Stress Flashcards
What is stress?
It is the general term for any condition that actually or potentially poses a serious challenge to the body ability to maintain homeostasis
State some physical symptoms of stress
Dehydration Haemorrhage Infection Surgery Temperature fluctuations
How is the body physiological homeostasis monitored?
Via the central nervous system via the hypothalamus in the brain stem
Which pathway is physiological homeostasis controlled by?
The sympathetic pathways
Slower maintenance is via the endocrine system with secretion from the adrenal glands
What are the two pathways can a stress response take?
Rapid short term response: Fight to flight
Long lasting body response under the endocrine control
Which part of the brain stimulates the sympathetic portion of the autonomic nervous system?
The hypothalamus
The hypothalamus stimulates what?
The sympathetic portion of the anatomic nervous system and the endocrine system via the adrenal glands in the high or flight response
What so the adrenal glands release during the fight or flight response?
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Describe the actions of the sympathetic nervous system?
- Nerve endings release noradrenaline
- This increases the heart rate and stroke volume ultimately increasing cardiac output
- Constriction of blood vessels increases. This increases blood pressure
- Blood is diverted from no essential organs to the brain, heart and skeletal muscles
- Ventilation increases
- Sweating may occur
Describe the actions of the adrenal medulla?
- Preganglionic nerve endings stimulate the adrenal medulla
- Adrenal medulla releases catecholamines (adrenaline and noradrenaline)
What is the adrenal glands made of?
2 Small glands:
The inner region: are activated in brief response systems
Outer region: activated in more pre longed lasting responses
What is the inner region of the adrenal glands?
The adrenal medulla
What is the outer region?
The adrenal cortex
Where are the adrenal glands found?
Above the kidneys
What does the adrenal medulla secrete and in what proportion?
Secretes:
Adrenaline 80-90% of cells
Noradrenaline 10-20% of cells
Where are the adrenaline and noradrenaline stored in the adrenal medulla?
They are stored in secratory granules
What stimulate the release of adrenaline and noradrenaline from the secretary granules in the adrenal medulla?
They are released when stimulates by the preganglionic fibres of the sympathetic nervous system
What type of actions does the sympathetic nervous system produce?
Rapid short term actions with rapid release that have a quick action on target cells and a very short life span of activation
What is adrenalines half life?
They have a short half life of 10s
What are the biological effects of catecholamine release?
Re-enforces the actions of the sympathetic nervous system
What receptors do the catecholamine act on?
Alpha 1 Alpha 2 Beta 1 Beta 2 Beta 3
What processes does atecholamine adrenaline stimulate?
Increased Glycogenesis
Increased Gluconeogenesis
Increased Mobilisation of free fatty acids
What is Glycogenesis?
Breakdown of stored of glycogen to release glucose in the blood stream
(ie increases the blood glucose concentration in the blood)
What is Gluconeogenesis?
Release of glucose from pre-cursors in the liver which ultimately increases the blood glucose concentration in the blood
What happens when mobilisation of are fatty acids is increased?
Glucose is released into the blood stream and the are fatty acids are used as an energy source
What is the biological effect of noradrenaline?
Causes vasoconstriction which increases the total peripheral resistance and increases cardiac output
Which receptors does noradrenaline work on?
Alpha 1 receptors
What is the biological effect of adrenaline?
May cause vasodilation in skeletal muscles
This increases oxygen supply to the muscles
Which receptors does adrenaline work on?
Beta 2 receptors in skeletal muscles
Which of the two: noradrenaline or adrenaline has a more potent effect on peripheral vasoconstriction and blood pressure
Noradrenaline
What does adrenaline have a more potent effect on?
The heart
Metabolic activities
What do both noradrenaline and adrenaline do?
They both inhibit insulin and stimulate glucagon which enables ample levels of glucose to be available in the body for use as an energy source
What do both noradrenaline and adrenaline act to support?
The sympathetic system in times of stress
What does familiar emotional stress tend to increase?
The release of noradrenaline