Anatomy and Physiology Answer Key

Because both conscious and unconscious controls are

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Unformatted text preview: Schwann cells (d) Neurons in the PNS frequently have to transmit over long distances so speed of impulse conduction is critical to efficient function. 4. The destruction of the myelin prevents those (previously myelinated) axons from conducting. Without insulation, the neuron membrane leaks ions and the local current is attenuated and insufficient to depolarize the next node. Note: myelinated axons only have gated channels at their nodes, so action potentials can only be generated at node regions in those axons that were previously myelinated. The Human Brain (page 73) 1. (a) (b) (c) (d) (e) (f) (g) (h) 2. The brain is protected against physical damage and infection by the bony skull, by the meninges overlying the delicate brain tissue, and by the fluidfilled ventricles, which absorb shocks and deliver nutritive substances (via cerebrospinal fluid) to the brain tissue. The blood-brain barrier formed by the endothelial tight junctions of capillaries surrounding the brain is also the main protection against toxins and infection as microbes and many large molecules cannot cross it. Anatomy and Physiology 3. Breathing/heartbeat: brainstem (medulla) Memory/emotion: cerebrum Posture/balance: cerebellum Autonomic functions: hypothalamus Visual processing: occipital lobe Body temperature: hypothalamus Language: motor and sensory speech areas Muscular movement: primary motor area (a) The CSF is produced by the choroid plexuses, which are the capillary clusters on the roof of each ventricle. It circulates through the ventricles and returns to the blood via projections of the arachnoid membrane. (b) If this return flow is blocked, fluid builds up in the ventricles causing hydrocephalus, and consequently pressure on the brain tissue and brain damage. Reflexes (page 77) 1. Higher reasoning is not a preferable feature of reflexes because it would slow down the response time. The adaptive value of reflexes is in allowing a very rapid response to a stimulus. 2. A spinal reflex involves integration within the spinal cord, e.g. knee jerk (monosynaptic) or pain wit...
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