The Structure And Functioning Of The Nervous System: Questions

Question 1

Where in the body are the peripheral nerves found?

Answer 1

PNS

Question 2

Structure and functioning of myelin sheath

Answer 2

• consists of complex material formed of protein and phospholipid (fat) that is laid down as a sheath around axons of certain neurons
• fatty material comes from Schwann cells
• myelination greatly increases conduction speed of action potentials
• myelin sheath also increase rate of transmission of nerve impulses
• myelin decrease capacitance across cell membrane and increases electrical resistances, preventing current from leaving axon

Question 3

How are chemical stimuli transducers into electrical impulses and where else in the body are chemical stimuli converted into electrical impulses?

Answer 3

• chemical stimuli in body converted into electrical impulses when some sensory input system in the body is triggered
• transduction begins with the interaction of chemical stimuli with specialized sensory receptors in the mouth, nose or skin
• chemical molecules interact with receptor proteins on the receptor cell membranes
• the receptor proteins then activate secondary messenger systems inside the cell which open ion channels in the cell membrane
• this causes the cell to initiate a signal to the brain in the form of an electrical impulse

Question 4

Why are we unable to taste properly when we have a blocked nose, despite our tongues not being affected?

Answer 4

• parts of brain that interpret taste and smell are linked—> sense of smell intimately connected to that of taste
• as a result, sensation of taste requires both actual taste and the smell of food
• when food is placed in the mouth, of our molecules from that food travel through the passage between the nose and mouth to the olfactory receptor cells at the top of the nasal cavity, just beneath the brain and behind the bridge of the nose
• if mucus = too thick—> air and odor molecules cannot reach olfactory receptor cells —> Brain does not receive signal
• is tidying odor contributes to taste of food —> receiving of signals hindered or reduced = sensation of taste also reduced

Question 5

Which part of brain is damaged if person is having difficulty forming words

Answer 5

Left frontal lobe

Question 6

What occurs when occipital lobe is damaged

Answer 6

Difficulty in vision

Question 7

Difficulty hearing words caused by

Answer 7

Temporal lobe damage

Olfactory mechanism damaged

Question 8

If someone had damage to part of brain associated with speaking words, what is the likelihood that the patient would also be suffering from partial face paralysis

Answer 8

Unlikely to cause facial paralysis

- cerebellum responsible for movement of facial muscles and is independent of the cerebrum which controls speech

Question 9

Multiple sclerosis (MS) pathophysiology

Answer 9

• characterized by patches of demyelination
• prevents impulses from being carried effectively —> loss of muscle control, speech, visual ability
• destruction follows immune process:
  1. Matrix metalloproteinases help T cells cross the blood brain barrier into the CNS
  2. T cells reencounter antigens
  3. Activated helper T cells produce pro-inflammatory, cytotoxic factors which promote oligodendrocyte death and demyelination
  4. Macrophages & microglia play significant part in axonal damage

Question 10

Explain how a signal is transmitted across the neuromuscular junction

Answer 10

• Ca^2+ ions released to initiate release of neurotransmitter Acetylcholine from presynaptic cell (I.e. neuron)
• acetylcholine travels across synaptic cleft —> attaches to receptors on postsynaptic cleft (I.e. muscle cell) results in muscle contraction due to neurotransmitter molecules binding to the receptor glycoproteins in the muscle cell

Question 11

Explain what is meant by resolving power (with respect to sensory perception)

Answer 11

Minimum distance between two simultaneously applied stimuli at which those two stimuli will be perceived as two separate stimuli rather than as a single stimulus