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By Root 834 0

the recessive gene. Numerous recessive genes are responsible for syndromes in the homozygous condition. Tay-Sachs syndrome produces progressive loss of nervous function and death in a baby. Albinism arises from a failure to synthesize or store pigment and also involves abnormal nerve pathways to the brain, resulting in quivering eyes and the inability to perceive depth or three-dimensionality with both eyes. Phenylketonuria (PKU) results in severe, irreversible brain damage unless the baby is fed a special diet low in phenylalanine within 30 days of birth; the infant lacks an enzyme to process this amino acid which can build up and poison cells of the nervous system. Thus, heredity and environment interact to determine a trait. Huntington’s disease is an example of a dominant gene defect that involves degeneration of the nervous system. Progressive symptoms involve forgetfulness, tremors, jerky motions, loss of the ability to talk, personality changes such as temper tantrums or inappropriate accusations, blindness, and death. Recessive genes for color blindness are located on the X chromosome with no corresponding gene on the Y chromosome. As a result, males show sex-linked traits like color blindness much more frequently than females. Behaviors and diseases may have variations only some of which are genetically based. A form of familial Alzheimer’s disease has been attributed to a gene on chromosome 21, but not all cases of Alzheimer’s disease are associated with that gene.

Review Questions

1. A neuron without terminal buttons would be unable to

(A) receive information from neighboring neurons

(B) generate an action potential

(C) direct the synthesis of neurotransmitters

(D) secrete neurotransmitters to postsynaptic neurons

(E) transport ions across the cell membrane

2. Paul Broca found that the loss of the ability to speak intelligibly is associated with damage to a region of the brain in the

(A) thalamus

(B) right parietal lobe

(C) right occipital lobe

(D) left temporal lobe

(E) left frontal lobe

3. Scientists are able to see changes in the brain as it processes information by means of

(A) lesioning

(B) autopsy

(C) CT

(D) MRI

(E) PET

4. The simplest behaviors we carry on

(A) are learned when we are infants

(B) do not involve the central nervous system

(C) are called instincts

(D) include sneezing and blinking

(E) must be processed by the medulla

5. Of the following, the effect of adrenalin on the body is most similar to the effect of the

(A) cerebellum

(B) parathyroids

(C) somatic nervous system

(D) parasympathetic nervous system

(E) sympathetic nervous system

6. Mr. Jenkins’ suffered a “stroke” as a result of a brain injury. Although he can still move the fingers on his right hand, he has lost sensation in these parts. Of the following, the site of damage to his brain is most likely in the

(A) right frontal lobe

(B) right temporal lobe

(C) left frontal lobe

(D) left parietal lobe

(E) hypothalamus

7. Of the following, which are located exclusively in the central nervous system?

(A) afferent neurons

(B) interneurons

(C) efferent neurons

(D) glial cells

(E) effectors

8. Which of the following glands interact(s) most directly with all of the others to help regulate body processes?

(A) pituitary

(B) adrenals

(C) parathyroids

(D) thyroid

(E) ovaries

9. Gunshot wounds, tumors, and strokes all result in

(A) infections

(B) significant loss of function

(C) lesions

(D) pain

(E) necessity for surgery

10. Which of the following must be males?

(A) dizygotic twins

(B) monozygotic twins

(C) Down syndrome children

(D) Klinefelter’s syndrome children

(E) Turner’s syndrome children

11. Which includes all of the others?

(A) autonomic nervous system

(B) peripheral nervous system

(C) somatic nervous system

(D) parasympathetic nervous system

(E) sympathetic nervous system

12. Which stimulate a muscle to contract?

(A) adrenal hormones

(B) receptors

(C) sensory