ANSC EXAM #4

what connects cardiac muscle cells

intercalated discs

what are intercalated discs composed of? what is the purpose?

made of different cell-cell adhesions: desmosomes, gap junctions

allows the heart to work as a functional system

what are the three layers of the heart

1. epicardium

2. myocardium

3. endocardium

where is the heart located

in the mediastinum, sitting in the pericardial sac (made of pericardium)

what are the layers of the pericardial sac

1. the outer layer: parietal layer

2. the inner layer: visceral layer “epicardium”

what is between the two layers of the pericardial sac

10-20mL of fluid, pericardial fluid. for movement fluidity

what is the myocardium

the muscle portion of the heart

what is the endocardium

the smooth muscle, continuous with the endothelium lining blood vessels

what are the top compartments of the heart

the atria

what are the bottom compartments of the heart

the ventricles

describe the flow of blood in the heart

vena cava → right atrium → right atrioventricular valve → right ventricle → pulmonary semilunar valve → pulmonary artery → lungs → pulmonary vein → left atrium → left atrioventricular valve → left ventricle → aortic semilunar valve → aorta

what is considered the “pumping part” of the heart

the ventricles

what is the right atrioventricular valve also known as

right AV valve

tricuspid valve

what is the left atrioventricular valve also known as

left AV valve

bicuspid valve

what separates the left/right ventricle chambers

the septum

what is diastole

relaxation

what is systole

contraction

describe the cardiac cycle

1. ventricles contract (pressure increases, ventricle pressure exceeds atrial)

2. forced closure of AV valves (blood stops flowing into ventricles)

3. isovolumetric contraction (ventricle pressure exceeds the arterial pressure)

4. opening of semilunar valves (blood can now leave the ventricles, so they relax, and then arterial pressure exceeds ventricle)

5. closure of semilunar valves (all valves are closed, isovolumetric relaxation), ventricle pressure is lower than atrial which has filled with blood

6. opening of AV valves (blood can flow out of atrium into ventricle

what are the chordae tendonae

the papillary muscles that the valves attach to, all lined by endocardium

how do the left + right sides work, timing wise

although they are separate, they always work synchronously because of the cardiac cycle

what is the SA node?

sinoatrial node, responsible for electrical conductivity: works as a pacemaker setting the heart rate because the cells can depolarize

where is the SA node located

in the vena cava

how does the SA node affect the atrium?

the intercalated discs of the cardiac muscle receive the SA node’s signal, and atria cells all depolarize, contracting at the same time

how does the SA node affect the ventricles?

the conducting fibers send the SA node’s signal to the atrioventricular node (AV node)

how does the AV node contract the ventricles

the AV node slows down the speed of the impulse, then sending it to the AV bundle (or bundle of His), then sending it through the purkinje fibers, causing contraction

what are Purkinje fibers

fibers that are embedded in cardiac muscle in ventricles, allowing for synchronized contraction of the ventricle

what contracts first, the atria or ventricles?

the atria contract first because of the quick signal via intercalated discs

ventricle contracts later because the signal passes through conducting fibers, then delayed via the AV node, then the AV bundle and through fibers

why is contraction offset important?

the offset in timing of atrium vs ventricle contraction is key for generating pressure difference in the heart

how does acetylcholine impact the SA node

parasympathetic. reduces rate of depolarization

how does norepinephrine impact the SA node

sympathetic. increase rate of depolarization

what is an EKG/ECG

an electrocardiogram/graph which detects the movement of charged particles via electrode use

what are the 3 types of waves on an ECG, in order

P wave

QRS complex

T wave

what is the P wave

the depolarization of the atrium

what is the QRS complex

depolarization of ventricles

what is the T wave

repolarization of ventricles

what is the largest wave on an ECG

QRS complex

what is stenosis

the narrowing of valves (don’t open completely)

what is regurgitation

when the valves don’t close completely (backflow in the heart)

what are the values comprising a blood pressure reading

systolic/diastolic

systolic=highest value=heart is contracting

diastolic=lowest value=heart is relaxed

how is flow/resistance affected when the vessel is constricted? dilated?

constricted: low flow, high resistance

dilated: high flow, low resistance

what is the response to a transient change in blood pressure/heart rate

baroreflex (a rapid, essential negative feedback system that maintains stable blood pressure)

how does norepinephrine increase heart rate

by binding beta1 receptors in the SA node

what are baroreceptors activated by

an increase of force in a blood vessel

what is the baroreceptors response to activation

1. activate the cardioinhibitory center

2. inhibit the vasomotor center

(both in the medulla of the CNS)

what does the cardioinhibitory center do

causes the parasympathetic system to release acetylcholine, thus reducing rate of depolarization

THIS IS ACTIVATED BY THE BAROREFLEX

what does the vasomotor center do

causes sympathetic system to release norepinephrine, thus increasing rate of depolarization

THIS IS INHIBITED BY THE BAROREFLEX

what are the two models which explain the response for low O2

1. vasodilator model

2. nutrient demand model

describe the vasodilator model

high demand for O2 that is unmet causes tissue to release vasodilating factor → acts on sphincters that control capillaries within tissues → sphincters relax, increasing amount of blood flow to the tissue

describe the nutrient demand model

high demand for O2 that is unmet causes direct relaxation of sphincters that control blood flow to the capillary bed (because the sphincters become unable to maintain contraction)

what is the autoregulation of blood flow

the ability to maintain blood flow despite changes in pressure

what is the role of Nitric Oxide (NO) in vasodilation

nitric oxide works as a vasodilator, activating guanylate cyclase, creating cyclic GMP, causing cells to relax and vasodilate

where is guanylate cyclase located

it is an enzyme found in vascular smooth muscle cells

what is Nitric Oxide released by

NO is commonly released by endothelial cells

what allows for vasodilation to be a transient event

phosphodiesterases (like PDE5) break down cyclic GMP (cGMP) causing vasodilation to stop, and allowing the blood vessel to return to the natural state

what is angiogenesis? what are the two types

the formation of new blood vessels

sprouting and splitting angiogenesis

describe the initiation sprouting angiogenesis

VEGF (vasoendothelial growth factor) is released by hypoxic tissues, and it binds receptors on endothelial cells, releasing proteolytic enzymes

what are proteolytic enzymes

enzymes that break down proteins in extracellular matrix of blood vessel, thus the basement membrane

what are the steps of sprouting angiogenesis

1. endothelial cells disperse

2. endothelial cell mitosis (increased cell #)

3. cells form cords, extending from vessel toward hypoxic tissue

4. cords flatten (widen and form sheet) and then roll together to form a tube

what is the process of splitting angiogenesis

one vessel to two blood vessels

forms a zone of contact: perforating sections between endothelial cells

what are fibroblasts? what role do they play in splitting angiogenesis?

fibroblasts are connective tissue cells that make the extracellular matrix (basement membrane), and then collagen proteins will surround the vessel to complete the new vessel

what is the purpose of the mucosa in the nasal cavity? what is it made of?

the mucosa is made of proteins called mucins, producing mucus

the mucus traps pathogens and foreign particles

what is the flow of the respiratory tract

nasal cavity → pharynx → larynx → trachea → primary bronchi → secondary bronchi → tertiary bronchi → bronchioles → alveoli

what is the larynx also known as

the organ of phonation

what is the structure of the trachea

a large single pipe, surrounded by incomplete cartilaginous rings that are linked by the trachealis muscle

describe primary, secondary, and tertiary bronchi

primary + secondary: have complete cartilaginous rings

tertiary: have small patches of cartilage

what are the bronchioles made of

smooth muscle

what are the alveoli

the sites of gas exchange

how do bronchioles dilate

when the beta2 receptors are bind, they cause smooth muscle to relax, allowing bronchioles to dilate

what are the drugs that address asthma

beta2 agonists, like albuterol, that bind beta2 receptors

what is the pleura

the lining of the lungs

what are the layers of the pleura

visceral: on the lung

parietal: on the chest wall

(fluid between these allows movement)

what is pleuritis

inflammation of the pleua, on the surface of the lung

what is surfactant

produced by alveoli that provides resistance to collapse of sacs, allowing them to fully inflate

describe inspiration and expiration

inspiration (active)- air in

expiration (passive)- air out

what are some other structures (not lungs) involved in ventilation

• diaphragm: can expand + contract

• abdominal muscles

• intercostal muscles: muscles between ribs

what is tidal volume

the amount of air moved into/out of lungs in one respiratory cycle

what are the reserves in the lungs

inspiratory reserve: the extra air in

expiratory reserve: the extra air out

what comprises the vital capacity of the lung

tidal volume + inspiratory reserve + expiratory reserve

what is residual volume

the space we have to move air in the lungs that is beyond the expiratory reserve

what comprises the total lung capacity

vital capacity + residual volume

what are the 4 regions of the brain that control unconscious ventilation

1. dorsal respiratory group

2. pneumotaxic center

3. apneustic center

4. ventral respiratory group

what is the dorsal respiratory group responsible for

the major site of signal integration

sets the rate of ventilation, initiates inspiraton

what is the pneumotaxic center responsible for

increasing the inspiration rate

what is the apneustic center responsible for

responsible for deep inspiration

what is the ventral respiratory group responsible for

responsible for expiration

define eupnea

normal pattern ventilation

define dyspnea

difficult ventilation

define hyperpnea

rapid ventilation

define polypnea

rapid and shallow ventilation

define bradypnea

slow ventilation

define apnea

without ventilation (a temporary cessation)

define panting

generally low tidal volume ventilation, largely moving in anatomical dead space

what are the 4 processes for removing foreign substances

1. macrophages (can engulf and remove particulates)

2. substances can move into interstitial space (picked up by lymphatic system)

3. blood vessels (blood stream picks things up)

4. sequestration (connective tissue covers it within alveoli, forms scar tissue)

what is boyle’s law

pressure is inversely proportional to volume

what does boyle’s law explain

ventilation, why breathing in/out and contraction/relaxation brings air out/in

what is henry’s law

the amount of gas in a solution is directly proportional to its partial pressure

what is dalton’s law

the law of partial pressures, that the sum of partial pressures equals the total pressure in a mixed gas

what do henry’s and dalton’s laws explain

why we see gas exchange between alveoli/capillaries and capillaries/tissues

gases will flow according to their partial pressure differences

what is mastication

the working of food into smaller particles and a bolus of food

what are 3 phases of swallowing

1. oral phase

2. pharyngeal phase

3. esophageal phase