Overview of the Nervous System and Sensory Reception

Neuron

Basic unit conducting nerve impulses in the body.

Myelin Sheath

Fatty layer insulating axons, speeding impulse transmission.

Action Potential

Electrical signal traveling along a neuron.

All-or-None Response

Signal intensity remains constant once triggered.

Synapse

Junction where neurons communicate via neurotransmitters.

Neurotransmitters

Chemicals transmitting signals across synapses.

Central Nervous System (CNS)

Includes brain and spinal cord, processes information.

Peripheral Nervous System (PNS)

Nerves outside CNS, connects to organs and muscles.

Autonomic Nerves

Involuntary nerves controlling internal organs.

Somatic Nerves

Voluntary nerves controlling skeletal muscles.

Parasympathetic Nerves

Nerves that promote relaxation and recovery.

Sympathetic Nerves

Nerves preparing body for fight or flight.

Glial Cells

Supportive cells, do not conduct impulses.

Dendrites

Branches receiving impulses towards neuron cell body.

Axons

Long branches transmitting impulses away from cell body.

Schwann Cells

Glial cells producing myelin around axons.

Nodes of Ranvier

Gaps in myelin sheath for faster impulse transmission.

Neurilemma

Outer membrane aiding axon regeneration after damage.

Multiple Sclerosis (MS)

Disorder causing myelin damage, affecting nerve transmission.

Symptoms of MS

Numbness, tingling, muscle spasms, coordination loss.

Homeostasis

Maintenance of stable internal environment in the body.

Electrochemical Messages

Signals transmitted by nervous system for communication.

Sensory Neurons

Transmit sensory information to the brain and spinal cord.

Interneurons

Process sensory information and relay to motor neurons.

Motor Neurons

Carry signals from the brain to effectors.

Reflex Arc

Pathway for reflex actions without brain involvement.

Nerve Impulse

Electrochemical signal transmitted along neurons.

Resting Membrane Potential

Charge difference across a resting neuron's membrane.

Resting State

Neuron's state before action potential initiation.

Sodium-Potassium Pump

Maintains ion balance by exchanging Na+ and K+.

Depolarization

Membrane potential shifts from -70 mV to +40 mV.

Threshold Potential

Minimum -55 mV required to trigger action potential.

All-or-None Principle

Neuron fires fully or not at all.

Repolarization

Restoration of resting potential after action potential.

Refractory Period

Time during which neuron cannot fire again.

Action Potential

Rapid change in membrane potential during nerve impulse.

K+ Ion Channels

Allow potassium to exit during repolarization phase.

Na+ Ion Channels

Open to allow sodium influx during depolarization.

Electrochemical Impulse

Combination of electrical and chemical signaling in neurons.

Concentration Gradient

Difference in ion concentration across a membrane.

Impulse Frequency

Rate of nerve impulses indicates stimulus intensity.

Neural Circuit

Network of neurons transmitting signals in reflex actions.

Positive Charge Accumulation

Occurs outside neuron during resting state.

Negative Charge Inside Neuron

Resting state characterized by negative internal charge.

Wavelike Motion

Propagation of action potential along the axon.

Axon Terminal

End of the axon where neurotransmitter release occurs.

Synapse

Space between axon terminal and dendrites of another neuron.

Neurotransmitters

Chemicals that transmit signals between neurons.

Action Potential

Electrical impulse traveling down the axon.

Calcium Channels

Gateways that open to allow calcium ions in.

Presynaptic Membrane

Membrane of the neuron releasing neurotransmitters.

Vesicles

Small sacs containing neurotransmitters in axon terminals.

Synaptic Cleft

Gap neurotransmitters cross to reach the post-synaptic membrane.

Post-Synaptic Membrane

Membrane of the neuron receiving neurotransmitters.

Receptors

Proteins that bind neurotransmitters on the post-synaptic membrane.

Cholinesterase

Enzyme that breaks down acetylcholine in the synapse.

Excitatory Neurotransmitters

Increase likelihood of action potential in post-synaptic neuron.

Inhibitory Neurotransmitters

Decrease likelihood of action potential in post-synaptic neuron.

Depolarization

Reduction in membrane potential, making neuron more positive.

Hyperpolarization

Increase in membrane potential, making neuron more negative.

Summation

Combined effect of multiple neurotransmitter signals leading to action potential.

Serotonin

Regulates mood and sleep; linked to depression.

Dopamine

Influences movement and pleasure; low levels cause Parkinson's.

Acetylcholine

Excites muscle contractions; low levels linked to Alzheimer's.

Stimulants

Drugs that mimic neurotransmitters and enhance receptor activity.

Depressants

Drugs that block neurotransmitter receptors and reduce activity.

GABA

Inhibitory neurotransmitter linked to epilepsy and Huntington's disease.

Sarin Nerve Gas

Blocks cholinesterase, causing constant muscle contraction.

Neurotransmitter Synthesis

Process of creating neurotransmitters in neurons.

Neurotransmitter Storage

Storing neurotransmitters in presynaptic neurons.

Neurotransmitter Breakdown

Decomposition of neurotransmitters in the synapse.

Central Nervous System (CNS)

Brain and spinal cord; neural processing site.

Peripheral Nervous System (PNS)

Nerves connecting CNS to body organs and muscles.

Somatic Nervous System

Voluntary control over skeletal muscles.

Autonomic Nervous System

Involuntary control maintaining homeostasis.

Sympathetic Nervous System

Activates 'fight or flight' response.

Parasympathetic Nervous System

Promotes 'rest and digest' functions.

Cerebral Hemispheres

Two halves of the brain, controlling opposite body sides.

Cerebellum

Coordinates voluntary movements and balance.

Pons

Connects different parts of the brain.

Medulla Oblongata

Controls vital functions like breathing and heart rate.

Hypothalamus

Regulates homeostasis and autonomic functions.

Spinal Cord

Transmits signals between brain and body.

Grey Matter

Contains unmyelinated neurons in CNS.

White Matter

Contains myelinated neurons in CNS.

Dorsal Root

Carries sensory information to spinal cord.

Ventral Root

Relays motor information to effectors.

Paraplegia

Paralysis below the first thoracic vertebra.

Quadriplegia

Paralysis above the first thoracic vertebra.

Cerebrospinal Fluid

Protects spinal cord and brain.

Meninges

Three-layer membrane surrounding the brain.

Dura Mater

Outer membrane surrounding the brain and spinal cord.

Arachnoid Mater

Middle layer of the meninges.

Pia Mater

Inner layer of the meninges, adheres to brain.

Cerebrospinal Fluid

Fluid that cushions and nourishes the brain.

Cerebrum

Largest brain part, divided into hemispheres.

Cerebral Cortex

Outer layer of the cerebrum, contains grey matter.

Frontal Lobe

Responsible for decision making and voluntary movements.

Parietal Lobe

Processes sensory information and body position.

Temporal Lobe

Involved in auditory reception and language comprehension.