chapter 6

Question 1

3 types of muscles + their properties + where they can be found in the body

Answer 1

*smooth muscles:
-surround internal organ’s
-involuntary

*cardiac muscles:
-found in the heart
-involuntary

*skeletal muscles:
-found everywhere
-attached to bones
-voluntary
-aka “striated”

Question 2

3 types of muscle contraction

Answer 2

*concentric:
-shortening
-ex. the hamstrings during quad contraction

*eccentric
-lengthening
-ex. the quads during quad contraction

*isometric
-static
-ex. plank, pushing a desk down

Question 3

5 parts of reflex arc

Answer 3

1) the receptor (receives initial signal)
2) the afferent neuron (carries impulse to spinal column/brain) (away from stimulus)
3) the interneuron (interprets signal & decided what to do with it)
4) the efferent neuron (carries the response message from spinal cord to muscle/organ) (exiting the brain)
5) the muscle/effector organ itself (carries out the response)

Question 4

Propioceptors + their function + the two proprioceptor’s and their function

Answer 4

*proprioception= person’s ability to sense where the body is in space (the position, orientation, and movement of the body) (balance)

*proprioceptor’s= receive information and send it back to the brain (hold balance, dont fall)

-muscle spindle’s and golgi tendon organs are sensory receptors and examples of propioceptor’s

*muscle spindle’s:
-attached to muscles
-maintain muscle tension
-detect changes in muscle length
-takes in at what point a muscle is eccentric (lengthening) and concentric (shortening)
-ex. knee-jerk reflex

*golgi tendon organs:
-attached to tendons
-detect changes in muscle tension
-prevent injury, unconsciously (protect muscle from excessive tension that might damage the muscle)

Question 5

Components of the neuromuscular junction

Answer 5

*neuromuscular junction= the area where the nerve and the muscle meet

-motor neuron (responsible for stimulating a number of fibres)
-axion (nerve’s pathway to muscle)
-axion terminal
-acetylcholine (chemical neurotransmitter)
-synaptic cleft (gap between nerve and muscle)
-muscle cell
-receptors on muscle cell for acetylcholine
-sarcolema

Question 6

Components of a motor unit

Answer 6

-moro neuron (nerve) (efferent)
-axion (nerve pathway to muscle)
-muscle fibres it stimulates

Question 7

Most important structural components within the sarcomere of a muscle fibre

Answer 7

*actin (thin filament)

*myosin (thick filament)

*troponin

*tropomyosin

Question 8

Steps of how a muscle contracts

Answer 8

1. A signal (impulse) is sent from BRAIN , it travels down the SPINAL CORD, onto a nerve (motor neuron), it runs along its AXON (nerves pathway to the muscle), it then reaches the NEUROMUSCULAR JUNCTION (where nerve + muscle meet)
2. When the signal from the brain reaches the neuromuscular junction, it causes the release of ACETYLCHOLINE (ACh) from the nerve into the space b/w the nerve + muscle/neuromuscular junction (SYNAPTIC CLEFT)
3. ACh travels across the SYNAPTIC CLEFT and binds to the RECEPTORS on the muscle cell
4. CALCIUM (CA²⁺) IONS that are stored in the muscle cell’s SARCOPLASMIC RETICULUM are released into the muscle cell’s SARCOPLASM (cytoplasm/ fluid of the muscle cell)
5. The CA²⁺ ions travel to the ACTIN FILAMENTS within the SARCOMERE, which contain the proteins TROPONIN and TROPOMYOSIN
6. C-A²⁺ ions bind to TROPONIN, which causes the DISPLACEMENT of TROPOMYOSIN on the actin filaments, and reveals the BINDING SITE for the MYOSIN filament (HEAD portion of myosin filament)

• The head of the myosin filament has an ADENOSINE DIPHOSPHATE (ADP) + and INORGANIC PHOSPHATE (Pᵢ) molecule bound to it from previous muscle contraction *
  ADP + Pᵢ = ATP (adenosine triphosphate) energy

7. The head of the myosin filament DROPS the inorganic phosphate Pᵢ molecule, then with the remaining ADP molecule, BINDS to the actin filament’s MYOSIN BINDING SITE (site that was exposed when the CA²⁺ ions bound to TROPONIN, which then caused the displacement of TROPOMYOSIN on the actin filament to reveal binding site for the MYOSIN HEAD)
8. With the use of the ADP energy that is attached to the myosin filament’s head (btw the myosin head is bound to the actin filament’s myosin head binding site rn) , the ADP energy is RELEASED and the myosin head PULLS on the actin filament at the binding site to produce a SLIDING motion
9. The sliding motion causes the SARCOMERE (muscle fibre) to shorten or CONTRACT
10. ATP energy molecules bind to the myosin head again in order to cause the myosin head to detach from the actin filament’s myosin head binding site
11. AGAIN… a chemical reaction in the myosin head breaks down the ATP into ADP + Pᵢ and the sliding filament process starts again