Lecture 3 Internal Constancy

What are the two physiological methods that all animals use to deal with change?

• Regulation

• Conformity

What is an example of a regulatory homeostasis in humans?

Glucose metabolism

How do anadromous salomonids deal with swimming into both freshwater and saltwater

They regulate their blood ion concentration so that they are constant

How do anadromous salmonids regulate their blood ion (Na+, K+, CL-..) concentration?

Chloride cells in the gills via activity of Na+,K+-APTase enzymes (Sodium potassium ATPase enzymes)

In sea water, what do anadromous salmonids do?

They need to counteract the uptake of ions so gill Na+,K+-ATPase enzymes shed excess ions from the body

In fresh water, what do anadromous salmonids do?

They need to retain ions in their blood so gill NA+,K+-ATPase enzyme activity is reduced

How do temperature regulators relate to conformers?

Both can thermoregulate behaviorally (taking actions to change their temperature like swimming to warmer areas)

What is behavioral thermoregulation?

Changing your behavior to indirectly regulate your internal body temperature

How does the glucose metabolism work?

A spike in glucose leads to increase in insulin which converts the glucose into glycogen for storage. When glucose levels are too low, glucagon is released which breaks down glycogen and releases glucose

Give an example about how problems with homeostasis can be fatal?

Normally brown bats hibernate in the winter by reducing their metabolism and sleeping until the end of winter. Fungi linked to climate change disrupts this and the bat uses more energy than normal. They run out before the end of winter, wake up, and die.

What does negative feedback do

It shuts down upstream metabolic signals

What is the Hypothalamus-Pituitary-Thyroid Axis?

Negative feedback that produces T3 and T4 which are involved in temperature regulation and growth

How does the Hypothalamus-Pituitary-Thyroid Axis work?

When the body needs the hormones, the hypothalamus releases thyrotropin releasing hormone which is recieved by the pituitary. The pituitary releases thyroid stimulating hormone which is picked up by the thyroid gland. It then releases T3 and T4

How does the hypothalamus-pituitary-thyroid axis end?

When there is enough T3 and T4 in the blood, it tells the hypothalamus and pituitary gland to stop releasing hormones

How does negative feedback work for temperatures in jack rabbits when they are too hot?

1. HPT axis decreases thyroid hormone release

2. Vasodilation increases blood flow through skin and ears

3. Heat is dumped into the environment

How does negative feedback work for temperatures in jack rabbits when they are too cold?

1. HPT axis increase thyroid hormone release

2. Vasoconstriction reduces blood volume through skin and ears

3. Heat is retained in core

What happens if the human body lacks iodine?

Thyroid hormones cannot be made so a buildup of thyroid stimulating hormones causes a lump called thyroid hyperplasia

Give an example of positive feedback in humans and how it works:

labor: When there is contraction, Mechanoreceptors at the head of the cervix send feedback to the hypothalamus and then the pituitary. The pituitary releases oxytocin which creates more prostaglandins which stimulates more contractions