Hormonal communication in animals

Question 1

endocrine glands

Answer 1

release hormones directly into blood

Question 2

exocrine glands

Answer 2

• don’t secrete hormones
• have small duct that carries secretion to where it’s needed eg. salivary glands

Question 3

how does a hormone affect a target cell?

Answer 3

• cells receiving hormonal signal (target cells) must have complementary receptor on plasma membrane which hormone binds to
• each hormone is different and has different receptor

Question 4

protein and peptide hormones

Answer 4

• hydrophillic so cannot ass through plasma membrane
• secondary messenger needed
• eg. adrenaline, insulin, glucagon

Question 5

steroid hormones

Answer 5

• derived from cholesterol
• lipid soluble so can pass through plasma membrane and attach to receptors in cytoplasm or nucleus
• transcription factors - act to facilitate or inhibit transcription of specific gene

Question 6

adrenal glands structure

Answer 6

• each gland divided into cortex and medulla
• located on top of each kidney

Question 7

adrenal glands function

Answer 7

• release adrenaline in response to stress eg. pain or shock
• effect prepares body for action
• increased heart rate, increased stroke volume, vasocontriction (raises blood pressure), relax smooth muscle in bronchioles, dilate pupils, increase mental awareness, inhibit gut action, hairs erect, converts glycagen to glucose

Question 8

adrenal cortex function

Answer 8

• uses cholesterol to produce steroid hormones
• mineralocordicoids:
  eg. aldosterone - controls blood pressure by balancing sodium, potassium and water in blood
• glucocorticoids - help regulate metabolism by controlling how body converts fats, proteins, carbs to energy
• androgen - small amounts of male and female sex hormones
  eg. cortisol

Question 9

coordinated responses

Answer 9

• an instinct possessed by all animals
• threat is perceived by autonomic NS, hypothalamus communicates with sympathetic NS and adrenal cortical system
• effects result in ‘fight or flight’

Question 10

coordination of fight or flight in adrenal cortical system

Answer 10

• hypothalamus activates adrenal-cortical system by releasing CRF
• pituitary gland secretes ACTH which arrives at adrenal cortex and releases about 30 hormones to bloodstream
• fight or flight

Question 11

coordination of fight or flight in sympathetic NS

Answer 11

• hypothalamus activates sympathetic NS
• this activates glands and smooth muscle
• it also activates adrenal medulla which releases noradrenaline and adrenaline to the bloodstream
• fight or flight

Question 12

how is cell signalling used by hormones - adrenaline and liver cells?

Answer 12

• adrenaline (first messenger) binds to specific receptor on liver cell plasma membrane
• this causes receptor to alter and interact with G-protein which splits and one part interacts with adenylyl cyclase
• this causes the enzyme adenylyl cyclase to be activated and turn ATP into cAMP
• cAMP- secondary messenger, binds and activates a protein kinase enzyme which activates glycogen phosphorylase kinase which binds to glycogen phosphorylase
• this is an enzyme which breaks glycogen down into glucose

Question 13

pancreas exocrine function

Answer 13

• secretes alkaline pancreatic juices which pass into duodenum via pancreatic duct
• alkaline because of sodium carbonate - helps neutralise contents which have left acidic stomach
• pancreatic juice contains enzymes such as:
  lipase - hydrolysis of lipids to fatty acids and glycerol
  amylase - hydrolysis of starch to maltose
  trypsin - hydrolysis of proteins to amino acids

Question 14

acinar cells

Answer 14

• groups of them surround tiny tubules that produce digestive juices
• make up most of the pancreas

Question 15

pancreas endocrine function

Answer 15

• islets of Langerhans - endocrine cells- make up 5% of volume of pancreas
• they secrete peptide hormones which control glucose levels
• endocrine cells are close to lots of capillaries which they can secrete hormones into

Question 16

alpha cells in pancreas - how they secrete the hormone

Answer 16

• manufacture and secrete glucagon to increase blood glucose levels
• alpha cells detect glucose level falling
• glucagon binds to receptors in liver cell plamsa membrane activating enzyme which breaks down glycogen into glucose - glycogensolysis
• this glucose is transported out liver cells by facilitated diffusion
• gluconeogenesis - new glucose made from amino acids and glycerol
• this causes blood glucose levels to rise

Question 17

beta cells in pancreas - how they secrete the hormone

Answer 17

• manufacture and secrete insulin to decrease blood glucose levels
• usually K+ channels are open so K+ diffuses outside the membrane, maintaining -70mV on inside of cell
• Ca2+ usually closed
• when glucose moves inside the cell by a transporter, it’s phosphorylated by glucokinase then metabolised into ATP
• ATP sensitive K+ channels close when ATP binds to them, reducing electrochemical grad to -30mV inside the cell
• this causes voltage gated Ca2+ channles open and Ca2+ floods into the cell - depolarisation
• Ca2+ help form and move the vesicles containing insulin so insulin can be released by exocytosis

Question 18

normal blood glucose level

Answer 18

3.5-7 mmol/dm3

Question 19

hyperglycaemic blood glucose level, why it’s a problem and symptoms

Answer 19

• 15 mmol/dm3
• cells have higher water potential than the blood and lose water to the blood
• symptoms - extreme thirst, blurred vision, ketoacidosis
• ketoacidosis - ketone bodies are formed by fatty acids in the liver causing an acidosis that can be fatal

Question 20

hypoglycaemic blood glucose level and why it’s a problem

Answer 20

can lead to inadequete glucose for respiration in cells

Question 21

glycogen

Answer 21

• store of glucose in liver and muscle cells
• large insoluble polysaccharide linked by alpha 1-4 glycosidic bonds and alpha 1-6 side branches

Question 22

insulin secretion

Answer 22

• in most cells, insulin can only enter cells via a transporter protein in membrane
• Eg. in muscle cells it is GLUT4 - usually in cytoplasm, but when insulin levels increase they move to the membrane to allow glucose to enter the cell and reduce the blood glucose level
• the cell can then utilise the glucose for respiration

Question 23

glycogenesis

Answer 23

• driven by raised insulin level
• insulin binds to receptors on plasma membrane of liver cells, activating enzyme called glucokinase
• glucokinase phosphorylates glucose, trapping it inside the cell as it can’t pass through the membrane tranporters
• phosphofructokinase and glycogen synthase catalyse formation of glycosidic bonds between glucose ot make glycogen
• as glucose levels drop, beta cells reduce amount of insulin reduced

Question 24

type 1 diabetes

Answer 24

• usually occurs in childhood
• destruction of beta cells, usually as an autoimmune response
• insulin not produced at all

Question 25

type 2 diabetes

Answer 25

• onset later in life
• insulin resistance - it’s released but lover doesn’t respond correctly
• link to high BMI and high visceral fat

Question 26

symptoms of diabetes

Answer 26

• urine with glucose level over 9 mmol/dm3
• tired (cells can’t respire as glucose can’t get in), thirsty (low water pot. compared to glucose level in blood), urinary frequency (drinking more water bc low water pot.)

Question 27

how do you monitor diabetes?

Answer 27

• clinistix or diastix - urine dip sticks
• blood testing - spot test with biosensor

Question 28

treatment of type 1 diabetes

Answer 28

• insulin from pig or genetically engineered injected at regular intervals (not in tablet form because insulin is peptide hormone so would be digested)
• infusion pumps
• planning diet
• regular exercise

Question 29

treatment of type 2 diabetes

Answer 29

• diet control
• exercise
• drugs that affect glucose absorption - reduce glycogenesis and enhance insulin production eg. metformin prevents glucose being absorbed