While walking in the snow, Jim falls and lands awkwardly on his head. Jim goes t
ID: 276386 • Letter: W
Question
While walking in the snow, Jim falls and lands awkwardly on his head. Jim goes to hospital, but Jim’s doctor cannot explain why Jim fell. You are asked to investigate everything that Jim was doing before the accident, to try to find a cause for the fall.
Walking involves all branches of the peripheral nervous system, as well as integration and activity in the central nervous system.
a) Name three different sensory inputs Jim may have detected while walking in the snow. In your answer discuss how this sensory information is detected and processed in the brain, and the brain regions involved.
b) Name three different outputs or efferent responses that are controlled by the peripheral nervous system, when a person is walking in the snow. For each response indicate the efferent pathway involved, the brain region(s) responsible, and explain their involvement.
c) Walking involves somatic motor neurones. Describe the sequence of neuronal events which occur as the brain sends messages to somatic motor neurones to release neurotransmitter from the axon terminals. How are these neurones excited; what two potentials are involved? Include in your answer the mechanisms involved in neurotransmitter release, neurotransmitter binding, and the effect of activation of the post-synaptic receptor upon excitability of the skeletal muscle fibre.
d) In the cerebral cortex, under normal conditions a glutamatergic neurone is innervated (influenced) by GABAergic inputs. Explain the effect of GABA released from the pre-synaptic neurone on the glutamatergic neurone. What overall effect would this have upon the areas of the brain that the glutamatergic neurone influences? A diagram may be helpful.
Explanation / Answer
a) The three sensory inputs are visual which is from the eyes,proprioceptive input from skin,muscles and joints and vestibular system information about the motion,equilibrium and orientation. This information provided by eyes,muscles,joints and vestibular system is sent to the brain stem. This then integrates with cerebellum and cerebral cortex of the brain. The cerebellum coordinates the voluntary movements and cerebral cortex gives information that is stored before on how to follow a different pattern of movement. As this integration takes place brain stem transmits impulse to the body parts and thus helps the person to balance. The regions of the Brain involved are brain stem,cerebral cortex and cerebellum.
b) The efferent responses are sympathetic,parasympathetic and somatic neuronal response. While walking in the snow the sympathetic response gets activated automatically which results in increase of heart rate and also release sugar from liver to blood. The hypothalamus if the brain is involved which controls cardiac regulation. Somatic neuronal response is voluntary control of the body movements. The efferent nerves sends the commands from central nervous system to body and this results in muscle contraction. The brain region involved is precentral gyrus is transmitted from motor neurons and then down to corticospinal tract. This results in the control of the skeletal muscles.
c) The two potentials involved are action potential and end plate potential. The mechanism of how this occurs is an action potential is conducted down the somatic motor neuron to synaptic knob. This results in activation of voltage-gated ca+2 channels. Calcium flows in the synaptic knob and results in release of neurotransmitter which then binds to neurotransmitter receptor sites. Now this activates the ligand-gated sodium ion channels where sodium ions flow in skeletal muscle cell and activates an action potential again then the muscle contracts which is an end plate potential.
d) GABA is an inhibitory Neurotransmitter which leads to depolarisation,increase in calcium and action potentials. So to counter the effects of GABA glutamatergic neurons act. So by activation of this helps in development of hypothalamic, cortical and spinal cord neurons.
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