Homeostasis and Body Organization What is homeostasis? “constancy” or “steady state” maintained within the organisms’ bodies. Whereas the environment can.

Homeostasis and Body Organization

What is homeostasis?

“constancy” or “steady state” maintained within the organisms’ bodies.

Whereas the environment can be highly variable, organisms incorporateinternal control mechanisms to oppose the forces that would change theirinternal physiological equilibrium.

The organisms’ internal state can be described as being in dynamic equilibrium, because the body needs to be constantly adjusting to theChanges.

This regulation occurs in two basic ways:

Negative feedback – most important means of maintaining homeostasis,negative feedback creates a counter-effect to the outside environmental change

Positive feedback – a mechanism whereby the effects from the originalenvironmental changes are intensified.

Homeostasis and Body OrganizationPositive and Negative Feedbacks

Homeostasis and Body OrganizationPositive and Negative Feedbacks

Homeostasis and Body OrganizationPositive and Negative Feedbacks

It should be noted though that there are many systems involved in organisms’ Body, and that they all need to interact with each other to maintain homeostasis.

Different systems working independently could end up working against each other,but since the body has systems that move substances and signals from one part of the body to the next, all the different body parts remain “connected”.

This coordination is achieved via chemical (hormones) and/or electrical(nervous) communication between tissues that elicits appropriate responses.

Body Organization

The body is organized at different levels:

Tissues: includes structurally similar cells that act together to perform a particular function. (e.g. muscular, nervous, epithelial, etc.)

Organs: the next higher level of organization, tissues come together to form organs. (e.g. stomach, kidneys, liver, etc.)

Organ systems: the different organs that work together towards a particularfunction come together to create organ systems. (e.g. digestive systemwhich is composed of the stomach, small intestine, large intestine, andother organs.

You are responsible to read pages 526 – 533. Learn the basic structure and function of the major vertebrate organ systems outlined in table 26-2 on page 532.

Circulation

Why do we even need a circulatory system?

Simple diffusion is too slow to serve the needs of “larger” organisms.

Primary Functions?

1. Gas exchange

2. Distribution of nutrients

3. Waste removal

Other functions in vertebrates (and some invertebrates)?

4. Distribution of hormones

5. Regulation of body temperature

6. Protection of body from bacteria and viruses – circulation of antibodies and white blood cells.

Circulation

All circulatory systems have 3 major components:

1. A fluid “blood” that serves as a medium of transport

2. A system of channels (blood vessels) that transport the blood throughout the body.

3. A “heart” that acts as a pump and keeps the blood circulating.

Animals have one of two types of circulatory systems:1. Open2. Closed

Circulation

Note: Vertebrates (including humans) have a closed circulatory system

Circulation – the vertebrate heart

There is an increased level of complexity associated with vertebrate evolution. Thisincreased complexity has created more efficient circulatory systems that have allowedfor greater diversity of form and function in different environments.

This is not of coursethe only solution,squids for examplehave three hearts...

Circulation – the four chambered heart

The mammalian and avian hearts consist of two pumps in one.

One pump is responsible for pulmonary circulation – consisting of the rightatrium and ventricles, this pump is responsible for sending blood to the lungs.

The other pump is responsible for systemic circulation – consisting of the leftatrium and ventricles, this pump is responsible for sending oxygenatedblood to the body.

Circulation – the four chambered heart

Electric impulses coordinatethe sequence of contractions

Valves maintain directionality ofblood flow. The valves are “one-way”

Circulation – the four chambered heart

The atria and ventricles of the heart need to pump in a coordinated fashion. The alternating contraction and relaxation of the heart chambers is calledthe cardiac cycle.

The nervous system and hormones influence heart rate...

The contraction of the ventricles is called the systole and the relaxation is called the diastole

Circulation – the four chambered heartMeasuring blood pressure

Circulation – the four chambered heartElectrocardiograms

Circulation – structure and function of blood vessels

Arteries and Arterioles – Thick-walled vessels that carry blood away from heart

arterioles can control the distribution of bloodby muscular contractions – they are influencedby nerves, hormones, and chemicals produced innearby tissues.

Capillaries – Microscopic vessels that allow blood and body to exchange gas, nutrients, and waste

Veins and Venules – Carry blood back to the heart

Valves direct flow of blood in veins

Circulation – structure and function of blood vessels

Change in blood velocity as a functionof circulatory cross section allows for more efficient transport as well as gas, nutrient, and waste exchange...

Circulation – blood

Blood components:

Plasma – the “fluid” part of the blood, it is composed of 90% water alongwith proteins, hormones, nutrients, gases, salts, and wastes...

Specialized cells – these are cells suspended in the plasma and include red bloodcells, white blood cells, and platelets.

Red blood cells are primarily involved in transport of oxygen

White blood cells are primarily involved in the immune system

Platelets are primarily involved in blood clotting

Circulation – blood

Red blood cells contain a large,iron-containing protein calledhemoglobin.

Each hemoglobin can bind to fouroxygen molecules and is involvedin picking up oxygen in the lungsand transferring it to the body...

Circulation – the lymphatic system

A network of lymph capilaries and large vesselsthat empty into the circulatory system. Functioninclude:

1. Removal of excess fluids and dissolvedsubstances that leak from capillaries.

2. Transport of fats from the small intestineto the blood stream.

3. Defense of the body by exposing bacteriaand viruses to white blood cells.