I. Sensory Systems

II. Skeletal MusclesA. Structure

B. Contraction

C. Nerve Input

III. Skeletal Systems

IV. Preparation for final

Lecture 15 – Ch.50: Muscular & SensoryLecture 15 – Ch.50: Muscular & Sensory

What is a Sensory Receptor?

Specialized cells that signals when stimulated

Receptors named after stimuli they respond to:

1) Thermoreceptors: Heat / Cold

2) Mechanoreceptors: Motion; pressure; gravity

3) Photoreceptors: Light (photons)

4) Chemoreceptors: airborne/waterborne molecules

5) Nociceptors: Pain (chemical release)

Sensory Input

Sound:Sensory Input

Sound waves are vibrations in fluid (air, water)

Sound: Ear: Sound Electrical Signal

1) Sound wave enters ear (auditory canal)

3) Vibration passes to middle ear bones

2) Tympanic membrane vibrates

Sensory Input

Outer ear Middle ear Inner ear

bones ofmiddle ear

auditorycanal

vestibular system(detects head

movementand gravity)

auditory nerveto brain

topharynx

tympanicmembrane

cochlea

auditory tube(Eustachian tube)

4) Inner ear (cochlea) converts vibrations to electrical signal

5

Sound:Sensory Input

5) Inside the cochlea, hair cells are between the basilar and tectorial membranes – vibrations cause the basilar membrane to vibrate, bending hairs against the tectorial membrane.

Two parts of sound are volume and pitch – which is detected by the basilar membrane?

1. Both volume and pitch

2. Volume only

3. Pitch only

4. Neither

Vision:Eye: Light Electrical Signal

Sensory Input

Some animals only sense light/darkMany arthropods have a compound eye, where many images are pieced together into a visual mosaic

Compound eyes

Vision:

Eye placement changes vision:• Forward-facing: many carnivores that need depth perception

• Widely spaced: herbivores - allows better predator detection

Sensory Input

Vision:Eye: Light Electrical Signal

Sensory Input

Mammals: collects & focuses light waves; transmits signal to brain

1) Light enters via cornea (transparent covering), through the pupil (opening in center of iris)

2) The iris is a pigmented ring of muscle that controls light entry

3) Light is focused on the retina (sheet of photoreceptors) by the lens (transparent surface)

Vision: Sensory Input

4) Muscles attached to lens contract to change the lens shape and focus image on the fovea for any visual distance

retina

Close object, lensfattens to focuson retina.

Distant object,lens thins tofocus on retina.

Vision: Sensory Input

Abnormally long eyeball: the image is focused in front of the retina: nearsightedness

Abnormally short eyeball: the image is focused behind the retina: farsightedness

Vision:Eye: Light Electrical Signal

Rods: Dim-light vision

(many but scattered)

Cones: Color vision

(Red/green/blue)

5) Light on the retina triggersreceptors; optic nerve excited

Sensory Input

fovea

blindspot

The blind spot is where the optic nerve connects to eyeball

No photoreceptors, so images disappear

Which animals would see better at night?

1. Those with more rods

2. Those with more cones

3. Those with larger irises

4. Those with longer eyeballs

Odor/Taste:

1) Chemicals enter nasal cavity;bind to receptors (olfactory epithelium)

2) Olfactory bulb (in brain) excited

Nose / Tongue: Chemical Electrical Signal

Sensory Input

olfactorydendrites

olfactoryepithelium

nasalcavity

air withodor molecules

olfactory structure of brain

bone

nasal cavity

olfactoryreceptors

mucus layer

Odor/Taste:

1) Dissolved chemicals enter taste buds on tongue (via taste pore)

2) Chemicals bind with receptors; stimulate nerves

• Five primary tastes:

• Sweet / Salt / Bitter / Sour / Umami

• Olfaction enhances taste

Nose / Tongue: Chemical Electrical Signal

Sensory Input

The human tongue

papillae

taste receptor cells

Taste bud

nerve fibersto brain

microvillitaste pore

Which is a correct statement about chemoreceptors?

1. Individual chemoreceptors detect specific tastes

2. Individual chemoreceptors detect specific odors

3. Individual chemoreceptors are specific to both taste and odor

4. Each chemoreceptor can detect more than one taste/odor

Pain is a specialized Chemical Sense:

1) Damaged cells spill chemicals

2) Nociceptors detecttissue damage

Sensory Input

18

Self-Check

Sensation Type(s) of receptor; Description of sense

Touch

Sound

Sight

Taste

Smell

Pain

Some senses are unfamiliar to humans

Other Senses:

Echolocation:

Animal emits pulse -interprets returning signal

Electrolocation:Animal

produceselectrical field;

interpret distortion

in field

Sensory Input

Magnetic Field

Detection:

Animals detect and

orient based on earth’s

magnetic field

Muscular and skeletal systems

Muscles power movement by contracting

Bones provide framework for muscles

Muscle Tissue (Muscle = “little mouse”):

• Exerts force by

contracting

Chemical energy (ATP) Mechanical EnergyTransformation

Muscles

Movement due to actin microfilaments and myosin strands

Slide past one another, change cell shape

connective tissuetendon (to bone)

Skeletal muscleMuscle fiber(muscle cell)

Myofibril(contains thin and thick filaments)

bundle ofmuscle cells

nerve andblood vessels

Skeletal Muscles

• Humans > 700 unique skeletal muscles

• Muscle connected to bones by tendons

Cross section of fiberm

uscl

e fib

er

T tubules

plasmamembrane

myofibril

sarcoplasmicreticulum

Skeletal Muscles

- Each muscle cell runs length of muscle

- Multinucleate

- Made up of myofibrils

Contractile cylinders of actin and myosin

- Each myofibril surrounded by sarcoplasmic reticulum

- Fluid with high calcium levels

- T-tubules in plasma membrane relay signals

Myofibril

myofibril

sarcomere

thick filamentthin filament

Z lines

Skeletal Muscles

Myofibrils of “thick” and “thin” filaments.

Each filament is made of protein strands.

Filaments arranged in sarcomeres

Separated by Z-lines of fibrous protein

Thick and thin filaments

tropomyosin

thin filament

thick filament(myosin)

myosin heads

accessoryproteins

troponin

actin

Skeletal Muscles

Thick filaments: made mostly of myosin, have small moveable “heads”

Thin filaments: primarily actin, have points to which the myosin heads temporarily attach

binding sites

thick filament

thin filament

ATP

ADP

myosin head

Skeletal Muscles

Each actin subunit has binding site for myosin head

Contraction exposes binding sites, allowing filaments to bind to one another

Myosin heads then repeatedly bend, pull, release, and reattach (using ATP-energy)

Sliding filaments shorten each sarcomere

Skeletal Muscles

Neuromuscular junctions between axons and fibers

All or nothing response:

Skeletal muscle excited

All sarcomeres respond

Skeletal Muscles

postsynapticmembrane

axon of motor neuronsynaptic terminal

synaptic vesicles

Strength of Muscle Contraction # of Fibers Stimulated

Motor Unit: A single motor neuron and all the muscle fibers innervated by it

Skeletal Muscles

How do you strengthen a muscle contraction?

1. Engage more muscle fibers

2. Contract each sarcomere further

3. Contract more sarcomeres in a muscle fiber

4. Activate additional myofibrils

Action potential travels through T-channels and opens Ca++ channels in sarcoplasmic reticulum

These ions allow binding of thin and thick fibers

Ca++ is pumped back out after action potential ends

Unless you’re dead

Skeletal Muscles

You cannot add muscle fibers

You can add more myofibrils

Skeletal Muscles

muscle

Muscle fiber(muscle cell)

Myofibril

bundle ofmuscle cells

Hydrostatic skeleton

Fluid provides support

Muscles contract and move fluid

Skeletal System

Exoskeleton

Hard shells cover outside of body

Muscles contract and move frame at joints

Skeletal System

Endoskeleton

Internal framework - least common skeleton type

Muscles contract and move frame at joints

Skeletal System

Movement of bones

Joints are where two bones meetLubricated by cartilage

Attached by ligaments

Muscles are attached to bone on either side of the jointAttached by tendons

LigamentsOrigin - attachment to still bone

Insertion - attachment to moving bone

Vertebrate Skeletons

Things To Do After Lecture 15…Reading and Preparation:

1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms.

2. Ch. 50 Self-Quiz: #2, 3, 4 (correct answers in back of book)

3. Read chapter 50, focus on material covered in lecture (terms, concepts, and figures!)

4. Prepare for final exam!!!

“HOMEWORK” (NOT COLLECTED – but things to think about for studying):

1. Describe the types of sensory information processed by humans – which receptors are responsible for each type?

2. What is the problem in the eye of someone who is near-sighted versus someone who is far-sighted? How do corrective lens fix the problem?

3. Explain how a muscle contracts – include the units down to the sarcomere and their place in a muscle fiber.