4. Endocrine System Flashcards
Importance of Communication Systems within Organisms
Communication systems (nervous system & endocrine system) are important as they help maintain a constant internal environment (homeostasis) and help an organism survive.
Endocrine Gland
Definition + Examples
An endocrine gland is a ductless gland that secretes hormones directly into bloodstream to be carried towards target cells or organs.
Examples: hypothalamus, pituitary glands, adrenal glands, pancreas, ovaries, testes
Hormone
Definition
A hormone is a chemical substance produced by an endocrine gland, carried by the blood, which alters the activity of one or more specific target organs, and is then destroyed by the liver.
- Hormones are responsible for many processes such as growth and development, metabolism, homeostasis and reproduction
- A single hormone is capable of eliciting different responses in different target cells or tissues
Characteristics of Hormones
Characteristics of hormones:
- Small, soluble molecules
- Effective in low concentrations
- Produced by one organ
- Secreted into and carried to all parts of the body by the blood
- Has an effect at a target site different from the site where it is synthesised
- It is specific. Thus, only organs with target cells that have specific receptors will respond to the hormone
Describe the process of adrenaline secretion and its effects.
When the stimulus, feelings of anger, fear, anxiety, or stress,
is detected by the hypothalamus,
nerve impulses are sent to the effectors, the adrenal glands,
which secrete the hormone adrenaline which is carried by the blood to the target organs.
Adrenaline stimulates:
- Liver and muscles to speed up the breakdown of glycogen into glucose, to increase blood glucose levels.
- Liver to increase its metabolic rate, so more energy is released by tissue respiration.
- Heart to increase rate of heartbeat and cause rise in blood pressure, so oxygen and glucose are carried faster to the muscles.
- Lungs to increase rate and depth of ventilation to take in more oxygen.
- Arterioles in skin to constrict, causing paleness, channeling more blood to muscles.
- The decrease of blood flow to the digestive system, to decrease digestive system activity
- Pupils to dilate, to enhance vision.
- Hair erector muscle to contract, producing ‘goose pimples.’
- The increase in rate of blood coagulation, to prevent excessive blood loss in accidents.
Adrenaline secretion is not a negative feedback mechanism.
Importance of maintaining a constant blood glucose level
- If blood glucose level is too high, the water inside the body cells will leave the cells by osmosis. The cells will become dehydrated, and the normal metabolic activities cannot be carried out properly.
- If the blood glucose level is too low, the brain may not receive sufficient glucose. The person experiences weakness and dizziness because glucose is the main energy source of the body. The body cells cannot carry out their functions properly.
Describe the homeostatic process that occurs when blood glucose concentration is too high.
Insulin:
- When blood glucose concentration increases above the normal conditions (stimulus),
- cells in the islets of Langerhans in the pancreas detect the stimulus, and secrete more insulin into the bloodstream (corrective mechanism).
- Blood transports insulin to body cells, liver, and muscle.
- Insulin promotes the uptake of glucose by almost all body cells especially liver, muscle, and adipose tissue by increasing the permeability of cells.
- Insulin also stimulates the liver and muscle to convert excess glucose into glycogen.
- When blood glucose conentration decreases back to normal, cells in the islets of Langerhans in the pancreas detect this, and sends a negative feedback to the pancreas to
- stop further corrective action. Insulin secretion decreases back to normal.
Describe the homeostatic process that occurs when blood glucose concentration is too low.
Glucagon:
- When blood glucose concentration decreases below the normal conditions (stimulus),
- cells in the islets of Langerhans in the pancreas detect the stimulus, and secrete more glucagon into the bloodstream (corrective mechanism).
- Blood transports glucagon to liver and muscle.
- Glucagon stimulates the liver and muscles to convert glycogen into glucose,
- and increases the release of glucose into the blood from the liver.
- When blood glucose concentration increases back to normal, cells in the islets of Langerhans in the pancreas detect this, and sends a negative feedback to the pancreas to
- stop further corrective action. Glucagon secretion decreases back to normal.
Diabetes Mellitus
What it is + Types
Diabetes mellitus: The condition where the body is unable to maintain blood glucose level within normal range.
There are two major types of diabetes mellitus with very different causes, but each is marked by high blood glucose concentration.
Type 1 diabetes (early-onset diabetes) is caused by a deficiency of insulin:
- Islets of Langerhans in the pancreas cannot produce insulin/sufficient insulin
- Develops at a young age
Type 2 diabetes (late-onset diabetes) is caused by a decreased response (sensitivity) to insulin in target tissues (liver and muscles):
- Develops at an older age
- Linked to unhealthy lifestyle
6 Risk Factors & 2 Prevention Measures of Diabetes Mellitus
Risk Factors:
- Obesity/overweight
- Age
- Family history (diabetes can be inherited)
- Unhealthy blood lipid levels
- Diet high in carbohydrates and fats
- Sedentary lifestyle (little exercise)
Prevention Measures:
- Exercise regularly, maintain healthy bodyweight
- Eat a balanced, healthy diet, low in calories, high in fibre
6 Symptoms of Diabetes Mellitus
Symptoms:
- Persistent high blood glucose (less glucose is able to enter target cells and remains in the blood)
- Glucose found in urine (too much glucose for all to be selectively reabsorbed from filtrate back into the blood stream)
- Frequent urination (more water remains in urine as there is high concentration of glucose)
- Frequently feeling dizzy, fatigue
- Unexpected weight loss (fat is the main substrate for cellular respiration as insufficient glucose absorbed by cells)
- Wounds take longer to heal
Treatment for Type 1 & 2 Diabetes Mellitus
Treatment for:
- Type 1: Insulin injections
- Type 2: Control blood glucose level: diet lower in carbohydrates, exercise regularly. If condition worsens, have to inject insulin/take medication to improve body’s sensitivity to insulin.
There is currently no cure for diabetes
Compare nervous and hormonal coordination
Similarity:
- Both provide pathways of communication within the body to coordinate various activities.
- Both involve the transmission of messages to the effectors.
Difference:
- Nervous coordination sends messages by nerve impulses and neutrotrasmitters while hormonal coordination sends messages by hormones.
- Nervous coordination transmits signals along neurones while hormonal coordination transmit signals in the bloodstream
- Nervous coordination has a rapid rate of transmission while hormonal coordination has a relatively slow rate of transmission
- In nervous coordination, the areas affected are restricted to structures linked to the related neurones. In hormonal coordination, the areas affected are over many parts of the body.
- In nervous coodination, the duration of effect is generally short-lived (e.g. withdrawal reflex). In hormonal coordination, the duration of effect is generally long lasting (e.g. growth).
