Sunday, April 26, 2009

The End (of Chapter 50)

Alright girls, here are the final notes!

Chemoreception – Taste and Smell
Taste buds are modified epithelial cells situated on different parts of the tongue and mouth

Movement and Locomotion

Locomotion is the movement from place to place.
Hydrostatic skeletons consist of fluid held under pressure in a closed body compartment
Exoskeletons are hard encasements on the surface of an animal, such as is found in the grasshopper. Endoskeletons consist of hard supporting elements buried within the soft tissues of an animals. Ex: the human body skeleton

Skeletal muscles are attached to bones and responsible for the movement of bones they consist of long fibers, each of which is a single muscle cell. A muscle fiber is a bundle of myofibrils which are composed of myofilaments called actin (thin filaments) and myosin (thick filaments).
The sarcomere is the basic contractile unit of the muscle. Z lines make up the border of the sarcomere. The I band is the area near the end of the sarcomere where only thin filaments exists. The A band is the entire length of the thick filaments.
Muscle contraction occurs when the length of the sarcomere is reduced.
There are two different types of muscle fibers: fast-twitch muscle fibers, which are used for fast, powerful contractions and slow-twitch muscle fibers, which are used for slow, long-lasting contractions
The sliding filament model states that the thick and thin filaments slide past each other so that their degree of overlap increases. This is dependent on the interaction between the actin and myosin molecules that make up the thin and thick filaments
Muscle cells contract when stimulated by a motor neuron.
In the first stage of muscle contraction, muscle contraction is stimulated by an action potential in a motor neuron that makes as synaptic connection with the muscle cell releases acetylcholine at the neuromuscular junction. This depolarizes the muscle cell and triggers the action potential.
In the second stage of muscle contraction, the action potential spreads along T tubules (transverse tubules); changes the permeability of the sarcoplasmic reticulum to calcium ions, and the newly released calcium ions bind to troponin and cause it to move, exposing the myosin sites on the actin; the muscle contracts.

The End

Review Questions:
1. All of the following are involved in the contraction of muscle cells EXCEPT:
a) actin
b) cAMP
c) mysoin
d) tropomyosin
e) troponin

2. Muscle cells are stimulated by neurotransmitters released from the tips of
A) T tubules
B) motor cell axons
C) motor cell dendrites
D) sensory cell dendrites
E) sensory cell axons

3. Which of the following does not form part of the thin filaments of a muscle cell?
a) tropomyosin
b) calcium-binding site
c) troponin
d) myosin
e) actin

1. b
2. b
3. d

Don't forget that the chapter 49 and 50 take home quiz is due on Friday!

We only have two weeks left until the AP Exam so it's time to start reviewing. . . Remember, about 25% of the exam will be on Molecular and Cellular Biology (Chemistry of Life, Cells, Cellular Energy), about 25% will be on Genetics and Evolution (Heredity, Molecular Genetics, Evolutionary Biology) and about 50% will be on Organisms and Populations (Structure and Function of Plants and Animals, Ecology, Taxonomy of Organisms).

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