Human Senses and Eye Anatomy
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Questions and Answers

Which type of cone is sensitive to the shortest wavelengths of light?

  • Blue cone (correct)
  • Red cone
  • Yellow cone
  • Green cone
  • What is the primary function of rods in the retina?

  • Vision in dim light (correct)
  • Color vision in bright light
  • Detailed visual acuity
  • Peripheral vision in bright light
  • Which of the following best describes the area of the retina known as the fovea centralis?

  • Contains both rods and cones
  • Has the highest density of rod cells
  • Contains only rods
  • Contains only cones (correct)
  • Color blindness is primarily caused by a deficiency in which of the following?

    <p>Red receptors</p> Signup and view all the answers

    What occurs at the optic disk in the retina?

    <p>Absence of photoreceptor cells</p> Signup and view all the answers

    Which type of light absorption is associated with photopsin III?

    <p>Bluish-violet light</p> Signup and view all the answers

    How does the brain interpret colors according to the input from cone cells?

    <p>Through comparisons between red and green cones' signals</p> Signup and view all the answers

    Which type of vision do cones provide?

    <p>Detailed color vision</p> Signup and view all the answers

    What type of receptor is responsible for detecting temperature in the general senses?

    <p>Thermoreceptors</p> Signup and view all the answers

    Which structure is primarily responsible for draining lacrimal fluid from the eye?

    <p>Lacrimal canals</p> Signup and view all the answers

    What is the function of the iris in the eye?

    <p>To adjust the size of the pupil</p> Signup and view all the answers

    Which muscle contracts to allow the eye to look outward?

    <p>Lateral rectus</p> Signup and view all the answers

    What is the primary role of the conjunctiva?

    <p>To protect the surface of the eye</p> Signup and view all the answers

    Which layer of the eye contains photoreceptors?

    <p>Sensory tunic</p> Signup and view all the answers

    What role does lacrimal fluid play in eye health?

    <p>Fights antigens and lubricates the eye</p> Signup and view all the answers

    Which extrinsic eye muscle allows for downward eye movement?

    <p>Inferior rectus</p> Signup and view all the answers

    What component of rhodopsin is responsible for its visual function?

    <p>Retinal</p> Signup and view all the answers

    Which structure prevents light from scattering in the eye?

    <p>Choroid layer</p> Signup and view all the answers

    What triggers the production of erythropoietin to control erythrocyte production?

    <p>Reduced oxygen levels in the blood</p> Signup and view all the answers

    Which type of leukocyte plays a crucial role in immune responses?

    <p>Lymphocytes</p> Signup and view all the answers

    Which of the following cell types is categorized as a granulocyte?

    <p>Eosinophil</p> Signup and view all the answers

    What is the first phase of hemostasis that occurs following a blood vessel injury?

    <p>Vascular spasms</p> Signup and view all the answers

    Where does hematopoiesis primarily occur in adults?

    <p>Red bone marrow</p> Signup and view all the answers

    Which two types of leukocytes lack visible granules in their cytoplasm?

    <p>Lymphocytes and Monocytes</p> Signup and view all the answers

    What should occur during the platelet plug formation phase of hemostasis?

    <p>Platelets aggregating and adhering to the exposed collagen</p> Signup and view all the answers

    What is the lifespan of a typical erythrocyte before it is removed from circulation?

    <p>100 to 120 days</p> Signup and view all the answers

    Which of the following granulocytes is responsible for initiating inflammation?

    <p>Basophils</p> Signup and view all the answers

    What identifies the process by which blood cell formation occurs?

    <p>Hematopoiesis</p> Signup and view all the answers

    What protein is primarily involved in the clotting process during hemostasis?

    <p>Fibrinogen</p> Signup and view all the answers

    Which leukocyte can move via ameboid motion to reach areas of infection?

    <p>Neutrophil</p> Signup and view all the answers

    During coagulation, what does thrombin convert to form a clot?

    <p>Fibrinogen</p> Signup and view all the answers

    What happens to the blood vessel muscle contractions during vascular spasms?

    <p>They contract, narrowing the vessel</p> Signup and view all the answers

    Study Notes

    The Senses

    • The human body has five basic senses: touch, taste, smell, sight, and hearing
    • Touch is further divided into tactile, temperature, pressure, and pain
    • Sensory receptors for each of these senses are specialized

    The Eye and Vision

    • The eye is responsible for sight
    • The human eye contains over a million nerve fibers
    • The eye is protected by the bony orbit
    • A cushion of fat surrounding the eye provides additional protection

    Accessory Structures of the Eye

    • The eyelids, eyelashes, ciliary glands, conjunctiva, and lacrimal apparatus protect and lubricate the eye
    • The eyelids brush particles out of the eye and cover the eye
    • Eyelashes trap airborne particles
    • Ciliary glands are modified sweat glands that lie between eyelashes
    • The conjunctiva lines the eyelids and connects to the surface of the eye, secreting mucus to lubricate the eye

    Conjunctivitis

    • Inflammation of the conjunctiva
    • Caused by bacterial or viral infections
    • Highly contagious

    Lacrimal Apparatus

    • The lacrimal apparatus is responsible for producing and draining tears
    • The lacrimal gland produces tears
    • Lacrimal canals drain tears from the eyes
    • The lacrimal sac provides passage for tears to the nasal cavity
    • The nasolacrimal duct empties tears into the nasal cavity

    Function of the Lacrimal Apparatus

    • Tears are a dilute salt solution
    • Tears contain antibodies and lysozyme which help protect the eye from foreign substances like bacteria
    • Tears protect, moisten, and lubricate the eye

    Extrinsic Eye Muscles

    • Extrinsic eye muscles attach to the outer surface of the eye
    • These muscles are responsible for eye movements

    Structure of the Eye

    • The eye is composed of three layers: the fibrous tunic, the choroid, and the sensory tunic
    • The fibrous tunic is the outermost layer
    • The choroid is the middle layer
    • The sensory tunic is the innermost layer

    The Fibrous Tunic

    • The sclera is the tough, white connective tissue layer of the fibrous tunic
    • The sclera can be seen as the “white of the eye”
    • The cornea is the transparent, central, anterior portion of the fibrous tunic
    • The cornea allows light to pass through the eye and bends light

    Choroid Layer

    • The choroid is a blood-rich layer that nourishes the eye
    • The choroid contains pigment to prevent light scattering
    • The choroid is modified internally to form the ciliary body and the iris

    Sensory Tunic (Retina)

    • The sensory tunic contains the light-sensitive receptor cells
    • The sensory tunic also contains ganglion cells and bipolar cells
    • Signals travel from the retina to the brain through the optic nerve

    Visual Pigments

    • Rhodopsin, a visual pigment found in rods, is composed of opsin and retinal proteins
    • Light hitting rhodopsin causes it to bleach

    Rhodopsin & Opsin

    • Rhodopsin is a pigment in rod cells that absorbs light
    • Rhodopsin is composed of opsin and retinal
    • Retinal is a vitamin-A derivative
    • Retinal changes shape when it absorbs light
    • Rhodopsin straightens out and breaks down into opsin and retinal
    • There are three other opsins besides rhodopsin:
      • Photopsin I: absorbs yellowish-green light
      • Photopsin II: absorbs green light
      • Photopsin III: absorbs bluish-violet light

    Neurons of The Retina Overview

    • The retina is a light-sensitive layer at the back of the eye
    • The retina contains specialized neurons, called photoreceptor cells, that detect light
    • There are two main types of photoreceptor cells: rods and cones

    Rod Cells

    • Rods are most abundant towards the edges of the retina
    • Rods allow for dim light vision and peripheral vision
    • Rods are more sensitive to light; they do not respond in bright light
    • Rods are involved in black and white (grayscale) vision

    Cone Cells

    • Cones allow for detailed color vision
    • Cones are densest in the center of the retina
    • The fovea centralis is an area of the retina with only cones
    • Cones respond best in bright light

    Optic Disk

    • The optic disk is the point where the optic nerve leaves the eye
    • There are no photoreceptor cells at the optic disk, resulting in a blind spot

    Cone Sensitivity

    • There are three types of cones:
      • Red cones: sensitive to long wavelengths
      • Green cones: sensitive to medium wavelengths
      • Blue cones: sensitive to short wavelengths
    • Each cone type is most sensitive to a different wavelength of light
    • Color blindness occurs from a lack of one or more cone type
    • Most common forms of colorblindness are red-green, due to a lack of red receptors

    How We See Colors

    • The brain compares the input from different cone cells to determine color
    • Red and green cone signals are compared by opponent cells in the retina
    • Opponent cells compute the balance of red and green light from a specific visual field location
    • Other opponent cells compare blue cone signals with combined red and green cone signals

    Color Blindness

    • Color blindness is an inherited trait
    • The lack of one or more cone types causes color blindness
    • Colorblindness is sex-linked, meaning it is more common in males
    • Color blindness is caused by a gene on the X chromosome, of which males have only one

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