BIO 235 Assignment 2 Questions With Complete Solutions | Latest Update 2026

BIO 235 Assignment 2 Questions With Complete Solutions | Latest Update 2026 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 is located within the spinal cord and receives the signal from the afferent neuron. It integrates the information and generates an appropriate reflex response. iv. Efferent neuron: The efferent neuron is the motor neuron that carries the signal from the spinal cord to the effector muscle. v. Effector muscle: The effector muscle is the muscle that receives the signal from the efferent neuron and contracts in response to the stimulus. The crossed extensor reflex is an important example of the spinal cord's ability to produce rapid and automatic responses to stimuli, even in the absence of input from the brain. By controlling the contraction of opposing muscles, the reflex helps to maintain balance and stability.Describe the structure and function of the blood-brain barrier and explain why the crushing injury of the occipital bone is often fatal. - answer-a. Selectively permeable membrane that regulates the passages of a multitude of large and small molecules into the microenvironment of the neurons. It is made up of capillary endothelial cells and basement membrane, neuroglial membrane and glial podocytes. Describe the structural and functional relationship between the hypothalamus and the pituitary gland. - answer-a. The hypothalamus is anatomically and functionally linked with the anterior and posterior pituitary gland. They are closely related because of the postal system of blood supply. The hypothalamus is directly connected to the posterior lobe of the pituitary gland by neurons. Hypothalamus regulates the function of the pituitary gland. Explain why the sympathetic division of the ANS has more widespread and longer-lasting effects than the parasympathetic division. - answer-a. A single sympathetic preganglionic fiber has many axon collaterals (branches) and synapses with 20 or more postganglionic neurons, whereas a parasympathetic preganglionic neurons synapses with only 4 or 5 postganglionic neurons. The sympathetic neurotransmitter, norepinephrine is broken down more slowly than acetylcholine, so postganglionic cells are stimulated longer. The sympathetic division also stimulates release of catecholamines (mostly epinephrine) from the adrenal medulla, thus enhancing the sympathetic effects via the endocrine system. Also, more visceral effectors have receptors for catecholamines (norepinephrine and epinephrine) than for acetylcholine. Compare and contrast the overall responses of the sympathetic and parasympathetic divisions, including specific effects at various visceral effectors. - answer-a. The sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS) are the two parts of the autonomic nervous system (ANS) regulation that is under involuntary control. The ANS is in charge of regulating the visceral motor systems that control the coordinated homeostasis of the various organs of the body. b. The cell body of the neuron of the ANS originates in the central nervous system (CNS) which innervates the ganglion of the autonomic system situated near the target organ. The second cell body of the neuron originates from ganglion which finally innervates the visceral organs. c. The sympathetic division is responsible for the fight or flight responses of the body. Its regulation results in an increased heart rate, sweating, pupillary dilation, and increased blood glucose levels. The neurotransmitters that come into play during the sympathetic modulation are adrenaline and acetylcholine. d. The parasympathetic division is in control of the rest and relaxation of vegetative functions of the body such as decreased heart rate increased digestive functions, and pupillary constriction. The neurotransmitters that are involved in the parasympathetic modulation is acetylcholine.A viral infection has damaged a patient's tectospinal tract. What signs of this damage probably helped the physicians diagnose the problem? - answer-a. The tectospinal tract is an extrapyramidal, or indirect, motor pathway. It conveys nerve impulses from the superior colliculus to contralateral skeletal muscles that move the head and eyes in response to visual stimuli. One sign of such damage would be the inability of the patient to turn his head toward a flashing light. The patient would also be unable to follow movements of the physician's finger with his eyes. The patient would probably be unable to read words scrolling across a screen. Each of these deficits relates to the inability to move the head or eyes in response to visual stimuli and would alert the physician to damage of the tectospinal tract. List the six types of sensory receptors, as classified based on the type of stimulus they detect, and describe the stimuli each responds to. Name the three types of sensory receptors categorized based on their location, identify the origin of stimuli that activate them, and describe the nature of the stimuli that cause their excitation. - answer-a. Sensory receptors can be classified based on the type of stimulus they detect and based on their location. Classification based on the type of stimulus detected: i. Photoreceptors: respond to light stimuli ii. Thermoreceptors: respond to temperature stimuli iii. Mechanoreceptors: respond to pressure or movement stimuli iv. Chemoreceptors: respond to chemical stimuli v. Nociceptors: respond to painful or harmful stimuli vi. Electromagnetic receptors: respond to electromagnetic stimuli b. Classification based on location: i. Free nerve endings: are located throughout the skin and mucous membranes and respond to stimuli such as temperature and pressure. ii. Root hair plexuses: are located near hair follicles and respond to slight changes in movement. iii. Pacinian corpuscles: are located deeper in the skin and respond to pressure. c. The stimuli that activate these receptors can originate from external sources, such as touch or temperature, or from internal sources, such as changes in blood pressure or levels of certain chemicals in the body. The nature of the stimuli that cause the excitation of sensory receptors can range from light pressure or movement to strong pressure or extreme temperature changes.Describe the process of image formation on the retina, and contrast light and dark adaptation. Include the role of the rods and cones in your description. - answer-a. The cornea and lens of an eye act together to form a real image on the light-sensing retina, which has its densest concentration of receptors in the fovea and a blind spot over the optic nerve. The power of the lens of an eye is adjustable to provide an image on the retina for varying object distances. Layers of tissues with varying indices of refraction in the lens are shown here. However, they have been omitted from other pictures for clarity. b. An image is formed on the retina with light rays converging most at the cornea and upon entering and exiting the lens. Rays from the top and bottom of the object are traced and produce an inverted real image on the retina. The distance to the object is drawn smaller than scale. c. With dark adaptation, we noticed that there is progressive decrease in threshold (increase in sensitivity) with time in the dark. With light adaptation, the eye has to quickly adapt to the background illumination to be able to distinguish objects in this background. d. Rods are more sensitive to light and so take longer to fully adapt to the change in light. Rods, whose photopigments regenerate more slowly, do not reach their maximum sensitivity for about two hours. Cones take approximately 9-10 minutes to adapt to the dark. e. Both cones and rods participate in dark adaptation, slowly increasing their sensitivity to light in a dim environment. Cones adapt faster, so the first few minutes of adaptation reflect cone-mediated vision. Differentiate between vertical and horizontal linear acceleration and deceleration. Describe the inner ear structures involved in receiving and transducing sensations involved in maintaining both types of equilibria. - answer-a. The linear acceleration and deceleration along the vertical and horizontal planes are sensed by the inner ear. The following are the differences between the vertical and horizontal linear acceleration and deceleration: b. Vertical linear acceleration and deceleration: i. It is the movement of the head along the vertical plane that is detected by the sensitive vestibular organ ii. Saccule is the otolith organ that senses the vertical linear acceleration and deceleration movement of the head iii. In this plane, the saccule is the most sensitive to vertical head tilt movements as it is oriented vertically iv. For instance, it responds to the movement that is experienced while standing inside a moving elevator c. Horizontal linear acceleration and deceleration: i. It is the movement of the head along the horizontal plane that is detected by the sensitive vestibular organii. The utricle is the otolith organ that senses the horizontal linear acceleration and deceleration movement of the head. iii. In this plane, the utricle is the most sensitive to horizontal head tilt movements as it is oriented horizontally iv. For instance, it responds to the movement that is experienced while sitting in a moving car d. The sensory apparatus that enables the inner ear to maintain the body equilibrium based on the sensory inputs is the vestibular system. The vestibular apparatus processes the sensory information to coordinate the head and eye movements. The semi-circular canals assess the rotational acceleration and deceleration while the linear acceleration and deceleration (function of gravitational force) is assessed by the utricle (horizontal movements) and saccule (vertical movements). Under the influence of the static equilibrium (linear movements) both the maculae are triggered by the forces acting between the otolithic membrane Explain the mechanism by which a deficiency of gonadotropin-releasing hormone (GnRh) will lead to infertility in both a male and a female. - answer-a. Gonadotropin-releasing hormone (GnRH) is a hormone produced by the hypothalamus that stimulates the production and release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by the pituitary gland. These hormones, in turn, regulate the production of hormones (testosterone in males and estrogen in females) and the maturation of gametes (sperm in males and ova in females) in the gonads (testes in males and ovaries in females). A deficiency of GnRH will lead to infertility in both males and females because it disrupts the hormonal balance necessary for reproduction. In males, a lack of GnRH can result in decreased levels of testosterone, which is necessary for sperm production. This can lead to decreased sperm count and reduced sperm motility, making it difficult for sperm to fertilize an egg. In females, a deficiency of GnRH can prevent the release of FSH and LH, leading to a disruption in the menstrual cycle and infertility. FSH is necessary for the growth and development of follicles, which contain the ova, while LH triggers ovulation and the production of progesterone, which is necessary for maintaining a pregnancy. A deficiency of GnRH can also lead to a decrease in estrogen levels, which is necessary for the thickening of the endometrial lining and preparing the uterus for implantation of a fertilized egg. In conclusion, GnRH is an important hormone that plays a crucial role in regulating the reproductive functions in both males and females. A deficiency of GnRH can lead to infertility by disrupting the hormonal balance necessary for normal reproductive processes.