Nervous Coordination

Question 1

Name 3 types of muscles in the body and where they are located

Answer 1

Cardiac: In the heart
Smooth: Walls of blood vessels and intestines
Skeletal: attached to incompressible skeleton by tendons

Question 2

What does an antagonistic pair of muscles mean?

Answer 2

Muscles can only pull, so they work in pairs to move bones around a joint. Pairs pull in opposite directions. Agonist contract while antagonist is relaxed

Question 3

Describe the gross structure of skeletal muscle

Answer 3

Muscle cells are fused to form parallel muscle fibres (myofibrils) bundles. Arrangement ensures there is no point of weakness between cells. Each bundle is surrounded by endomycium which is loose connective tissue with many capillaries

Question 4

Describe the microscopic structure of skeletal muscle

Answer 4

Myofibrils: site of contraction
Sacroplasm: shared nuclei and cytoplasm with lots of mitochondria and endoplasmic reticulum
Sarcolemma: folds inwards towards sarcoplasm to form T tubules.

Question 5

What are Isotropic bands (I-Bands) + Anisotropic bands (A-Bands)

Answer 5

I - Contains only actin and shows up light
A - Contains myosin and actin but they overlap and myosin controls the band and shows up dark

Question 6

What does z-line to z-line form

Answer 6

Sarcomere

Question 7

What is the H- zone

Answer 7

Where actin and myosin don’t overlap in the A- band , so it is only myosin

Question 8

How is muscle contraction stimulated

Answer 8

1. Neuromuscular junction: action potential = voltage-gated Ca2+ channels open
2. Vesicles are stimulated by Ca2+, moving towards the presynaptic membrane, and fusing with it.
3. Exocytosis of Ach , which is released to the synaptic cleft
4. Ach binds to neurotransmitter receptors on Na+ channel proteins on skeletal muscle cell membrane
5. Influx of Na+ = depolarisation

Question 9

Role of Ca2+ ions in muscle contraction

Answer 9

1. Action potential moves through t-tubules in the sarcoplasm = Ca2+ channels in sarcoplasmic reticulum open
2. Ca2+ binds to troponin, triggering conformational change in tropomyosin
3. Exposes binding sites on actin filaments so actinmyosin bridges can form

Question 10

Where are slow + fast twitch muscle fibres found?

Answer 10

Slow = Sites of sustained contraction e.g calf muscle

Fast = Sites of short-term, rapid, powerful contractions e.g. biceps

Question 11

Role of slow and fast twitch muscle fibres

Answer 11

Slow = Long duration contraction, well adapted to aerobic respiration to prevent lactate build up

Fats = Powerful short term contraction; well adapted to anaerobic respiration

Question 12

Structure of a motor neuron

Answer 12

Cell body = contains RER + organelles
Dendrons = branch dendrites which carry impulses towards the cell body
Axon = long unbranched fibre carries nerve impulses away from cell body

Question 13

3 processes schwann cells are involved in

Answer 13

1. electrical insulation
2. phagocytosis
3. nerve regeneration

Question 14

How does an AP pass along an unmyelinated neuron?

Answer 14

1. Stimulus leads to influx of Na+ ions. First section of the membrane depolarise.
2. Local electrical current causes Na voltage gated channels further along the membrane to open. Meanwhile, the section behind begins to repolarise
3. Sequential WOD

Question 15

Why do myelinated acons conduct impulses faster than unmyelinated axons

Answer 15

Saltatory conduction, impulses jump from one Node of Ranvier to another , since depolaristaion cannot occur where myelin sheath acts as electrical insulators, so impulse doesn’t have to travel along whole axon length.

Question 16

What is resting potential and how is it established?

Answer 16

Potential difference across a neuron membrane when not stimulate normally 70mV in humans. Membrane is more permeable to K+ than Na+ . Sodium - potassium pump actively transports 3NA+ out of cell and 2K+ into cell, which establishes an electrochemical gradient

Question 17

What happens during depolarisation

Answer 17

1. Stimulus occurs. Na+ channels open and facilitated diffusion moves Na+ down electrochemical gradient
2. P.d across membrane becomes more +ve
3. if membrane reaches threshold potential (-50mV) voltage gated Na+ channels open

3.Significant influX of Na+ ions reveres p.d to +40mV

Question 18

What happens during repolarisation

Answer 18

1. Na+ channels close and K+ channels open
2. Facilitated diffusion of K+ ions out of cell down their electrochemical gradie t
3. p.d across membrane becomes more -ve.

Question 19

What happens during hyperpolarisation

Answer 19

1. P.d becomes more -ve than resting potential
2. This makes a refractory period

3.K+ channels close and sodium potassium pump establishes resting potential

Question 20

Explain what a refractory period is and importance?

Answer 20

When no stimulus is large enough to raise membrane potential to threshold. Ut ensures a unidirectional impulse and discrete impulse and limits frequency of impulse transmission

Question 21

What is the all or nothing principle

Answer 21

Any stimulus that cuases the membrane to reach threshold potential will generate an action potential all action potentials have same magnitude

Question 22

Name factors that affect the speed of conductance

Answer 22

1.Myelin sheath
2. Temperature
3. Axon diameter