Midterm 1

Multiple choice: As always, choose the best answer for each multiple-choice question. Answer on your scantron form. Each question is worth 3 points.

1. In a negative feedback loop the effector

a. changes a regulated variable in a direction opposite to its deviation from the setpoint.

b. changes a regulated variable in the same direction as its deviation from the setpoint.

c. changes the setpoint to match the variable’s current value.

d. carries a message but does not itself alter the variable.

e. is the variable being regulated.

2. The “internal environment” of the body consists of

a. intracellular fluid

b. interstitial fluid

c. serum or plasma

d. Two of the above.

e. All of the above.

3. The use of sensory information to anticipate a change in a regulated variable before it happens is called a

a. negative feedback system.

b. positive feedback system.

c. feed forward system.

d. proportional response.

e. inhibitory response.

4. Consider two compartments, A and B, divided by a membrane permeable only to chloride ions. In compartment A we put 2.0 M NaCl, and in B we put 1.0 M NaCl. Which choice below best describes the pattern of ion diffusion?

a. Equal concentrations of Cl^- in both compartments at equilibrium; no change in Na⁺ concentrations from the initial state.

b. Some net movement of Cl^- from A into B; no change in Na⁺ concentrations from the initial state.

c. Some net movement of Cl^- from A into B; lesser net movement of Na⁺ from B into A.

d. Some net movement of Cl^- from A into B; lesser net movement of Na⁺ from A into B.

e. Equal numbers of Cl^- and Na⁺ ions diffuse across the membrane.

5. Consider two compartments, A and B, divided by a membrane. In A we put 500 mOsm NaCl, and in B we put 500 mOsm urea. Over time, water moves from compartment B into compartment A. Relative to compartment A, compartment B was initially

a. hyposmotic and hypotonic.

b. hyperosmotic and hypertonic.

c. isosmotic but hypotonic.

d. isosmotic but hypertonic.

e. Impossible to tell from the information given.

6. Which of the following involves channel proteins?

a. Secondary active transport

b. Primary active transport

c. Permeation

d. Simple diffusion

e. Facilitated diffusion

7. Which of the following synapses with skeletal muscles?

a. Cerebellum

b. Medulla

c. Afferent nervous system

d. Somatic nervous system

e. Autonomic nervous system

8. The concentration of potassium in the extracellular fluid around a cell is changed while all other ion concentrations remain the same. The best equation to predict the new resting potential of the membrane would be

a. Fick’s equation.

b. the Nerntz equation.

c. the Goldman equation.

d. the Cannon equation.

e. the Roberts equation.

9. The hyperpolarization at the end of a normal action potential results from

a. the opening of voltage-gated Na⁺ channels.

b. the closing of voltage-gated Na⁺ channels.

c. the opening of voltage-gated K⁺ channels.

d. the closing of voltage-gated K⁺ channels.

e. The membrane does not hyperpolarize at the end of a normal action potential.

10. Action potentials are propagated along an axon because

a. the action potential depolarizes adjacent regions of the neuron beyond the threshold voltage.

b. the threshold voltage of the membrane is lowered by the approaching action potential.

c. the wave form in the membrane opens mechanically-gated channels on its leading edge.

d. the cable properties of axons allow them to carry voltage signals long distances without degradation.

e. Action potentials are prevented from being propagated by the refractory period.

11. The fusing of synaptic vesicles with the membrane of the presynaptic cell is triggered most directly by

a. an influx of Na⁺.

b. an influx of Ca²⁺.

c. an efflux of K⁺.

d. direct effects of G-proteins.

e. secondary messengers activated by G-proteins.

12. Which of the following would not be true of slow chemical synaptic transmission?

a. Released neurotransmitters take as long as 2 ms to affect the post-synaptic neuron.

b. Neuropeptides may serve as the neurotransmitter.

c. G-proteins are often activated by the neurotransmitter receptor.

d. Slow neurotransmitters are typically released from the presynaptic neuron at different locations than are fast neurotransmitters.

e. Slow chemical transmissions may act to inhibit the post-synaptic neuron.

13. A neurotransmitter associated with the inhibition of pain signals is

a. Epinephrine

b. Norepinephrine

c. Dopamine

d. Endorphin

e. GABA

14. Sensory neurons can send information about stimulus strength to the central nervous system via

a. the duration of the depolarization period of each action potential.

b. the frequency of action potentials generated.

c. the amplitude of each action potential.

d. Two of the above.

e. All of the above.

15. An interoceptive receptor

a. is located in the taste buds.

b. is sensitive to pain.

c. senses the body’s internal environment.

d. rapidly adapts to a constant stimulus.

e. acts as a connector between a sensory neuron and the central nervous system.

16. Which of the following is not true concerning the olfactory system of mammals?

a. Olfactory receptors are restricted to the nasal cavity.

b. The “cilia” of olfactory neurons are not true cilia.

c. The olfactory cilia are covered in a layer of mucus.

d. Stimulation of olfactory neurons involves the G-protein system.

e. Each olfactory neuron is sensitive to only one chemical.

17. An example of a tonic receptor is

a. Ruffini’s capsule.

b. a Pacinian corpuscle.

c. a hair receptor.

d. Two of these are tonic receptors.

e. All of these are tonic receptors.

18. A person who lacked otoliths would probably have trouble

a. seeing.

b. hearing.

c. sensing her body’s movement.

d. sensing her body’s orientation.

e. understanding this question.

19. The sensory neurons of the auditory system respond

a. directly to pressure changes in the air.

b. directly to pressure changes in the cochlear fluid.

c. to mechanical disturbances of the organ of Corti.

d. to chemical stimulation of the organ of Corti.

e. to fluid movements in the semicircular canals.

20. Which of the following statements concerning vertebrate rod cells is true?

a. Rod cells are less sensitive to light than cone cells.

b. Rod cells are oriented so that their photoreceptive segment is the closest segment to the light source.

c. The retinal component of rhodopsin changes from a trans to a cis form when struck by a photon.

d. The G-protein system involving transducin, phosphodiesterase and GMP amplifies the response to light in rod cells.

e. Rod cells are depolarized when struck by light.

21. Which type of secretion is not a chemical messenger?

a. Autocrine

b. Paracrine

c. Exocrine

d. Hormone

e. All of these secretions are chemical messengers.

22. Hormones that stimulate intracellular receptors include

a. Peptide hormones

b. Steroid hormones

c. Catecholamines

d. Prostaglandins

e. Alcohols

23. The release of hormones is controlled by

a. endocrine cells themselves, which respond directly to physiological variables.

b. the nervous system.

c. the levels of other hormones.

d. Two of these mechanisms control the release of hormones.

e. All three of these mechanisms control the release of hormones.

24. Growth hormone release is greatest.

a. Shortly after going to sleep.

b. Shortly before waking up.

c. Shortly after waking up.

d. Shortly before going to sleep.

e. The peak period of growth hormone release is unpredictable.

25. Which of the following glands can most directly control body temperature?

a. Gonads

b. Thyroid gland

c. Adrenal cortex

d. Adrenal medulla

e. Posterior pituitary

Short answer: Write a concise answer to each of the following questions. Your answers should fit in the spaces provided.

26. Identify and briefly explain an example of a positive feedback loop. (3 points)

27. Provide the Fick equation (in some form), and indicate what each variable stands for. (You do not need to provide any units.) (4 points)

28. Name two ways that the speed of propagation of action potentials along an axon can be increased. (2 points)

29. Briefly describe what is meant by neuronal integration, and explain the difference between temporal summation and spatial summation of post-synaptic potentials. (4 points)

30. The sensory system can often provide information on the intensity of a particular kind of stimulus over ranges of several magnitudes. In other words, both a very weak and a very strong stimulus are accurately reported to the central nervous system. Briefly describe two mechanisms or strategies that allow the sensory system to do this. (You may include graphs in your response if you desire.) (4 points)

31. Label the parts of the eye on the diagram. (3 points)

32. Fill in the following table for the hypothalamic-pituitary system with the appropriate hormones. (Note that this is not a complete table.) At the bottom of the table, list the two inhibitory hormones released by the hypothalamus and indicate which pituitary hormones they inhibit. Be sure to use the full names of each hormone, not the abbreviations. (5 pts.)

Hypothalamus		Anterior Pituitary		Target Organ or Tissue
_______________		_______________		Adrenal cortex
_______________		_______________		Gonads
		_______________
Inhibitory hormones:		Hormone(s) inhibited:
_______________		_______________
_______________		_______________