Physiology Test 2 - BU MAMS

Body Temperature

Internal core temperature, which is usually measured sublingually, rectally, or via the ear canal

3-6 am; 3-6 pm

Body temperature tends to vary approximately 1 degree Celsius throughout the day’ when is body temperature lowest? When is body temperature highest?

0.5

The stage of the menstrual cycle also results in variation of body temperature; how many degrees Celsius does it increase by?

Heat Loss Response

How does the body attempt to maintain normal body temperature when excess heat is generated through physical activity?

High SA to Mass Ratio, Limited Shiver/Sweat Response

Characteristics of newborns with regard to regulating their body temperature

Atrophy of Skeletal Muscle

Why do the elderly have reduced heat generating ability?

Reduced CVS Reserve, Sweat Gland Atrophy

Why do the elderly have reduced heat dissipating ability?

Homeotherms

Organisms that maintain internal temperature to sustain optimal reaction rates

72; 500

What is the metabolic rate at rest? How high can the metabolic rate rise during exercise? (kcal/hr)

Convection (Major); Conduction (Minor)

What are the two mechanisms through which core body heat flows to the skin?

Radiation, Conduction, Convection, Evaporation

Four main forms of heat transfer

Rate = Heat Transfer Coefficient x (Tskin-Tambient) x Surface Area

General formula for rate of heat loss (same formula for radiation & convection; evaporation uses vapor pressure difference instead of temperature)

Radiation

Form of heat transfer via electromagnetic (infrared) rays between skin and solid bodies in the environment, without contact

Conduction

Form of heat transfer between skin and a solid body via direct contact

Convection

Form of heat transfer between skin and the environment by a fluid (e.g., air, water)

Evaporation

Form of heat transfer between the skin and the environment via evaporation of liquid; heat loss/gain is independent of the temperature difference

1. Thermal Sensors

2. Afferent Pathways

3. Integration Center (Hypothalamus)

4. Efferent Pathways

5. Target Organs

Five components of the system used to regulate body temperature

Temperature Sensors

Specialized sensory neurons (free nerve endings) which are distributed over the entire skin surface of the body; also present in the core (e.g., preoptic area, anterior hypothalamus)

Warm, Cold

Two types of skin thermoreceptors, which help to alter the sensitivity of response to body core thermoreceptors

Face, Lips, Fingers

Example of areas that have fine temperature discrimination (acral skin)

Spinal Cord, Preoptic Area, Anterior Hypothalamus (10% of Neurons)

Where are body core thermoreceptors (warmth-sensitive neurons) found?

Cutaneous Circulation, Sweat Glands, Skeletal Muscle, BAT (Brown Adipose Tissue)

Four types of thermal effectors (which are different ways in which a thermoregulatory system mounts a response to heat or cold stress)

ANS

Through which “system” is the majority of cutaneous blood flow controlled?

Acetylcholine (ACh)

Although the secretory segment of the sweat gland is innervated by the sympathetic nervous system, which neurotransmitter is involved?

Flushing From Cooler Peripheral Circulation

What accounts for the slight initial drop in core temperature at the onset of exercise?

Prostaglandin (PGE2)

Which signaling molecules do pyrogens (released from immune cells) release, in turn, acting on the warmth-sensitive neurons in the preoptic area of the hypothalamus, inhibiting firing?

Heart, Blood Vessels, Blood

Parts of the CVS

Pulmonary (Low-Pressure), Systemic (High-Pressure)

The heart consists of two pumps in series; what are their names?

Capillaries

Where is the flow velocity lowest due to a large cross-sectional area?

Venules, Veins

Which two types of blood vessels are called capacitance vessels because they contain a large fraction of blood volume at low pressure? (More compliant/stretchable)

Compliance = DeltaV / DeltaP

Formula for compliance

Q (Flow) = DeltaP / R (Resistance)

Formula for flow (ml/sec, L/min)

Volume Flow = Flow / Cross-Sectional Area

Formula for volume flow (cm3/sec)

P = Force/Area = pgh

Formula for pressure (mmHg, cmH2O)

1.36 cm

How many centimeters of water are equal to 1 mmHg? We can use this conversion because the density of a given liquid is constant, as is g, so it is customary to use the height as a measure of P

ET = EP + EK + EG+ ER (Thermal Energy)

Formula for the total energy of the system

Flow = (DeltaP*pi*r^4)/(8*Viscocity*L)

Formula for Poiseuille’s Law

R = (8*Viscocity*L)/(pi*r^4)

Formula for resistance derived from Poiseuille’s Law

R1 + R2 + R3

How is resistance calculated in parallel?

1/R1 + 1/R2 + 1/R3

How is resistance calculated in series?

TPR = (PA - PRA) / CO

Formula for total peripheral resistance

PA = Mean aortic/arterial pressure

PRA = Right atrial pressure

CO = Cardiac output

Re = (pDv)/Viscocity

Formula for Reynolds number (Re): a critical dimensionless number that takes all the factors of the conversion of laminar flow to turbulent flow into consideration

55% Plasma, 45% Erythrocytes (Hematocrit), Buffy Coat (Leukocytes/Platelets)

What is the composition of blood?

760 mmHg

How many mmHg is in 1 atm?

Syncytium

What is the term for cells electrically coupled to each other by intercalated discs? Gap junctions allow action potentials to cause action potentials in downstream cells

Autorhythmicity

What property indicates that cardiac excitation is myogenic rather than neurogenic?

Contractile

Which types of cardiac myocytes make up the vast majority (>90%) of cardiac myoctes and must be stimulated to initiate contraction?

SA Node, Atrial Internodal Tracts, AV Node, Bundle of His, Purkinje Fibers

Where are electrical cardiac myocytes found?

Sinoatrial (SA) Node

Where does cardiac depolarization begin? (Pacemaker cells in this region)

Atrioventricular (AV) Node

Where in the heart is there slower conduction velocity to allow ventricles to fill with blood?

0. Rapid Depolarization

1. Initial Repolarization

2. Plateau

3. Rapid Repolarization

4. Diastolic Interval

Five phases for electrical activity of the heart

200-500 msec

How long do cardiac action potentials last? (In nerve/skeletal muscles, action potentials last a few milliseconds)

SA Node —> AV node —> His Bundle —> Bundle Branches —> Purkinje Fibers —> Ventricle

Pathway for conduction of action potentials (AP) starting from the SA node

Pacemaker Potential

Term for the slow depolarization occurring between discharges in “pacemaker cells”

TRUE

True or false? There is no change in the maximum diastolic potential regarding sympathetic stimulation effects on heart rate

TRUE

True or false? In vagal stimulation, the maximum diastolic potential is increased and the rate of rise of the pacemaker potential is decreased; together, they contribute to the slowing of the heart rate

L-Type Ca2+ Channels

What is responsible for the plateau phase for action potentials in atria and ventricles?

Current = Conductance * Driving Force

Formula for current

4, 0, 3

What are the three phases of the action potentials of the SA and AV node? (In order)

Phase 4

Which phase of action potentials in the SA/AV node is characterized by the following properties?

• Slow influx of Na+ creating funny current (If)

• Funny current leads to Ca2+ through T-type Ca2+ channels at threshold

Phase 0

Which phase of action potentials in the SA/AV node is characterized by the following properties?

• Depolarization through L-type Ca2+ channels

Phase 3

Which phase of action potentials in the SA/AV node is characterized by the following properties?

• Repolarization through K+ efflux

Ryanodine Receptor 2 (RyR2)

What are the calcium release channels in the sarcoplasmic reticulum called?

Voltage Vectors (Mean Electrical Vectors)

Sum of the individual charge differences in the heart at any given moment during depolarization/repolarization

Minus to Plus

What direction does the lead go?

Right Arm, Left Arm, Left Leg

Where are the standard limb leads located? (Einthoven & Augmented leads)

Atrial Depolarization

What event in the cardiac cycle is represented by the P wave in an ECG pattern?

P Wave (Start), Q Wave (Start)

Which two events in the cardiac cycle mark the start/end of the PR interval?

Septal Depolarization (L to R)

What event in the cardiac cycle is represented by the Q wave in an ECG pattern?

Early Ventricular Depolarization

What event in the cardiac cycle is represented by the R wave in an ECG pattern?

Late Ventricular Depolarization

What event in the cardiac cycle is represented by the S wave in an ECG pattern?

S Wave (End), T Wave (Start)

Which two events in the cardiac cycle mark the start/end of the ST segment (when the heart is fully depolarized, no electrical activity)?

Ventricular Repolarization

What event in the cardiac cycle is represented by the T wave in an ECG pattern?

Q Wave (Start), T Wave (End)

Which two events in the cardiac cycle mark the start/end of the QT interval (the amount of time it takes for the ventricles to depolarize and repolarize)?

P Wave (End), Q Wave (Start)

Which two events in the cardiac cycle mark the start/end of the PR segment?

1. 0.12 s

2. 0.12-0.20 s

3. 0.05-0.10 s

4. 0.26-0.45 s

From top to bottom, what are the durations of the following ECG intervals?

1. P Wave Duration

2. PR Interval

3. QRS Duration

4. QT Interval

0.04 Seconds

What does each small box in an ECG represent? (in seconds)