SEM 1 - WEEK 1 - HOMEOSTASIS PART 1 + 2

Homeostasis

Ability for the body to maintain a relatively stable internal environment. The body stays in a dynamic steady state, continuously adjusting to changes that occur to adapt to the needs of the body.

Key targets of control

Blood Pressure, pH, Body Temperature, Potassium Sodium Calcium Ion Concentration Levels, Fluid Levels, Blood Glucose Levels

Positive Feedback Loop

Amplifying the initial change

What happens in blood Clot Positive Feedback Loop

Platelets continue attracting other platelets to form clot/scab.

Labour Contractions Positive Feedback Loop

Oxytocin amplifies contractions until childbirth is achieved.

Negative feedback loop

Opposing the initial change

Stimulus

Something that initiates a change

Receptor

Detects Changes

Input

Receptors send signals to brain through an afferent pathway

Afferent Pathway

Information arriving to brain

Output

Brain sends signals to the effector organs through efferent pathway to respond

Response

Change from effector organs that opposes/amplifies the initial change to reach homeostasis.

Effectors

Organ or cell that acts upon the signals sent by the brain

Role of Insulin

Following food intake, blood glucose rises, prompting pancreatic insulin release. Insulin lowers blood glucose by promoting glucose uptake in muscle and liver tissues.

Impact of Iodine Deficiency

Iodine is crucial for T3 and T4 production. These hormones cannot be synthesised without it. Low T3 and T4 levels fail to inhibit TRH. Increased TRH leads to thyroid gland enlargement (goiter) due to iodine deficiency.

Blood Glucose Regulation

After high glucose intake, beta cells in pancreas release insulin, facilitating glucose uptake into the muscles and liver. If blood glucose levels drop, alpha cells release glucagon to prompt glycogen breakdown in liver, raising blood glucose levels.

Type 1 Diabetes

Destruction of beta cells in the pancreas leads to absent insulin release, leaving high blood glucose levels.

Type 2 Diabetes

Body tissues do not effectively respond to insulin and glucose removal is impaired.

Homeostatic Set Point

Physiological value that the normal range fluctuates around

Calcium Homeostatic Mechanism

If calcium levels drop, the parathyroid gland releases PTH, which increases calcium absorption in the intestine, reducing kidney excretion, and releasing calcium from bones. If calcium levels increase, the thyroid releases calcitonin, reducing calcium release from bones, and increasing excretion.