Biology Exam 4

nervous system

receives and integrates information

initiates rapid responses to that information

the human nervous system enables us to think, remember, empathize, write poetry, make music, and enjoy sensations

neurons

cells in the nervous system

can transmit signals from one part of the body to another quickly

peripheral nervous system (PNS)

nerves and nervous tissues

the PNS gathers information from the external and internal environment and sends it on to the CNS

central nervous system

brain and spinal cord

processes PNS information and often generates a return signal to be delivered by the PNS to the body parts that will execute the signal

neuron

a specializes cell that can receive and transmit information from many different types of cells

dendrites and axons

dendrites: that receive signals from adjacent cells

axons: which specialize in transmitting signals to other cells

myelin

an insulating sheath made of a fatty material produced by glial cells which surround the axons

myelinated axons can carry signals more rapidly than unmeyelinated axons

nerve

made up of many individual neurons bundled together with supporting cells, blood vessels, and connective tissue to form a major communication pathway

the peripheral and central nervous system exchange information

sensory neurons from the PNS convey sensory input to interneurons in the CNS

interneurons process and may send them directly to the motor neurons for immediate action or to the brain for further processing

an interneuron may also send its output up to the brain and out to the PNS at the same time ina simultaneous flow

voluntary vs involuntary

reflex arc

consists of a sensory neuron that send the message to the spinal cord

then an interneuron

and finally a motor neuron that creates a response in the body

action potential

a pulse of electrical disturbance that travels down the length of an axon

triggers the release of chemical messengers called neurotransmitters the signal to the next cell in this line of communication

action potentials are propogated along the length of an axon

an action potential is a self sustaining electrical signal that travels away from the body of the neuron

the action potential is dependent on the positively charged ions moving across the plasma membrane

the plasma membrane is in a polarized state because there is a difference in electrical charges across the plasma membrane

the electrical charge that exists across the plasma membrane of an unstimulated neuron is known as the resting potential

a stimulus depolarizes a neuron if the flow is changed in such a way that many more positivitely charged ions are able to enter the cell

once the action potential has passed the neuron returns to its resting potential

nodes of ranvier

the site of action potentials

unmyelinated gaps between the myelin sheath

myelinated axons transmit action potentials especially rapidly

action potentials are sped up by the presence of the myelin sheath

the action potential is regenerated at each node allowing the signal strength to jump rapidly from one node of ranvier to the next

action potentials have several important features

they move along the axon in only one direction keeping the signal from being lost

remains consistently strong as it moves from one end of the axon to the other and does not weaken with distance

a strong stimulus will initiate action potentials more often but any individual action potential will be no stronger than any other it is an all or none event

synapse

a junction where the electrical signal is converted into a chemical message and relayed to the next cell

neurotransmitters

the chemical messangers

transmission of the information at a synapse takes place across a tiny fluid filled gap between two cells called the synaptic cleft

forebrain

cerebrum, thalamus, hypothalamus

cerebrum

divided into two hemispheres

bundles of axons carry information between the right and left hemispheres

cerebral cortex

highly folded part

responsible for our capacity to talk, calculate, create art, and conciously sense the world around us

thalamus

determines which of the sensory signals coming from the spinal cord should go to the conscious perception centers in the cerebrum

hypothalamus

helps integrate the nervous system and the endocrine system

the cerebrum is divided into 4 major lobes - each of the hemispheres of the cerebrum has four major lobes

frontal lobe: reasoning and problem solving

parietal lobe: speech, taste, reading, and sensation

occipital lobe: vision

temporal lobe: sound and smell

midbrain

helps control movement involved in motivation and reward seeking behaviors

helps maintain muscle tone and sends some sensory data to higher brain centers in the forebrain

hindbrain

coordinates information dealing with breathing rhythms, blood pressure, heart rate, and balance among many other functions

midbrain and hindbrain together make up the brain stem

sensory structures

chemoreceptors: chemicals (taste, smell)

photoreceptors: light (vision)

mechanoreceptors: physical changes (touch, hearing, proprioception (body position), balance)

thermoreceptors: moderate heat and cold (thermoreception (gradations of heat and cold)

pain receptors: injury, noxious chemicals, chemical and physical irritants (pain, itch)

electroreceptors: electrical fields (electrical sense)

magnetoreceptors: magnetic fields (magnetic sense)

chemoreceptors are found on cells that respond to chemicals such as those found on the tongue

chemoreceptors respond to chemicals

involved in two types of sensory perception: receptors on the tongue gives us our sense of taste, receptors in the nasal passages give us our sense of smell

taste involves sensing chemicals in direct contact with our bodies (food in the mouth)

chemoreceptors in the nasal passages enable us to smell

smell involves sensing molecules that are vaporized (gas forms) like the scent molecules released by a rose (for example)

mechanoreceptors

detect various kinds of physical stimuli both inside and outside the body

thermoreceptors

found in a variety of tissues including the skin, mouth, and internal organs

activated by temps in the moderate range

pain receptors

located on just about every tissue type inside and on the surface of the body and detect different types of noxious stimuli

activated by extreme temps

photoreceptors: vision

light sensitive pigment is required to sense light and dark

all image forming eyes have two common features: the light gathered from photoreceptor cells is focused to a single point in the array of photoreceptors, the photoreceptor cells convert light energy into nerve impulses that are sent by sensory neurons to the brain for processing

forming images requires a way to focus light

single lens eye focuses incoming light through a lens to the retina at the back of the eye

the pupil is an adjustable opening that controls the amount of light entering the eye

the retina is a sheet of photoreceptors that converts the light stimuli into nerve impulses

all vertebrates have a single lens eye

the human retina has two classes of photoreceptor cells called rods and cones that contain light sensitive pigments

rods: enable us to see images in shades of gray in dim light

cones: function best in bright light and transmit information in color

fovea

an area of densely packed rods and cones in the back of the human eye

allows us to form sharp colorful images of whatever is in the center of our view

herbivores eyes

have eyes that tend to be situated far apart on either side of the head

allowing them the wildest possible panoramic view

most predators eyes

have eyes situated close together on the front of the head to enable both eyes to focus on the same point at the same time

this gives them good depth perception

hearing

involves detecting waves of pressure change in air which spread out in all directions from the sound source

sound waves

diminish in intensity as they travel which explains why distant sounds are softer than the same sounds originating nearby

pitch

the number of pressure changes per second is known as the sounds frequency or what we perceive as pitch

loudness

reflects the intensity of the pressure changes in the sound waves

hearing process

the outer ear consists of the pinna which is the cartilaginous part that we identify as the external ear and the auditory canal

the outer ear is designed to concentrate sounds energy on the eardrum

the eardrum converts sounds energy into physical movements by vibrating in response to rapid changes in air pressure

structure of the human ear

the eustachian tube equalizes pressure differences between the middle and outer ears

in the middle ear vibrations from the eardrum are transmitted to a second membrane by three tiny bones which then channel them to the chochlea

in the cochlea are many organ of corti where vibrations of a basilar membrane are converted by mechanoreceptors into a pattern of nerve impulses

proprioceptors

specialized mechanoreceptors that respond to stretching of or pressure on muscles, tendons, and joints to inform us of the position of our bodies in space

vestibule

a structure in the ears helps us maintain our sense of balance, sense up from down, and detect head movements

semicircular canals

located in the vestibule and help us detect head movements

locomotion

ability to move from place to place

accomplished through skeletal structures and muscles

the skeleton

supports the body

gives it shape

protects soft tissue and organs

axial skeleton

supports and protects the long axis of the body

includes the skull, ribs, and a long bony spinal column

appendicular skeleton

makes movement possible

includes the arms, legs, and pelvis

compact bone

forms the hard white outer region

spongy bone

lies inside the compact bone

osteocytes

specialized bone cells that surround themselves with a hard nonliving mineral matrix composed largely of calcium and phosphate compounds

marrow

a tissue inside the cavity of bone that produces blood cells or stores fat

osteoclasts

special bone cells that remove tissue from the bone

osteoblasts

special bones cells that restore bone tissue

cartilage

dense tissue that combines strength with flexibility

made up predominantly of extracellular material containing collagen (an extremely pliable protein)

thin and lacks a blood supply therefore living cells in cartilage depend on diffusion to acquire oxygen and nutrients and remove wastes

joints

junctions in the skeletal system that let the skeleton move in specific ways

ligaments

flexible bands of connective tissue

join bone to bone to help hold a joint together

tendons

collagen rich

connect muscle to bone

how joints work

two pairs of ligaments connect the femur to the lower leg bones (prevents sliding along the joint surface when the knee bends)

knee joint: allows the lower leg to swing forward and back like a hinge but not side to side thereby providing both motion and stability

synovial sac

made of sheets of tissue that create a sac containing lubricating fluid that reduces friction between the two bony surfaces

how muscles work

muscle tissue is unique to animals and provides the power necessary for movement

muscle has the ability to contract and relax unlike any other tissue

a muscle fiber is made up of several muscle cells that fused together

each muscle fiber contains myofibrils which contain proteins that can contract against each other

muscle tissue can generate force by contracting

myofibrils are organized into contractile units called sarcomeres which are visible as bands when seen through a microscope

each sarcomere consists of actin filaments and myosin filaments made of proteins that attach to a z disc at each end

myosin and actin filaments interact to create a muscle contraction that produces force

skeletal and cardiac muscles have a banded appearance

most skeletal muscles are under voluntary control executing movements we choose to make

cardiac and smooth muscles are under involuntary control

cardiac muscle

found only in the heart

contains fibers that are joined by interconnecting branches that help them produce the coordinated contractions of the heart

smooth muscle

lacks the bands associated with other muscle types

its contractions are generally involuntary

smooth muscle lacks the banded appearance

the contractile proteins of smooth muscle cells interlink the plasma membrane on opposite sides of these spindle shaped cells and slide together producing a squeezing action

smooth muscle is also found in the digestive tract, the walls of blood vessels, the respiratory tract, and the urinary bladder

muscles that move body parts often work in opposing pairs

muscles that move limbs and other body parts are arranged in opposing pairs so that the contraction of one causes the other to relax

the triceps and biceps are an example of opposing pairs that work together to move the arms

thick muscles are stronger than thin muscles

all animals have essentially identical sarcomeres with the same actin and myosin molecules arranged in much the same pattern

strength differences among species and individuals depend almost entirely on the cross sectional area of the muscles

the greater the cross sectional area or thickness of the muscle the more muscle fibers it contains and the greater the contractile force the muscle can generate

comparing skeletons

animals have different skeletons but all have two basic functional features: stiff structures that maintain shape, joints that let the stiff parts of the skeleton move relative to one another

most skeletons are strengthened by tissues with a stiff extracellular matrix: hardened minerals (calcium salts), tough proteins (cartilage, collagen), carbohydrates (exoskeletons/chitin)

chitin

tough polysaccharide often interlinked by proteins

forms the exoskeletons of arthropods

hydrostat

many invertebrates rely on this type of structure for their skeleton

consisting of a fluid filled compartment surrounded by elastic and muscular tissue

many invertebrates depend on hydrostatic skeletons for structure and movement

fluid pressure within the body chamber gives shape to the bodies of soft bodied animals

movements of body parts powered by muscle contractions

relaxations exerted against pressurized fluid in the body cavity

endoskeleton

support tissues lies inside the body

humans and other vertebrates

exoskeleton

an external skeleton surrounds and encloses the soft tissues it supports

many invertebrates, lobsters, insects, etc.

provide a protective armor and prevent moisture loss in terrestrial animals

must be shed for animal growth

mixing of muscle fibers

two main types: slow (type 1), fast (type 2)

they differ in how fast they respond to the nerve impulses that trigger contractions and how long they can sustain a muscle contraction

different muscles have a different mix of slow and fast fibers depending on the main function of the muscle

the mix is also determined by genetics and affected by training

athletes in strength sports tend to have a high proportion of fast fibers while runners have many slow fibers

pathogens

disease causing agents and can be found on almost any surface we touch

include viruses, bacteria, and protists, some fungi, and multicellular animals

as pathogens mutate different genotypes or strains evolve

host

the individual that becomes infected by a pathogen

immune system

protects against most infectious agents can also remove abnormal cells and scavenge dead ones

external defenses

the surface of the body are the first line of defense (non-specific)

barrier defenses: the protective layers of tissue on those surfaces of the body that come in direct contact with the environment also include chemical environments

internal defense system

innate immune system: functions as the second line of defense (non-specific), features biochemical weapons and immune cells always ready

adaptive immune system

responds in a highly specific manner using specialized defense cells

immune memory that remembers a first encounter with a specific strain of pathogen and mobilizes a speedy and targeted response to a repeat infection by the same strain of pathogen

barrier defense

physical and chemical barriers on body surfaces that come into contact with the environment

internal defenses must distinguish self from nonself

sometimes a pathogen breaks through the external defense systems

must have a way of recognizing the invader as non-self

cell surface markers: designated as self by the immune system, all other proteins and carbohydrates are likely to be perceived as non-self

antibody mediated immunity

uses antipathogen protein complexes called antibodies made by white blood cells called B cells

cell mediated immunity

relies on white blood cells called T cells to attack invaders, body cells harboring invaders, and other abnormal cells in the body such as cancer cells

key immune cells of the innate and adaptive immune systems

allergies and autoimmune diseases

lymphatic system

a closed network of vessels

tissue pockets called lymph nodes

tissue patches

special organs that include the thymus and the spleen

lymph

fluid that circulates through the lymph vessels

lymphatic ducts

a network of tubes where defensive proteins, white blood cells, and interstital fluid are collected

will return fluid back to the circulatory system

lymph nodes

contain large numbers of white blood cells such as lymphocytes that trap bacteria, viruses, and foreign proteins

first line of defense

second line of defense

phagocytes

white blood cells

include macrophages and neutrophils destroy invading cellular organisms by engulfing their target in a process called phagocytosis

the engulfed pathogen is confined to a membrane enclosed compartment where it is chemically broken down or walled off from other cells by encapsulation

individual phagocytes die when they are full of pathogens

inflammation

cleans up the damaged tissues and prevents the entry or spread of a pathogen

direct injury or activation by chemical signals stimulates mast cells which release histamine and other alarm signals including cytokines

innate immune system is involved in blood clots

the innate immune system is also responsible for clotting the blood to close a wound

clotting reduces blood loss and restores the integrity of external defense barriers

platelets: sticky cells fragments that circulate in the blood an interlink with the clotting proteins to form a gel-like mesh that traps blood cells

innate immunity can trigger fever

cytokines trigger the release of prostaglandins to stimulate the hypothalamus and raise the body temperature resulting in a fever

moderate fever is beneficial because it: limits growth of many pathogens, enhances phagocytosis, speeds repair of damaged tissues