Campbell Biology Chapt 50 Part I

Front 1

Sensory process begins with a stimuli

Back 1

Stimuli is forms of energy

A sensory receptors converts stimulus energy into a change in membrane potential

When input to nervous system is received and processed, a motor response is generated

Front 2

sensory pathways have 4 basic common functions

Back 2

1. Sensory reception

2. Transduction

3. Transmission

4. Perception

Front 3

Sensory reception

Back 3

Detection of stim by sensory receptors on sensory cells

Front 4

Sensory receptors

Back 4

Sensory cells are specialized neurons, epithelial cells, or sensory organs (eyes,ears) that interact directly with stim

Interact both inside (blood pressure, body position) and out (heat, light, pressure)

Open or close ion channels

Front 5

Sensory transduction

Back 5

Conversion of stimulus energy into a change in the membrane potential of a sensory receptor

Change in membrane potential is receptor potential (graded potentials who magnitude varies pending strength of stim)

Front 6

Transmission

Back 6

Sensory info travels through nervous system as action potentials

Sensory receptors can be neurons or non-neuronal receptors

Non-neuronal receptors involve chemical synapses with afferent neurons

Front 7

Size of receptor increases with intensity of stim and varies pending neuron vs non-neuronal

Back 7

Neuron receptor: larger receptor potential results in more frequent action potentials

Non-neuronal receptor: larger receptor potential causes more NTs to be released

Front 8

Perception

Back 8

Brains construction of stimuli(colors, sound, taste)

Stim from different receptors travel as action potentials along dedicated neural pathways

Brain distinguishes stim from different receptors based on the path by which the action potential arrives as well as area of brain (smell, color, sound)

Front 9

Amplification

Back 9

Strengthening of a sensory signal during transduction

Enzyme catalyzed reactions

Also takes place in accessory structures (like ear 3 small bones enhances pressure assoc. with sound waves more than 20 fold)

Front 10

Sensory adaptation

Back 10

Decrease in responsiveness to continued stim

Front 11

5 types of sensory receptors

Back 11

1. Mechano

2. Chemo

3. Electromagnetic

4. Thermo

5. Pain

Front 12

Mechanoreceptors

Back 12

Sense physical deformation caused by forms of mechanical energy such as pressure, touch, stretch, motion, and sound

Consist of ion channels linked to external structures (hair, cilia) and internal (cytoskeleton)

Dendrites of sensory neurons

Bending/stretching of external structures generates tension that alters the permeability of ion channels producing depolarization

Front 13

Chemoreceptors

Back 13

Transmit info about total solute concentration of a solution-osmoreceptors

Respond to individual kinds of molecules-glucose, amino acids, oxygen, CO2

When stim molecule binds, becomes more or less permeable to ions

Antenna of male silk worm moth sensitive to pheromones (chemoreceptors)

Front 14

Electroreceptors

Back 14

Detect electromagnetic energy such as light, energy, and magnetism

Many animals use earths magnetic field to orient themselves through iron to migrate

Front 15

Thermoreceptors

Back 15

Detect heat and old and help regulate body temp

Snakes have them

Cayenne peppers contain capsaicin and receptors that respond to this open calcium channels and also respond to high temperatures

Variety of thermoreceptors (each specific for a particular temp range which is transient receptor potential TRP)

TRP specific to lower temps respond to menthol

Front 16

Pain or nociceptors

Back 16

Reflect harmful conditions like naked dendrites in epidermis which leads to defensive action

Respond to excess heat, pressure, or chemicals released from damaged or inflamed tissues

Chemicals produced in body can enhance perception of pain (prostaglandins lower pain threshold sensitizing pain receptors )

Front 17

Thin vs thick filaments

Back 17

Thin: composed of actin

Thick: composed of myosin

Front 18

Skeletal muscle

Back 18

Moves bones and body

Characterized by hierarchy of smaller and smaller units

Consist of bundles of long fibers, each fiber (single cell with multiple nuclei) running parallel to the length of muscle

Front 19

Muscle fiber

Back 19

Bundle of smaller myofibrils arranged longitudinal

Contain unique arrangements of myofilaments in units (scaromeres)

Front 20

Sacromeres

Back 20

Myofilaments arranged in units that make up myofibrils which, arranged in bundles, make up muscle fibers

Functional unit of a muscle

Bordered by z lines where thin filaments attach

Front 21

Skeletal muscle is also called

Back 21

Striated muscle

Has regular arrangements of myofilaments creates a pattern of light and dark bands

Microfilament move and bring about contraction

Front 22

Thick myofilments

Back 22

Only myosin

Each myosin molecule is shaped like a golf club

Straight portion ending in a double globular head or cross bridge

Cross-bridges occur on each side of a sarcomere but not in the middle

Front 23

Thin myofilaments

Back 23

Consisting of two intertwining actin filaments

Tropomyosin and Troponin are assoc. regulatory proteins

Front 24

Sliding-filament model

Back 24

Thin and thick filaments ratchet past each other longitudinally powered by the myosin molecules

Neither thin not thick change in length when sacromere shortens

Instead slide past each other increasing their overlap

Front 25

Step 1, 2, 3 of myosin actin sliding

Back 25

Myosin molecules have head and tail regions. Tails form thick filament and head binds atp

1. Myosin head is bound to ATP. Is in low energy configuration

2. Myosin head hydrolyzes ATP to ADP and Pi, converts to high energy form

3. Head binds to actin forming a cross-bridge with thin filament

Front 26

Steps 3-5 for myosin actin sliding

Back 26

4. Myosin a binding slides actin along, returning myosin head to low energy state

This filament moves toward center of sacromere

5. Binding of new molecule of ATP releases myosin head and a new cycle begins

Front 27

Muscle contraction requires repeated cycles of binding and releasing

Back 27

In each cycle, myosin head freed from cross bridge cleaves newly bound atp and begins again

Myosin attaches to new binding site on thin filament since it has moved toward center

300 heads of thick filament form and reform about 5 cross-bridges per second moving actin filaments

Front 28

Glycolysis and aerobic respiration generate ATP

Back 28

Muscle at rest-only enough atp fit a few contractions

To power repetitive contractions, relies on creatine phosphate and glycogen

Front 29

Creatine phosphate

Back 29

Transfer of phosphate group from creatine phosphate to ADP in an enzyme cataloged reaction synthesizes additional ATP

Resting supply of creatine phosphate can sustain contractions for about 15 seconds

Front 30

Glycogen break down

Back 30

ATP is restored when glycogen is broken down to glucose by either aerobics respiration or glycolysis

Aerobic respiration can sustain contraction for about one hour

During intense muscle activity, oxygen becomes limiting and ATP is generated instead by lactic acid fermentation (less activity per glucose than glycolysis; sustains about 1 minute)

Front 31

Troponin complex and tropomyosin

Back 31

Regulatory proteins that bind to actin when a muscle fiber is at rest

Covers myosin bindings sites and prevents interaction of actin and myosin

Troponin complex is like a mail holding tropomyosin in place

Front 32

For muscle fiber to contract...

Back 32

Muscle contraction occurs when Ca concentration is high and stops when Ca concentration is low

Calcium in cytosol binds to Troponin complex causing proteins to shift position, exposing myosin sites

Relaxation occurs when nerve impulses stop And Ca is actively transported into the sacroplasmic reticulum

Front 33

Stimulus leading to contraction is an action potential in a motor neuron that makes a synapse with a muscle fiber

Back 33

1. Motor neuron release Ach, which binds to receptors on muscle fiber causing muscle to produce action potential

2. AP travels along T tubules in sarcoplasmic reticulum (SR), opening Ca channels in SR

3. Ca ions stored in SR flow into cytosol and (4) bind to Troponin complex on actin filaments

5. Binding exposes myosin binding sites and allows cross-bridge (contraction)

6. Motor neuron input stops, muscle cells relax (transport proteins pump Ca back into SR

7. Due to low Ca levels, regulatory proteins bind to thin filaments and shift back to starting position.

Front 34

Muscle fiber

Back 34

A muscle cell with typical cellular components

Front 35

Another pic of muscle fiber

Back 35

A

Front 36

Acetylcholinesterase (AChE)

Back 36

Enzyme that breaks down NT acetylcholine at synapse

Breaks it down into acetic acid and choline which are recycled to make new NT

Stops signal

AChE has one of the fastest reaction rates of any of our enzymes, breaking up each molecule in about 80 microseconds

Front 37

Botox and tetanus

Back 37

Botox prevents release of ACh from motor axon terminals, inhibits muscle contraction (reduces overactive bladder, reduces sweat gland production, prevents wrinkles)

Tetanus: inhibits AChE so constant presence of ACh, excessive muscle contraction which can be fatal

Front 38

Amyotrophic lateral sclerosis (ALS)

Back 38

Lou Greg’s disease

Involve neurons responsible for voluntary muscle movement

Degeneration of neurons leads to atrophy of muscles and death

Front 39

Myasenthia gravis

Back 39

Autoimmune disease

Attacks acetylcholine receptors on muscle fibers

Treatments exist

Front 40

Twitch

Back 40

A single contraction

Results from a single action potential in a motor neuron

A series of action potentials is necessary to produce more sustained contraction

Front 41

2 mechanisms by which nervous system produces graded contractions

Back 41

1. Varying number of fibers that contract

2. Varying rate at which fibers are stimulated

Contraction of a whole muscle is graded, the extent and strength of its contraction can be voluntarily altered

Front 42

Motor unit

Back 42

Consist of a single motor neuron and all the muscle fibers it controls

All muscle fibers in unit contract when motor neuron produces action potential

Strength depends how many muscle fibers the motor neuron controls (few to hundreds)

Nervous system can choose large or small unit to contract

Front 43

Recruitment

Back 43

Process by which more and more motor neurons are activated

As recruitment proceeds, the force developed by a muscle increases

More rapid delivered action potential produce a graded contraction through summation

Front 44

Recruitment of multiple motor neurons results in stronger contractions

Back 44

A single potential will produce a twitch lasting for 100 ms

If second action potential arrive before relaxation, the twitches sum increasing tension

Further summation occurs as the rate of stimulation increases

Front 45

Muscle tension

Back 45

Condition which muscles of the body remain semi-contracted for an extended period

Tetanus: muscles cannot relax btw stimuli, creates tension in bones by stretching connective tissues btw bone and muscle