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Animal Physiology: Homeostasis > Week 5 > Flashcards

Week 5 Flashcards

1
Q

Variation in Blood flow requirements

A

Different blood flow based on metabolic need and support of special functions (kidneys)

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2
Q

Control of blood flow in the arterioles

A
  • Major site of resistance in cardiovascular system (where largest drop in pressure occurs)
  • Controlled by hormones and SNS
  • Highly muscularly allowing them contract and relax based on signals from local tissues
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3
Q

Feedback loop locally controlling blood flow

A
  • Decrease in O2 delivery or increase in tissue metabolism
  • Decrease in tissue O2
  • relaxation of arterioles
  • increase in tissue blood flow
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4
Q

Active hyperaemia in skeletal muscle

A

Skeletal muscle can rapidly increase metabolic rate during contraction, leading to rapid increases in blood flow
- increase in hematocrit concentration in blood also increases during contractions (mechanisms not fully understood but could involve changes in the endothelial surface layer (glycocalyx))

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5
Q

Relationship between muscle O2 delivery and muscle O2 consumption rate

A
  • Linear relationship
  • Slope is .6 meaning that there is a great increase in delivery relative to O2 consumption (extraction not as efficient)
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6
Q

Misconceptions in active hyperaemia mechanism

A

Common view:
- capillaries close and do not support blood flow at rest, open following contraction to support more flow
Scientific Observation:
- intravital microscopy has observed most capillaries already support some flow in resting skeletal muscle
New Observation:
- haematocrit within capillaries of resting muscle is much lower than the normal haematocrit in large vessels

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7
Q

Vasodilator Substances

A
  • Released by tissues when they experience low availability of O2 or other nutrients
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8
Q

What substances contribute to blood flow

A

CO2, H+, lactate, adenosine, adenosine phosphates
- CO2 and H+ play prominent roles in controlling local blood flow in the brain

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9
Q

Why is lactate a good signal for a need in increased blood flow?

A
  • Produced when no oxygen is available to enter citric acid cycle
  • Increase in ATP production when increase in energy -> meaning increase lactate production
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10
Q

Why is adenosine a good signal for a need in increased blood flow?

A
  • more ATP broken down with increased activity
  • when ATP production meets ATP breakdown, all adenosine is reuptaken into the cell
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11
Q

Communication between capillaries and arterioles

A
  • Endothelial cells can be hyperpolarized in response to local conditions
  • cells interconnected by gap junctions - electrical signals can be conducted along vasculature
  • endothelial cells in arterioles signal nearby smooth muscle and cause dilation
  • Paracrine pathways between successive neighboring endothelial cells may also contribute to communication between capillaries and upstream arterioles
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12
Q

Endothelium derived relaxation factors

A
  • Increase in blood flow causes shear stress
  • leads to release of NO (potent vasodilator)
  • microvasculature increase flow in larger upstream vessels
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13
Q

Hormones causing vasoconstriction

A
  • Norepinephrine
  • Epinephrine
  • Angiotensin II
  • Antidiuretic Hormone
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14
Q

Hormones causing vasodilation

A
  • Norepinephrine
  • Epinephrine
  • Bradykinin
  • Histamine
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15
Q

Where are the receptors that regulate arterial blood pressure located

A

Aortic arch and carotid arteries

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16
Q

Cardiovascular control Center

A
  • Located: Brainstem (medulla and pons)
  • Receive afferent neural information from sensory receptors and higher centers
  • Neurons innervated and control the SNS and PSN
17
Q

What are the higher centers that send information to the cardiovascular control center

A
  • Temporal
  • Orbital
  • Cingulate Gyrus
  • Motor
  • Reticular Substance
  • Mesencephalon
18
Q

SNS anatomy

A
  • Short pre-ganglion axon (Myelinated) going to sympathetic chain ganglion releasing ACh
  • Long post-ganglionic axon releasing NE to effector cell
  • Some SNS cells pass all the way to the adrenal medulla without synapsing and release ACh at AD
  • AD chromaffin cells then releases NE or dopamine into the blood stream
19
Q

PNS anatomy

A
  • Long lightly myelinated pre-ganglion axon that passes all the way to the target organ without synapsing releasing ACh
  • short unmyelinated post-ganglion axon releasing ACh to target organ
20
Q

SNS and PNS Neurochemistry

A

PRE-GANGLIONIC NEURONS
- ACh binds to Nicotinic ACh receptors
POST-GANGLIONIC NEURONS
- Parasympathetic system: ACh binds to Muscarinic ACh receptors
- Sympathetic system: NE binds to alpha or beta adrenergic NE receptors

21
Q

Arterial Baroreceptors

A
  • Sense blood pressure in aorta and carotid sinus
  • Baroreceptors are neurons with spray-type nerve endings that are embedded in the artery wall
  • Nerve endings depolarize when stretched (Glossopharyngeal in carotid sinus and vagus in aortic)
  • Baroreceptor axons project tp the brain and send afferent information to the cardiovascular control centers
22
Q

Action potential frequency in baroreceptors

A
  • Sensors are always active - baseline frequency
  • respond to change (phasic) in BP - most important for short-term regulation
  • AP frequency reflects afferent information
  • Increase in pressure = increase in AP frequency
  • Decrease in pressure = decrease in AP frequency
23
Q

Efferent pathways in baroreceptors

A
  • SNS neruons innervate the pacemaker and contractile cells in the heart (increase HR and contractility)
  • SNS innervates arterioles, which mostly posses alpha adrenergic receptors and constrict in response to SNS
  • Arterioles in select organs (heart) posses beta adrenergic and dilate in response to SNS stimulation
  • SNS innervates veins causing constriction, increasing venous return
  • PNS innervates pacemaker (decrease HR)
24
Q

Regulated changes in blood pressure

A
  • Locomotion or the stress response activate the SNS and increase BP
  • results in a changed setpoint
  • increase BP setpoint facilitate increase in systemic BF during periods of high metabolic activity

Animal Physiology: Homeostasis (12 decks)

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