The Nervous System

Vocabulary flashcards covering key terms from lecture notes on the structure, function, and organization of the nervous system.

Neuron

Fundamental unit of the nervous system that transmits information via electrical and chemical signals; also called a nerve cell.

Electrical impulse

A wave of electrical activity that travels along a neuron to convey information and trigger responses.

Central Nervous System (CNS)

The brain and spinal cord; responsible for processing, integration, and coordination of sensory input and motor output.

Peripheral Nervous System (PNS)

All nerves outside the brain and spinal cord; carries signals between the CNS and the rest of the body.

Dendrite

Branched extension of a neuron that receives incoming signals and directs them toward the cell body.

Excitatory signal

Input that makes a neuron more likely to generate an action potential (fire).

Inhibitory signal

Input that makes a neuron less likely to generate an action potential.

Cell body (Soma)

Central part of a neuron containing the nucleus; metabolic and nutrient center of the cell.

Axon

Long, thin projection that conducts action potentials away from the cell body to other neurons, muscles, or glands.

Myelin sheath

Fatty insulating layer around many axons; speeds and increases efficiency of impulse transmission and prevents signal loss.

Schwann cell

Glial cell that forms myelin around axons in the peripheral nervous system.

Oligodendrocyte

Glial cell that forms myelin around axons in the central nervous system.

Node of Ranvier

Periodic gap in the myelin sheath rich in voltage-gated sodium channels; enables rapid impulse “jumping.”

Saltatory conduction

Process by which action potentials leap from one Node of Ranvier to the next, greatly increasing conduction speed.

Axon terminal

Specialized ending of an axon that releases neurotransmitters to communicate with another cell.

Synapse

Junction where a neuron communicates with another cell across a small gap called the synaptic cleft.

Synaptic cleft

Microscopic gap between the presynaptic and postsynaptic membranes across which neurotransmitters diffuse.

Nerve

Bundle of neuron fibers (primarily axons) wrapped in connective tissue within the PNS.

Nerve fibre

Another term for an individual axon, especially when myelinated.

Somatic nervous system

Division of the PNS that controls voluntary movements of skeletal muscles.

Autonomic nervous system

Division of the PNS that regulates involuntary functions such as heart rate and digestion.

Sympathetic division

Branch of the autonomic nervous system that prepares the body for ‘fight or flight’ responses.

Parasympathetic division

Branch of the autonomic nervous system that promotes ‘rest and digest’ activities.

Sensory neuron (Afferent)

Neuron that carries information from sensory receptors toward the CNS.

Interneuron

Neuron within the CNS that connects sensory neurons to motor neurons and processes information.

Motor neuron (Efferent)

Neuron that transmits commands from the CNS to muscles or glands (effectors).

Stimulus

Any internal or external change that can be detected by receptors and elicit a response.

Receptor

Specialized cell or structure that detects a stimulus and initiates neural signaling.

Control centre (Integration centre)

Part of the CNS that interprets sensory input and determines the appropriate response.

Effector

Muscle or gland that carries out the response commanded by the nervous system.

Reflex arc

Simple neural pathway of a reflex involving a sensory neuron, an interneuron (often), and a motor neuron.

Reflex action

Rapid, involuntary response to a stimulus that occurs before conscious brain processing.

Action potential

All-or-none electrical signal that travels along an axon to convey information.

Voltage-gated sodium channel

Ion channel that opens in response to membrane depolarization, essential for initiating and propagating action potentials.

label 1

dendrite

label 2

cell body

label 3

nucleus

label 4

axon

label 5

node of ranvier

label 6

axon terminal

label 7

myelin sheath

label 8

schwann cell

cerebrum function

responsible for higher-level functions (i.e. thinking, memory + voluntary movement

cerebellum function

coordinates movement, balance + maintains posture

brainstem function

controls essential + automatic functions (i.e. breathing, heart rate) connects cerebrum + cerebellum to spinal cord

brain death

when a person no longer has any brain functions

frontal lobe

largest lobe of the brain - controls voluntary movement, thinking, emotions + memory

parietal lobe

processes sensory information, such as taste, touch + temperature

occipital lobe

related to visual stimuli - depth perception, colours + facial recognition

temporal lobe

forming visual + long-term memories, recognising speech, + automatic responses

right brain function

creativity, imagination, intuition, left-hand controls

left brain function

logic, language, reasoning, number skills, right-hand control

functions of the brain

sensory perception, motor control, cognitive functions, emotional regulation, homeostasis

anterior cerebral artery location

tissue behind the forehead and under the crown

middle cerebral artery location

further inside the brain

posterior cerebral artery location

back of head, lower part of brain + cerebellum

neuroplasticity

the nervous systems ability to change its activity in response to stimuli, reorganising structure, function, or connections after brain injury

MRI process

strong magnetic fields observe different types of body tissue, blood flow shows areas of brain working hardest

MRI function

can diagnose brain tumours + areas of damage

skull function

supporting brain + facial structures

cranium

passage through birth canal + growth of the brain

most common skull issue

fracture - break in bone

meninges layers

dura matter, arachnoid matter, pia matter

dura matter function

thick outer layer - connective tissue attaches to skull and arachnoid matter - allows blood to leave the brain and cerebrospinal fluid to enter

arachnoid matter function

middle layer - no blood vessels or nerves - web-like appearance of connective tissue projections

pia matter

innermost layer - tight against brain + spinal cord - supplies blood to brain tissue, contains cerebrospinal fluid

epidural space location + purpose

between skull + dura matter - pain medications + anaesthesia are injected here

subdural space location + purpose

between dura matter + arachnoid matter - can be opened to treat trauma to the brain

subarachnoid space location + purpose

between arachnoid matter + pia matter - filled with cerebrospinal fluid to protect brain + spinal cord

meningitis

infection of the meninges, caused by bacteria, fungus or virus - diagnosed by lumar puncture - fever, headache, rash

subdural hematoma

bleeding between dura matter and arachnoid matter due to tear in blood vessel

bleeding within meningeal layers

bleeding in blood vessels in meninges - caused by head trauma, creating swelling in the brain

cerebrospinal fluid (CSF)

clear colourless fluid surrounding brain + spinal cord - provides nutrients, cushioning for impact

ventricles

connected, fluid filled cavities that produce + circulate CSF

CSF fluid leaks

loss of CSF, dropping fluid pressure

hydrocephalus

build up of CSF → headaches, vision problems, cognitive changes

idiopathic intracranial hypertension (IIH)

increased pressure within skull → headaches + vision problems

blood-brain barrier

semi-permeable membrane - prevents harmful substances from entering the brain - maintaining a stable environment in the brain

what molecules CAN pass through the blood-brain barrier

small, lipid-soluble molecules, some gases + nutrient

what molecules CANNOT pass through the blood-brain barrier

larger molecules, proteins + drugs

blood-brain barrier conditions

inflammation/weakening (chronic or acute) - allows harmful substances in - brain cancer, infection, concussion, MS, parkinsons

nervous tissue

made up of neurons + neuroglial cells -

neuroglial cells (glial cells or glia)

do not produce electrical impulses, provide support + critical functions for neurons

neuroglial cell function

regulates neurotransmission, brain homeostasis, making myelin, forming blood-brain barrier

neuroglial cell types

astrocytes, oligodendrocytes, microglia, schwann cells

astrocytes location

found in the CNS in both grey and white matter

astrocytes structure

star-shaped glial cells with many branches

astrocytes function

provide nutrients to neurons, maintaining extracellular environment + provide structural support

oligodendrocytes location

CNS in both grey and white matter - more abundant in white matter

oligodendrocytes structure

round + dense nucleus, surrounded by cytoplasm - processes extend and wrap around axons

oligodendrocytes function

axon myelination, providing a stable environment for neurons + tissue repair

microglia location

CNS - most abundant in brain stem, hippocampus + bansal ganglia

microglia structure

small cell body with branching cell processes - activated when they become larger - very mobile

microglia function

macrophage - white blood cells digest pathogens - triggering inflammatory responses to protect the brain

schwann cells location

main glial cells of the peripheral nervous system

schwann cells structure

shaped like a rolled up sheet of paper, layers of myelin between each roll

schwann cells function

myelination and non-myelinating - a number of schwann cells are needed to myelinate an axon

grey matter development

not fully developed until mid 20s - begins forming in utero

grey matter function

prefrontal cortex is responsible for planning, decision making, and impulse control - the last part of the brain to develop

grey matter decline

metabolic disorders, trauma, neurogenerative disease