phys day 1 : body systems, homeostasis, feedback systems

anatomy and physiology

2 branches of science that deal with body parts & functions

anatomy

science of body structures & relationships

first studies done by dissection

imaging techniques

physiology

science of body functions

structure and function of body

structure of a part of the body allows performance of certain functions

ex: bone of skull provides protection for the brain, thin air sacs of lungs permit movement of oxygen

6 main levels of structural organization

chemical, cellular, tissue, organ, system, organismal

chemical level

atoms: carbon, hydrogen, oxygen, nitrogen, phosphorus —> molecule DNA

cellular level

ex: smooth muscle cell

tissue level

ex: smooth muscle tissue

organ level

ex: stomach

system level

ex: digestive system

organismal system

ex: human

internal environment

the environment in which the cells of the body actually live

types of body fluids

intracellular (ICF), extracellular (ECF)

types of ECFs

interstitial fluid, plasma

interstitial fluid (IF)

fluid outside the cells

plasma

fluid portion of blood

body’s internal environment

80% made of water

body cells in contact with water environment

internal environments are the fluid around the cells

materials that exchange between blood and tissue

nutrients, gases, wastes

process of material exchange

Blood —> External Fluid —> Tissue Cells

1. blood travels through tiny blood vessels (capillaries)

2. the plasma (liquid part of the blood) carries nutrients, oxygen, & other materials

3. the fluid surrounding the tissue cells is called external fluid

4. materials pass through this fluid to get between the blood & cells

5. nutrients & oxygen move from the blood —> external fluid —> tissue cells

6. cells use these materials to function

7. tissue cells produce waste (ex: CO2)

8. waste moves from the tissue cells —> external fluid —> to blood

9. blood carries the waste away so the body can get rid of it

homeostasis

maintenance of a stable, relatively constant, internal environment (an internal equilibrium)

controlled conditions in an internal environment

temperature, pH, concentration of glucose, ions, gases

homeostatic range

pre-set limits of these controlled variables

dynamic condition

always responding to environmental conditions

every cell/organ/system in the body contributes to homeostasis

homeostasis as a dynamic condition (external & internal)

external: blood temperature

• too hot: sweat

• too cold: shiver

internal: concentration of blood glucose

too high: release insulin

too low: release glucagon

3 components of homeostatic control feedback system

receptor: sensory neuron

control center: brain

effector: muscle gland

receptor

body structure that monitors changes in a controlled condition, sends an input to the control center (brain)

types of receptors

thermoreceptors (in the skin): for temperature

baroreceptors (in blood vessel wall): for pressure

chemoreceptors (in blood vessel wall): for different levels of atoms/chemicals

osmoreceptors (in hypothalamus): detects changes in osmosis/water diffusion

control center

brain

brain function in feedback systems

sets range of values that need to be maintained (depends on DNA)

evaluates input received from receptors & generates output command

output command is mediated by nerve impulses and/or hormones

effector

muscle gland

muscle gland role in feedback systems

receives output from control center

produces a response/effect that changes the controlled condition

negative feedback systems

opposes a change in the original stimulus

returns to homeostatic conditions

body typically operates on negative feedback system

ex: blood sugar regulation, blood pressure regulation

positive feedback loop

amplifies original stimulus

ex: cut, needs to start sending signals for blood clotting, increases blood clotting to stop bleeding

ex: childbirth, contractions → more oxytocin → stronger contractions → more oxytocin (oxytocin causes uterus to contract)

baroreceptor reflex

regulation of blood pressure, negative feedback loop

blood pressure

force exerted by blood as it presses against the walls of the blood vessels

receptors in regulation of blood pressure

baroreceptors (pressure sensitive)

control center in regulation of blood pressure

cardiovascular (CV) system of the brain

effectors in regulation of blood pressure

heart & blood vessels

baroreceptor reflex process in regulation of blood pressure

stimulus causes a decrease in BP

baroreceptors - detect drop in BP

sends a message (neurons) to the control center (CV center of brain)

sends a message (neurons) to the effectors

heart = increases force & rate of heart contraction

blood vessels = vasoconstriction (get smaller, reduce blood flow, and increase pressure)

result: BP increased to homeostatic levels

• process also works to decrease BP