Organs involved in the stress response

Heart-Controls blood pressure and blood-flow

Adrenal gland-Releases adrenaline, noradrenaline and cortisol

Kidneys-Purify the blood

Hypothalamus-Controls the nervous system

Pituitary gland-Controls the release of hormones

Lungs-Control resperation

Stress can be defined as-When the pressure on someone exceeds what they can cope with and it becomes damaging.

Stress occurs when a persons environmental and social demands are greater than their percieved ability to cope. When stressed, our body prepares us for fight or flight. The stress response involves 2 major systems: one for acute stressors i.e. personal attack, a second for chronic stressors i.e. a stressful job. Our nervous and endocrine systems are involved.

The nervous system

Divided into central nervous system involving neurones in the brain and spinal cord. Peripheral nervous system nerves outside the spinal cord and brain carrying information to and from the body. Autonomic nervous system is part of the PNS which acts automatically. The sympathetic branch is involved in stimulating the body. The parasympathetic branch is involved in returning the body to a relaxed state.

The endocrine system

A system of glands that release hormones into the blood. The pituitary gland in the brain is the master gland and controls all parts of this system. The adrenal gland releases important stress hormones such as adrenaline, noradrenaline and cortisol.

Acute Stress

Sympathomedullary system (SAM)

This system is very fast at responding

  • Stressors stimulate the central brain
  • The hypothalamus activates the sympathetic branch of the ANS
  • The sympathetic branch sends a signal to the adrenal medulla
  • The adrenal medulla releases adrenaline and noradrenaline
  • Adrenaline increases heart rate and the supply of oxygen and glucose to the brain and muscles

Chronic Stress

Pituitary adrenal system (PAS)

This system is not as fast as the above but it keeps the stress response going

  • Stressors are sensed in the cortex
  • The hypothalamus signals the pituitary gland to release adrenocortrophic hormone (ACTH)
  • ACTH causes the adrenal cortex to release coticosteriods, mainly cortisol
  • Cortisol causes a quick burst of energy but it can also lower the immune system.

Stress related illness

Hans selye developed the General Adaptation Syndrome (GAS) to describe how our physical reactions to stress can lead to illness. It has 3 stages.

Stage 1:  Alarm stage-The systems that deal with the stressor e.g. SAM and PAS. Heart rate increases, breathing increases and glucose levels rise.

Stage 2:  Resistant stage-Stable level. The body tries to adapt to the ongoing stressor and reaches a stable level.

Stage 3: Exhastion stage-If stress continues, we are less able to deal with it, our immune system becomes less efficent and we can become ill. This is called immunosuppresion.

The immune system is our main defence against infection by forgien agents. Any agent that stimulates an immune response is called an antigen. Key players in our immune system are the white blood cells which are made in the bone marrow and circulate in the bloodstream. The two types of white blood cells are called lymphocytes and phagocytes. Phagocytes are cells that


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