Homeostasis, motivated behavior, and stress Flashcards
Homeostasis
the active process of maintaining a relatively stable, balanced internal environment.
Motivation
psychological process that induces or sustains a particular behavior.
Critical structures for motivated behavior
-Hypothalamus and associated pituitary gland
- Limbic system
- frontal lobe
Regulatory behavior
-Behavior motivated to meet the survival needs of the animal
-Controlled by homeostatic mechanisms, which involve the hypothalamus
ex. eating, temperature and salt regulation, waste elimination
Homeostatic Mechanism
Process that maintains critical body functions within a narrow, fixed range
Nonregulatory behavior
-Behavior unnecessary to meet the basic survival needs of the animal
-Not controlled by homeostatic mechanisms
-Most involve the frontal lobes more than the hypothalamus
Strongly influenced by external stimuli
ex. sex, aggression
Regulatory Function of the Hypothalamic Circuit
-Hypothalamus maintains homeostasis by acting on both the endocrine system and the autonomic nervous system.
-Influences behaviors selected by the limbic system
What motivated behaviors is the hypothalmus responsible for
Wide range of behaviors including heart rate, feeding, and sexual behaviors
Osmotic thirst
stimulated by high extracellular solute concentration.
ex. eating pizza
Hypovolemic thirst
stimulated by reduced extracellular volume
ex. blood loss
Osmosensory neurons
in the hypothalamus respond to changes in osmotic pressure
Aldosterone
steroid hormone that is released from the adrenal gland in response to thirst signals
-stimulates the kidneys to conserve Na+, aiding water retention.
Pituitary Gland
secretions control the activities of many other endocrine glands
associated with biological rhythms
Subfornical organ
-sensitive to angiotensin II
-stimulation strongly elicits drinking behavior
Posterior Pituitary
Neural tissue; continuation of the hypothalamus
Anterior Pituitary
Glandular tissue; synthesizes various hormones
Peptides that are released by the hypothalamus and act to increase or decrease the release of hormones from the
anterior pituitary
Three Regions of the Hypothalamus
Lateral region
Medial region
Paraventricular region
Vasopressin
aka anti-diuretic hormone
prevents urination to conserve water
Paraventricular region of the hypothalmus
produce oxytocin: released during intimate moments such as nurturing behavior, hugging, or sex; known as the bonding hormone.
Lateral Region of the hypothalmus
Contains nuclei and nerve tracts that connect the lower brainstem to the forebrain
Medial Forebrain Bundle (MFB)
-Tract that connects structures in the brainstem with various parts of the limbic system
-Forms the activating projections from the brainstem to the basal ganglia and frontal cortex
-Dopamine-containing fibers are involved in reward and therefore contribute to many motivated behaviors
Feedback Loops
Control the amount of hormone that is released
Hormones influence the hypothalamus to decrease secretion of releasing hormones
Neural Regulation
Other brain regions (e.g., limbic system and frontal lobes) influence hormone release
Excitatory and inhibitory influences exerted by cognitive activity can influence neurons in the periventricular region
Aphagia
-observed following lesions to the lateral hypothalamus
-failure to eat
Experiential Responses
Experience can alter the structure and function of hypothalamic neurons
Endotherms
generate most of their own heat through internal processes
Ectotherms
get most of their heat from the environment.
Homeostatic mechanisms that regulate temperature, body fluids, and metabolism are primarily
negative feedback systems
Hyperphagia
-overeating
-produced by lesions in the ventromedial hypothalamus or the paraventricular nucleus of the hypothalamus
Cognitive factors that contribute to eating behavior
- amygdala- projects to hypothalamus
- Inferior prefrontal cortex- receives input from olfactory bulb
negative feedback
property by which some of the output of a system feeds back to reduce the effect of input signals
Lesions in the lateral hypothalamus (LH)
abolish behavioral regulation, but do not affect physiological responses such as shivering.
Intracellular compartment:
The fluid part of the body contained within cells
Extracellular compartment
The fluid space outside of cells
-The extracellular compartment, is divided between the interstitial fluid (the fluid between cells) and blood plasma (the protein-rich fluid that carries red and white blood cells).
Ventromedial hypothalamus
controls female mating posture
Water moves in and out of cells through
aquaporins
Osmosis
passive movement of water molecules, through a semipermeable membrane, from one place to another
Osmotic pressure
tendency of a solvent to move through a membrane in order to equalize the concentration of solute
Baroreceptors in major blood vessels and the heart detect the initial drop; the heart decreases secretion of
atrial natriuretic peptide (ANP).
atrial natriuretic peptide (ANP) causes
blood pressure to rise and water excretion to decrease
Preoptic area of the medial hypothalamus
Controls copulatory behavior in males, but not sexual motivation
Amygdala (sexual response)
controls sexual motivation in males and possibly in females outside of their estrous cycle
Low road
sensory info -> thalamus -> directly to amygdala
primes the amygdala
High road
thalamus -> sensory cortex -> amygdala
detailed analysis
Primary olfactory pathway
-pyriform cortex
-common odors
-vomeronasal organ: pheromones
______ seem to increase aggression in rats
androgens
______ levels seem to impact aggression levels in humans
serotonin
Hypothalamus stimulates ________ in response to stress
anterior pituitary
Stress immunization
mild stress early in life makes one more capable of handling stress later in life
Epigenetic regulation
change in expression of a gene rather than a change in the encoding region of the gene
