BIO 224 Lab 1 - Homeostasis

Homeostasis

The process by which physiological variables are maintained at relatively stable levels within the body of an animal.

Regulation of the internal bodily environment at or near a stable level.

Examples of homeostatic processes

• temperature

• nutrients

• O2

• CO2

• waste

• water

• salt

• pH

External influences on homeostasis

• temperature

• body position relative to gravity

Set-point

The level at which the condition controlled by a homeostatic pathway is to be maintained.

Negative feedback

Returns a variable towards a set point.

Minimizes difference between actual level and the set-point.

Most common in homeostasis.

Positive feedback

Moves variable away from the set point.

Amplifies the difference between actual level and set-point.

Used to quickly increase/decrease a process.

Is eventually shut off by negative feedback.

Vasoconstriction

The narrowing of blood vessels due to the contraction of muscles in their walls.

Reduces blood flow and increased blood pressure.

Vasodilation

The widening of blood vessels caused by the relaxation of smooth muscles in their walls.

Increases blood flow and lessens blood pressure.

Local blood flow

Reflects the volume of blood travelling through vessels supplying blood to tissue.

Can be increased or decreased by altering the diameter of vessels.

Blood pressure

Each pulse of blood ejected from the ventricle exerts a physical force on the walls of the blood vessels.

Hypotension

Occurs when blood pressure drops below the normal range.

Low blood pressure.

Hypertension

High blood pressure.

Blood forcefully pushes against artery walls, increasing the hearts workload and damaging vessels over time.

Plethysmograph

A device the records blood pressure changes in arteries, causing slight changes in the volume of organs.

Used to study the physiology and regulation of arterial blood pressure and local blood flow.

Thermoreceptor

Within the dermis of skin of mammals, specialized sensory receptors that are able to detect changes in skin temperature, sending neuronal signals to the hypothalamus.

Describe the path of blood flow during a complete circuit of blood flow from the left ventricle of the human heart to the fingertips, and then the path back to the left ventricle, naming the major vessels and heart structures encountered along this circuit.

Taylor et al., 2014

Analyze how vasodilation of a blood vessel will influence blood flow and pressure in vessels downstream from the vasodilation (peripherally) compared to the effects of vasodilation on these parameters in vessels upstream from the site of vasodilation (more centrally, closer to the heart).

Compare the effect of gravity on blood flow in the human lower limbs to the effect in the head, and the effect of gravity in a shark with that in a giraffe.

iWorx TA ROAM

Peripheral hardware device that collects physiological information as electrical signals, converts the analog signals into digital signals, and then sends digital information via a USB connection to the computer for display and analysis by the LabScribe program.