Homeostasis

Question 1

Homeostasis

Answer 1

Process by which organisms maintain a stable internal environment (e.g., temperature, pH, blood sugar) despite external changes.

Question 2

Feedback Loops: Components

Answer 2

Stimulus → Receptor → Control Center → Effector → Response

Question 3

Negative Feedback

Answer 3

Decreases stimulus; e.g., thyroid regulation (TRH → TSH → T3/T4 → metabolic balance).

Question 4

Positive Feedback

Answer 4

Amplifies stimulus; e.g., labor contractions (pressure → oxytocin → stronger contractions).

Question 5

Structure of Neurons

Answer 5

1. Cell Body: Contains nucleus, organelles.
2. Dendrites: Receive signals.
3. Axon: Sends signals.

Question 6

Types of Neurons (3 main types)

Answer 6

Sensory (Afferent): Body → CNS.
Interneurons: In CNS; process information.
Motor (Efferent): CNS → muscles/glands.

Question 7

Resting Potential (RP)

Answer 7

70 mV; maintained by Na⁺/K⁺ pump.

Question 8

Threshold Potential (TP)

Answer 8

-55 mV triggers AP

Question 9

Phases

Answer 9

1. Depolarization: Na⁺ influx.
2. Repolarization: K⁺ efflux.
3. Hyperpolarization: Brief overshoot before RP restored.

Question 10

Non-Myelinated Axons

Answer 10

Continuous, slower.

Question 11

Myelinated Axons:

Answer 11

Saltatory conduction (jumps between Nodes of Ranvier), faster and energy-efficient.

Question 12

Synaptic Transmission

Answer 12

AP reaches terminal → Ca²⁺ influx.
Neurotransmitters (e.g., acetylcholine) released into synaptic cleft.
NTs bind to receptors → triggers response (EPSP/IPSP)

Question 13

CNS consists of…

Answer 13

Brain, spinal cord (integration and processing).

Question 14

PNS consists of….

Answer 14

Nerves (sensory input and motor output).

Question 15

Somatic Nervous System

Answer 15

Voluntary movements and conveys sensory information

Question 16

Autonomic Nervous System

Answer 16

Regulates involuntary functions like heart rate, digestion, and respiration.

Question 17

Sympathetic Nervous System:

Answer 17

Prepares the body for stress or emergency (fight or flight response).

Question 18

Parasympathetic Nervous System:

Answer 18

Promotes relaxation and recovery (rest and digest).

Question 19

Endocrine Glands

Answer 19

Secrete hormones directly into bloodstream (e.g., pancreas for insulin).

Question 20

Exocrine Glands

Answer 20

Secrete substances via ducts (e.g., sweat glands).

Question 21

2 types of Hormones, and how they function

Answer 21

Peptide Hormones: Water-soluble; act via second messengers (e.g., cAMP).

Steroid Hormones: Lipid-soluble; directly regulate gene expression.

Question 22

Pituitary Gland (two types and what they secrete)

Answer 22

Posterior: Stores/releases ADH, oxytocin.

Anterior: Produces GH, TSH, ACTH, FSH, LH, prolactin.

Question 23

Adrenal Gland (Parts and function- what they secrete)

Answer 23

Cortex: Cortisol (stress), aldosterone (Na⁺/water balance).
Medulla: Adrenaline (short-term stress response).

Question 24

Thyroid/Parathyroid (What they secrete + function)

Answer 24

Thyroid: T3/T4 (metabolism), calcitonin (lowers Ca²⁺).
Parathyroid: PTH (raises Ca²⁺)

Question 25

Pancreas (What it secretes + function)

Answer 25

Sugar Control: Insulin: Lowers blood sugar (beta cells). Glucagon: Raises blood sugar (alpha cells).

Question 26

Reflex Arcs

Answer 26

Stimulus → Sensory Neuron → Interneuron (CNS) → Motor Neuron → Effector. Example: Flinching from pain.

Question 27

Kidney (homeostasis) Functions

Answer 27

Water balance, toxin removal, pH regulation.

Question 28

ADH (Function + How it works)

Answer 28

Water reabsorption: - When the hypothalamus senses there's issues with BP pH and sometimes CO2 it sends a signal to the posterior pituitary to release ADH - ADH targets Kidneys collecting ducts --> Effect: Opens aquaporins → H2O reabsorbed

Question 29

Aldosterone (Function + How it works)

Answer 29

- Secreted by adrenal cortex - Targets DCT (Distal Convoluted Tubule) cells, promoting Na+ and water reabsorption, increasing blood pressure.

Question 30

Structure of Kidneys

Answer 30

Renal Arteries/Veins: Blood transport. Nephrons: Filtration and reabsorption.

Question 31

Estrogen/Progesterone

Answer 31

Reproductive hormone that regulates menstrual cycle & secondary sex traits.

Question 32

Testosterone

Answer 32

Reproductive hormone that is involved in sperm production, secondary sex traits.

Question 33

FSH/LH

Answer 33

Repreoductive hormone that triggers gamete production and ovulation/testosterone release.

Question 34

What is forced filtration? (in the nephron)

Answer 34

The process where blood pressure forces small molecules like water, glucose, salts, and urea through glomerular capillaries into the Bowman's capsule. Large molecules (e.g., proteins) stay in the blood.

Question 35

Where does reabsorption occur, and what is its purpose?

Answer 35

Reabsorption occurs mainly in the proximal tubule but also in the loop of Henle, distal tubule, and collecting duct. It retrieves useful substances like glucose, amino acids, water, and salts back into the bloodstream.

Question 36

What substances are reabsorbed in the nephron?

Answer 36

Glucose and amino acids: Actively reabsorbed. Water: Reabsorbed by osmosis. Salts: Reabsorbed based on the body’s needs (regulated by hormones like aldosterone).

Question 37

What is secretion in the nephron?

Answer 37

The active transport of substances like H+ ions, drugs, and toxins from the blood into the nephron, especially in the distal tubule, to maintain pH and remove waste.

Question 38

What is excretion, and how does it happen?

Answer 38

The final step in the nephron where urine (containing waste and excess substances) is removed from the body.