Unit 4 Homeostasis Answer Keys PDF

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Answer Key for Unit 4 Bio 12...

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Answer Key Unit 4 Homeostasis Answers to Unit Preparation Questions Assessing Student Readiness (Student textbook pages 338–40) 1. A: eyepiece (or ocular lens)—holds a magnifying lens through which the observer looks B: body tube—holds the eyepiece at the proper working distance from the objective lenses C: revolving nosepiece—holds and turns the objective lenses into viewing position D: objective lenses—in combination with the eyepiece lens, magnify the specimen under the microscope E: arm—supports the body tube and is used for carrying the microscope F: coarse-adjustment knob—focusses the image under low power G: fine-adjustment knob—sharpens the image under medium or high power H: stage (or stage clips)—supports the microscope slide (hold the slide in place) I: light source—directs light through the specimen J: diaphragm—controls the amount of light entering the body tube K: base—provides support for the microscope 2. E (arm) and K (base) 3. d

7. Chemical preservatives may give off fumes that are harmful to your eyes or may splash onto skin, clothing, or into eyes. Safety glasses, gloves, and lab aprons reduce the likelihood of exposure to these chemicals. 8. Anterior—toward the front end or head Posterior—toward the back end Proximal—close to a reference point Distal—far from a reference point (in anatomy, the reference point can be the centre of the body or the point of attachment of a limb or a muscle) 9. a 10. Sample answer: Blood cells need to have a large surface area for gas exchange. Cells in the digestive system need to have a large surface area for absorption of nutrients. 11. • Excretion—a function of the excretory system and the respiratory system; the process of removing liquid wastes from the body. • Elimination—a function of the digestive system; the process of removing solid wastes from the body. 12. b 13. Two organ systems such as: the nervous and muscular systems, the excretory and nervous systems, the respiratory and circulatory systems, or the digestive and circulatory systems. 14. The projections on neurons allow for signals to be received from different points and then transmitted through the nervous system back to the brain.

4. Dissecting instruments, such as scalpels, are very 15. e sharp. Cuts must be made away from the body to avoid 16. d cutting yourself if the scalpel slips. 17. excretory system 5. Both chemical and biological hazards are relevant to the disposal of dissection materials. Chemicals 18. d used to preserve specimens should be poured into 19. e appropriate chemical waste disposal containers. 20. The cell would have no control over molecules entering Biological specimens should be treated as biohazard or exiting. Toxins could enter freely, wastes would material (placed in biohazard bags and autoclaved). not be able to be contained in the vacuole, essential Teachers should consult MSDS sheets for chemical molecules would be able to leak out of the cell, and preservatives and any other information provided with concentration gradients could not be established preserved specimens. or maintained. 6. Notify your teacher immediately or have the nearest classmate do so. Rinse skin or eyes thoroughly with water for 15 min. Biology 12 Answer Key Unit 4 • MHR TR

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21. The amount of solute dissolved in a particular unit volume of solvent is known as the concentration of solute = concentration). that solute ( solvent 22. c

35. The concentration of hydrogen ions increases as pH decreases. 36. d range of acids

neutral

range of bases

23. Both move molecules or particles from one area to 1 2 3 4 5 6 7 8 9 10 11 12 another, generally across a membrane. They differ in stomach pure ammonia that active transport requires the input of energy for acid water movement to occur, while passive transport proceeds 38. b without the input of energy. Also, passive transport moves substances down a concentration gradient, 39. d from an area of higher concentration to an area of lower concentration. On the other hand, active Chapter 8 The Nervous transport moves substances against their concentration System and Homeostasis gradients, from an area of lower concentration to an area of higher concentration. 24. Diagrams should show an equal number of oxygen molecules on either side of the membrane. 25. passive transport 26. There would be no change in the distribution of glucose molecules, since glucose cannot freely diffuse across the cell membrane. However, water molecules would move into the cell by osmosis, from an area of higher concentration of water molecules outside the cell to an area of lower concentration of water molecules inside the cell. This would cause the cell to swell. 27. Assuming there are no channel proteins or carrier proteins present, there would be no movement of glucose molecules. 28. i. P ii. P iii. A iv. P 29. d 30. b 31. The concentration of the molecule, the size of the molecule, and the charge on the molecule. 32. Any three organelles with cellular membranes: chloroplasts, mitochondria, the endoplasmic reticulum, vacuoles, Golgi bodies, nucleus. 33. e 34. An ion is a charged particle formed when an atom or group of atoms loses or gains electrons. Answer should include any three of the following biologically important ions: Na+, K+, Ca2+, and H+.

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Answers to Learning Check Questions (Student textbook page 346) 1. cells, tissues, organs, organ systems

2. The tendency of the body to maintain a relatively constant internal environment. 3. A cycle of events in which a variable, such as body temperature, is continually monitored, assessed, and adjusted. 4. • Sensor—detects a change in the internal environment and sends a signal to a control centre • Control centre—sets the range of values within which a variable should be maintained, receives information from a sensor, and sends signals to an effector • Effector—receives signals from the control centre and responds, resulting in a change to an internal variable 5. The sensory receptors in the integumentary system communicate with the brain and spinal cord via nerves. 6. The stomach is composed of individual cells. Cells of the same type that perform a common function make up tissues, such as those that line the stomach. One or more tissues interact to form more complex structures called organs, such as the stomach. Several organs, such as the stomach and small intestine, organize structurally and functionally to form an organ system, such as the digestive system.

(Student textbook page 354) 7. The human nervous system can regulate tens of thousands of activities simultaneously. Its overall function is to collect information about the external conditions in relation to the body’s internal state, analyze it, and initiate appropriate responses to maintain homeostasis.

8. Sample answer: System

Structure

Function

Central nervous system

• Brain • Spinal cord

• The spinal cord carries messages from the body to the brain. • The brain analyzes and interprets these messages. • The brain then passes response messages through the spinal cord to target a structure, such as a muscle, gland, or neuron.

Peripheral nervous system

• Somatic nervous system • Autonomic nervous system

• The sympathetic nervous system controls organs in times of stress (fight or flight). • The parasympathetic nervous system causes a return to a state of rest and controls organs when the body is at rest.

9. Neurons are the basic structural and functional units of the nervous system. They are specialized to respond to physical and chemical stimuli, conduct electrochemical signals, and release chemicals that regulate various body processes. Glial cells support neurons. These cells nourish neurons, remove their wastes, and defend against infection. Glial cells also provide a supporting framework for all of the nervous-system tissue.

• Motor neurons—transmit information from the central nervous system to effectors (muscles, glands, or other organs). 12. The basic neural pathway used is a reflex arc. Sense organ (eye) detects the ball → initiates an impulse in a sensory neuron → activates spinal cord (interneuron) → activates a motor neuron → causes muscle to act to move the body out of the way of the ball This response is much like a withdrawal reflex, which is an involuntary response triggering a very fast response that moves the body out of harm’s way.

(Student textbook page 357) 13. This is the charge difference across the membrane in a resting neuron; usually -70 mV in unstimulated neurons, and is more negative on the inside. This provides energy for the generation of a nerve impulse in response to a stimulus. 14. • Some negatively charged substances, such as proteins and chloride ions (Cl-), are trapped inside the cell and unable to diffuse out through the selectively permeable cell membrane. • Sodium ions (Na+) and potassium ions (K+) cannot diffuse unaided from one side of the cell membrane to the other. Special membrane proteins, however, can use the energy of ATP to pump charged particles across the membrane. This sodium-potassium pump pumps out three sodium ions for every two potassium ions pumped into the cell, which results in an unequal distribution of positive charges on either side of the membrane. The build up of positive charges on the outside of the cell creates an electric potential. • Special transport proteins form ion-specific channels that allow potassium ions to diffuse down their concentration gradient and out of the cell. There are sodium ion channels as well, but, in a resting neuron, there are more open channels for potassium ions than for sodium ions. As a result, relatively more potassium ions diffuse out of the cell compared to the number of sodium ions diffusing in. This contributes to the build up of positive charges on the outside of the membrane.

10. Diagrams should be similar to the motor neurons shown in Figure 8.8 on page 351 of the student textbook. Students should label structures and identify functions: • Dendrites—receive impulses from other neurons and conduct impulses to the cell body • Cell body—site of the cell’s metabolic reactions and relay gatekeeper for nerve impulses sent down the axon • Axon—conducts impulses away from the cell body • Schwann cell—type of glial cell that wraps around the axon to form the myelin sheath, insulating the axon and speeding up impulses • Node of Ranvier—spaces between adjacent Schwann 15. • The shape of a carrier protein in the cell membrane cells involved in impulse transmission allows it to take up three sodium ions (Na+) on the 11. • Sensory neurons—gather information from sensory cytoplasmic side (inside) of the neuron. receptors and transmit those impulses to the central • ATP is split, and a phosphate group is transferred to nervous system. the carrier protein. • Interneurons—are found entirely within the central • A change in shape of the carrier protein causes nervous system. They act as a link between sensory the release of three sodium ions (Na+) outside and motor neurons. They process and integrate the cell. The altered shape permits the uptake of incoming sensory information and relay outgoing two potassium ions (K+) from the outside of the motor information. extracellular (outside) of the membrane. Biology 12 Answer Key Unit 4 • MHR TR

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• The phosphate group is released from the carrier protein. • A change in shape of the carrier protein causes the protein in the cell membrane to release the potassium ions (K+) into the cell. The carrier protein is once again able to take up three sodium ions (Na+). 16. A nerve impulse is a wave of action potentials that occurs along the length of a neuron, followed by a subsequent repolarization along the neuron. The impulse begins as a movement of ions across a localized area of the cell membrane, which reverses the polarity of the membrane potential in the area. This reversal of polarity results in depolarization in the neighbouring area of the membrane, which has the same effect on the next area of the membrane, and so on. In this way, the impulse propagates in one direction along the length of the neuron, with sodium ion channels and then potassium ion channels opening up in one area after another. 17. Until the neuron goes through the refractory period and is repolarized, it cannot be stimulated again. In other words, it cannot generate another action potential until it has been repolarized. 18. If a threshold potential is reached, large numbers of sodium ion channels simultaneously open, allowing for an influx of sodium ions and rapid depolarization of the membrane. This rapid change in the membrane potential initiates an action potential. If the sodium ion channels are blocked by tetrodotoxin, then the sodium ions will not flow into the neuron. Without this influx of sodium ions, an action potential will not be generated. Essentially, nervous impulses will not be transmitted and an individual may experience paralysis.

(Student textbook page 367) 19. • Brain—site of neural integration and processing, the brain receives messages, evaluates the information, and initiates outgoing responses to the body; plays a central role in maintaining homeostasis. • Spinal cord—links the brain and the peripheral nervous system. Sensory nerves carry messages from the body to the brain for interpretation and motor nerves relay messages from the brain to the effectors. Is also the primary reflex centre. 20. • Grey matter—is grey because it contains mostly cell bodies, dendrites, and unmyelinated neurons. • White matter—is white because it contains myelinated neurons that run together in tracts.

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21. By cerebrospinal fluid, soft tissue layers, and the spinal column, which consist of a series of backbones (vertebrae). 22. Diagrams should resemble Figure 8.19 on page 365 of the student textbook. 23. Protects the brain by preventing many toxins and infectious agents from leaving the blood. The bloodbrain barrier also supplies the brain with nutrients and oxygen. 24. The hypothalamus helps maintain homeostasis by • controlling blood pressure • controlling heart rate • controlling body temperature • controlling drives, such as thirst • coordinating actions of the pituitary gland, by producing and regulating the release of hormones

(Student textbook page 372) 25. Nerves that link the brain and spinal cord to the rest of the body, including the senses, muscles, glands, and internal organs. 26. Twelve pairs of myelinated cranial nerves and 31 pairs of myelinated spinal nerves. 27. Controls voluntary movement of skeletal muscles. Consists of sensory receptors in the head and extremities, nerves that carry sensory information to the central nervous system, and nerves that carry instructions from the central nervous system to the skeletal muscles. 28. Sympathetic nervous system (fight-or-flight response) and the parasympathetic nervous system (rest-anddigest response). 29. Stress or danger triggers the sympathetic nervous system. When triggered, it may increase the body’s heart rate and blood pressure. 30. This system prepares the body either to confront a dangerous situation (fight) or to flee from it (flight).

Answers to Caption Questions Figure 8.1 (Student textbook page 344): cardiac muscle cells → cardiac muscle tissue → heart → circulatory system Figure 8.3A (Student textbook page 346): The control centre sends messages to effectors causing constriction of blood vessels in the skin, which decreases heat loss; hormone release, which increases metabolism, generating heat; and repeated contraction of muscles (shivering), which creates heat.

Figure 8.14 (Student textbook page 357): If the sodium channels were unable to close, the neuron would not be able to repolarize. The membrane potential would stay positive instead of returning to its normal resting membrane potential, and the line on the graph would continue to rise. Figure 8.15 (Student textbook page 358): Increased velocity, 30 times faster than by continuous conduction.

• During lactation, the more a baby suckles, the more milk is produced and released. 7. All body systems must function properly in order to maintain a relatively constant internal environment (or homeostasis). 8. Sample answer:

Figure 8.22 (Student textbook page 368): occipital, frontal, and temporal Figure 8.23 (Student textbook page 370): Neurons in the muscles of the arms, shoulders, and fingers as well as those that maintain balance and posture.

Answers to Section 8.1 Review Questions (Student textbook page 348) 1. cells, tissues, organs, organ systems

Normal blood glucose levels

negative feedback and return to normal liver

low

stimulus

glycogen to glucose sensor

pituitary gland 2. Three systems involved in kicking a ball include the control centre skeletal, muscle, and nervous systems. The nervous increase hgH (brain) system has sensory receptors that communicate with 9. A positive feedback system because it is a mechanism the brain and spinal cord via nerve fibres. The nervous that brings about an ever greater change in the system gives instructions to specific muscle groups in same direction. your legs causing them to contract. The contracting muscles move the bones of the skeletal system. This 10. a. A negative feedback system between points A and C. coordinated series of events creates the kicking motion. It is keeping body temperature close to a set point.

3. a. sensor b. control centre c. effector 4. cooling of body temperature (stimulus) → sensor sends data to control centre → control centre receives information from sensor and compares it to the set point (set point 37°C) and sends response to effectors (blood vessels constrict, sweat glands are inactive) → negative feedback and return to normal 5. Venn diagrams should include: • Negative Feedback Only— a mechanism of homeostatic response by which the output of a system reverses a change in a variable, bringing the variable back to within normal range • Negative and Positive Feedback—a sensor; a control centre; effector(s) • Positive Feedback Only—a mechanism of homeostatic response by which the output of the system strengthens or increases the change 6. Two examples including: • Blood clotting helps to limit the amount of blood loss. • Hormones released during childbirth increase the strength of contractions of the uterus to help expel the baby.

b. A positive feedback system between points C and D. It is bringing about an ever greater change in temperature in the same direction. c. A negative feedback system between points D and E. It is preventing an even greater change in the same direction. (It is also possible that medications were administered that reduced a fever, or an infection that was causing the fever was brought under control.)

Answers to Section 8.2 Review Questions (Student textbook page 362) 1. A—central nervous system B—peripheral nervous system C—sensory pathways D—motor pathways E—somatic nervous system F—autonomic nervous system G—sympathetic nervous system H—parasympathetic nervous system 2. A message pathway of the nervous system. It is made up of many neurons grouped into bundles and surrounded by protective connective tissue. 3. Schwann are a type of glial cell that produce myelin by wrapping themselves around the axon. Biology 12 Answer Key Unit 4 • MHR TR

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4. Type of Neuron

Primary Function

Sensory neurons

• Gather information from sensory receptors and transmit impulses to the central nervous system

Interneurons (found entirely within central nervous system)

• Act as a link between sensory and motor neurons, process and integrate incoming sensory information, and relay outgoing motor information

Motor neurons

• Transmit information from the central nervous system to muscles, g...