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Human Physiology > Unit 2 > Flashcards

Unit 2 Flashcards

Control of Movement/Proprioception, Autonomic Nervous System, Endocrinology, Cardiovascular Physiology

1
Q

higher centers of motor control

A
  • forms complex plans according to individual’s intention and communicates with the middle level via command neurons
  • includes areas involved with memory, emotions, and motivation, and the sensorimotor cortex
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2
Q

supplementary motor cortex

A
  • postural stabilization, coordinating of both sides of the body
  • control of movements that are internally generated rather than triggered by sensory events
  • control of sequences of movements
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3
Q

primary motor cortex

A

voluntary movement

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4
Q

promotor area

A

planning movement, spatial and sensory guidance of movement

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5
Q

parietal-lobe association cortex

A

integrating somatosensory and visual input, important for complex movements

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6
Q

middle level of motor control

A
  • converts plans received from higher centers into smaller motor programs that determine the pattern of neural activation required to perform the movement
  • programs are broken down into subprograms that determine the movements of individual joints
  • programs and subprograms are transmitted through descending pathways to the local control level
  • includes sensorimotor cortex, cerebellum, parts of basal nuclei, some brainstem nuclei
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7
Q

local level of motor control

A
  • specifies tension of particular muscles and angle of specific joints at specific times necessary to carry out programs and subprograms from middle control levels
  • includes brainstem or spinal cord interneurons, afferent neurons, and motor neurons
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8
Q

motor homunculus

A

neurons of the motor cortex that control muscle groups in various parts of the body are arranged anatomically into a somatotopic map similar to sensory homunculus in somatosensory cortex

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9
Q

corticospinal pathway

A
  • controls movements of the limbs and trunk
  • cell bodies in sensorimotor cortex and terminate in spinal cord
  • fibers crossover in medulla oblongata near the junction of the spinal cord and brainstem, and descend on the opposite side
  • skeletal muscles on the left side of the body are controlled largely by neurons in the right half of the brain
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10
Q

brainstem pathways

A
  • controls involuntary and automatic control of all musculature (tone, balance, posture, and locomotion)
  • cell bodies in the brainstem
  • most axons do not cross, affect muscles on the same side of the body
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11
Q

voluntary movements

A
  • conscious awareness of what we are doing and why we are doing it
  • attention focused on the action or its purpose
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12
Q

involuntary movements

A

unconscious, automatic, or reflex

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13
Q

proprioception

A
  • the “sixth sense” that lets us perceive the location, movement, and action of parts of the body
  • encompasses a complex of sensations, including perception of joint position and movement, muscle force, and effort
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14
Q

muscle sensory organs

A
  • muscle spindles: sense muscle length, in parallel with extrafusal fibers
  • golgi tendon organs: sense muscle tension, in series with extrafusal fibers
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15
Q

extrafusal fibers

A

ordinary muscle fibers that cause contraction

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16
Q

intrafusal fibers

A
  • in parallel with the extrafusal fibers
  • innervated with gamma-motor neurons and are co-activated with alpha motor neurons to maintain tension on spindle
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17
Q

afferent nerve

A

sensory nerve

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18
Q

alpha- and gamma-motor neuron co-activation

A
  • passive stretch of extrafusal and intrafusal muscle fibers due to external load
  • contraction of extrafusal fibers due to action potentials along alpha motor neurons removes stretch on intrafusal fibers, slowing stretch receptor firing
  • activating both alpha and gamma motor neurons maintains stretch on intrafusal fibers during shortening contraction, which provides sensory information about muscle length
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19
Q

joint receptors

A
  • respond to mechanical pressure
  • ruffini’s corpuscles: in tendon material, sensitive to stretch
  • golgi tendon organs: in ligaments, sensitive to tension
  • pacinian corpuscles: in skin, tendons, and tendon material, respond to high frequency vibrations
  • free nerve endings: throughout joint connective tissue, respond to mechanical pressure and pain
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20
Q

stretch reflex

A
  • stretched muscle activated and antagonist muscle inhibited
  • stretching the extensor causes: contraction of the extensor muscle originally stretched, relaxation of flexor muscles, contraction of other extensor muscles, and muscle length information to travel to the brain
  • knee-jerk reflec
  • remaining upright posture when the body tilts forward
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21
Q

crossed extensor reflex

A
  • inhibitor ipsilateral extensor muscles and excite ipsilateral (same side) flexor muscles
  • excite contralateral extensor muscles and inhibit contralateral flexor muscles
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22
Q

maintaining an upright posture

A
  • center of gravity must remain within base of support
  • postural reflexes: input from vestibular system, visual system, and proprioceptive receptors
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23
Q

somatic (voluntary) nervous system

A
  • division of the peripheral nervous system that provides voluntary control of skeletal muscles
  • only activation
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24
Q

autonomic nervous system

A
  • division of the peripheral nervous systems that innervates the heart, smooth muscle, and glands
  • influences the function of internal organs
  • can be excitatory or inhibitory
  • two branches: sympathetic and parasympathetic
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25
Q

two neuron system

A
  • cell body of preganglionic neuron in CNS
  • cell body of postganglionic neuron in autonomic ganglion
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26
Q

sympathetic nervous system

A
  • fight-or-flight
  • increase heart rate and strength of contraction, inhibits gastric motility
  • constrict blood vessels, increase sweat rate, mobilize energy store (increase blood glucose and fatty acids
  • helps maintain homeostasis in face of environmental stress or injury
  • releases norepinephrine and epinephrine
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27
Q

parasympathetic nervous system

A
  • rest-and-digest
  • slow heart rate and decrease strength of contraction, increase salivation, increase gastric motility, promote energy storage
  • dominates at rest
  • releases acetylcholine (nicotinic and muscarinic)
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28
Q

sympathetic ganglia

A
  • lie along both sides of spinal cord and few in abdominal cavity
  • preganglionic neurons exit spinal cord between 1st thoracic and 2nd lumbar vertebra
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29
Q

parasympathetic ganglia

A
  • close to target organ
  • preganglionic neurons exit CNS from the brainstem and sacral spinal cord
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30
Q

endocrine system

A
  • integrates organ function via hormones secreted from endocrine tissue (glands) into extracellular fluid
  • hormones circulate in the blood and bind to receptors on/in target tissues
  • receptors: high affinity, high specificity proteins on cell surface, in cytoplasm, or in nucleus
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31
Q

endocrine glands

A
  • secrete their product, hormones, into the blood rather than through a duct
  • release hormones into extracellular fluid and are then taken up by circulatory system
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32
Q

hypothalamus (endocrine system)

A
  • secretes several neurohormones that stimulate or inhibit anterior pituitary gland function
  • synthesizes oxytocin and vasopressin, which are stored and released from the posterior pituitary
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33
Q

anterior pituitary gland (endocrine system)

A
  • produced hormones with diverse actions related to metabolism, reproduction, growth, etc (ACTH, GH, FSH, LH, PRL, TSH)
  • releases tropic hormone that controls the secretion of another hormone
  • negative feedback loop
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34
Q

posterior pituitary (endocrine system)

A
  • secretes oxytocin, which stimulates uterine contractions during birth and milk secretion after birth
  • secretes antidiuretic hormone (vasopressin) which increases water reabsorption in the kidneys
  • direct extension of hypothalamus
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35
Q

thyroid (endocrine system)

A
  • thyroid hormones regulates metabolic rate, growth, and cell differentiation
  • calcitonin: role in Ca2+ homeostasis in some species
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36
Q

parathyroids (endocrine system)

A

increases blood Ca2+ and stimulates conversion of inactive to active vitamin D in the kidneys

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37
Q

adrenal glands (endocrine system)

A
  • medulla: catecholamines, epinephrine, and norepinephrine; mediate sympathetic response
  • cortex: mineralocorticoids regulate Na+ and K+ balance; glucocorticoids regulate growth, metabolism, development, immune function, and stress response; androgens have role in reproduction
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38
Q

pancreas (endocrine system)

A
  • insulin: decreases blood glucose
  • glucagon: increases blood glucose
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39
Q

ovaries (endocrine system)

A

estrogens (estradiol and progesterone) control female reproduction

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40
Q

testes (endocrine system)

A

androgens (testosterone) control male reproduction

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41
Q

non-classical endocrine glands

A
  • heart
  • kidneys
  • stomach and small intestine
  • adipose tissue
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42
Q

hormones

A
  • chemical substance produced in the body that controls and regulates the activity of certain cells or organs
  • circulating hormones are found at very low concentrations in the blood
  • bind to specific receptors
  • control: rates of enzymatic reactions, transport of ions or molecules across cell membranes, and gene expression and protein synthesis
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43
Q

feedback control of hormone secretion

A
  • a sensor detects perturbation in regulated variable
  • sensor cells modulate secretion of a hormone
  • hormone acts on target to modulate its production of another hormone or a metabolite, which may affect a second target
  • other hormones or metabolites may also feed back on the original sensor cell
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44
Q

hormone interactions

A
  • synergism: combined effect of some hormones is greater than additive
  • permissiveness: hormone is necessary for the action of second hormone
  • antagonism: two hormones exert opposite effects
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45
Q

hypothalamo-pituitary axis

A
  • pituitary gland is the master gland of the body because it controls many endocrine glands
  • hypothalamus controls the pituitary
  • neurons in hypothalamic nuclei secrete releasing/inhibitory hormones into capillary bed in the median eminence and pituitary stalk
  • capillaries coalesce into portal veins and carry hormones to the anterior pituitary
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46
Q

endocrine pancreas

A
  • beta cells secrete insulin as a response to elevated blood glucose
  • alpha cells secrete glucagon as a response to low blood glucose
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47
Q

thyroid hormone

A
  • synthesized from tyrosine and iodine in thyroid gland
  • released in response to thyroid stimulating hormone
  • negative feedback at hypothalamus and anterior pituitary
  • metabolic, permissive, and growth/development actions
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48
Q

Ca2+ regulation

A
  • large deviations in extracellular Ca2+ concentrations can disrupt neurological and muscular activity
  • regulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D
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49
Q

growth hormone (control of growth)

A
  • induces precursor cells to differentiate and secrete insulin-like growth factor 1 (IGF-1), which stimulates cell division
  • stimulates liver to secrete IGF-1
  • stimulates protein synthesis
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50
Q

insulin (control of growth)

A
  • stimulates growth via IGF-1
  • stimulates protein synthesis
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51
Q

thyroid hormone (control of growth)

A

permissive for growth hormone’s secretion and actions

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52
Q

testosterone and estrogen (control of growth)

A
  • stimulates the secretion of growth hormone at puberty
  • causes eventual epiphyseal closure
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53
Q

cortisol (control of growth)

A
  • inhibits growth
  • stimulates protein catabolism
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54
Q

stress

A
  • real or perceived threat to homeostasis
  • comprise a large number of situations
  • endocrine responds by release of cortisol from adrenal cortex and epinephrine from the adrenal medulla
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55
Q

physiological functions of cortisol

A
  • permits action of epinephrine and epinephrine on smooth muscle cells surround blood vessels (regulates blood pressure)
  • maintains cellular concentrations of metabolic enzymes required to produce glucose between meals (prevent hypoglycemia)
  • decreases inflammatory response
  • allows for proper fetal development
56
Q

effects of increased plasma cortisol during stress

A
  • effects on organic metabolism
  • enhanced vascular reactivity
  • inhibition of inflammation and specific immune responses
  • inhibition of nonessential functions
57
Q

other hormones released during stress

A
  • vasopressin and aldosterone retain water and Na+
  • overall effects of changes in GH, glucagon, and insulin
  • increased secretion of epinephrine and norepinephrine
58
Q

actions of sympathetic nervous system during stress

A
  • increase energy substrate availability
  • increase cardiac function
  • divert blood to skeletal muscles from viscera
  • increases lung ventilation
59
Q

hypersecretion

A
  • excess hormone
  • caused by tumors of exogenous treatment
  • negative feedback
60
Q

hyposecretion

A
  • deficient hormone
  • caused by decreased synthesis materials or atrophy
  • absence of negative feedback
61
Q

functions of the cardiovascular system

A
  • deliver oxygen and nutrients to tissues
  • remove carbon dioxide and waste products from tissues
  • communication (transport hormones)
  • fluid balance
  • thermoregulation
  • immune function
62
Q

principal components of the circulatory system

A
  • heart (the pump)
  • blood vessels or vascular system
  • blood (fluid connective tissue containing water, solutes, and cells that fills the tubes)
63
Q

components of blood

A
  • volume: 5-5.5 L
  • formed elements: erythrocytes, leukocytes, and platelets
  • buffy white coat: leukocytes and platelets
  • plasma: blood-cells
  • serum: blood-cells-clotting factors
  • hematocrit: fraction of blood that is red blood cells
64
Q

plasma

A
  • > 90% water with dissolved substances
  • carries electrolytes, nutrients, wastes, gases, hormones, and plasma proteins
65
Q

erythrocytes

A
  • red blood cells
  • non-nucleated, biconcave cell
  • shape increases surface area to volume ratio
  • deliver O2 to tissues, delivers CO2 to lungs, buffers pH
  • contains hemoglobin
66
Q

blood circulation

A
  • closed loop
  • volume of pumped out of the heart through one set of vessels must equal volume returning to the heart by a different set
67
Q

pulmonary circulation

A

carries O2-poor blood from the right ventricle to the lungs, returns O2-rich blood to the left atrium

68
Q

systemic circulation

A

carries O2-rich blood from the left ventricle to all the organs except the lungs and returns O2-poor blood to the right atrium

69
Q

path of blood flow through the heart

A
  1. right atrium
  2. right AV (tricuspid) valve
  3. right ventricle
  4. pulmonary semilunar valve
  5. pulmonary arteries
  6. pulmonary veins
  7. left atrium
  8. left AV (bicuspid/mitral) valve
  9. left ventricle
  10. aortic semilunar valve
  11. aorta
70
Q

cardiac excitation and conduction

A
  • pacemaker cells in sinoatrial (SA) node have fastest depolarization rate, normally pacemaker for the heart
  • conduction of action potential from SA node –> AV node (internodal pathways) –> bundle of his –> right and left bundle branches –> purkinje fibers and myocardium
71
Q

innervation of the heart

A
  • parasympathetic: fibers mainly from vagus nerve terminate on SA node, release Ach on muscarinic receptors (mAchR)
  • sympathetic: postganglionic fibers innervate entire heart, release norepinephrine and epinephrine on beta receptors
72
Q

pacemaker cell depolarization

A
  • hyperpolarization-activated channels allow Na+ influx
  • depolarization opens T-type Ca2+ channels
  • Ca2+ influx brings membrane potential to threshold for L-type Ca2+ channel activation
  • membrane potential becomes very positive
  • repolarization due to L-channel closing and K+ channel opening
  • to slow heart rate, decrease spontaneous depolarization, and vice versa
73
Q

ECG

A
  • P: atrial depolarization
  • QRS complex: ventricular depolarization
  • T: ventricular repolarization
  • atrial repolarization masked by QRS complex
  • steps: signal originates in SA node, signal spreads over atria and atrial contracts, signal delays at AV node, signal spreads down conducting fibers to bottoms of ventricles and ventricles contract, ventricles relax
74
Q

cardiac cycle

A
  • the orderly process of depolarization triggers a cycle of atrial and ventricular contraction and relaxation
  • divided into systole and diastole
  • each cycle lasts about 0.8 seconds (0.3 for systole and 0.5 for diastole)
75
Q

systole

A

ventricular contraction and blood ejection

76
Q

diastole

A

ventricular relaxation and blood filling

77
Q

ventricular systole

A
  • ventricles begin to contract
  • left and right AV valves closed
  • pressure in aorta and pulmonary arteries > left and right ventricular pressure
  • aortic and pulmonary semilunar valves closed
  • ventricles contract but no blood flow (isovolumetric contraction)
  • pressure in left and right ventricles > pressure in aorta and pulmonary arteries
  • aortic and pulmonary semilunar valves open
  • ventricles contract and eject blood, decreasing ventricular volume
78
Q

ventricular diastole (isometric relaxation)

A
  • ventricles begin to relax
  • pressure in aorta and pulmonary artery > pressure in left and right ventricles
  • aortic and pulmonary semilunar valves closed
  • pressure in left and right ventricles > pressure in left and right atria
  • left and right AV valves closed
  • ventricles relax
79
Q

ventricular diastole

A
  • ventricles continue to relax
  • pressure in aorta and pulmonary artery > pressure in left and right ventricles
  • aortic and pulmonary semilunar valves closed
  • pressure in left and right atria > pressure in left and right ventricles
  • left and right AV valves open
  • blood flows passively from atria to ventricles
  • atria contract
  • pressure in left and right atria > pressure in left and right ventricles
  • left and right AV valves remain open
  • ventricles fill additional 15-20%
  • pressure in aorta and pulmonary artery > pressure in left and right ventricles
  • aortic and pulmonary semilunar valves closed
80
Q

left ventricle pressure-volume (work) loop

A

A-C: ventricular filling (aortic closed, mitral open)
C-D: isovolumetric contraction (ortic closed, mitral closed)
D-F: ventricular ejection (aortic open, mitral closed)
F-A: isovolumetric relaxation (aortic closed, mitral closed)

81
Q

Wiggers diagram

A
  • lub: first heart sound, closing of AV valves at start of systole
  • dub: second heart sound, closing of semilunar valves at start of diastole
  • dicrotic notch: blood recoils off semilunar valve
82
Q

cardiac output (CO)

A
  • volume of blood pumped out of each ventricle per unit time
  • product of heart rate and stroke volume (CO=HR*SV)
  • blood loss causes decrease in stroke volume and increase in heart rate to maintain CO
83
Q

regulation of heart rate

A
  • average heart rate is 72 bpm but increases to ~100 bpm if you remove nervous and hormonal influences
  • at rest, parasympathetic influence on the SA node dominates
  • sympathetic activity increases HR
84
Q

effects having to do with the heart

A
  • chronotropic: effects that change HR
  • inotropic: effects change contractility (strength of cardiac contraction)
  • lusitropic: effects change rate of relaxation
85
Q

stroke volume

A
  • volume of blood ejected from the ventricle during each contraction
  • difference between end-diastolic volume (maximal ventricular filling) and end systolic volume (maximal ventricular emptying)
  • SV=EDV-ESV
  • determined by EDV/preload, contractility, and afterload (arterial pressures)
86
Q

Frank-Starling Mechanism

A
  • stroke volume increases as end-diastolic volume increases
  • contractility: strength of contraction at any given EDV
  • sympathetic stimulation causes an increase in contractility
87
Q

sympathetic regulation of stroke volume

A

GPCR –> adenylyl cyclase –> cAMP –> PKA –> excitation-contraction coupling proteins or sarcomeric proteins

88
Q

ejection fraction

A
  • quantifying contractility
  • ratio of stroke volume to end-diastolic volume
  • EF=SV/EDV
  • as EF increases, contractility increases
89
Q

effect of afterload on SV

A
  • increased arterial pressure tends to reduce stroke volume
  • increased load causes increased pressure heart must generate
  • greater the load, the less contracting muscle fibers can shorten at a given contractility, causing a smaller stroke volume
90
Q

evaluation of cardiac function

A
  • angiography: used to identify narrowed coronary arteries
  • echocardiography: detects abnormal function of cardiac valves or contractions of cardiac walls, can be used to measure ejection fraction
91
Q

function of the vascular system

A
  • regulate blood pressure and distribution of blood flow to various tissues
  • elaborate branching and regional specializations of blood vessels enable efficient matching of blood flow and metabolic demand in individual tissues
92
Q

endothelium (endothelial cells)

A
  • common structural component of entire circulatory system (from heart to capillaries)
  • smooth, single cell layer in contact with blood
93
Q

pressure (P)

A
  • force exerted by the blood, measured in mmHG
  • blood moves from areas of high pressure to areas of low pressure
94
Q

flow (Q)

A

volume of blood moved per unit time, measured in mL/minute

95
Q

resistance (R)

A

describes how difficult it is for blood to flow between two points at any given pressure difference, calculated not measured

96
Q

relating pressure, flow, and reistsance

A

Q=(change in P)/R

97
Q

vessel resistance is determined by…

A
  • directly proportional to vessel length and blood viscosity
  • inversely proportional to vessel radius to the fourth power
98
Q

vessel diameter is primary determinant of blood flow

A
  • most important quantitatively and physiologically
  • vessel diameter changes due to contraction and relaxation of the vascular smooth muscle in the wall of the blood vessel
  • very small changes in vessel diameter lead to large changes in resistance
  • vessel length does not change significantly
  • blood viscosity normally stays within small range
99
Q

large arteries

A
  • high, pulsatile pressure
  • recoil provides pressure reservoir
  • low resistance to flow
  • multiple layers of elastic fibers and smooth muscle
100
Q

arterioles

A
  • declining pulsatile pressure
  • origin of vascular resistance
  • controls distribution of blood flow
  • lacks elastin fibers
  • layer of smooth muscle
101
Q

capillaries

A
  • pulsatile pressure remains
  • single layer of epithelial cells
  • gas, nutrient, and waste exchange (purple)
102
Q

large veins

A
  • constant low pressure
  • low resistance to flow
  • high capacitance vessels, can stretch
  • hold ~70% of blood
  • few layers of elastic fibers and smooth muscle
103
Q

venules

A
  • pressure no longer pulsatile
  • low pressure
  • thin porous layer of muscle and elastic tissue
  • allow migration of cells out of vessel
104
Q

endothelial cell functions

A
  • permeability barrier
  • blood cells do not normally adhere
  • secretes platelet regulators
  • secretes paracrine agents
  • mediate angiogenesis (ne capillary growth)
  • central function in vascular remodeling
  • produce growth factors and cytokines in response to damager
105
Q

movement of blood into and out of arteries

A
  • arteries are highly compliant
  • compliance=change in volume/change in pressure
  • higher compliance, more easily stretch
  • elastic recoil maintains pressure and flow during cardiac diastole
105
Q

blood pressure in blood circulation

A
  • higher pressure in systemic circulation than pulmonary circulation
  • pressure in arteries, arterioles, and capillaries on both sides is pulsatile
  • systemic circulation must force greater volumes of blood further through the body compared to pulmonary
106
Q

arteriosclerosis

A

general term for development of thick, stiff arteries

107
Q

atherosclerosis

A

specific type of arteriosclerosis caused by buildup of fats, cholesterol, and other substances in and on artery walls; plaque narrows artery and can burst, leading to a blood clot

108
Q

blood pressure

A
  • pressure exerted by blood on arterial walls
  • written as systolic (maximal arterial pressure, during peak ventricular ejection) / diastolic (minimum arterial pressure, end of diastole)
109
Q

pulse pressure

A
  • difference between systolic and diastolic pressure
  • determined by stroke volume, speed of ejection of the stroke volume, and arterial compliance
  • large pulse pressure may indicate stiff arteries and is a risk factor for heart disease
110
Q

changes in blood pressure with age

A
  • systolic pressure tends to rise over an individual’s lifetime
  • diastolic pressure tends to rise into adulthood then remain steady or decline later in life
111
Q

mean arterial pressure (MAP)

A
  • average pressure driving blood into the tissues over entire cardiac cycle
  • MAP=diastolic pressure + 1/3(pulse pressure)
  • changes in compliance have little effect on MAP
  • minimum MAP of 60 mmHg is required to maintain perfusion of organs
  • MAP=CO*TPR
112
Q

total peripheral resistance (TPR)

A

resistance that must be overcome to push blood through the circulatory system and create flow

113
Q

arterioles

A
  • determine relative blood flow (fraction of cardiac output) to a given organ
  • sum of resistance in all arterioles of the body determines TPR
  • maintains intrinsic tone
  • smooth muscle can dialate or restict the arteriole
114
Q

active hyperemia

A
  • local increase in vasodilatory substance –> arteriole smooth muscle relaxation –> decrease in local resistance –> increase blood flow
  • many of these substances from increased energy metabolism, some involved with inflammation
115
Q

myogenic response

A
  • vascular smooth muscle triggers smooth muscle contraction
  • sudden increase in blood flow into an arteriole triggers arteriole constriction and maintains constant flow rate into the tissue
116
Q

flow autoregulation

A
  • decrease in blood flow tends to induce vasodilation
  • ischemia, lack of blood flow, causes release of some of vasodilatory substances involved in reactive hyperemia
117
Q

extrinsic control of arteriole resistance

A
  • extensive sympathetic innervation symptoms
  • norepi/epi binding to alpha receptors causes vasoconstriction, decreasing blood flow
  • norepi/epi binding to beta receptors causes vasodilation, increasing blood flow
  • most arterioles express alpha receptors and arterioles in the heart express beta receptors
118
Q

hormonal regulation of blood pressure

A
  • angiotensin II and vasopressin cause water reabsorption and vasoconstriction, increasing blood pressure
  • atrial natriuretic peptide increase Na+ and water excretion, decreasing blood volume and blood pressure
119
Q

types of capillaries

A
  • continuous: intercellular clefts, gaps between neighboring cells that allow small molecules to pass
  • fenestrated capillaries: many gaps in membrane
  • sinusoidal: large gaps, large enough to allow blood cell through, leakiness of capillaries
120
Q

blood flow through capillaries

A
  • flow rate inversely proportional to cross-sectional area (capillaries have large surface area, decreasing flow rate)
  • transit time of blood through capillary bed is sufficient for efficient exchange of gases, nutrient, and waste products
121
Q

Starling Forces

A
  • difference between capillary hydrostatic pressure and tissue hydrostatic pressure favors filtration out of capillary
  • difference between capillary osmotic pressure and tissue osmotic pressure favors absorption into capillary
  • arterial end: (capillary hydrostatic pressure-interstitial osmotic force) > capillary osmotic force, fluid flows out of the capillary into the interstitial fluid (favors filtration)
  • venous end: (capillary hydrostatic pressure-interstitial osmotic force) < capillary osmotic force, fluid flows from the interstitial fluid into the capillary (favors absorption)
  • outward flow > inward flow –> lymphatic system
122
Q

venous return

A
  • amount of blood returned to the atria
  • veins are highly compliant
  • enhanced by sympathetic stimulation, skeletal muscle pump, and respiratory pump
123
Q

skeletal muscle pump

A
  • muscle contraction compresses veins
  • unidirectional blood flow toward heart due to one-way valves
124
Q

respiratory pump

A
  • during inspiration contraction of diaphragm and intercostal muscles expand thoracic cavity
  • thoracic pressure drops
  • increased central-peripheral pressure difference increase blood flow back to heart
125
Q

lymphatic system

A

network of lymph vessels and lymph nodes that collect and filter capillary filtrate and returns it to the circulatory system

126
Q

baroreceptors

A
  • stretch receptors
  • in carotid sinus and aortic arch
  • increased arterial pressure stretched vessel and activates receptors
  • afferent neurons project to the cardiovascular control centers in the brainstem
127
Q

atrial natriuretic hormone

A
  • reduced blood pressure
  • released from atria in response to stretch
  • acts on kidney, increasing water and sodium excretion (urine production), decreasing blood volume (slower)
  • acts on vascular smooth muscle, causing vasodilation, decreasing blood pressure (faster)
128
Q

oxygen consumption

A
  • oxidative metabolism requires oxygen
  • oxygen consumption (VO2) is the amount of oxygen consumed
  • VO2=CO*(arterial oxygen-venous oxygen)
  • CO determines amount of oxygen delivered to tissue
  • arterial oxygen content: amount of oxygen entering tissue
    venous oxygen content: amount of oxygen leaving tissue
  • difference: amount of oxygen consumed by tissue
  • after training an individual is able to consume oxygen at a faster rate, meaning they can produce energy via oxidative metabolism faster than prior to training (increased VO2 max due to increased CO and a-vO2)
128
Q

hypotension

A
  • low blood pressure, regardless of the cause
  • significant loss of blood volume, as in hemorrhage, vaises decrease in blood flow to brain and cardiac muscle
  • blood loss tiggers autotransfusion to partially restore blood volume and pressure
129
Q

shock

A
  • any situation in which a decrease in blood flow to the organs and tissues damages them
  • hypovolemic shock: caused by decrease in blood volume secondary to hemorrhage or loss of fluid other than blood
  • low-resistance: due to decrease in TPR secondary to excessive release of vasodilators
  • cardiogenic: due to an extreme decrease in cardiac output from any variety of factors
130
Q

cardiovascular response to exercise

A
  • increase blood flow to brain and heart, no change in % of CO
  • increase blood flow to working muscle, total amount and % of CO
  • increase blood flow to skin, increase % of CO, greater increase in heat
  • decrease blood flow to kidneys and abdominal organs, decrease % of CO
131
Q

impact of endurance exercise on heart rate

A
  • decrease in resting heart rate
  • decrease in submaximal heart rate
  • no change in maximal heart rate
131
Q

impact of endurance exercise on cardiac output

A
  • increase in work capacity
  • increase in maximal cardiac output
  • no change in submaximal cardiac output
132
Q

impact of endurance exercise on stroke volume

A
  • increase in resting stroke volume
  • increase in submaximal stroke volume
  • increase in maximal stroke volume
  • plateaus eventually

Human Physiology (1 decks)

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