H4: Hormones that Affect Blood Sugar Levels

Blood Glucose/Sugar Levels

Available glucose in blood for immediate use

* normal levels: 4.0 - 5.5 mmol/L
* monitored by beta cells in pancreas (glucose receptors)

Pancreas

Situated behind stomach; both exocrine & endocrine gland

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**Exocrine:** Accessory organ in digestive system; performed by cells that secrete digestive enzymes

* pancreatic juice enters duodenum
* amylase - carb digestion
* lipase - lipid digestion
* trypsin, chymotrypsin & carboxypeptidase - protein digestion

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**Endocrine:** Performed by small glandular structures (islets of Langerhans); composed of alpha, beta and delta cells

* alpha cells produce & secrete glucagon; promotes gluconeogenesis
* beta cells P&S insulin; promotes glycogenesis
* delta cells P&S somatostatin; inhibitory function

Glucagon

Protein hormone secreted in response to a **low** blood glucose concentration and gastrointestinal hormones

* breaks down larger molecules into smaller molecules to increase blood glucose levels for energy
* stimulates: protein & fat degradation, conversion of glycogen → glucose, glucogenesis
* glucogenesis: pathways through non-carb substances, esp. amino acids, are converted into glucose
* glucagon’s actions are largely antagonistic to those of insulin

Insulin

Protein hormone secreted in response to a **high** blood glucose concentration

* makes body more permeable to glucose
* tries to absorb glucose and store it in muscle, liver and fat cells
* aids in building proteins from amino acids absorbed
* stimulates: uptake of glucose by muscle & adipose cells, storage of glucose → glycogen

Hypoglycemia (low blood glucose levels)

Overproduction of insulin (

Hyperglycemia (high blood glucose levels)

Underproduction of insulin or..

* insensitivity (cells don’t respond to insulin) leads to diabetes mellitus
* characterized by having hyperglycemia/high blood glucose levels
* lead to excretion of glucose in urine & water loss

Diabetes mellitus

Chronic disease that occurs when body can’t produce any/enough insulin, or is unable to properly use insulin it makes

* frequent urination; more urine bc higher concentration of glucose in urine
* increased thirst
* increased appetite; cells are not taking in glucose and not receiving nutrients

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Leads to having more glucose in blood; more needs to be filtered & excreted

* can damage blood vessels by hardening them (artherosclerosis) & damage nerves, nervous tissue (neuropathy)

Types of Diabetes

Type 1: Pancreas unable to produce enough insulin

* born with it

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Type 2: Occurs when cells become insensitive to insulin

* body has constant spikes of blood sugar and insulin that cells get used to it

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Gestational Diabetes: Occurs in some pregnant females bc of insulin resistance

* temporary condition; hormones block action of mother’s insulin

Adrenal Glands

Play a role in regulating blood glucose levels

**Adrenal Cortex:** ACTH secretes steroid hormones (corticosteroids)

* main glucocorticoid = cortisol
* catabolic effects - break down larger molecules to provide energy
* stress hormone
* promotes gluconeogenesis in liver (peaks in morning)
* main mineralcorticoid = aldosterone
* reabsorption of sodium ions
* regulates ion levels in plasma

Adrenal Medulla

Secretes (nor)epinephrine = catecholamine (amino-acid derived)

* **adrenaline** hormones in response to stress
* epinephrine > norepinephrine
* increase metabolic rate & promote gluconeogenesis (creation of glucose)
* increase blood glucose levels