Human Biology Test Revision

Nervous System

One of the body's two communication systems, coordinating voluntary and involuntary actions.

Neurons

The basic structural and functional units of the nervous system, specialized for rapid communication of messages.

Dendrites

Extensions of the neuron that carry messages into the cell body.

Axon

A long extension of the neuron that carries nerve impulses away from the cell body.

Myelin Sheath

A fatty layer that covers most axons, providing insulation and speeding up nerve impulse transmission.

Schwann Cells

Cells that form the myelin sheath outside the brain and spinal cord.

Nodes of Ranvier

Gaps in the myelin sheath where ion exchange occurs, facilitating the rapid conduction of nerve impulses.

Synapse

The junction between neurons, where neurotransmitters transmit signals across a small gap.

Neurotransmitters

Chemicals that transmit signals across the synapse from one neuron to another.

Sensory Neurons

Neurons that carry messages from sense organs to the central nervous system.

Motor Neurons

Neurons that carry messages from the central nervous system to muscles and glands.

Interneurons

Neurons that connect sensory and motor neurons within the central nervous system.

Multipolar Neurons

Neurons with one axon and multiple dendrites, most common in the brain and spinal cord.

Bipolar Neurons

Neurons with one axon and one dendrite, found in sensory organs like the eyes and ears.

Unipolar Neurons

Neurons with a single extension; typically found in insects.

Pseudounipolar Neurons

Neurons that appear unipolar but have two functional extensions; common in sensory pathways.

Nerve Fibres

The axons and dendrites of nerve cells, grouped together to form nerves.

Nerve

A bundle of nerve fibers in the peripheral nervous system.

Electrochemical Change

The process involved in the transmission of a nerve impulse, involving electrical and chemical gradients.

Membrane Potential

The potential difference across a cell membrane, crucial for nerve impulse conduction.

Resting Membrane Potential

The electrical charge of a neuron at rest, typically around -70 mV.

Depolarisation

The phase in which the membrane potential increases due to sodium ions entering the cell.

Action Potential

A rapid rise and fall in membrane potential that transmits a signal along a neuron.

Repolarisation

The phase where the membrane potential returns to a more negative value after depolarization.

Hyperpolarisation

The phase where the membrane potential becomes more negative than the resting potential.

Refractory Period

The period after an action potential during which the neuron cannot fire again.

Saltatory Conduction

The process by which action potentials jump from node to node along myelinated axons.

All-or-None Response

The principle that a nerve impulse occurs fully or not at all, regardless of stimulus size.

Neurotransmitter Effects

The influence of chemicals on the transmission of nerve impulses across synapses.

Receptor

A structure that detects changes in the internal or external environment.

Thermoreceptors

Receptors that respond to heat and cold, helping to regulate body temperature.

Osmoreceptors

Receptors in the hypothalamus responding to osmotic pressure in the body.

Chemoreceptors

Receptors sensitive to chemicals, involved in taste and smell.

Pain Receptors

Receptors that detect tissue damage and excessive stimulation, primarily in the skin.

Reflexes

Rapid, automatic responses to stimuli, involving a small number of neurons.

Innate Reflexes

Protective reflexes present from birth.

Acquired Reflexes

Learned reflexes based on experience, such as riding a bicycle.

Central Nervous System (CNS)

The part of the nervous system consisting of the brain and spinal cord.

Cranium

The bony structure that protects the brain.

Meninges

Three layers of protective tissue covering the brain and spinal cord.

Cerebrospinal Fluid (CSF)

Fluid surrounding and cushioning the CNS, providing support and transport.

Cerebrum

The largest part of the brain, responsible for higher brain functions like thought and memory.

Cerebral Cortex

The outer layer of the cerebrum, involved in complex brain functions.

Corpus Callosum

The band of nerve fibers connecting the left and right cerebral hemispheres.

Cerebellum

Part of the brain responsible for coordination, posture and balance.

Hypothalamus

A small brain region controlling homeostasis and autonomic functions.

Medulla Oblongata

The part of the brain that controls vital autonomic functions like heart rate and breathing.

Spinal Cord

A cylindrical structure extending from the brain, facilitating communication between brain and body.

Ascending Tracts

Sensory pathways carrying messages from the body to the brain.

Descending Tracts

Motor pathways carrying messages from the brain to the body.

Peripheral Nervous System (PNS)

Nervous system outside the CNS, responsible for carrying messages to and from the CNS.

Cranial Nerves

Twelve pairs of nerves that emerge directly from the brain.

Spinal Nerves

Thirty-one pairs of mixed nerves that emerge from the spinal cord.

Afferent Division

The sensory division of the PNS that carries impulses to the CNS.

Efferent Division

The motor division of the PNS that carries impulses away from the CNS.

Autonomic Nervous System (ANS)

Part of the PNS that controls involuntary body functions.

Sympathetic Division

Part of the ANS responsible for the 'fight or flight' response.

Parasympathetic Division

Part of the ANS responsible for 'rest and digest' functions.

Sodium-Potassium Pump

A carrier protein that moves sodium and potassium ions across the cell membrane.

Leakage Channels

Protein channels open all the time for ion flow in and out of the neuron.

Voltage-Gated Channels

Channels that open in response to changes in membrane potential.

Ion Channels

Protein structures that allow specific ions to enter or exit a neuron.

Threshold Stimulus

The minimum stimulus required to trigger an action potential.

Chemical Agents

Substances affecting neurotransmitter action and nerve impulse transmission.

Acetylcholine

A neurotransmitter involved in muscle action and synaptic transmission.

Organophosphates

Chemicals that disrupt neurotransmitter function, leading to muscle paralysis.

Blood-brain Barrier

A protective barrier that limits the passage of substances into the brain.

Electrolytes

Ions that conduct electricity in a solution, vital for nerve function.

Phospholipid Bilayer

The structural foundation of cell membranes, creating a barrier to ion movement.

Positive Feedback Loop

A process where an output enhances or increases a change in a system.

Negative Feedback Loop

A process where an output reduces or counteracts a change in a system.

Homeostasis

The maintenance of stable internal conditions in the body.

Neuronal Plasticity

The ability of neurons to change their connections and behavior based on experience.

Electroencephalogram (EEG)

A test that detects electrical activity in the brain.

Phantom Limb Syndrome

A condition where amputees feel sensations or pain in a limb that is no longer there.

Neurogenesis

The process of forming new neurons in the brain.

Neuronal Firing Rate

The frequency at which a neuron fires action potentials, affecting signal strength.

Somatic Nervous System

The part of the PNS that controls voluntary muscle movements.

Visceral Nervous System

The part of the PNS that controls involuntary actions, affecting internal organs.