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Flashcards in Problem 7 Deck (50)
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1

System Variable

Characteristic/ Thing to be regulated

ex.: Thirst

2

Set Point

Optimal value of the system variable

ex.: not being thirsty

3

Detector

monitors the value of the system variabel

4

Correctional mechanism

restores the system variable to set point

ex.: water (eating, drinking)

5

Negative feedback

Process whereby the effect produced by an action serves to diminish /terminate the action

ex.: Blood sugar regulation --> insulin lowers blood glucose when levels are high ; glucagon raises blood glucose when levels are low

6

What are Satiety mechanisms ?

brain-based mechanisms that reduce hunger + thirst by making sure there is an adequate intake of nutrients

e.g.: water or food

7

Intracellular fluid

fluid portion of the cytoplasm of the cells
--> 2/3 of the body water is contained here

8

Intravascular fluid

extracellular fluid, found within blood vessels

--> must be closely regulated because it manages the heart

9

Osmometric thirst

Occurs when the solute concentration of interstitial fluid increases

--> interstitial fluid draws water out of the cell which causes the cells to shrink in volume

10

Solute

substances dissolved in solution

ex.: salt

11

Osmoreceptors

- located in lamina terminalis

- responsible for osmometric thirst

12

Lamina terminalis

reflects the activity/concentration of solutes

--> contains the OVLT + SFO which are circumventricular organs

- these organs are located outside the blood brain barrier

13

Anterior cingulate cortex

Activation of this region reflects a persons thirst

14

Volumetric/Hypovolemic Thirst

occurs when the volume of the blood plasma decreases

--> leads to salt appetite

15

Angiotensin

hormone, initiates drinking and salt appetite

--> causes kidneys to retain salt and water when there is reduced blood flow to kidneys

16

Correctional devices for Volumetric thirst

- Baroreceptor reflex
- Vasopressin
- RA System

17

Correctional device for Osmometric thirst

- Cortex
- Vasopressin

18

Baroreceptors

detect when the blood volume in the heart falls

=> correctional device for volumetric thirst

19

Subfornical organ
(SFO)

- low doses of angiotensin in the SFO cause drinking

- destruction of the SFO or injection of a drug that blocks angiotensin abolishes drinking

20

Median preoptic nucleus

Integrating system for most stimuli of osmometric and volumetric thirst

21

Function of the Short term reservoir

Sustains fuel need for several hours between meals

--> stores carbohydrates

- located in liver and muscle cells
- filled with glycogen

22

Short term reservoir
(Procedure)

1. Food is absorbed from digestive tract

2. Presence of insulin causes the conversion of glucose - glycogen

3. Level of glucose falls

4. Fall in level of glucose is detected by cells in pancreas + brain

5. Pancreas stops secretion of insulin + starts secretion of glucagon

6. Presence of glucagon causes the conversion of glycogen - glucose

Process continues for hours until reservoir is used up
--> we usually eat before its empty, if not - long term

23

Function of the Long term reservoir

keeps us alive when we are fasting

--> stores fat, consist of adipose tissue

24

Adipose tissue

located beneath skin

25

Triglyceride

molecules that contain glycerine + fatty acids

--> size of fat cells is determined by the amount triglycerides

26

Long term reservoir
(Procedure)

1. Usage of the contents of the short term reservoir

2. Fat cells start converting triglycerides into fuels which are then released into bloodstream

4. Triglycerides are broken down into their constituents
--> glycerol
--> fatty acids

5. Fatty acids are directly metabolized by all cells of the body except the brain

6. Liver takes up the glycerol and converts it to glucose

7. Glucose is taken into cells and brain

27

Cephalic Phase

Preparatory Phase of metabolism

--> begins with sight, smell or thought of food
--> ends with food entering the digestive system

- insulin is released by pancreas in anticipation of arrival of glucose

28

Absorptive Phase

Digestive phase of metabolism

--> carbohydrates - glucose
--> proteins - amino acids
--> fats = fats

29

Glucose

- level rises when eating

- pancreas stops secreting glucagon + begins secreting insulin so that glucose can be turned into glycogen

30

Ghrelin

Peptide hormone, initiates eating

--> released from gastrointestinal system when digestive system is empty

--> binds to receptors in hypothalamus