Ch4: Homeostasis

Question 1

What is the difference between a typical neural circuit and a reflex arc?

Answer 1

A typical neural circuit involves the brain for processing and decision-making, while a reflex arc bypasses the brain to enable a rapid, involuntary response.

Typical Neural Circuit: sensory information is detected by a sensory receptor, relayed to the spinal cord, and then sent to the brain for processing and integration. After the brain interprets the information and makes a decision, a signal is sent back down the spinal cord to a motor neuron, which then relays the message to muscles, organs, or glands to produce a response.

Reflex Arc: A reflex arc is a faster and simpler neural pathway designed for immediate responses to stimuli, often bypassing the brain. In a reflex arc, a stimulus (like touching something hot) is detected by a sensory receptor, and the signal travels along a sensory neuron to the spinal cord. At the spinal cord, an interneuron directly relays the information to an efferent (motor) neuron, which immediately stimulates an effector (such as a muscle) to produce a quick, involuntary action. For example, if you touch a burning match, your finger is pulled away very quickly, even before you consciously register the pain. While this immediate action occurs, a separate signal is simultaneously sent up to the brain to inform it of what happened, but the brain is not involved in the decision to move the hand. This direct routing allows for critical, rapid responses that enhance survival by preventing severe injury.

Question 2

Describe how a message is passed from one neuron to to another.

Answer 2

Messages are passed from one neuron to another across a specialized gap called a synapse. The neuron transmitting the signal is known as the presynaptic neuron, and the neuron receiving the signal is the postsynaptic neuron.

Question 3

What is the primary function of neurons within the nervous system?

a) Providing structural support to nerve tissue.
b) Nourishing and removing waste from nerve cells.
c) Responding to physical and chemical stimuli and conducting electrochemical signals.
d) Defending against infection in nerve tissue.

Answer 3

C

Question 4

At resting membrane potential, what is the typical charge difference between the inside and outside of a neuron?

Answer 4

-70 mV

Question 5

The sodium-potassium pump is crucial for maintaining the resting membrane potential. How many sodium (Na+) ions does it typically pump out for every potassium (K+) ions pumped in?

Answer 5

3 Na+ out for ever 2 K+ in

Question 6

Which event primarily characterizes the depolarization phase of an action potential?

a) Potassium ions rushing out of the cell
b) Sodium ions rushing into the cell
c) Voltage-gated potassium channels closing
d) The membrane becoming more negative inside

Answer 6

B

Question 7

What is the approximate threshold level that the membrane potential must reach to trigger an action potential in a neuron?

Answer 7

-55 mV

Question 8

During the repolarization phase of an action potential, which of the following events primarily occurs?

a) Voltage-gated sodium channels open and sodium rushes in.
b) Voltage-gated potassium channels close, trapping potassium inside.
c) Voltage-gated potassium channels open and potassium rushes out of the cell.
d) The membrane becomes hyperpolarized.

Answer 8

C

Question 9

What is the gap between two neurons called, across which chemical messengers are transmitted?

Answer 9

synapse

Question 10

Which of the following is true about the absolute refractory period?

a) The neuron can fire another action potential if the stimulus is strong enough.
b) It occurs during hyperpolarization.
c) Voltage-gated sodium channels are inactivated, preventing another action potential.
d) It allows action potentials to travel backwards along the axon.

Answer 10

C

Question 11

What type of cells are specialized to support neurons by nourishing, removing wastes, and defending against infection?

Answer 11

Glial cells

Question 12

When neurotransmitters have an excitatory effect on a postsynaptic neuron, what typically happens?

Answer 12

Sodium channels open, leading to depolarization and re-initiation of an action potential.

Question 13

If the voltage-gated potassium channels in a neuron were to open much faster than normal and close more slowly, what would be the most likely consequence for the action potential?

a) The depolarization phase would be prolonged and reach a higher peak.
b) The repolarization phase would be accelerated, and the hyperpolarization (undershoot) would be more pronounced and prolonged.
c) The threshold potential would become more negative, making it harder to fire.
d) The resting membrane potential would be permanently stuck at +30 mV.

Answer 13

B

Question 14

The nervous system is broadly divided into two main components. What are these two divisions?

Answer 14

The two main divisions of the nervous system are the Central Nervous System (CNS), which includes the brain and spinal cord, and the Peripheral Nervous System (PNS), which includes all other parts of the nervous system.

Question 15

Which type of neuron is responsible for relaying environmental information from sensory receptors to the Central Nervous System (CNS) for processing?

Answer 15

Sensory neurons

Question 16

What are the chemical messengers that carry neural signals across the synaptic gap from one neuron to another?

Answer 16

Neurotransmitters

Question 17

How are neurotransmitters released from the presynaptic axon terminal into the synaptic gap?

A) Through passive diffusion directly across the membrane
B) Via endocytosis into the synaptic cleft
C) By vesicles fusing with the presynaptic membrane and releasing contents through exocytosis
D) Actively pumped across by the sodium-potassium pump

Answer 17

C.

The action potential stimulates the release of neurotransmitters, which diffuse across the synapse in vesicles and bind to the dendrites on the postsynaptic neuron. Vesicles release neurotransmitters into the synapse via exocytosis.

Question 18

What is the primary function of the myelin sheath that surrounds some axons?

Answer 18

The myelin sheath is an insulating layer that allows the signal to hop from node to node, resulting in faster nerve signal travel.

Question 19

A reflex arc is a rapid neural circuit that allows for quick responses to stimuli by bypassing which part of the nervous system?

Answer 19

The brain

Question 20

The effect on the postsynaptic neuron will be determined by the sum of all the effects of the neurotransmitters released.

Answer 20

Summation

Question 21

Which cells in the male testes are responsible for producing testosterone?

a) Sertoli cells
b) Seminiferous tubules
c) Interstitial cells
d) Follicular cells

Answer 21

C

Question 22

What is one of the effects of testosterone in males?

a) Shedding of the endometrial lining
b) Stimulation of sperm creation
c) Formation of the corpus luteum
d) Inhibition of LH release by stimulating GnRH

Answer 22

B

Question 23

Which hormone, released by the hypothalamus, initiates the release of FSH and LH from the anterior pituitary in both males and females?

Answer 23

GnRH

Question 24

In males, high levels of testosterone provide negative feedback to inhibit the further release of which hormone?

Answer 24

LH

Question 25

Sperm are produced in which part of the male reproductive organ?

Answer 25

Seminiferous tubules

Question 26

What are follicles in the ovary?

Answer 26

Groups of cells surrounding an ovum

Question 27

Which female hormones are produced by follicular cells?

Answer 27

Estrogen and progesterone

Question 28

What causes ovulation?

Answer 28

A massive spike in LH concentration

Question 29

After ovulation, the remaining follicular cells form a structure called the?

Answer 29

Corpus Luteam

Question 30

What is the primary hormone secreted by the corpus luteum that promotes the buildup of the endometrium and inhibits further ovulation?

Answer 30

Progesterone

Question 31

Birth control pills typically contain high concentrations of which hormone to inhibit ovulation?

Answer 31

Progesterone

Question 32

What hormone is secreted by the embryo to keep the corpus luteum from breaking down during pregnancy?

Answer 32

hCG

Question 33

At low concentrations, estrogen has what kind of feedback effect on the anterior pituitary regarding LH secretion?

Answer 33

Negative

Question 34

The luteal phase of the menstrual cycle is named for the formation of which structure?

Answer 34

Corpus Luteam

Question 35

Besides progesterone and a small amount of estrogen, what other hormone does the corpus luteum secrete that inhibits FSH release?

Answer 35

Inhibin

Question 36

What is the role of the corpus luteum in the menstrual cycle and early pregnancy, and what causes its eventual degeneration?

Answer 36

In the menstrual cycle, after ovulation, the remaining follicular cells transform into the corpus luteum (CL). The CL is crucial because it secretes essential hormones: progesterone (P), inhibin (I), and a small amount of estrogen (E). Progesterone, the most important hormone of the luteal phase, promotes the buildup of the endometrial lining, inhibits further ovulation, and inhibits contractions of the uterus, preparing the uterus for a potential pregnancy. Inhibin, along with progesterone, provides negative feedback to the anterior pituitary, inhibiting further FSH and LH release, which prevents new follicles from maturing. If pregnancy does not occur, the CL degenerates after about 10 days. This degeneration leads to a decrease in estrogen and progesterone levels. The drop in these hormones causes the endometrium to degenerate, leading to menstruation, and allows GnRH levels to increase, initiating a new cycle. If fertilization and implantation do occur, the embryo secretes human chorionic gonadotropin (hCG). hCG acts to prevent the CL from breaking down, ensuring that it continues to produce high levels of estrogen and progesterone to maintain the uterine lining and prevent menstruation, thus supporting the early pregnancy.

Question 37

What is menopause, and how does it relate to the female reproductive hormones?

Answer 37

Menopause is the process where female sex hormones cease to be secreted, signaling the end of a woman's reproductive life. It is described as a gradual process. Throughout a woman's reproductive years, her female hormone levels, specifically estrogen and progesterone, fluctuate as part of the menstrual cycle. Menopause marks the point when the ovaries no longer produce these hormones in significant amounts, leading to the cessation of menstrual cycles and the ability to reproduce. The sources indicate that the number of follicles a woman has decreases over time, with only some reaching maturation, and female hormone levels eventually cease to be secreted.

Question 38

How do birth control pills containing high concentrations of progesterone prevent conception?

Answer 38

Birth control pills containing high concentrations of progesterone prevent conception primarily by inhibiting ovulation. Progesterone, particularly at high levels, plays a key role in the negative feedback loop of the menstrual cycle. It inhibits the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus and subsequently the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary. Without the surge in LH, which is typically triggered by high estrogen levels later in the follicular phase, ovulation does not occur. By preventing the release of an egg, the pills effectively prevent conception. Additionally, progesterone also promotes the buildup of the endometrium, but in the context of birth control, its primary contraceptive action is inhibiting ovulation and contractions of the uterus.

Question 39

A male patient presents with symptoms of low sperm count and decreased sex drive. Based on the provided information, which hormone levels might be low, and what could be the potential cause related to the pituitary gland?

Answer 39

Given the symptoms of low sperm count and decreased sex drive, the patient likely has low testosterone levels. Testosterone stimulates sperm creation and is associated with sex drive. The control of testosterone production is linked to the pituitary and hypothalamus. If the anterior pituitary is not adequately releasing Luteinizing Hormone (LH), then the interstitial cells in the testes would not be sufficiently stimulated to produce testosterone. Therefore, a potential cause could be a dysfunction in the anterior pituitary leading to insufficient LH release

Question 40

A pregnant woman is in her first trimester. Her doctor explains that her corpus luteum is still active and crucial for maintaining the pregnancy. What hormone is the embryo secreting to ensure the corpus luteum remains active, and why is this continued activity vital?

Answer 40

The embryo is secreting human chorionic gonadotropin (hCG). This continued activity of the corpus luteum is vital because it secretes high levels of estrogen and progesterone, which are essential for maintaining the uterine lining and preventing menstruation. If the corpus luteum were to degenerate prematurely, as it would in a non-pregnant cycle, the decrease in these hormones would lead to the shedding of the endometrial lining, resulting in a miscarriage.

Question 41

A female athlete experiences amenorrhea (absence of menstruation) due to intense training and low body fat, which can impact hormone levels. If her estrogen levels are consistently low, how might this affect her FSH and LH levels based on the feedback mechanisms described in the early follicular phase?

Answer 41

In the early follicular phase, low concentrations of estrogen typically have a negative feedback effect on the pituitary, inhibiting LH release. Additionally, FSH is secreted primarily in response to low estrogen concentrations. If her estrogen levels are consistently low, it might paradoxically lead to elevated FSH levels, as FSH secretion is a response to low estrogen. However, the effect on LH might be less clear-cut from this specific information; while low estrogen inhibits LH, prolonged very low estrogen could also disrupt the entire cycle's progression, preventing the later estrogen surge needed for the LH spike. The initial effect described for low estrogen is inhibition of LH, and FSH levels would be higher if estrogen levels were low.

Question 42

A young woman at puberty is experiencing significant acne and muscle development. Based on the information, which hormone is primarily responsible for these changes, and what general category of changes do these fall under?

Answer 42

The hormone primarily responsible for these changes is testosterone. Although testosterone is a male sex hormone, it also contributes to secondary sex characteristics in females, albeit at much lower levels than in males. In the context of male puberty, the sources clearly state that testosterone stimulates secondary sex characteristics such as muscle development and acne. These changes fall under the category of "secondary sex characteristics" that appear at puberty.

Question 43

How do pregnancy tests work?

Answer 43

Pregnancy tests work by detecting the presence of human chorionic gonadotropin (hCG), a hormone secreted by the embryo. When an egg is fertilized, the developing embryo releases hCG. This hormone plays a crucial role in preventing the corpus luteum (CL) in the ovary from breaking down, which in turn ensures that the CL continues to secrete estrogen and progesterone to maintain the uterine lining and prevent menstruation during pregnancy. Additionally, hCG suppresses the mother's immune system to prevent the rejection of the baby.

Question 44

Steroid hormones act on specific target tissues by binding to receptors located where in the cell? a) Nucleus b) Cytosol c) Cell membrane d) Ribosomes

Answer 44

B

Question 45

Which natural steroid hormone is produced by the adrenal glands in response to stress and raises blood glucose levels?

Answer 45

Cortisol

Question 46

What are synthetic hormones designed to do?

Answer 46

Mimic the actions of natural hormones

Question 47

Synthetic steroids are important for transplant patients because they?

Answer 47

Suppress the immune system

Question 48

The negative perception of steroids comes largely from the illegal use of what type of steroids in sports?

Answer 48

Anabolic steroids

Question 49

Besides building muscle mass, what other performance-enhancing substance is mentioned that stimulates red blood cell production, leading to more oxygen transport and endurance?

Answer 49

EPO

Question 50

Compare and contrast natural steroid hormones and synthetic steroids based on their origin and general purpose.

Answer 50

Natural steroid hormones are those produced naturally in the body, such as testosterone, estrogens, progestins, aldosterone, and cortisol. They act on specific target tissues by binding to appropriate receptor molecules to regulate gene expression, controlling various body functions like muscle development, sexual development, stress response, and the menstrual cycle. Synthetic steroids are chemicals created by humans, designed to mimic the actions of natural hormones. Their general purpose can be for legitimate medical uses, such as suppressing the immune system to reduce organ rejection in transplant patients, reducing pain and inflammation in autoimmune disorders, or treating asthma. Some synthetic steroids, like anabolic steroids, are also misused for performance enhancement in sports.

Question 51

Compare and contrast the legitimate therapeutic uses of synthetic steroids with their use for performance enhancement in sports.

Answer 51

Legitimate therapeutic uses of synthetic steroids involve medical purposes under a doctor's supervision. They are important for transplant patients to suppress the immune system and reduce organ rejection, and they can reduce pain and inflammation for conditions like arthritis, asthma, and autoimmune disorders such as lupus. Examples include prednisone for lupus/transplantation, beclomethasone for asthma, dexamethasone for rheumatoid arthritis, and hydrocortisone for inflammatory skin disorders. Use for performance enhancement in sports typically involves the illegal use of anabolic steroids and other performance-enhancing substances. Athletes use these to gain an unfair advantage, primarily to build muscle mass (anabolic steroids) or stimulate red blood cell production for endurance (Erythropoietin/EPO). This use carries significant risks to health and reputation.

Question 52

Where are endocrine hormones produced and secreted?

Answer 52

In endocrine glands, secreted directly into the blood.

Question 53

Where do steroid hormones combine with receptor molecules within target cells?

Answer 53

In the cytoplasm

Question 54

Which type of hormone includes insulin and growth hormone?

Answer 54

Protein

Question 55

What are the two hormones produced by the adrenal medulla?

Answer 55

Epinephrine (adrenaline) and Norepinephrine (noradrenaline)