Biology Homework Chapter 29: The Senses - Hearing

Homework

• Reading Preparation
• WebLecture
• Study Activity
• Preparation work for chat
• Online Quiz
• Lab Instructions

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Reading Preparation

Textbook assignment: Chapter 29: The Senses, 1-6.

Study Points

Try to link the information in this chapter to what you already know about general cell functions, neuron cells in particular, the nervous system and transport across membranes.

• 29.1: Sensory cells respond to stimuli of different sorts: chemical changes, electrical charges, thermal changes, vibrations, and light can all cause nervous system receptor cells to suffer changes in action potential. Each type of sensor cell receives input (pressure changes, chemical interactions with surface molecules, light stimulus of pigment molecules). In taste buds, for example, the stimulating molecule (salt, sugar, acid) binds to the matching surface receptor membranes, which triggers a transduction pathway similar to those followed by hormones. The receptor cell releases neurotransmitters to its nearest neuron non-receptor neighbors, which pass the signal to the central nervous system and brain for analysis. If multiple receptor cells fire, the brain receives a more intense signal. Repeated firing can cause the brain to ignore signals of a "harmless" situation (sensory adaptation), so that it can focus on signals that require a response.
• 29.2: We have competing theories for possible magnetic field sensory cells in animals: (1) the Earth's magnetic field can affect biochemical reactions in cells, and (2) cells contain magnetite, metal molecules that can be strongly magnetized.
• 29.3: Specialized sensory receptors detect different kinds of stimuli:
  • Pain receptors respond to excessive situations, warning the brain that tissue damage is underway.
  • Thermoreceptors track changes in temperature and stimulate homeostasis responses to maintain the body's intermal temperature (goose bumps, shivering, sweating, panting).
  • Mechanoreceptors responds to changes in pressure felt by the skin, ears, or even internal tissues. These tell you where your body parts are; they let you coordinate sight information with body motion to walk on uneven ground or pick something up.
  • Chemoreceptors respond to the presence of chemicals, either through taste or smell, and trigger recognition analysis in the brain.
  • Electromagnetic receptors detect changes in electrical, magnetic, or light levels and colors.

  Note that different sources may classify receptors in different groups, breaking out "photoreceptors" from other kinds of electromagnetic receptors, or subsuming pain receptors under mechanoreceptors and thermoreceptors. The important thing to remember is that receptors are specialized; however we group them for study and comparison, they all have the same general structure and response processes.

• 29.4: The human ear collects sound in the outer ear and funnels it through the auditory canal to the eardrum, where it is transferred from air to the three small bones of the middle ear, which in turn relay it to the cochlea of the inner ear. There vibrating fluids cause the hair cells of the basilar membrane to move, which shifts the action potentials of the attached auditory neurons and causes signals to be sent to the brain. Variations in volume ater the strength of the signal; variations in pitch cause frequency changes in the vibrations of the responding hair cells. The sensitivity of the signal response lets us analyze complex sounds made of multiple vibration patterns, such as voices. However, repeated intense sound can damage the mechanical components of the ear, reducing sensitivity.
• 29.5: Levels of fluids in the semicircular canals next to the cochlea detect changes in the head's rate of movement and angle, providing information necessary to preserve the sense of balance.
• 29.6: Conflicting signals between the eyes and balance sensitivity of the ear can lead to motion sickness. Medication can suppress not the initial signals, but the brain's response, so that the victim feels less nauseated.

Web Lecture

Read the following weblecture before chat: The Senses, Part I.

Take notes on any questions you have, and be prepared to discuss the lecture in chat.

Study Activity

Perform the study activity below:

Chat Preparation Activities

• Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

Chapter Quiz

• No quiz yet: the Chapter Quiz opens when we finish the chapter.

Lab Work

Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.

• Lab Instructions: Peripheral Vision

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