MODULE 2: Nervous Systems

Question 1

Stages of Information Processing

Answer 1

1. sensory input
2. integration
   3 motor output

Question 2

Sensory Neuron

Answer 2

• detect light, sound, etc
• dendrites connect directly to axon
• cell body located in middle of axon

Question 3

Interneuron

Answer 3

• central nervous system (spine & brain)
• collect info into cell body
  axons take to more cells
• one axon takes info into complex dendrite tree

Question 4

Motor Neuron

Answer 4

• dendrites collect info into cell body
• no synapse
• one axon from nervous system to muscle tissue

Question 5

Astrocytes

Answer 5

• gila cells
• central nervous system
• provide support
• regulate extracellular concentration of ions and neurotransmitters
• formation of blood brain barrier
• compound must be VERY lipidphilic to enter brain

Question 6

Oligodendrocytes and Schwann Cells

Answer 6

• oligodendrocytes = CNS
• schwann cells = PNS
• form myelin sheaths around axons
• node of ranvier (Exposed axon) causes action potential
• lipid membranes –> insulator
• defective insulator makes electrical signals stop before end of neuron

Question 7

Resting Membrane Potential

Answer 7

resting potential is negative

-70 mV

Question 8

Ion Gradient / ATPase Pump

Answer 8

• Na+/K+ Atpase pumps 3 Na+ out of cell and 2 K+ into cell
• results in neg charge inside cell
• against concentration –> uses transporter for energy
• electrogenic pump (neg charge inside cell)

OUTSIDE
5mM K+, 150mM Na+, 120mM Cl-

INSIDE
140mM K+, 15mM Na+, 100mM A-

Question 9

Hyperpolarisation

Answer 9

• inside of membrane becomes more negative
• opening of VG K+ channels
• K+ out
• increase membrane potential
• slower
• closed open

Question 10

Depolarisation

Answer 10

• inside of membrane becomes more positive
• opening of coltage gated Na+ channels
• Na+ in
• decrease membrane potential
• fast
• closed –> open –> inactivated –> closed…

Question 11

Action Potential Graph

Answer 11

1. resting stage - VG ion channels closed
2. Stimulus - causes a few Na+ channels to open, Na+ in
3. Depolarisation - if threshold reached, lots of Na+ channels open
4. Hyperpolarisation - K+ channels open & K+ out. Na+ channels inactivate
5. Undershoot - small hyperpolarisation. Also need ATPase to restore ion concentrations

Question 12

Refractory Period

Answer 12

• VG Na+ channels inactivated during repolarisation
• during absolute refractory period (peak), no AP can be generated
• during trlative refractory period (undershoot), AP only if large stimulus
• some Na+ channels closed again
• limits firing frequency of neuson
• local anaesthetics don’t allow channels to go from inactivated –> closed, no pain signals

Question 13

Factors Affecting Conduction Speed

Answer 13

Axon diameter
- increase diameter –
> decrease resistance = faster

Temperature

• chemical reactions occur faster at higher temps
• more kinetic energy

Degree of Myelination

• myelin insulates axon membrane = faster
• affected more by myelin than diameter
• AP only generated at nodes of ranvier (saltatory conduction)

Question 14

Neurotransmitter Release at Chemical Synapse

Answer 14

• chemical stored in synaptic vesicle (not metabolised)
• exocytosis occurs
• axon signal passes through ligand gated ion channel
• allows Ca2+ to enter presynaptic neuron via VG Ca2+ channels
• Ca2+ causes fusion of vesicle and membrane –> release of neurotransmitters
• depolarisation —> excitatory post synaptic potential
• hyperpolarisation —> inhibitory post synaptic potential

Question 15

Temporal Summation

Answer 15

• several EPSPs from same synapse just after each other

- can reach threshold at axon hillock —> axon potential

Question 16

Spatial Summation

Answer 16

• two or more EPSPs from different synapses

- EPSP + IPSP = unlikely to reach AP

Question 17

Potentials: Postsynaptic vs Action

Answer 17

Postsynaptic

• EPSP or IPSP
• graded
• local
• at cell body or dendrites

Action

• depolarisation
• “all or nothing”
• EPSPs add up to cause AP
• generated at axon hillock

Question 18

Direct Synaptic Transmission

Answer 18

• fastest (ms)
• neurotransmitters open ion channels on postsynaptic membrane
• action via ligand gated ion channels (opened via neurotransmitter binding)

Question 19

Indirect Synaptic Transmission

Answer 19

• neurotransmitter binds to receptor on postsynaptic membrane
• activates a signal transduction pathway
• involves a second messenger (GPCR)
• slower (s)

Question 20

Removal of Neurotransmitters From Synaptic Cleft

Answer 20

• must be quick
• can be lost to diffusion or enzymes
• can be recycled by transporters back into neuron

Question 21

Peripheral Nervous System

Answer 21

• 12 pairs of cranial nerves
• 31 pairs of spinal nerves
• both PNS and CNS contain sensory and motor neurons
• contains ganglia (segmentally arranged clusters of neurons)
• contains somatic nervours system (voluntary) and automatic nervous system (involuntary)

Question 22

Dorsal/Posterior

Answer 22

back of body

Question 23

Automatic Nervous System

Answer 23

• sympathetic division
• parasympathetic division
• entric division (intestines)

Question 24

Parasympathetic Division

Answer 24

• from cervical & sacral region
• long pre ganglionic fibre
• short post ganglionic fibre
• “rest & digest”
• calming
• often opposite response to sympathetic division

Question 25

Sympathetic Division

Answer 25

- from thoracic and lumbar region - short pre ganglionic fibre - long post ganglionic fibre - "fight or flight" - bronchi dilate - increase heart rate - glycogen to glucose - adrenaline secretion - digestion inhibited

Question 26

Central Nervous System

Answer 26

brain and spinal cord

Question 27

The Brain

Answer 27

- Forebrain: cerebrum and diencephalon - Midbrain: part of brainstem - Hindbrain: part of brainstem and cerebellum - grey matter outside, white matter inside

Question 28

Cerebrospinal Fluid

Answer 28

- protects CNS - clear fluid - subarachnoid space (b/w skull and cortex) - 4 ventricles and central canal - supplies nutrients and horomones - removes waste - blocked flow in hydrocephalus

Question 29

Spinal Cord

Answer 29

white matter outside grey matter inside

Question 30

Brainstem

Answer 30

- oldest part - basic functions - homeostasis, movement - transfers info to rest of brain - made of three parts: pons, midbrain, medulla oblongata - reticular formation --> selectivity filter than determines arousal and sleep

Question 31

Cerebellum

Answer 31

- coordination - motor function - cognitive and perceptual function

Question 32

Diencephalon

Answer 32

Epithalamus: - connects limbic system (emotional) to rest of brain - pineal gland --> melatonin (sleep) Thalamus: - input from sensory neurons - output via motor neurons Hypothalamus: - homeostasis regulation - biological clock - temp regulation - survival (hunger, thirst, etc)

Question 33

Ventral/Anterior

Answer 33

front of body

Question 34

Cerebrum / Cerebral Cortex

Answer 34

- neocortex - left and right hemisphere connected via corpus callosum - basal nuclei: deep in tissue and important for movement - four lobes - frontal, temporal, parietal, occipital

Question 35

Frontal Lobe

Answer 35

- prefrontal cortex = decision making, planning - motor cortex = control of skeletal muscle - Broca's area = forming speech

Question 36

Temporal Lobe

Answer 36

- auditory cortex = hearing | - Warnicke's area = comprehending language

Question 37

Parietal Lobe

Answer 37

- somasensory cortex (touch) | - sensory integration cortex (integration of sensory info)

Question 38

Occipital Lobe

Answer 38

- visual cortex = processing visual stimuli, pattern recognition - visual association cortex = combining images and object recognition

Question 39

Limbic System

Answer 39

- thalamus - hypothalamus - olfactory bulb - hippocampus (memory) - amygdala (fear)

Question 40

Long-term Potentiation

Answer 40

- high frequency transmission - results in increase size of postsynaptic potentials at synapse - fundamental process for storing memories ---> learning