Physical Responses to Stressors

Physical Responses to Stressors

Imagine a near miss: As you step off the curb, a car speeds toward you. With just a fraction of a second to spare, you leap safely out of harm’s way. In that split second of danger and in the moments following it, you experience a predictable series of physical reactions. Your body goes from a relaxed state to one prepared for physical action to cope with a threat to your life.

Two systems in your body are responsible for your physical response to stressors: the nervous system and the endocrine system. Through rapid chemical reactions affecting almost every part of your body, these systems allow you to act quickly and appropriately in time.

Actions of the Nervous System The nervous system consists of the brain, spinal cord, and nerves. Part of the nervous system is under voluntary control, as when you tell your arm to reach for a chocolate. The part that is not under conscious supervision for example, the part that controls the digestion of the chocolate is the autonomic nervous system. In addition to digestion, it controls your heart rate, breathing, blood pressure, and hundreds of other involuntary functions.

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The autonomic nervous system consists of two divisions:

• The parasympathetic division is in control when you are relaxed. It aids in digesting food, storing energy, and promoting growth.

• The sympathetic division is activated during times of arousal, including exercise, and when there is an emergency, such as severe pain, anger, or fear.

Sympathetic nerves use the neurotransmitter norepinephrine (or noradrenaline) to exert their actions on nearly every organ, sweat gland, blood vessel, and muscle to enable your body to handle an emergency. In general, the sympathetic division commands your body to stop storing energy and to use it in response to a crisis.

Actions of the Endocrine System During stress, the sympathetic nervous system triggers the endocrine system. This system of glands, tissues, and cells helps control body functions by releasing hormones and other chemical messengers into the bloodstream to influence metabolism and other body processes. These chemicals act on a variety of targets throughout the body. Along with the nervous system, the endocrine system prepares the body to respond to a stressor.

The Two Systems Together How do both systems work together in an emergency? Let’s go back to your near-collision

Pupils dilate to admit extra light for more sensitive vision.

Mucous membranes of nose and throat shrink while muscles force a wider opening of passages to allow easier airflow.

Secretion of saliva and mucus decreases; digestive activities halt in an emergency.

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