Hormone and Nervous Systems Review

Flashcards covering the endocrine system coordination, nervous system structure, action potential mechanics, sensory receptor types and transduction, and the molecular mechanism of muscle contraction.

Negative feedback (Hormonally)

A control mechanism, such as thyroid hormone blocking TRH and TSH release, that prevents the overproduction of a hormone by inhibiting its own stimulation pathway.

Hormones

Control substances formed in specialized tissues or organs that exert extremely specific influences on other tissues, moving through the blood to reach cells with specific receptors.

Synaptic signaling

A type of communication where an electrical signal (impulse) triggers the release of neurotransmitters by a sending cell, which then diffuse to and are captured by a target cell.

Central Nervous System (CNS)

Part of the nervous system consisting mainly of the brain and spinal cord, specifically where the cell bodies of neurones are located.

Peripheral Nervous System (PNS)

The division of the nervous system consisting of the extensions of all neurons, specifically the axons and dendrites.

Axon

A part of the neuron that conducts impulses away from the cell body.

Dendrite

A part of the neuron that conducts impulses toward the cell body or receives signals from sensors.

Resting potential

The negative charge of approximately $-70\,mV$ in a neuron at rest, maintained by the $Na^+/K^+$ pump and the leakage of more $K^+$ out than $Na^+$ in.

Threshold (Drempelwaarde)

The specific level of depolarization required to trigger an action potential.

Hyperpolarization

A change in the membrane potential that makes it more negative, often caused by stimuli increasing the permeability of the cell membrane for $K^+$.

Depolarization

A change in the membrane potential toward a more positive value, which can lead to an action potential if the threshold is reached.

Action potential

A rapid change in membrane potential reaching exactly $+35\,mV$ once the threshold is met, involving the opening of voltage-gated $Na^+$ channels followed by $K^+$ channels.

Saltatory conduction

The jumping of action potentials from one node of Ranvier to the next along a myelinated axon, which increases the speed of transmission.

Transduction (Sensory)

The process by which sensory receptors convert a stimulus into a receptor potential.

Amplification

The strengthening of a weak stimulus during signal processing, which can make a signal up to $100,000$ times stronger.

Sensory adaptation

A decrease in sensitivity following repeated or continuous stimulation of a sense organ.

Nociceptors

Pain receptors that detect extreme pressure or temperature capable of damaging tissue.

Organ of Corti

The structure in the ear containing hair cells (mechanoreceptors) that bend in response to vibrations in the cochlea to create receptor potentials.

Rhodopsin

A light-sensitive pigment in the rods of the retina consisting of retinal, which changes from a cis-form to a trans-form when it absorbs light.

Skeletal muscle

Striated muscle tissue controlled by the somatic nervous system.

Sarcomere

The functional unit of skeletal muscle tissue where contraction occurs on a microscopic level.

Sliding filament model

A model of muscle contraction involving the interaction and movement of actin and myosin filaments.

Troponin complex

A regulatory protein complex in skeletal muscle to which $Ca^{2+}$ binds, causing tropomyosin to move and expose myosin-binding sites on actin.

Sarcoplasmic reticulum (SR)

A specialized endoplasmic reticulum in muscle cells that stores and releases $Ca^{2+}$ ions to trigger contraction.

Rigor mortis

A state of chronic muscle contraction after death caused by the complete depletion of $ATP$, which is required for myosin to release from actin and to pump $Ca^{2+}$ out of the cytosol.