Urinary system

Comprehensive vocabulary flashcards covering the structural anatomy, physiological processes, and endocrine control of the human nervous and urinary systems based on lecture notes from Chapters 11 and 12.

Motor neurons

Nerve cells that carry impulses (action potentials) from the central nervous system to effectors such as muscles, organs, and glands; characterized by a long axon and short dendrites.

Sensory neurons

Nerve cells that carry impulses from sensory receptors to the central nervous system; characterized by a long dendrite and a shorter axon.

Interneurons

Nerve cells located solely in the central nervous system that carry impulses from sensory neurons to motor neurons; characterized by short dendrites and short axons.

Myelin sheath

A protective covering composed of Schwann cells surrounding axons that enables rapid impulse propagation at velocities up to $150\text{ m/s}$ (compared to $0.5\text{ to }10\text{ m/s}$ for non-myelinated axons).

Multiple sclerosis (MS)

An autoimmune disease where white blood cells attack and destroy the protective myelin sheath, disrupting the normal conduction of nerve impulses.

Structure 'X' (on the axon)

Schwann cells; specialized neuroglial cells that wrap around the axon to collectively produce the fatty insulating layer known as the myelin sheath.

Nodes of Ranvier

Small exposed gaps between Schwann cells along a myelinated axon where ion gates are concentrated, allowing action potentials to jump from node to node.

Saltatory conduction

The mechanism by which nerve impulses 'jump' from one node of Ranvier to the next along a myelinated axon, allowing impulses to travel at speeds up to $700\text{ km/h}$.

Resting membrane potential (RMP)

The electrical potential across a neuron's membrane at rest ($-65\text{ mV}$ to $-70\text{ mV}$), maintained by a higher concentration of $\text{Na}^+$ ions outside and a higher concentration of $\text{K}^+$ ions and negative organic anions inside.

Depolarization

The rapid phase of an action potential reaching $+40\text{ mV}$, triggered when a stimulus reaches threshold and causes gated sodium channels to open, allowing $\text{Na}^+$ ions to rush into the cell via facilitated diffusion.

Repolarization

The downward phase of an action potential returning toward resting potential, caused by the opening of potassium gates and the rapid exit of $\text{K}^+$ ions via facilitated diffusion.

Refractory period

The recovery phase of a nerve impulse where the $\text{Na}^+/\text{K}^+$ pump uses active transport and ATP to restore original ion distribution by pumping $\text{Na}^+$ out and $\text{K}^+$ back in.

Integration

The process by which a postsynaptic neuron sums and processes all incoming excitatory and inhibitory signals from multiple presynaptic neurons to determine whether an action potential will be initiated.

Cholinesterase

An enzyme released into the synaptic cleft that breaks down the neurotransmitter acetylcholine to prevent continuous stimulation of the postsynaptic neuron.

Dopamine

A brain neurotransmitter responsible for producing sensations of pleasure and controlling movements; its diminished production causes Parkinson's disease.

Reflex arc

A rapid, automatic neural circuit bypassing the brain that carries impulses directly from a sensory receptor to a sensory neuron, interneuron in the spinal cord, motor neuron, and effector organ.

Somatic nervous system

A division of the peripheral nervous system comprising motor neurons that control voluntary conscious movements (such as running) as well as involuntary reflex actions (such as blinking).

Autonomic nervous system

A division of the peripheral nervous system that regulates involuntary physiological functions and visceral organs not under conscious control, such as heart pumping, digestion, and hormone secretion.

Sympathetic nervous system

The autonomic division governing 'fight or flight' responses during stress; uses norepinephrine to dilate pupils, dilate bronchi, accelerate heart rate, and inhibit digestion.

Parasympathetic nervous system

The autonomic division governing 'rest or digest' responses; uses acetylcholine to constrict pupils, slow heart rate, stimulate saliva, and promote digestive and urinary activity.

Cerebrum

The upper part of the brain responsible for sensation, conscious thought processes, and voluntary motor control.

Cerebellum

The brain structure that organizes outgoing motor impulses to ensure movements are smooth and coordinated, while maintaining balance and posture.

Hypothalamus

The brain region linking the nervous system to the endocrine system by releasing hormones that control pituitary secretions and monitoring homeostatic parameters such as blood osmolarity.

Thalamus

A sensory relay center in the brain that receives and routes incoming sensory information to the upper brain regions.

Corpus callosum

A thick band of nerve fibers connecting the left and right cerebral hemispheres, allowing information to pass between them.

Medulla oblongata

A brainstem structure that regulates vital metabolic functions including breathing, blood pressure, and heart rate, as well as reflex actions like coughing, vomiting, swallowing, and hiccoughing.

Pituitary gland

An endocrine master gland located in the brain that secretes hormones governing metabolic rate, water balance, sexual maturity, and the menstrual cycle under hypothalamic guidance.

Adrenal cortex

The outer region of the adrenal gland that secretes steroid hormones including cortisol (targeting all tissues), aldosterone (targeting the kidneys), and sex hormones.

Adrenal medulla

The inner region of the adrenal gland that secretes adrenaline (epinephrine) and noradrenaline (norepinephrine) to trigger rapid fight-or-flight responses in cardiac and other muscles.

Erythropoietin

A hormone released by the kidneys that stimulates red blood cell production to support blood oxygen-carrying capacity.

Renal cortex

The outer region of the kidney containing the majority of nephron tubules, including each nephron's glomerulus and Bowman's capsule.

Renal medulla

The central hypertonic region of the kidney containing the loops of Henle and nephron collecting ducts.

Renal pelvis

The funnel-shaped basin of the kidney that collects urine from the collecting ducts and channels it directly into the ureter.

Renal artery

The blood vessel that carries arterial blood high in urea and oxygen from the aorta to the kidneys.

Renal vein

The blood vessel that carries filtered venous blood low in urea and oxygen away from the kidneys toward the inferior vena cava.

Afferent arteriole

The vessel branching from the renal artery that brings blood into the glomerulus capillary bed under high pressure.

Glomerulus

A specialized capillary tuft situated between the afferent and efferent arterioles that filters blood into Bowman's capsule via pressure filtration.

Efferent arteriole

The vessel that carries concentrated blood leaving the glomerulus into the peritubular capillary network.

Peritubular capillary network (PCN)

A network of capillaries surrounding the nephron tubules that reclaims reabsorbed water and nutrients and receives secreted substances before draining into venules.

Pressure filtration

The non-selective movement of water, salts, urea, glucose, and amino acids across the glomerular capillaries into Bowman's capsule under high pressure, leaving behind blood cells and large proteins.

Selective reabsorption

The reclamation of approximately $98\%$ of the glomerular filtrate (including glucose, amino acids, and water) from the nephron tubules back into the peritubular capillary blood, leaving about $2\text{ ml}$ out of $100\text{ ml}$ to become urine.

Proximal convoluted tubule (PCT)

The initial convoluted portion of the nephron responsible for the active reabsorption of glucose and amino acids and the passive reabsorption of water.

Loop of Henle

The hairpin-shaped tubule extending into the renal medulla; its ascending limb actively pumps $\text{Na}^+$ (with $\text{Cl}^-$ following) into the medulla to create a hypertonic environment that draws water from the descending limb and collecting duct.

Tubular secretion

The active transport of substances—including metabolic wastes, drug residues (such as antibiotics), and $\text{H}^+$ or $\text{HCO}_3^-$ ions—from peritubular capillaries directly into the distal convoluted tubule to regulate blood pH and excrete wastes.

Antidiuretic hormone (ADH)

A hormone released by the posterior pituitary (prompted by the hypothalamus) that increases the water permeability of the distal convoluted tubule and collecting duct, concentrating urine and expanding blood volume.

Aldosterone

A steroid hormone secreted by the adrenal cortex in response to renin that stimulates the reabsorption of $\text{Na}^+$ and excretion of $\text{K}^+$ in the distal convoluted tubule and collecting duct, drawing water back into the blood to restore blood pressure.

Juxtaglomerular apparatus

A specialized group of cells located near the glomerulus that detects drops in blood pressure and responds by secreting the hormone renin into the bloodstream.