Hormonal communication Flashcards
1
Q
endocrine glands
A
secrete hormones directly into blood
2
Q
exocrine glands
A
- don’t secrete hormones
- have small duct that secrete chemicals to where they’re needed eg. salivary glands
3
Q
how does a hormone cause a response on a target cell?
A
- 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
4
Q
protein and peptide (non-steroid) hormones
A
- hydrophillic so cannot pass through plasma membrane
- attach to receptor on plasma membrane which triggers secondary messenger
- eg. adrenaline, insulin, glucagon
5
Q
steroid hormones
A
- derived from cholesterol
- lipid soluble so can pass through plasma membrane and attach to receptors in cytoplasm or nucleus
- they are transcription factors - act to facilitate or inhibit transcription of specific gene
- eg. testosterone, oestrogen
6
Q
differences between endocrine system and nervous system
A
- endocrine - communication by hormones, nervous - communication by nerve impulses
- transmission in blood vs by neurones
- slow vs rapid
- widespread vs localised
- long-lasting vs short-lived
- effect can be permanent vs temporary
7
Q
adrenal glands structure and location
A
- each gland divided into cortex on outside and medulla on inside
- located on top of each kidney
8
Q
adrenal glands and adrenaline function
A
- release adrenaline in response to stress eg. pain or shock
- outer layer - capsule, next layer in - cortex, inner section - medulla
- 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 glycogen to glucose
9
Q
adrenal cortex function
A
- uses cholesterol to produce steroid hormones
- mineralcorticoids eg. aldosterone - controls salts (potassium and sodium) and water balance in blood - impact on blood pressure
- glucocorticoids eg. cortisol - main stress hormone - helps regulate metabolism by controlling how body converts fats, proteins, carbs to energy
- androgens - sex hormones eg. testosterone after puberty
10
Q
adrenal medulla function
A
- releases hormones when sympathetic NS activated
- adrenaline - increases heart rate to send blood to muscles and brain, increases blood glucose levels by converting glycogen to glucose
- noradrenaline - increases heart rate, widens pupils, widens air passages in lungs, narrows blood vessels in non-essential organs - high BP
11
Q
fight or flight responses overall
A
- 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’
Responses: - increased HR - pump more oxygenated blood around body
- pupils dilated - more light taken in for better vision
- blood glucose levels increase - more respiration
- smooth muscle of airways relax - more oxygen in lungs
- digestion stops - focus more resources on emergency functions
12
Q
fight or flight in adrenal cortical system
A
- hypothalamus stimulates pituitary gland to secrete ACTH
- ACTH arrives at adrenal cortex and releases about 30 cortisol hormones to bloodstream
- fight or flight
13
Q
fight or flight in sympathetic NS
A
- hypothalamus activates sympathetic NS
- this activates glands and smooth muscle
- also activates adrenal medulla which releases noradrenaline and adrenaline to bloodstream
- fight or flight
14
Q
adrenaline effect on liver cells
A
- process has a cascade effect
- adrenaline (first messenger) binds to specific receptor on liver cell plasma membrane
- this activates the enzyme adenylyl cyclase to turn ATP into cAMP
- cAMP- secondary messenger, binds and activates a protein kinase enzyme which activates other enzymes
- the final enzyme triggers conversion of glycogen into glucose
15
Q
ways of increasing blood glucose concentrations
A
glycogenolysis - glycogen in liver and muscle cells is broken down into glucose - released into bloodstream, increasing blood glucose conc
gluconeogenesis - production of glucose from non-carbohydrate sources eg. liver makes it from glycerol and amino acids, it’s then released into the bloodstream to increase blood glucose conc
16
Q
ways of decreasing blood glucose concentration
A
Respiration - glucose in blood used by cells to release energy
Glycogenesis - production of glycogen from excess glucose is stored in liver
17
Q
pancreas exocrine function
A
- 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
18
Q
acinar cells
A
- groups of them surround tiny tubules that produce digestive juices
- make up most of the pancreas
19
Q
pancreas endocrine function
A
- islets of Langerhans - endocrine cells - made up of beta or alpha cells
- they secrete peptide hormones which control glucose levels
- endocrine cells are close to lots of capillaries which they can secrete hormones into
20
Q
alpha cells in pancreas - how do they increase blood glucose conc?
A
- alpha cells detect glucose level falling and secrete glucagon into bloodstream
- glucagon binds to receptors in liver cell plamsa membrane activating enzyme which breaks down glycogen into glucose - glycogenolysis, this glucose is transported out liver cells by facilitated diffusion
- glycogen also reduces amount of glucose absorbed by liver cells
- increases gluconeogenesis - new glucose made from amino acids and glycerol
- when alpha cells detect blood glucose cons above a certain level, secretion stops (negative feedback
21
Q
beta cells in pancreas - how they decrease blood glucose conc
A
- manufacture and secrete insulin
1. usually K+ channels are open so K+ diffuses outside the membrane, maintaining -70mV on inside of cell
2. when glucose moves inside the cell by a transporter, it’s metabolised in mitochondria into ATP
3. ATP sensitive K+ channels close when ATP binds to them, reducing electrochemical grad to -30mV inside the cell - depolarisation
4. this causes voltage gated Ca2+ channles open and Ca2+ floods into the cell - depolarisation
5. Ca2+ help form and move the vesicles containing insulin so insulin can be released by exocytosis
22
Q
normal blood glucose level
A
3.5-7 mmol/dm3
23
Q
hyperglycaemic blood glucose level, why it’s a problem and symptoms
A
- 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
24
Q
hypoglycaemic blood glucose level and why it’s a problem
A
- below 3mmol/dm3
- can lead to inadequete glucose for respiration in cells
- symptoms: dizziness, feeling weak, nausea
25
glycogen
- store of glucose in liver and muscle cells
- large insoluble polysaccharide linked by alpha 1-4 glycosidic bonds and alpha 1-6 side branches
26
insulin effect on muscle cell
- insulin binds to receptor on plasma membrane
- receptor signals to cell to make vesicles with transporter protein (GLUT4) merge with the plasma membrane
- allows glucose to enter the cell and reduce the blood glucose level
- the cell can then utilise the glucose for respiration
27
how does insulin cause glycogenesis?
- 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
- 2 other enzymes catalyse formation of glycosidic bonds between glucose to make glycogen
- as glucose levels drop, beta cells reduce amount of insulin reduced
28
type 1 diabetes
- usually occurs in childhood
- destruction of beta cells, usually as an autoimmune response - immune system attacks beta cells
- insulin not produced at all
29
type 2 diabetes
- onset later in life
- insulin resistance - it's released but receptor on cell doesn't work correctly - cells don't take up enough glucose
- beta cells don't release enough insulin
- link to high BMI and high visceral fat
30
symptoms of diabetes
- 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.)
31
how do you monitor diabetes?
- clinistix or diastix - urine dip sticks
- blood testing - spot test with biosensor
32
treatment of type 1 diabetes
- blood glucose level is tested by pricking finger and a machine analysing it
- amount of insulin injected is dependent on blood glucose level
- insulin will reduce blood glucose levels
33
treatment of type 2 diabetes
- diet control
- exercise
- insulin injections
- drugs that affect glucose absorption - reduce glycogenesis and enhance insulin production eg. metformin prevents glucose being absorbed
34
where can insulin injections come from?
- pancreas of pigs or cows
- genetically modified bacteria - pure form (less allergic reaction), higher quantities, cheaper, more ethical
35
stem cells in diabetes treatment and advantages
- totipotent - can grow into any type of cell
- usually come from embryo - 'spare' from infertility treatments/terminated pregnancies
- advantages: doesn't require a donor, reduced likelihood of rejection, doesn't require insulin injection
36
how does the body know there needs to be a heart rate change?
- baroreceptors in the aorta, vena cava or carotid arteries detect a blood pressure change
- baroreceptors send nerve impulse along sensory neurones to medulla oblongata which sends an impulse along a parasympathetic/sympathetic neurone to decrease/increase heart rate
- chemoreceptors in carotid artery, aorta and medulla detect a chemical change eg. pH of blood reducing as CO2 levels rise causes heart rate to increase to send more blood to lungs so CO2 is exhaled
37
what happens when high bp is detected?
- cardioinhibitory centre sends nerve impulse along parasympathetic neurones to the SAN
- acetylcholine is secreted at the parasympathetic neurone and binds to receptors in the SAN
- this reduces the rate of impulses sent from the SAN to heart muscle to reduce heart rate
38
what happens when low bp is detected?
- cardioacceleratory centre in medulla oblongata sends nerve impulse along sympathetic neurones to SAN
- noradrenaline is secreted by sympathetic neurone and binds to receptors on SAN
- this increases the rate of impulses sent from the SAN to the heart muscle so heart rate increases
