Coordination 2

Question 1

Speed of conduction:

Answer 1

• Myelination (when myelin wraps around axon) causes speed of conduction to increase from 0,5 ms^-1 up tp is 100 ms^-1, cuz myelin stops depol. to occur.
• Myelin causes salutation conduction, A.P. jump from one node to the next, this is about 50 times faster than on a unmyelinated axon.
• Diameter also effects speed of transmission, thinner axons = greater resistance = slower transmission.

Question 2

When are axons at their r.p.?

What is the r.p.?

Answer 2

• Most of the time unless being depol.

- Potentail difference is about -70mV compered to the outside.

Question 3

R.p. (Negative nature) is achieved by:

Answer 3

• Axon phospholipid bilayer impermeable to K+/ Na+.
• Na-K pumps that constantly pump out 3NA+ ions and pumps in 2K+ each time.
• Separate Na+ and K+ channels are open all times, more of K+ channels, hence K+ diffuses back out much faster than Na+ diffuses in.
• Many large negatively charged m.s inside cell.

Question 4

Synaptic cleft:

Answer 4

• Where 2 synapses meet there is a small gap.

- Contains transmitter substances (neurotransmitters) that which stimulate next neurone.

Question 5

How A.P. Are transmitted:

Answer 5

• A.p. Arrives at presynaptic knob, causing Ca^2+ voltage gated channels to open.
• Ca^2+ ions cause exocytosis of Acetylcholine (ACh) vesicles. (Synapses w/ ACh are called cholinergic synapses)
• ACh moves to presynaptic knob temporarily bonding to the receptor proteins which have a complimentary shape.
• Which causes Na+ (chemical) channels in post synoptic knob to open, Na+ enter and cause depol.
  -ACh is recycled by enz. acetylcholinesterase which breaks the it into acetate and choline which is recombined in the presynaptic knob
  • If ACh is not broken down the Na+ channels will remain open so n. Will be permanently depol.

Question 6

Role of synapses:

Answer 6

1. Ensures one-way transmission.
2. Decreases the overload of info in the brain.
3. Involves in memory and learning.
4. Interconnection of nerve pathways: s. and r. have many dendrite so can cause many more neurones to be activated by just one receptor cell.

Question 7

Striated muscle:

Answer 7

• Is organised into parallel bundles of myofibrils that are attached to the skeleton which is controlled by neurones.

Question 8

Sarcolemma:

Answer 8

• C.s.m., splits into many infoldnings called T-tubules.

Question 9

Sarcoplasm:

Answer 9

• C.p., contains many mitochondria that generate the ATP required for muscle contraction.

Question 10

Sarcoplasmic reticulum (SR):

Answer 10

• ER, they have many protein pumps that transport calcium ions into the cisternae of SR.

Question 11

Structure of the myofibrils:

Answer 11

• Myofibril itself is made up of smaller components of thick and thin filaments.
  —> Thin = Actin, —> Thick = Myosin.
• The Z line is where the actin filaments are attached to.
• The M line does the same for myosin filaments.
• Sarcomere is the part if myofibril between two Z lines.

Question 12

Bands:

Answer 12

• A bands: Darker parts in centre is the region of overlap of action and myosin.
• H band: White area between these dark bands is the region where only myosin is present.
• I band: White are next to the thick black line (Z line) is the region where only actin is present.