Human Anatomy & Physiology - Homeostasis and Neurotransmission Vocabulary

Vocabulary flashcards covering Introduction to Anatomy & Physiology, Tissue Types, Homeostasis Feedback Loops, Electrical Signals, and Neurotransmission.

Anatomy

The study of body structure, derived from literal roots meaning "to take apart".

Levels of body organization

Molecular, cellular, tissue, organ, system, organism

What are the four types of tissue?

Epithelial, muscle, nervous and connective

Physiology

The study of natural phenomena and body function, operating on the foundational principle that "form follows function".

Epithelial Tissue

classified by the number of cell layers and their shape, is avascular

Skeletal Muscle Tissue

Voluntary muscle tissue attached to the musculoskeletal system consisting of long, tubular, striated cells with multinucleation ($5\text{ to }5000$ nuclei) and a very large cell diameter ($100\,\mu m$).

What are the 3 types of muscle?

Smooth, cardiac and skeletal

Cardiac Muscle Tissue

Involuntary, striated, large, has gap junctions, involuntary

Smooth Muscle Tissue

Involuntary, non-striated muscle tissue found in hollow organs, consisting of small ($8\,\mu m$), spindle-shaped cells with a single nucleus and gap junctions.

Homeostasis

A self-regulating process by which biological systems maintain stability within a narrow internal range compatible with life while adjusting to changing conditions.

What are the two systems that are key for maintaining homeostasis?

Nervous and endocrine

What is an external perturbation

Usually environmental like Extremes in temperature or oxygen changes

How does the nervous system maintain homeostasis?

Communicates with the target organs using electrical impulses to evoke rapid changes that restore balance

How does the endocrine system maintain homeostasis?

Communicates with target organs using blood borne hormones to affect changes that restore balances, usually slowly

What are internal perturbations?

Internal changes like blood sugar or waste products

Classes of connective tissues

1. Connective tissue proper

2. Cartilage

3. Bone

4. Blood and lymph

Types of loose connective tissues

Areolar, reticular and adipose

Types of dense connective tissues

Regular, irregular and elastic

Feedback System

A cycle of events in which the status of a body variable is continually monitored, evaluated, changed, re-monitored, and re-evaluated.

What is a variable in feedback systems?

A controlled condition like body temp or RBG

What is a change in a feedback variable called?

A stimulus

Detector (Receptor)

A component of a feedback loop that monitors and detects changes in a controlled variable.

Control Center

A component of a feedback loop that evaluates input from a detector and initiates an appropriate output response.

Effector

A body structure that receives signals from the control center and produces a response or effect that alters the controlled variable.

Negative Feedback Loop

A homeostatic control mechanism in which the body's response decreases or reverses the departure of a variable from its set point.

Positive Feedback Loop

A control mechanism that strengthens or reinforces a change in a controlled variable until interrupted or terminated by an outside event.

Positive feedback loop examples?

Thrombus formation, action potential in neurons, Ovulation, labour/delivery, lactation

Sign

An objective, measurable indicator of a disease or homeostatic departure, such as elevated blood pressure or elevated blood glucose.

Symptom

A subjective measure of body change reported by a patient, such as fatigue, nausea, or thirst.

Cell Body (Soma)

The central region of a neuron (also known as the perikaryon) that contains the nucleus and essential cellular organelles.

What do dendrites do?

Receive input

What does an axon do?

Conducts nervous impulses

What does the myelin sheath do? What are they made of?

Helps increase speed of conduction of impulses, Schwann cells

What do synaptic end bulbs do?

Site of release of neurotransmitter

Axon Hillock

The cone-shaped region of a neuron connecting the soma to the axon where action potentials (nervous impulses) are generated at the trigger zone.

What conditions facilitate production of electrical signals?

Resting membrane potential and ion channels

For ions to move across the plasma membrane to produce electrical signals, what is the problem and solution?

Problem: lipid bilayer plasma membrane is an insulator and tough to get through

Solution: ion channels are transmembrane proteins that contain a pore that allows the irons to move down their electrochemical gradient

The electrochemical gradient has which two gradients?

Electrical (charge) gradient and the chemical (concentration) gradient

What does the electrical charge gradient do?

Positively charged ions (cations) move towards negatively charged areas, while anions move to positive ones

What does the chemical gradient do?

Ions move from an area of high concentration to low

Resting Membrane Potential (RMP)

The electrical voltage across the plasma membrane of a resting neuron, averaging $-70\,mV$, generated by unequal ion distribution, differential membrane permeability, and electrogenic $Na^+/K^+$ ATPases.

Na+/K+ ATPase

An electrogenic transmembrane pump that uses $1\,ATP$ to transport $3\,Na^+$ ions out of the cell and $2\,K^+$ ions into the cell, maintaining ionic concentration gradients.

Leak Channel

An ion channel that randomly opens and closes, providing greater permeability to $K^+$ than $Na^+$ in resting neuronal membranes.

Ligand-Gated Channel

An ion channel that opens or closes in response to a specific chemical stimulus, such as a neurotransmitter binding to its receptor site.

Mechanically-Gated Channel

An ion channel that opens or closes in response to mechanical stimuli, such as touch, pressure, tissue stretching, or vibration.

Voltage-Gated Channel

An ion channel that opens or closes in response to direct changes in the membrane potential (voltage).

Graded Potential

A localized, short-distance electrical deviation in membrane potential that varies in amplitude depending on stimulus strength and experiences decremental conduction.

Summation

The process by which individual graded potentials combine spatially (occurring close together in space) or temporally (occurring close together in time) to produce a larger net change in membrane potential.

Action Potential

A rapid, long-distance electrical signal propagated along an excitable membrane operating on an all-or-none principle via positive feedback activation of voltage-gated $Na^+$ channels.

Absolute Refractory Period

The period during an action potential when even a very strong second stimulus cannot initiate another action potential because voltage-gated $Na^+$ channels are inactivated.

Relative Refractory Period

The period following an action potential during which a second action potential can be triggered, but only by a larger-than-normal stimulus, because voltage-gated $K^+$ channels remain open while $Na^+$ channels have reset.

Continuous Conduction

The step-by-step depolarization and repolarization of adjacent segments along unmyelinated axons and muscle fibers.

Saltatory Conduction

The rapid mode of impulse propagation along myelinated axons in which the action potential leaps from one myelin sheath gap (node of Ranvier) to the next.

Synapse

A specialized region where electrical or chemical communication occurs between a presynaptic neuron and a postsynaptic neuron or effector cell.

Excitatory Postsynaptic Potential (EPSP)

A depolarizing postsynaptic graded potential that brings the membrane potential closer to threshold, often caused by the opening of $Na^+$ channels.

Inhibitory Postsynaptic Potential (IPSP)

A hyperpolarizing postsynaptic graded potential that moves the membrane potential further from threshold, often caused by the opening of $K^+$ or $Cl^-$ channels.

Ionotropic Receptor

A neurotransmitter receptor that functions directly as a ligand-gated ion channel, opening immediately upon neurotransmitter binding.

Metabotropic Receptor

A neurotransmitter receptor coupled to a G-protein that indirectly opens or closes associated ion channels through second messenger pathways.

Acetylcholine (ACh)

A small-molecule neurotransmitter released by somatic and autonomic PNS motor neurons and certain CNS neurons involved in memory and cognition.

Biogenic Amines

A class of small-molecule neurotransmitters containing an amino functional group ($\text{R-NH}_2$), including catecholamines (epinephrine, norepinephrine, dopamine), indolamines (serotonin), and histamine.

Substance P

A neuropeptide neurotransmitter consisting of amino acid chains that transmits pain signals in the nervous system.

Enkephalins and Endorphins

Endogenous neuropeptides that act as natural analgesics by inhibiting the release of Substance P.

Nitric Oxide (NO)

A gas and lipid-soluble small-molecule neurotransmitter synthesized in the brain and body tissues that functions in learning, memory, vasodilation, and blood clotting inhibition.