baroreflex/dive refley Flashcards
What are the two main control systems for maintaining blood pressure?
The two main control systems for maintaining blood pressure are:
- Local control of capillary flow, operated by chemoreceptors inside arterioles.
- Nervous and endocrine control on the heart, arteries, and veins.
Describe the mechanisms involved in tissue perfusion when metabolic activity increases.
When tissue becomes metabolically active, it consumes more oxygen and produces more carbon dioxide. This triggers two simultaneous mechanisms:
- Local control: Chemoreceptors inside arterioles detect changes in oxygen and carbon dioxide levels, leading to the relaxation of capillary sphincters and arteriolar vasodilation.
- Nervous control: This involves the autonomic nervous system, specifically the sympathetic and parasympathetic divisions, which regulate heart rate, arterial tone, and venous return to enhance blood flow to metabolically active tissues.
How is the nervous system organized in bilateral animals, particularly in vertebrates?
In vertebrates, the nervous system comprises the central nervous system (CNS) and the peripheral nervous system (PNS), which further divides into:
- Afferent division: Carries sensory information from receptors to the CNS.
- Efferent division: Transmits instructions from the CNS to effector organs. It includes the somatic nervous system (SNS) and the autonomic nervous system (ANS), the latter further divided into sympathetic and parasympathetic divisions.
Differentiate between sympathetic and parasympathetic nerve fibers based on their origins and neurotransmitters.
- Sympathetic nerve fibers originate from nuclei in the thoracic and lumbar regions of the spinal cord. They release acetylcholine at preganglionic synapses and norepinephrine at postganglionic synapses.
- Parasympathetic nerve fibers arise from nuclei in the brain stem and sacral region of the spinal cord. They release acetylcholine at both preganglionic and postganglionic synapses.
What are baroreceptors, and where are they located in mammals?
Baroreceptors are specialized sensory nerve endings located in the aortic arch and carotid sinuses. They detect changes in blood pressure and stretch of arterial walls. Baroreceptors in the carotid sinuses are crucial for regulating blood pressure to the brain.
Describe the physiological response during a hypertensive episode.
During a hypertensive episode, increased blood pressure triggers the activation of the parasympathetic nervous system. This leads to the release of acetylcholine, which decreases heart rate through muscarinic receptors in the SA node, ultimately reducing blood pressure.
Explain the physiological response during a hypotensive episode.
In a hypotensive episode, the sympathetic nervous system is activated, leading to the release of norepinephrine. Norepinephrine increases heart rate, myocardial contractility, and vasoconstriction, ultimately raising blood pressure.
What are the main types of adrenergic receptors involved in blood pressure regulation?
The main types of adrenergic receptors are:
- α1 receptors (activators)
- β1 receptors (activators)
- α2 receptors (inhibitors)
- β2 receptors (inhibitors)
Their activation or inhibition influences vascular tone and cardiac function, thereby affecting blood pressure.
How is blood volume regulated in the body?
Blood volume is primarily regulated by renal mechanisms, including direct and indirect controls.
- Direct control involves atrial stretch receptors releasing atrial natriuretic peptide (ANF) to increase diuresis and sodium excretion.
- Indirect control involves osmoreceptors in the hypothalamus regulating vasopressin secretion to adjust water reabsorption and diuresis.
What is the dive reflex, and how does it function in marine mammals?
The dive reflex is an adaptation in marine mammals that redirects blood flow to vital organs during prolonged submersion. It involves
- arteriolar vasoconstriction
- bradycardia (decreased heart rate)
- and increased vasoconstriction mediated by chemoreceptors and mechanoreceptors
ensuring oxygen supply to essential tissues during diving.
Name some adaptations in marine mammals for prolonged submersion.
Marine mammals such as seals have adaptations including
- increased blood volume
- high hematocrit values
- a well-developed heart
- elastic aortic bulbus and retes mirabilis to buffer pressure changes and prevent decompression sickness
What neurotransmitters are involved in the autonomic nervous system, and how do they differ in their effects?
- Acetylcholine: Released by both sympathetic and parasympathetic preganglionic fibers. In the sympathetic nervous system, it binds to nicotinic receptors at ganglia, while in the parasympathetic system, it binds to nicotinic receptors at ganglia and muscarinic receptors at target organs. Overall, acetylcholine mediates synaptic transmission.
- Norepinephrine: Released by sympathetic postganglionic fibers. It primarily binds to adrenergic receptors at target organs, exerting excitatory effects.
What are the main roles of α1 und 2 and β1 und 2 adrenergic receptors in blood pressure regulation?
- α1 receptors: Activators that primarily bind to norepinephrine, causing vasoconstriction when stimulated.
- α2 receptors: Inhibitors that primarily bind to norepinephrine, modulating neurotransmitter release and contributing to blood pressure regulation.
- β1 receptors: Activators that equally bind to norepinephrine and epinephrine, increasing heart rate and contractility when stimulated.
- β2 receptors: Inhibitors that primarily bind to epinephrine, causing vasodilation when stimulated.
Describe the direct control mechanism for regulating blood volume.
- atrial stretch receptors detecting changes in blood volume
- Excessive blood volume triggers the release of atrial natriuretic peptide (ANF) into the bloodstream
- ANF acts on the kidneys to inhibit the secretion of renin and aldosterone
- leading to increased diuresis and sodium excretion
- thereby reducing blood volume and pressure
Describe the indirect control mechanism for regulating blood volume.
- involves osmoreceptors in the hypothalamus
- monitoring intercellular water levels
- Increased water levels suppress vasopressin (antidiuretic hormone) secretion from the posterior pituitary gland
- Reduced vasopressin levels decrease water reabsorption in the kidneys
- promoting diuresis and reducing blood volume and pressure