Week 9 - Motivation: Homeostatic survival Flashcards
Learn about the motivation systems for survival
Explain the two motivational processes for thirst?
There are two ways we can become thirsty, Extracellular (outside cells - usually in the bloodstream) and Intracellular (inside the cells) water levels
Extracellular water volume has blood pressure receptors that alert the hypothalamus (axons) about blood pressure.
When you are high water levels (hydrated), this causes high blood pressure (water expands the blood), which is detected by the receptors
Conversely, If you have low water levels, blood vessels shrinks, which is detected by the hypothalamus, motivating drinking behaviour. This low blood pressure (shrinkage of blood vessels) is detected and causes the release vasopressin (hormone) from the pituitary gland to further shrink the blood vessels.
Intracellular water volume is registered by the osmoreceptors, by detecting cell shrinkage cause by water loss, which initiates drinking.
Outline what the function of vasopressin and what is its purpose? How does this hormone impact the kidney?
When blood vessel shrinkage is detected, vasopressin is released by the pituitary gland, which constricts blood vessels to increase blood pressure.
This occurs to keep the blood moving to avoid passing out from lack of oxygen to get to water.
The vasopressin also causes the kidney to retain water to reduce water loss from processes such as urination
Outline the basic process of high and low level water motivation for thirst?
High water expands blood, creates high pressure expanding blood vessels, detected by receptors in vessels, alerting the thalamus, motivating behaviour
Low water, low blood pressure, detected by blood vessel receptors, alerting the thalamus, motivating behaviour, which also release vasopressin from the pituitary gland to keep oxygen/energy moving via blood, also causing kidneys to retain water (making you thirsty and reducing urination).
Outline what happens when the body gets too hot/cold, giving an example?
If the body gets too hot/cold vital functions cease to operate properly.
When getting too hot, as in runner in hot weather, proteins in the calves can denature, breaking down the muscles.
When in too cold, your blood can become too viscous, making it too hard to pump.
Explain the process of Thermo-regulation?
(stable temps - too hot or too cold)
Thermo-regulation in a bodily mechanism that maintains a relatively stable body temperature.
It can be internally regulated with the hypothalamus which detects the temperature of blood, activating the parasympathetic nervous system to decrease heat by vasodiolation and sweating. For example when your blood vessels dilate in you face after a run and you are red and sweaty (evaporative cooling). or
the sympathetic nervous system to preserve heat that causes vasoconstriction, shivering and goosebumps (vestigial characteristic).
Externally, behavioural adjustments can be made when too hot or too cold by moving to a hotter place (like ectotherms - lizards on a hot rock in the sun) or making warmers (as in endotherms who have an efficient circulatory system with separate pathways for oxygenated and deoxygenated blood, so we can wast oxygen to create heat).
Explain how to hypothalamus is directly and indirectly involved in Motivation?
Directly – neuronal connection, sending axons down to the autonomic nervous system
Indirectly: through the release of hormones into the blood, stream with the pituitary gland
(1) Hormones are synthesised in the hypothalamus and sent to axon terminals in the posterior/anterior pituitary gland. (2) These hormones are released by axon terminals in the posterior/anterior pituitary gland and are picked up by bloodstream.
(3) Hypothalamus not just releases things into the blood stream, it also detects what in the blood stream (sensitive to hormones in the blood stream, temperature of blood, glucose in blood) which helps regulate behaviour.
Explain how to hypothalamus influences eating behaviour? Identify what occurs with ventro-medial, and lateral lesion and stimulation?
For two areas of the thalamus, the lateral and ventro-medial sections, when lesion or stimulation of these areas occurs it produces stimulated eating behaviour (hyperphagia - VM lesion) and decreased eating behaviour (aphagia - lateral lesion).
Explain the effect of lesion to the ventro-medial thalamus on eating behaviour?
Lesion of the ventro-medial thalamus induces abnormally high activity in the parasympathetic nervous system (by destroying the whole regulatory system/set point for eating). This causes increased secretion of insulin, which causes an excess of glucose to be used up (converted to fat), reducing the amount of available glucose (for energy use), which stimulates eating behaviour.
Explain what three receptors are activated when a drop in blood pressure/volume occurs?
(1) Baroreceptors (signals) in major blood vessels send signals to brain via the autonomic NS.
(2) Vasopressin (reduce Bl/Ur)( posterior pituitary) reduces blood vessel volume and urination
(3) Angiotensin II (reduce Bl, signals thirst) from the renin release in Kidneys, narrows blood vessels to maintain blood pressure and send signals to the brain to stimulating thirst.
Outline the process of Hunger, and how it is initiated?
The body ‘needs’ food for energy, nutrients and protiens, where there are many cues to stimulate and terminate hunger. Hunger is usually directly initiated with glucose levels either (1) immediately when low glucose levels are detected by the thalamus and stimualte eating behaviour, or (2) over long period with signals from the liver that regulate eating behaviour when the liver detects the conversion of glucose to glycogen (dont eat), or glycogen to glucose (eat, using the reserves).
Identify four ways that hunger can be reduced, other than glucose levels?
(1) In humans/primate when stomach is full
(2) in other animals with calories counts
(3) Food that is high in calories/ or tastes that it is high in calories
(4) eating simple carbs, as they quickly increase glucose levels and reduce hunger rapidly.
Outline the three main function of Insulin in regulating glucose levels?
Permits, converts, and detects.
(1) permits the body cells to use glucose, (2) promotes the conversion of glucose into glycogen (stores), (3) provides a signal to the brain to detect glucose levels.
