Lecture 15: The Stress Response Flashcards
Where is the hypothalamus located?
Base of brain and Centre of Limbic region
At the bottom centre of the brain
What is the role of the Hypothalamus?
Releasing and inhibiting hormones, released from axon termini nerve, to control the pituitary
(influences what the anterior pituitary does)
How many hormones does the Hypothalamus release?
9 hormones
all affect the pituitary gland
Where is the pituitary gland located?
2 lobes on a stalk
posterior and anterior
What is the name of the stalk which connects the 2 lobed pituitary gland and the hypothalamus?
infundibulum
What is the Infundibulum?
Stalk which connects the two lobed Pituitary Gland to the Hypothalamus
Blood vessels
Hypophyseal Portal Vein= at the base of the hypothalamus there is a capillary network which go into veins which travel down the infundibulum to a second capillary network in the anterior pituitary gland.
This system allows in the hypothalamus to secrete hormones which travel down down to pituitary capillary network which travel to pituitary gladden and stimulate those cells to do something
What is the role of the Pituitary?
controlling endocrine organs via release into blood stream, and control what those endocrine organs make or don’t make
Hormones travel through a portal vein –> to secondary plexus —> then to pituitary target cells
How many hormones does the Pituitary release?
7 hormones
In combination, what do the Hypothalamus and Pituitary do?
Together regulate growth, development, metabolism, homeostasis Control endocrine system and many of our bodily functions Portal system (Hypophyseal) to allow communication between hypothalamus and Pituitary
What is the Adrenal Gland?
“Ad-Renal” (“ontop” of “Kidney”) Triangular organ sitting on top of the Kidney, in the Retroperitoneal Space
2x Structurally and Functionally distinct areas
-cortex –> 80-90%
-medulla (middle)
Highly Vasculated
Produces Steroid Hormones
What system is the Adrenal Gland closely linked with?
Sympathetic Autonomic Nervous System
What is the Adrenal Medulla similar to?
Modified Ganglion
How does the Adrenal Gland work in synchrony with the Sympathetic Nervous system.
Part of the sympathetic nervous system that is not acting through a ganglion switching station, but is acting directly on the adrenal medulla to cause its cells (modified post ganglionic neurons) to secrete hormones (epinephrine and norepinephrine) into the blood stream, to effect heart(cardiac muscle), Smooth muscle and glands
What are the cells of the Adrenal Medulla?
Modified PostGanglionic “Neuron”
(don’t have long axons extending out, instead have cells completely contained in the adrenal medulla).
and when these cells are stimulated by sympathetic autonomic signals into the bloodstream, release Neurotransmitters/hormones NE and E.
What is the role of the hormones Norepinephrine and Epinephrine?
Sustained action
What is the adrenal medulla stimulated by?
ACh
fromm the Preganglionic Neurons
What hormones are released by the adrenal medulla?
Epinephrine
Norepinephrine
What is the Principal action of the Adrenal Medulla?
Enhances the sympathetic autonomic Alarm response
-Neurotransmitters sent through blood stream to circulate
-affect tissue in a more prolonged way - Slow effect - more Sustained action than the Autonomic System Activation
-this can Enhance and Extend Activation process
several seconds later has an affect
What is the First stage of the Sympathetic Autonomic Flight or Flight Response?
(Inducible) Immediate burst of action
Sympathetic autonomic activation
Sustained through action of Adrenal Medulla - E and NE
What is the Second stage of the Sympathetic Autonomic Resistance Reaction?
Slower (more endocrine manner)
In response to signals from pituitary
Longer lasting
Enhances effected by sympathetic activated cells
Associated with the hypothalamus, pituitary and Adrenal Cortex (cortisol)
What is the First stage of the Stress Response?
sympathetic autonomic activation
Mobilise resources for immediate physical activity
Immediate action of Glucose and Oxygen consumption
Alertness and Activity
What is the Second stage of the Stress Response?
Reduces tissue damage
Ward off danger, or flee
What is Hormone A produced by the Adrenal Cortex?
Mineralocorticoids
e.g. aldosterone
From the adrenal cortex which regulates mineral ion concentration
What are Mineralocorticoids simulated by?
Increased K+ and Angiotensin II in the blood
What are the Principal Actions of Mineralocorticoids?
Increased Na+ and water -> reabsorption
Decreased K+ in blood (increase blood volume and pressure)
What is Hormones B produced by the Adrenal Cortex?
Glucocorticoids
e.g. cortisol
What are Glucocorticoids stimulated by?
ACTH (adrenocorticotropic hormone) from the Pituitary Gland (CRH from Hypothalamus)
Goes through blood stream and Stimulates the adrenal cortex (“adrenocortico”) to make cortisol
What are the Principal Actions of Glucocorticoids?
Dampen inflammation (inflammatory responses)
Resistance reaction to stress –> upregulate processes
Alter immune response as can cause damage themselves
What are the 7 actions of Cortisol?
- increase protein breakdown (especially in muscle)
- Gluconecgenesis in liver
- Lipolysis in adipose tissue
- Altered blood vessel sensitivity to vasoconstriction
- Anti-inflammatory to limit tissue damage
- Alters immune responsiveness
- Resistance to stress
What is the consequence of increased Protein Breakdown due to cortisol release?
in muscles
Amino acids are available for new protein synthesis
- to reform tissue
-also ATP
What ist he consequence of Glycogenesis in the Liver due to cortisol release?
To breakdown Carbohydrates, Amino acids and Lactic Acid into Glucose,
which cells can use for ATP production in order to rebuild
What is the consequence of Lipolysis in adipose tissue due to cortisol release?
Breakdown of triglycerides and release of fatty acids from adipose tissue into the blood for availability
–> building blocks for making complex lips as fatty tissue is rebuilt
What is the consequence of Altered Blood Vessel Sensitivity to Vasoconstriction due to cortisol release?
Blood vessels become more sensitive to hormones that causes vasoconstriction, therefore/enhance Less Elastic, and
therefore rise/maintain in Blood Pressure
What is the consequence of being Anti-inflammatory in order to limit tissue damage due to cortisol release?
Inhibit white blood cells to take part in inflammatory responses
to limit tissue damage by them
but also leads to slow tissue repair and wound healing so don’t want to slow down too much
What is the consequence of Alteration of the Immune responsiveness due to cortisol release?
depress immune responses due to high glucocorticoid concentration
at expense of longer term immune responses
What is the consequence of resistance to stress due to cortisol release?
Increased glucose and ATP combat stresses such as (10) exercise fasting fright temperaturen extreems high altitude bleeding infection surgery trauma disease
What is the overall consensus of cortisol release?
All these actions are good in Transient ways, but need to be moderated as if in excess (harmful) (e.g. slowing wound repair by being too anti-inflammatory)
resistance reaction needs to have “dimmer control” in order to be able to up and down regulate
NEGATIVE feedback mechanism
Glucocorticoids are essential in order to be able to rebuild up tissues, and helps deal with tissue injury, but should be relatively short term process (similar to autonomic)
What does Cortisol’s Negative feedback loop consist of?
- CRH —via portal system –>
- ACTH —>
- adrenal cotex —>
- cotrisol release —>
- elevated cortisol inhibits release of ACTH by anterior pituitary corticotrophs
- elevated cortisol inhibits release of CRH by hypothalamic Neurosecretory cells
Why is the Cortisol Negative feedback loop essential?
So that the cycle doesn’t get out of control and the system get overloaded
What is the two parts of the stress response?
- Immediate response when we see danger/stress, driven by sympathetic NS. Sustained by NE and E from the Adrenal Medulla
- slightly slower resistance reaction coming from purely endocrine pathways –> production of cortico steroids/glucocorticoids (cortisol in case of humans) –> slower ing getting out of the way, longer lasting, facilitating tissue repair in a limited way, useful in injury
What is the immediate response symptoms?
Alarm response: fight or flight
- pounding heart
- cold sweat
- goose flush
- rapid breathing
What are the sustained response symptoms?
Desirable as long as under control (feeds back to inhibit its production)
Resistance reaction:
1. increased glucose, fatty acids, amino acids
2. sensitised vessels (increased BP)
3. reduced inflammation
4. immune suppression (reduced immunity)
Why is the resistance reaction longer?
As it is fluid driven not nerve driven
What are the Neuro-immune links?
Autonomic Nerves
Hormones
Cytokines
What is the role of the Autonomic nerves in Neuro-Immune links?
Neuroendocrine –> immune
Sympathetic and para sympathetic
*Nervous system affects immune functions (in more ways than cortisol)
co-ordinating immunity(B and T cell production)
*Autonomic nerves of into secondary lymphoid organs and influence the way lymphocytes respond to foreign material and produce antibody responses to deal with infectious agents
What is the role of Hormones in Neuro-Immune links?
Neuroendocrine –> Immune
e.g. cortisol can modulate immune function
charge balance
What is the role of Cytokines in Neuro immune links?
Immune –> Neuroendocrine
Immune hormone-immune system controls itself using cytokines
Also it influences (communicating) the brain and the way the nervous system interacts –> and therefore behaviour and metabolism
What is the Neuroendocrine system?
system which perceives to be threat –> coordinate
What does the Immune system?
system with threats from infectious agents
How are Neuro-immune links activities co-ordinated?
Bidirectional Communication
Modulate Each other
