Chapter 11/12 Control and Integration

Flashcards covering the control and integration mechanisms of the nervous and endocrine systems, including nerve impulse conduction, synaptic activity, and hormonal regulation.

Regulate

To adjust the amount, concentration, or rate of a physiological process to maintain a desired level.

Integration

The control of all physiological systems so that they merge into a smoothly operating organism; no single process occurs independent of others.

Neurons

The nerve cells that make up the nervous system of all animals, composed of a cell body, an axon, and dendrites.

Resting potential

The potential difference between the inside and outside of an inactive neuron's cell membrane, resulting from concentration differences of $Na$ and $K$ ions.

Equilibrium potential for $K$ ($EK^+$)

The state reached when for every $K$ ion that exits the cell, one moves back in, equal to $-75\,mV$.

Normal resting potential

The potential of an inactive neuron, which is approximately $-70\,mV$, slightly more positive than $EK^+$ due to $Na$ permeability being slightly more than 0.

Depolarization

A change in membrane permeability that allows $Na$ ions to flow inward, making the inside of the axon positive.

Hyperpolarization

An increase in the membrane permeability of $K$, causing more $K$ to flow outward and making the membrane potential more negative.

Repolarization

The process of re-establishing membrane permeability and returning $Na$ or $K$ concentrations to normal levels, bringing the membrane back to resting potential.

Na/K ATPase pump

A gated ion channel that uses energy from the hydrolysis of ATP to pump $3\,Na$ out and $2\,K$ into the axon.

Ligand-gated-channels

Ion channels that respond to outside agents.

Voltage-gated-channels

Self-closing ion channels that respond to electrical currents.

Action potentials (AP)

Electrical signals that occur in the axon, maintain a constant amplitude of $100\,mV$, and are initiated by voltage-gated channels.

Post-synaptic potentials (PSP)

Electrical signals that occur in the dendrites and cell body, vary in amplitude depending on the number of open ion channels, and are initiated by ligand-gated channels.

Myelin sheath

A covering formed by glial cells that wrap around the axon to increase conduction velocity in vertebrates.

Nodes

The gaps between glial cells on a myelinated axon where the only delays in conduction occur.

Electrical synapse

A type of synapse where gap junctions form low-resistance pathways for electrical continuity, allowing current to flow without measurable delay.

Chemical synapse

The most common type of synapse where an axon terminal button (knob) is separated from the target cell by a synaptic cleft.

Synaptic cleft

The narrow space that remains between the axon and the target cell in a chemical synapse.

Excitatory post synaptic potential (EPSP)

A wave of depolarization that spreads through the cytosol, created when $Na$ enters the target cell through ligand-linked channels.

Inhibitory post synaptic potential (IPSP)

A hyperpolarizing wave created in the target cell when channels for $K$ or $Cl$ are opened.

Threshold potential

The specific potential level an EPSP must reach to trigger the opening of voltage-gated channels in the axon.

Rising phase

The first part of an action potential resulting from the opening of voltage-gated $Na$ channels.

Falling phase

The second part of an action potential resulting from the opening of voltage-gated $K$ channels.

Hyperpolarization phase

The final part of an action potential where $K$ channels remain open, eventually returning the potential to $-70\,mV$ as they close.

Steroids

Hormones derived from cholesterol, such as estrogen, cortisone, and aldosterone.

Tyrosine-Derived hormones

Hormones synthesized from tyrosine, specifically the thyroid hormones noradrenalin and adrenalin.

Hypothalamus

The control center for the endocrine system and seat of nervous control for temperature, food, and water intake regulation.

Hypophysis

The 'master gland' of the endocrine system, regulated by the hypothalamus via neural connections or portal circulation.

Neurohypophysis

A part of the hypophysis that serves as a storage and release organ for hormones produced in the brain, particularly those regulating water reabsorption.

Adenohypophysis

A part of the hypophysis that produces hormones, with release regulated by hypothalamic hormones delivered through the portal circulation.

Adrenal cortex

The outer part of the adrenal gland, essential for life, which produces hormones affecting the metabolism of carbohydrates, proteins, fats, and electrolytes.

Adrenal medulla

The inner part of the adrenal gland of neural origin that secretes noradrenaline and adrenaline to trigger the fight-or-flight response.

Thyroid gland

A gland that takes up iodine to produce hormones that stimulate oxidative metabolism and determine metabolic rate.

Pineal gland

A small tissue between the cerebral hemispheres that fluctuates with light and dark cycles to maintain circadian rhythms.