Muscles

Question 1

What are muscles used for

Answer 1

Lift objects, move, walk, maintain posture, to circulate blood(heart), push materials through organs and tissues eg lung, gut and bladder. And allow your eyes to keep things in focus, to make your hairs stand up

Question 2

What is cardiac muscle tissue

Answer 2

Small branched cell interconnected to other heart cells is porous junctions. Centrally located nucleus. Striated

Question 3

Where is cardiac muscle tissue located

Answer 3

Heart

Question 4

Innervation of cardiac muscle tissue

Answer 4

Rely on specialised auto rhythmic cardiac placement cells (sinoatrial and atrioventricular nodes) for timing of contraction.
Contra in rate altered by automatic nerves to the sinoatrial pacemaker

Question 5

Function of cardiac muscle tissue

Answer 5

Blood circulation and maintain hydrostatic blood pressure
Works as functional syncytium

Question 6

What is smooth muscle

Answer 6

Small spindle shaped cells tapered ends. Single, central nucleus. Non striated

Question 7

Where is smooth muscle located

Answer 7

Located in the walls of blood vessels, around hollow organs and repsiratory, digestive, cardiovascular and reproductive tracts

Question 8

Innervation of smooth muscle

Answer 8

Can be self contractile eg digestive tract, or requires direct innervation by autonomic/ involuntary nerves

Question 9

Function of smooth muscle

Answer 9

Movement of food bolus, urine and reproductive tract secretions. Regulation of the diameter of airways and blood vessels. Piloerection. Works as a functional syncytium

Question 10

What is skeletal muscle

Answer 10

Very larger striated cells. Multi nucleated. Close the plasma membrane each cell is a cellular syncytium (cytoplasmic mass containing several nuclei)

Question 11

where is skeletal muscle located

Answer 11

Throughout the body associated it’s bones and connective tissue

Question 12

Innervation of skeletal muscle

Answer 12

Voluntary/ somatic nerves

Question 13

Function of skeletal muscle

Answer 13

Movement/ stabilisation of skeleton. Gaurd entrances/ exits to digestive, respiratory and urinary tracts, generates heat, protects internal organs, stores nutrient reserve

Question 14

Prime mover (agonist)

Answer 14

Muscles whose contraction is responsible for producing a particular movement

Question 15

Antagonist muscles

Answer 15

Work in the opposite directions to an agonist muscle to control or slow it down

Question 16

Synergistic muscle

Answer 16

Work together in the same direction as the prime mover and assist movement

Question 17

Fixator (type of synergistic)

Answer 17

Muscles that stabilise part of the body to prevent movement at a joint and at the origin of an agonist muscle to allow for effective controlled movement to be achieved

Question 18

Origin point

Answer 18

Place were the fixed end of a skeletal muscle attatches to bone (proximal)

Question 19

Insertion

Answer 19

The place where muscles moveable end attatches (distal)

Question 20

Innervation of skeletal muscles by the nervous system

Answer 20

-skeletal muscles are innervated (supply an organ with neves) by motor neurones that carry efferent information from the central nervous system to the muscles via myelinated axons
-each MN axon formed a motor unit
-trunk and limbs: cell body of MNS: ventral horn of the grey matter of the spinal cord. MN axons leave the spinal cord via the ventral roots and synapse onto muscle cell fibres
-face and oropharyngeal: cell body of MNS: brain stem
Mn axons: leave the brainstem via the cranial nerves and again synapse directly onto muscle cells

Question 21

What is a motor unit

Answer 21

• a single motor neurone and ask muscle fibres it innervates = motor unit
  -the cell bodies (soma) of all MN’s innervating a same muscle are stacked vertically in the spinal cord. This is known as a motor nucleus

Question 22

What does the CNS do in regards to the motor unit

Answer 22

-the CNS calculates the number of motor units required to produce the right level of muscle contraction
-the CNS allows them to be swapped in and out to maintain contraction over time to avoid fatigue
-the size and number of motor units in a muscle also determines level of control the CNS has over muscle contraction

Question 23

What is the neuromuscular junction

Answer 23

-each muscle fibre is innervated by only one MN
-in the area where the axon of an MN and a muscle fibre are held in close proximity, they form a clump of synapses collectively known as the neuromuscular junction
-each of these synapses is elongated and the chemicals communicate at these synapses using a small molecule called acetylcholine

Question 24

What is myasthenia

Answer 24

-sevre muscle weakness
-prevalence in uk 15/100000
-fatal as respitaoy muscle failure life expectancy 20 to 30 years before drug therapy

Question 25

What are the causes of myasthenia

Answer 25

-auto immune, anti bodies produced by patients against their own ACh receptors
-congenital, transfer of antibodies from mum to baby
-genetic, mutation affecting ACh release

Question 26

What are the symptoms of myasthenia

Answer 26

-abnormal muscle fatigue during repetitive or prolonged muscle contraction, prominent in the cranial muscles, limbs and chest
-variation in symptom severity- on a daily basis or over longer period of time

Question 27

How can tou treat myasthenia

Answer 27

-reversal of symptoms by drugs preventing ACh degradation
-test by short acting cholinesterase inhibitor: edrophonium
-treated by long lasting cholinesterase inhibitors: neostigmine, pyridostigmine

Question 28

Isometric

Answer 28

Doesn’t change length increasing tension

Question 29

Isotonic

Answer 29

Muscles change length, bearing the load

Question 30

What is myofibrils

Answer 30

• long protein rich structures in muscles
  -made of repeating units called sacromeres

Question 31

What do sarcomeres contain

Answer 31

-parallel think protein stands: made of myosin that are free from any permeant point of attatchment
-thin and thick strands are organised in an interdigiated manner within the sarcomeres
-the sarcomere is the basic contractile unit of the muscle fibre

Question 32

What is the sliding filament theory

Answer 32

1)Calcium binds to tropin which frees the actin from tropomyosin.
2)ATP binds to myosin
3)This creates ADP and Pi = cock and bind (myosin head can move and bind to actin)
4)ADP and Pi leaves =power stroke
5)ATP binds= release
6)repeat

Question 33

What id excitation - contraction coupling in each muscle cell

Answer 33

-at rest : low calcium in sarcoplasm
-excitation initiation of muscle fibre ap: excitation of membrane
Calcium exported out of SR
-high calcium in sarcoplasm causes muscle contraction
-end of muscle fibre ap: calcium pumped back into SR so low calcium in sarcoplasm causes contraction to stop
-excitation ( of a muscle cell membrane) and contraction (of a muscle cell) occur nearly simultaneously eg they are coupled

Question 34

Contraction efficiency and sarcomere overlap :

Answer 34

-sacromeres (=muscle) too stretched or too contracted equals a decreased cross bridge formation due to limited overlap or hindrance, respectively less tension that can be generated
-optimal sarcomere light equals optimum cross bridge formation equals maximum tension (80%-120% of the resting length)