Nervous System

Question 0

What are the three parts in response to change in environment?

Answer 0

Sensation- receptors detect change inside and outside body.
Integration-process info and determine appropriate response
Reaction- motor output- activation of muscles or glands by neurotransmitters

Question 1

What is the purpose of the nervous system?

Answer 1

Used by animals to increase survival by responding to changes in environment
Any change in environment = STIMULUS

Question 2

What are the 2 divisions of the nervous system?

Answer 2

Central - brain and spinal cord- protected

Peripheral- connects cns to limbs- not protected

Question 3

What’s the difference between the endocrine and nervous system?

Answer 3

NS= fast acting, effects short lasting, info via electrical impulse
ES= slower, chemical agents in blood to cells, lasts longer

Question 4

The peripheral nervous system can be divided. What are the divisions?

Answer 4

Sensory division- conducts impulse from receptor to the cns, informs cns of the state of the body inside and out.
Motor division - conducts impulse from cns to effectors ( muscle and glands)

Question 5

What are the other 2 divisions within the motor division?

Answer 5

Somatic- voluntary, conduct impulse from cns to skeletal muscle, results in a conscious action
Autonomic- involuntary, conduct impulse from cns to smooth muscle, cardiac muscle and glands, reflex action ( fight or flight)

Question 6

What are the 2 types of nervous tissue?

Answer 6

Neurones- conduct impulse

Neuroglia- cells that provide physical support and regulate internal environment

Question 7

What is a neurone?

Answer 7

Specialised to conduct info from 1 part of body to another.

Question 8

Describe the structure of a neurone ?

Answer 8

Cell body= soma
One or more slender processes
Input region= dendrite
Conducting component= axon
Secretory output region= terminal endings

Question 9

What is a dendrite?

Answer 9

Thin branched processes- main function to receive incoming signals.
Increase S A of neurone

Question 10

What is an axon?

Answer 10

Transmit electrical impulse away from cell body.

Most neurones have a single axon( up to 1 meter long)

Question 11

What is a Schwann cell?

Answer 11

Insulating lipid myelin sheath that surrounds axon.

Wrap round axon so tight ( up to 10 times) their cytoplasm is squeezed out leaving only cell memb and nucleus.

Question 12

What are the spaces between the Schwann cells?

Answer 12

Nodes of ranvier- no myelin.

Impulse jumps from node to node

Question 13

Describe the function of the sensory neurone?

Answer 13

Relay impulse from receptors to CNS
1 long dendrite carries impulse from recep. To cell body
1 short axon carries impulse from cell body to CNS

Question 14

Describe the function of the motor neurone?

Answer 14

Relays message from CNS to muscle and organs
Impulse carried along many short dendrite to cell body
1 long axon carries impulse from cell body to effector cells

Question 15

What are relay neurones?

Answer 15

Relay info from sensory to motor neurones

Many short dentrites and axons to carry nerve impulse

Question 16

What are the characteristics of an axon?

Answer 16

Take info away from cell body
Smooth surface - 1 axon per cell
No ribosomes
Can have myelin
Branch further from cell body.

Question 17

Describe the characteristics of a dendrite?

Answer 17

Bring info to cell body
Rough surface - usually many dendrites per cell
Have ribosomes
No myelin
Branch near cell body

Question 18

Describe to process involved in the reflex arc?

Answer 18

Arrival of stim at receptor. Activation of sensory neurone-pass dorsal root- sensation relayed to brain via collateral- info processed in cns - pass ventral root and activation of motor neurone bring about response at effector.

Question 19

Describe a reflex action?

Answer 19

Fast, automatic, act to protect body. Follows reflex arc pathway.eg hand over flame- innate response!!

Question 20

What are the 2 ways neurones conduct information?

Answer 20

From 1 end of neuron to the other end- done electrically via action pot.
Across the space separating 1 neuron from another( space = synapse). This is done chemically via neurotransmitters

Question 21

What is resting potential?

Answer 21

More positive ions outside the cell create potential difference of - 70mv
Generated by k ions moving down conc gradient by facilitated diffusion
Active transport used to move 3 Na ions out for every 2 K ions in. ATP required

Question 22

What happens to the action potential when stimulus occurs?

Answer 22

Triggers threshold stimulus. Change in charge across membrane. Excites neurone cell causing Na channels to open.
Na ions diffuse down conc grad.
Make inside cell less negative.

Question 23

What is depolarisation ?

Answer 23

If pot. difference across membrane = -55 mv more Na channels open
More Na ions diffuse into neurone
All or nothing response

Question 24

What is repolarisation?

Answer 24

At a pot. diff of + 30 mv Na channels close and K ion channels open
K ions diffuse out do neurone down conc grad
Start to get neurone back to resting pot.

Question 25

What is hyper polarisation?

Answer 25

K ion channels slow to close - slight overshoot where too many k ions diffuse out of neurone.

Question 26

What is the refractory period?

Answer 26

After an action potential a neurone can’t be excited straight away
Channels are recovering and can’t open
Ensures action pot. don’t overlap.

Question 27

How are action potentials conducted?

Answer 27

Unmyelinated- undergo continuous conduction

Myelinated- saltatory conduction (leaps)

Question 28

Which has faster AP conduction, myelinated or unmyelinated axons?

Answer 28

Myelinated- jumps from axon to axon

Question 29

Which would conduct AP faster, axon with large diameter or one with small diameter?

Answer 29

Large diameter.

Question 30

How do AP pass from one neurone to another?

Answer 30

Via neurotransmitters eg. Acetylcholine

AP reaches nerve terminal and is converted to chemical signal

Question 31

Describe process of synaptic transmission?

Answer 31

AP arrives at end of axon= synaptic knob- stimulates Ca ion channels to open and Ca ions diffuse into knob. Increase in Ca ions cause synaptic vesicles to fuse with pre synap memb causing relates of Ach into synaptic cleft(exocytosis). Ach diffuses across and bind to receptors on post synaptic memb. Na channels open starting an AP. Neurotran. Removed by enzymes, diffusion or reuptake.