9.3 Stress Response and Blood Sugar

Regulate Stress Response

Regulate Blood Sugar

Stress Response

Involves hormone pathways

that regulate metabolism,

heart, rate and breathing

The Adrenal Glands

a pair of organs

Composed of 2 layers:

1. Adrenal medulla (inner layer)

Regulated by nervous system

2. Adrenal cortex (outer layer)

Regulated by hormones

Adrenal Medulla: Short-term Stress Response

In response to a stressor:

Neurons in the sympathetic nervous system carry a signal from the hypothalamus to the adrenal medulla (fight-or-flight response)

adrenal medulla secretes epinephrine and norepinephrine

increase in breathing rate, heart rate, blood pressure, blood flow to the heart and muscles, and the conversion of glycogen to glucose in the liver

Epinephrine works quickly

can be used in anaphylactic

emergencies to open up air

passages and restore

breathing (eg. Epi-pen)

Adrenal Medulla: Short-term Stress Response

Produces 3 types of hormones:

1. Glucocorticoids:

Cortisol is the most abundant

increases amino acids in blood to recover from stress

The liver converts the amino acids into glucose to produce energy during times of stress

2. Mineralocorticoids:

Aldosterone increases sodium retention in the blood and water reabsorption by the kidneys to increase blood pressure

3. Small amounto of sex hormones

Adrenal Cortex: Long-term Stress Response

The hypothalamus secretes a releasing hormone

anterior pituitary gland secretes adrenocorticotropic hormone (ACTH)

adrenal cortex secretes cortisol

Promotes breakdown of fats and muscle protein to increase blood glucose levels

also an anti-inflammatory and immune system suppressant

Adrenal Cortex: Long-term Stress Response

Cortisol levels are controlled in a

negative feedback loop

High level of cortisol in the blood can

inhibit the release of tropic hormones

from the hypothalamus or pituitary

However, chronic high levels of

cortisol can impair thinking, damage

the heart, and cause early death.

Adrenal Cortex: Long-term Stress Response

Addison’s Disease

Damage to adrenal cortex

insufficient glucocorticoid and mineralocorticoid secretion

low blood sugar (hypoglycemia), sodium and potassium imbalances, and weight loss

need to be treated within a few days because it can be fatal

Regulating Blood sugar:

Pancreas

involved in both the digestive and

endocrine systems

over 2000 islets of Langerhans (endocrine cells) scattered

throughout the pancreas

beta cells secretes insulin – lowers blood glucose

alpha cells secretes glucagon – increases blood glucose

Both hormones are regulated by negative feedback loops

Hormones of Pancreas

When blood sugar levels are high:

beta cells release insulin

Makes cells in the liver, muscles

and adipose tissue more

permeable to glucose

Lowers blood glucose

Hormones of Pancreas

When sugar levels are low

alpha cells release

glucagon

Stimulates the liver and

adipose tissue to break

down glycogen or fat

increase blood sugar

levels

Diabetes Mellitus

1. body does not produce enough insulin

2. or does not respond properly to insulin

Glucose stays in the blood after meals instead of entering the cells

Hyperglycemia (high blood sugar but no sugar in the cells)

Fatigue

begins to use fat and protein for metabolic energy

glucose is excreted in the urine

Over the long term, permanent damage to the eyes, nerves, and kidneys. Severe infection (gangrene) can occur in the limbs.

Interpreting Blood Sugar Levels

Causes of Diabetes

Type 1 (Juvenile Diabetes):

immune system attacks and destroys beta cells in the pancreas

diagnosed in childhood

need daily insulin injections

Type 2 (Adult-Onset Diabetes):

Insulin receptors on the body’s cells stop responding to insulin

overweight greater chance of developing this condition

usually diagnosed in adulthood

can be controlled with diet, exercise, and oral medications

Type 1

Toward a Cure for Diabetes

In 1921, Canadian scientists Frederick Banting and Charles Best isolated insulin and use it successfully to treat a person with diabetes.

Today, transgenic bacteria are used to produce synthetic insulin in large quantities for diabetes treatment.

Successful islet cells transplants have also been performed to restore beta cell function.