physio lab 7, 8 & 9

respiratory sinus arrhythmia

heart rate rises during inhalation and slows during exhalation

mechanics of RSA

lung vol increases → greater venous return via vena cava (to R atrium) → stretch receptors activated → afferents in vagus nerve to cardiac centers of medulla → activate sympathetic efferents to SA node → raise heart rate

Bainbridge reflex

increased venous return → increased central venous pressure → atrial stretch receptors → vagus afferents to medulla → sympathetic efferents to SA node

effects of apnea

bradycardia, especially in cold water; spleen signaled to release blood

dive response mechanics

peripheral temperature sensors send afferent impulses to hypothalamus → dramatic increase in BP → detected by baroreceptors in carotid sinus → signals cardiac center in medulla → slow HR

vagus nerve sensory information

communicate information about organs (i.e. O2 levels, pH levels)

vagus nerve motor information

communicate information about HR, breathing rate, swallowing

parasympathetic effects

decreased conduction through AV node + decreased HR; bronchoconstriction and increased bronchial secretions; vasodilation; movement of smooth muscle and increased secretion in digestive system; release of enzymes and insulin from pancreas; increased flow and excretion of urine from urinary system

vagal tone

measures HR, HR variability, and relation to breathing, psychological stress, physical stress

RSA parasymp/ symp effects

high parasympathetic activation → more pronounced RSA; high sympathetic activation → less pronounced RSA

mammalian dive reflex

physiological changes to conserve O2 while immersed in water; triggered by apnea and water on face and nose

reactive hyperemia

local blood flow to individual tissues changes depending on needs (increased O2 consumption and associated changes in CO2 and temp; pH changes)

reactive hyperemia blood flow changes

vasodilation, increased blood flow; does not disrupt blood flow or pressure in the entire cardiovascular system; mean arterial pressure unchanged

autoregulation

relative independence of local blood flow and arterial pressure

active hyperemia

dilation of many vessels at once; decreases overall peripheral resistance, causing pressure in cardiovascular system to drop.

baroreceptors

detect changes in systemic blood pressure (and systemic blood flow); in aorta and carotid arteries

medulla

signals sent here from baroreceptors when systemic arterial pressure is low. Has sympathetic motor neurons in vasomotor center and cardioaccelerator

baroreceptor reflex

can adjust systemic arterial pressure changes quickly; baroreceptors sense change in BP, send signal to medulla. Medulla signals vasomotor and cardioaccelerator to trigger peripheral vasoconstriction and increase heart rate.

arterial chemoreceptors

in carotid body; monitor blood pH, CO2, O2 levels; emotional reactions can influence too

arterial blood pressure

standard measure of blood pressure, measured as close to the aorta as possible. represents the highest BP expereinced by the cardiovascular system

negative feedback reflex mechanism

simple neural circuits that respond to stimuli and are self-limiting

nitric oxide

produced by epithelial cells of arteries; released in response to physical shearing stress from high blood flow. causes relaxation of smooth muscle right next to epithelium

systemic regulation of BP

hormones (ADH, epinephrine, norepinephrine) can sustain vasomotor tone and cardiac output

glucocorticoids and thyroid hormone

can raise BP thorugh effects on glucose metabolism and metabolic rate

ADH, aldosterone

raise BP by enhancing water resoprtion in kidneys

histamine

vasodilator, cause of local swelling

autoregulation vasodilators

decrease O2; increase CO2, metabolic acids, NO, K+, H+, inflammation, body temp; relax precapillary sphincters; increase blood flow

autoregulation vasoconstrictors

prostaglandins, products released by activated platelets, leukocytes, and endothelins; constrict precapillary sphincters; decrease blood flow

neural mechanism: blood chemistry

cardiac, vasomotor centers; vasoconstriction of peripheral vessels by NE; vasodilation of some via ACh and NO

renal endocrine control

erythropoietin (RBCs); renin/ angiotensin/ aldosterone

adrenal endocrine control

catecholamines

brain endocrine control

ADH

heart endocrine control

ANH

hyperemia

increase blood flow to tissues

reactive hyperemia

increase in local blood flow to specific tissue following temporary loss of flow; response to low O2, high CO2, pH, metabolic waste; local vasodilation

active hyperemia

larger scale dilation of vessels and decrease in peripheral resistance during exercise

sphygmomanometer

first sound: systolic pressure; loss of sounds: diastolic pressure

compliance

ability of compartment to expand and accommodate increased content; more compliance = greater ability to accommodate increased blood flow without increased BP

hypovolemia

low blood vol, only symptomatic after 10-20% volume lost

hypervolemia

excess blood volume from retention of water and sodium

cardioaccelerator center

stimulate cardiac function by regulating heart rate and stroke

cardioinhibitor centers

slow cardiac function by decreasing heart rate and stroke volume; parasympathetic stimulation from the vagus nerve

vasomotor centers

control vessel tone and contraction of smooth muscle; change diameter of vessel to affect peripheral resistance, pressure, and flow

chemoreceptor reflex - exercise

drop in O2, increase CO2, drop pH; stimulate cardioaccelerator and vasomotor centers; increase cardiac output, constrict peripheral vessels

chemoreceptor reflex - resting

higher O2, lower CO2, increase pH; stimulate cardioinhibitory centers; decrease cardiac output, peripheral vasodilation

glucocorticoids

increased Na+ and water retention in kidneys; receptors in vascular smooth muscle and endothelial cells

hypothyroidism

slower HR, loss of arterial elasticity, increased BP

hyperthyroidism

atrial fibrillation, high BP, widened pulse pressure

no thyroid disease

higher T3 signals higher metabolic demands and corresponds to higher HR, blood flow, BP

allometry

nonlinear scaling of physiology with body size

physiology with allometric relationships

heart size, brain size, metabolic rate, number of offspring, lifespan

Kleiber’s Law

metabolic scaling is at ¾ power (Y proportional to M³/4)

reasons for Kleiber’s Law

restraints of the circulatory system; doubling the number of cells requires more than double in circulatory capacity

reasons behind metabollic rate differences

surface area to volume ratio decreases as body size increases (less heat lost to environment); blood easier to circulate in larger organisms; more reserve (adipose) mass, which is metabolically active, structural components

weapons and ornaments

sexual selection for dimorphic traits; scale allometrically and positively

metabolic rate

rate of fuel oxidation for the production of ATP, measured by O2 consumption or CO2 production