Homeostasis

Question 1

what is homeostasis

Answer 1

the maintenance of relatively constant conditions in the internal environment (ECF) in the face of external or internal change

Question 2

what is a regulated variable

Answer 2

the variable the system senses and tries to keep stable

Question 3

what is a set point

Answer 3

the target variable for that regulated variable

Question 4

what is a reference range

Answer 4

values of the regulated variable within normal limits

Question 5

what is inter-individual variation

Answer 5

variation in set points between individuals

Question 6

what is intra-individual variation

Answer 6

within an individual variables fluctuate around the set point in response to normal activity

Question 7

what is a circadian rhythm

Answer 7

cycle of 24 hours

Question 8

what is a monthly rhythm

Answer 8

normal fluctuation in levels several hormones and body temperatures

Question 9

what type of distribution do reference ranges follows and what individuals are considered normal

Answer 9

• usually follows a normal distribution and the values within 2 standard deviations of the mean is considered normal
• 95% of measurements from healthy people will be within 2 standard deviations of the mean of that variable

Question 10

what is a negative feedback system

Answer 10

a regulatory mechanism where the output of a process or system reduces the input, leading to a more stable state. It works by having the product of a reaction or the output of a process trigger a mechanism that decreases the original process.
- opposes change and move regulated variable back towards its set point

Question 11

what are the 4 components of the negative feedback system

Answer 11

1. sensors
2. control center or integrator
3. communication pathways
4. effectors

Question 12

what is the role of the sensor in the negative feedback system

Answer 12

monitor the regulated variable and detects deviation from set point

Question 13

what is the role of the control center or integrator in the negative feedback system

Answer 13

compares the variables actual value to the set point

Question 14

what is the role of the communication pathways in the negative feedback system

Answer 14

sends via communication pathways to effectors if correction is required

Question 15

what is the role of the effectors in the negative feedback system

Answer 15

act to oppose the effect of the stimulus, thereby correcting the change and restoring the variable to its set point

Question 16

what is a positive feedback system

Answer 16

amplifies an initial stimulus, causing a change in the same direction
- is a response to a stimulus that moves the variable further away from the set point, therefore it reinforces the initial change

Question 17

what is a feedforward system

Answer 17

involves detection or anticipation of conditions that could disrupt homeostasis if some sort of preemptive action was not taken

Question 18

how does a feedforward system work

Answer 18

based on information received, the integration center established a future predicted value for the the regulated variable, compares this with the set point and makes anticipatory corrections

Question 19

what are the 2 types of feedforward responses

Answer 19

1. physiological feed forward
2. behavioral feed forward

Question 20

where the nervous system’s neurons produce APs and release neurotransmitter at synapse, what does the endocrine system do to communicate?

Answer 20

most hormones are circulating hormones secreted initially into the interstitial fluid then diffuses into blood to be transported to target tissues

Question 21

what do hormones bind to in the endocrine system

Answer 21

hormones bind to membrane or intracellular receptors of target cells - affects any cells with correct receptors

Question 22

compare the speed of the nervous system to the endocrine system

Answer 22

endocrine is relatively slower, but generally longer lasting and more widespread action compared to nervous - which is typically fast

Question 23

what are local hormones

Answer 23

Local hormones are a large group of signaling molecules that do not circulate within the blood. Local hormones are produced by nerve and gland cells and bind to either neighboring cells or the same type of cell that produced them

Question 24

what is paracrine

Answer 24

local hormones that act locally on other nearby cells

Question 25

what is autocrine

Answer 25

local hormones act on the same cell that secreted them

Question 26

what are the 3 classes of hormones

Answer 26

1. amino acid derivatives 2. peptide hormones and protein hormones 3. lipid derivatives

Question 27

what are amino acid derivatives

Answer 27

hormones that are synthesised by modifying particular amino acids typically by changing the amino group, carboxyl group, side chain, or any group attached to the central carbon

Question 28

what are peptide hormones

Answer 28

hormones of chains of 3 to 49 amino acids

Question 29

what are protein hormones

Answer 29

hormones of chains of 50 to 200 amino acids

Question 30

what are glycoprotein hormones

Answer 30

protein hormones that have carbohydrate groups attached

Question 31

what are peptide and protein hormones synthesised as 1st (not biologically active)

Answer 31

as larger preprohormones that are not biologically active but may contain a sequence of various peptides that are

Question 32

what are peptide and protein hormones cleaved into from preprohormones and where

Answer 32

prohormones in ER

Question 33

what are peptide and protein hormones cleaved into from prohormones and how

Answer 33

- prohormones are packaged into secretory vesicles in golgi apparatus - during this process enzymes in vesicles cleave prohormones to produced active hormone and inactive fragments

Question 34

what are lipid derivatives (steroid hormones)

Answer 34

hormones derived from lipids - cholesterol

Question 35

what are the differences among steroid hormones

Answer 35

the chemical groups attached at various sites on the 4 ring structure are responsible for producing diverse effects

Question 36

why do steroid hormones remain in circulation longer that peptide hormones

Answer 36

steroid hormones are bound to specific transport proteins in blood so they remain in circulation longer

Question 37

what does the response to a hormone depend on

Answer 37

1. the hormone itself 2. the particular target cells - what receptors are present - their intracellular machinery

Question 38

how do the same hormones produce different effects in different cells

Answer 38

due to the presence of different hormone receptors and signaling pathways within those cells.

Question 39

to have an effect, what should a hormone first bind to

Answer 39

a hormone must first bind to receptors on the target cells which are in the cell membrane or in the cytoplasm/nucleus

Question 40

why are amine, peptide and protein hormones receptors membrane proteins at the cell surface

Answer 40

they are generally not lipid soluble

Question 41

what is the first messenger in the action of water soluble hormones

Answer 41

when the hormone binds to these receptors - hormone acts as first messenger

Question 42

what is the second messenger in the action of water soluble hormones and how is it activated

Answer 42

- the activated receptor via its coupling to a G protein then causes the production of a second messenger inside the cell - adenylate cyclase (AC)

Question 43

what are Cyclic adenosine monophosphate and calcium ions

Answer 43

second messengers

Question 44

what are G proteins

Answer 44

a class of proteins that act as intermediaries in signal transduction, converting external signals from cell surface receptors into intracellular actions

Question 45

what are G protein coupled receptors

Answer 45

integral membrane proteins containing an extracellular amino terminus, seven transmembrane α-helical domains, and an intracellular carboxy terminus

Question 46

what activates the G protein

Answer 46

the binding of hormone to receptor (externally) activates the G protein (internally)

Question 47

what can a G protein do once it has been activated by the hormone

Answer 47

- G protein subunit can then activate enzymes on inner cell membrane (adenylate cyclase) to produce a second messenger (cAMP) - alter activity of ion channels so that Ca act as second messenger

Question 48

what can a second messenger do once it has been activated by the G protein

Answer 48

they can switch on or off various enzymes within the cell

Question 49

how can some G proteins decrease enzyme activity

Answer 49

they can inhibit adenylate cyclase and so reduce cAMP - reduces enzyme activity