Lecture 6: Introduction to Movement Flashcards Preview

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Flashcards in Lecture 6: Introduction to Movement Deck (97)
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1

Three Steps underlying voluntary movement

1. brain sends motor commands to motor neurons in the spinal cord
2. Motor neurons in spinal cord release ACh at neuromuscular junction
3. ACh binds to nicotinic ACh receptors on muscle fibre and trigger muscle contraction

2

Nicotinic ACh receptors

Respond to NT, Acetylcholine. At the neuromuscular junction they are the primary receptor in muscle responsible for muscle-nerve communication that controls muscle contraction.

3

Where are motor neurons found?

In the ventral horns of spinal cord

4

How does AP travel to muscle from spinal cord?

Through the ventral roots

5

Where is acetylcholine released? What does it do once released?

- At the neuromuscular junction
- Released ACh binds to receptors on muscle fibre causing postsynaptic potentials (PSPs) to arise (same rules of temporal and spatial summation apply) and trigger action potentials in muscle fibre

6

What type of receptor are Nicotinic ACh receptors?

nAChR receptors are ionotropic

7

What attaches muscle to bone?

Tendon

8

Muscles are...

a bundle of fibres called myofiber; each fibre is ONE cell with multiple DNA containing nuclei

9

Why do singular muscle fibres have multiple nuclei?

They are a product of cellular fusion

10

What is myofiber made of?

cylinder shaped bundles of protein polymers called myofibrils

11

What is myofibril composed of?

Each myofibril is composed of repeats of a functional unit called sarcomere

12

What is a key factor in muscle contraction?

The dynamic change in the structure of the protein polymers (myofibrils)

13

Sarcomere

Basic contractile unit that makes up myofibril. Each unit has a myosin (thick) and actin (thin) protein filament.

14

Where would you find myosin and actin?

These protein filaments are found in each sarcomere, which is found in myofibril which composes myofiber.

15

Breakdown of muscles

muscles --> myofiber --> myofibril --> sarcomere --> actin and myosin

16

Muscles contract when...

thick and thin filaments pass each other

17

What is the function of the tropomyosin complex?

In a resting state, the tropomyosin complex masks the myosin binding sites in the actin filaments so the myosin head cannot grab the actin fibre

18

What exposes the myosin binding sites on actin?

Binding of ACh to nACh receptors trigger APs in muscle fibre which causes release of Ca2+ from sarcoplasmic reticulum (storage for Ca2+). Calcium ion binds to troponin pulling tropomyosin to the side exposing binding sites.

19

What role does calcium play in muscle contraction?

calcium ions are released from sarcoplasmic reticulum and bind to troponin revealing the binding sites

20

What does the myosin head do when myosin binding sites are exposed? What does it do?

It binds to actin (grabs it) and the bending motion pulls on the actin filaments causing them to slide

21

one motor neuron can be responsible for...

multiple muscle contractions

22

Somatic Nervous System

Receives sensory info from sensory organs (skin, eyes, ears) and controls movement of skeletal muscles. Carries motor and sensory information both to and from the CNS.

23

Muscles contain what types of sensory nerves (also number)?

2 types: muscle spindle and golgi tendon

24

Afferent nerves

SENSORY NERVES - carry info from various body parts close to external environment to the CNS

25

Efferent nerves

MOTOR NERVES - carry info from CNS to the skeletal muscle

26

Muscle spindle

muscle fibre that report muscle length, composed of intrafusal muscle fibres

27

Intrafusal

skeletal muscle fibres that serve as specialized sensory organs that detect the amount and rate of change in length of a muscle

28

What innervates muscle spindle?

Mechanosensory axon terminals

29

Innervate

to supply with nerves

30

Knee-jerk reflex is an example of

a stretch reflex