Homeostasis (Kapitel 13)

Question 1

Explain the difference between an endotherm and ectotherm animal.

Answer 1

Endotherm, is when an animals body temperature is regulated chiefly by internal metabolic processes (mammels, birds)

Question 2

Thermoregulation is?

Answer 2

The active process of closely regulating body temperature around a set value.

Question 3

Explain what a ‘set point’ is compared to a ‘set zone’ in maintaining homeostasis.

Answer 3

Set point, refers to the point of reference in a feedback system (like setting a thermostat). On the other hand, a ‘set zone’ is the range of a variable that a feedback system tries to maintain (so kind of the same as a set point, just broader, in a way..)

Question 4

What part of the brain senses and controls body temperature?
(hint; it is close to the pituitary gland).

Answer 4

Hypothalamus.

Question 5

Can you name one hormone, that acts a response to cold? (not as the disease, but if it is cold where you are).

Answer 5

Thyroid hormone (increases metabolism).

Question 6

Besides the thyroid hormone, what other 3 reactions are there to being cold?

Answer 6

Metabolism of brown fat, constriction of cutaneous blood vessels, shivering of muscles. (p. 396)

Question 7

Can you name three responses to heat?

Answer 7

Accelerated respiration, perspiration and dilation of cutaneous vessels.

Question 8

When hypothalamus, receptors in the skin and body core detect temperature, this information is sent to three neural regions. Which?

Answer 8

Spinal cord, brainstem and, yes, hypothalamus.

p. 398

Question 9

Can you name these two:

1. The fluid space of the body that is contained within cells.
2. The fluid space of the body that exists outside the cells.

Answer 9

1. Intracellular compartment.

2. extracellular compartment.

Question 10

What and where are ‘aquaporins’ located?

Answer 10

They are channels spanning the cell membrane that are specialized for conducting water molecules into and out of the cell.

Question 11

Can you explain the concept of ‘diffusion’?

Answer 11

It is the spontaneous spread of molecules of one substance among molecules of another substance until a uniform concentration is achieved.

Question 12

What is ‘osmosis’?

what is osmotic pressure?

Answer 12

The passive movement of water molecules from one place to another.

(The tendency of a solvent to move through a membrane in order to equalize the concentration of solute (like salt).

Question 13

There are 3 kinds of tonic (four if you think gin and tonic counts). What are is meant by ‘Isotonic’, ‘hypertonic’ and ‘hypotonic’?

Answer 13

Isotonic: Referring to a solution with a concentration of salt that is the same as that found in interstitial fluid and blood plasma (about 0,9% salt).

Hypertonic: Referring to a solution with a higher concentration of salt than that found in interstitial fluid and blood plasma (more than 0,9%).

Hypotonic: Less than about 0,9% salt. (You might be able to explain, how that is connected to the ‘hypo’ part of the name’?)

Question 14

There are to kinds of thirst, called ‘hypovolemic thirst’ and ‘osmotic thirst’. What causes them?

Answer 14

Hypovolemic thirst: Stimulated by a reduced volume of extracellular fluid

Osmotic thirst: Stimulated by a high concentration of solute (like salt) in the extracellular compartment.

(p. 401).

Question 15

What do Osmosensory neurons in the brain detect?

Answer 15

They detect any increased osmolality of extracellular fluid. (For repetition purposes, you might try to explain or look at p. 401).

Question 16

Short Intermission.

https://www.youtube.com/watch?v=XgvR3y5JCXg

Answer 16

Alan!

Question 17

Barorectors are and work in what way?

Answer 17

Baroreceptors are pressure receptors in the heart or a major artery that detects a fall in blood pressure. This way, they detect any pressure drop from fluid loss, and so has a connection to hypovolemic thirst.

Question 18

Atrial natriuretic peptide (ANP) is a hormone, secreted by the heart. But what does the hormone ‘do / facilitate’?

Answer 18

Reduces blood pressure, inhibits drinking and promotes the excretion of water and salt at the kidneys.

Question 19

In sort of opposition to the secretion of atrial natriuretic peptide, which decrease its secretion when baroreceptors detect a drop in blood pressure, another hormone is released from the posterior pituitary. What is that hormone?

Answer 19

Vasopressin.

Question 20

What is vasopressin and what function does it serve?

Answer 20

It is a peptide hormone from the posterior pituitary. It promotes water conservation.

Question 21

So, just to sum up.
It the following right or wrong:

Heart -> Atrial natriuretic peptide -> excretion of water

Anterior pituitary -> Vasopressin -> water preservation

?

Answer 21

Almost correct. Only one mistake: It is not the anterior pituitary, that releases vasopressin. It is the posterier pituitary.

Question 22

‘angiotensin II’ is?

Answer 22

A subtance that is produced in the blood by the action of renin and that may play a role in the control of thirst. It appears to act at several additional brain sites, particularly the circumventricular organs.

Question 23

Where are the circumventricular organs located?

Can you name one of the organs?

Answer 23

It lies in the wall of a cerebral ventricle and monitors the composition of the cerebrospinal fluid.
(subfornical organ).

Question 24

What job does a osmosensory neuron have?

Answer 24

It is a specialized neuron, that measures the movement og water into and out of the intracellular compartment.

Question 25

aldosterone is a.. ?

Answer 25

.. Mineralocorticoid hormone, secreted by the adrenal cortex, that promotes conservation of sodium by the kidneys.

(p. 404).

Question 26

Another short sum up.

What other important steroid hormone is secreted from the adrenal cortex?

Answer 26

Cortisol.

Question 27

Tip: Terrific drawing of ‘Fluid Regulation’ on p. 405.

Answer 27

.. yes.

Question 28

Why is meant by the therm ‘basal metabolism’? Is it important for survival?

Answer 28

It is the consumption of energy to fuel processes such as heat production, maintenance of membrane potentials, and all other basic life-sustaining functions of the body. So, quite important.

Question 29

A trophic factor is?

Answer 29

A substance that promotes cell growth and survival.

Question 30

What happens at glycogenesis?

Answer 30

It is the physiological process by which glycogen is produced.

Question 31

Insulin is, and is released by?

Answer 31

A hormone, released by alpha cells in the ‘islets of Langerhans’, that lowers blood glucose.

Question 32

What is described as:” a complex carbohydrate made by the combining of glucose molecules for a short-term store of energy”

Answer 32

Glycogen.

Question 33

Can you describe what ‘glycogenolysis’ is?

Answer 33

It is the conversion of glycogen back into glycose, triggered when blood concentrations of glucose drop too low.

Question 34

‘Lipids’ are?

Answer 34

Large molecules (commenly called fats) consisting of fatty acids and glycerol that are insoluble in water.

Question 35

‘Ketones’ Are?

Answer 35

A metabolic fuel source. Liberated by the breakdown of body fats and proteins.

Question 36

What can you say of the Vagus Nerve? What number is it?

Answer 36

It is cranial nerve X, which provides extensive innervation of the viscera (organs). The vagus both regulates organ activity and transmits signals from the viscera to the brain.

Question 37

What is described as:” A complicated brainstem nucleus that receives visceral and taste information via several cranial nerves” ?

Answer 37

nucleus of the solitary tract (NST).

Question 38

What characterizes ‘diabetes mellitus’ ?

Answer 38

Excessive glucose in the urine, caused by the failure of insulin to induce glucose absorption by the body.

Question 39

The ventromedial hypothalamus (VMH) is involved in?

Answer 39

Eating and sexual behaviors.

Question 40

The brain can consume glucose without the aid of insulin. But the body can’t. But what does the body do, in the absence of insulin?

Answer 40

It uses fatty acids for energy.

Question 41

Excessive eating, is also called?

Answer 41

Hyperphagia.

Question 42

The lateral hypothalamus is region involved in?

Answer 42

.. The control of appetite and other functions.

Question 43

‘Aphasia’ is?

Answer 43

Refusal to eat.

Question 44

So, can you figure out what rats with lesions of the lateral hypothalamus (LH) exhibited?

Answer 44

Aphagia (refusal to eat).

Question 45

“This evidence indicates that the X of the hypothalamus contains a highly specialized appetite controller, that is governed by circulating levels of a variety of hormones”. What is X?

Answer 45

arcuate nucleus (an arc-shaped hypothalamic nucleus, implicated in appetite control).

Question 46

Can you name two peptide hormones, that have to do with energy balance in the body (the regulation of wheight). ?

Answer 46

Leptin (released by fat cells). Obese mice, have defective genes for leptin.

Ghrelin (released by the gut). A powerful appetite stimulant.

Question 47

The peptide hormone PYY3-36. What does it do?

Answer 47

It is secreted by the intestines, that probably acts on hypothalamic appetite control mechanism to suppress appetite.

(it even appears that PYY3-36 may act in opposition to ghrelin, providing a potent appetite-suppressing stimulus to the hypothalamus).

Question 48

What is the difference between ‘orexigenic neurons’ and ‘anorexigenic’ neurons?

Answer 48

Whereas orexigenic neurons in the hypothalamic appetite system promote feeding behavior, anorexigenic neurons of the hypothalamic appetite system inhibits feeding behavior.

Question 49

For a drawing of the arcuate appetite system, and a lot of different hormones, see p. 412 - 413.

Answer 49

Yup.

Question 50

“Peptide hormones from the gut - or in the case of leptin, from body fat cells - are carried to the brain, where they help regulate appetite” Right or Wrong?
(if you can, explain why!)

Answer 50

Right.

Question 51

Visceral and somato-sensory information travels via X and spinal nerves. What is X? And what does visceral mean?

Answer 51

Vagus nerve.

visceral; another word for organ

Question 52

Er Purple Rain en god film?

Answer 52

Nej, egentlig ikke. Men soundtrack’et, er for vildt.

Question 53

“Ghrelin and PYY3-34 are thought to exert ongoing minute to minute control on appetite, and they have opposing effects on NPY/AgRP neurons: ghrelin stimulates eating, and PYY3-34 appears to inhibit appetite.” Right or Wrong?

Answer 53

Almost right. The peptide hormone PYY3-34, doesn’t exists. It is called PYY3-36.

(p. 413).

Question 54

What is meant by epigenetic transmission?

Answer 54

The passage of epigenetic modifications of a gene from one generation to another.

Question 55

Bariatic means..

Answer 55

.. having to do with obesity.

Question 56

Can you describe these three?

1. Anorexia nervosa
2. Bulimia
3. Binge Eating.

Answer 56

1. Anorexia nervosa: A syndrome in which individuals severely deprive themselves of food.
2. Buliamia: Also called bulimia nervosa. A syndrome in which individuals periodically gorge themselves, usually with junk food and then either vomit or take laxatives to avoid weight gain.
3. Binge eating: The paroxymal intake of large quantities of food, often of poor nutritional value and high calories.

Question 57

Ready for the eksam?

Answer 57

Good luck.