living control mechanisms

Question 1

define homeostasis

Answer 1

the maintenance of a constant internal environment

is the property of a system in which variables are regulated so that internal conditions remain stable and relatively constant

Question 2

examples of things that need to be kept at a certain level

Answer 2

temperature
blood pressure
pH, glucose and oxygen concentration
hydrogen ion concentration
potassium levels

Question 3

how is homeostasis achieved

Answer 3

1. have a set point (normal range)
2. sensor detects change
3. control centre processes
4. effectors make a change
5. variable is regulated back to normal

Question 4

does every single thing have the same control centre

Answer 4

no its different for everything

Question 5

what are the 2 main types of communication system

Answer 5

• nervous system
• endocrine system

Question 6

what does the nervous system use to communicate

Answer 6

electrical impulses

Question 7

what does the endocrine system use to communicate

Answer 7

hormones

Question 8

what is a receptor

Answer 8

the part that receives a signal from a cell

Question 9

what are the 3 main categories of communication

Answer 9

• autocrine
• paracrine
• endocrine

Question 10

how does autocrine communication work

Answer 10

Chemical is released from cell into the
extracellular fluid and then acts upon the same cell that secreted it

Question 11

how does paracrine communication work

Answer 11

Chemical messengers involved in the
communication between cells, released into the extracellular fluid - travel short distances, local communication (the cells are close to each other)

the signal diffuses across gaps between cells and doesn’t enter the bloodstream

Question 12

what are 2 key differences between paracrine and endocrine

Answer 12

Hormones travel in blood in
endocrine whereas in paracrine chemical messengers only travel in extracellular fluid.

Endocrine affects more things and travels further than paracrine

Question 13

how does exocrine communication work

Answer 13

Secretion into ducts then into organ

Question 14

example of paracrine

Answer 14

interleukins
they signal in the immune system
mainly between white blood cells

Question 15

how does the endocrine communication work

Answer 15

• endocrine cell releases hormone
• hormone travels in bloodstream
• goes to target cell elsewhere in the body

Question 16

which organs and glands are involved in the endocrine system (7)

Answer 16

• hypothalamus (hypothalamic hormones include dopamine)
• pituitary (anterior pituitary hormones include FSH, LH and thyroid stimulating hormone (TSH), posterior pituitary hormones include oxytocin (released during child birth) and ADH/ vasopressin) (in brain, master endocrine organs),
• thyroid (front of neck), parathyroid (directly behind neck),
• adrenals (above kidneys),
• pancreas,
• ovaries
• testes

Question 17

define hormone

Answer 17

a molecule that acts as a chemical structure

Question 18

how are hormones sub divided into different types

Answer 18

according to structure
thus they all have different functions

Question 19

what are the different types of hormones (3)

Answer 19

• amino acid derivatives
• peptide
• steroid

Question 20

what are the most simple type of hormones

Answer 20

amino acid hormones

Question 21

example of amino acid hormone

Answer 21

adrenaline

Question 22

what are amino acid hormones synthesised from

Answer 22

tyrosines

Question 23

what are peptide hormones made of

Answer 23

several amino acids joined together
vary in size from few amino acids to small proteins
some have carbohydrate side chains (glycoproteins)
hydrophilic

Question 24

do peptide and amino acid hormones produce a quick or slow reaction in body

Answer 24

a quick reaction

Question 25

example of peptide hormone

Answer 25

thyroid-stimulating hormone - stimulates the thyroid gland
released from pituary

Question 26

how do peptide hormones work

Answer 26

• cell makes the hormone
• hormone is stored within the cell ready to be released when required
• hormone is dissolved in blood stream
• goes round blood stream to receptor cell on cell membrane
• hormone binds to receptor
• chemical reaction produces quick response from cell

Question 27

what are steroid hormones derived from

Answer 27

cholesterol

different enzymes modify molecules to produce a variety of hormones

Question 28

properties of steroid hormones

Answer 28

cant dissolve in water
cant dissolve in lipids

Question 29

do steroid hormones produce slow or fast response

Answer 29

slow response

Question 30

how do steroid hormones work

Answer 30

• made continuously by cell
• diffuse through lipid bilayer into blood stream as they are made (Not stored)
• bind to specific carrier protein
• which carries them throughout blood stream
• hormone dissolves through cell membrane at other end
• receptor is inside target cell
• hormone produces change on DNA
• by affecting DNA replication or transcription
• this is why its slow

Question 31

what is a positive feeback loop

Answer 31

• signal is amplified
• so cell is stimulated to produce more

Question 32

examples of positive feedback (2)

Answer 32

clotting cascade
oxytocin release during childbirth

Question 33

what does negative feedback loop do

Answer 33

main way endocrine hormones are controlled.

Question 34

which systems use negative feedback

Answer 34

blood sugar regulation, temperature regulation, blood pressure regulation, thyroid regulation

Question 35

how is thyroid regulated using negative feedback

Answer 35

thyroid regulation - thyroxin, as well as going to target cell, is also sensed by the pituitary, if there is too much thyroxine in the blood then the high thyroxine levels will stimulate the pituitary to stop producing thyroid stimulating hormone (TSH)

Question 36

what are problems with feedback

Answer 36

Can get primary hypothyroidism: that is the thyroid is
producing too little thyroxine to induce negative feedback, meaning TSH levels in the blood keep increasing since pituitary doesn’t think there is enough thyroxine in the blood. Can also get primary hyperthyroidism: whereby the thyroid produces too much thyroxine and keeps producing regardless of the presence of TSH produced by the pituitary, TSH levels fall but thyroxine levels rise. Primary - means the problems is with the endocrine gland e.g. the thyroid. Secondary - means the problem is with the pituitary or hypothalamus e.g secondary hypothyroidism - whereby both TSH and thyroxine levels are low (indicative of secondary hypothyroidism) since the pituitary is not producing enough TSH thus little thyroxine is produced meaning target cells are not being induced.