Exam 2 Flashcards
(36 cards)
What is the Frank‐Starling Mechanism?
a. Ability of the heart to change its force of contraction (contractility) & therefore stroke volume in response to changes in venous return
b. Stroke volume increases in response to an increase in preload (end diastolic volume)
- Larger volume of blood flows into ventricle = blood stretches cardiac muscle fibers = increase in force of contraction
What are the intrinsic and extrinsic factors which determine blood flow (and resistance)?
Intrinsic: signals come from inside the vasculature
Extrinsic: signals come from outside the vasculature (neural system)
Explain intrinsic control of blood redistribution
- Metabolic regulation: increase in O2 demand increase in metabolic by-products (H+, CO2)
- Endothelium-mediated vasodilation: dilator substances produced within endothelium (inner lining of arterioles) = nitric oxide, prostaglandins; Ach, adenosine
- Myogenic response: pressure changes in vessel cause VC & VD
- Vascular smooth muscle responds to increase in pressure by VD/relaxing
- Vascular smooth muscle responds to decrease in pressure by VC/contract
Explain extrinsic control of blood redistribution
- Resting conditions = SNS keeps vessels (arterioles) moderate constricted
- Sympathetic stimulation increases → vasoconstriction in specific area decreases blood flow into that area → allow blood redistribution elsewhere
- VC = dec in blood flow & inc in blood pressure - Decreased sympathetic stimulation → vessels passively dilate, inc blood flow into that area
What is the intrinsic heart rate?
The rate at which the heart beats when all cardiac neural & hormonal inputs are removed
What is Q? SV?
- Q = cardiac output (total volume of blood pumped by LV per minute)
- Q = HR*SV
- Ranges from 4.2 - 5.6 L/min - SV = stroke volume (volume of blood pumped out of the LV with each contraction)
- SV = EDV – ESV
What is venous return? How is it maintained? What is its importance?
a Blood returned to the heart
b Maintained by skeletal muscle pump
c Importance: we have limited blood volume needs to be returned so it can perfuse brain
What is EF?
a. Ejection fraction
b. EF = SV/EDV
- (EDV - ESV) / EDV
c. Measures contractility of heart (how efficient it can expel blood from LV)
What is the athlete’s heart?
Vigorous exercise (intense aerobic activity) –> working muscles need for blood increases –> demands of LV are high –> LV responds by increasing its size (like skeletal muscle) (hypertrophy)
What is MAP?
a. Mean arterial blood pressure = average pressure exerted by blood as it travels via arteries
b. 2/3 DBP + 1/3 SBP
Since diastole takes 2x time
c. Q x TPR
What is hemoglobin? Myoglobin?
a. Hemoglobin (composed of protein (globulin) & heme (iron))
- Carries oxygen from lungs to rest of body
b. Myoglobin: protein that carries & stores oxygen in muscle cells
- Captures oxygen that muscle cells use for energy
Characteristics of cardiac muscles
- Location: heart
- Appearance: branching, shorter, striated fibers connected end to end by dark stained regions (intercalated disks)
- Single, central nucleus
- Continuous, rhythmic contraction via Ca2+ induced Ca2+ release
- One fiber type similar to I
- Involuntary
- Rapid self regulation
Understand the events depicted by the Cardiac Cycle (EKG, volumes).
- Small square = 1 mm long = 0.04 sec
- height of wave used to measure voltage
- QRS wave = ventricular depolarization
- T wave (absolute refractory period) = ventricular repolarization
Sinus rhythms
- Normal = 60 - 100 bpm
- Sinus bradycardia = RHR < 60 bpm
- Sinus tachycardia = RHR > 100 bpm
Know the hormones related to exercise and which organ releases each.
- Anterior pituitary: GH & ACTH (adrenocorticotropin)
- Posterior pituitary: ADH (antidiuretic hormone) - vasopressin
- Thyroid: T3 (triiodothyronine) & T4 (thyroxine)
- Parathyroid: parathyroid hormone
- Adrenal medulla: EPI & NOREP
- Adrenal cortex: aldosterone, cortisol, androgens & estrogens
- Pancreas: insulin, glucagon
- Kidney: renin, EPO (erythropoietin)
- Testes: testosterone
- Ovaries: estrogen & progesterone
GH action
- Muscle growth & hypertrophy
- Acts directly on cells & tissues
- Stimulates lipolysis by increasing lipolytic enzyme synthesis
ACTH action
- Tropic hormone
- Controls secretion of hormones from adrenal cortex
Insulin action
- Facilitates glucose transport to cells
- Promotes glycogenesis (storage of glycogen)
- Inhibits gluconeogenesis
- Declines with exercise
- Promotes storage of glucose, amino acids & fats
- Lack → diabetes mellitus
Glucagon action
- Increase glycogenolysis to maintain plasma glucose levels
- Mobilization of glucose
- Gradually increases with exercise
- Promotes mobilization of fatty acids & glucose
What is GLUT‐4?
- Insulin-regulated glucose transporter
- Found in fat tissues & striated muscle (skeletal & cardiac)
- Responsible for insulin-regulated glucose translocation into cell
What is insulin resistance?
a. Cells are less responsive to insulin
- Reduced # of insulin receptors in cell → must release much more insulin
What stimulates thirst?
- Plasma osmolality > 295 mOsm/L (normal = 275-295)
- Water loss > 2 L
- Activation of renin-angiotensin system (RAS)
- Mouth & throat receptors
- Negative feedback → stomach distension
What is the renin‐angiotensin system?
a. RAS
b. Low BP or plasma volume → kidneys release renin into circulation
- Angiotensinogen → angiotensin I (catalyzed by renin)
- AI → angiotensin II (catalyzed by ACE (angiotensin converting enzyme))
- AII → acts on adrenal cortex to release aldosterone (conserve Na+ at kidney, therefore water will be conserved)
- ACE inhibitor → encourage diuresis (rid of water, decrease BP)
What is ANP?
a. Atrial natriuretic peptide
b. Released from atria → too much blood volume/pressure (vasoconstricted → increased venous return → ANP), bed rest (increased venous return), microgravity
