CENTRAL NERVOUS SYSTEM

CNS

Central Nervous System — brain and spinal cord

PNS

Peripheral Nervous System — nerves

-sensory divison

- motor divison

Primary Function of Nervous System

Integrate & coordinate the body's activities

Sensory Input

The process of receiving information from sensory receptors

Integration

The process of interpreting sensory input and deciding on a response

Motor Output

The response to sensory input, carried out by effectors

Effector

Motor neuron, muscle or gland that carries out the response

Neuron

Nerve cell that transmits impulses and makes up ~20% of the nervous system

Axon

Extension of a neuron specialized for conducting electrical impulses, can be 3 ft long

Neuroglia

Supportive cells that support and protect neurons without transmitting impulses

Schwann Cell

A supportive neuroglial cell found in the peripheral nervous system that makes up the myelinated sheath

Myelin Sheath

Fatty substance that covers the axon, protecting and insulating it

Demyelinated Diseases

Diseases like Multiple Sclerosis and Guillain-Barré Syndrome that involve damage to myelin sheaths

Multiple Sclerosis

An immune system attack on myelin sheaths in the CNS, causing paralysis and loss of sensation

Guillain-Barré Syndrome

An immune system attack on Schwann cells, causing pain with muscle weakness

Node of Ranvier

Gaps between Schwann cells filled with protein gates and pumps

Na+/K+ Ion Channels

Protein gates that help sodium (Na+) and potassium (K+) flow down their gradient

Na+/K+ PUMPS

Active transport mechanisms that move Na+ out of the axon and K+ into the axon

Saltatory Conduction

The process where impulses jump from gap to gap, allowing super fast conduction (250 mph)

Na+

Sodium ion, more concentrated outside the cell at resting state.

K+

Potassium ion, more concentrated inside the cell at resting state.

Polarized

Condition where the inside of the axon is more negative than the outside.

Depolarized

Transition from a negatively charged state to a positively charged state.

Depolarization Causes

Na+ gates close and K+ gates open.

Repolarization

Process of becoming negatively charged again after depolarization.

Hyperpolarization

Condition of being overly negatively charged.

Action Potential

An electrical impulse that is carried along neurons, characterized by a flip flop between positive and negative charges.

Refractory Period

The unresponsive reset phase where Na+ gates are unable to open.

Synapse

The junction of a neuron and another cell, which can be electric or chemical.

Neurotransmitters

Chemicals that carry impulses across synapses from a neuron to a target cell.

Neurotransmission

The process of action potential causing neurotransmitters to be released and bind to receptors.

Ion channel

A protein structure that opens to allow ions to flow, triggering a new action potential.

Reuptake

The process of neurotransmitters being recycled after their release.

Drugs affecting neurotransmitters

Substances that can strengthen signals or block actions, such as caffeine and pain relievers.

Caffeine

A drug that blocks inhibitory neurotransmitters, affecting signal transmission.

Endorphins

Neurotransmitters that block substance P, reducing pain perception.

More than 100 known NTs

Includes neurotransmitters involved in muscle contraction, thermoregulation, mood, emotions, sleep, and memory.

Na+/K+ PUMP

A mechanism that moves K+ back inside the cell and Na+ back outside to restore resting conditions.

Basic Steps of Signal Sending

1. Resting conditions & trigger, 2. Depolarization, 3. Repolarization, 4. Hyperpolarization, 5. Reset.

meninges

protective layer of CNS

- 3 layers

-CSF between layers

meningitis

an acute inflammation of the meninges

- high fever, severe headache & neck sickness

gray matter

cell bodies & some short unmyelinated axons

white matter

myelinated axons

- white & greasy