BIO 235 Assignment 2 Questions and Answers 100% Pass

BIO 235 Assignment 2 Questions and Answers 100% Pass With regards to effort and load, describe the main difference between a lever operating with a mechanical advantage versus a lever operating at a mechanical disadvantage. - Answer- a. Mechanical advantage- If the load is closer to the fulcrum and the effort farther from the fulcrum, then only a relatively small effort is required to move a large load over a small distance.Mechanical disadvantage- If the load is farther from the fulcrum and the effort is applied closer to the fulcrum then a relatively large effort is required to move a small load. Name and describe the locations and actions of the muscles typically used in breathing. - Answer- a. The diaphragm forms the floor of the thoracic cavity. It flattens during inspiration to increase the size of the thoracic cavity. The external intercostals between the ribs increase the lateral and anteroposterior dimensions of the thorax. Internal intercostals between ribs pull ribs together in the opposite movement during expiration to decrease the size of the thoracic cavity. The diaphragm relaxes during expiration to form a dome and decrease the size of the thoracic cavity. The anterior scalenes and the pectoralis minor may assist during forced inspirations. Describe how K+ permeability and Na+/K+ pump activity contribute to the unequal distribution of ions and charges, thereby establishing a resting membrane potential. - Answer- a. K+ permeability - Because the plasma membrane has more K+ leak channels than Na+ leak channels, more K+ leaves the cell than Na+, causing the inner membrane to become more negative and the outside membrane to become more positive. b. Activity of the Na+/K+ Pump - this pumps out 3 Na+ ions for every 2 K+ ions imported. The Na+/K+ ATPase is electrogenic and helps generate the inside-negative resting membrane potential by removing more positive charges from the cell than it puts into it. Describe the difference between spatial and temporal summation in a postsynaptic neuron. - Answer- a. In temporal summation, the action potentials of the presynaptic and the elicited postsynaptic neuron summate with each other. However, in spatial summation, the action potential within a neuron is a result of several action potentials of presynaptic cells. A presynaptic neuron is the one that fires the neurotransmitter to the postsynaptic neuron (receives neurotransmitter that triggers the action potential. Describe the gross external and cross-sectional anatomy of the spinal cord. - Answer- a. The spinal cord begins as a continuation of the medulla oblongata and terminates at about the second lumbar vertebrae in an adult. It contains cervical and lumbar enlargements that serve as points of origin for nerves and extremities. The tapered portion of the spinal cord is the conus medullaris from which arise the filum terminale and cauda equina from; 'Horsetail'. The spinal cord is partially divided into right and left sides by the anterior median fissure and posterior sulcus. Paired spinal nerves arise from a spinal segment spinal nerves and paths of communication between S.C. and body. Roots=2 parts of attachment that connect each spinal nerve to spinal cord 1) Posterior(Dorsal) Root=sensory nerve fibers conducts nerve impulses from periphery into spinal cord;each has swelling ganglion with cell bodies of sensory nerves form periphery 2. Anterior(Ventral) Root= motor neuron axons and conducts impulses from spinal cordto periphery. Removal of cerebrospinal fluid from the subarachnoid space is called a spinal tab. Describe the role of all components of a crossed extensor reflex. - Answer- a. The crossed extensor reflex is a reflex that occurs when a stimulus is applied to one limb, leading to an automatic contraction of the limb on the opposite side of the body. The components of the crossed extensor reflex are: i. Receptor: The receptor is the sensory nerve ending that detects the stimulus and sends a signal to the spinal cord. ii. Afferent neuron: The afferent neuron is the sensory neuron that carries the signal from the receptor to the spinal cord. iii. Interneuron: The interneuron is the neuron that