SBI4U - Nervous Systems, Menstruation, Reproduction

SBI4U - Nervous Systems, Menstruation, Reproduction

By definintion, a “nerve” is

a. a bundle of neurons and their axons

b. a single extension oof a neeuron

c. the same as a neuron within the central nervous system

d. a dendrite

e. a fiber more than 10 inches in length

a. a bundle of neurons and their axons

Which of the following sequences is correct?

a. receptors→sensory neurons→motor neurons→ interneurons

b. sensory neurons→ receptors→ motor neurons

c. motor neurons → integrations → sensory neurons

d. receptors → motor neurons → interneurons → sensory neurons

e. sensory neurons → interneurons → motor neurons

e. sensory neurons → interneurons → motor neurons

The structure labeled 2 is

a. the axon hillock

b. a dendrite

c. a schwann cell

d. an oligodendricyte

e. a node of raniver

a. the axon hillock

The structure labeled 1 is

a. the axon hillock

b. a dendrite

c. a schwann cell

d. an oligodendricyte

e. a node of raniver

b. a dendrite

The structure labelled 5 is

a. the axon hillock

b. a dendrite

c. a schwann cell

d. an oligodendricyte

e. a node of raniver

c. a schwann cell

Functionally speaking, a nerve impulse is

a. a flow of electrons along the outside of the plasma membrane of a neuron

b. the movement of cytoplasmic elements through the core of the neuron

c. a series of changes in membrane potentials

d. a lengthening and shortening of the membrane extensions of a neuron

c. a series of changes in membrane potentials

Within a single neuron, the direction an impulse follows is

a. dendrite→axon→cell body

b. axon→ dendrite →cell body

c. dendrite → cell body → axon

d. cell body→ dendrite → axon

e. cell body → axon → dendrite

c. dendrite → cell body → axon

In the neuron, the sodium potassium pump

a. requires ATP and provides an equal distribution of ions across the axon membrane

b. requires ATP and provides an unequal distribution of ions across the axon membrane

c. doesn’t require ATP and provides an equal distribution of ions across the axon membrane

d. doesn’t require ATP and provides unequal distribution of ions across the axon membrane

b. requires ATP and provides an unequal distribution of ions across the axon membrane

During which part of action potential is the sodium potassium pump active

a. Y only

b. Z only

c. W and X

d. W, X, Y, and Z

d. W, X, Y, and Z

What does the term “threshold” refer to during the synaptic transmission

a. the number of impulses in a given unit of time

b. the amount of stimulus required to cause depolarization

c. the maximum numbeer of sodium ions that can exit the axon

d. the maximum time neurotransmitters spend in the synaptic cleft

b. the amount of stimulus required to cause depolarization

The phrase “all or nothing”. used in conjunction with discussion about an action potential, means that

a. a resting membrane potential has been received by the cell

b. nothing can stop the action potential if the threshold is reached

c. the membrane either achieves total equilibrium or remains as far from equilibrium as possible

d. propagation along the neuron is saltatory

e. none of these

b. nothing can stop the action potential if the threshold is reached

Before another action potential “spike” can occur

a. after hyperpolarization, there is a restoration of resting conditions in the membrane

b. the membrane voltage must drop to zero

c. the Na+/K+ pump must case temporarily

d. all of the membrane gates must b closed at the same time

a. after hyperpolarization, there is a restoration of resting conditions in the membrane

A deterioration in the myelin sheaths of motor axons to the lower leg would be expected to

a. remove the restraints to ion movement and speed up impulse transmission

b. cause immobility of the leg due to cessation of impulses to leg muscles

c. slow the rate of transmission and cause lack of motor control

d. have little effect becausee the sheaths are for insulation only

c. slow the rate of transmission and cause lack of motor control

Neurotransmitter substances

a. are usually small molecules

b. change the permeability of postsynaptic cells

c. may be inhibitory or stimulatory

d. cause graded potentials near the synapse

e. all of the above

e. all of the above

Neurotransmitters catagorized as inhibitory would be expected too

a. act independently of their receptor proteins

b. close potassium channels

c. open sodium channels

d. close chloride channels

e. hyperpolarize the membrane

e. hyperpolarize the membrane

Which of the following statements is FALSE

a. synaptic potentials may vary in magnitude

b. transmitter molecules bind to receptor molecules on the postsynaptic cells

c. an excitatory postsynaptic potential is hyprpolarizing. whereas an inhibitory postsynaptic potential is depolarizing

d. synaptic integration means that signals arriving at a neuron can be reinforced or dampened by the arrival of other signals

e. synaptic integration means that signalss arriving at a neuron can cause t to “fire” or prevent in from “firing”

c. an excitatory postsynaptic potential is hyprpolarizing. whereas an inhibitory postsynaptic potential is depolarizing

What is the function of hydrolytic enzymes such as AChE in the synaptic cleft?
a. to increase the threshold level

b. to break down neurotransmitters

c. to stimulate contracile proteins in the synaptic ending

d. to increase the permeability of the presynaptic membrane to calcium ions

b. to break down neurotransmitters

Areas of the spinal cord appear glistening white because of

a. naked dendrites

b. cell bodies

c. neuroglia cells

d. lack of meniges

e. myelin sheaths

e. myelin sheaths

What is the advantagee of reflex arcs

a. they stop the sensation of pain in the brain

b. thy provide a quick response to a stimulus

c. they take place independently of any nerve function

d. they allow us to think about an appropriate response to a stimulus

b. they provide a quick response to a stimulus

The vertebrate nervous system can be divided into more and more subsystems. The two major divisions of the vertebrate nervous system are the

a. autonomic and peripheral systems

b. brain and spinal cord

c. cranial and spinal nerves

d. central and peripheral nervous systems

e. sympathetic and parasympathetic systems

d. central and peripheral nervous systems

The word that best describes the interaction of sympathetic and parasympathetic systems is

a. antagonistic

b. cooperation

c. overriding

d. subversive

e. ineeffectivee

a. antagonistic

Four of the five answers listed below are actions mediated by the parasympathetic nervous system. Select the exception

a. pulse increasees

b. blood glucose levels drop

c. metabolism increases

d. digestion slows down

e. pupils of the eyes dilate

d. digestion slows down

The tissue indicated by i.) is

a. gray matter

b. white matter

c. yellow body

d. ventricles

e. meninges

a. gray matter

The part of the brain that controls the basic (unconscious) responses necessary to maintain lif processes (such as breathing or heartbeat) and directly connects to the spinal cord is the

a. medulla oblongata

b. corpus callosum

c. fissure of Rolando

d. cerebellum

e. cerebral cortex

a. medulla oblongata

What part of the brain is responsible for memory and conscious thought (thinking)

a. the thalamus

b. the cerebrum and hippocampus

c. the cerebellum

d. the medulla oblongata

b. the cerebrum and hippocampus

The part of the brain labelled A is the

a. cerebrum

b. pons

c. cerebellum

d. medulla oblongata

e. thalamus

a. cerebrum

The part of the brain labeled E is the

a. cerebrum

b. pons

c. cerebellum

d. medulla oblongata

e. thalamus

c. cerebellum

The largest part of the brain can be subdivided into lobes. The part of the brain labelled A is th

a. temporal lobe

b. frontal lobe

c. partial lobe

d. occipital lob

e. cerebellum

a. temporal lobe

The part of the brain labelled D is the

a. temporal lobe

b. frontal lobe

c. partial lobe

d. occipital lobe

e. cerebellum

d. occipital lobe

The following diagram shows the location of two special areas of the brain, Broca’s area and Wernickle’s area. What function is associated with the two areas?

a. speech

b. memory

c. taste

d. visions

e. hearing

a. speech

Which of the following hormones is/are produced in males and females

a. follicle stimulating hormonoe

b.luteinizing hormone

c. progesterone

d. follicle stimulating hormone and progesterone

e. follicle stimulating hormones, and luteinizing hormone

e. follicle stimulating hormones, and luteinizing hormone

What effect does decreasing levels of estroogene and progesterone have on the female reproductive system

a. ovulation would occur

b. the corpus lutetium degenerates and ovulation occurs

c. the endometrium breaks down and menstruation begins

d. the uterine lining becomes secretory and pregnancy begins

c. the endometrium breaks down and menstruation begins

Where are the hormones produced which cause the endometrium to thicken during the uterine (luteal) cycle

a. in the uterus

b. in the hypothalamus

c. in the corpus luteum

d. in the posterior pituitary

c. in the corpus luteum

Menstration begins in response to

a. rising levels of FSH and lH

b. falling levels of estrogen

c. falling levels of progesterone

d. falling levels of estrogen and progesterone

d. falling levels of estrogen and progesterone

What are the days 5-13 of the uterine cycle called

a. the luteal phase

b. the follicular phase

c. ovulation

d. the menstrual phase

b. the follicular phase

Which of the following is a consequence of increased secretions of progesterone?

a. the release of th ova

b. the maturation of the follicle

c. a decrease in luteinizing hormone

d. an increase in follicle stimulating hormonee

c. a decrease in luteinizing hormone

Ovulation is triggered by

a. high levels of LH

b. low levels of Lh

c. high levels of chorionic gonadotropin

d. high levels of estrogen

e. high levels of progesterone

a. high levels of LH

Where are the hormones produced which cause the endometrium to thicken more during the uterine (Luteal) cycle

a. in the uterus

b. in the hypothalamus

c. in the corpus lutetium

d. in the posterior pituitary

c. in the corpus lutetium

After ovulation, the follicle develops into the

a. ovum

b. placenta

c. endometrium

d. corpus lutetium

d. corpus lutetium

Implantation of the fertilized egg in the uterus results in the secretion of a new hormone. Since only a growing embryo produces it, this hormone is also a good candidate for an indicator iiin a pregnancy test. Which hormone is it?

a. progesterone

b. luteinizing hormone

c. follicle stimulating hormone

d. human chorionic gonadotropin

e. testosterone

d. human chorionic gonadotropin

A contraceptive pill “fools” your boddy into believing you’re pregnant. It contains

a. estrogen

b. progesterone

c. the follicle stimulating hormone

d. luteinizing hormone

e. both estrogen and prgoesterone

e. both estrogen and prgoesterone

1. Nerve signals are electrical in nature

a) Explain how the resting potential of a nerve cell is achieved (3 marks)

The resting potential of a nerve cell is achieved through the following mechanisms:

1. Large negativ charged moleculess (like proteins) are trapped inside the cll

2. The Na+.K- pump moves 3Na+ out for every 2K+ in, causing a difference in ion concentration in and out of the cell.

3. Leaky channels (always open); a neuron at resting potential contains many opn K+ channels, but fewer for Na+, meaning K+ diffuses out of the cell faster than Na+ moves in

1. Nerve signals are electrical in nature

b) Describe the events that occur along an axon when a nerve ‘fires’ using a labelled diagram of an action potential (5+ marks)

1. Resting state: The voltage-gated Na+ and K+ channels are closed, resting potential is maintained by ungated channels and trapped proteins

2. A stimulus opens some Na+ channels first and if a threshold is reached, an action potential that cant be stopped is propagated along the axon.

3. When threshold potential is reached, additional Na+ voltage gated channls open, and Na+ floods into the cell, depolarizing it more (more +ve) during the rising phase until action potential is attained. The rising phase only lasts ~a msec.

4. Na+ channels are fast acting and close about ~1 msec, so the action potential is a maximum of about 40+mV

5. Slower acting K+ voltage gated channels open at this tim, allowing K+ to rush out of the cell during the falling phase, returning the cell to a relatively -ve value compared to outside

6. Again, K+ channls are slow compared to Na+ channels, and do not close until after the resting potential is crossed. This results in an undershoot where the cell is hyperpolarized — briefly more negative than its resting potential. The Na+/K+ pump then returns the region to its resting potential

   • During the undershoot, this region of the cell experiences a refractory priod where a second action potential cannot be initated. The Na+/K+ pump and leaky K+ channels then return the region to its resting potential.

c) Discuss the role myelin sheath in nervous conductions (2 mark)

The myelin sheath insulates axons in vertebrates and increases the speed of action potentials through saltatory conduction. This process allows the electrical impulse to "jump" from one Node of Ranvier to the next, bypassing the myelinated sections of the axon.

Label the neuron

a) Label the diagram of a chemical synapse (3 marks)

b) Describe the sequence of events (including the result) that occur at a chemical synapse when an action potential arrives. Use (choose a specific example) of either an excitatory neurotransmitter OR an inhibitory neurotransmitter in your description (4+ marks)

b) When the action potential reaches the axon terminal of the presynaptic neuron, it triggers the opening of the voltage-gated calcium channels. Ca2+ ions flow into the axon terminal due to their higher concentration outside the cell. The influx of Ca²⁺ causes synaptic vesicles containing the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) to fuse with the presynaptic membrane, and GABA is released into the synaptic cleft. GABA diffuses across the synaptic cleft and binds to ligand-gated chloride (Cl⁻) ion channels on the postsynaptic membrane. When GABA binds, the Cl⁻ channels open, allowing Cl⁻ ions to flow into the postsynaptic neuron. This makes the inside of the postsynaptic neuron more negative (hyperpolarization), causing an inhibitory postsynaptic potential (IPSP). This reduces the likelihood that the postsynaptic neuron will reach the threshold for firing an action potential.

For an EPSP

When an action potential reaches the axon terminal of the presynaptic neuron, it causes voltage-gated calcium (Ca²⁺) channels to open. Ca²⁺ ions flow into the terminal due to their higher concentration outside the cell. The influx of Ca²⁺ triggers synaptic vesicles containing the excitatory neurotransmitter glutamate to fuse with the presynaptic membrane, and then it is released into the synaptic cleft by exocytosis. Glutamate diffuses across the cleft and binds to ligand-gated sodium channels) on the postsynaptic membrane. This binding opens the channels, allowing Na⁺ ions to flow into the postsynaptic neuron. The influx of Na⁺ causes the postsynaptic membrane to become less negative, creating an excitatory postsynaptic potential (EPSP). If the EPSP is strong enough to reach the threshold potential (~-55 mV), it triggers an action potential in the postsynaptic neuron. The action potential generated in the postsynaptic neuron continues to propagate the signal, contributing to excitation and communication in the nervous system.

BONUS: The cone snail Conus geographus is one of the larger cone snail species that eat fish… Explain why these cone snails can be so dangerous to divers (2 marks)

 bright and colourful, yet deadly: kills prey with venom that disables neurons (nerve cells). If injected into a diver, it can cause severe, fatal symptoms.

The graph shows the action potentials recorded at the target neuron (the cell body shown). E1 and E2 are axons/axon terminals of incoming excitatory presynaptic neurons, while I is an inhibitory presynaptic neurons. As an example: In 1, the action potential comes only from E1… E2 and I are not firing (no red arrows)

Explain what happened (and why) to the electric potential in the target neuron for all four cases. Do not describe the events within the synapse, deal only with the overall effect on the post synaptic target cell (6 marks)

(picture wont have labels on the test…)

a) This is a subthreshold where single excitatory postsynaptic potentials (EPSPs) are produced by E₁. The signals cause small depolarizations but are too far apart in time to summate. Since the membrane potential doesn't reach the threshold at the axon hillock, no action potential is generated.

b) This is called temporal summation, when two EPSPs are produced in the same synapse (E1) in rapid succession. The second signal adds to the first before the first fully decays, resulting in a summation of their effects. This summation depolarizes the membrane enough to reach the threshold, triggering an action potential.

c) This is called spatial summation, where EPSPs are generated nearly simultaneously at two different synapses (E₁ and E₂). The combined depolarizations summate, allowing the membrane potential to reach the threshold and initiate an action potential.

d) This is a spatial summation of EPSP and IPSP. An excitatory signal from E₁ generates a slight depolarization, but it doesn't reach the threshold. Meanwhile, an inhibitory postsynaptic potential (IPSP) from I hyperpolarizes the membrane, opposing the depolarization. When E₁ and I fire together, the EPSP and IPSP cancel each other out, preventing the membrane potential from reaching the threshold and inhibiting an action potential.

The human reproductive cycle is coordinated by tropic hormones and sex hormones in anootther hormone cascade (10 marks)

a) Fill in the missing hormones

The human reproductive cycle is coordinated by tropic hormones and sex hormones in anootther hormone cascade

b) Why are FSH and LH described as gonadotropic hormones?

FSH and LH are described as gonadotropic hormones because they help regulate the function of the gonads (testes and ovaries). These hormones are produced and secreted by the anterior pituitary gland and play key roles in the reproductive processes. In females, FSH stimulates the growth and maturation of ovarian follicles, while LH triggers ovulation and the formation of the corpus luteum. In males, FSH promotes spermatogenesis (sperm production) in the testes, and LH stimulates the production of testosterone.

The human reproductive cycle is coordinated by tropic hormones and sex hormones in anootther hormone cascade (10 marks)

c) Describe why estrogen’s role in the cycle is so interesting and explain what the effects on the targets are

Estrogen plays a central and interesting role in regulating the human reproductive cycle. During the follicular phase, estrogen levels start off low and gradually increase as it is produced by the developing ovarian follicles. Initially, this has a negative feedback effect, decreasing the release of FSH from the pituitary gland.

As estrogen levels continue to rise, it stimulates the thickening of the endometrial wall in preparation for potential pregnancy. Once estrogen levels reach a critical threshold, it exerts a positive feedback mechanism on the hypothalamus and anterior pituitary. This leads to an increase in GnRH, LH, and FSH secretion. The surge in LH and FSH causes ovulation (around day 14), marking the peak of estrogen’s positive feedback effect.

The high LH levels also stimulate the empty follicle to develop into the corpus luteum, which secretes both estrogen and progesterone. These hormones now exert a negative feedback effect, causing a drop in FSH and LH levels to prevent the development of a new follicle.

If fertilization does not occur, the corpus luteum breaks down, leading to a decline in estrogen and progesterone levels. As these hormone levels fall, FSH begins to rise again, and the uterine wall breaks down, resulting in menstruation, which marks the start of a new cycle.

d) A blood test for pregnancy is performed by a technician. Explain which hormone is useful in determining the women’s status (ie. pregnant or not)

Pregnancy tests detect a hormone called human chorionic gonatropin (hCG). hCG supports the pregnancy by maintaining the corpus luteum, which continues to secrete progesterone and estrogen. These hormones prevent the breakdown of the uterine lining and support the early stages of pregnancy. The levels of hCG rise rapidly during the first trimester, making it a reliable marker for early pregnancy detection.