Biopsychology - The Endocrine System + Fight or Flight

The Endocrine System

The network of glands in the body that produce + secrete hormones. Works alongside the nervous system to control vital bodily functions.

Glands

Secrete and produce hormones. Many different ones/types (e.g. Pituary gland, adrenal gland). Different glands produce different hormones.

Hormones

Chemical messengers that travel in the bloodstream (unlike neurotransmitters). Only effect target cells with receptors for specific hormones. When enough receptors are stimulated by hormones this causes a physiological reaction (change) in a target cell. 

Target cells

Cells with the receptors for a specific hormone and therefore can effected by this type of hormone. When enough of these receptors are stimulated by hormones a physiological reaction is caused in the cell. 

Pituitary Gland

Also known as the master gland, this controls the release of hormones from all other endocrine glands in the body. It is located in the brain, next to the hypothalamus. PG releases a stimulating hormone for a target gland (hormone travels through the bloodstream) which causes it to release a specific hormone as a result of the hypothalamus secreting a specific releasing hormone.

Hypothalamus (in the endocrine system)

A part of the brain, next to the pituitary gland. Controls the release of hormones by controlling when and what hormones the pituitary gland releases and causes target glands to secrete. The hypothalamus does this by secreting a specific type of releasing hormone. When hormone level (released by the target gland) rises in the bloodstream the hypothalamus shuts down secretion of the releasing hormone and this stops all related hormone secretion. This continued secretion and shut down by the hypothalamus results in a stable concentration of hormones circulating in the blood stream.

How is a stable concentration of hormones in the bloodstream maintained??

Hypothalamus recognises low level of a specific hormone in the bloodstream —> hypothalamus secretes a releasing hormone —> pituitary gland recognised this + consequently releases a stimulating hormone into bloodstream —> target gland secretes the specific hormone when stimulating hormone reaches it —> specific hormone level rises in the bloodstream —> hypothalamus shuts down secretion of releasing hormone —> PG shuts down secretion of stimulating hormone —> target gland shuts down secretion of specific hormone —> REPEAT

Adrenal Gland

Releases the hormone adrenaline when an individual is stressed or fearful. This triggers the Fight or Flight response by causing bodily changes including: increased heart rate + increased breathing rate.

Thyroid Gland

Produces the hormone thyroxine which regulates a wide range of bodily functions. This includes: metabolism, digestion + heart rate. It is also in part responsible for growth and development.

Pineal Gland

Produces the hormone melatonin which regulates the sleep-wake cycle. Melatonin is released when it gets dark to induce sleep.

Fight or Flight response

The body’s specific reaction when an individual is faced with a threat. It is evolved as a survival mechanism to enable humans to react quickly to life-threatening situations. Involves: Adrenaline, the sympathetic nervous system and the parasympathetic nervous system. 

What happens in the fight or flight response?

1. A person is faced with a threat

2. The amygdala is activated + sends distress signals to hypothalamus

3. Hypothalamus activates SAM pathway

4. Sympathetic nervous system is activated

5. This stimulates the adrenal medulla to secrete adrenaline into the bloodstream

6. Adrenaline causes physiological changes 

7. Parasympathetic nervous system is activated + causes body to return to a state of relaxation (rest + digest)

Sympathomedullary (SAM) Pathway

Abbreviated as the SAM pathways. Allows the sympathetic nervous system (responsible for causing fight or flight) to be activated. SAM pathway is activated by the hypothalamus

Amygdala

A tiny part of the brain located in the temporal lobe. Sends distress signals to the hypothalamus when a person is faced with a threat.

Adrenal medulla

A part of the adrenal gland that secretes the hormone adrenaline into the bloodstream. This hormone causes the fight or flight response.

Sympathetic Nervous System

Part of the Autonomic nervous system. Works alongside the endocrine system. Brings about the fight or flight response when an individual is faced with a threat. 

Parasympathetic nervous system

Part of the Autonomic Nervous System. Works Alongside the endocrine system. Brings an individual back to their resting state once a threat has passed (rest and digest).

Increased Heartrate (Physiological change)

Adrenalin causes increased blood flow to skeletal muscles

Increased breathing rate (Physiological change)

Adrenalin causes increased oxygen intake

Pupil dilation (physiological change)

Adrenalin causes this so there is increased light entry into the eye so the individual has improved vision

Sweat production (physiological change)

Adrenaline causes this so the individual can regulate their temperature.

Reduction of non-essential functions (physiological change)

Adrenalin causes this so the individual has increased energy for other essential functions.

CON - Fight or Flight - Tend and Befriend

One weakness of the fight or flight response is that early research was conducted on males and recent research suggests that this response cannot be generalised to females. Taylor et al (2000) suggested women are more likely to protect their offspring (tend) and form alliances with other women (befriend) than fight or flee. Therefore, this is beta-bias within this area of psychology as differences between males and females have been ignores.

CON - Fight or Flight - Freeze

One weakness of the fight or flight response is that it has been adapted from its original research in order to include the freeze response. Gray (1988) suggested the ‘freeze’ is the initial response is the initial response to a threat when the individual is hyper-vigilant, assessing the threat and deciding on the best course of action. Therefore, the original form of the flight or flight response in an incomplete description.