Transcript circ and homeo

The Circulatory System and
Homeostasis
• The Circulatory System , which contributes to
homeostasis by serving as the body's transport system
consists of the heart, blood vessels, and blood
• The walls of the heart are composed primarily of cardiac
muscle, which is self excitable; it initiates its own
contractions.
• The heart serves as a double pump to continually
circulate blood between the lungs where Oxygen is
picked up and Carbon Dioxide is removed, and other
body tissues, which use oxygen to support their energy
generating chemical reactions, producing carbon dioxide
in the process.
• Components of the circulatory system
include
• blood: a connective tissue of liquid plasma
and cells
• heart: a muscular pump to move the blood
• blood vessels: arteries, capillaries and
veins that deliver blood to all tissues
• The circulatory system is sometimes referred to
as the cardiovascular system or blood vascular
system.
• This system consists of a muscular pump, the
heart (cardio), and a network of blood vessels arteries, veins and capillaries (vascular).
• The transport medium in this system is blood
which is pumped throughout an organism
through a closed circuit of blood vessels.
• This closed system keeps blood contained as it
passes through various “circulations” of the
body.
• The capillaries, which are tiny blood vessels
connecting arteries and veins, are in contact with
extra cellular fluid surrounding each individual
cell.
• In these microscopic vessels, blood performs its
ultimate homeostatic function. Nutrients and
other essential materials pass from capillary
blood into fluids surrounding the cells as waste
products are removed.
• Therefore, homeostasis within extra cellular fluid
and the cells is facilitated
• Numerous control mechanisms ensure a constant
internal environment surrounding each body cell
regardless of differing demands for nutrients or
production of waste products.
• All sorts of factors affect the suitability of our body fluids
to sustain life; these include properties like temperature,
salinity, acidity (carbon dioxide), and the concentrations
of nutrients and wastes (urea, glucose, various ion,
oxygen).
• Physiological mechanisms, in conjunction with the
circulatory system, ensure that the above properties are
maintained at ideal levels.
• These physiological mechanisms are controlled by
various organs in the body.
Thermal Regulation
The skeletal muscles can shiver to produce
heat if the body temperature is too low.
• Non-shivering, thermogenesis, involves
the decomposition of fat to produce heat.
• Sweating cools the body by taking
advantage of the cooling effect of
evaporation.
Temperature Regulation in
Homeotherms
• Animals capable of temperature regulation within a given
range are deemed homeotherms (alternatively
homiotherms or homotherms). They have the ability to
regulate temperature via negative feedback control
which is outlined below
• Temperature fluctuations in the body are recognized by
thermoreceptors in the hypothalamus. Other
thermoreceptors which detect temperature fluctuations in
the external environment are present in the skin.
• When a temperature change is detected the information
is relayed from the skin to the hypothalamus which in
turn transmits messages causing corrective mechanisms
to return body temperatures to a stable state.
Corrective Mechanisms in
Temperature Control
• Increased perspiration is a corrective mechanism which
can reduce elevated body temperatures through the
cooling action of evaporation.
• Vasodilation is a corrective response where the blood
vessels close to the skin surface become more dilated in
response to increased core body temperatures.
• The larger surface area of dilated vessels allows more
heat to escape from overheated blood to the external
environment.
• Vasoconstriction is the opposite of this and occurs when
temperatures in an organism drop. The blood vessels
become constricted so that minimal heat loss occurs.
• The hairs on your body also play an important role in
temperature regulation. A corrective response to
decreased temperatures can occur where the hairs
'stand on end', and trap a layer of air between the hair
and the skin.
• This insulation of warmer air next to the skin reduces
heat loss. Hair flattened to the skin in response to
increased temperatures means there is a minimal layer
of insulation, which would increase heat loss.
• Other corrective mechanisms are involved, such as a
drop in metabolic rate and shivering when temperatures
drop.