Animal Biology

Question 1

What two types of cell communicate through electro-chemical gradients?

Answer 1

Neurones and muscle cells.

Question 2

What are the short connections between neurones and axons called?

Answer 2

Dendrites.

Question 3

ENa+ = ?

The equilibrium potential of Na+ is?

Answer 3

60mV

Sixty milivolts

Question 4

What two types of cell communicate through electro-chemical gradients?

Answer 4

Neurons and muscle cells.

Question 5

What are the short connections between neurones and axons called?

Answer 5

Dendrites.

Question 6

ENa+ = ?

The equilibrium potential of Na+ is?

Answer 6

60mV

Sixty milivolts

Question 7

What do flexors and extensors do?

Answer 7

Flexors flex causing a smaller angle at the joint.

Extensors extend causing a larger angle at the joint.

Question 8

What are the three types of muscle?

Answer 8

Skeletal: Striated, long cylindrical cells under voluntary control. Nurogenicly controlled

Cardiac: Striated, branched myogenicly controlled cells under involuntary control.

Smooth: Smooth, fusiform myogenicly controled cells under involuntary control.

Question 9

What characteristics do all muscle types have?

Answer 9

Irritable: Can receive and respond to signals.
Contractibility: Can contract, requires energy.
Extensibility: Can be stretched.
Elasticity: Can revert to resting length after extension or contraction.

Question 10

Muscles form cells with many nuclei, what is the term for these?

Answer 10

Syncytium.

Question 11

Humans and fish grow through two different pathways name them.

Answer 11

Humans: Hypertrophy which is the modification of existing muscles cells.

Fish: Hyperplasia where they make more cells to grow muscle.

Question 12

What are the parts of a Sarcomere?

Answer 12

A sarcomere is the muscle unit between two Z-disks.

They have the lighter coloured I-band connected to either side of the Z-disk.

And a darker A-band in the middle.

Question 13

What are the steps of the “Sliding filament” theory?

Answer 13

1. Resting muscle with ATP bound myosin, low [Ca+]
2. ATP hydrolysis, myosin primed for activation.
3. [Ca+] increases, crossbridge formation.
4. ADP is lost, actin moves relative to myosin.
5. New ATP binding, crossbridge breaks.

Cycle begins anew.

Question 14

What [Ca+] is needed for contraction and relaxation?

Answer 14

For Contraction [Ca+] = 5x10⁶

For Relaxation [Ca+] = ~10^7—10^8

Question 15

What does a length-tension curve show?

Answer 15

The amount of tension a muscle can generate based on sarcomere length.

Question 16

What does Ca+ bind to in the muscle cell?

Answer 16

Ca+ binds to troponin C causing a conformational change in the troponin 1 subunit, this moves troponin T and tropomyosin away from the myosin binding site on the filament.

Question 17

How is Ca+ released into the cell?

Answer 17

The action potential will travel down the T-tubules of the cell which will cause the sarcoplasmic reticulum to release Ca+ uniformly across the cell.

Question 18

What does Acetylcholine do in muscles?

Answer 18

It is the neurotransmitter in a muscle-nerve synapse.

Question 19

What is a triad?

Answer 19

A Triad is the T-tubules and the sarcoplasmic reticulum together, this can be seen under high magnification

Question 20

What is the main function of the SR?

Answer 20

To store Ca+ using calcequesterin and pump it into and out of the cytosol using Ca+ pumps.

Question 21

Define the Latent period.

Answer 21

The latent period is a delay between excitation and contraction.~2-5 ms.

Question 22

What are the three types of skeletal muscle?

Answer 22

Type 1 = slow contracting aerobic muscle. Activated by (alpha) 1 neurones which are small, slow and have low recruitment thresholds.

These types are activated by large fast neurones with high recruitment thresholds.

Type 2a = fast contracting aerobic muscle. Fast oxidative glycotic.

Type 2b = fast contracting anaerobic muscle. Fast glycotic.

Question 23

What is phosphocreatine?

Answer 23

A rapidly mobilisable high energy reserve of high energy phosphates, recycles ADP into ATP.

Question 24

What are tonic fibres?

Answer 24

A kind of skeletal muscle fibre found in lower vertebrates, they have smaller, fewer mitochondria and their ATPases are very slow. They develop tension rather than contracting.

Question 25

What determines muscle type?

Answer 25

In fish the muscles are arranged into blocks of the same, they can do this because a fish doesn’t need to combat gravity. In higher vertebrates all three types are present as a mosaic, the most dominant type present determines the type of the muscle.

Question 26

What effect does training have on your muscle type?

Answer 26

Muscle type cannot change between ST and FT because the nerve supply is different. Type 2a fibres can become much more aerobic making them more efficient. Exercising is a stress on the body so the body wants to return to a homeostatic norm but you can become accustom to an elevated level of stress as long as you maintain it as the norm else the body will return to its genetically preset homeostatic level.

Question 27

List the characteristics of cardiac muscle.

Answer 27

The cells are ~20um with a small centrally located nucleus. In humans they are only in the heart, they communicate via gap junctions called intercalated disks. They are myogenic meaning they will spontaneously contract there is a neurogenic override. They have complex controls. Action potentials are slow to develop so the refractory period is large. They will NOT go into tetanus. They have lots of mitochondria and a good blood supply.

Question 28

Lower vertebrates don’t have the neurogenic pacemaker so how do they keep pace?

Answer 28

They have a separate heart chamber that keeps pace called the Sinus venosus.

Question 29

In higher vertebrates what is the hearts pacemaker?

Answer 29

A specialised region of the atrium called the Sinus node.