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Questions and Answers
What happens to enzyme activity at high temperatures when excessive heat is generated?
What happens to enzyme activity at high temperatures when excessive heat is generated?
- Oxidative stress is reduced due to increased enzyme efficiency.
- Enzymes become more rigid and retain their functionality.
- Proteins may denature and lose their functional shape. (correct)
- Enzyme activity increases linearly with temperature.
How does the body size of species relate to their thermal resistance?
How does the body size of species relate to their thermal resistance?
- Smaller species are generally more thermally resistant.
- Larger species are typically more hypoxia tolerant due to higher oxygen stores. (correct)
- Thermal resistance is independent of body size.
- Larger species lose heat more rapidly than smaller species.
What effect does low temperature have on enzymatic reactions?
What effect does low temperature have on enzymatic reactions?
- It increases the rate of reaction by lowering activation energy.
- It does not favor the reaction and prevents reaching activation energy. (correct)
- It enhances the rigidity of enzymes, increasing their specificity.
- It causes enzymes to denature, making them more effective.
What is the primary consequence of the Surface Area to Volume ratio (SA:V) in larger species?
What is the primary consequence of the Surface Area to Volume ratio (SA:V) in larger species?
What is the relationship between mass-specific metabolic rate and body size?
What is the relationship between mass-specific metabolic rate and body size?
What occurs when there is an increase in sodium (Na+) levels in the blood?
What occurs when there is an increase in sodium (Na+) levels in the blood?
How does the body respond to dehydration in terms of thirst motivation?
How does the body respond to dehydration in terms of thirst motivation?
What role does cortisol play in the osmoregulation of saltwater fish?
What role does cortisol play in the osmoregulation of saltwater fish?
What is the effect of prolactin on freshwater fish regarding osmoregulation?
What is the effect of prolactin on freshwater fish regarding osmoregulation?
How do diadromous fish such as salmon adapt to their varying salinity environments?
How do diadromous fish such as salmon adapt to their varying salinity environments?
What is the primary function of UCP1 in brown adipose tissue?
What is the primary function of UCP1 in brown adipose tissue?
What initiates the activation of UCP1 in response to cold stimuli?
What initiates the activation of UCP1 in response to cold stimuli?
How does torpor differ from hibernation?
How does torpor differ from hibernation?
What vascular adaptation helps to maintain core body temperature during cold exposure?
What vascular adaptation helps to maintain core body temperature during cold exposure?
Which group of mammals is suggested to have ancestral traits related to torpor?
Which group of mammals is suggested to have ancestral traits related to torpor?
Which physiological mechanism is NOT associated with daily heterothermy?
Which physiological mechanism is NOT associated with daily heterothermy?
What is the relationship between body size and fasting endurance regarding torpor in small and large species?
What is the relationship between body size and fasting endurance regarding torpor in small and large species?
What effect does the cold environment have on the metabolism of hibernators?
What effect does the cold environment have on the metabolism of hibernators?
What physiological change primarily prepares anadromous fish for migration from freshwater to seawater?
What physiological change primarily prepares anadromous fish for migration from freshwater to seawater?
How does the prolactin level change when migrating back to freshwater as adults?
How does the prolactin level change when migrating back to freshwater as adults?
What adaptation occurs over time to address the challenges faced during migration?
What adaptation occurs over time to address the challenges faced during migration?
Which design feature is specific to an open circulatory system?
Which design feature is specific to an open circulatory system?
What is the primary mechanism for blood perfusion in a closed circulatory system?
What is the primary mechanism for blood perfusion in a closed circulatory system?
Which structure primarily prevents backflow in the heart?
Which structure primarily prevents backflow in the heart?
What type of heart mechanism allows the atrium to empty before the ventricle contracts?
What type of heart mechanism allows the atrium to empty before the ventricle contracts?
What characteristic distinguishes a closed circulatory system from an open one?
What characteristic distinguishes a closed circulatory system from an open one?
What is the role of prostaglandins in pain perception?
What is the role of prostaglandins in pain perception?
Which of the following statements about gas messengers is true?
Which of the following statements about gas messengers is true?
What distinguishes neurosecretory cells from epithelial endocrine cells?
What distinguishes neurosecretory cells from epithelial endocrine cells?
What is the primary function of the adrenal cortex?
What is the primary function of the adrenal cortex?
How do direct acting hormones differ from tropic hormones?
How do direct acting hormones differ from tropic hormones?
Which statement best characterizes the stress response?
Which statement best characterizes the stress response?
What is one of the first physiological responses to acute stress?
What is one of the first physiological responses to acute stress?
Which of the following correctly describes the adrenal medulla's function?
Which of the following correctly describes the adrenal medulla's function?
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Study Notes
Enzyme Activity and Temperature
- Too high temperature (Tb) can denature proteins
- Too low temperature (Tb) slows down enzyme activity
Body Size and Homeothermy
- Larger species are more thermally resistant, fasting resistant, have more energy stores, and are more hypoxia tolerant
- Surface Law: smaller species have higher surface area to volume ratio, which leads to faster heat loss
- Mass-specific metabolic rate (MSMR) is higher in smaller species
- Smaller species have shorter fasting endurance
Thermogenesis
- Uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) allows protons to enter the mitochondrial matrix without generating ATP, producing heat
- GDP blocks UCP1 activity, resuming ATP synthesis
- Cold stimulus triggers the release of norepinephrine, which activates UCP1
- Acclimation can increase BAT and UCP1 levels
Thermoregulatory Mechanisms
-
Altering Tb-Ta gradient:
- Vasoconstriction reduces blood flow to extremities
- Countercurrent heat exchange: warm blood from the core transfers heat to veins, warming cold blood returning from extremities
-
Torpor/Fasting:
- Reversible state of reduced metabolic rate and body temperature
- Occurs when Ta is below lower critical temperature (LCT)
- Fasting endurance decreases with body size due to energy stores
- Small species have higher MSMR, allowing for torpor
-
Daily Heterothermy:
- Variation in MR over 24 hours
- Seen in small mammals and birds
-
Seasonal Endothermy:
- True hibernation:
- Dramatic reduction in MR and Tb
- Rely on body stores and cached food
- Seasonal lethargy:
- Inhibition of metabolism, allowing body temperature to drop to 30°C
- Estivation:
- Small reduction in Tb and MR to conserve resources
- True hibernation:
-
Regional endothermy:
- Active heating of specific organs
- Prostaglandins, generated by COX pathway, contribute to localized heat production
Gas Messengers
- Lipid-soluble molecules that act through paracrine signaling
- Short half-life
- Nitric oxide (NO) is a vasodilator produced by nitric oxide synthase
Control of Endocrine Secretions
-
Neurohemal organs contain neurosecretory cells, which release neurohormones
-
Pituitary gland:
- Posterior pituitary (neurohypophysis): releases hormones synthesized in the hypothalamus (AVP, CRH, oxytocin)
- Anterior pituitary (adenohypophysis): releases hormones synthesized by epithelial endocrine cells
-
Adrenal gland:
- Adrenal cortex: produces steroid hormones (aldosterone, CORT)
- Adrenal medulla: produces catecholamines (epinephrine, norepinephrine)
Stress Response
- Stress disrupts homeostasis and elicits physiological and behavioral responses
- Primary response:
- Increase in catecholamines and CORT
- Secondary response:
- Effects on target tissues, including gene expression and pathway activation
- Tertiary response:
- Changes in metabolism and anti-predator behavior
Osmoregulation
-
Dehydration:
- Angiotensin II triggers thirst by activating osmoreceptors in the brain
-
Increased sodium (Na+) levels:
- ANP is released to increase kidney filtration and decrease aldosterone production to reduce Na+ reabsorption
-
Diadromous fishes:
- Catadromous: spawn in saltwater (SW)
- Anadromous: spawn in freshwater (FW)
-
Hormonal regulation in fish:
- Cortisol (CORT): "Saltwater adapting hormone"
- Increases Na+/K+ ATPase activity to retain ions in SW
- Prolactin: "Freshwater adapting hormone"
- Decreases Na+/K+ ATPase activity to conserve ions in FW
- Cortisol (CORT): "Saltwater adapting hormone"
-
Smoltification:
- Physiological and morphological changes for anadromous fish transitioning from FW to SW
- CORT levels increase before migration to SW, as it is a slow-acting hormone
Circulatory System
- Open circulatory system:
- Single-chambered heart, hemolymph flows through vessels, sinuses, and lacunae
- Lower resistance, but slower flow
- Closed circulatory system:
- Blood remains within vessels, multi-chambered heart
- Higher resistance, but faster flow
- Heart:
- Primary mechanism for blood circulation
- Other mechanisms: elastic recoil of arteries, smooth muscle contraction, skeletal muscle movement
- Valves: prevent backflow
- Pacemaker: sets heart rhythm
- Myocardium: heart muscle, regulates force of heartbeat
- Axillary hearts: provide localized blood flow
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