Download 1 C.P. BIOLOGY Unit 9 – Physiology: Maintaining Homeostasis

C.P. BIOLOGY
Unit 9 – Physiology: Maintaining Homeostasis
Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes
LS1.A and LS.1D: Structure, Function and Information Processing
OBJECTIVE 1: EXPLAIN THE IMPORTANCE OF HOMEOSTASIS IN THE HUMAN BODY
A. Organisms are complex, organized, and built on a hierarchical structure, with each level providing the
foundation for the next: cell, tissue, organ, organ system, organisms. Homeostasis is maintained
within the body by a complex series of organs and organ systems working together.
1. When equilibrium within the body is maintained, homeostasis is said to occur. The human body
maintains a steady internal environment for the proper functioning of the body.
B. Maintaining a constant internal environment requires the body to make many adjustments.
1. Adjustments within the body are referred to as regulation of homeostasis.
a. Homeostatic regulation is comprised of three parts: a receptor, a control center and an
effector. The receptor functions by receiving information about any changes that are occurring
in the environment while the control center processes that information and the effector
executes the commands of the control center by making changes in response.
C. Feedback mechanisms maintain a living system’s internal condition within certain limits and mediate
behaviors, allowing it to remain alive and functioning even as external conditions change within some
range. Outside the range, the organism cannot survive. Feedback mechanisms can encourage
(through positive feedback) or discourage (through negative feedback) what is going on in the living
systems.
OBJECTIVE 2: EXPLAIN THE IMPORTANCE OF AN ORGANISM’S NERVOUS SYTEM
A. An organism’s ability to sense and respond to its environment enhances its chance of surviving and
reproducing.
B. Animals have external and internal sensory receptors that detect different kinds of information, and
they use internal mechanisms for processing and storing it.
1. Each receptor can respond to different inputs (light, mechanical, chemical), some receptors
respond by transmitting impulses that travel along nerve cells.
C. In complex organisms, most such inputs travel to the brain, which is divided into several distinct
regions and circuits that serve primary roles, in particular:
1. visual and auditory perception
2. interpretation of perceptual information
3. guidance of motor movement
4. decision making
D. Some of the brain’s circuits give rise to emotions and store memories.
E. Brain function also involves multiple interactions between the various regions to form an integrated
sense of self and the surrounding world.
OBJECTIVE 3: DESCRIBE THE BASIC STRUCTURE AND FUNCTION OF A NEURON
A. The basic unit of structure and function of the nervous system is the neuron, or nerve cell, which
conduct impulses throughout the nervous system. Allows organism to respond to a changing
environment both internally and externally in order to maintain homeostasis.
1. consists of three regions: (see diagram and page 973)
a. cell body: contains the nucleus of the neuron
b. dendrites: branch-like extensions of the neuron that receive impulses and carry them toward
the cell body.
c. axon: a single extension of the neuron that carries impulses away from the cell body and
towards other neurons, muscles, or glands.
OBJECTIVE 4: DESCRIBE THE FUNCTIONS OF THE THREE CATEGORIES OF NEURONS AND
SUMMARIZE THE RELAY OF AN IMPULSE
A. Neurons are categorized into three groups based on their functions
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B. Sensory neurons: carry impulses from the body to the spinal cord and brain
C. Interneurons: found within the brain and spinal cord; process incoming impulses and pass response
impulses on to the motor neurons
D. Motor neurons: carry the response impulses away from the brain and spinal cord to a muscle or a
gland.
E. The nervous system sorts and interprets incoming information before directing a response. It mediates
communication between different parts of the body and the body’s interaction with the environment.
1. Receptors are sense organs and are sensitive to changes in the environment, triggered by a
stimulus; heat, cold, light, sound, pressure, chemicals, etc.
2. Receptorsà sensory neuronsà interneuronsà motor neuronsà effectors
3. Effectors are of two types: muscles and glands. Glands when stimulated will either increase or
decrease activity. Muscles will contract.
F. The body automatically responds to an external stimulus through a reflex arc.
1. A simple reflex arc involves one sensory neuron, one interneuron in the spinal cord, and one motor
neuron.
OBJECTIVE 5: DESCRIBE A NEURON AT REST
A. A neuron at rest is not transmitting any impulses.
B. The outside of the neuron has a positive charge and the inside has a negative charge.
+
+
1. A neuron’s plasma membrane is more permeable to potassium (K ) than to sodium (Na ), so more
sodium ions exist on the outside of the cell.
2. The neuron membrane has an active transport system called the sodium/potassium pump. Using
ATP, the system pumps three sodium ions out of the cell for every two potassium ions it pumps in.
3. The action of the pump increases the concentration of positive charges on the outside of the
membrane.
C. Under these conditions, the cell is polarized and has the potential to transmit impulses.
OBJECTIVE 6: DESCRIBE THE TRANSMISSION OF AN IMPULSE AND THE IMPORTANCE OF THE
MYELIN SHEATH AND NEUROTRANSMITTERS
A. When a stimulus excites a neuron, gated sodium channels open up in the plasma membrane and
sodium ions rush into the cell.(see page 975)
B. The inside of the cell now becomes more positively charged than the outside. This change in charge
is called depolarization and moves like a wave down the length of the axon.
+ +
1. As the wave passes the gated sodium channels and the Na /K pump return the neuron to its
resting state.
C. An impulse can travel down the length of an axon only when the stimulation is strong enough.
1. If the threshold level, the level at which depolarization occurs, is not reached then the impulse
quickly dies out.
2. All impulses along a neuron are the same size, but not all neurons have the same threshold to
trigger that impulse
3. A stronger stimulus will trigger more neurons (and trigger them at a faster rate). This tells the
brain/spinal cord the strength of that impulse.
D. Most axons are covered by the myelin sheath that insulates the axon and prevents the movement of
ions across the plasma membrane.
1. Ions move quickly down the axon until they reach a gap in the sheath where, at that point, the ions
pass through the membrane and depolarization occurs.
2. As a result, the impulse jumps from gap to gap, greatly increasing the rate at which it travels.
a. unmyelinated: 2m/second
b. myelinated: 100m/second
3. In the brain and spinal cord masses of myelinated axons make up what is called “white matter”.
E. Neurons lie end to end, axons to dendrites, but don’t actually touch. The junction between them is
called a synapse. (see diagram and page 976)
1. Impulses traveling to and from the brain move across the synaptic space.
a. As an impulse reaches the end of an axon, calcium channels open, allowing calcium to enter the
end of the axon.
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b. Calcium causes vesicles in the axon to fuse with the plasma membrane and release
neurotransmitters via exocytosis.
c. These neurotransmitters diffuse across the space to the dendrite of the next neuron and signal
receptor sites to open the ion channels.
d. These open channels change the polarity in the neuron initiating a new impulse.
e. Enzymes break down neurotransmitters shortly after transmission, preventing the continual
firing of impulses.
OBJECTIVE 7: COMPARE THE STRUCTURE AND FUNCTION OF THE HUMAN CENTRAL AND
PERIPHERAL NERVOUS SYSTEM
Human Nervous System
Central Nervous System
1.
2.
3.
Brain
Interprets and
stores information
Controls and
coordinates
Learning
1.
2.
Peripheral Nervous System
Spinal Cord
Carries info. to
and from the
brain
Reflex
Motor Neurons
Information carried
away from the brain
to effectors
Autonomic
1. involuntary
2. stimulates glands and
other muscles (temp.,
blood pressure)
Parasympathetic
Stimulates activity of normal
internal body functions
(digest food) and inhibits
alarm responses
Sensory Neurons
Information to the
brain from receptors
Somatic
1. voluntary
2. relays commands to
skeletal muscles (lift arm)
3. reflexes
Sympathetic
Stimulates alarm
responses (faster heart
rate) and inhibits normal
functions
OBJECTIVE 8: DESCRIBE THE FOLLOWING SENSE ORGANS: TASTE BUDS, NOSE, EYE, EAR,
AND SKIN
A. Taste and smell are senses that respond to chemical stimulation.
1. Taste: chemicals dissolved in saliva contact sensory receptors on your tongue called taste buds.
Signals from the taste buds travel to the cerebrum where they are interpreted…then you taste!
Taste buds are sensitive to sweet, sour, salt, and bitter
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2. Nose: Chemical molecules stimulate hairlike nerve endings located in the upper portion of your
nose that initiate impulses in the olfactory nerve, which is connected to the brain. In the brain, this
signal is interpreted as a particular odor.
3. The senses of taste and smell are closely linked.
B. Sight is a sense that responds to light stimulation
1. Eye structure: see diagram and terms
2. Vision:
a. Light passes through the lens and forms an image on the retina containing rods and cones.
b. An impulse is carried to the brain by the optic nerve. The brain interprets the images.
C. Hearing and balance are senses that respond to mechanical stimulation
1. Ear structure: see diagram and terms
2. Hearing:
a. sound waves vibrate the tympanic membrane à bones of the middle ear à fluid in the
cochlea à tiny hairs which stimulate the auditory nerve to send an impulse to the brain
3. Gravity:
a. at the base of the semicircular canals are gravity receptors called statocysts, a gelatinous
matrix containing small crystals. The crystals stimulate cilia on receptor cells.
4. Equilibrium (sensing motion):
a. the movements in the fluid in the semicircular canals stimulate cilia on receptor cells
D. The sense of touch also responds to mechanical stimulation
1. Many kinds of receptors within the dermis of the skin convert stimuli into nerve impulses.
2. Some detect gentle touches while others respond to heavy pressure.
3. The sensation of pain, heat, and cold are sensed by other kinds of receptors.
OBJECTIVE 9: DISCUSS THE IMPORTANCE OF COORDINATION OF STRUCTURES AND
FUNCTIONS OF ORGAN SYSTEMS
A. The coordination of structures and functions of the organ systems allows the internal environment of
the human body to remain relatively stable (homeostatic) despite changes to the outside environment.
1. The complementary activity of the major body systems provides cells with oxygen and nutrients
and removes toxic products such as carbon dioxide and nitrogen compounds.
B. See handout integration of systems
C. All of these chemicals are transported by the circulatory system and the cells. Organs at the final
destination direct the chemicals to their exit from the circulatory system.
OBJECTIVE 10: DESCRIBE HOW THE CIRCULATORY SYSTEM MAINTAINS HOMEOSTASIS, THE
STRUCTURE OF THE HEART, HOW THE HEART BEATS, THE FLOW OF BLOOD
IN THE BODY AND HOW THE CIRCULATROY SYSTEM SUPPORTS OTHER
SYSTEMS SUCH AS DIGESTIVE, RESPIRATORY AND EXCRETORY
A. The body’s transport system is the circulatory system, consisting of blood, the heart, blood vessels
and the lymphatic system. They work together to maintain homeostasis.
1. The circulatory transports many important substances like oxygen and nutrients.
2. The circulatory system allows cells to get rid of waste.
3. The blood carries disease fighting materials produced by the immune system
4. The blood has cell fragments and proteins for clotting blood.
5. The circulatory system distributes heat throughout the body to help regulate body temperature
B. Your heart is a little larger than your fist and it functions to keep the blood moving constantly
throughout the body. It pumps oxygenated blood to your body and deoxygenated blood to your lungs.
1. Made of cardiac muscle high in mitochondria capable of conducting electrical impulses for muscular
contractions.
2. Consists of four chambers; two atria and two ventricles
a. atria: collect blood from the body (right) or lungs (left); thin
b. ventricles: pump blood to the body (left) or to the lungs (right); thick and muscular
c. valves are between the atria/ventricles and ventricles/vessels
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C. Heartbeat cycle:
1. The heart acts in two main phases
a. Phase one – atria fill with blood, then contract to fill the ventricles
b. Second phase – ventricles contract to pump blood out of the heart to the lungs and forward into
the body.
2. heartbeat: valves shutting, AV and then semilunar
D. Control of heart rate:
1. cardiac muscle has a built-in ability to contract, your brain, the medulla oblongata, only tells it to
speed up or slow down the rate of contractions.
2. The heart rate is set by the S/A node or pacemaker, a bundle of nerve cells located at the top of
the right atrium. Sends electrical impulses that spread over both atria and both ventricles.
E. A pulse is a surge of blood through an artery. Every time the heart beats a surge of blood flows from
the left ventricle into the aorta and then into the arteries.
1. Blood pressure is the force that the blood exerts as it pushes against the walls of an artery.
2. Blood pressure rises and falls as the heart contracts(systole) and then relaxes (diastole).
3. Blood pressure can be increased by exercise, stress, and alcohol. An average adult blood
pressure is 120 (systolic pressure)/80 (diastlolic pressure)
F.
Blood circulates around the heart and lungs (pulmonary) and the heart and body tissues (systemic)
1. Pulmonary Circulation:
a. rv--. pulmonary arteriesà arteriesà arteriolesà capillaries around alveoli to drop of CO2 and
pick up O2à venulesà veinsà pulmonary veinsà la
2. Systemic Circulation:
a. lvà aortaà ateriesà arteriolesà capillaries around the body tissues to drop of O2 and pick up
CO2à venulesà veinsà superio/inferior vena cavasà ra
G. There are three important areas concerning circulation:
1. Coronary circulation: around the heart muscle
2. Hepatic-portal circulation: between the small intestine and liver for nutrient regulation
3. Renal circulation: kidneys
H. The digestive and respiratory systems depend on the circulatroy system to transport nutrients and
oxygen to the cells and wastes and carbon dioxide away from the cells. The excretory system utilizes
the kidneys to maintain homeostasis by removing wastes and excess water from the body and
maintaining the pH of the blood. The systems are interdependent on one another.
OBJECTIVE 11: DESCRIBE THE MECHANICS OF BREATHING AND THE CONTROL OF
RESPIRATION
A. The action of your diaphragm and the muscles between your ribs enable you to breathe in and out.
B. Inhalation:
1. Muscles between your ribs contract raising the rib cage
2. Diaphragm contracts, becomes flattened and moves lower into your chest cavity
3. Increased space in the chest cavity creates a slight vacum and air rushes in
C. Exhalation:
1. Muscles of the ribs and your diaphragm relax and ribs drop down in the chest cavity.
2. Volume of the chest cavity decreases and forces most of the air out. Some air remains in the
alveoli.
D. Breathing is usually an involuntary process, controlled by the chemistry of your blood as it interacts
with a part of your brain called the medulla oblongata.
1. Medulla oblongata maintains homeostasis.
higher levels of xcarbon dioxide in the blood causes it to send nerve signals to the rib muscles and
diaphragm. Nerve impulses cause these muscles to contract and you inhale.
OBJECTIVE 12: DESCRIBE THE STRUCTURES AND FUNCTIONS OF THE URINARY SYSTEM AND
HOW THEY HELP TO MAINTAIN HOMEOSTASIS
A. Know the structures and functions of your diagrams
B. Excretion is the removal of cellular wastes: CO2, H2O, and nitrogen compound to help regulate the
chemical makeup of the blood and other body fluids
1. Excretion can be carried out by the liver, skin glands, lungs, and the urinary system
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C. The urinary system is composed of two kidneys, a pair of ureters, the urinary bladder, and the urethra.
D. The kidneys filter the blood to remove wastes from it, thus maintaining homeostasis.
E. Structures and Functions within Urinary System:
1. nephron: functional unit of the kidney; 1.25 million/kidney
2. blood enters kidney through renal artery
3. filtration: at the glomerulus (ball of capillaries) all substances ( that are small enough) pass from
the blood into the Bowman’s capsule
4. reabsorption of useful materials out of the Loop of Henle and into surrounding capillaries
a. water by osmosis
b. active transport of nutrients, amino acids, and salt ions
c. maintains homeostasis
5. excretion: whatever is not reabsorbed (urine) goes to the collecting ductà pelvisà ureterà
bladderà urethraà out
a. Urine is excess water, waste molecules, and excess ions
F. The urinary system helps maintain the homeostasis of body fluids:
1. Removes urea and ammonia, both of which are toxic by products from the breakdown of proteins
2. Controls the level of sodium in the blood by removing and reabsorbing sodium ions (controls
osmotic pressure of the blood)
3. Regulates the pH of the blood by filtering out hydrogen ions and allowing bicarbonate to be
reabsorbed back into the blood.
OBJECTIVE 13: RECOGNIZE THE DIFFERENT FUNCTIONS OF THE DIGESTIVE TRACT AND
DIFFERNTIATE BETWEEN CHEMICAL AND MECHANICAL DIGESTION
A. The main function of the digestive system is to disassemble the food you eat into its component
molecules so that it can be used as energy for your body.
B. Digestion is accomplished through a number of steps:
1. The system takes ingested food and begins moving it through the digestive tract.
a. Mechanical digestion occurs when teeth or muscles physically break the food down into
smaller pieces. Prepares food for chemical digestion.
b. Chemical digestion occurs when enzymes are used to break the bonds between molecules so
that nutrients can be absorbed.
2. The system absorbs the digested food and distributes it to your cell via the circulatory system
3. The system eliminates undigested materials from your body.
OBJECTIVE 14: KNOW THE ORGANS AND ENZYMES OF THE HUMAN DIGESTIVE SYSTEM AND
BE ABLE TO EXPLAIN HOW EACH CONTRIBUTES TO DIGESTION
A. Mouth:
1. Mechanical digestion (teeth) of everything and chemical (salivary amylase) digestion of
carbohydrates.
2. Tongue pushes food to the back of the mouth, swallow, food in pharynx, and the epiglottis covers
the trachea.
B. Esophagus:
1. peristalsis – wave-like contractions push the food towards the stomach (see page 950)
2. cardiac sphincter is the valve between the stomach and the esophagus
C. Stomach:
1. Mechanical digestion (muscles ) of everything and chemical digestion of proteins
a. pyloric glands – secret mucus to protect the stomach lining
b. gastric glands – secrete HCl and the enzyme pepsin for the digestion of proteins. This is
stimulated by thought, smell, sight, or taste of food or stretching of the walls of the stomach
2.Food will stay in your stomach for 2-4 hours. The end product is called chyme
3. Pyloric sphincter – the valve between the stomach and the small intestine
4. Ulcers: not enough mucus or may be caused by a virus.
D. Small Intestine:
1. Muscle contractions contribute to further mechanical breakdown of the food (food stays here 3-5
hours)
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2. Chemical digestion continues and ALL absorption occurs here
3. Chyme is mixed with;
a. bile (made in the liver, stored in the gall bladder) for the digestion of fats and oils
b. pancreatic and intestinal juice digest carbohydrates, fats, and proteins
c. enzymes from these organs are secreted into the small intestine by ducts
4. Absorption is good because the small intestine has tiny folds (microvilli) on folds (villi) on folds.
This increases the surface area for absorption. Each villi has a good capillary blood supply.
E. Large Intestine:
1. No digestion, only absorption of water and vitamins (anaerobic bacteria here synthesize vitamins B
and K )
a. diarrhea: too fast
b. constipation: too slow
2. After 18-24 hours the remaining indigestible material now called feces reaches the rectum and is
eliminated through the anus.
3. A meal’s entire journey from the beginning of the digestive tract to the end has taken between 2433 hours.
OBJECTIVE 15: CONTRAST THE ACTIONS OF STEROID AND AMINO ACID HORMONES
A. Once hormones are released by an endocrine gland, they travel to the target tissue to cause a
change. Hormones are grouped into two basic types according to how they act on their target cells.
1. Steroid hormones:
a. made from lipids and diffuse freely through plasma membranes (see page 963)
b. Bind to a hormone receptor and travels to the nucleus to direct the synthesis of specific mRNA
c. mRNA activates the synthesis of specific proteins
d. All sex hormones are this type
2. Amino acid hormones:
a. Can be either short or long chains of amino acids
b. Once secreted into the bloodstream they bind to receptors embedded in the plasma membrane
of the target cell (see page 963).
c. Open ion channels in the membrane, or route signals down from the surface of the membrane to
activate enzymes inside the cell.
d. These enzymes alter the behavior of other molecules inside the cell.
e. Most hormones are this type.
OBJECTIVE 16: DESCRIBE VARIOUS ORGANS OF YOUR ENDOCRINE SYSTEM AND THEIR
EFFECTS ON YOUR BODY
A. Know the location and function of these organs on a diagram
B. Pineal: secretes melatonin effecting body’s internal clock
C. Hypothalmus: link between the nervous and endocrine system
D. Pituitary: master gland because it controls other glands
1. sperm and egg development
2. hypersecretion: overstimulation of other glands, gigantism. Lactation
3. hyposecretion: dwarfism, so sexual development
E. Thyroid: rate of metabolism
1. hypersecretion: nervous, low weight, eyes protrude
2. hyposecretion:
(a) in infancy can cause mental retardation
(b) in adults can cause weight gain and decrease in mental activity
F. Parathyroid: regulates calcium levels ( nerves, muscle and bone)
G. Thymus: role in development and function of immune system
H. Adrenal: helps body to resist stress
I. Pancreas: problems with this gland result in diabetes
1. secretes insulin which decreases glucose levels in the blood
2. secretes glucagon which increases blood glucose levels
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J. Ovaries: secretes estrogen and progesterone which stimulates the development of the female
reproductive system and regulates the menstrual cycle.
K. Testes: secretes testosterone which stimulates the development of the male reproductive system
OBJECTIVE 17: DESCRIBE THE ENDOCRINE SYSTEM AND HOW IT COMPARES TO AND
INTERACTS WITH THE NERVOUS SYSTEM
A. Internal control of the body is regulated by the nervous system and the endocrine system
1. Feedback loops in the nervous and endocrine systems regulate conditions in the body.
B. The endocrine system is made up of a series of glands, endocrine glands, which release chemicals
(hormones) directly into the bloodstream.
1. Hormones are released from part of your body act as messengers relaying information to other
parts of the body.
2. secretions from the endocrine system affect metabolism, homeostasis, growth, reproduction and
behavior
3. Hormones travel in the blood stream and attach to specific binding sites (receptors) found on the
plasma membranes, or in the nuclei, of target tissue cells.
C. The endocrine system produces a gradual change compared to the immediate response produced by
the nervous system.
D. Messages from the endocrine system last longer than messages produced by the nervous system
E. Because some glands actually control others, nerve and blood vessels must connect them.
F. The presence or absence of hormones in the blood brought to the brain by the circulatory system will
trigger appropriate body stimuli in an attempt to regulate body conditions.
OBJECTIVE 18: SUMMMARIZE THE NEGATIVE FEEDBACK MECHANISM USING HORMONE
LEVELS IN THE BODY AS AN EXAMPLE
A. The amount of hormone released from a gland is determined by your body’s demand for that hormone
at a given time. Ensures that the right amount is in your system at all times.
B. The endocrine system is controlled by negative feedback system, a system in which the hormones,
or their effects, are fed back to inhibit the original signal
1. If hormone level is too low the glands will start secreting, if the level of hormone is too high, the
gland will stop secreting.
2. Example is regulation of blood glucose
a. blood: normal glucose levels
b. eat: glucose levels rise in the blood
c. pancreas begins secreting insulin into the bloodstream
d. Insulin causes liver and other tissues to take up more glucose
e. Homeostasis restored, return to normal glucose levels in the blood.
3. A and B represent two related metabolic processes. An increase in A causes an increase in B.
However, the change in B also causes a change in A. This is called feedback. If the change
caused by B is opposite to the original change in A, the feedback is called negative. Negative
feedback prevents A from changing very much in either direction; and helps to maintain
homeostasis. (refer to Objective 1: C)
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