HNS01 Overview Of The Central Nervous System

Question 1

CNS components

Answer 1

1. Cerebral cortex
2. Cerebellum
3. Brainstem
4. Spinal cord (connect to higher centres by brainstem)

Question 2

Function of cerebral cortex

Answer 2

1. Cognition
2. Perception
3. Voluntary movement

Question 3

Function of Limbic system

Answer 3

Emotion

Question 4

Function of Brainstem

Answer 4

Housekeeping

Question 5

Function of Cerebellum

Answer 5

Motor coordination

Question 6

2 type of synapses in Brain

Answer 6

1. Excitatory / Glutamatergic synapses
   - AMPA receptor
   - NMDA receptor
   - Kainate receptor
2. Inhibitory synapses (e.g. GABAergic synapse)
   - GABA-gated Cl channel (other agonists: Benzodiazepine, Ethanol, Barbituate)

Question 7

Excitatory synapse and Inhibitory synapse

Answer 7

Excitatory synapse:
Action potential in presynaptic neuron
—> lead to Depolarisation in postsynaptic neuron

Inhibitory synapse:
Action potential in presynaptic neuron
—> lead to Hyperpolarisation in postsynaptic neuron

Question 8

Sensation and Perception

Answer 8

Sensation (OBJECTIVE sensory physiology):

1. Event: interact with sense organs
2. Stimulus: adequate stimulus to receptor
3. Excitation: central processing
4. Integration: central processing in functioning brain centres

Perception (SUBJECTIVE sensory physiology):
5. Impression: conscious subject
6. Perception: subject with experience, reasoning, personality
—> performed in Association Cortex

Question 9

Important processes in sensory system

Answer 9

1. Sensory transduction
   - receptor
2. Receptive field
   - receptor
   - peripheral and central neuron
3. Central processing

Question 10

Somatic senses

Answer 10

1. Mechanoception
2. Proprioception
3. Thermoception
4. Nociception

Question 11

Special senses

Answer 11

1. Taste
2. Smell
3. Hearing
4. Balance
5. Vision

Question 12

Mechanoreceptors in skin

Answer 12

Mechanical stimuli delivered to skin activate several mechanoreceptors simultaneously but to different degree

1. Pressure (Slowly adapting)
   - Merkel’s disk
2. Pain / Temperature
   - Free nerve ending
3. Touch
   - Meissner’s corpuscle
4. Vibration (Rapid adapting)
   - Pacinian corpuscle
   - Ruffini’s ending (Skin stretch)

Question 13

Crossed ascending projection

Answer 13

Information from one side of body crossed at different levels of spinal cord / brainstem
—> opposite side of cerebral cortex

Question 14

Cross at Dorsal column nuclei

Answer 14

1. Discriminative touch
2. Vibration
3. Position sense

Question 15

Cross at Spinal cord

Answer 15

1. Temperature

2. Pain

Question 16

Narrow vertical columns of submodalities in somatosensory cortex

Answer 16

1. Slow-adapting functional unit

2. Rapid-adapting functional unit

Question 17

Topographic body map

Answer 17

• Distorted body surface for tactile sensibility

- Magnified areas of high acuity

Question 18

Taste

Answer 18

• bitter, salt, sour, sweet, umami (MSG) (all chemical stimulation)
• all chemical stimulation
• G-protein: Sweet (甜5), Bitter (苦2), Umami (味精4)
• Ion channels: Salty (ENaC), Sour (OTOP1, PKD2L1), (bitter), Chilli (Nociception)

Question 19

Common plan of sensory systems

Answer 19

1. Sensory transduction (feature extraction)
2. Topographic organisation (maps can be found at different levels)
3. Bilateral inputs to cortex (e.g. skin: crossed, auditory: **bilateral, taste: **ipsilateral)

Question 20

Motor system

Answer 20

CNS —> PNS (Motor division) —> Somatic NS (e.g. skeletal muscle)

Example: reflexive control (Stretch reflex, Golgi tendon reflex, Pain reflex)

Question 21

3 Cardinal neural regions responsible for motor control

Answer 21

1. Motor cortex
2. Cerebellum
3. Basal ganglia

Question 22

Crossed descending projection

Answer 22

One side of motor cortex to contralateral side of head and body

Question 23

Seizure

Answer 23

Epilepsy
—> Spread of abnormal synchronised cortical discharge (e.g. cortical area responsible for trunk to area responsible for head)

Question 24

Association cortex function

Answer 24

1. Cognition
2. Consciousness

Question 25

Lateralization of cerebral cortex

Answer 25

Left hemisphere: - Right hand - ***Logical thinking - ***Language ability - Writing - ***Science and math work Right hemisphere: - Left hand - Musical and artistic ability - ***Perception of space - ***Imagination and fantasising - ***Body control and awareness

Question 26

Limbic system

Answer 26

Components: 1. Hippocampus 2. Amygdala (fear response, negative emotions) Function: 1. Cognition - ***Learning and memory - Sleep and wakefulness - ***Emotion

Question 27

Imaging techniques

Answer 27

1. Functional MRI 2. CT scan 3. PET scan (molecular imaging)

Question 28

Parkinson’s disease

Answer 28

Degeneration of Dopamine neuron within Substantia nigra (area within Basal ganglia) —> movement disorders

Question 29

Alzheimer’s disease / Dementia

Answer 29

Shrinkage of Hippocampus (+ Cortex) —> impairment of learning and memory Causative components: 1. Amyloid plaque (extracellular) 2. Neurofibrillary tangle: Tau fragment (intracellular) —> ALL lead to damaged neurons

Question 30

Psychosis / Schizophrenia

Answer 30

Blockade of NMDA receptor by PCP (phencyclidine piperidine) —> do not allow Ca, Na to go through channel —> behaviour mimic schizophrenia

Question 31

Drug addiction

Answer 31

Dopamine neurons in Nucleus accumbens (part of Basal ganglia) Heroin: 1. Bind to opioid receptor of GABAergic inhibitory neuron —> do not allow GABAergic inhibitory neuron to release GABA onto GABA receptor on presynaptic receptor —> NO inhibition of dopamine release 2. Direct agonist to opioid receptor on postsynaptic neuron —> direct stimulation of postsynaptic neuron —> cAMP —> activated protein Cocaine: 1. Block reuptake transporter on presynaptic neuron —> more dopamine to postsynaptic neuron —> cAMP —> activated protein

Question 32

Summary

Answer 32

Limbic system: - Hippocampus: Alzheimer’s disease - Amygdala: Fear response, Negative emotions Basal ganglia: - Substantia nigra: Parkinson’s disease - Nucleus accumbens: Drug addiction