1: Introduction to the Nervous System

Question 1

Neuron: Nerve

Answer 1

Bundle of axons of neurons wrapped in connective tissue.

Question 2

Neuron: Dendrites

Answer 2

Sensory information comes in through these.

Question 3

Neuron: Axon

Answer 3

Where electrical impulse is generated and propagates down the axon.

Question 4

Neuron: Myelin

Answer 4

Fatty sheath/insulator which helps speed up the rate at which the electrical impulse is passed down the axon.

Question 5

Integration in the Nervous System

Answer 5

A single neuron integrates all its many inputs (some inhibitory, some excitatory) to produce a single response in the form of a nerve impulse or action potential. This allows the NS to process a huge amount of info very quickly and produce appropriate responses.

Question 6

Glial Cells: Role

Answer 6

Protective and supportive role to the neurons. 6 types - 4 in the CNS and 2 in the PNS.

Question 7

CNS Neuroglia: Astrocytes

Answer 7

• Largest and most numerous
• Physically support neurons
• Wrap around capillaries and form the blood-brain barrier

Question 8

CNS Neuroglia: Ogliodendrocytes

Answer 8

• Form a myelin sheath along axons in the CNS

- Myelinated axons permit faster transmission of information

Question 9

CNS Neuroglia: Microglia

Answer 9

Help protect CNS via phagocytosis of waste, debris and pathogens.

Question 10

CNS Neuroglia: Ependymal Cells

Answer 10

• Line the ventricles of the brain and the central canal of the spinal cord
• Secrete cerebrospinal fluid (CSF)
• Monitor composition of CSF and help circulate it

Question 11

PNS Neuroglia: Schwann Cells

Answer 11

• Wrap around PNS axons
• Multiple Schwann cells form myelin sheath
• Also encases non-myelinated axons`

Question 12

PNS Neuroglia: Satellite Cells

Answer 12

• Surround cell bodies of axons in the PNS
• Provide structural support
• Regulate passage of material between neutron soma and interstitial fluid

Question 13

Membrane Potential

Answer 13

The inside surface of the membrane has a negative charge compared to the outside.

Comes about because intra and extracellular fluids have a different composition - creating concentration gradients.

Higher concentration of Na+ ions OUTSIDE cells compared to inside and vice versa for K+ ions.

Question 14

Resting Membrane Potential

Answer 14

Potential difference when a cell is at rest, with the inside of the cell membrane negative with respect to the outside.

Question 15

Depolarisation

Answer 15

The rapid reversal of the membrane potential from the inside negative at rest to inside positive and is what allows neurons to signal.

Open sodium channels.

Question 16

Repolarisation

Answer 16

The return of the membrane potential to normal and the readiness to pass on another signal.

Open the potassium channels.

Question 17

Nerve Impulse Conduction

Answer 17

A wave of depolarisation followed by repolarisation then moves rapidly along the axon as more and more sodium channels open.

Question 18

Neurotransmitters

Answer 18

Chemical communication between neurons.

Question 19

Synapse

Answer 19

The small gap between the axon of one neurone and the dendrite of another.

Question 20

CNS: Brain

Answer 20

• Externally, grey matter (cell bodies) visible

- Internally, white matter (axons) interconnecting different areas of the brain

Question 21

CNS: Spinal Cord

Answer 21

• Externally, white matter visible

- Grey matter in the centre of the cord

Question 22

PNS: Spinal and Cranial Nerves

Answer 22

• 12 pairs of cranial nerves

- 31 pairs of spinal nerves

Question 23

Sensory NS

Answer 23

Processes sensory information e.g. vision, hearing, somatic sensation (touch), taste and smell.

Question 24

Motor NS

Answer 24

Contains motor nerves which conduct impulses from the CNS and PNS to the muscles, organs and glands e.g. peristaltic wave.

Question 25

Autonomic Sensory Functions

Answer 25

• Stretch receptors: in hollow structures like the bladder, gut and uterus
• Chemoreceptors
• Baroreceptors

Question 26

Somatic Sensory Functions

Answer 26

E.g. touch, pain, temperature, etc.

Question 27

Somatic Motor Functions

Answer 27

Movement of all skeletal muscles.

Question 28

Autonomic Motor Functions

Answer 28

Movement of all smooth muscles and gland activity.

Question 29

Characteristics of Reflexes

Answer 29

• Quick
• Stereotyped
• Automatic
• Can involve cranial nerves
• Can involve spinal cord or brain
• Can be autonomic or somatic
• Can be innate or acquired
• Some are present early in life, but are overridden later in life