Human Physiology - The Nervous System and Neuronal Excitability

Flashcards covering key vocabulary terms from the lecture on the nervous system and neuronal excitability, including divisions, functions, cell types, electrical signals, and ion channels.

Central Nervous System (CNS)

Comprises the brain and spinal cord.

Peripheral Nervous System (PNS)

Comprises cranial nerves, spinal nerves, and sensory receptors in the skin.

Afferent Division (PNS)

The division of the PNS responsible for sensory input, including somatic and special senses.

Efferent Division (PNS)

The division of the PNS responsible for motor output, including the somatic nervous system and autonomic nervous system.

Somatic Nervous System

Part of the efferent division of the PNS that controls skeletal muscle.

Autonomic Nervous System

Part of the efferent division of the PNS that controls smooth muscle, cardiac muscle, and glands, divided into sympathetic and parasympathetic.

Enteric Nervous System

Part of the autonomic nervous system that controls smooth muscle and glands of the GI tract.

Sensory Function (Nervous System)

Sensory receptors detect external or internal stimuli and relay sensory information to the brain and spinal cord for integration.

Integration Function (Nervous System)

The CNS analyzes sensory information and makes decisions for appropriate responses.

Motor Function (Nervous System)

Motor information is conveyed from the CNS through cranial and spinal nerves of the PNS to appropriate effectors (muscles and glands).

Neurons

Cells of the nervous system that possess dendrites, a cell body, and an axon, responsible for electrical signaling.

Neuroglia

Support cells of the nervous system, including astrocytes, oligodendrocytes, microglia, and ependymal cells in the CNS, and Schwann cells in the PNS.

Astrocytes

Most numerous neuroglia in the CNS, maintaining the blood-brain barrier, extracellular chemical environment, guiding neuron development, and playing a role in synapse formation.

Oligodendrocytes

Neuroglia in the CNS that form and maintain the myelin sheath.

Microglia

Phagocytic neuroglia in the CNS that remove debris, damaged cells, and pathogens.

Ependymal Cells

Neuroglia in the CNS that produce and assist in the circulation of cerebrospinal fluid (CSF).

Schwann Cell

Neuroglia in the PNS that form and maintain the myelin sheath and participate in PNS axon regeneration.

Myelin Sheath

An electrical insulation around axons that increases the speed of conduction of action potentials, formed by Schwann cells in the PNS and oligodendrocytes in the CNS.

Nodes of Ranvier

Gaps in the myelin sheath along an axon.

White Matter

Areas of the nervous system composed primarily of myelinated axons.

Plasticity (Neurons)

The ability of neurons to change throughout life, based on experience, including making new connections, increasing dendrites, or changing receptor numbers.

CNS Repair

Little to no neuron regeneration occurs in the CNS due to inhibitory proteins from neuroglia, absence of growth-stimulating cues, and scar tissue formation, leading to permanent damage.

PNS Repair

Regeneration of damaged neurons in the PNS can occur if the cell body is intact and Schwann cells remain active, forming a regeneration tube to guide and stimulate axon regrowth.

Excitable Cells

Cells that can produce electrical signals, such as neurons and muscle cells.

Electrical Signal

A change in the membrane potential of an excitable cell, referring to action potentials and graded potentials.

Action Potential

One of two types of electrical signals in excitable cells, involving a rapid, transient change in membrane potential.

Graded Potential

One of two types of electrical signals in excitable cells, which are localized changes in membrane potential that vary in magnitude.

Potential Difference

The separation of charge across a membrane, with its magnitude measured in millivolts.

Equilibrium Potential (Ex)

The value of the membrane potential when the electrical force exactly opposes the concentration force for a single ion, resulting in no net change in the number of ions across the membrane.

K+ Equilibrium Potential

The membrane potential value (approximately -90 mV) reached when the membrane is permeable only to potassium, and the electrical and chemical gradients for K+ are equal and opposite.

Na+ Equilibrium Potential

The membrane potential value (approximately +60 mV) reached when the membrane is permeable only to sodium, and the electrical and chemical gradients for Na+ are equal and opposite, representing a steady state.

Nernst Equation

A formula used to calculate the equilibrium potential for a specific ion.

Resting Membrane Potential (RMP)

The voltage that exists across the plasma membrane of an unstimulated cell, typically around -70mV in neurons, determined by unequal ion distribution, differences in membrane permeability, and the Na+/K+ pump.

Na+/K+ Pump (Na+/K+ ATPase)

An active transport mechanism that maintains the concentration gradients of K+ and Na+ across the membrane by transporting 3 Na+ out and 2 K+ in, contributing approximately 3mV to the membrane potential.

Goldman-Hodgkin-Katz Equation

An equation used to calculate the membrane potential by taking into account ion permeabilities.

Ion Channels

Specific protein channels in the plasma membrane that allow ions to flow, causing changes in membrane potential and enabling electrical communication.

Leak Channels (Non-gated Channels)

Ion channels that have gates that randomly alternate between open and closed positions, contributing to resting membrane potential.

Ligand-gated Channel (Chemically-gated Channel)

An ion channel that opens or closes in response to the binding of a specific ligand (chemical stimulus).

Mechanically-gated Channel

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

Voltage-gated Channel

An ion channel that opens in response to a change in the membrane potential (voltage).

Ohm's Law (Membrane Potential)

Describes the relationship between current (I), voltage (V), and resistance (R) in the context of membrane potential, where I = V/R.

Current (I)

The flow of charged particles across a membrane.

Voltage (V)

The electrical potential difference across a membrane.

Resistance (R)

The hindrance to the flow of charges across a membrane.