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Systems & Homeostasis Notes
***Disclaimer*** Before we begin, please realize that when talking about living creatures there are always exceptions. When we say “all” or “always” or other absolutes, there may in fact be an exception that you know about. That’s fine. We’re just giving you what is most common!
Keep these objectives in mind as we study the animal kingdom in more depth:
5B. examine specialized cells, including … animal cells such as blood, muscle, and epithelium;
9C. identify and investigate the role of enzymes;
10A. describe the interactions that occur among systems that perform the functions of regulation, nutrient absorption, reproduction, and defense from injury or illness in animals;
10C. analyze the levels of organization in biological systems and relate the levels to each other and to the whole
11A. describe the role of internal feedback mechanisms in the maintenance of homeostasis
11B. investigate and analyze how organisms…respond to external factors
11C. summarize the role of microorganisms in both maintaining and disrupting the health of … organisms …
Introduction to Animal Systems
Animals are organized in an increasing hierarchy of structure (smallest à largest):
cells à tissues à organs à organ systems à organism
Recall that all animals are composed of cells (cell theory! – Schwann), and all but the sponges (Porifera) have tissues. The development of organs begins when those tissues begin to work together in a close structural/functional relationship.
There are 4 major types of tissues:
epithelial connective
nervous muscle
Organs, in turn, make up organ systems. There are 11 primary systems in a mammal such as a human.
The table below lists them, their main components, and primary function.
Organs, in turn, make up organ systems. There are 11 primary systems in a mammal such as a human. The table below lists them, their main components, and primary function.
We think of humans as the most complex organisms. Whether that is true or not, it is true that as body structure becomes more complex, the same functions must still occur
Most importantly, homeostasis must be maintained. Recall that homeostasis is the ability to maintain stable internal conditions, even when the environment is changing. Some examples we are going to include in this unit are energy level (digestive system, thermoregulation), water balance (osmoregulation – excretory system & integumentary system), and oxygenation (circulatory & respiratory systems).
As we move through this material, please note two things: not all members of the Kingdom Animalia have a true “system” for each of these functions, and yet they still occur; no system works in isolation. It is important that you draw on the interconnections among the systems and see how they function together.
Movement & Locomotion
(Skeletal & Muscular Systems)
Locomotion requires energy to overcome both friction and gravity.
Skeletal System
· skeleton – supports & protects the body
· humans have an endoskeleton – hard supporting elements
buried in the soft tissue; made of cartilage and bone
· Bone is made up of cells imbedded in calcium phosphate.
· Bone is alive. The cells are called osteocytes.
· Blood vessels and nerves pass through tunnels in the bone
called Haversian canals.
Human Skeletal System
Function:
· protect and support the body & organs
· bones produce red blood cells, white blood cells, and
platelets in the middle part of the bone called marrow
· bones also store calcium which is important in muscle function
Structures
2 divisions of the vertebrate skeleton
1. axial skeleton
2. appendicular skeleton
Axial Skeleton – the axis of the body
· skull
· vertebral column = cervical, thoracic, lumbar, sacral
· ribs
· sternum
Appendicular Skeleton – the appendages of the body
· pectoral girdle
· forelimbs
· pelvic girdle
· hindlimbs
Skeletal system interconnections:
Other systems that provide protection:
3
Ø Integumentary
Ø Immune
3
Other systems that provide movement:
3
Ø Muscular
Ø Nervous
3
Other systems that use blood cells made by the skeletal system:
Ø Circulatory
Ø Immune
3
Muscular System
- muscles in limbs work in pairs, one flexing & one extending
Human Muscular System
Functions
• move limbs and trunk
• move substances through the body (peristalsis)
• provides support and structure, as well as protection
*recall that muscles have lots of mitochondria since they need lots of energy
Structure
3 Types of Muscle Tissues:
• Skeletal—skeletal muscles; voluntary; striated
• Smooth—vessels and organs; involuntary; spindle-shaped cells
• Cardiac—heart; involuntary; branched striated
Muscular system interconnections:
Other systems that provide movement:
Ø Skeletal
Ø Nervous
Other systems that are made of muscle tissue:
Ø Circulatory (cardiac tissue)
Ø Respiratory (smooth tissue)
Other systems that benefit from the muscles ability to move substances throughout the body:
Ø Digestive
Ø Nervous
Ø Reproductive
Ø Excretory
Ø Endocrine
Digestive System
- Energy comes from the food we eat (heterotrophy). It is broken down into simple molecules that the body can use for cellular respiration (to make ATP). Humans in general are omnivores, though many are herbivores by choice. It is controlled by hormones and the nervous system.
5
- a series of organs involved in breaking down food with the help of enzymes & bacteria and absorbing nutrients for the body’s growth and repair; compartmentalized to prevent self-digestion as well as to allow for varying pH
Functions
• break up large molecules—proteins, carbohydrates, and fats, into small subunits—amino acids, glucose, glycerol, and fatty acids for energy
· uses ENZYMES to break the large molecules of the food we eat into the simple molecules needed
• helps body maintain homeostasis
The basic process of obtaining energy and nutrients from food involves 4 steps:
5
1. ingestion – eating
2. digestion – processing
mechanical – chewing (increase surface area)
chemical – involves enzymes (hydrolysis); breaks large molecules down into absorbable nutrients
3. absorption – of nutrients
4. elimination – of wastes
5
Structures
mouth – digestion starts here.
salivary glands – secrete enzymes to help with digestion.
esophagus
– tube that goes from the mouth to the stomach
– pushes food down the tube through peristalsis
stomach
– mechanical digestion
– digests proteins with pepsin or HCl
small intestine
– completes digestion; trypsin, lipases, bile
– absorbs nutrients that then enter the blood stream (circulatory)
large intestine
– reabsorbs water
– passageway for waste
gall bladder* – stores bile
pancreas*
– secretes enzymes into small intestine
– produces insulin (endocrine hormone for sugar regulation)
liver*
– secretes bile
– purifies blood
– removes toxins
– stores glucose as glycogen
Digestive system interconnections
Nutrients are absorbed from the small intestine and carried throughout the body by this system:
Ø Circulatory
This system controls peristalsis:
Ø Muscular
This system gets rid of the waste produced by the digestive system:
Ø Excretory (Urinary)
These systems are also closely linked:
5
Ø Nervous
Ø Endocrine
Ø Skeletal
Circulatory (Cardiovascular) System
Functions
· transport and exchange of many substances, including nutrients, wastes, hormones, gases, and heat through a series of organs and vessels
· involved in maintaining homeostasis
Structure
· composed of blood, blood vessels, heart
· 2 parts:
1. cardiovascular (heart-vessel) system
2. lymphatic system (often listed separately)
- humans have closed circulatory systems, meaning that the blood is
confined to vessels and remains separate from the interstitial fluid
- exchange of materials at the cells occurs by diffusion with the capillaries -
- the heart is located ventrally
The human circulatory system is a double circuit
with 2 atria & 2 ventricles
pulmonary loop (circuit) – from the right ventricle to
the lungs and back to the left atrium
systemic loop – from the left ventricle to the body
and back to the right atrium
Blood – composed of a variety of cells in a fluid matrix
plasma – fluid portion of the blood; important in maintaining homeostasis
platelets – proteins involved in blood clotting
red blood cells – contain hemoglobin for carrying oxygen; made in the bone marrow
white blood cells – cells involved primarily in the immune response
- B lymphocytes – white blood cells that produce antibodies; made and mature in the bone marrow
- phagocytes – type of white blood cell that engulf particles including viruses and bacteria
Structures
pericardium: surrounds & protects the heart
atria: 2 top chambers of the heart
– receives the blood
– left and right atrium
ventricles: 2 bottom chambers of the heart
– pump blood
– left and right ventricle
septum: separates the right & left sides of the heart
coronary blood vessels: feed the muscle of the heart with oxygen
aorta: carries oxygenated blood to body
superior (anterior) vena cava: carries blood from head to heart (deoxygenated)
inferior (posterior) vena cava: carries blood from bottom to heart (deoxygenated)
arteries: carry blood away from the heart (oxygenated, except in pulmonary arteries)
veins: carry blood to the heart (deoxygenated, except in pulmonary veins)
Blood Flow Through the Heart
Circulatory system interconnections
The other system that involves exchanging oxygen and carbon dioxide into and out of the blood:
Ø Respiratory (at the lungs)
The other system that involves lymph nodes to fight infection:
Ø Immune
The system that makes blood cells:
Ø Skeletal
This system composes the cardiac tissue in the heart:
Ø Muscular
Nutrients absorbed in this system are circulated throughout the body:
Ø Digestive (at the small intestine)
Works with this system transferring heat toward or away from the skin’s surface to release or retain heat (vasodilation & vasoconstriction)
Ø Integumentary
Nervous and endocrine systems are also connected closely.
Respiratory System
Function
· moves air into and out of the lungs
· controls gas exchange between blood and lungs
· helps to maintain homeostasis
Why do you need to breathe?
All the cells in your body require oxygen. Without it, they couldn't turn food (glucose) into energy (ATP) through cellular respiration. You get oxygen from breathing in air, which your red blood cells carry to all parts of the body. You breathe out the carbon dioxide.
Gas Exchange - Gas exchange occurs at the cellular level by diffusion in all organisms
o lungs – do not branch through the body in vertebrates, therefore a close relationship with the circulatory system is required to exchange gases
Respiratory System Terminology
pharynx: back of throat, beginning of trachea
epiglottis: covers the glottis as an organism swallows
larynx: voice box, vibrations produce noise
glottis: opening to the trachea (windpipe)
trachea: windpipe carries air to lungs
bronchi: two branches (left & right bronchus) at lower end of trachea
bronchioles: smaller branches located in lungs
diaphragm: muscle that contracts to pull air into lungs
lungs: right lung- three lobes, left lung- two lobes, exchange gases
– each minute you breathe in about 13 pints (26 cups) of air
alveoli: air filled sacs where oxygen and carbon dioxide are exchanged (where gas exchange occurs between the respiratory system and the capillaries of the circulatory system)
Trace a breath through the Respiratory System
external nostrils/mouthàpharynxàlarynxàtracheaàbronchiàbrochiolesàalveoli
Many of the cells of the respiratory tract are lined with cilia. These cilia function to remove debris out of the respiratory tract like an escalator moving up. Cigarette smoke damages these ciliated cells which can greatly affect the debris removal.
Respiratory system interconnections
Other systems that involve exchanging oxygen and carbon dioxide into and out of the blood:
Ø Circulatory
The system that helps compose the lungs (made of smooth tissue):
Ø Muscular
Other systems involved:
Ø Nervous
– the central nervous system controls breathing. The breathing response is triggered by the level of carbon dioxide (too high = breathe), NOT the level of oxygen.
Ø Endocrine
Regulation – Maintaining Homeostasis
(Integumentary & Excretory/Urinary systems—
thermoregulartion, osmoregulation, waste disposal)
thermoregulation – involves heating and cooling of an organism to maintain a body temperature within a (generally) narrow range
- humans are endotherms, meaning that they have a high metabolic rate that generates enough heat to keep the body warmer than the environment and can cool themselves through convection and evaporation
- conduction – direct transfer of heat; contact between organism and object in its environment
o animal à cold water
o warm rock à animal
- convection – involves the transfer of heat by movement of fluids past the surface of the organism
o breeze passing over skin
o blood carrying heat from core to extremeties
- radiation – involves the emission of electromagnetic waves (usually in the infrared range – IR – which we call “heat”)
o sun à animal
o animal à environment
- evaporation – removal of heat from the surface of a liquid that is losing some of its molecules as gas
Integumentary System
- important in thermoregulation
- layer of adipose tissue (fat) below the skin acts as an insulator (and cushion); protection
- skin often contains glands such as sweat glands that increases heat transfer to the environment by evaporation
- sweat is a body fluid that helps remove certain wastes, similar to urine
Functions
· protection against injury, infection and fluid loss; adds insulation
· helps maintain homeostasis by regulating body temperature through thermoregulation
Structures
skin: the largest organ of the body; it is made of two layers the epidermis and the dermis
– epidermis: outer layer of skin
– dermis: inner layer of skin
sweat glands: sweat is a body fluid that helps remove certain wastes, similar to urine
sebaceous (oil) glands
Integumentary system interconnections:
Other systems that provide protection:
Ø Immune
Ø Skeletal
Other systems that help maintain homeostasis:
Ø Circulatory
Ø Nervous
Ø Endocrine
Excretory (Urinary) System
- central to homeostasis
- dispose of metabolic waste (nitrogenous)
- control body fluid by adjusting the rates of loss of particular solutes
- basic process
o filtration
o reabsorption
o secretion
o excretion
- nephron – microscopic functional unit of vertebrate kidney
o unfiltered blood enters the nephron at the ball of capillaries called the glomerulus
o the ball of capillaries is surrounded by a cup called the Bowman’s capsule that begins filtration
o the urine produced at the end should be composed of water, urea, and a little salt
Human Excretory (Urinary) System
Functions
• responsible for filtering metabolic wastes from the bloodstream and controls the ionic composition of the blood
• excretes wastes outside of body
• involved in maintaining homeostasis
· does NOT produce feces – that is a byproduct of digestion from the digestive system
Structures
kidney: filters waste from blood, produces urine (water + urea + some ions)
ureter: carries urine from kidney to bladder
urinary bladder: stores urine
urethra: tube through which urine leaves from the bladder to the outside of the body
renal arteries & veins: take oxygenated blood to the kidneys & deoxygenated blood away from the kidneys, respectively
nephron: tube-like structure in the kidneys that filters wastes from the blood and retains useful molecules and water IN the blood
Water Balance and Waste Disposal
osmoregulation – management of the body’s water content & solute composition; goal is to maintain homeostasis in the content of the cytoplasm & interstitial fluids/blood