Endocrine system and Fight/flight

Question 1

The Endocrine System

Answer 1

The endocrine system is the collection of glands
that produce hormones that regulate metabolism,
growth and development, tissue function, sexual
function, reproduction, sleep, and mood

The hypothalamus, a collection of specialized cells
that is located in the lower central part of the
brain, is the main link between the endocrine and
nervous systems

Question 2

Glands and Hormones

Answer 2

• The endocrine system works alongside the nervous system to control vital functions in the body. The endocrine system acts more slowly that the nervous system but has very widespread and powerful effects. Some basics you need to know…
• Glands in the body produce hormones
• Hormones are secreted into the bloodstream and affect any cell in the body that has a
  receptor for that particular hormone.
• The main gland is the pituitary gland which is located in the brain. It controls the release of
  hormones from all the other endocrine glands in the body.

Question 2

HYPOTHALAMUS

Answer 2

• Sends signal to pituitary gland
• Via ‘secreting hormone’ eg. CRH

Question 2

PITUITARY GLAND

Answer 2

• Secretes a stimulating hormone into bloodstream
• Via ‘stimulating hormone’ eg. ACTH

Question 2

TARGET GLAND

Answer 2

• Eg. Adrenal gland then produces target hormone
• Eg. Cortisol
• Hypothalamus then shuts down secreting hormone and pituitary shuts down stimulating hormone, balancing target hormone levels

Question 2

Pituitary Gland

Answer 2

2 Main Parts:

1. Anterior Pituitary (front)
2. Posterior Pituitary (back)

• Release different hormones, targeting different parts of the body.
• E.g. Anterior releases ACTH as a response to stress. (ACTH stimulates the adrenal glands to produce
  cortisol). Anterior also produces LH and FSH – important in control of reproductive functioning.
• In females, stimulate ovaries to produce oestrogen and in males, stimulate testes to produce testosterone
  and sperm.
• Posterior releases oxytocin, which simulates

Question 2

Physiological Stress Response

Answer 2

• Stress can be acute or chronic
• In an acute stress reaction, which hormone do you think we
  release?
• What are the effects of this hormone?

Question 2

Negative Feedback Loop

Answer 2

• The endocrine system receives feedback from the hormones secreted by
  the target gland.
• The hormones are detected and the hypothalamus responds by shutting down secretion of releasing hormones, making the pituitary gland shut down secretion of stimulating hormones.
• Thereby, the endocrine system works via a negative feedback loop.

Question 2

Acute stressors activate the Sympathetic Adrenal-medullary
Pathway

Answer 2

• The SAM pathway involves the amygdala sensing danger and alerting the hypothalamus.
• This sends a message to the adrenal medulla, part of the adrenal gland in the kidneys.
• The adrenal medulla then releases adrenaline (stress hormone) into the bloodstream, stimulating the body and making it work faster and more efficiently, to deal with the stress.

Question 2

Chronic Stress Response

Answer 2

• This is an example of chronic stress. You can’t fight or flight you boss (arguably…) you have to cope with him/her
• If a stressor is chronic (on going) and cannot be dealt with by SAM, then our bodies use the HPA.
• HPA = hypothalamic pituitary adrenocortical axis
• The Hypothalamus triggers the Sympathetic Nervous System (SNS).
• This stimulates the endocrine system, which helps us to manage constant stress.
• This is a hormonal response (inc eg cortisol) and travels through the blood
• This a slower response than SAM.

Question 2

Fight or Flight Response: Effects of Adrenaline

Answer 2

• Increased heart rate
• Relaxation of the bronchi of the lungs
• Pupil dilation / expansion
• Glucose (energy store in liver) is released
• Reduced activity within the stomach
• Saliva production is inhibited

Question 2

Chronic Stress Response: HPA axis (1)

Answer 2

H: The hypothalamus activates the SNS. The hypothalamus releases corticotrophin-releasing
hormone (CRH) , which is released into the bloodstream.

P: CRH causes the pituitary gland to release adrenocorticotrophic hormone (ACTH) which travels
through the bloodstream to target glands.

A: ACTH stimulates the adrenal cortex to release various hormones, inc cortisol. This aids the
fight-or-flight response, inc giving a quick burst of energy and lowered pain sensitivity.

The body is now prepared to deal with constant stress and is more tolerant to pain

However chronic stress damages your body. The liver is stimulated to release glucose, which suppresses the immune system & impairs cognitive ability.

Question 2

Parasympathetic nervous system

Answer 2

When the threat has passed, the parasympathetic nervous system
dampens down the stress response, bringing the body back to
normal. For example, the PNS slows heart rate and reactivates
digestion.

Question 2

Chronic Stress Response: HPA axis (2)

Answer 2

• Once ACTH & cortisol are circulating in the bloodstream, they tend to stop more ACTH being released from the pituitary.
• If the stressor is removed, blood sugar levels will gradually return to normal. But if the stressful situation continues, so will the pituitary-adrenal excitation. By this time:
• the body’s resources are becoming depleted
• the adrenals can no longer function properly
• blood glucose levels drop; in extreme cases, hypoglycaemia could result in death
• psychophysiological disorders develop: these include high blood pressure (hypertension), coronary artery disease (CAD), coronary heart disease (CHD), asthma & peptic (stomach) ulcers.

Question 3

A03 Fight or Flight: The ‘tend and befriend’ response

Answer 3

Taylor et al. (2000) suggest that, for females, behavioural responses to stress are more characterised by a pattern of tend and befriend than fight or flight. This involves protecting themselves and their young through nurturing behaviours (tending) and forming protective alliances with other women (befriending). Women may have a different system for coping with stress because their responses evolved in the context of being the primary caregiver of their children. Fleeing at any sign of danger would put a female’s offspring at risk. This finding, explained in terms of the higher levels of the hormone oxytocin in females, suggests that previous research, which has mainly focused on males, has obscured patterns of stress response in females.

Question 3

A03 Fight or Flight: Negative consequences of the fight-or-flight response

Answer 3

The physiological responses associated with fight or flight may be adaptive for a stress response that requires energetic behavioural responses. However, the stressors of modern life rarely require such levels of physical activity. The problem for modern humans arises when the stress response is repeatedly activated. For example, the increased blood pressure that is characteristic of SNS activation can lead to physical damage in blood vessels and eventually to heart disease. As a consequence, although cortisol may assist the body in fighting a viral infection, too much cortisol suppresses the immune response, shutting down the very process that fights infection and increasing the likelihood of stress-related illness.

Question 3

A03 Fight or Flight: ‘Fight or flight’ does not tell the whole story

Answer 3

Gray (1988) argues that the first phase of reaction to a threat is not to fight or flee, but to avoid confrontation. He suggests that, prior to responding with attacking or running away, most animals (including humans) typically display the ‘freeze response. This initial freeze response is essentially a ‘stop, look and listen’ response, where the animal is hyper-vigilant, alert to the slightest sign of danger. The adaptive advantages of this response for humans are that ‘freezing’ focuses attention and makes them look for new information in order to make the best response for that particular threat.