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Muscles, Locomotion & Sensation (Ch. 50). Overview of information processing by nervous systems. Sensory input. Integration. Sensor. Motor output. Effector. Peripheral nervous system (PNS). Central nervous system (CNS). Animal Locomotion. What are the advantages of locomotion?.

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slide1

Muscles, Locomotion

& Sensation

(Ch. 50)

overview of information processing by nervous systems
Overview of information processing by nervous systems

Sensory input

Integration

Sensor

Motor output

Effector

Peripheral nervoussystem (PNS)

Central nervoussystem (CNS)

animal locomotion
Animal Locomotion

What are the advantages of locomotion?

sessile

motile

lots of ways to get around1
Lots of ways to get around…

mollusk

mammal

bird

reptile

lots of ways to get around2
Lots of ways to get around…

bird

arthropod

mammal

bird

muscle
Muscle

involuntary, striatedauto-rhythmic

voluntary, striated

heart

moves bone

multi-nucleated

involuntary, non-striated

digestive systemarteries, veins

evolved first

slide8
All cells have a fine network of actin and myosin fibers that contribute to cellular movement. But only muscle cells have them in such great abundance and far more organized for contraction.
  • SMOOTH MUSCLESmooth muscle was the first to evolve. Lining of blood vessels, wall of the gut, iris of the eye.Some contract only when stimulated by nerve impulse. Others generate electrical impulses spontaneously and then are regulated by nervous system.
  • CARDIAC MUSCLESmall interconnected cell with only one nucleus. Interconnected through gap junctions. Single functioning unit that contract in unison via this intercellular communication. Mostly generate electrical impulses spontaneously. Regulated rather than initial stimulation by nervous system.
  • SKELETAL MUSCLEFusion of many cells so multi-nucleated. Attached by tendon to bone. Long thin cells called muscle fibers.
organization of skeletal muscle
Organization of Skeletal muscle

skeletal muscle

plasma

membrane

nuclei

tendon

muscle fiber (cell)

myofibrils

myofilaments

muscles movement
Muscles movement
  • Muscles do work by contracting
    • skeletal muscles come in antagonistic pairs
      • flexor vs. extensor
    • contracting = shortening
      • move skeletal parts
    • tendons
      • connect bone to muscle
    • ligaments
      • connect bone to bone
structure of striated skeletal muscle
Structure of striated skeletal muscle
  • Muscle Fiber
    • muscle cell
      • divided into sections = sarcomeres
  • Sarcomere
    • functional unit of muscle contraction
    • alternating bands of thin (actin) & thick (myosin) protein filaments
muscle filaments sarcomere
Muscle filaments & Sarcomere
  • Interacting proteins
    • thin filaments
      • braided strands
        • actin
        • tropomyosin
        • troponin
    • thick filaments
      • myosin
thin filaments actin
Thin filaments: actin
  • Complex of proteins
    • braid of actin molecules & tropomyosinfibers
      • tropomyosin fibers secured with troponin molecules
thick filaments myosin
Thick filaments: myosin
  • Single protein
    • myosin molecule
      • long protein with globular head

bundle of myosin proteins:

globular heads aligned

thick thin filaments
Thick & thin filaments
  • Myosin tails aligned together & heads pointed away from center of sarcomere
interaction of thick thin filaments
Interaction of thick & thin filaments

sarcomere

sarcomere

  • Cross bridges
    • connections formed between myosin heads (thick filaments) & actin (thin filaments)
    • cause the muscle to shorten (contract)
where is atp needed
Where is ATP needed?

formcrossbridge

releasecrossbridge

shortensarcomere

binding site

CleavingATP ADP allows myosin head to bind to actin filament

thin filament(actin)

myosin head

ADP

thick filament(myosin)

1

2

ATP

So that’s where those10,000,000 ATPs go!

Well, not all of it!

1

1

3

1

1

4

closer look at muscle cell
Closer look at muscle cell

Sarcoplasmicreticulum

Transverse tubules(T-tubules)

Mitochondrion

multi-nucleated

muscle cell organelles
Muscle cell organelles

Ca2+ ATPase of SR

  • Sarcoplasm
    • muscle cell cytoplasm
    • contains many mitochondria
  • Sarcoplasmic reticulum (SR)
    • organelle similar to ER
      • network of tubes
    • stores Ca2+
      • Ca2+ released from SR through channels
      • Ca2+ restored to SR by Ca2+ pumps
        • pump Ca2+ from cytosol
        • pumps use ATP

There’sthe restof theATPs!

But whatdoes theCa2+ do?

ATP

muscle at rest
Muscle at rest
  • Interacting proteins
    • at rest, troponin molecules hold tropomyosin fibers so that they cover the myosin-binding sites on actin
      • troponin has Ca2+ binding sites
the trigger motor neurons
The Trigger: motor neurons
  • Motor neuron triggers muscle contraction
    • release acetylcholine (Ach) neurotransmitter
nerve trigger of muscle action
Nerve trigger of muscle action
  • Nerve signal travels down T-tubule
    • stimulates sarcoplasmic reticulum (SR) of muscle cell to release stored Ca2+
    • flooding muscle fibers with Ca2+
ca 2 triggers muscle action
Ca2+ triggers muscle action
  • At rest, tropomyosin blocks myosin-binding sites on actin
    • secured by troponin
  • Ca2+ binds to troponin
    • shape changecauses movement of troponin
    • releasing tropomyosin
    • exposes myosin-binding sites on actin
how ca 2 controls muscle
How Ca2+ controls muscle
  • Sliding filament model
    • exposed actin binds to myosin
    • fibers slide past each other
      • ratchet system
    • shorten muscle cell
      • muscle contraction
    • muscle doesn’t relax until Ca2+ is pumped back into SR
      • requires ATP

ATP

ATP

how it all works
How it all works…
  • Action potential causes Ca2+ release from SR
    • Ca2+ binds to troponin
  • Troponin moves tropomyosin uncovering myosin binding site on actin
  • Myosin binds actin
    • uses ATP to "ratchet" each time
    • releases, "unratchets" & binds to next actin
  • Myosin pulls actin chain along
  • Sarcomere shortens
    • Z discs move closer together
  • Whole fiber shortens  contraction!
  • Ca2+ pumps restore Ca2+ to SR relaxation!
    • pumps use ATP

ATP

ATP

fast twitch slow twitch muscles
Fast twitch & slow twitch muscles
  • Slow twitch muscle fibers
    • contract slowly, but keep going for a long time
      • more mitochondria for aerobic respiration
      • less SR  Ca2+ remains in cytosol longer
    • long distance runner
    • “dark” meat = more blood vessels
  • Fast twitch muscle fibers
    • contract quickly, but get tired rapidly
      • store more glycogen for anaerobic respiration
    • sprinter
    • “white” meat
muscle limits
Muscle limits
  • Muscle fatigue
    • lack of sugar
      • lack of ATP to restore Ca2+ gradient
    • low O2
      • lactic acid drops pH which interferes with protein function
    • synaptic fatigue
      • loss of acetylcholine
  • Muscle cramps
    • build up of lactic acid
    • ATP depletion
    • ion imbalance
      • massage or stretching increases circulation
diseases of muscle tissue
Diseases of Muscle tissue
  • ALS
    • amyotrophic lateral sclerosis
    • Lou Gehrig’s disease
    • motor neurons degenerate
  • Myasthenia gravis
    • auto-immune
    • antibodies to acetylcholine receptors

Stephen Hawking

botox
Botox
  • Bacteria Clostridiumbotulinum toxin
    • blocks release of acetylcholine
    • botulism can be fatal

muscle

rigor mortis
Rigor mortis
  • So why are dead people “stiffs”?
    • no life, no breathing
    • no breathing, no O2
    • no O2, no aerobic respiration
    • no aerobic respiration, no ATP
    • no ATP, no Ca2+ pumps
    • Ca2+ stays in muscle cytoplasm
    • muscle fibers continually contract
      • tetany or rigor mortis
    • eventually tissues breakdown& relax
      • measure of time of death
overview of information processing by nervous systems1
Overview of information processing by nervous systems

Sensory input

Integration

Sensor

Motor output

Effector

Peripheral nervoussystem (PNS)

Central nervoussystem (CNS)

sensory reception two mechanisms
Sensory reception: two mechanisms

Strongmuscle stretch

Weakmuscle stretch

Muscle

Dendrites

–50

Receptor potential

–50

–70

–70

Stretchreceptor

Membranepotential (mV)

Action potentials

0

0

Axon

–70

–70

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

0

Time (sec)

Time (sec)

(a) Crayfish stretch receptors have dendrites embedded in abdominal muscles. When the abdomen bends, muscles and dendrites

stretch, producing a receptor potential in the stretch receptor. The receptor potential triggers action potentials in the axon of the stretch

receptor. A stronger stretch produces a larger receptor potential and higher frequency of action potentials.

No fluidmovement

Fluid moving inone direction

Fluid moving in other direction

“Hairs” ofhair cell

Moreneuro-trans-mitter

Lessneuro-trans-mitter

Neuro-trans-mitter at synapse

Receptor potential

–50

–50

–50

Axon

–70

–70

–70

Membranepotential (mV)

Membranepotential (mV)

Action potentials

Membranepotential (mV)

0

0

0

–70

–70

–70

0

1

2

3

4

5

6

7

1

2

3

4

5

6

7

1

2

3

4

5

6

7

0

0

Time (sec)

Time (sec)

Time (sec)

(b) Vertebrate hair cells have specialized cilia or microvilli (“hairs”) that bend when sur-rounding fluid moves. Each hair cell releases an excitatory neurotransmitter at a synapse

with a sensory neuron, which conducts action potentials to the CNS. Bending in one direction depolarizes the hair cell, causing it to release more neurotransmitter and increasing frequency

of action potentials in the sensory neuron. Bending in the other direction has the opposite effects. Thus, hair cells respond to the direction of motion as well as to its strength and speed.

sensory receptors in human skin
Sensory receptors in human skin

Cold

Light touch

Pain

Hair

Heat

Epidermis

Dermis

Nerve

Hair movement

Strong pressure

Connective tissue

the structure of the human ear
The Structure of the Human Ear

1

2

Overview of ear structure

The middle ear and inner ear

Incus

Semicircularcanals

Skullbones

Stapes

Middleear

Outer ear

Inner ear

Malleus

Auditory nerve,to brain

Pinna

Tympanicmembrane

Cochlea

Eustachian tube

Auditory canal

Ovalwindow

Eustachian tube

Tympanicmembrane

Tectorialmembrane

Hair cells

Roundwindow

Cochlear duct

Bone

Vestibular canal

Auditory nerve

Axons of sensory neurons

Basilarmembrane

To auditorynerve

Tympanic canal

Organ of Corti

4

3

The organ of Corti

The cochlea

transduction in the cochlea
Transduction in the cochlea

Cochlea

Stapes

Axons ofsensoryneurons

Oval window

Vestibularcanal

Perilymph

Apex

Base

Roundwindow

Tympaniccanal

Basilar membrane

how the cochlea distinguishes pitch
How the cochlea distinguishes pitch

Cochlea(uncoiled)

Apex(wide and flexible)

Basilarmembrane

500 Hz(low pitch)

1 kHz

2 kHz

4 kHz

8 kHz

16 kHz(high pitch)

Frequency producing maximum vibration

Base(narrow and stiff)

organs of equilibrium in the inner ear
Organs of equilibrium in the inner ear

Each canal has at its base a swelling called an ampulla, containing a cluster of hair cells.

The semicircular canals, arranged in three spatial planes, detect angular movements of the head.

When the head changes its rateof rotation, inertia prevents endolymph in the semicircular canals from moving with the head, so the endolymph presses against the cupula, bending the hairs.

Flowof endolymph

Flowof endolymph

Vestibular nerve

Cupula

Hairs

Haircell

Nervefibers

Vestibule

Utricle

Body movement

Saccule

The hairs of the hair cells project into a gelatinous cap called the cupula.

The utricle and saccule tell the brain which way is up and inform it of the body’s position or linear acceleration.

Bending of the hairs increases the frequency of action potentials in sensory neurons in direct proportion to the amount of rotational acceleration.

structure of the vertebrate eye
Structure of the vertebrate eye

Sclera

Choroid

Retina

Ciliary body

Fovea (centerof visual field)

Suspensoryligament

Cornea

Iris

Opticnerve

Pupil

Aqueoushumor

Lens

Vitreous humor

Central artery and

vein of the retina

Optic disk(blind spot)

focusing in the mammalian eye
Focusing in the mammalian eye

Front view of lensand ciliary muscle

Ciliary muscles contract, pulling border of choroid toward lens

Lens (rounder)

Choroid

Retina

Suspensory ligaments relax

Ciliarymuscle

Lens becomes thicker and rounder, focusing on near objects

Suspensoryligaments

(a) Near vision (accommodation)

Ciliary muscles relax, and border of choroid moves away from lens

Lens (flatter)

Suspensory ligaments pull against lens

Lens becomes flatter, focusing on distant objects

(b) Distance vision

cellular organization of the vertebrate retina
Cellular organization of the vertebrate retina

Retina

Optic nerve

Tobrain

Retina

Photoreceptors

Neurons

Rod

Cone

Amacrinecell

Horizontalcell

Opticnervefibers

Ganglioncell

Bipolarcell

Pigmentedepithelium

rod structure and light absorption
Rod structure and light absorption

Rod

Outersegment

H

H

O

C

H

CH3

C

C

H3C

H

CH3

C

H2C

C

H

H

H2C

C

C

C

C

Disks

C

C

C

C

H

H

H

CH3

CH3

cis isomer

Insideof disk

Cell body

Enzymes

Light

Synapticterminal

H

H

CH3

C

CH3

H

H

H2C

C

H

H

H2C

C

C

C

C

C

O

C

C

C

C

C

C

H

CH3

CH3

H

CH3

CH3

Cytosol

trans isomer

Retinal

Rhodopsin

Opsin

(b) Retinal exists as two isomers. Absorption of light converts the cis isomer to the trans isomer, which causes opsin to change its conformation (shape). After a few minutes, retinal detaches from opsin. In the dark, enzymes convert retinal back to its cis form, which recombines with opsin to form rhodopsin.

(a) Rods contain the visual pigment rhodopsin, which is embedded in a stack of membranous disks in the rod’s outer segment. Rhodopsin consists of the light-absorbing molecule retinal bonded to opsin, a protein. Opsin has seven  helices that span the disk membrane.

neural pathways for vision
Neural pathways for vision

Right

visual

field

Left

visual

field

Left

eye

Right

eye

Optic nerve

Optic chiasm

Lateralgeniculatenucleus

Primaryvisual cortex

smell in humans
Smell in humans

Brain

Action potentials

Odorant

Olfactory bulb

Nasal cavity

Bone

Epithelial cell

Odorantreceptors

Chemoreceptor

Plasmamembrane

Cilia

Odorant

Mucus

sensory transduction by a sweetness receptor
Sensory transduction by a sweetness receptor

Taste pore

Sugar molecule

Taste bud

Sensoryreceptorcells

Sensoryneuron

Tongue

1 A sugar molecule binds to a receptor protein on the sensory receptor cell.

Sugar

Adenylyl cyclase

G protein

Sugarreceptor

2Binding initiates a signal transduction pathway involving cyclic AMP and protein kinase A.

ATP

cAMP

3Activated protein kinase A closes K+ channels in the membrane.

Proteinkinase A

SENSORYRECEPTORCELL

4 The decrease in the membrane’s permeability to K+ depolarizes the membrane.

K+

Synapticvesicle

5 Depolarization opens voltage-gated calcium ion (Ca2+) channels, and Ca2+ diffuses into the receptor cell.

—Ca2+

6 The increased Ca2+ concentration causes synaptic vesicles to release neurotransmitter.

Neurotransmitter

Sensory neuron

specialized electromagnetic receptors
Specialized electromagnetic receptors

Eye

Infraredreceptor

(a) This rattlesnake and other pit vipers have a pair of infrared receptors,one between each eye and nostril. The organs are sensitive enoughto detect the infrared radiation emitted by a warm mouse a meter away. The snake moves its head from side to side until the radiation is detected equally by the two receptors, indicating that the mouse is straight ahead.

(b) Some migrating animals, such as these beluga whales, apparentlysense Earth’s magnetic field and use the information, along with other cues, for orientation.

the lateral line system in a fish
The lateral line system in a fish

Lateralline

Opening of lateralline canal

Lateral line canal

Scale

Epidermis

Neuromast

Lateral nerve

Segmental muscles of body wall

Cupula

Sensoryhairs

Supportingcell

Hair cell

Nerve fiber

slide53

Make sure you can do the following:

  • Label all parts of a striated motor unit and explain how those structure contribute to the function of the motor unit.
  • Explain the sliding filament model of muscle contraction
  • Compare and contrast the major sensory apparatus used by mammals and other animals
  • Explain the causes of sensory and motor system disruptions and how disruptions of the sensory and motor systems can lead to disruptions of homeostasis.