exam 3 ch 13-17 Flashcards
Battlefield trauma victims who have lost large volumes of blood often express a craving to drink water. Why?
- Due to severe dehydration and blood volume loss.
- Triggered by sympathetic division of ANS: increases heart rate and blood pressure to maintain perfusion to vital organs, while simultaneously suppressing functions such as digestion to conserve energy
- Thirst sensation encourages fluid intake to restore homeostasis.
You’ve stayed up all night trying to meet a term paper deadline. You now are typing frantically, keeping one eye on the paper and the other on the clock. How has the periventricular zone of the hypothalamus orchestrated your body’s physiological response to this stressful situation? Describe in detail.
- Orchestrates HPA axis activation.
- Releases CRH into hypothalamo-pituitary portal circulation.
- Stimulates anterior pituitary to release ACTH.
- Results in cortisol release from adrenal cortex.
An “Addisonian crisis” describes a constellation of symptoms that include extreme weakness, mental confusion, drowsiness, low blood pressure, and abdominal pain. What causes these symptoms and what can be done to treat them?
- Symptoms: extreme weakness, mental confusion, low blood pressure, abdominal pain.
- Caused by acute adrenal insufficiency (lack of cortisol and aldosterone).
- Treatment: Immediate administration of glucocorticoids and mineralocorticoids.
Why is the adrenal medulla often referred to as a modified sympathetic ganglion? Why isn’t the adrenal cortex included in this description?
- Responds to preganglionic sympathetic neurons.
- Releases catecholamines directly into bloodstream.
- Not part of sympathetic ganglia.
- Adrenal cortex produces steroid hormones, not neurotransmitters.
A number of famous athletes and entertainers have accidentally killed themselves by taking large quantities of cocaine. Usually the cause of death is heart failure. How would you explain the peripheral actions of cocaine?
- Blocks neurotransmitter reuptake (dopamine, norepinephrine, serotonin).
- Leads to excessive adrenergic receptor stimulation.
- Causes vasoconstriction, increased heart rate, elevated blood pressure.
- Can result in heart failure due to strain on the heart.
How do the diffuse modulatory and point-to-point synaptic communication systems in the brain differ? List four ways.
- Diffuse modulatory: Releases neurotransmitters diffusely, modulates overall neural activity.
- Point-to-point: Specific pathways and synapses for precise transmission.
- Diffuse systems regulate global brain states, while point-to-point systems mediate specific functions.
- Anatomical, neurotransmitter, and functional differences between the two.
Under what behavioral conditions are the noradrenergic neurons of the locus coeruleus active?
The noradrenergic neurons of the ANS?
- Active under stress, arousal, vigilance.
- Regulation of attention, arousal, sleep-wake cycles, mood.
- Innervate various brain regions.
- Prepare body for “fight or flight” response in ANS.
Which type of synaptic connection restricts synaptic communication?
a) Point-to-point
What brain area regulates body temperature and blood composition?
Secretory hypothalamus
Which hormone is released by the hypothalamus during the stress response?
c) Corticotropin-releasing hormone (CRH)
Which division of the autonomic nervous system is responsible for the “fight or flight” response?
b) Sympathetic division
Which neurotransmitter is released by the parasympathetic nervous system?
c) Acetylcholine
Which brain region is involved in regulating attention, arousal, and sleep-wake cycles?
c) Locus Coeruleus
Which component of the nervous system is responsible for maintaining homeostasis?
a) Secretory hypothalamus
What neurotransmitter is primarily responsible for the fast excitatory postsynaptic potentials (EPSPs) at preganglionic terminals of the autonomic nervous system?
a) Acetylcholine
Which brain region integrates sensory information from internal organs and coordinates autonomic output?
b) Nucleus of solitary tract
Which neurohormone released by the posterior pituitary gland regulates blood volume and salt concentration?
c) Vasopressin (ADH)
Which neurotransmitter is primarily released by the parasympathetic nervous system postganglionic neurons?
c) Acetylcholine
Which division of the autonomic nervous system is responsible for regulating physiological processes involved in transport and digestion of food?
c) Enteric division
Which diffuse modulatory system is particularly involved in the regulation of sleep-wake cycles and mood?
b) Serotonergic Raphe Nuclei
What is the primary function of the dorsal thalamus compared to the hypothalamus?
b) Integration of sensory information
How is movement initiated? What triggers it?
- In response to environmental stimuli such as cold temperatures, the lateral hypothalamus initiates motivation to actively seek or generate warmth to maintain homeostasis.
- Elevated leptin levels activate arcuate neurons in the hypothalamus, leading to the release of anorectic peptides such as αMSH and CART. These peptides induce responses such as activation of the sympathetic nervous system and inhibition of orexinergic neurons in the lateral hypothalamus, which can influence movement behavior.
- Ghrelin, released when the stomach is empty, activates NPY- and AgRP-containing neurons in the arcuate nucleus of the hypothalamus, potentially affecting movement behavior.
- Dopamine, particularly in the mesocorticolimbic system, plays a crucial role in motivation and reward processing.
Why do we eat?
- Eating is associated with reinforcement and reward mechanisms mediated by neurotransmitters such as dopamine.
- Drugs that block dopamine receptors reduce self-stimulation, indicating the involvement of dopamine in reinforcing behaviors like eating.
- Eating is driven by both hedonic (liking) and motivational (wanting) factors.
- Leptin influences feeding behavior through activation of arcuate neurons in the hypothalamus, which release peptides that affect appetite and energy expenditure.
What chemicals and what neurons are mediating feeding behaviors?
Hormones:
Leptin: Secreted by adipose tissue, leptin regulates body mass, appetite, and energy expenditure. Elevated levels of leptin activate specific neurons in the hypothalamus, leading to the release of anorectic peptides and influencing feeding behavior.
Ghrelin: Released when the stomach is empty, ghrelin activates neurons in the hypothalamus, including those containing neuropeptide Y (NPY) and agouti-related peptide (AgRP), which stimulate appetite and food intake.
Neuropeptides and Neurotransmitters:
Neuropeptide Y (NPY) and Agouti-Related Peptide (AgRP): These peptides, released by neurons in the arcuate nucleus of the hypothalamus, promote feeding behavior and increase appetite.
Melanin-Concentrating Hormone (MCH) and Orexin: Neurons in the lateral hypothalamus containing MCH and orexin stimulate feeding behavior and are involved in the initiation of motivation to seek food.
Alpha-Melanocyte-Stimulating Hormone (αMSH) and Cocaine- and Amphetamine-Regulated Transcript (CART): These peptides, released by neurons in the arcuate nucleus of the hypothalamus, act as anorectic peptides, suppressing appetite and reducing food intake.
Dopamine: Dopaminergic pathways, particularly those originating from the ventral tegmental area (VTA) and projecting to the forebrain, play a role in motivation, reward, and reinforcement associated with feeding behavior.
A surgical approach to reducing excessive body fat is liposuction—the removal of adipose tissue. Over time, however, body adiposity usually returns to precisely the same value as before surgery. Why does liposuction not work permanently? Contrast this with the effect of gastric surgery to treat obesity.
- Liposuction removes adipose tissue surgically, but over time, body adiposity returns to its previous level.
- Adipose tissue is a dynamic organ involved in energy storage and metabolism.
- Liposuction removes fat cells, but if energy intake exceeds expenditure, remaining fat cells can expand, leading to weight regain.
- Liposuction does not address underlying factors contributing to obesity, such as diet, exercise, and hormonal regulation.
- Gastric surgery alters the anatomy of the gastrointestinal tract, leading to changes in appetite, food intake, and energy balance.
- Procedures like gastric bypass or sleeve gastrectomy reduce stomach size, alter digestion, and affect gut hormones involved in appetite regulation.
- These surgeries result in more sustainable weight loss by influencing hormonal and neural signals that control hunger and satiety.
Bilateral lesions of the lateral hypothalamus lead to reduced feeding behavior. Name three types of neurons, distinguished by their neurotransmitter molecules, which contribute to this syndrome.
- Neurons containing Melanin-Concentrating Hormone (MCH)
- Neurons containing Orexin (also known as hypocretin)
- Neurons containing Neuropeptide Y (NPY) and Agouti-Related Peptide (AgRP)
What neurotransmitter agonists and antagonists would you design to treat obesity? Consider drugs that could act on the neurons of the brain as well as drugs that could act on the peripheral nervous system.
Agonists:
- Melanocortin receptor agonists (e.g., MC4R agonists) to suppress appetite and increase energy expenditure.
- Serotonin (5-HT) receptor agonists to promote satiety and reduce food intake.
- Dopamine receptor agonists to modulate reward pathways and reduce cravings.
Antagonists:
- Cannabinoid receptor antagonists to decrease appetite and food intake.
- Ghrelin receptor antagonists to reduce hunger signals.
- Opioid receptor antagonists to diminish reward-related eating behaviors.
Name one way the axons of the vagus nerve might stimulate feeding behavior and one way they inhibit it.
- Stimulation: Axons of the vagus nerve can transmit hunger signals to the brainstem and hypothalamus, promoting feeding behavior.
- Inhibition: Vagal input can also convey signals of satiety from the gastrointestinal tract to the brain, inhibiting further food intake.
What does it mean, in neural terms, to be addicted to chocolate? How could chocolate elevate mood?
- Addiction to chocolate involves activation of reward pathways in the brain, particularly the mesolimbic dopamine system.
- Chocolate contains compounds such as phenylethylamine and theobromine, which can enhance dopamine release and produce feelings of pleasure and reward.
- Consuming chocolate may elevate mood by increasing serotonin levels in the brain, leading to mood enhancement and temporary relief from stress or anxiety.
Compare and contrast the functions of these three regions of the hypothalamus: the arcuate nucleus, the subfornical organ, and the vascular organ of the lamina terminalis
- Arcuate Nucleus: Contains neurons involved in appetite regulation, sensing peripheral signals of energy balance, and releasing orexigenic and anorexigenic neuropeptides.
- Subfornical Organ: Acts as a circumventricular organ, sensing changes in blood composition and influencing thirst and fluid balance.
- Vascular Organ of the Lamina Terminalis: Involved in regulating cardiovascular function, fluid balance, and responses to stress and inflammation
What is the primary function of the lateral hypothalamus in motivated behavior?
c) Regulating feeding behavior
Which of the following is a component of the neuronal response involved in maintaining homeostasis?
a) Humoral response
In the long-term regulation of feeding behavior, what hormone plays a key role in regulating body mass and energy expenditure?
c) Leptin
Which hypothalamic syndrome is associated with obesity and is related to leptin signaling?
b) Ventromedial hypothalamic syndrome
What neurotransmitters are released by arcuate neurons in response to elevated leptin levels?
b) α-Melanocyte-stimulating hormone (αMSH) and CART
Which phase of the short-term regulation of feeding is characterized by hunger signals initiated by the brain?
a) Cephalic phase
What hormone is released when the stomach is empty, activating neurons in the arcuate nucleus to stimulate appetite?
c) Ghrelin
What is the primary role of the vagus nerve in regulating feeding behavior?
c) Conveying satiety signals
What neurotransmitter is associated with reinforcement and reward in the context of eating behavior?
c) Dopamine
Dopamine-depleted animals are likely to:
a) Overeat but not enjoy food
b) Have reduced appetite and food intake
c) Seek food actively but not consume it
d) Experience cravings for specific foods
b) Have reduced appetite and food intake
What neurotransmitter is implicated in mood elevation and is influenced by changes in blood tryptophan levels?
b) Serotonin
Which region of the hypothalamus is primarily involved in controlling feeding behavior?
a) Arcuate nucleus
What peptide hormones are involved in the regulation of feeding behavior by lateral hypothalamic neurons?
a) Melanin-concentrating hormone (MCH) and Orexin
What neurotransmitter is released by arcuate neurons in response to decreased leptin levels, stimulating appetite?
c) Neuropeptide Y (NPY)
Which hormone is associated with the feeling of fullness during the gastric phase of feeding regulation?
d) Cholecystokinin (CCK)
Which phase of short-term feeding regulation involves the release of insulin?
c) Substrate phase
What term describes the drive reduction aspect of eating behavior?
d) Wanting
Which neurotransmitter system is primarily involved in the mesocorticolimbic dopamine pathway associated with motivation and reward in eating behavior?
d) Dopaminergic
What neurotransmitter is often implicated in eating disorders and is associated with mood regulation?
a) Serotonin
In the context of feeding behavior, what does the lipostatic hypothesis propose?
c) The control of body fat levels by a feedback mechanism involving leptin
what are the concepts of motivated behavior and its relationship to maintaining homeostasis
Motivated behavior refers to actions and behaviors driven by internal needs, desires, or goals.
Motivated behaviors can vary widely and include actions such as seeking food, water, shelter, social interaction, or reproduction.
Motivated behaviors are closely linked to homeostasis as they are often aimed at restoring equilibrium or meeting biological needs necessary for survival.
For example, when the body experiences deviations from homeostatic set points (e.g., low body temperature), motivated behaviors such as seeking warmth (shivering) or food (increased appetite) are activated to restore balance.
Unconscious Reflexes:
Definition:
Unconscious reflexes are automatic, involuntary responses to sensory stimuli that occur without conscious awareness or cognitive processing.
Examples include the pupillary reflex, withdrawal reflex, and knee-jerk reflex.
Voluntary Movements:
Definition
Voluntary movements are purposeful actions initiated and controlled consciously by the individual.
Examples include reaching for an object, walking, speaking, and typing.
Motivated Behaviors:
Definition
Motivated behaviors are goal-directed actions driven by internal needs, desires, or goals.
Motivated behaviors are influenced by internal states such as hunger, thirst, and arousal, as well as external stimuli and environmental cues.
Motivated behaviors can vary widely and include actions such as seeking food, water, shelter, social interaction, or reproduction.
Functions of Hypothalamus in homeostasis:
Regulation of Body Temperature
- In response to heat loss (e.g., exposure to cold environment), the hypothalamus triggers mechanisms such as shivering, vasoconstriction (to reduce heat loss from the skin), and increased metabolic rate to generate heat.
- in response to heat gain (e.g., exposure to heat or exercise), the hypothalamus initiates mechanisms such as sweating, vasodilation (to promote heat loss from the skin), and inhibition of metabolic heat production.
Functions of Hypothalamus in homeostasis:
Regulation of Blood Composition:
the hypothalamus secretes corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH, in turn, stimulates the adrenal glands to secrete cortisol, which plays a crucial role in metabolism and stress response.
Functions of Hypothalamus in homeostasis:
Regulation of Fluid Balance:
The hypothalamus regulates fluid balance by controlling thirst and kidney function.
the hypothalamus influences kidney function by releasing vasopressin (antidiuretic hormone), which regulates water reabsorption in the kidneys to maintain fluid balance.
Humoral Response:
Definition
The humoral response involves the release of hormones into the bloodstream in response to changes in the internal environment to maintain homeostasis.
Humoral Response:
Characteristics:
These hormones travel through the bloodstream to target organs or tissues, where they exert their effects by altering cellular activities or gene expression.
Hormonal responses are often slower but more sustained compared to neural responses.
Example: When blood glucose levels rise after a meal, the pancreas releases insulin, which promotes glucose uptake by cells, thereby lowering blood glucose levels.
Visceromotor Response:
Definition
The visceromotor response involves autonomic nervous system (ANS) regulation of visceral functions to maintain homeostasis.
Visceromotor Response:
Characteristics
Visceromotor responses are coordinated by the hypothalamus, brainstem nuclei, and spinal cord circuits in response to sensory inputs and hormonal signals.
Sympathetic activation typically increases physiological arousal and prepares the body for action (fight-or-flight), while parasympathetic activation promotes relaxation and conservation of energy (rest-and-digest).
Example: During stress, sympathetic activation increases heart rate, blood pressure, and glucose release, while inhibiting digestive functions.
Somatic Motor Response:
Definition
The somatic motor response involves voluntary control of skeletal muscles to maintain homeostasis.
Somatic Motor Response:
characteristics
Somatic motor responses are under conscious control and involve voluntary movements such as walking, reaching, and speaking.
The primary motor cortex in the brain initiates voluntary movements, sending signals via the corticospinal tract to motor neurons in the spinal cord, which innervate skeletal muscles.
Somatic motor responses enable adaptive behaviors and motor skills necessary for interacting with the external environment.
Example: Adjusting clothing or seeking shelter to regulate body temperature, or consciously drinking water to maintain hydration levels.
Describe the long-term regulation of feeding behavior, including the role of energy balance, prandial states, and the lipostatic hypothesis.
- When energy intake matches energy expenditure, the body maintains a stable weight and composition.
- Imbalances in energy balance, such as excessive energy intake or reduced energy expenditure, can lead to weight gain or loss over time.
- Prandial states refer to the metabolic states of the body in response to feeding (prandium means “meal” in Latin).
- Anabolism occurs during the prandial state, characterized by nutrient absorption and storage. This phase involves the synthesis of complex molecules from simpler ones, such as the conversion of glucose into glycogen or triglycerides for storage.
- The lipostatic hypothesis proposes that the brain monitors and regulates body fat levels to maintain energy homeostasis.
According to this hypothesis, adipose tissue releases signaling molecules called adipokines, with leptin being a key hormone. - The lipostatic hypothesis suggests that leptin serves as a feedback signal to regulate food intake and energy balance based on the body’s long-term energy stores.
Explain the significance of leptin in regulating body mass, appetite, and energy expenditure
- The main function of leptin is to signal the brain about the body’s long-term energy stores, specifically the amount of adipose tissue present.
- When fat stores are high, adipose tissue releases more leptin into the bloodstream. Elevated leptin levels act on specific receptors in the hypothalamus, signaling a state of energy abundance.
- Leptin plays a key role in regulating appetite by influencing the activity of neurons in the hypothalamus, particularly in the arcuate nucleus.
- Leptin receptors are present on two types of neurons in the arcuate nucleus: pro-opiomelanocortin (POMC)/cocaine- and amphetamine-regulated transcript (CART) neurons and neuropeptide Y (NPY)/agouti-related protein (AgRP) neurons.
- Activation of POMC/CART neurons by leptin leads to the release of α-melanocyte-stimulating hormone (α-MSH), which suppresses appetite and promotes energy expenditure.
- Conversely, activation of NPY/AgRP neurons by low leptin levels stimulates appetite and reduces energy expenditure, promoting weight gain.
- In addition to its effects on appetite regulation, leptin also acts on the sympathetic nervous system (SNS) to increase thermogenesis (heat production) and basal metabolic rate.
- By stimulating sympathetic outflow, leptin enhances the activity of brown adipose tissue (BAT), which generates heat through uncoupled mitochondrial respiration, thereby increasing energy expenditure.
what are the implications of lateral hypothalamic syndrome (anorexia) and ventromedial hypothalamic syndrome (obesity) in relation to leptin signaling.
In the context of leptin signaling:
Normally, leptin acts on neurons in the hypothalamus, including those in the lateral hypothalamus, to suppress appetite and reduce food intake when fat stores are sufficient.
However, in individuals with lateral hypothalamic syndrome, leptin signaling may be disrupted due to damage or dysfunction of hypothalamic neurons.
This disruption can lead to impaired sensitivity to leptin’s appetite-suppressing effects, resulting in a persistent state of reduced appetite and decreased food intake characteristic of anorexia.
Leptin acts on neurons in various hypothalamic nuclei, including the ventromedial hypothalamus, to regulate energy balance by suppressing appetite and increasing energy expenditure.
However, in individuals with ventromedial hypothalamic syndrome, leptin signaling may be impaired due to damage or dysfunction of hypothalamic neurons.
This impairment can lead to reduced sensitivity to leptin’s appetite-suppressing effects and decreased energy expenditure, contributing to increased appetite and weight gain characteristic of obesity.
Explain the Cephalic Phase:
Initiation: Begins with the anticipation of food or sensory stimuli associated with food intake, such as sight, smell, taste, or even the thought of food.
Hunger Response: Sensory cues related to food activate neural pathways in the brain, including the hypothalamus and brainstem, triggering the cephalic phase response.
Neural Regulation: Activation of the cephalic phase involves neural signals originating from higher brain centers, such as the cerebral cortex and limbic system, which stimulate appetite and prepare the body for food intake.
Hormonal Release: Release of hormones such as ghrelin, often referred to as the “hunger hormone,” which increases appetite and prepares the digestive system for food ingestion.
explain the Gastric Phase:
Initiation: Begins upon the actual consumption of food and the entry of food into the stomach.
Distension Response: Stretch receptors in the stomach wall detect the presence of food and signal the brain via the vagus nerve (cranial nerve X) about gastric distension.
Hormonal Release: Gastric distension triggers the release of hormones such as cholecystokinin (CCK) from the small intestine. CCK acts on receptors in the brain to reduce appetite and promote satiety.
Insulin Release: Food ingestion also stimulates the release of insulin from pancreatic β-cells in response to rising blood glucose levels, which further promotes satiety and reduces appetite.
explain the substrate phase
Initiation: Begins after the absorption of nutrients from the gastrointestinal tract into the bloodstream, which occurs during digestion and metabolism of ingested food.
Metabolic Responses: Nutrients such as glucose, amino acids, and fatty acids derived from ingested food are metabolized by various tissues in the body to meet energy demands and maintain metabolic homeostasis.
Insulin Regulation: During the substrate phase, insulin levels remain elevated to facilitate the uptake of glucose by peripheral tissues, promote glycogen synthesis, and suppress gluconeogenesis, contributing to the termination of feeding behavior.
Integration: Metabolic signals from nutrient metabolism, including changes in blood glucose and fatty acid levels, are integrated with neural and hormonal signals to regulate appetite and feeding behavior, maintaining energy balance.
Discuss the relationship between neurotransmitter systems (e.g., serotonin) and mood regulation in the context of eating disorders.
Role of Serotonin: Serotonin, a neurotransmitter primarily synthesized in the brain and gastrointestinal tract, plays a crucial role in regulating mood, emotions, and behavior. It is involved in mood stabilization, anxiety reduction, and promoting feelings of well-being and satiety.
Impact on Feeding Behavior: Changes in serotonin levels and activity can influence feeding behavior and appetite regulation. For example, alterations in serotonin signaling may lead to appetite dysregulation, increased food cravings, or decreased motivation to eat, contributing to disordered eating patterns seen in individuals with eating disorders.
Compare and contrast the functions of key hypothalamic nuclei involved in feeding behavior, such as the arcuate nucleus, lateral hypothalamus, and ventromedial nucleus.
Arcuate Nucleus:
- Contains NPY/AgRP neurons that promote feeding and inhibit energy expenditure.
- Houses POMC neurons that suppress appetite and stimulate energy expenditure.
Lateral Hypothalamus (LH):
- Initiates and maintains feeding behavior, containing orexin/hypocretin-producing neurons.
- Promotes hunger, arousal, and food-seeking behavior.
Ventromedial Nucleus (VMH):
- Regulates satiety and energy expenditure.
- Contains neurons that inhibit feeding and promote satiation.
Which part of the brain plays a role in regulating both reproduction and eating behaviors?
Hypothalamus
Which hormone receptor distribution differs between prairie voles and meadow voles?
a) Oxytocin
Differentiate conscious control by the cerebral cortex from subconscious regulation
Conscious Control by the Cerebral Cortex:
Voluntary Regulation
Awareness and Intentionality
Subconscious Regulation:
Automatic Processes
Efficiency and Speed: (heartbeat/ digestion)
What is the role of the motor system?
b) Coordination of muscle movements
Which part of the nervous system is responsible for generating coordinated muscle contractions?
a) Spinal cord
Where are lower motor neurons located?
c) Ventral horn of the spinal cord
Which muscles are controlled by lower motor neurons located in the ventral horn?
a) Axial muscles
What is a motor unit?
c) A motor neuron and all the muscle fibers it innervates
Which type of muscle fiber is slow to contract and can sustain contraction?
a) Red muscle fibers
What happens during the plateau phase of the sexual response cycle?
c) Peak of sexual pleasure is reached
