Gen. Biology Midterms Coverage PDF

COVERAGE FOR THE MIDTERMS Sensory Receptors & Mechanisms in Plants Sensory Receptors & Mechanisms in Animals Sensory and Motor Mechanisms in Humans Homeostasis (Nervous and Endocrine) Negative Feedback Mechanisms Positive Feedback Mechanisms  Sensory and Motor Mechanis...

COVERAGE FOR THE MIDTERMS Sensory Receptors & Mechanisms in Plants Sensory Receptors & Mechanisms in Animals Sensory and Motor Mechanisms in Humans Homeostasis (Nervous and Endocrine) Negative Feedback Mechanisms Positive Feedback Mechanisms  Sensory and Motor Mechanisms in Humans  Can you think of any activities that require you to use your five senses? 3 Cooking is an example of an activity that requires the use of all five senses. 4  The human nervous system is highly similar to the nervous system of other mammals. Among the vertebrate groups, mammals have the most complex nervous systems. 5  Divisions of the Nervous System Aside from the central and peripheral divisions of the nervous system, it can also be classified based on the type of control exhibited. 6  Divisions of the Nervous System Divisions Based on Control Somatic Nervous The nervous system can also be System classified based on control: ○ The somatic nervous Autonomic system; and Nervous ○ the autonomic nervous System system. 7  Divisions of the Nervous System The Somatic Nervous System Somatic Nervous The somatic nervous system System controls the activities of the skeletal muscles. Autonomic Nervous System 8  Divisions of the Nervous System Neurons extend from the spinal cord to the muscles. This allows voluntary and involuntary nervous control of these muscles. 9  Divisions of the Nervous System The Autonomic Nervous System Somatic Nervous This division regulates the System involuntary processes of various internal organs. Autonomic Nervous System 10  Divisions of the Nervous System The sympathetic division of the autonomic nervous system regulates the fight-or-flight response and prepares the body for high amounts of activity. 11  Divisions of the Nervous System The parasympathetic division of the autonomic nervous system regulates the rest-and-digest response and lowers energy expenditure. 12  Divisions of the Nervous System The Autonomic Nervous System Somatic Nervous This division regulates the System involuntary processes of various internal organs. Autonomic Nervous System 13  The five senses allow us to collect information from the environment. 14  The Five Senses The five senses each have specialized structures to allow them to collect information from the environment to send to the brain for processing. 15 The Five Senses Sight Sight Smell The eyes are the photoreceptors that humans Hearing have. Touch Taste 16  The Five Senses The major parts of the eye are the cornea, lens, retina, iris, and pupil. 17  The Five Senses The amount of light that enters the eye is controlled by the iris and the pupil. 18  The Five Senses The retina contains the photoreceptors of the eye. These are the rods and the cones. 19  The Five Senses The optic nerve connects the eyes to the brain. 20 The Five Senses Sight Smell Smell The sensory structure for smell, which is the olfactory Hearing epithelium, can be found inside the nose. Touch Taste 21  The Five Senses The olfactory epithelium contains chemoreceptors that can detect the presence of substances in the air. 22 The Five Senses Sight Hearing Smell The ears catch and sense vibrations in the environment. Hearing These vibrations are what we perceive as sound. Touch Taste 23  The Five Senses The parts of the outer ear are responsible for catching vibrations. These are eventually passed on to the middle ear and the inner ear. 24  The Five Senses The outer ear is responsible for catching sounds. 25  The Five Senses The malleus, incus, and stapes vibrate due to the sounds transmitted to them by the outer ear. They then transmit these vibrations to the inner ear. 26  The Five Senses The spiral organ of Corti in the cochlea is responsible for detecting sounds and the information is then transmitted to the brain using the auditory nerve. 27 The Five Senses Sight Touch Smell Mechanoreceptors that respond to touch are present in Hearing the skin. Touch Taste 28  The Five Senses Different receptors in the skin can detect different types of pressures associated with touch. 29 The Five Senses Sight Taste Smell The chemoreceptors that can detect substances in food are Hearing found in the tongue. Touch Taste 30  The Five Senses When gustatory cells in the taste buds detect particular chemicals in the tongue, they release neurotransmitters that help in relaying these signals via the nerve fibers. 31 Homeostasis Baseball is one of the most intense sports. It involves stability so players need to be in the peak of physical state to be able to play it efficiently. 33 Being a runner on second base in a baseball game has a stable place to stand. He watches the next pitch for the opponent and is always ready for action. 34 Our bodies are like this. The body exists in a stable state, but it is always ready for action or response when that stability becomes disturbed. 35 35 What are the different conditions that affect the body’s stability? 36 How does homeostasis maintain normal bodily function? 37  Overview of Homeostasis Cells are surrounded by fluids Maintenance of the cell’s fluid = sustain normal functions Most cells in the body are surrounded by fluids. The maintenance of these fluids is important to sustain the function of the cell. 38  Overview of Homeostasis Temperature Variables Volume Chemical substances These variables can change because of some external factors. The response of the body to these variables in order to maintain the normal conditions is part of homeostasis. 39 Overview of Homeostasis Homeostasis (homeo = the same + stasis = standing) It is the existence and maintenance of a relatively constant environment within the body. 40 Overview of Homeostasis Homeostasis Homeostasis involves balancing body temperature, water levels, salt levels, maintaining pH, and many others. 41 Overview of Homeostasis Body temperature is a variable that needs to be maintained in homeostasis. It is set around an ideal range, which can increase or decrease around a set point. 42  Overview of Homeostasis All organ systems contribute to homeostasis Although all organisms must carry out some degree of homeostasis, animals vary in the degree to which they Fishes must be able to retain or release salt and water in response regulate these internal to the concentration of salt in the variables. external environment. 43  Homeostatic Control System Sensor or Receptor Control center Effector Monitors the value of a variable Functions Detects changes in the internal or external environment which are called stimulus (stimuli). 44  Homeostatic Control System Sensor or Receptor Control center Effector baroreceptors for detecting blood pressure changes Examples peripheral chemoreceptors which detect changes in blood pH 45  Homeostatic Control System Sensor or Receptor Control center Effector Establishes the set-point around which the variable is maintained Functions Receives information from the sensors and initiates the response to maintain homeostasis 46  Homeostatic Control System Sensor or Receptor Control center Effector The hypothalamus and other parts of the brain may act as control centers, depending on the process Examples involved. For blood pressure, the control center is in the medulla. 47  Homeostatic Control System Sensor or Receptor Control center Effector Can change the value of the variable Functions Any organ or tissue that collects information from the integrating center and acts to create changes needed to maintain homeostasis 48  Homeostatic Control System Sensor or Receptor Control center Effector In relation to blood pressure: Heart in which the blood pressure depends on its contraction. Examples In relation to blood pressure: Kidney, which retains water if blood pressure is too low. 49 If the body temperature is below the setpoint, muscles shiver to generate heat while the constriction of blood vessels helps the body retain heat. Identify the three components of the homeostatic system in the given situation. 50  Homeostatic System Pathway Communication is an important component of homeostasis. This communication occurs primarily through nervous and endocrine system. 51 Homeostatic System Pathway The homeostatic system pathway is composed of efferent and afferent pathways. These pathways are controlled by the nervous and endocrine systems. 52  Homeostatic System Pathway Afferent Pathway Receptor Communication Control center If the communication flows from the receptor toward the control center, this is termed as an afferent pathway. 53  Homeostatic System Pathway Efferent Pathway Control center Communication Effector If the information flows from the control center toward the effector, this is termed as an efferent pathway. 54  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: Signals (stimulus) Central Nervous System Afferent neurons 55  Homeostatic Control System Sensor or Receptor Control center Effector baroreceptors for detecting blood pressure changes Examples peripheral chemoreceptors which detect changes in blood pH 56  Homeostatic Control System Sensor or Receptor Control center Effector Establishes the set-point around which the variable is maintained Functions Receives information from the sensors and initiates the response to maintain homeostasis 57  Homeostatic Control System Sensor or Receptor Control center Effector The hypothalamus and other parts of the brain may act as control centers, depending on the process Examples involved. For blood pressure, the control center is in the medulla. 58  Homeostatic Control System Sensor or Receptor Control center Effector Can change the value of the variable Functions Any organ or tissue that collects information from the integrating center and acts to create changes needed to maintain homeostasis 59  Homeostatic Control System Sensor or Receptor Control center Effector In relation to blood pressure: Heart in which the blood pressure depends on its contraction. Examples In relation to blood pressure: Kidney, which retains water if blood pressure is too low. 60 If the body temperature is below the setpoint, muscles shiver to generate heat while the constriction of blood vessels helps the body retain heat. Identify the three components of the homeostatic system in the given situation. 61  Homeostatic System Pathway Communication is an important component of homeostasis. This communication occurs primarily through nervous and endocrine system. 62  Homeostatic System Pathway Afferent Pathway Receptor Communication Control center If the communication flows from the receptor toward the control center, this is termed as an afferent pathway. 63 Homeostatic System Pathway The homeostatic system pathway is composed of efferent and afferent pathways. These pathways are controlled by the nervous and endocrine systems. 64  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: Signals (stimulus) Central Nervous System Afferent neurons 65  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: Central Nervous System Body response Efferent neurons 66  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: also called motor neurons responsible for carrying signals away from CNS send signals for motor Efferent neurons response 67  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: also called sensory neurons originate in the periphery of the body responsible for sensing a stimulus Afferent neurons 68  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: Central Nervous System Body response Efferent neurons 69  Homeostatic System Pathway Neurons associated with the signals that are carried in the pathways: also called motor neurons responsible for carrying signals away from CNS send signals for motor Efferent neurons response 70 Homeostatic System Pathway The afferent and efferent neurons can be found on the spinal cord. These neurons both give signals to the brain to give appropriate responses for a sensed stimulus. 71 How can one differentiate between the afferent pathway and the efferent pathway? 72 In an afferent pathway, the sensory neurons send information about the stimulus to the central nervous system. In an efferent pathway, the motor neurons carry signals away from the central nervous system to initiate an action. 73 You can also simply remember Afferent = Arrives since the information arrives at the central nervous system. On the other hand, Efferent = Exits, since the information exits the central nervous system. 74 Identify the term being described by the following statements 1. It refers to the existence and maintenance of a constant environment within the body. 2. These are the changes that the body responds to. 3. This refers to the ideal set of values which will be the basis of maintaining a certain variable. 75 Briefly explain the possible consequences should the following events take place. 1. The body is exposed to very high or very low temperatures. 2. The body is unable to respond to high or low temperatures. 3. Not all organs are involved in the maintenance of homeostasis. 76  Let’s Sum It Up! Homeostasis (homeo = the same + stasis = standing) is the existence and maintenance of a relatively constant environment within the body. Homeostatic mechanisms are performed by the body to maintain the body’s ideal normal value or set point. 77  Let’s Sum It Up! As long as the body temperatures and other essential bodily processes remain within the normal range, homeostasis is maintained. The homeostatic control system has at least three interdependent components for the variable being regulated: sensor or receptor, control center, and effector. 78  Let’s Sum It Up! Communication that flows from the receptor toward the control center is termed as an afferent pathway. Information that flows from the control center toward the effector, is termed as an efferent pathway. 79  Let’s Sum It Up! Afferent neurons are also called sensory neurons that are responsible for sensing a stimulus. Efferent neurons are also called motor neurons, that are responsible for carrying signals away from the central nervous system in order to initiate an action. 80 Graphical representation of homeostasis 81 How do the components of the homeostatic control system function to maintain homeostasis? 82 Negative Feedback Mechanisms All products, when newly-released to the market, receive feedback from consumers. 84 This feedback is any information gained from consumer reviews regarding the product. 85 Similar to this, our body also has feedback mechanisms that function in somewhat the same way. 86  Changes and stimuli can be likened to consumer reviews which the body needs to respond to. If there is a change in the systems of our body, the process of feedback triggers certain results. This change can be an increase or decrease to the system to bring it back to its normal state. How do these systems work? 87 What is the natural feedback or response of our body when its normal state is disrupted? 88 How do negative feedback mechanisms function in the body? 89  Negative Feedback Mechanisms Negative mechanisms are dubbed as “negative” because any deviation from the set point is met by a response that helps in reducing the change that was The negative feedback loop consists of the detected. stimulus, sensor, control center, and the effector. 90 Home Heating System Negative Feedback Mechanisms The thermostat contains a thermometer, which is a sensor that detects when the room temperature is above or below the set point. 91 Home Heating System Negative Feedback Mechanisms The thermostat also contains a control center; it turns the furnace off when the room is warm. 92 Home Heating System Negative Feedback Mechanisms When the furnace is off, the room cools a bit. 93 Home Heating System Negative Feedback Mechanisms When the furnace is on, the room warms a bit. 94 How can a home likened to the body regarding the feedback mechanism shown in home heating systems? 95  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation Hypothalamus is a part of the brain where the sensor and the control center for body temperature are located. 96  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation The mechanism when the temperature is below normal 97  Examples of Negative Feedback Mechanisms Temperature Osmotic Glucose Level Blood Pressure Menstrual Regulation Balance Regulation Regulation Cycle The mechanism when the temperature is above normal 98  Examples of Negative Feedback Mechanisms Temperature Osmotic Glucose Level Blood Pressure Menstrual Regulation Balance Regulation Regulation Cycle The mechanism when the water level of the body is critically low 99  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation The mechanism when the level of water in the bodily fluids is too high 100  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation The mechanism when blood sugar levels are too high 101  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation The mechanism when blood sugar levels are too low 102  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation The mechanism when blood pressure is above normal 103  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation The mechanism when blood pressure is below normal 104  Examples of Negative Feedback Mechanisms Temperatur Glucose Blood Osmotic Menstrual e Level Pressure Balance Cycle Regulation Regulation Regulation A high level of GnRH produces LH and FSH, which then produces high levels of estrogen. If the level of estrogen in the body is high, the production of GnRH will be inhibited. 105 What is the role of pituitary glands in the different processes involved in negative feedback mechanisms? 106 Identify terms being described by the following statements. 1. Signals are sent to this component and it initiates an action to bring conditions back to normal. 2. This structure is where information is sent to in the efferent pathway. 3. It is known as the normal range which forms the basis for homeostatic stability. 107 Provide the possible consequence, should the following events take place. 1. The temperature decreases below the normal range. 2. The osmoreceptors detected that there is a high amount of fluid in the body. 3. The body does not convert enough glucose. 4. The receptors in the blood vessels detected an increase in the blood pressure. 5. There is a high level of estrogen in the body. 108  Our body’s systems are regulated by negative feedback mechanisms, which functions to maintain homeostasis. This feedback maintains the variation within a normal range. It is dubbed as negative since the changes are met with a response that decreases their magnitude. 109  The sensor and the control center for body temperature are located in a part of the brain called the hypothalamus. 110  When the body temperature is above normal, the control center directs the blood vessels of the skin to dilate. The result is that more blood flows near the surface of the body, where heat can be lost to the environment. 111  Water intake is balanced out by processes like urination, perspiration, defecation, and more. The blood sugar level is a measure of how effectively the body uses glucose, which may vary throughout the day. Insulin and glucagon, which are both hormones secreted by the pancreas, keep the level of blood sugar within a healthy range. 112  The maintenance of blood pressure is another example of a negative-feedback mechanism. The menstrual cycle and puberty of females are controlled by the hormones estrogen, luteinising hormone (LH), and follicle stimulating hormone (FSH). 113 Graphical representation of negative feedback mechanisms 114 How does the negative feedback mechanism function when there is an imbalance in the homeostatic state of the body? 115 Positive Feedback Mechanisms You, as a student, may already be used to the need to submit requirements on a regular basis. 117 As a result, work tends to get more difficult as more and more requirements pile up. Has this ever happened to you? How did you respond? 118 Our body also experiences the same scenario if the balance maintained by homeostasis is disturbed, which can be remedied by positive feedback mechanisms. 119 How does the positive feedback mechanism function in the human body? 120  Positive Feedback Mechanism Positive Feedback GREATER change Mechanisms 121  Positive Feedback Mechanism Positive Feedback away from a Mechanisms balanced state 122 Positive Feedback Mechanism greater deviation from “positive” a normal value 123 Positive Feedback Mechanism Positive Feedback Mechanisms Sensor Control center Effector 124  Positive Feedback Mechanism A positive feedback loop has roughly the same components as a negative feedback loop. However, these two feedbacks have different effects when they occur in the body. 125  Examples of Positive Feedback Mechanism Childbirth Once the process of childbirth begins, it must progress consistently until the baby is born to ensure the safety of both the baby and the mother. 126  Examples of Positive Feedback Mechanism Childbirth first contraction of labor (stimulus) pushes the baby towards the cervix 127  Examples of Positive Feedback Mechanism Childbirth receptors signals brain (control center) stronger contractions pituitary gland in the uterus (effector) releases oxytocin 128  Examples of Positive Feedback Mechanism Childbirth push the baby down to the greater stretching of birth canal the cervix 129  Examples of Positive Feedback Mechanism Childbirth uses a positive feedback mechanism in response to the need for more contractions to release the baby. This happens with the aid of the hormone oxytocin. 130  Examples of Positive Feedback Mechanism Lactation Lactation involves a positive feedback loop that ensures continuous milk production. Breastfeeding stimulates milk production. 131  Examples of Positive Feedback Mechanism Lactation suckling of infant hypothalamus 132  Examples of Positive Feedback Mechanism Lactation anterior pituitary s e c r e t e s prolactin 133  Examples of Positive Feedback Mechanism Lactation secretion of prolactin secretion of oxytocin release of milk 134 Examples of Positive Feedback Mechanism The suckling action of an infant triggers the production of more milk. More production of milk leads to more lactation. Lactation uses positive feedback mechanisms to ensure continuity of milk production. 135  Examples of Positive Feedback Mechanism Blood Clotting damaged vessel platelets flock to the injured site. wound plugged up 136 Examples of Positive Feedback Mechanism platelets release more attracted chemicals platelets to the site plugged wound, platelets pile up bleeding stops until clot is formed 137 Examples of Positive Feedback Mechanism Blood clotting also uses positive feedback mechanisms. The chemicals released from the damaged vessel attract more platelets until it forms enough clot to stop the bleeding. 138 Examples of Positive Feedback Mechanism Inflammation increased blood flow increased redness swelling pain temperature 139  Examples of Positive Feedback Mechanism Inflammation accelerates delivery increased blood flow of WBCs redness and warmth more oxygen and nutrients 140  Examples of Positive Feedback Mechanism Inflammation uses positive feedback mechanisms by increasing the blood flow to fasten the delivery of white blood cells to the damaged tissue or cell. 141  Positive feedback is a mechanism that brings about a continually greater change in the same direction. The first contraction of labor is the stimulus pushes the baby towards the cervix. This triggers positive feedback until the baby is born. 142  The suckling action of an infant signals the anterior pituitary by the hypothalamus to secrete prolactin. Breastfeeding stimulates milk production. Estrogen level rises because of the hormonally active cells within the follicle. This leads to positive feedback with FSH and LH. 143  Once a vessel is damaged or any wound that causes bleeding, the platelets will cling to the injured site. These platelets release chemicals that attract more platelets. 144  Inflammation is characterized by increased blood flow. An increase in the blood flow accelerates delivery of the white blood cells that help fight against invading foreign substances. 145 Graphical representation of positive feedback mechanism 146 Sensory Receptors and Mechanisms in Plants Plants respond to various factors in their external environment, such as light, water availability, and different events that cause stress. 148 Plants have also developed various physical and chemical defenses to deter herbivores from consuming their parts. 149 Some plants have also adapted to nutrient-poor environments by trapping and digesting small insects or mollusks. 150 What are the mechanisms by which plants respond to various environmental stimuli? 151 Introduction to Plant Responses Some Factors that Initiate Responses 152 General Response Mechanisms Stimuli are factors that trigger responses in organisms. This initiation of responses is best demonstrated by human sensory systems. 153  Responses Through Hormones These chemical messengers No special glands produce are released by tissues in them as they can synthesized trace or small quantities. by any plant cell or tissue. Plant Hormo nes These molecules can be They influence various transported into distant biological processes such as targets via vascular tissues. growth, development, and flowering. 154  Responses Through Hormones Hormone Description Auxins play a role in plant growth, cell expansion, and inducing cell Auxins division in various plant tissues. Cytokinins play a role in cell division. They also play a role in cell Cytokinins differentiation, aging, and the maintenance of meristems. Gibberellins also promote growth and are notable in their role in the Gibberellins elongation of plant stems. They are also known to stimulate flower development and leaf senescence. Ethylene plays a role in the ripening of fruits and in the growth and Ethylene aging of plants. This hormone is also responsible for initiating various responses against stress. 155  Common Plant Stimuli and Responses Light Gravity Touch Water Phytochromes are used to detect or sense the presence of red light. Cryptochromes and phototropins detect or sense blue light. Completely submerged aquatic plants, similar to terrestrial ones, rely on photoreceptors to detect and harness light energy. 156 Common Plant Stimuli and Responses Light Gravity Touch Water 157 Common Plant Stimuli and Responses Light Gravity Touch Water Submerged Plants Forest Floor Plants 158  Common Plant Stimuli and Responses Light Gravity Touch Water Submerged Plants Forest Floor Plants Mostly rely on blue light Mostly rely on red light Red light is attenuated by water, Less shaded areas of the forest while blue can penetrate more floor have more red light Thus, submerged aquatic plants Thus, forest floor plants rely more rely more on blue photoreceptors on red photoreceptors 159  Common Plant Stimuli and Responses Light Gravity Touch Water Light-Dependent Responses in Plants Photomorphogenesi s This response refers to the development and growth of plants due to the presence, type (or wavelength), or intensity of light. An etiolated Hyacinthoides hispanica 160  Common Plant aStimuli and Responses Light Gravity Touch Water Light-Dependent Responses in Plants Photomorphogenesi s Thus, some plants have altered growth when grown in the dark--they become etiolated, making them slender and white. An etiolated Hyacinthoides hispanica 161  Common Plant Stimuli and Responses Light Gravity Touch Water Light-Dependent Responses in Plants Photoperiodism This response refers to how plants use light to track time and trace temporal changes. Euphorbia pulcherrima only blooms when day length is less than 12 hours. 162  Common Plant Stimuli and Responses Light Gravity Touch Water Light-Dependent Responses in Plants Photoperiodism Some plants sense that the appropriate light for the current season is present, so they will start Euphorbia pulcherrima only blooms when to produce flowers. day length is less than 12 hours. 163  Common Plant Stimuli and Responses Light Gravity Touch Water Light-Dependent Responses in Plants Phototropism This refers to the orientation of plants as a response to light. In most cases, plants grow towards a light source. The orchid Phalaenopsis sp. orients itself where sunlight is present. 164  Common Plant Stimuli and Responses Light Gravity Touch Water Light-Dependent Responses in Plants Phototropism This response may be positive or negative depending on whether plants orient themselves to or away from a light source. The orchid Phalaenopsis sp. orients itself where sunlight is present. 165  Common Plant Stimuli and Responses Light Gravity Touch Water Gravitropism refers to the directional response of plant parts to gravity. 166  Common Plant Stimuli and Responses Light Gravity Touch Water The shoot exhibits negative gravitropism by growing against the direction of the pull of gravity. The root exhibits positive gravitropism by growing similar to the direction of the pull of gravity. 16 167 Common Plant Stimuli and Responses Light Gravity Touch Water The hormone indole-3 acetic acid is responsible for the normal growth of shoot and root systems. 16 168  Common Plant Stimuli and Responses Light Gravity Touch Water Thigmotropism Thigmonasty Thigmomorphogenesis Directional response of plants Response to stimulus Growth changes due to the to mechanical stimuli regardless of the direction constant mechanical stimulus 169  Common Plant Stimuli and Responses Light Gravity Touch Water Water-Dependent Responses in Plants Stomatal Opening The opening and closing of stomata depends on the increase or decrease in the water potential of the guard cells. A stoma in a tomato leaf 170  Common Plant Stimuli and Responses Light Gravity Touch Water Water-Dependent Responses in Plants Stomatal Opening Thus, plants can regulate the amount of water vapor that is lost when the stomata of their leaves remain open. A stoma in a tomato leaf 171  Common Plant Stimuli and Responses Light Gravity Touch Water Water-Dependent Responses in Plants Seed Germination Water intake by the developing seed activates gibberellin, which, in turn, activates amylase. A germinating seed 172  Common Plant Stimuli and Responses Light Gravity Touch Water Water-Dependent Responses in Plants Seed Germination Consequently, the amylase initiates the breakdown of starch, which stimulates the seed germination. A germinating seed 173  A stimulus from the environment can elicit various forms of responses within an organism. Plants are able to respond to environmental stimuli through the use of substances known as hormones, as well as through different cellular structures and receptors. 174  There are many classes of hormones, and each of these has specific functions in plants, which may depend on the location of action or environmental conditions. Common stimuli that plants constantly respond to are water, touch, gravity, and light. 175 ○ Light reception influences not only the photosynthesis but also the patterns of growth, flowering, and appearance of plants. ○ Detection of the pull of gravity influences the rate of growth of the root and shoot systems. 176 ○ Water levels in plants generally affect the turgidity of the guard cells. Generally, this relationship influences the rate of water loss in plants through stomata. 177 ○ Touch reception in plants may influence their direction or pattern of growth, as well as rapid reactions that do not rely on the direction of the stimulus. 178 Sensory and Motor Mechanisms in Animals Snakes feed in frequencies that vary with their age, sex, and size. Some of them feed twice a week, while others once every other week. 180 Snakes utilize multiple senses to locate their potential prey. For example, they can detect the presence of chemicals in air. Also, they can detect the heat emitted by their target through infrared vision. 181 Animals and humans have various biological features and means to detect changes in their internal and external environments. 182 How do animals sense and relay sensory information from their environments? 183  Nerve Cells Most important functional units of the nervous system Transmit, receive, and process nervous information Functional classes include sensory and motor neurons 184 Nerve Cells 185  Diversity in Nervous System Complexity The nervous system of higher animals is divided into the central and peripheral nervous systems. 186 Sensory Structures Sensory neurons are found in sensory 1 structures that detect or sense stimuli. Also called afferent neurons, they 2 are associated with particular receptors. They relay information into the 3 central nervous system for processing. 4 Their cell bodies are located in the brain or the spinal cord. 187  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Nociceptors detect pain stimuli, which can potentially harm the body or lead to potentially serious damages in tissues. 188  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Mechanoreceptors detect various forms of mechanical stimuli, such as sound waves, tactile sensations, and gravity. 189  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Various fish species have statoliths, which enable them to properly orient themselves in the aquatic medium. 190  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Photoreceptors are able to detect the presence or absence, wavelengths, and intensities of light. 191  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Photoreceptors in the mantle of giant clams and other bivalve species help them detect shadows of passing predators. 192  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Chemoreceptors, such as olfactory receptors and taste buds, help detect the presence of chemicals in air and food. 193  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors The Jacobson’s organ in snakes help them detect various Thermoreceptors substances through their tongue that catches particles in air. 194  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors Osmoreceptors sense changes in the concentration of substances or changes in the osmotic pressure of fluids. 195  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Osmoreceptors Thermoreceptors The hypothalamus consists of osmoreceptors that can determine blood osmolality to trigger thirst when hydration is needed. 196  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Thermoreceptors sense Osmoreceptors specific temperatures or changes in temperature in internal and external Thermoreceptors environments. 197  Sensory Receptors Nociceptors Mechanoreceptors Photoreceptors Chemoreceptors Snakes have pit organs, Osmoreceptors which help them detect the presence of warmth (from a potential prey) in Thermoreceptors their environment. 198 Motor Structures 1 Motor neurons transmit information from the CNS regarding a response. 2 Also called efferent neurons, they are associated with effector organs. 3 Their cell bodies are located in the motor cortex of brain or spinal cord. The triggered response in the 4 effector organ may help improve survival. 199 Effector Organs Muscle Tissues Glands Signals from the central nervous system trigger muscle tissues to undergo contraction, when needed. The motor neurons associated with muscle tissues serve to relay information regarding their contraction. Control of the contractions of the muscles can be voluntary or involuntary depending on the type of muscle tissue involved. 200  Effector Organs Muscle Tissues Glands Skeletal muscles are voluntary Smooth muscles help in the Cardiac muscles are involved in muscles that help bones move involuntary control of some the involuntary and continuous to initiate locomotion and other organs, such as intestines and pumping action of the heart for movements. blood vessels. blood circulation. 201  Effector Organs Muscle Tissues Glands Sample Responses of Tissues to Stimuli Stimulus Cold temperatures Stimulus Cold temperatures Response Arrector pili muscles make hairs erect Response Vasoconstriction via smooth muscles  Effector Organs Muscle Tissues Glands Sample Responses of Tissues to Stimuli Stimulus Nociceptive pain Stimulus Dim light Response Voluntary control of skeletal muscles Response Pupil dilation via skeletal muscles  Effector Organs Muscle Tissues Glands Motor Structures in Other Animals Structure Hydrostatic skeleton in earthworms Structure Pseudocoel in nematodes Function Allows muscular contractions Function Allows muscular contractions  Effector Organs Muscle Tissues Glands Motor Structures in Other Animals Structure Flatworm circular and longitudinal muscles Structure Insect striated flight muscles Function Allow movement in water or substrates Function Allow rapid wing vibrations  Effector Organs Muscle Tissues Glands Glands are effector organs that secrete specific substances in response to certain nervous control. Secretions from glands can either be enzymes or hormones depending on the type of gland that is stimulated. They can either be exocrine (secretions via ducts) or endocrine Pig liver (secretions into the bloodstream for circulation). 206  Effector Organs Muscle Tissues Glands Examples of Endocrine Effectors Pancreas (which is likewise Ovary (with a Graafian an exocrine gland) follicle) Stimulus Changes in blood glucose levels Stimulus Presence of FSH and LH Response Secretion of insulin or glucagon Response Follicle formation and ovulation  Effector Organs Muscle Tissues Glands Examples of Exocrine Effectors Sweat glands Mucous glands Stimulus High temperatures Stimulus Presence of irritants Response Secretion of sweat (mostly water) Response Increased secretion of mucus  A stimulus from the internal or external environment can elicit responses in an animal. The nervous system coordinates with other organ systems in order to elicit responses. 209  Sensory neurons send signals to the central nervous system regarding the stimuli that they detected. The CNS then responds by sending signals to motor neurons to generate the appropriate responses. 210  Different receptors detect various types of stimuli from the environment. These receptors are usually specific in terms of the type of stimuli that they detect. 211  Effector organs are structures that generate the changes and responses to stimuli. Muscles and glands are major effector organs in the animal body. Muscles usually respond through movement, while glands respond by secreting substances. 212 Animal stimuli and receptors 213