Hormonal communication- coordinated responses Flashcards
How does the flight or fight response occur?
-threat detected by autonomic nervous system
-hypothalamus communicates with sympathetic nervous system (neurones) and the adrenal-cordial system (hormones). These combined affects create a fight or flight response.
Role of the sympathetic nervous system in the fight or flight response?
send out impulses to glands and smooth muscles and tells adrenal medulla to release adrenaline and noradrenaline (stress hormones) into blood which cause severe changes in body (e.g increased heart rate)
Describe the role of other stress hormones apart form adrenaline?
-longer term action from the adrenal cortex is controlled by hormones produced by pituitary gland in the brain.
-The hypothalamus stimulates pituitary gland to secrete adrenocorticotropic hormone (ACTH).
-This travels in the blood to the adrenal cortex, where it activates the release of of many hormones which prepare for the threat
Why does heart rate increase?
to pump more oxygenated blood around the body
why do pupils dilate?
to take in as much light as possible for better vision
why do arterioles in the skin constrict?
more blood to major muscle groups, brain, heart and muscles for ventilation
why do blood glucose levels increase?
increased respiration for more energy for muscle contraction
why do smooth muscle of airways relax?
to allow more oxygen into the lungs
why do non essential systems (like digestion) shut down?
to focus on resources on emergency functions
why is there difficulty when focusing on small tasks?
brain solely focused on where threat is coming from
what is one of adrenalines main functions?
to trigger liver cells to undergo glycogenolysis so glucose is released into the blood stream for respiration
How does adrenaline trigger glycogenolysis in the liver cells?
as adrenaline is a hormone and hyphphilic, it cannot pass through the cell membrane so it binds with receptors on the surface, triggering a chain reaction inside the cell
what reaction chain occurs inside a liver cell when adrenaline binds?
-adrenaline binds to receptor causing enzyme adenyl cyclase to be activated (adrenaline-receptor complex)
-Adenyl cyclase triggers the conversion of ATP into cyclic adenosine mono-phosphate (cAMP) on the inner surface of the cell membrane in the cytoplasm
-The increase in cAMP levels activates enzymes called protein kinases which phosphorylate and hence activate other enzymes. Enzymes are activated which trigger the conversion of glycogen into glucose.
what is the first and second messenger?
first- adrenaline
second- cAMP
what part of the brain is responsible for controlling heart rate?
medulla oblongata
Describe the two centres of the the medulla oblongata which is linked to the SAN in the heart
-one centre increases heart rate by sending impulses through the sympathetic nervous system, these impulses are transmitted by the accelerator nerve
-one centre decreases heart rate by sending impulses through the parasympathetic nervous system, these impulses are transmitted by the vagus nerve.
changes in heart rate are dependent on?
blood pressure, pH of blood and stress responses
What are baroreceptors?
receptors which detect changes in blood pressure. E.g if a person’s blood pressure is low, the heart rate increases to prevent fainting. Baroreceptors are located in the aorta, vena cava and the carotid arteries.
What are chemoreceptors?
receptors which detect changes in the level of particular chemicals in the blood such as carbon dioxide. Chemoreceptors are located in the aorta, the carotid artery and the medulla
Why does the pH of blood decrease when carbon dioxide levels in the blood increase?
carbonic acid is formed when carbon dioxide interacts with water in the blood. If chemoreceptors detect a decrease in blood pH, a response is quickly triggered to increase heart rate- therefore blood flows more quickly to the lungs so carbon dioxide can be exhaled
Describe the process of what happens when there is an increased muscular/ metabolic activity?
-more carbon dioxide produced by tissues from increased respiration
-blood pH lowered
-centre in medulla oblongata that speeds heart rate, increases frequency of impulses to SAN via the sympathetic nervous system
-SAN increases heart rate
-increased blood flow removes carbon dioxide faster
-carbon dioxide level returns to normal
What occurs when the carbon dioxide level in blood decreases?
pH of the blood rises which is detected by chemoreceptors in the wall of the carotid arteries and the aorta. This results in a reduction in the frequency of the nerve impulses being sent to the SAN via the sympathetic nervous system and thus heart rate decreases back to its normal level.
What occurs when the carbon dioxide level in blood decreases?
pH of the blood rises which is detected by chemoreceptors in the wall of the carotid arteries and the aorta. This results in a reduction in the frequency of the nerve impulses being sent to the SAN via the sympathetic nervous system and thus heart rate decreases back to its normal level.
What occurs when blood pressure is too high?
-baroreceptors detect this change
-impulses are sent to the medulla oblongata centre which decreases heart rate
-medulla oblongata sends impulses along the parasympathetic neurones to the SAN which decreases heart rate back to normal
What occurs if blood pressure is too low?
-baroreceptors detect this change
-impulses are sent to the medulla oblongata centre which increases heart rate
-the medulla oblongata sends impulses along sympathetic neurones to the SAN which increases heart rate and returns blood pressure back to normal
How do hormones affect heart rate?
In times of stress, adrenaline and noradrenaline are released. These hormones affect the pacemaker region o the heart itself- they speed up heart rate by increasing frequency of impulses produced by SAN.
