JoShur Darker Laboratory Review 17 Per Pherel. Is the sciatic nerve part of the
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JoShur Darker Laboratory Review 17 Per Pherel. Is the sciatic nerve part of the central nervous sysem or the peripheral nervous system? erebrn 2. What part of the brain is divided into right and left hemispheres.? 3. What portion of the brain looks like a tree in cross section? 4 What is the most posterior portion of the brain stem? 5. What cerebral lobe is associated with the sense of vision? 6. What structures protect the spinal cord? 7. What makes the white matter of the spinal cord appear white? 8. What type of neuroe is found completely within the central nervous system? 9. What type of neuroe is responsible for transmitting merve impulses from the spinal cord to an effector? 10. What part of the eye refracts and Socuses light rays? 11. What part of the ear contains the sensory receptors for hearing? 12. What is the anatomical name for the eardrum that picks up sound waves? 13. What layer of the skin contains Meissner and Pacinian corpuscles? 14. What are the names of the chemoreceptors that respond to molecules in air and water? Thought Questions 15. Explain why people who develop cataracts (cloudy eye lenses) require surgery to implant new lenses. 16. When you stared at the dark cross with your left eye, why did the dark circle "disappear from view as you moved the illustration toward you? In a drag race, drivers must wait until the green light is illuminated before they can move their vehicle. Explain why a time delay exists, based on the information presented in this exercise. 17. 238 Laboratory 17 Nervous System and Senses 17-16Explanation / Answer
1. Is the sciatic nerve part of the central nervous system or the peripheral system?
Answer: Peripheral nervous system
Explanation: Sciatic nerve is a branch of sacral plexus which is a part of peripheral nervous system
2. What part of the brain is divided into right and left hemispheres?
Answer: Cerebrum
Explanation: Forebrain consists of cerebrum, thalamus and hypothalamus in which cerebrum is divided into right and left hemispheres
3. What portion of brain looks like a tree in cross section?
Answer: Arbor vitae
Explanation: Arbor vittae in Latin means tree of life, it is so named because it is the cerebellar white matter which is branched and appears like tree when seen in cross section
4. What is the most posterior portion of the brain stem?
Answer: Medulla
Explanation: The most superior part of brainstem is midbrain in which more anterior superior part is pons while most posterior inferior part is medulla
5. What cerebral lobe is associated with the sense of vision?
Answer: The occipital lobe
Explanation: Occipital lobe is the visual processing center for most of the mammals. The other lobes of cerebral cortex are frontal, pareital, and temporal lobes
6. What structures protect the spinal cord?
Answer: Vertebrae of vertebral column and Meninges (Dura matter, arachnoid matter and pia matter)
Explanation: The space between vertebra and dura matter called as epidural space is filled with Cerebrospinal fluid which also serves as shock absorber
7. What makes the white matter of the spinal cord appear white?
Answer: White matter consists of neurons that are covered by myelin sheath (myelinated neurons) that is made of fat and proteins thus appearing white in color
8. What types of neuron is found completely within the central nervous system?
Answer: Interneuron
Explanation: Interneuron is completely found within CNS and typically connect sensory and motor neurons in reflex arcs
9. What type of neuron is responsible for transmitting nerve impulses from the spinal cord to an effector?
Answer: Motor neurons
Explanation: Motor neurons are efferent nerves which carry information from the CNS to the effector organ. The information from affector to CNS is carried by Sensory or Afferent neurons while the neurons which does both the functions are called mixed neurons
10. What part of the eye refracts and focuses light rays?
Answer: Cornea
Explanation: Cornea is outer anterior fibrous layer of eye and continues posteriorly as sclera. Cornea refract rays of light to focus them onto the retina. Sclera is a fibrous coat which protects the inner parts of the eye
11. What part of the ear contains the sensory receptors for hearing?
Answer: Cochlea
Explanation: Cochlea and vestibular part comprises the inner part of the ear in which cochlea is snail like apparatus with fluid and consists of organ of corti with cilia which is responsible for hearing while vestibular part is responsible for balance, posture and equilibrium of the body's position
12. What is the anatomical name for the eardrum that picks up sound waves?
Answer: Tympanic membrane
Explanation: Ear pinna transmits or converges the airborne vibrations to the tympanic membrane or eardrum
13. What layer of the skin contains Meissner and Pacinian corpuscles?
Answer: Dermis
Explanation: The structure of skin consists of 3 layers external epidermis, middle layer of dermis and inner layer of hypodermis.
Dermis is highly vascular and contains Meissner, pacinian corpuscles which serve as sensory receptors. It is made up of fibroelastic connective tissue
Hypodermis is made up of loose connective tissue with variable amounts of adipose tissue
14. What are the names of the chemoreceptors that respond to molecules in air and water?
Answer: Peripheral chemoreceptors like carotid and aortic bodies
Explanation: Chemoreceptors are divided into peripheral and central chemoreceptors. Peripheral chemoreceptors are polymodal receptors which can detect slight variations in blood oxygen, carbon dioxide, glucose, pH etc
15. Explain why people who develop cataracts require surgery to implant new lenses
Answer: Cataract refers to the clouding or partial/ complete loss of transparency of lens in the eyes which ultimately results in blurred vision (reduction in visual acuity), unable to see in dim light, halos around lights or complete loss of vision.
Since, this is an irreversible process, the natural cloudy lens of eye are replaced by artificial intraocular lenses through surgery.
Surgery is the only treatment for cataract in which either pseudophakic or phakic intraocular lens are implanted by removing the cataract
16. When you stared at the dark cross with your left eye, why did the dark circle disappear from view as moved the illustration toward you?
Answer: The perception of vision is due to light sensitive cells present in the eyes. But there is a blind spot in the eye through which the nerves, arteries and veins make their way in and out of the eye. This part of retina do not contain light sensitive cells.Staring at the cross makes the dark circle to be focussed on blind spot (optic disk) which makes it disappear as there are no cells to perceive the dark circle. When it is refocussed in other part of retina except blind spot it can be seen normally
So, the disappearance of dark circle is due to the dark spot or optic disk in the eye
17. In a drag race, drivers must wait until the green light is illuminated before they can move their vehicle. Explain why a time delay exists, based on the information presented in this exercise.
Answer: The delay is due to the Neuromuscular reaction time. There is variation in individual reaction times and activation of muscles which makes a delay in interpretation of visual perception of green light by the driver and start off.
Hence green light illumination in drag races will not follow the pattern to avoid false starts and to make a uniform start for all vehicles in the race, giving them an equal chance
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