Leaving Certificate Biology: The Nervous System

Vocabulary practice flashcards covering Chapter 23 of Leaving Certificate Biology, including human response systems, neuron anatomy, impulse transmission, synaptic mechanisms, brain regions, spinal cord anatomy, and reflex arcs.

Response system

A biological system that detects a stimulus and coordinates an appropriate action (in humans, the endocrine system and the nervous system).

Stimulus

A change in an organism's internal or external environment that can be detected so an appropriate response can be coordinated.

Receptor cells

Specialised cells present in a sense organ that can detect a stimulus and generate electrical impulses.

Effector

A tissue (specifically a muscle or a gland) that carries out an appropriate response when it receives an electrical impulse from the nervous system.

Central nervous system (CNS)

The component of the nervous system consisting of the brain and spinal cord; it receives impulses from sense organs, processes information, and sends impulses to effectors.

Peripheral nervous system (PNS)

The component of the nervous system consisting of nerve fibres and cell bodies found outside the central nervous system; it carries impulses to and from the CNS.

Neuron

A nerve cell that serves as the basic functional unit of the nervous system and transmits electrical impulses throughout the body.

Sensory neuron

A neuron that carries impulses from sense organs to the central nervous system, characterized by a cell body situated along the length of the neuron.

Motor neuron

A neuron that carries impulses from the central nervous system to an effector, with its cell body situated at the beginning of the neuron.

Interneuron

A neuron located strictly within the central nervous system that carries impulses between sensory neurons and motor neurons and does not possess Schwann cells.

Dendrites

Neuronal projections that carry electrical nerve impulses towards the cell body.

Cell body (neuron)

The part of a neuron that receives impulses from dendrites, passes them to the axon, synthesises neurotransmitters, and contains many mitochondria to generate energy for impulse transmission.

Axon

The long, slender projection of a neuron that carries electrical impulses away from the cell body.

Schwann cell

A specialised cell wrapped along the axon of certain neurons that produces and secretes the myelin sheath.

Myelin sheath

A fat-rich membrane that insulates the neuron, significantly speeding up the transmission of electrical nerve impulses.

Axon terminal

A branching end of an axon that transmits electrical nerve impulses to the neurotransmitter swellings.

Neurotransmitter swelling

A bulbous structure at the tip of an axon terminal that releases neurotransmitters to convey impulses across a synapse to another neuron.

Threshold stimulus

The minimum stimulus intensity required for an electrical impulse to be generated and conducted along a neuron.

Synapse

The junction where two neurons come into close proximity without physically touching.

Synaptic cleft

The microscopic physical gap between two neurons at a synapse across which chemical neurotransmitters diffuse.

Neurotransmitters

Chemicals synthesised in the cell bodies and stored in vesicles that carry a nerve impulse across the synaptic cleft from one neuron to another.

Reuptake

The process in which neurotransmitters are inactivated by enzymes and reabsorbed from the synaptic cleft back into the neurotransmitter swellings to be recycled.

Acetylcholine

A neurotransmitter that plays a crucial role in muscle functioning, memory, and learning, whose deficiency in the brain is associated with Alzheimer's disease.

Endorphins

Neurotransmitters released during exercise, pleasurable activities, stress, or injury to block pain and reduce anxiety.

Dopamine

A neurotransmitter involved in pleasure, reward, motivation, memory, mood, sleep, and learning.

Cerebrum

The forebrain structure divided into right and left hemispheres that controls voluntary movements, senses, memory, learning, and emotions.

Cerebellum

The hindbrain structure responsible for muscular coordination and maintaining balance.

Thalamus

The brain region located below the cerebrum that acts as a sorting centre, redirecting incoming sensory impulses to the appropriate area of the brain.

Hypothalamus

A structure located below the thalamus that monitors body temperature, appetite, thirst, and water and salt balance to maintain homeostasis.

Medulla oblongata

The part of the brainstem connecting the brain to the spinal cord that controls involuntary actions such as breathing, swallowing, vomiting, and sneezing.

Pituitary gland

The body's master endocrine gland situated hanging from the base of the brain, below and attached to the hypothalamus, which secretes various hormones.

Meninges

Three protective membranes surrounding the brain and spinal cord that contain cerebrospinal fluid to act as a shock absorber.

Meningitis

A disease characterised by inflammation of the protective meninges membranes surrounding the brain and spinal cord.

Central canal

A central cavity within the grey matter of the spinal cord that contains cerebrospinal fluid to absorb shocks and provide protection.

White matter

Nervous tissue in the central nervous system composed primarily of axons covered in myelin sheath, whose fat content gives it a white appearance.

Grey matter

Nervous tissue in the central nervous system composed primarily of neuron cell bodies lacking myelin sheaths, giving it a grey appearance.

Dorsal root

A nerve tract entering the posterior side of the spinal cord that carries sensory neurons inward.

Dorsal root ganglion

A swelling on the dorsal root located outside the CNS where the cell bodies of sensory neurons are grouped together.

Ventral root

A nerve tract emerging from the anterior side of the spinal cord that carries motor neurons outward to effectors.

Reflex action

An involuntary, automatic reaction to a stimulus that protects the body from damage by executing a response more rapidly than normal.

Reflex arc

The neural pathway followed by an electrical nerve impulse during a reflex action (from receptor through sensory neuron, interneuron, and motor neuron to effector).

Opioids

Painkilling drugs (such as codeine, morphine, and fentanyl) that bind to receptors on post-synaptic neurons in the brain to inhibit pain signal transmission and stimulate the release of dopamine.