Bio-30 Unit A1: The Nervous System

Homeostasis

The nervous system receives an interprets information from the internal and external environment, and produces a rapid response to maintain dynamic equilibrium

Nervous system

Uses electrical impulses, along axons and chemical neurotransmitters across synapses for rapid short-term targeted responses

Endocrine system

Uses chemical signals ( hormones ) Released into the bloodstream for slower longer, lasting systemic responses

Central nervous system (CNS)

Consist of the brain and spinal cord. Functions as the primary command centre for integrating processing and storing sensory information and issuing motor commands.

Peripheral nervous system (PNS)

Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves, divided into two types: stomatic and autonomic.

Somatic

Voluntary skeletal muscle control & reflex arcs. (PNS)

Autonomic

Involuntary organs/glands. (PNS)

Sympathetic: “fight or flight” (dilates pupils, accelerates heart rate, inhibits digestion)

Parasympathetic: “rest and digest” (constricts pupils, slows heart rate, stimulates digestion)

Cell body (soma)

Contains nucleus and cytoplasm; processes incoming dendrite signals.

Dendrites

Branches extensions that receive stimuli and conduct impulses toward soma.

Axon

Long process conducting action potentials away from cell body to terminals.

Axon terminals

Bulbous ends containing neurotransmitters in vesicles.

Schwann cells

Neuroglial cells in PNS that form the insulating myelin sheath.

Myelin sheath

Lipid insulating layer that speeds impulse transmission via saltatory conduction.

Nodes of ranvier

Uninsulated gaps between Schwann cells where action potential jumps (100m/s vs 1m/s)

Neurilemma

Delicate outer PNS membrane that promotes axon regeneration after injury.

Nucleous

Main part of the neuron responsible for cell function

Interneurons (association neurons)

Located entirely within the Central nervous system, they act as a link between the sensory and motor neurons. They process and integrate incoming sensory information, and relay outgoing motor information.

Motor (efferent) neurons

Transmit information from the central nervous system to the muscles, glands and other organs (effectors).

Myelinated neurons

Make up the white matter of your brain, which is responsible for conducting nerve impulses. Capable of regenerating after injury.

Unmyelinated neurons

Make up the gray matter of your brain, which is responsible for processing information and generating nerve impulses. Not capable of regenerating after injury.

Sensory receptors

Receive information about external or internal environment

Sensory (afferent) neuron

Relay information from sensory receptors to central nervous system for processing

Motor neuron

Relay information from the interneuron to the effectors

Effectors

Cell or organ that responds to stimulus. Muscles/Organs/glands.

Synapse

a gap or space between two neurons or a neuron and an effector.

Synaptic knobs

Contain vesicles which hold neurotransmitters that allow impulses to be transmitted across the gap or synapse.

Cholinesterase

An enzyme that breaks down acetylcholine and other neurotransmitters

Ion pump

Specialized proteins that produce an unequal concentration of charged particles between the cell and its extracellular environment.

Repolarization

The process of restoring the original polarity of the nerve membrane.

Hyperpolarization

Occurs when the inside of the nerve cell membrane has a greater negative charge than the resting membrane; Caused by excessive diffusion of potassium out of the cell.

Refractory period

Recovery time required before a neuron can produce another action potential.