nervous system

Question 1

what are the 2 kinds of nervous tissue cells

Answer 1

neurons// neuroglia

Question 2

what is the function of a neuron

Answer 2

conducts signals

Question 3

what is the function of the neuroglia

Answer 3

connection and support to the neurons

Question 4

what is the function of nervous tissue (2)

Answer 4

irritability// conduction

Question 5

draw and label the neuron (8)

Answer 5

neucleous// dentrites// cell body// axon (hullux)// schwanns cells// myelin sheath// node of ranvier// axon terminals

Question 6

what is a motor unit

Answer 6

a single neuron & the muscle fibres it supplies

Question 7

what are the 3 types of neurons

Answer 7

afferent (sensory)// efferent (motor)// interneurons (connecting)

Question 8

which direction to afferent neurons send impulses

Answer 8

spinal cord to brain

Question 9

which direction to efferent neurons send impulses

Answer 9

brain to spinal column & muscles

Question 10

what do interneurons do

Answer 10

relay impulses between neurons

Question 11

what is the absolute refractory period

Answer 11

this is when the an action potential is being passed. the sodium ions (Na+) enter and the potassium ions (K+) leave the cell depolarizing it. it cannot then receive another impulse.

Question 12

what is saltatory conduction

Answer 12

the is the jumping of the action potential along the nodes of ranvier via the myelin sheathes. once this happens the area behind can then re polarize.

Question 13

what is the refractory period

Answer 13

Na+ leaves and K+ re-enters the area re polarizing and therefore a new impulse can be received

Question 14

what is the propagation of a nerve impulse

Answer 14

when an action potential is received in the nucleus and they summate at the axon hullux if the signal is strong enough it will cause a rapid depolarization meaning it becomes +ve as Na+ enters and K+ leaves the area. the impulse can then jump over the nodes of ranvier via the myelin sheaths down the schwanns cells known as saltatory conduction. this means that re-polarization of the area has taken place and another signal can be processed this is call the refractory period. once the signal reaches the axon terminals where they connect with a muscle fibre (the motor unit) Ach diffuses across the synaptic cleft from the synaptic vesicle and binds to the receptors on the motor end plate. the impulse travels down the sarcolemma through the T Tubules. This triggers the Sarcoplasmic recticulum to release Ca++ into the sarcoplasm where it binds to troponin the thin actin filaments. Troponin pulls tropomysium off the active actin sites allowing the heads of the myosin filaments to bind with the actin forming cross bridges. ATP is used to pull actin filaments together so they slide past each other to contract the muscle this is known as the sliding filament theory.

Question 15

what 3 things need to be present for a muscle contraction

Answer 15

Action potential// Ca++// ATP

Question 16

what happens when the contraction phase of the propagation of the nerve ends

Answer 16

the SR takes back the Ca++ from the troponin and the tropomysium returns to its position blocking the binding sites of the actin. the myosin heads can no longer bind and the muscle fibre returns to its relaxed state.

Question 17

What is the resting membrane potential in the propagation of a nerve impulse

Answer 17

The difference between the electrical potential on either side of the membrane.

Question 18

What is the action potential of a nerve impulse neurons membrane

Answer 18

The rapid depolarisation of the neurons