Chapter 12 nervous system

What are the components of the CNS

Brain and spinal cord

PNS main components

All nervous tissue outside brain & spinal cord

PNS division: Controls voluntary movement, carries sensory info to CNS

Somatic (SNS)

PNS division: Controls involuntary body functions

Autonomic (ANS)

PNS division: Network of nerves in digestive tract that controls digestion, influenced by ANS

Enteric (ENS)

Group of cell bodies in the CNS

Nucleus

Bundle of axons in the CNS

Tract

Group of neuron cell bodies in PNS

Ganglion

Bundle of axons in the PNS

Nerve

Gray matter

Made of neuron cell bodies, dendrites, and unmylinated axons. Processes info

White mater

Made of myelinated axons, transmits info

Neurons structure: Contains nucleus

Soma (cell body)

Neurons structure: Receives signals

Dendrite

Neurons structure: Carries signals away

Axon

Neurons structure: Determines when action potential starts

Axon hillock

Neurons structure: Releases neurotransmitter to communicate with other cells

Axon terminal

Neurons structure: Insulates axon, speeds up electrical signals.

Myelin sheath

Neurons structure: Gaps in myelin sheath, action potential regenerate.

Nodes of Ranvier

Neuron polarity: One process, carry sensory info, touch, pain, temp.

Unipolar

Neuron polarity: 2 process, special senses

Bipolar

Neuron polarity: One axon, multiple dendrites, motor neurons.

Multipolar

Glial cell in CNS: Support, Blood brain barrier, most abundant, common in gray matter

Astrocyte

Glial cell in CNS: Produce myelin sheath

Oligodendrocyte

Glial cell in CNS: Smallest & least abundant, immune cells of CNS

Microglia

Glial cell in CNS: Produce and circulate CSF

Ependymal cells

Glial cell in PNS: Surround neuron cell bodies, provide support.

Satellite cell

Glial cell in PNS: Produce myelin sheath

Schwann cell

Step 1 in motor response pathway: Sensory input (afferent)

Thermoreceptors detect, neurotransmitters pass signal to another neuron.

Step 2 in motor response pathway: Integration (CNS processing)

Sensory info travels to brain, thalamus relays info, temp is interpreted, brain decides water too hot must move hand.

Step 3 in motor response pathway: Motor response (Efferent)

Motor command generated, command travels down spinal cord, at NMJ ACh is released triggering signal in muscle to contract.

Sensory (afferent) division

Carrying signals TO the CNS

Motor (Efferent) division

Carries signals FROM the CNS to the effector organs

Graded potential

Small change in neurons electrical charge, varies in strength.

Action potential

Rapid electrical signal that travels alone axon.

Threshold potential

Membrane voltage needed to trigger action potential.

Propagation

Movement of action potential along axon

Synapse

Junction where neuron communicates with another neuron, muscle, or gland.

Phospholipid bilayer

Hydrophobic, prevents charged particles from crossing freely.

Sodium potassium pump

3 sodium (Na+) out, 2 potassium (K+) in

Type of gated channel: Opens when a specific signaling molecule binds.

Ligand

Type of gated channel: Opens due to physical distortion, pressure, stretch touch.

Mechanically

Type of gated channel:Opens to a change in membrane voltage.

Voltage

Type of gated channel: Nongated, random opening

Leakage

Resting membrane potential

Electrical charge across membrane when its not sending action potential

Action potential phase: Depolarization

Reaches threshold, Na+ (sodium) rushes into neuron, becomes more positive.

Action potential phase: Repolarization

K+ (potassium) rushes out of neuron, becomes more negative.

Action potential phase: Hyperpolarization

Too much K+ leaves, more negative than resting.

Action potential phase: Return to resting potential

K+ channels close, membrane returns to -70mV

Absolute refractory period

caused by inactivation of voltage gated Na+ channels

Relative refractory period

K+ channels are still open, can be started, only by much stronger stimulus.

Propagation of action potential: Continuous conduction

Unmyelinated axons, slower

Propagation of action potential: Saltatory conduction

Myelinated axon, jumps between Nodes of Ranvier, faster.

Graded potential type: Sensory neuron generates an action potential

Generator

Graded potential type: Specialized sensory cell releases neurotransmitters

Receptor

Graded potential type: GP that occurs after signal from another cell at a synapse is received.

Postsynaptic

Graded potential postsynaptic type: Causes depolarization, increases change of AP

Excitatory postsynaptic potential

Graded potential postsynaptic type: Causes hyperpolarization, makes neurons less likely to fire

Inhibitory postsynaptic potential

Cholineric system

Uses ACh as neurotransmitter to send signals between cells

Type of ACh receptor: Ion channel, excitatory

Nicotinic

Type of ACh receptor: Metabotropic, inhibitory.

Muscarinic

Type of amino acid neurotransmitter: Main excitatory NT in CNS

Glutamate

Type of amino acid neurotransmitter: Main inhibitory NT in brain

GABA

Type of amino acid neurotransmitter: Major inhibitory NT in spinal cord

Glycine

Type of biogenic amines: Mood, sleep, appetite

Serotonin

Type of biogenic amines: Reward, motivation, movement

Dopamine

Type of biogenic amines: Alertness

Norepinephrine

Type of biogenic amines: Emergency response

Epinphrine (adrenaline)

Type of biogenic amines: Short chains of amino acids that act as chemical messengers, modify cell signaling.

Neuropeptides

The effect of a NT (excitatory or inhibitory) depends on what

The receptor it binds to

Ionotropic receptor

Directly opens an ion channel when bound by a neurotransmitter

Metabotropic receptors

Slower but longer lasting effects

Metabotropic process

NT binds, G protein activates, Effector protein activates, 2nd messenger forms, cell responds.

Where are interneurons found?

CNS only

An excitatory postsynaptic potential is caused by the influx of which ion into the postsynaptic neuron?

Sodium

The rapid influx of Na+ ions into a neuron causes which phase of the action potential?

Depolarization

What is a reason why CNS axons do not regenerate well after injury?

Oligodendrocytes and astrocytes create an inhibitory environment

Division of the ANS: Fight or flight

Sympathetic

Division of the ANS: Rest and digest

Parasympathetic

At resting membrane potential, which ion is more concentrated inside the neuron?

K+ (potassium)

The motor (efferent) division of the PNS is further divided into which two systems?

Somatic and Automic

What is an Excitatory Postsynaptic Potential (EPSP)?

A depolarization of the postsynaptic membrane that brings the neuron closer to threshold

The process by which multiple graded potentials are added together to reach threshold is called:

Summation

Multiple sclerosis (MS) is an autoimmune disease where the body's immune system attacks and damages

Oligodendrocytes in the CNS

Indirect signaling

When a neurotransmitter binds to a metabotropic receptor, it activates a G-protein, which triggers a second-messenger signaling pathway inside the cell.

The blood-brain barrier is formed by which two components working together?

Astrocytes and tight junctions of capillary endothelial cells

Why do peripheral nerves have a better chance of regeneration than central nerves?

Schwann cells

Which type of nervous tissue cell is most likely to form a brain tumor (glioma)?

Glial cells

A disease that damages the tracts in the brain would affect:

The transmission of signals between different areas of the brain

PNS division organization

Sensory (afferent) & Motor (efferent) → Somatic & Autonomic → Sympathetic & Parasympathetic (ANS)

What ion is responsible for triggering the release of neurotransmitters from the presynaptic terminal?

Calcium

The ability of a synapse to strengthen or weaken over time is known as:

Synaptic plasticity

The transport of materials from the axon terminal back to the cell body is called:

Retrograde transport

An Inhibitory Postsynaptic Potential (IPSP) is often caused by the influx of which ion?

Chloride (Cl-)

Type of summation: ONE neuron fires multiple times rapidly

Temporal

Type of summation: MULTIPLE neurons fire at the same time

Spatial summination

What is synaptic depression

temporary decrease in the strength of communication between neurons, often caused by repeated stimulation.

Anterograde transport

Carries away from cell body

Retrograde transport

Returns to the cell body

Myelinated axons are more energy efficient than unmyelinated axons because:

Action potentials only need to be regenerated at the nodes of Ranvier