26-1 Chapter 26 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

26-1

Chapter 26

Lecture Outline

See PowerPoint Image Slides

for all figures and tables pre-inserted into

PowerPoint without notes.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.26-2

Coordination in Multicellular Animals

Maintaining a constant internal environment is crucial for large multicellular organisms.

– Accomplished by monitoring and modifying the functioning of various systems

– Called homeostasis

Homeostasis maintains oxygen levels, blood pressure, heart rate, body temperature, fluid levels, pH, etc.

Homeostasis is maintained by the nervous, endocrine and immune systems.

Example: Running up a hill


Negative Feedback Control

A common homeostatic mechanism

Occurs when an increase in the stimulus results in a decrease in response

Functions to maintain a set point

Example: Thermostat


Positive Feedback Regulation

When an increase in stimulus results in an increase in response

Does not result in homeostasis, but plays an important role in homeostasis

– Childbirth


Nervous System Function

Important in making adjustments over a short time period

Transmission of information is very fast in the nervous system.


The Structure of the Nervous System

Consists of a network of cells that carry information from one part of the body to another

Made up of specialized cells called neurons– Cell body or somacontains the nucleus– Dendritesreceive information and carry it to the

cell body– Axonscarry information away from the cell body


The Anatomy of a Neuron


Central Nervous System

Brain and spinal cord Protected by skull and vertebrae Receives input from sensory organs Interprets and integrates information Generates responses


Peripheral Nervous System

Located outside the skull and vertebral column

Consists of bundles of axons and dendrites called nerves– Somatic nervous system

Nerves that control the skeletal muscles

– Autonomic nervous system Nerves that control the involuntary muscles, the heart

and glands


Types of Neurons

Motor neurons– Carry messages from the central nervous system

to muscles and glands– Usually have one long axon that runs from the

spinal cord to the muscle or gland Sensory neurons

– Carry input from sense organs to the central nervous system

– Have long dendrites that carry input from the sense organ to the brain or spinal cord


Organization of the Nervous System


The Nature of Nerve Impulses

Information is transmitted through neurons in the form of nerve impulses.– Also known as action potentials– Involve a sequence of chemical events at the cell

membrane of the neuron


Neurons have an Unequal Distribution of Ions Inside and Outside of the Cell

Active transport pumps sodium out and potassium in– More sodium is pumped out than potassium

pumped in– As a result

Sodium is concentrated outside the cell. Potassium is concentrated inside the cell.


Neurons have an Unequal Distribution of Ions Inside and Outside of the Cell

This unequal distribution of charge generates a voltage across the neuronal cell membrane.

– Voltage is a measure of the electrical charge difference that exists between two points.

– The inside of the cell is more negative than the outside.– At rest, the membrane voltage of a neuron is about -70mV.

The voltage across the membrane makes it polarized.


The Polarization of Cell Membranes


Generation of a Nerve Impulse

When a neuron is stimulated by an input …– The cell membrane becomes more permeable to

sodium.– Sodium ions enter the cell down their

concentration gradient.– The inside of the cell becomes more positive.– The cell is depolarized.

The depolarization spreads down the axon.


Generation of a Nerve Impulse

Depolarization of any one segment of membrane is brief.– Membrane becomes repolarized when potassium

flows out of the cell

Repolarization is followed by the pumping of sodium out of and potassium into the cell.– This re-establishes the original concentration

gradients.– This brings the cell back to its resting membrane

potential.


The Nerve Impulse


Activities at the Synapse

The synapse is the small space between the axon of one neuron and the dendrite of another neuron.

Neurons communicate with one another through the activities at the synapse.

When the nerve impulse in one neuron reaches the synapse, chemicals are released from the end of the axon.

– Called neurotransmitters– Diffuse across the synapse and bind to receptor sites on the

dendrite of the other neuron– This can cause depolarization and generate a nerve

impulse in the second neuron.


Events at the Synapse


Neurotransmitters

Made in the cell body and transported to the end of the axon to be stored until released.

– Acetylcholine was the first neurotransmitter identified.

Bind to receptors and stimulate them as long as they are bound

Enzymes in the synapse destroy neurotransmitters, allowing the second cell to return to resting state.

– Acetylcholinesterase is the enzyme that breaks down acetylcholine.

Many drugs interfere with neurotransmission at the synapse.


Direction of Information Flow

Information in the nervous system only travels in one direction…– From the axon of one cell to the dendrite of

another in a synapse– From the dendrites to the cell body of one neuron– From the cell body through the axon to the

synapse


The Organization of the Central Nervous System

The brain consists of several different regions that have specific functions.

The functions of the brain can be divided into three major levels.– Automatic activities– Basic decision making and emotions– Thinking and reasoning



Spinal cord– Collection of neurons and nerve fibers surrounded by the

vertebrae– Conveys information to and from the brain

Medulla oblongata– The base of the brain where the spinal cord enters the brain– Controls fundamental life support activities such as

Blood pressure Breathing Heart rate

– Fibers from the spinal cord cross sides in the medulla Right side of body is controlled by left side of brain and vice

versa



Cerebellum– Large bulge at the base of the brain– Connected to the medulla oblongata– Receives information from sensory organs that

involve balance Inner ear, eyes, pressure sensors in muscles and

tendons

– Regulates muscle activity to establish balance and coordination



Pons– The region of the brain that is anterior to the medulla

oblongata– Controls many sensory and motor functions of the head and

face Thalamus

– Located between the pons and the cerebrum– Relays information between the cerebrum and the lower

centers of the brain Spinal cord, medulla, pons

– Important in awareness– Involved in sleep and arousal



Hypothalamus– Involved in sleep and arousal– Important in emotions

Fear, anger, pleasure, hunger, sexual responses, pain

– Regulates body temperature, blood pressure and blood volume

– Connected to and controls the pituitary gland Controls the release of hormones


The Functions of More Primitive Brain Regions



Cerebrum– The thinking part of the brain.– Comprised of two hemispheres– Controls memory, language, movement– Responsible for the integration of sensory input– The major site of association and cognition.


Specialized Areas of the Cerebrum


Endocrine System

The Endocrine system– A collection of glands that communicate with one another and with

body tissues through the release of hormones. Hormones

– Chemical signals released by one organ that are transported to another organ where it triggers a change in activity

Glands– Organs that make and release specific chemicals– Endocrine glands

Lack ducts Secrete hormones in to the circulatory system

– Exocrine glands Have ducts Release their products into the digestive tract or onto the skin Digestive glands, sweat glands


Endocrine Glands


Endocrine System Function

Hormones released by endocrine glands travel throughout the entire body.– However, they only bind to and affect target cells

that have receptors. Target cells respond by

– Releasing products that have been previously made

– Making new molecules or increasing metabolic activity

– Dividing and growing


Some Examples of Hormone Action

Epinephrine and norepinephrine– Released by the adrenal medulla during emergency

situations– Acts quickly

Increases heart rate, blood pressure and breathing rate Shunts blood to muscles

Antidiuretic hormone– Released from posterior pituitary in response to dehydration– Acts more slowly

Targets kidney cells Increases the re-absorption of water


Some Examples of Hormone Action

Insulin– Works rapidly– Produced and released from the pancreas– Stimulates cells to take in glucose – Is released in response to high glucose levels in the blood

Would occur after a high carbohydrate meal– Diabetes is a lack of insulin

Cells don’t take in glucose

Growth-stimulating hormone– Works over a period of several years during childhood– Produced by the anterior pituitary– Stimulates growth


Integration of Nervous System and Endocrine System Function

The pituitary gland links the endocrine system to the nervous system.

– Located at the base of the brain– Divided into two parts

Anterior pituitary– An endocrine gland– Produces hormones that trigger other glands to release their

hormones– Receives commands from the chemicals released from the

hypothalamus Posterior pituitary

– Part of the brain– Holds the axons from cells in the hypothalamus– Releases specific hormones into the bloodstream


Hormones of the Pituitary


Integration of Nervous System and Endocrine System Function

Example: In songbirds, the length of day causes hormonal changes that prepare the animals for reproduction.

– Length of day is sensed by the pineal body in the brain.– The pineal gland controls the release of chemicals from the

hypothalamus.– The chemicals released by the hypothalamus trigger the

pituitary to release hormones into the bloodstream.– These pituitary hormones stimulate the reproductive organs

to secrete reproductive hormones.– These reproductive hormones trigger courtship and mating

rituals in birds.


Interaction Between the Endocrine and Nervous Systems


Sensory Input

The nervous and endocrine systems respond to sensory input.– This input comes from sense organs.– Some sense organs detect external stimuli.

Vision, hearing, touch

– Other sense organs detect internal stimuli. Pain and pressure

The sense organs detect changes; the brain is responsible for perception.


Chemical Detection

All neurons have chemical receptors on their surface.– When chemicals bind to these receptors, the

activity of the cell changes.– Usually results in depolarization and the

generation of a nerve impulse. Other types of cells have chemical receptors

as well.– The aorta can sense and respond to changes in

hydrogen ions, carbon dioxide and oxygen in the blood.


Taste

Taste buds are sensory cells located on the tongue.

They have chemical receptors that respond to classes of molecules.

These classes correspond with the five kinds of taste we experience.– Sweet, sour, salt, bitter and umami (meaty)


Taste

Sour and salty sensation results from ions entering taste buds and causing a depolarization.

– Sour sensing taste buds respond to hydrogen ions.– Salty sensing taste buds respond to sodium chloride.

Sweet, bitter and umami sensations result from molecules binding to receptors on taste buds.

– Sweet receptors are stimulated by sugars, artificial sweeteners, etc.

– Umami receptors are stimulated by glutamate.


Smell

The sensory receptors in the nose are more versatile than taste buds.– They can sense thousands of different molecules

at low concentrations.– Found in the olfactory epithelium– Very sensitive– Fatigue quickly


Vision

The sensory cells in the eyes respond to changes in the flow of light energy.

Light-sensing cells are found in the retina.– At the back of the eye– The other parts of the eye are designed to focus light

onto the retina Light-sensing cells are called rods and cones.

– Rods are very sensitive and can detect dim light but not color.

– Cones are less sensitive, but can detect different wavelengths of light (color).

– This is why we cannot see color at night.


The Structure of the Eye


Vision

The fovea centralis is a region in the retina with many cones and no rods.

– This area gives us the most focused and detailed vision. Rods and cones sense light because they contain

pigment molecules.– Rhodopsin is the pigment in rods.– When light hits rhodopsin, it changes shape and causes the

rod to depolarize.– This generates a nerve impulse that is sent to the brain.– Different types of cones have different pigments that

respond to specific wavelengths of light.


Light Reception by Cones


Hearing and Balance

One set of sensory cells in the ear responds to changes in sound waves.

– These sensory cells are found in the cochlea.– Sound is produced by the vibration of molecules.

Volume is a measure of the intensity of the vibration. Pitch is determined by the frequency of the vibration.

The other set of sensory cells in the ear responds to movements of the head.

– These cells are found in the fluid-filled semi-circular canals.– They sense the position of the head with respect to the

force of gravity. Helps maintain balance


The Anatomy of the Ear


Hearing

The ear is designed to funnel sound and transmit the vibrations to the sensory cells.

– External ear funnels sound to the eardrum.– The eardrum (tympanic membrane) vibrates in response to

sound.– The vibration is passed to small bones (malleus, incus and

stapes) in the middle ear.– The bones, in turn, vibrate another membrane covering the

oval window.– The oval window is an opening into the cochlea.


Hearing

The cochlea is a tube filled with fluid under pressure. When the oval window vibrates, the fluid in the

cochlea vibrates. This vibration causes the basilar membrane to

vibrate. Sensory cells on the basilar membrane are

depolarized when it vibrates. The depolarization generates a nerve impulse that is

transmitted to the brain.


Touch

Sensory receptors in the skin and internal organs respond to changes in pressure and temperature.

– Found all over the body, but more concentrated in certain areas

Tips of fingers, genitalia, lips, etc. That is why these areas are the most sensitive to touch.

Pain receptors in the skin and internal organs respond to cell damage and extreme pressure and temperature.

– Allows our brain to monitor our internal activities


Output Coordination

After sensing changes in the external or internal environments,– The nervous and endocrine systems work

together to cause a change in response.

Responses may involve– Muscle contraction– Hormone secretion by glands


Muscles

Muscle contraction facilitates movement. Muscles pull by contracting.

– But, they do not push by lengthening.– Relaxation is merely passive.

Muscles exist in antagonistic sets.– The biceps cause the arm to bend.– The triceps cause the arm to extend.– Biceps and triceps are antagonistic muscles.


Antagonistic Muscles


Muscular Contraction

A muscle is made up of many muscle cells. Muscle cells are made up of many myofibrils. Myofibrils are bundles of fibers made up of

myofilaments.– When these fibers move past one another, the

muscle contracts.– This movement requires the energy from ATP.


Myofilaments and Contraction

Myofilaments are either thick or thin.– Thick filaments are made of myosin.

Shaped like a golf club The head of the ‘golf club’ is positioned to bind to the

thin filaments.– Thin filaments are made of actin, tropomyosin and

troponin. Actin filaments are shaped like two pearl necklaces

intertwined. Tropomyosin and troponin are shaped like a gold thread

that is laid on the pearl necklace.– These molecules block actin and prevent the interaction

between actin and myosin.


The Events of Muscle Contraction

The nerve impulse arrives at the muscle cell. The muscle cell depolarizes. Calcium ions are released onto the myofibrils. The calcium ions bind to troponin, causing the

troponin-tropomyosin complex to move. This exposes actin, allowing myosin and actin to

interact. Myosin heads bind to actin, the heads flex, pulling

actin. This causes the muscle cell to shorten (contract).


Interaction Between Actin and Myosin


Types of Muscles

There are three types of muscles:– Skeletal

Mediate voluntary movement Arms, legs, neck, back, abdomen, lungs

– Smooth Mediate involuntary movement Digestive tract, reproductive tract

– Cardiac Heart muscle


Skeletal Muscles

Voluntary muscle Controlled by the brain

– Brain sends the command to the spinal cord– Spinal cord sends the command to the muscles


Skeletal Muscles

Many neurons from the spinal cord end in each muscle.– Each neuron stimulates a specific set of muscle

cells called a motor unit. A motor unit is one neuron and all of the muscle cells it

stimulates to contract.

– Each muscle has many motor units.– This allows for different intensities of contraction

in one muscle.– The intensity of contraction is dependent on how

many motor units are stimulated at once.


Skeletal Muscles

Skeletal muscle cells contract quickly, but fatigue quickly.– Different motor units must be recruited to keep a

muscle contracted for a long time.


Motor Units


Smooth Muscles

Found in the muscular walls surrounding internal organs

Contract in response to being stretched– Digestive system

Is constantly stretched as food passes through The responsive contractions result in rhythmic movements that

move food through

Involuntary– Do not need direct messages from nervous system– Some respond to hormones

Uterine contractions in response to oxytocin


Cardiac Muscle

Makes up the heart Can contract rapidly without direct nervous

system stimulation The rate of contraction can be controlled by

– The nervous system– Hormones (epinephrine and norepinephrine)

Cannot stay contracted for a long time– Must relax between contractions


Characteristics of Different Kinds of Muscles


Activities of Glands

There are two types of glands.– Endocrine glands

Secrete hormones into the bloodstream Pituitary, thyroid, ovary, testes, etc.

– Exocrine glands Secrete substances to the surface of the body or into the

tubular organs (gut, reproductive tract) Salivary glands, intestinal mucus glands, sweat glands, etc. Some are controlled by the nervous system (salivary). Some are controlled by hormones (digestive).


Growth Responses

Hormones regulate growth.– Growth-stimulating hormone is produced throughout

childhood to increase the size of the body.– Testosterone released during puberty in males stimulates

Bone and muscle growth– This is why men are generally taller and more muscular than

women. Growth of the penis, larynx and hair on face and body

– Estrogen released during puberty in females stimulates Growth of reproductive organs Development of breast tissue Start of the menstrual cycle


The Body’s Defense Mechanisms

Immunity is the ability to maintain homeostasis by resisting or defending against potentially harmful agents.

– Microbes, toxins, tumor cells, etc.

The immune system is made up of specialized cells and molecules that fight infection and disease.

– Generates nonspecific and specific defenses– Nonspecific defenses protect the body from a lot of things.– Specific defenses recognize specific threats and attack

them in specialized ways.


Nonspecific Defenses

General ways that the body prevents disease and infection

No previous contact with the danger is required.


Nonspecific Defenses

Defensive barriers – Skin and mucous membranes – Block the entry of pathogens– Lysozyme, found in skin, destroys bacterial cells.– Mucus traps pathogens so that they can be eliminated.

Chemicals – Complement proteins circulate in the blood and help

immune cells attack and kill pathogens.– Interferons are proteins that prevent viruses from attaching

to and entering cells. Certain types of cells

– Cells and chemicals interact to mediate inflammation. A series of events that clears a damaged area of harmful

agents and damaged tissue


Inflammation


Specific Defenses

These mechanisms must be turned on by a primary exposure to the harmful agent.

– Therefore, it is called “acquired immunity”. The harmful agent that causes a response is called an

antigen.– Usually a large protein– Stimulates the production of a specific defense mechanism– Becomes neutralized or destroyed by that mechanism– Can be toxins or parts of viruses or bacterial cells

T-lymphocytes and B-lymphocytes respond to antigens.– Each type of lymphocyte works a little bit differently.– Each are needed for specific immunity to work correctly.


B-cell and Antibody Mediated Immunity

B-lymphocytes (B-cells) are made in bone marrow.– Found mostly in lymph nodes and spleen

When a B-cell contacts an antigen– Information is sent to the nucleus and genes are activated.– This results in an antibody being made that is specific to

that antigen.– The antibody will be released by the B-cell and will bind to

the antigen, making it a target for destruction.


Classes of Antibodies



After antigen binding, that B-cell will only make that specific antibody. – It has been activated.– All of their descendants will only produce that antibody.– Some descendants will be plasma cells that make and

release antibodies.– Some descendants will be memory cells.

During the infection/danger, plasma cells outnumber memory cells.



After the infection/danger, plasma cell number drops; but memory cells remain.

When the same antigen appears again– The memory B-cells produce more plasma cells

very rapidly.– The plasma cells make and release antibody that

leads to the elimination of the threat.


Immunization

A technique to induce an acquired immune response

Utilizes vaccines to expose the body to an antigen without causing an infection– Usually contains pieces of the bacteria or virus– Some are synthetic, with molecules that mimic the

real antigen.


Immunization

When the vaccine is given, the B-cells react as described.– This is called a primary immune response.– Generates memory B cells

When the real antigen is encountered again (during infection)– The memory B cells generate a swift, massive

response.– Eliminates the infection before illness sets in


Active Immunity due to Immunization


T-cell and Cell-mediated Immunity

T-lymphocytes (T-cells) are made in bone marrow.– Mature in thymus– Found in blood, lymph and lymph tissue– Regulate B-cell activity– Rupture pathogens, virus-infected cells and

cancer cells


Becoming a Specialized T cell


Activating T-cells

T-cells only become active if the pathogen is “presented” to it by other cells.– Called antigen presenting cells (APCs)– These are macrophages that have ingested the

pathogen.– They break the pathogen into pieces and send

the pieces to their cell surface.– The APCs then present the antigen to the T-cells.


Activating T-cells

When the T-cell detects the antigen, a signal is sent to the nucleus, DNA is altered and the cell becomes differentiated into one of three forms.– T-regulator cells– Cytotoxic T-cells– T-memory cells


Types of T-cells

T-regulator cells– Communicate with B-cells and help them control

the amount of antibody produced– Two types of T-regulator cells

T-helper cells encourage B-cells to make antibodies. T-suppressor cells inhibit B-cells from making

antibodies.


Types of T-cells

Cytotoxic T-cells– Move toward the pathogen and make holes in it– Target bacteria, cancer cells, transplanted cells,

parasites– Release cytokines, chemicals that attract WBCs

to the site of infection T-memory cells

– Remember specific antigens so that a faster response can be initiated upon repeated exposure


Allergic Reactions

An allergy is an abnormal immune reaction to an antigen.– If the antigen comes from outside the body, it is

called an allergen. Food, pollen, drugs

– Involves an interaction between the antigen and a B-cell antibody


Allergic Reactions

Type I hypersensitivity– Associated with an antibody called IgE– Upon first exposure, the allergen stimulates a

B-cell to make IgE.– Upon second exposure to the allergen, the B-cells

make a lot of IgE. IgE stimulates the release of histamine, leukotrienes

and prostaglandins. These chemicals cause skin rashes, hives, asthma,

eczema, headaches, etc.


Allergic Reactions

Anaphylactic shock– The most severe allergic reaction– Starts with reddening of the skin and progresses

through a severe drop in blood pressure and can lead to death.

– Epinephrine will block the progression of anaphylactic shock.


How an IgE Allergy Works


Autoimmune and Immunodeficiency Diseases

Autoimmune diseases result from the immune system turning against normal cells or molecules in one’s body.

– The immune system attacks and kills normal, healthy cells.– Rheumatoid arthritis - normal cartilage is attacked.– Type I diabetes - cells that make insulin are attacked.

Immunodeficiency disease results when one or more components of the immune system do not work properly.

– Makes people more susceptible to infections and cancers.– SCIDS - a genetic immunodeficiency disease– AIDS - a viral-induced immunodeficiency disease

26-1 Chapter 26 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

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