Unit 9 Response Mechanisms

different types of muscles found in vertebrates

skeletal, cardiac, and smooth

skeletal muscle

found throughout the body, striated, and responsible for voluntary movements allows muscles to contract and relax

cardiac muscle

found in the heart, striated, intercalated discs (electrical signals), responsible for involuntary contraction and relaxation

smooth muscle

found in hollow organs such as bladder, digestive system and blood vessels. not striated. responsible for involuntary expansion of muscles

hierarchal structure of skeletal muscle from largest to smallest

muscle, muscle fibers, single muscle fiber, myofibril, sarcomere

proteins involved in the contraction of skeletal muscle

tropomyosin and troponin complex

tropomyosin

blocks the myosin-binding sites on actin molecules

troponin complex

controls the position of tropomyosin on the thin filament

interaction of calcium with tropomyosin and troponin during contraction

bind to troponin, causing a change in shape, which moves tropomyosin away from binding sites

interaction of ATP with tropomyosin and troponin during contraction

binds to myosin heads and breaks into ADP and P, this energy released from ATP moves the head into a high energy state. Pulling the actin filament, causing the muscle to contract.

sequence of events associated with the sliding filament theory of muscle contraction

signal arrival, ion release, calcium binding, tropomyosin movement, cross-bridge formation, power stroke, detachment, reseting, and relaxation

signal arrival (sliding filament theory)

a nerve impulse reaches the muscle cell

ion release (sliding filament theory)

the release of calcium ions from the sarcoplasmic reticulum

calcium binding (sliding filament theory)

Calcium ions bind to troponin, causing a change in its shape.

tropomyosin movement (sliding filament theory)

shape change moves tropomyosin away from the binding sites on actin filaments

cross-bridge formation (sliding filament theory)

myosin heads attach to the exposed binding sites on actin, forming cross-bridges

power stroke (sliding filament theory)

energy from ATP, the myosin heads pivot, pulling the actin filaments toward the center of the sarcomere

detachment (sliding filament theory)

ATP molecule binds to the myosin head, causing it to detach from the actin

resetting (sliding filament theory)

myosin head resets to its original position

relaxation (sliding filament theory)

nerve impulse stops, calcium ions are pumped back into the sarcoplasmic reticulum, tropomyosin covers the binding sites on actin again, and the muscle relaxes

sliding filament theory

motor unit

a single motor neuron and all the muscle fibers it controls

how are motor units recruited

depending on the task needed to do, the nervous system controls which motor units are activated and the rate of muscle fiber stimulation

motor units for fine motor skills

precise small movements, less motor units innervated

motor units for gross motor skills

large, powerful movements, more motor units innervated

innervation ratio

number of muscle fibers supplied with neurons by a single motor neuron

antagonistic muscle pairs

muscles that work together in opposite directions (one muscle contracting, and one relaxing)

flexion

decreasing the angle between two body parts

extension

increasing the angle between two body parts

photoreceptors in plants that control their mediate response to light

blue light: phototropins and cryptochromes

red and far-red: phytochromes

blue light receptors

cryptochromes and phototropins

cryptochromes

photomorphogenesis, set circadian clock, seedling flower, stimulate cell expansion in cotyledons and leaves

phototropins

phototropism (growth in response to light)

phototropism

lets plants re-orient shoots in response to light (growing towards light)

photomorphogenesis

allows plants to change shape/grow in response to light

phytochrome signaling

protein that activate a plant, in red and far red light, controlling when plants flower or germinate

plant responses mediated by phytochromes

seed germination, de-elonagtion, shade avoidance, circadian clocks, flowering times

phytochrome signaling affects seed germination

seeds germinate during red light (active form), but not far-red light (inactive form)

photoperiodism

plants physical response to the length of day or night (light periods)

short day plant

(long night plant) flowers when days are shorter than nights and the light period is shorter than critical length,

long day plant

(short night plant) flowers when days are longer than nights and the light period is longer than critical length

phytochrome signaling responsible for shade avoidance

chlorophyll pigments absorb more red-light and allows far-red to pass through

gravitropism

growth response of plants to gravity

gravitropism in roots and shoots

as soon as seed germinates, it ensures that the roots grow into the soil and the shoots grow towards sunlight

thigmotropism

a directional growth of a plant in response to touch or a solid object

thigmomorphogenesis

changes in the morphology (form) of plant resulting from mechanical disturbances. ex. trees growing in windy conditions are shorter and have thicker trunks

nastic movements

non-directional responses to stimuli

photonasty

movement in response to light

thigmonasty

movement in response to touch or mechanical stimulation

thermonasty

movemnet in response to changes in temperature