D3.3 Homeostasis*

homeostasis

The ability of body to maintain a constant internal environment

factors that need to be control

Blood glucose

Blood pH (7.4)

Body temperature (37.0°C)

Blood osmotic concentration

what involves homeostasis

negative feedback mechanism

negative feedback mechanism fedinition

The action of the response is opposite to the action of the stimulation.

negative feed back is a way of

monitoring levels of variables and correcting changes in levels around a set point.

stimulus detected will initiate what

nervous and/or endocrine systems to respond to return variable to set point

endocrine gland

Endocrine glands secrete their product (hormones) directly into the bloodstream, rather than through a duct (e.g. exocrine gland)

• Major endocrine glands include the: pancreas, adrenal gland, thyroid gland, pineal gland, and the gonads (ovaries and testes)

• The hypothalamus and pituitary gland are neuroendocrine glands and function to link the nervous and endocrine systems

• Some organs may also secrete hormones despite not being endocrine glands (e.g. adipose tissue secretes leptin)

endocrine system

consist of glands that release hormones that are transported via blood into the target organs.

insulin secretion site target site effect

Beta (β) cells of the pancreas

Liver and body cells

Decrease blood glucose

glucagon secretion site target site effect

Alpha (α) cells of the pancreas

Liver

Increase blood glucose

thyroxin secretion site target site effect

thyroid gland

Body cells

Regulate the metabolic rate and help control body temperature

leptin secretion site target site effect

cells in adipose tissue

Hypothalamus

Inhibit appetite

concentration of leptin in the blood is controlled by food intake and the amount of adipose tissue in the body.

If the amount of adipose tissue in an individual increase, then their concentrations of leptin also increases, leading to long-term suppression of appetite and reduced food intake.

melatonin secretion site target site effect

pineal gland

Hypothalamus

Control circadian rhythms

blood glucose regulation 

Blood glucose concentration is carefully monitored by negative feedback mechanisms

• Cellular respiration is constantly lowering blood glucose levels.

• Receptors in the pancreas sense when the blood glucose level is too low

• alpha cells in the pancreas secrete glucagon into the bloodstream

• Glucagon stimulates the liver to breakdown stored glycogen into glucose which is released into the

bloodstream.

• Blood glucose levels rise back to their normal limits.

• If the glucose levels get too high, receptors sense the increased glucose levels causing the pancreas to secrete

insulin by the beta cells in the pancreas.

• Insulin stimulates the absorption of glucose from blood rom the blood into skeletal muscles and fat tissue, and,

thus allowing the liver to convert glucose into glycogen (animal carbohydrate storage molecule)

• Glucose levels decrease back to the normal range.

consequence of blood sugar glucose not controlled

diabetes

diabetes

A disease where the patient has a high level of blood glucose.

results in symptoms including glucose present in urine, thirsty, fatigue, prone to infection, could results blindness and limbs amputation

Type I diabetes

Other names

Cause

Risk factors

Prevention

Treatment

Insulin-dependent

Early onset diabetes

Autoimmune disease that destroys beta-cells = insufficient production of insulin

Family history

n/a

Insulin injections

Dietary modifications

Regular exercise

Type II diabetes

Insulin-independent

Late onset diabetes

Insulin resistance

Family history, overweight/obesity, sedentary lifestyle, diet high in process/sugar/unhealthy fat, age

Changes to lifestyle to prevent or delay onset

Moderate weight loss

Healthy diet

Regular physical activity

how birds and mammels regulate body temperature

physiological and behavioral mechanism

Thermoregulation is coordinated by the

nervous system.

Temperature changes are detected by

thermoreceptors.

two physiological response yo temperature

skin

hormone 

Response to heat

Detected by hypothalamus

Thyroid gland secretes less thyroxin

Effects:

1. Vasodilation

Blood arterioles dilate, more blood pass near skin surface to radiate off heat

2. Sweating - sweat droplets will absorb body heat to evaporate

3. Hair erectile muscles relax, hair lies flat 

4. Reduced metabolic rate

5. Reduced cell respiration in brown adipose tissue (BAT)

 

Response to cold

Detected by hypothalamus

Thyroid gland secretes more thyroxin

Effects:

1. Vasoconstriction

Blood arterioles constrict, blood pass beneath the fat layer to insulate heat

2. Shivering - this causes muscle contraction; cells respire more to produce heat.

3. Hair erectile muscles contract, hair stays upright

4. Increased metabolic rate

5. Increased cell respiration in brown

adipose tissue (BAT)

brown adipose tissue

heat is

byproduct in cellular repisration

mitochondira in brown adipose tissue can

uncouple cellular respiration from ATP synthesis

so glucose can be broken down for sole purpose of heat generation 

Hypothalamus

receives information from nerves throughout the body and other parts of the brain and initiates endocrine responses.

what does hypothalamus secretes

inhibiting hormones — called releasing factors) into a portal system which target the anterior lobe of the pituitary gland.

secretes oxytocin and antidiuretic hormone (ADH) directly into the blood via neurosecretory cells that extend into the posterior pituitary lobe

negative feedback includes

Blood sugar control

body temperature

appetite control

circadian rythym

positive feedback includes

ovulation

childbirth

apetite control

pineal gland

hormone target organ function

melatonin

many

biological clock

pituitary gland

hormone target organ function

FSH/LH - ovaries - menstural cycle

ADH - kidneys - osmoregulation/ blood pressure

Growth Hormone - many - growth and division

Oxytocin - Uterus - Birth Contractions

Prolactin - Breast tissue - milk production

Thyroid gland

hormone target organ function

thyroxin - liver - metabolic rate

Adrenal Glands

hormone target organ function

adrenaline - many - fight or flight (increase blood rate/tense muscles, etc)

cortisol - any - anti stress

pancreas

hormone target organ function

insuline/glucagon - liver - blood sugar levels

ovaries

hormone target organ function

estrogen/progestorone - uterus - mentrual cycle

testes

hormone target organ function

testosterone - many - male characteristics

leptin

hormone target organ function

adipose cell

hypothalamus

control apetite