AN PHYS

A detailed collection of vocabulary flashcards covering neurophysiology mechanisms, ionic basis of resting and action potentials, synaptic transmission, thermal homeostasis, and anatomical functions of the central nervous system based on lecture transcripts.

Axon

A neuron process that transmits electrical information away from the cell body.

Dendrite

A neuron process that transmits electrical information toward the cell body.

Cell body (Neuron)

The central structural part of a neuron that integrates incoming and outgoing information.

Multipolar neuron

A structural category of neuron with multiple processes extending from the cell body, found primarily in the central nervous system.

Pseudounipolar neuron

A structural category of neuron possessing a single process that divides into two branches, found primarily in the peripheral nervous system.

Bipolar neuron

A structural category of neuron with two distinct processes, found mainly in specialized sensory organs.

Afferent neuron

A sensory neuron that transmits impulses from sensory receptors in the peripheral nervous system toward the central nervous system.

Efferent neuron

A motor neuron that transmits electrical signals from the central nervous system out to effector organs, such as muscles and glands.

Interneuron

An association neuron located entirely within the central nervous system that relays information between sensory and motor pathways.

Glial cells

Non-neuronal cells in nervous tissue that are roughly $10$ times more abundant than neurons and provide structural support, nutrient transport, and insulation.

Oligodendrocytes

Specialized glial cells responsible for synthesizing myelin sheaths around nerve fibers in the central nervous system.

Astrocytes

Glial cells that contact both blood vessels and neurons to transport nutrients, and secrete glutamate to modulate neuronal excitability.

Microglia

Glial cells in the nervous system that possess phagocytic activity to protect brain tissue.

Grey matter

Nervous tissue composed predominantly of neuronal cell bodies and unmyelinated elements.

White matter

Nervous tissue composed of myelinated nerve process bundles, deriving its color from lipid sheaths.

Ganglia

Clusters of sensory neuron cell bodies located outside of the central nervous system.

Myelin sheath

An electrical insulating layer composed of sphingomyelin lipid membranes wrapped around nerve axons.

Nodes of Ranvier

Uninsulated gaps in the myelin sheath occurring every $1\text{ to }2\text{ mm}$ along an axon that allow localized ion flow and action potential generation.

Resting membrane potential

The difference in electrical charge across a cell membrane at rest, averaging $-\text{70 to }-\text{90 mV}$ in nerve cells, with the inner membrane negative relative to the outside.

Na+/K+ pump

An active transport membrane pump that pumps $3\text{ Na}^+$ ions out of the cell and $2\text{ K}^+$ ions into the cell against concentration gradients, utilizing up to $40\%$ of cellular ATP.

Depolarization

The phase of an action potential characterized by the opening of voltage-gated $\text{Na}^+$ channels and a rapid influx of $\text{Na}^+$, making the membrane potential positive.

Repolarization

The phase of an action potential during which voltage-gated $\text{K}^+$ channels open to allow an outflow of $\text{K}^+$, restoring the internal membrane potential back toward resting levels.

Refractory period

The period following an action potential during which a neuron cannot be restimulated until the resting membrane potential is fully restored.

All-or-none rule

The principle stating that an action potential is triggered at full, fixed amplitude once threshold is met, encoding stimulus intensity by frequency rather than signal size.

Saltatory conduction

The rapid transmission of an action potential along a myelinated axon where the electrical current jumps from one node of Ranvier to the next.

Small-molecule neurotransmitters

Neurotransmitters synthesized directly within nerve terminals by specific enzymes, including amino acid derivatives and biogenic amines.

Neuropeptides

Neurotransmitter chains consisting of $3\text{ to }40$ amino acids that are synthesized in the neuronal cell body, packaged into vesicles, and transported down the axon.

Excitatory postsynaptic potential

A temporary localized depolarization of the postsynaptic membrane caused by the influx of $\text{Na}^+$ ions.

Inhibitory postsynaptic potential

A localized hyperpolarization of the postsynaptic membrane caused by the influx of $\text{Cl}^-$ or the outflow of $\text{K}^+$ ions.

Homeostasis

The automatic, coordinated response of physiological organs and systems to maintain a constant internal environment.

Homeotherms

Warm-blooded animals, such as mammals and birds, that maintain core body temperature within narrow physiological limits.

Thermoneutral zone

The ambient temperature range in which an endothermic animal maintains core body temperature without requiring extra metabolic energy expenditure.

Shivering thermogenesis

Involuntary, rhythmic ($15/\text{sec}$) simultaneous contractions of antagonistic skeletal muscles that convert $100\%$ of consumed energy into heat production.

Non-shivering thermogenesis

Heat production resulting from sympathetic secretion of catecholamines and thyroid hormones that elevates cellular metabolic rate, particularly in brown fat.

Radiation

The transfer of thermal energy via electromagnetic waves emitted or absorbed between an animal's body surface and the surrounding environment.

Conduction

The direct physical transfer of thermal energy between contacting surfaces, such as an animal lying on the ground.

Convection

The transfer of thermal energy between an animal's body surface and a moving fluid medium, such as air or water.

Panting

An active evaporative cooling process involving rapid, shallow respiratory ventilation observed in dogs and birds, but absent in horses and pigs.

Heat-loss center

The neuronal integration area located in the anterior hypothalamus that triggers physiological responses to decrease body temperature.

Heat-producing center

The neuronal integration area located in the posterior hypothalamus that initiates shivering, metabolic elevation, and vasoconstriction in response to cold.

Aldosterone (Thermoregulation)

A hormone whose secretion increases during prolonged heat exposure to enhance the reabsorption of $\text{Na}^+$ and $\text{Cl}^-$ from sweat glands.

Fever

A pathological elevation of body temperature induced by pyrogens resetting the hypothalamic set point to a higher baseline.

Hyperthermia

A pathological condition occurring when body heat production exceeds heat loss capacity beyond regulatory capabilities, leading to protein denaturation.

Hypothermia

A pathological condition occurring when heat loss exceeds heat production capabilities, leading to slowed neural activity and circulatory failure.

Normal body temperature (Dog)

Standard physiological core temperature range of $37.5\text{ to }39.0\,^\text{o}\text{C}$.

Normal body temperature (Horse)

Standard physiological core temperature range of $37.5\text{ to }38.5\,^\text{o}\text{C}$.

Normal body temperature (Broiler Chicken / Laying Hen)

Standard physiological core temperature range of $40.5\text{ to }42\,^\text{o}\text{C}$.

Cerebrum

The major brain division containing sensory areas for interpreting impulses, motor areas for muscle control, association areas, basal nuclei, and the limbic system.

Basal nuclei

Subcortical nuclei within the cerebrum that coordinate gross, automatic skeletal muscle movements and regulate muscle tone.

Limbic system

A functional brain network within the cerebrum involved in emotional aspects of behavior essential for survival.

Thalamus

A central brain structure that relays sensory input to the cerebral cortex, mediates crude perception of sensory stimuli, and contributes to movement control.

Hypothalamus

A vital brain region that integrates autonomic nervous system activities, controls body temperature, regulates eating, drinking, and circadian rhythms, and produces oxytocin and ADH.

Pineal gland

An endocrine structure in the brain that secretes melatonin to set the body's biological clock.

Cerebellum

A posterior brain structure that compares intended movements with actual execution to smooth and coordinate complex motor activities, posture, and balance.

Midbrain

A region of the brainstem that relays motor impulses from the cortex to the pons and sensory impulses from the spinal cord to the thalamus, containing visual and auditory reflex centers.

Superior colliculi

Midbrain structures that coordinate visual reflexes and eyeball movements in response to visual stimuli.

Inferior colliculi

Midbrain structures that coordinate auditory reflexes and movements of the head and trunk in response to sound stimuli.

Pons

A brainstem region that relays impulses across the cerebellum and contains the pneumotaxic and apneustic areas for respiratory control.

Medulla oblongata

The lower portion of the brainstem containing vital centers for heartbeat, blood vessel diameter, and respiration, as well as reflex centers for coughing, sneezing, vomiting, and swallowing.

Reticular formation

A diffuse brainstem network that maintains consciousness, initiates awakening from sleep, filters repetitive sensory input, and regulates muscle tone.

Spinal cord

A neural structure that conducts sensory nerve impulses toward the brain, transmits motor impulses toward peripheral effectors, and integrates spinal reflexes.