Bio Exam #2

Arteries

Carry blood away from the heart

Veins

Carry blood towards the heart

The layers of the heart wall from superficial to deep are:

Endocardium, Myocardium, Epicardium, Serious Pericardium, Fibrous Pericardium

Myocardium

muscular layer of the heart

Cardiac muscle cells

contain myofibril and sarcomeres, contract involuntary and contain only 1-2 nuclei

myocardial contractile cells

99% of the heart

myocardial conductive cells

1% of the heart

intercalated discs

hold cardiac muscle cells together (form a zig-zag)

Similarity to skeletal muscle

Has sarcoplasmic reticulum and T-Tubules

Gap Junctions

channels between cardiac cells for the passage of ions, that allow the heart to contract and pump in unison

Pacemaker

Heart can generate its own rhythm

Electrical Pathway

SA node, AV node, Bundle of His, Purkinje fibers

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

Systole

Contraction of the heart (Depolarization)

Repolarization

Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell.

Diastole

Relaxation of the heart (Repolarization)

Conductile Cells

no true resting potential, sodium slowly leaks in and at the threshold hit rapid depolarization. Depolarized (relaxed) through K+ influx

What do contractile cells have that is important for their function?

Resting potentials

What happens when an action potential is received by contractile cells?

Na flows in, causing rapid depolarization.

What occurs at the peak of depolarization in contractile cells?

Na channels close and Ca2+ channels open.

What is the effect of Ca2+ channels opening in contractile cells?

It maintains contraction for a long time.

What happens when Ca2+ channels close in contractile cells?

The membrane repolarizes with K+ influx.

When do K+ channels close in contractile cells?

At the end of the refractory period.

EKG/ECG

electrocardiogram detects five prominent points during a heartbeat

P wave

atrial depolarization

P-R segment

represents the action potential delayed at the AV node; atrial depolarization complete

QRS wave

ventricular depolarization

S-T segment

plateau phase, ventricular systole

T wave

ventricular repolarization

atrioventricular valves closing

Tricuspid and Mitral Valves, the "Lub" Sound

semilunar valves closing

Pulmonary and Aortic Valves, the "Dub" Sound

Cardiac Performance = Cardiac Output

How well your heart performs = how much blood it pumps per minute

Cardiac Output

the amount of blood pumped by each ventricle in 1 minute (L/min)

Stroke Volume

how much blood is pumped per heart beat per minute

Cardiac Output Equation

HR x SV = CO

Factors affecting heart rate

autonomic innervation, hormones, fitness levels, age

Factors affecting stroke volume

heart size, fitness levels, gender, contractility, duration of contraction, preload, after load

End Diastolic Volume (EDV)

Volume of blood in ventricles before contraction. (Preload)

End Systolic Volume (ESV)

Volume of blood remaining in ventricles after contraction.

Stroke Volume Equation

EDV-ESL

More EDV means

more blood pumped -> higher stroke volume

More ESV means

less blood pumped -> lower stroke volume

The Cardiac Output of a regular human

heart pumps 4-8 Liters of blood every minute at rest

If stroke volume doesn't change

Heart rate raises or lowers Cardiac Output

Resting HR

60-120 bpm

HR During Exercise

150 BPM

Infant RHR

120 BPM

Max HR

220 BPM

Bradycardia

slow heart rate (less than 60 bpm)

Tachycardia

Fast heart rate (HR greater than 100bpm)

Cardiovascular Centers

located in brainstem and control your heartrate

Cardioaccelerator Center

sympathetic, speeds up HR

Cardioinhibitor Center

parasympathetic, slows down HR

tone

heart is always getting stimulation from both cardiovascular centers

cardiac plexus

where both cardiovascular centers connect to (base of heart)

Norepinephrine (NE)

Sympathetic chemical released that shortens depolarization time, increases HR, makes heart cells reset faster, binds to beta 1 - receptor

Acetycholine (ACh)

Parasympathetic, opens K+ channels to slow depolarization, slows HR

Cardiac Reflexes

automatic responses that adjust HR based on what your body needs, receptors sensors that detect changes and send signals to cardiovascular centers

Proprioceptors

detect exercise

Baroreceptors

detect blood pressure (pressure in walls of blood vessels)

Chemoreceptors

Detect changes in blood gases and pH (CO2, O2, Acidity)

factors affecting stroke volume

Preload, Contractility, Afterload

Preload

how much the heart fills with blood at EDV

Contractility

how strongly the ventricles contract. stronger contraction -> more blood pushed out. higher contractility = higher stroke volume

Afterload

resistance the heart has to pump against. higher afterload = lower stroke volume

Other factors that affect SV

Venous return, filling time, autonomic intervention, hormones, vasodilation

blood pressure (BP)

The pressure that the blood exerts against the walls of blood vessels caused by the heart contraction (pumping)

how is blood pressure measured

systolic/diastolic or contraction/relaxation

Pulse Pressure

systolic pressure - diastolic pressure

Mean Arterial Pressure (MAP)

Average pressure in your arteries overtime

Where is blood pressure high vs low

Blood pressure is high near the heart, but drops at arterioles and is low at capillaries and veins

Pulse

pressure wave that travels through your arteries when your heart beats. artery walls expand and snapback creating wave of pressure

How to measure blood pressure

sphygmomanometer (BP cuff) and stethoscope

Korotkoff sound

sound when artery is partially compressed

Factors affecting blood pressure

smaller vessel = higher pressure, larger vessel = lower pressure

factors affecting blood flow speed (velocity)

narrow vessel = blood flows fasters, wide vessel = blood moves slower

Cross sectional area

total space blood can flow through

Capillaries

where change of fluids, nutrients and waste happens

Filtration

where water leaves capillary (beginning)

reabsorption

water reenters capillary (end)

Capillary hydrostatic pressure (CHP)

pushes fluid out - pressure of blood

Interstital fluid hydrostatic pressure (IFHP)

push fluid into capillary - pressure from surround tissue

Blood colloid osmotic pressure (BCOP)

pulls fluid into capillary - main force of reabsorption

interstitial fluid colloidal osmotic pressure (IFCOP)

pull fluid out of capillary - protein from surrounding tissue

Blood Plasma

55% of blood

Formed Elements

(37-54% of blood)red blood cells, white blood cells, platelets

Hematocrit

percentage of blood volume occupied by red blood cells

Hematopoiesis

blood cell formation

Hematopoietic Stem Cell (HSC)

What cell gives rise to all formed elements? in bone marrow

Erythrocytes (RBCs)

transport oxygen and carbon dioxide. 120 day lifespan

Leukocytes (WBCs)

immune defense. exits capillaries and moves into tissues. lifespan of a few days

Granulocytes

neutrophils, eosinophils, basophils

Neutrophils

most common abc, affective against bacteria and releases chemicals. lifespan of min-days

Eosinophils

parasite killers, allergy regulation. lifespan of min-days

Basophils

promotes inflammation, least common WBC. lifespan - unknown

Agranulocytes

lymphocytes and monocytes

Lymphocytes

T cells -> kill infected cells

B cells -> make antibodies

Natural Killer -> Kill abnormal/cancer cells

lifespan of many years