Homeostasis Flashcards
Homeostasis
Process by which organisms maintain a stable internal environment (e.g., temperature, pH, blood sugar) despite external changes.
Feedback Loops: Components
Stimulus → Receptor → Control Center → Effector → Response
Negative Feedback
Decreases stimulus; e.g., thyroid regulation (TRH → TSH → T3/T4 → metabolic balance).
Positive Feedback
Amplifies stimulus; e.g., labor contractions (pressure → oxytocin → stronger contractions).
Structure of Neurons
- Cell Body: Contains nucleus, organelles.
- Dendrites: Receive signals.
- Axon: Sends signals.
Types of Neurons (3 main types)
Sensory (Afferent): Body → CNS.
Interneurons: In CNS; process information.
Motor (Efferent): CNS → muscles/glands.
Resting Potential (RP)
70 mV; maintained by Na⁺/K⁺ pump.
Threshold Potential (TP)
-55 mV triggers AP
Phases
- Depolarization: Na⁺ influx.
- Repolarization: K⁺ efflux.
- Hyperpolarization: Brief overshoot before RP restored.
Non-Myelinated Axons
Continuous, slower.
Myelinated Axons:
Saltatory conduction (jumps between Nodes of Ranvier), faster and energy-efficient.
Synaptic Transmission
AP reaches terminal → Ca²⁺ influx.
Neurotransmitters (e.g., acetylcholine) released into synaptic cleft.
NTs bind to receptors → triggers response (EPSP/IPSP)
CNS consists of…
Brain, spinal cord (integration and processing).
PNS consists of….
Nerves (sensory input and motor output).
Somatic Nervous System
Voluntary movements and conveys sensory information
Autonomic Nervous System
Regulates involuntary functions like heart rate, digestion, and respiration.
Sympathetic Nervous System:
Prepares the body for stress or emergency (fight or flight response).
Parasympathetic Nervous System:
Promotes relaxation and recovery (rest and digest).
Endocrine Glands
Secrete hormones directly into bloodstream (e.g., pancreas for insulin).
Exocrine Glands
Secrete substances via ducts (e.g., sweat glands).
2 types of Hormones, and how they function
Peptide Hormones: Water-soluble; act via second messengers (e.g., cAMP).
Steroid Hormones: Lipid-soluble; directly regulate gene expression.
Pituitary Gland (two types and what they secrete)
Posterior: Stores/releases ADH, oxytocin.
Anterior: Produces GH, TSH, ACTH, FSH, LH, prolactin.
Adrenal Gland (Parts and function- what they secrete)
Cortex: Cortisol (stress), aldosterone (Na⁺/water balance).
Medulla: Adrenaline (short-term stress response).
Thyroid/Parathyroid (What they secrete + function)
Thyroid: T3/T4 (metabolism), calcitonin (lowers Ca²⁺).
Parathyroid: PTH (raises Ca²⁺)
Pancreas (What it secretes + function)
Sugar Control:
Insulin: Lowers blood sugar (beta cells).
Glucagon: Raises blood sugar (alpha cells).
Reflex Arcs
Stimulus → Sensory Neuron → Interneuron (CNS) → Motor Neuron → Effector.
Example: Flinching from pain.
Kidney (homeostasis) Functions
Water balance, toxin removal, pH regulation.
ADH (Function + How it works)
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
Aldosterone (Function + How it works)
- Secreted by adrenal cortex
- Targets DCT (Distal Convoluted Tubule) cells, promoting Na+ and water reabsorption, increasing blood pressure.
Structure of Kidneys
Renal Arteries/Veins: Blood transport.
Nephrons: Filtration and reabsorption.
Estrogen/Progesterone
Reproductive hormone that regulates menstrual cycle & secondary sex traits.
Testosterone
Reproductive hormone that is involved in sperm production, secondary sex traits.
FSH/LH
Repreoductive hormone that triggers gamete production and ovulation/testosterone release.
What is forced filtration? (in the nephron)
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.
Where does reabsorption occur, and what is its purpose?
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.
What substances are reabsorbed in the nephron?
Glucose and amino acids: Actively reabsorbed.
Water: Reabsorbed by osmosis.
Salts: Reabsorbed based on the body’s needs (regulated by hormones like aldosterone).
What is secretion in the nephron?
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.
What is excretion, and how does it happen?
The final step in the nephron where urine (containing waste and excess substances) is removed from the body.
