Reflexes Flashcards
Describe neural regulation of circulation, including various reflexes that influence it.
Nervous regulation of circulation involves
① redistributing blood to different areas of the body.
② increasing the heart’s pumping activity
③ providing rapid BP control
Only the SNS provides ANS circulatory control through the vasomotor center in the medulla (and pons)Which has vasoconstrictor fibers throughout circulation .These fibers secrete NE onto alpha fibers, causing vasoconstriction. The vasodilator area inhibits this mechanism and sensory area regulates both.
Nervous Regulation of Circulation
Local flow control locally
Nervous control for
Redistributing blood flow to different body areas
Increasing heart’s pumping activity
Providing rapid BP control
Regulated by autonomic nervous system (ANS)
Sympathetic
Circulation
Heart function
Parasympathetic
Heart Function
NOT circulation
Sympathetic Innervation
of Blood Vessels
Most tissues: all vessels except capillaries
Some tissues: precapillary sphincters & metarterioles
Innervation of small arteries/arterioles can increase resistance and decrease flow
Innervation of large vessels (veins) can decrease volume/affect heart pumping
Control by the CNS
Vasoconstrictor fibers (throughout circulation)
Especially kidneys, intestines, spleen
Not as much brain, skeletal muscle
Vasomotor Center
Medulla/lower pons
Parasympathetic impulses to heart (through vagus)
Sympathetic through spinal cord/PNS to all arteries, arterioles and veins
Vasoconstrictor area
SNS vasoconstrictor neurons throughout spinal cord
Vasodilator area
Inhibit vasoconstrictor area
Sensory area
Receives signals from vagus & glossopharyngeal nerves
Regultes vasoconstrictor & vasodilator areas
Vasomotor Tone
Continuous signals from vasoconstrictor area – sympathetic tone
Sympathetic (lateral)
Increases heart rate & contractility
Generally increase when vasoconstriction occurs
Generally decrease when vasoconstriction inhibited
Parasympathetic (medial)
Decreases heart rate (vagus nerve)
Higher nervous centers can influence vasomotor center
Pons
Midbrain
Diencephalon
Hypothalamus – powerful regulator
Cerebral cortex
Vasoconstrictor neurotransmitter
NE
Adrenal Medulla Innervation
Causes medulla to release Epi and NE
Generally cause vasoconstriction
In tissues with β2 receptors, cause vasodilation
MAP can be increased by
Constricting most arterioles
Increase TPR and therefore CO
Constricting large vessels
Increase venous return and therefore CO
Increasing HR and contractility
Increase CO
These can occur within seconds
Exercise/fright
Constricting most arterioles
Increase TPR and therefore CO
Constricting large vessels
Increase venous return and therefore CO
Increasing HR and contractility
Increase CO
These can occur within seconds
Exercise/fright
Cardiovascular Reflexes & Responses
Vasovagal syncope
Baroreceptor reflex
Ischemic response
Atrial & pulmonary artery reflexes
Bainbridge reflex
Baroreceptor Reflex
Important in short term BP regulation
Increase in BP stretches baroreceptors
Increases the number of impulses from carotid sinus increases which results in
Inhibition of the vasoconstrictor
Activation of the vagal center
Causes AP through afferent neurons
Hering’s and glossopharyngeal or vagus
Integrating center is vasomotor center in medulla
Baroreceptors respond to changes in arterial pressure
Carotid sinus baroreceptors respond to pressures between 60 and 180 mmHg
Baroreceptors reflex is most sensitive at a pressure of ~100mmHg
Maintains relatively constant pressure despite changes in body posture
Moving from a supine to a standing position results in
an increase in heart rate
an increase in total peripheral resistance
constriction of veins
Baroreceptor Reflex Functions
Oppose changes (increase or decrease) in BP, reducing daily fluctuations
Adapt, so not helpful in long-term regulation of BP
Chemoreceptors
Remember chemoreceptors located in carotid bodies and aorta?
Their activation also activates vasomotor center in medulla to increase sympathetic stimulation
CNS Ischemic Response
CNS Ischemic response is activated in response to cerebral ischemia
Reduced cerebral blood flow causes CO2 buildup which stimulates vasomotor center thereby increasing arterial pressure
Atrial and Pulmonary Reflexes
Receptors in atria and pulmonary arteries minimize arterial pressure changes in response to changes in blood volume
Increases in blood volume activate receptors
Decrease ADH
Increasing GFR
Decrease Na reabsorption
And H2O
Bainbridge Reflex
Prevents damming of blood in veins, atria, and pulmonary circulation
Increase in atrial pressure increases heart rate
Stretch of atria sends signals to VMC via vagal afferents to increase heart rate and contractility
Components of Blood
Plasma
Cellular elements
Red blood cells (RBCs)/erythrocytes
White blood cells (WBCs)/leukocytes
Platelets/thrombocytes
Plasma
Aqueous solution
Proteins
Enzymes
Hormones
Nutrients
Ions
Gases
Describe the basic composition of the fluid & cellular portions of blood.
The basic components of blood are :
①Plasma
↳ an aqueous solution with nutrients , gases ,
-Ions , and proteins (hormones 1- enzymes)
②
cellular-elements RBCs
↳WBCS
↳Platelets : cell fragments
Requirements for RBC Production
Erythropoeitin
Vitamin B12
Folic acid
Iron
Normal hemoglobin formation
Erythropoietin
Hormone released from kidney in response to low renal oxygenation (also produced in liver)
Red cell production increases within 24 hours
Erythropoietin life span is 4-12 hours
Increase in red cell number in 5 days
Vitamin B12 & Folic Acid
Required for final maturation of RBCs
Required for DNA synthesis
Vitamin B12
Dietary Sources: mostly animal proteins; especially high in fish
Absorption: requires intrinsic factor, produced by the stomach
Cells in the ileum contain intrinsic factor receptors
Storage: liver (can store >3 years’ worth)
Deficiency: due to lack of vitamin B12 in the diet or lack of absorption due to insufficient intrinsic factor
Folic Acid
Dietary Sources: liver; dark, leafy greens; other vegetables and fruits
Storage: liver
Deficiency: malnutrition; intestinal issues that prevent absorption
Iron
Necessary for oxygen to be able to bind to the hemoglobin (and other things in body)
~ 10% in food absorbed, few mg/day
loss 1 mg/day males average
menstruating women additional 14 mg/period loss
duodenum and upper jejunum major site absorption
Absorption enhanced by meat, Vitamin C, HCl
Inhibited by carbonates, tannate (tea), oxalate (spinach, rhubarb), phosphates (vegetables)
Excess iron is stored in liver
Mechanism of absorption (throughout small intestine)
Requires substance produced by liver into bile
This is secreted into the duodenum
It then binds to iron, created transferrin
Intestinal cells contain receptors for transferrin, bringing the complex into the cell
Transferrin is moved out of the cell and into the blood
Hemoglobin
Protein containing 4 hemoglobin chains, each of which contains:
Globin chains
Heme molecules
Each contains one atom of iron, for a total of 4 iron atoms/hemoglobin
Each atom of iron can bind on molecule of O2, for a total of 4 oxygen molecules/hemoglobin
Abnormal Hemoglobin
Generally inherited
Sickle-cell anemia
Thalassemia
Others
Genetic mutation results in abnormal protein with reduced function
Regulation of RBC Numbers
Balance between production and destruction
~ 1% produced/day ~ 1% destroyed/day
Produced in bone marrow
sternum, pelvis, vertebrae, ribs
Life span ~100 days before starting to degrade and being ingested by macrophages in the spleen.
Describe the physical characteristics, production, function, and life span of red blood cells (erythrocytes).
Physical : flat , biconcave , nd nucleus or organelles
4 heme groups which bind to Oz v4 help of iron
Production: from stem cells in bone marrow
↳ NEET
① erythropoei fin :
hormone from kidney 9 in lack of Oz
② vitamin Biz: found in animals (protein
③ folic acid : liver
④ iron : needed for 02 → hemoglobin quit.C
⑤ hemoglobin : 4 heme groups binds 402s
Function :
transport Oz 1- Coz
Life Span :3-4 months , recycled by spleen
100 days
