The Endocrine System & the Fight or Flight Response

The endocrine system

One of the body's major information system that provides a chemical system of communication via the bloodstream. The endocrine system instructs glands to produce and secret a range of hormones into the bloodstream to regulate the activity of cells and organs in the body and thus, bodily functions

- The endocrine system works alongside the nervous system to control vital functions in the body
- The endocrine system works much more slowly than the nervous system

Hypothalamus

Stimulates and controls the release of hormones from the pituitary gland

Pituitary gland

Sometimes known as the master gland because the hormones released by this gland control and stimulate the release of hormones from other glands

Pineal gland

Releases melatonin
Responsible for important biological rhythms, including the sleep-wake cycle

Thyroid gland

Releases thyroxine
Responsible for regulating metabolism

Adrenal gland (medulla)

Releases adrenaline and noradrenaline
The key hormone in the fight or flight response

Adrenal gland (cortex)

Releases cortisol
Stimulates the release of glucose to provide the body with energy, while suppressing the immune system

Testes (male)

Releases testosterone
Responsible for the development of male sex characteristics during puberty whilst also promoting muscle growth

Ovaries (female)

Releases oestrogen
Controls the regulation of the female reproductive system, including the menstrual cycle and pregnancy

Q. Using an example of a gland and hormone, outline the function of the endocrine system. Do not use the adrenal gland / adrenaline in your answer (4 marks)

The endocrine system uses a chemical system of communication to stimulate the release of hormones from certain glands. This regulates the activity of cells and organs in the body. One example of such a gland is the thyroid which releases thyroxine to increase heart rate and metabolic rate

The Fight or Flight Response

The fight or flight response occurs when the body becomes physiologically aroused in response to a stressor. During a stressful event the endocrine system and the autonomic nervous system work together to fight or flight and overcome the stressor

Describe the process of the fight or flight response

1. Stressor is perceived e.g. someone jumps out to frighten you
2. The hypothalamus activates the pituitary gland
3. This triggers the nervous system
4. Adrenaline is released from the adrenal medulla (part of the adrenal gland)
5. This then triggers physiological changes in the body (e.g. increased heart rate) which creates a physiological arousal necessary for the fight or flight response
6. Once the stress has passed, the parasympathetic nervous system returns the body to its resting state. The parasympathetic branch of the autonomic nervous system works in opposition to the sympathetic nervous system - its actions are antagonistic to the sympathetic nervous system
7. The 'rest and digest' response - the parasympathetic nervous system acts as a brake and reduces the activities of the body that were increased by the sympathetic branch

Q. Outline the function of adrenaline in the fight or flight response (4 mark)

Adrenaline is secreted from the adrenal medulla into the bloodstream, leading to a number of physiological changes. Firstly, our heart rate increases due to thyroxine being released from the thyroid gland which allows blood carrying oxygen to be delivered to muscles at a faster rate. Secondly, our pupils dilate for a wider scope of vision in order to be able to see and react to danger more efficiently, and thirdly, there is a reduction in the functioning of non-essential processes e.g. the digestive system so that respiration and other vital functions can be prioritised so the person has maximum energy to fight or flee as necessary

Beta bias of the fight or flight response

Whilst early research into fight or flight suggested that both sexes responded in the same manner, the fight or flight response is now accepted to be more of a male response. According to Taylor, women are more likely to protect their offspring (tending) and form alliances with other women (befriending), rather than fight an adversary or flee, in stressful situations. This is beta bias whereby the fight or flight response theory minimises and ignores the differences between men and women, instead favouring an androcentric perspective. This shows the theory may not be accurate for women and so should not be generalised

Fight or flight is reductionist

Gray suggests that the first response to danger is not to fight or flight but to avoid confrontation altogether, which is known as freezing. This means the fight or flight theory is reductionist as it is oversimplifies the complexity of reacting to danger such that the theory is incomplete, causing a loss of validity