Final Homeostasis

What is homeostasis and why is it considered a dynamic equilibrium?

Homeostasis is the maintenance of a stable internal environment by keeping variables near a set point. It is a dynamic equilibrium because conditions constantly change, but feedback mechanisms continuously restore balance.

Describe a homeostatic feedback loop and how it maintains stability.

A stimulus disrupts a variable → receptors detect the change → the control centre processes information → effectors create a response → the variable returns toward the set point.

Explain negative feedback and why it is important for homeostasis.

Negative feedback reverses a change and returns a variable toward its set point. It is the main mechanism of homeostasis, such as regulating temperature and blood glucose.

Explain positive feedback and give an example.

Positive feedback amplifies a change until a specific endpoint is reached. During childbirth, cervical pressure causes oxytocin release, which increases contractions until birth occurs.

Compare the endocrine and nervous systems.

The endocrine system uses hormones carried through blood to create slower, longer-lasting, widespread effects. The nervous system uses electrical impulses and neurotransmitters to create rapid, short-term, localized effects.

What are hormones, receptors, target cells, endocrine glands, and exocrine glands?

Hormones are chemical messengers released by endocrine glands. Target cells contain specific receptors that bind hormones and trigger responses. Endocrine glands release hormones into blood, while exocrine glands release substances through ducts.

How do the hypothalamus and pituitary gland connect the nervous and endocrine systems?

The hypothalamus detects internal conditions and controls the pituitary gland. The pituitary releases hormones that regulate growth, metabolism, reproduction, and water balance.

Explain blood glucose regulation as a negative feedback loop.

The pancreas monitors blood glucose. High glucose causes insulin release, causing cells to absorb glucose and the liver to store glycogen. Low glucose causes glucagon release, causing the liver to break down glycogen and release glucose.

What happens when blood glucose is too high?

Pancreatic β-cells release insulin. Insulin causes body cells to take in glucose and the liver to convert glucose into glycogen, lowering blood glucose.

What happens when blood glucose is too low?

Pancreatic α-cells release glucagon. Glucagon causes the liver to break down glycogen into glucose, increasing blood glucose.

What are the major pituitary hormones and their functions?

GH stimulates growth; TSH stimulates the thyroid; ACTH stimulates the adrenal cortex; FSH controls gamete production; LH triggers ovulation or testosterone production; prolactin stimulates milk production; ADH controls water retention; oxytocin causes contractions and milk ejection.

What hormones are produced by the thyroid and what are their functions?

T3 and T4 increase metabolism, while calcitonin lowers blood calcium levels.

What hormones are produced by the adrenal glands and what are their functions?

The adrenal cortex produces cortisol for long-term stress and aldosterone for salt/water balance. The adrenal medulla produces epinephrine and norepinephrine for fight-or-flight responses.

How does the pancreas function as an endocrine gland?

The pancreas releases insulin to decrease blood glucose and glucagon to increase blood glucose through negative feedback.

Explain how reproductive hormones are controlled by the endocrine system.

The hypothalamus releases GnRH → pituitary releases FSH and LH → testes or ovaries produce gametes and sex hormones → sex hormones provide feedback to regulate the system.

Describe the male reproductive system and how sperm is produced.

The testes produce sperm and testosterone. Sperm develops in seminiferous tubules, matures in the epididymis, travels through the vas deferens, and combines with fluids from glands to form semen.

Describe the structure of a sperm cell and how each part helps its function.

The head contains DNA and an acrosome with enzymes to penetrate the egg. The midpiece contains mitochondria that produce ATP. The tail allows movement.

Explain spermatogenesis.

Spermatogenesis occurs in seminiferous tubules where diploid spermatogonia undergo meiosis to produce haploid sperm cells. The sperm mature in the epididymis.

What roles do FSH, LH, and testosterone play in males?

FSH stimulates Sertoli cells and sperm production. LH stimulates Leydig cells to produce testosterone, which supports sperm production and male secondary sex characteristics.

What are gametes, meiosis, diploid cells, and haploid cells?

Gametes are haploid sex cells produced through meiosis. Diploid cells contain two chromosome sets (2n), while haploid cells contain one chromosome set (n).

Compare spermatogenesis and oogenesis.

Spermatogenesis begins at puberty and continuously produces many sperm. Oogenesis begins before birth and usually produces one mature egg per menstrual cycle.

Describe the female reproductive system and the pathway of an egg.

Ovaries produce eggs and hormones. The follicle develops the egg, fimbriae guide it into the fallopian tube, fertilization occurs in the tube, and the uterus supports embryo development.

Explain the menstrual cycle using hormones.

FSH stimulates follicle development → follicles produce estrogen → estrogen thickens the endometrium → LH surge causes ovulation → progesterone maintains the endometrium → hormone levels fall if fertilization does not occur, causing menstruation.

What are the main reproductive hormones and their functions?

FSH stimulates follicle development and sperm production. LH triggers ovulation and testosterone production. Estrogen develops female traits and thickens the endometrium. Progesterone maintains the uterine lining. Testosterone supports sperm production and male traits.

Explain fertilization and early development.

Fertilization occurs in the fallopian tube when sperm penetrates the egg using acrosome enzymes. The sperm and egg nuclei combine to form a diploid zygote.

Describe the organization of the nervous system.

The central nervous system (CNS) contains the brain and spinal cord. The peripheral nervous system (PNS) connects the CNS to the body and includes the somatic system and autonomic system. The autonomic system includes sympathetic and parasympathetic divisions.

Compare sympathetic and parasympathetic nervous systems.

The sympathetic system produces fight-or-flight responses by increasing activity during stress. The parasympathetic system produces rest-and-digest responses by conserving energy and restoring normal conditions.

Describe the structure of a neuron and how it transmits information.

Dendrites receive signals, the cell body processes information, the axon carries impulses, myelin speeds conduction, and axon terminals release neurotransmitters to communicate with other cells.

Compare sensory neurons, interneurons, and motor neurons.

Sensory neurons carry information from receptors to the CNS. Interneurons process information within the CNS. Motor neurons carry commands from the CNS to muscles and glands.

Explain a reflex arc and why it is useful.

A stimulus activates a receptor → sensory neuron carries the signal → interneuron in the spinal cord processes it → motor neuron activates an effector. Reflexes are rapid because they bypass conscious brain processing.

Explain resting potential in neurons.

Resting potential is the negative charge inside a neuron (~−70 mV) maintained by the sodium-potassium pump, which moves 3 Na⁺ out and 2 K⁺ into the cell.

Explain the stages of an action potential.

When threshold (~−55 mV) is reached, Na⁺ channels open causing depolarization. Na⁺ channels close and K⁺ channels open causing repolarization. The neuron briefly hyperpolarizes before returning to resting potential.

Explain the all-or-none principle, refractory period, and saltatory conduction.

An action potential either occurs completely or does not occur. The refractory period prevents immediate refiring and ensures one-way movement. Saltatory conduction allows impulses to jump between Nodes of Ranvier, increasing speed.

Explain chemical synaptic transmission.

An action potential reaches the axon terminal → Ca²⁺ enters → neurotransmitters are released → they cross the synapse → bind receptors on the next cell → neurotransmitters are removed by enzymes or reuptake.

What are the major lobes of the brain and their functions?

The frontal lobe controls decision-making and movement. The parietal lobe processes touch and body sensations. The temporal lobe processes hearing and memory. The occipital lobe processes vision.

What are the major brain structures and their functions?

The hypothalamus maintains homeostasis and controls endocrine activity. The pituitary releases hormones. The hippocampus supports long-term memory. The spinal cord relays information and controls reflexes.

What happens during a seizure from a nervous system perspective?

A seizure occurs when groups of neurons undergo uncontrolled, abnormal electrical activity. This disrupts normal brain communication and can cause changes in movement, sensation, or awareness.