Hormonal communication Flashcards
Which part of the brain coordinates the fight or flight response?
Hypothalamus
What are the two pathways involved in the FoF response?
- Sympathetic nervous system and adrenal-cortical system
How does the sympathetic nervous system pathway work in the FoF response?
- Sensory neurones detect change, sends impulse to amygdala.
- This stimulates the hypothalamus, which in turn stimulates the sympathetic nervous system to send impulses to the adrenal glands.
- Activates the adrenal medulla, stimulates release of adrenaline and noradrenaline into the bloodstream.
- Impulses activate glands and smooth muscles e.g in eyes/skin.
How does the adrenal-cortical system pathway contribute to the FoF response?
- Activated by hypothalamus.
- Releases CRF which stimulates the pit. gland to produce ACTH.
- ACTH arrives at the adrenal cortex and releases approxiamtely 30 hormones into the bloodstream, including cortisol.
How is heart rate controlled?
- Chemo/baro receptor detects change (found in carotid artery and aorta)
- Signal sent to medulla.
- Impulse sent down accelerator or vagus nerve (para) to SAN, increasing or decreasing the frequency of contraction.
How does adrenaline act on cells?
- Binds to external receptor on CSM.
- This activates adenylyl cyclase on the inside, causing a change in shape.
- A.C can then convert ATP into cAMP which can go on to act as a secondary messenger, activating other enzymes which convert glycogen to glucose.
- Protein kinase A –> phosphorylase kinase –> glycogen phosphorylase.
Where are chemo and baro receptors found?
In the carotid artery and aorta
What is the effect of ACh released at the synapse with the SAN?
- Reduces the frequency of impulses triggered by the SAN.
Which hormones does the adrenal cortex produce?
- Glucocorticoids: cortisol (regulates metabolism), corticosterone (suppresses inflammatory reactions).
- Mineralocorticoids: aldosterone (control b.p by maintainng salt and water conc.), androgens (sex hormones)
Which hormones does the adrenal medulla produce?
- Adrenaline and noradrenaline.
How does the pancreas act as an exocrine gland?
- Pancreatic acini produce and secrete enzymes through the pancreatic duct into the duodenum.
How is insulin secretion stimulated in beta cells?
- At normal blood glucose concentrations, the membrane is polarised as K+ channels are open.
- Glucose enters the cell by a glucose-transporter protein.
- Metabolised by mitochondria, ATP produced.
- ATP binds to ATP-sensitive K+ channels.
- K+ cannot diffuse out, therefore membrane depolarises.
- Ca2+ ions enter the cell, causing secretory vesicles to fuse with the CSM, releasing insulin by exocystosis.
What are the types of hormones?
- Steroid: lipid-soluble, pass through membrane, bind to receptors forming hormone-receptor complexes (this acts as a transcription factor or inhibits the transcription of a specific gene).
- Non-steroid: hydrophobic, cannot pass directly through. Bind to receptors on CSM, rely on secondary messengers to bring about change through mediating a cascade of reactions.
What is the histology of the different pancreatic tissues?
- Acini: darker, berry-shaped.
- IoL: lighter, spherical.
How can blood glucose conc be reduced?
- Increase respiration.
- Increase absorption by skeletal muscle and liver cells.
- conversion of glucose –> glycogen (glycogenesis) or fat.
- Inhibit glucagon production/secretion.
How can blood glucose conc be reduced?
- Increased gluconeogenesis.
- Decreased absorption by liver.
- Increased glycogenesis.
How does insulin act on target cells?
- Muscle cells, fat storage cells, adpiose tissue and liver cells all have glucose transporter proteins in their CSM.
- These are insulins target cells.
- The glucose-transporter proteins allow for glucose uptake by fac. diff.
- Insulin also binds to specific receptors which open the GTPs/add more to the membrane.
How does glycogenesis occur in the liver?
- Glycogen is converted to glucose phosphate then glucose.
- This maintains the conc. gradient in liver cells.
