory or afferent: transmit signals from the sensory receptors to the CNS. Two sensory afferents; somatic (from skin, skeletal muscle etc), visceral (from internal cavities such as stomach, bladder etc.)
motor or efferent: transmit signals from CNS to effector organs. Two motor or efferent; somatic (transmit signals to skeletal muscles). Autonomic (transmit to smooth and cardiac muscles, and glands).

Autonomic Nervous System (ANS)

Involuntary system regulating body activities.
Controls visceral functions (e.g., heart rate, blood pressure, digestion).
Comprised of motor neurons that innervate smooth and cardiac muscles and glands.
Organized into three divisions (sympathetic, parasympathetic, and enteric).

An autonomic nerve pathway

Consists of two neurons: preganglionic and postganglionic neurons.
Pre-ganglionic neuron: transmits nerve impulses from the CNS to the autonomic ganglion.
Post-ganglionic neurons: transmits nerve impulses from the autonomic ganglion to the effector organ

Comparison between autonomic and somatic nervous systems

Three ways to compare: location of cell bodies, myelination and number of cells involved and effector organs.
Autonomic nervous system is a two-neuron chain, whereas somatic is a single neuron.
Autonomic is considered visceral/ involuntary response, whereas somatic is voluntary response.
Effectors differ; Somatic nervous system affects skeletal muscles, while the autonomic affects smooth/cardiac muscles and glands.

Anatomical differences between sympathetic and parasympathetic ANS divisions

ANS Neurotransmitters

Sympathetic and parasympathetic neurons: release acetylcholine (ACh), which binds to nicotinic receptors.

Sympathetic nerves to adrenal medulla → adrenaline release to circulation.
Postganglionic neurons: release norepinephrine (noradrenaline) – adrenergic receptors.
Sweat glands → release ACh → muscarinic receptors.
All parasympathetic postganglionic neurons: release ACh Muscarinic receptors Two subtype: n and m

Physiological characteristics of ANS

Sympathetic dominance ("fight or flight"): Mobilizes energy, increases heart rate and respiration, and inhibits digestion and elimination.
Parasympathetic dominance ("rest and digest"): Conserves energy, decreases heart and respiration rates, and promotes digestion and elimination

Physiological characteristic of ANS - further details

Fight-or-flight response: increased production of ATP, dilation of pupils, increase heart rate & blood pressure; airway dilation, increase blood supply to skeletal muscles, cardiac muscle, liver, and adipose tissue; increase glycogenolysis, lipolysis.

Physiological characteristic of ANS - further details - parasympathetic dominance

Localized versus diffuse effects

Parasympathetic division → short-lived, localized control over effectors (ACh quickly destroyed by acetylcholinesterase)
Sympathetic division → longer-lasting, body-wide effects (norepinephrine and epinephrine circulate in blood and taken up and degraded over time by the liver).

Properties of the cardiac muscle

Autorhythmicity: The ability to initiate a heart beat continuously without external stimulation.
Conductivity: The ability to conduct excitation through the cardiac tissue
Excitability: The ability to respond to a stimulus of adequate strength and duration (i.e. threshold or more) by generating a propagated action potential
Contractility: The ability to contract in response to stimulation.

Autorhythmicity and the conduction system

The heart's ability to initiate and maintain its rhythmic contractions without external nervous system input.
Myogenic; due to presence of specialized excitatory and conductive system within the heart.
Two specialized types of cardiac muscle cells; contractile cells and autorhythmic cells.

The cardiac muscle

Contractile cells ~ 99% of cardiac muscle cells responsible for contraction.
Autorhythmic cells ~ 1% of cardiac muscle cells responsible for generating and conducting the rhythmic action potentials that coordinate contraction of working cells.

Locations of autorhythmic cells

Pacemaker potentials in autorhythmic fibers

Autorhythmic cells Lack a stable resting membrane potential, and repeatedly depolarize to threshold spontaneously.
Pacemaker potential: Spontaneous depolarization leading to action potential.
SA node: Fastest autorhythmic fibers, setting the rhythm of the heart.

Why sinoatrial node is a pacemaker

SA node's rapid spontaneous depolarization.
The slow pace making of other autorhythmic areas.

Heart rate and the autonomic influences on SA node

Increased sympathetic activity:
Increased rate of spontaneous depolarization in SA and AV nodes • Elevated Ca2+ and Na+ inflow through channels

Heart rate and the autonomic influences on SA node- parasympathetic

Conduction

Involves electrical excitation passing through the specialized cardiac tissue.

Spread of cardiac excitation

Impulses originate in the SA node and spread through the atria.
AV node delays the impulse to allow complete atrial contraction before ventricular contraction.
Impulse spreads rapidly through the ventricles via the bundle of His and Purkinje fibers.

Electrocardiogram (ECG)

An ECG is a record of the electrical activity of the heart.
By comparing tracings from different leads with normal records, you can determine if the conducting pathway is abnormal or if the heart is enlarged or if certain regions are damaged.
The ECG shows the electrical changes occurring throughout the heart cycle, with several deflections: • P wave - atrial depolarization • QRS complex - ventricular depolarization • T wave - ventricular repolarization

Spread of cardiac excitation

Cardiac impulse begins in the SA node
Propagates through the atria; AV node (delay)
Enters the ventricles through the AV bundle.
Travels to the apex of the heart.
Depolarisation spreads upwards through the ventricles.

Ventricular muscle action potential

Depolarisation; Ca2+ inflow while K+ outflow slows, maintaining depolarization (plateau).
Repolarisation: Ca2+ channels close and K+ channels open causing repolarisation.
This plateau and refractory period are crucial to preventing tetanus in cardiac muscle.

Cardiac muscle has long refractory periods

Refractory periods during contraction ensure the heart can completely relax between contractions to allow the heart to fill with blood effectively before the next contraction.
Longer refractory period prevents tetanus in cardiac muscle.

Cardiac muscle is excited by action potential

Cardiac muscle fibers are excited by action potentials.
Calcium enters the muscle, causing contraction.

Summary

Normal function of the specialized excitatory and conductive system of the heart results in atria contract before ventricles, allow filling of ventricles, all portions contract simultaneously, and efficient pressure generation.

Introduction to cardiac cycle and cardiac output

The cardiac cycle consists of alternate systole and diastole.
Systole→ contraction and emptying
Diastole → relaxation and filling
Atrial & ventricle goes through different cycles of systole and diastole.

Important terminologies

Venous return: Amount of blood returning to the heart per minute
End diastolic volume (EDV): volume of blood in the ventricles at the end of diastole.
Preload: degree of stretch on the heart before it contracts; directly proportional to the end-diastolic volume (EDV).
End systolic volume (ESV): volume of blood remaining in the ventricles at the end of systole.
Ejection fraction: fraction of EDV ejected
Afterload: Pressure that must be exceeded for ejection of blood from the ventricles.
Stroke volume: volume of blood pumped out of the ventricle every heartbeat (EDV-ESV)

Blood flow = AP/R

Cardiac output = mean arterial pressure/ total peripheral resistance.

Pressure gradient in the systemic circulation

The pressure gradient in the system blood circulation is the difference in pressure between the ascending (higher pressure) and descending (lower pressure) capillaries to create steady blood flow.
A positive pressure gradient is essential for blood flow.
Mean arterial pressure (MAP) is the average blood pressure in the arteries.

Mean arterial pressure

MAP can be estimated by the formula: diastolic BP + 1/3 pulse pressure
Important for driving blood through the body.
Dependent on cardiac output and resistance.

Most vascular resistance is in arterioles

2) Vascular resistance

Resistance is opposition to the flow of blood through a vessel.
Key factors determining resistance are blood vessel radius, blood viscosity, and total blood vessel length.

Factors determining vascular resistance - diameter

Resistance is inversely proportional to the fourth power of the radius (Resistance α 1/r⁴).
Smaller diameter, greater resistance.

Factors determining vascular resistance - blood viscosity

Viscosity is directly proportional to resistance. Higher viscosity, Greater resistance to blood flow.

Factors determining vascular resistance - vessel length

Resistance is directly proportional to the vessel's length. Longer vessel, Greater resistance.

Total peripheral resistance

Blood pressure

Pressure gradient in the systemic circulation

Mean arterial pressure

1) Blood pressure

Neural regulation of blood pressure

• Baroreceptors • Other reflexes • Chemical regulation of blood pressure (hormonal control)

Hormonal regulation of blood pressure

Several hormones affect blood pressure by altering cardiac output (CO), total peripheral resistance(TPR), or total blood volume. ▪ Epinephrine and norepinephrine: increase cardiac output, constrict blood vessels → increase TPR → increase blood pressure. ▪ Renin-angiotensin-aldosterone system (RAAS): increases sodium and water reabsorption in kidneys → increases blood volume → increases blood pressure. ▪ Antidiuretic hormone (ADH): Increases water reabsorption in kidneys, and constricts blood vessels→ increase TPR → increase blood pressure ▪ Atrial natriuretic peptide (ANP): decreases sodium and water reabsorption in kidneys → decreases blood volume→ decreases blood pressure.

1. Epinephrine and norepinephrine

Adrenal medulla release epinephrine and norepinephrine

2. Renin-angiotensin-aldosterone system (RAAS)

3. Antidiuretic hormone (ADH)

4. Atrial Natriuretic peptide (ANP)

Ventilation and breathing

The composition of atmospheric air does not change with altitude or in a hyperbaric environment.
Boyle's law describes the inverse relationship between the pressure and volume of gases. Volume and pressure changes allow air to enter or exit the lungs.

Muscles of inhalation & exhalation

Role of the medullary rhythmicity area

The pneumotaxic and apneustic area

The pneumotaxic area → inhibit the inspiratory area to control the rate and depth of breathing.
The apneustic area → stimulate the inspiratory area to prolong inspiration
Coordination of these areas result in normal breathing pattern.

Chemical Control of Respiration

Central chemoreceptors: Located bilaterally in the medulla, they are highly sensitive to H+ concentration and/or CO2 in cerebrospinal fluid (CSF).
Peripheral chemoreceptors → Located in aortic bodies and carotid bodies, they are sensitive to changes in Po₂, Pco₂, H+ in blood.

Role of increased arterial Pco₂ on ventilation

Role of increased arterial H+ on ventilation

Role of reduced arterial Po₂ on ventilation

Summary of influence of chemical factors on respiration

Other factors affecting respiration

Types of hypoxia

Blood flow through special circulations

• Cerebral circulation (brain) • Coronary circulation (heart) • Gastrointestinal (splanchnic) • Renal (kidneys) • Skeletal muscle • Cutaneous circulation (skin)

Cerebral circulation

Coronary circulation

Skeletal muscle blood flow

Gastrointestinal blood flow

Cutaneous circulation (skin)

Renal circulation

Transport across the capillary wall

Continuous capillaries, fenestrated capillaries, and sinusoidal capillaries.

Forces influencing bulk flow across the capillary wall

Glomerular blood hydrostatic pressure (GBHP), Blood colloid osmotic pressure (BCOP), and Capsular hydrostatic pressure (CHP)|
Net filtration pressure: difference between forces favoring filtration and forces opposing filtration

Glomerular filtration rate (GFR)

Adjustment of glomerular filtration rate (GFR)

• Renal autoregulation (myogenic and tubuloglomerular feedback) • Neural regulation • Hormonal regulation

Renal autoregulation by myogenic mechanisms

Renal autoregulation by tubuloglomerular feedback

Neural regulation of GFR

Hormonal regulation of GFR

Atrial natriuretic peptide (ANP): Released when blood volume and pressure increases, acts on arteriol, and decreases pressure, thereby increasing GFR.
Angiotensin II: Released when blood volume and pressure decreases, causes constriction of the efferent arteriole, which maintains or increases GFR despite low blood pressure.

Basic functions of the nephron

Glomerular Filtration (GF): Water and most solutes in blood move across the capillary walls.
Tubular reabsorption (TR): Useful solutes and water are reabsorbed from the filtrate.
Tubular secretion (TS): Removes substances from the blood into the filtrate.

Tubule segments (summary)

Proximal tubule

Loop of Henle

Distal convoluted tubule (DCT)

Collecting ducts

Principles of tubular reabsorption

Steps of transepithelial transport

Transport mechanisms

Interplay between active and passive transport

Summary of contents filtered, reabsorbed, and excreted in urine

Hormonal regulation of tubular reabsorption and tubular Secretion

Renin-angiotensin-aldosterone axis

Kidney secretion of renin → activation of hormones to regulate sodium and water reabsorption, thereby maintaining blood pressure
Results in activation of other hormones (ADH, ANP) in the end to maintain homeostasis.

Antidiuretic hormone (ADH, Vasopressin)

Released from the posterior pituitary.
Involved in regulating facultative water reabsorption in the kidneys.
Osmolality increases, or blood volume decreases to induce ADH secretion
Increases water reabsorption = decreases urine output.

The natriuretic peptides

Released from the atria of the heart when stretched.
Stimulate sodium and water excretion in the urine..
Antagonistic to the renin-angiotensin-aldosterone system.
Causes vasodilation of afferent arterioles and constriction of efferent arterioles thereby promoting GFR.

L16: Acid base balance

Acid-Base Imbalances

Respiratory acidosis and alkalosis

Metabolic acidosis

Metabolic Alkalosis

Biological (chemical) buffers

Respiratory mechanism

Renal mechanism

pH regulation by respiratory compensation

Summary of the influence of chemical factors on respiration