Bio 30-1 Section 13

Central Nervous System

Central Nervous System

The Brain and spine.

Coordinating center

Peripheral Nervous System

Other nerves.

Relays info between body and CNS

Nerves have neurilemma

Autonomic Nervous System

Part of PNS

Communicates with organs and glands (internal involuntary functions).

CNS —> preganglionic neuron —> ganglion —> postganglionic neuron —> organ/muscle/gland

Sympathetic (stress)

Parasympathetic (peace)

Connects CNS to inside.

Somatic Nervous System

Part of PNS

Communicates with senses and voluntary movement.

Sensory NS; afferent, sensory input

Motor NS; efferent, motor output.

Connects CNS to the outside.

Governed by 12 cranial nerves and 31 spinal nerves

Glial cells

Structural and metabolic support to neurons.

Dendrites

Listens and receives messages.

Myelin Sheath

Schwann cells, myelin, nodes of Ranvier work together to speed through messages.

Axon

Sends messages

Myelinated, have nodes of Ranvier and increased diameter.

3 Types of Nerve Cells

Sensory (Afferent)

Interneurons

Motor (Efferent)

Sensory Nerve Cell

Relay info from sensory receptors.

Groups = ganglia

Afferent

Interneurons Nerve Cells

Links neurons

In spine.

Motor

Relay info to effectors: muscles, glands, etc.

Efferent

Neurilemma

Allows for slow repair in the peripheral nervous system (grey).

Reflex Arc

Sensory Receptor - receives stimulation

Sensory Neuron (ganglion in groups) - sends electrical impulses

Interneuron (in spine) - making the decisions

Motor Neuron - carries efferent impulses to the effector

Effector - perform reflex action

Plasticity

The brains ability to grow, learn.

Axons grow and myleinate.

Impulse traveling

Going along the axon by switching between resting potential and action potential.

Sodium-Potassium Pump

The pump that moves sodium and potassium across the cell membrane.

Movement of Action Potential

Does not move but triggers farther action potential (domino effect)

Depolarization causes sodium channels to open nearby.

Backwards impulses impossible b/c of refractory period.

Signal jumps between nodes of Ranvier.

Threshold

Nerves only fire when ________ is met.

Overshooting _________ does not affect effector.

Rest (Action Potential Sequence)

1st

Everything in system closed

-70mV

Straight line on graph.

Threshold (Action Potential Sequence)

2nd

Some Na+ starts going through Na+ pump.

-55mV

Lower part of climbing sequence on graph.

Depolarization (Action Potential Sequence)

3rd

Na+ rushes through Na+ pump.

Anything above -55mV around 0mV

The incline on the graph.

Channel Changer (Action Potential Sequence)

4th

Na+ closes and K+ pump opens with K+ starting to go through.

40mV

The maximum point of the graph.

Repolarization (Action Potential Sequence)

5th

All K+ moves through K+ pump.

Around 0mV

The declining section of the graph.

Hyperpolarization (Action Potential Sequence)

6th

Too much K+ passes through the K+ pump

-75mV

Point of graph past the baseline

Refractory Period (Action Potential Sequence)

7th

Molecules travel through sodium-potassium pump to restore everything to normal.

-70mV

Final part of graph that matches the first part at the baseline.

Synapses

tiny gaps between neurons (20 nanometers) most involve many neurons.

Presynaptic neuron

Releases neurotransmitter in vesicles

Neurotransmitters

Excitatory and Inhibitory

Excitatory

Increases polarization by opening Na+ gates

Inhibitory

Decreases depolarization by opening K+ gates

Acetylcholine

Excitatory

Opens Na+ channels on postsynaptic neuron (depolarization)

Must be destroyed so neuron can repolarize.

Cholinesterase

Destroys acetylcholine.

Can be used to slow dementia and Alzheimer’s.

Used in insecticides so the heart contracts but never relaxes causing death.

Summation

When multiple neurons work together to depolarize another.

Norepinephrine

Uses to treat low blood pressure (increase blood pressure by narrowing blood vessels of the heart)

As a neurotransmitter, it is released by nerve cells in the brain and near the spinal cord.

Plays an important role in the fight-or-flight response, boosts alertness, affects sleep, etc.

Dopamine

Involved in controlling movement, a lack of it can lead to Parkinson’s disease.

Plays a role in the brain’s reward system. Helps aid the flow of information to the brain regions responsible for thought and emotion.

Can also create feelings of pleasure, certain drugs cause large amounts of it to flood the systems.

Serotonin

Known as the happy chemical, as it seems to play an important role in regulating mood. Low levels have been associated with depression.

GABA (Gamma-aminobutyric acid)

Inhibit or reduce activity of the neurons or nerve cells.

Plays an important role in behavior, cognition, and the body’s response to stress.

Low levels have been linked to schizophrenia, depression, anxiety, and sleep disorders.

Inhibitory Impulses

Essential

Allow you to focus on what’s important and not all incoming information.

GABA is the most common.

Protective Layers of the Central Nervous System

Dura Mater (outer)

Arachnoid mater (middle)

• Cushion/immune/nutrient and waste

• Connect to endocrine

• Spinal tap - ID meningitis

Pia Mater (inner)

Spinal Cord

Carries message between brain and body.

Starts in foramen magnum

White Matter

• Myelinated nerve fibre’s from sensory and motor neurons

Grey Matter

• non-myelinated interneurons

Dorsal (back) Root: info to spine

Ventral (front) Root: info to effectors

Brain Structure

Forebrain

Midbrain

Hindbrain

Spinal Cord

Forebrain Structure

Two Hemispheres

Four Lobes

• Frontal

• Temporal

• Parietal

• Occipital

Corpus Callosum

Thalamus, Hypothalamus, pituitary gland, olfactory bulbs.

Frontal Lobe

Is both reason and control.

Temporal Lobe

Memory and emotion control

Parietal Lobe

Spatial, temperature and touch

Occipital Lobe

Visual

Corpus Callosum

Bridges both hemispheres

Thalamus

Relays sensory info to cerebrum

Hypothalamus

Hormone control and hemostasis.

Pituitary Gland

Releases hormone

Olfactory bulbs

Process smell

Midbrain Structure and Function

Four spheres of grey matter.

Relays for eye and ear reflexes.

Hindbrain Structure

Cerebellum

Pons

Medulla Oblongata

Cerebellum

Limb movement, balance, muscle tone.

Pons

“Bridge”

Relay between cerebellum and medulla.

Medulla Oblongata

Autonomic control,

Connects CNS to PNS

Alzheimer’s Disease

Most common neurodegenerative disease, affecting memory (hippocampus) and emotional centers (Amygdala)

Most common in patients over 65

Genetic and environmental triggers

Plaques outside, tangles inside.

Cholinesterase inhibitors improves activity.

Sympathetic Nervous System

Part of PNS (Autonomic)

Stress

Short preganglionic nerves (acetylcholine), long postganglionic nerves (norepinephrine)

Extends from ribs and back

Parasympathetic Nervous System

Part of PNS (Autonomic)

Peace

Long preganglionic nerves (acetylcholine), short postganglionic nerves (acetylcholine + nitric oxide)

Extends from brain, neck, and tailbone.

Vagus

Parasympathetic nerve

Affects heart, lungs, liver, pancreas, and digestive tract.