Last update: 2019-12-24- 41 - (d) Cerebrum -1. Control of voluntary action -Initiate motor responses - Motor cortex is the region where descending motor pathways emerge -2. Site for sensation/perception -e.g. skin sensation/vision/audition/taste/other sensory functions -Cerebral cortex is the final station of all major ascending sensory systems -3.Site for other integrative functions -Coordinate all voluntary activities -Site for associative functions -Coordinate some involuntary activities -4.Learning/reasoning/intelligence -Memory/personality/emotion/other suitable associative activities Spinal cord -1. Site for synaptic interaction of spinal reflexes -Coordinate some involuntary action such as autonomic reflexes (e.g. contraction of the bladder) and spinal reflexes -Coordinate some simple spinal reflexes -2.provide a means of communication between spinal nerves and the brain -for passage of nerve fibres relaying nerve impulses to the brain -and nerve impulses from the brain any 2 max. 1 any 2 max. 1 any 2 max. 1 any 2 max. 1 any 2 max. 1 any 2 max. 1 _______ (6)
16 Coordination in Humans Last update: 2019-12-24- 42 - AL950202 (ii) * No marks will be awarded if the word brain is used instead of cerebrum and cerebellum. *Cerebrum (0.5) *Cerebellum (0.5) receives impulses from touch receptors on foot (0.5). 1. impulses from the canals, utriculus, and sacculus about the position of the head (0.5) 2. impulses from the limb receptors (muscle / joint). (0.5) process the information (0.5) 5 coordinates (0.5) 1. muscular activities in the leg or leg muscles (0.5). 2. reflexes in the body (0.5) to maintain balance (0.5). The medulla / brain stem also assists to maintain the equilibrium state of the body. 1 (max. 5) (iii) The spinal cord relays sensory impulses (0.5) along sensory neurones (0.5) from the limb receptors (0.5) via the spinal nerves to the brain (0.5). 2 The interneurons and motor neurones (0.5) of the spinal cord relay motor impulses (0.5) from the brain (0.5) to the leg muscles (0.5) via the spinal nerves to effect co-ordinated movement (0.5) and to keep body in equilibrium position (0.5). 3 The spinal cord serves as a pathway to allow the two-way conduction of nervous impulses to and / or from the brain and the leg muscles. (1 + 1 mark only) (5) (b) The unidirectional transmission is mainly determined at synapse (0.5)/ neural-muscular junction. Only the pre-synaptic element / synaptic knob (0.5) possesses synaptic vesicles (0.5) that contain neurotransmitter (0.5). Upon arrival of a nerve impulse, such neurotransmitter is released (0.5)v and it diffuses across a synaptic cleft (0.5) for relaying information to the opposite side. only the post-synaptic membrane (0.5) possesses receptors (0.5) to specifically combine with the neurotransmitter (0.5), leading to post-synaptic depolarization (0.5) and propagation of nerve impulse. 5 (5) (Bonus : mention of refractory period of nerve fibre also plays a role in uni-directional transmission (1))
16 Coordination in Humans Last update: 2019-12-24- 43 - AL960105 Diagram of a synapse in process of neurotransmission showing the following features : synaptic knob, post-synaptic and presynaptic membrane, synaptic cleft, vesicle discharging neurotransmitting substance. (1) (0.5 mark for each label, structure and name must correspond) (4) Structure of a synapse (5) Q5 = 5 marks N. B.