Portage learning module 1: Nervous System

What makes up the central nervous system?

brain and spinal cord

What makes up the peripheral nervous system?

All nerves not in the brain or spinal cord

What is the function of the central nervous system?

receives and processes information; initiates action

What are the 2 divisions of the PNS?

Afferent (sensory) and efferent (motor) divisions

What are the 2 parts of the efferent (motor) division?

Somatic and autonomic systems

What is the main function of the somatic nervous system?

This part of the nervous system is involved in voluntary activities the involve skeletal muscles, skin, and joints

What is the main function of the autonomic nervous system?

This part of the nervous system is involved with involuntary actions that involves the glands and smooth muscles of the internal organs

What are the 2 parts of the autonomic nervous system?

sympathetic and parasympathetic nervous systems

What is the main function of the sympathetic nervous system?

fight or flight; activates and prepares the body for vigorous activity, stress, and emergencies

What is the main function of the parasympathetic nervous system?

Rest and digest; operates during normal situations, permits digestion's, and conserves energy

What is the main neurotransmitter of the Sympathetic nervous system?

norepinephrine

What is the main neurotransmitter of the parasympathetic nervous system?

acetylcholine

What protection does the CNS have?

Skull for the brain and vertebrae for the spinal cord

What is the main function of the CNS?

Send impulses to and receive impulses from the PNS

What are nuclei?

clusters of neuron cell bodies in CNS

What are tracts?

bundles of axons in the CNS

What does the brain stem include?

Midbrain, pons, and medulla

What are ganglia?

clusters of cell bodies in the PNS

What are nerves?

bundles of axons in the PNS

What is the main function of the PNS?

To connect all parts of the body to the CNS

What are neurons?

nerve cells that conduct electrical impulses and relay information throughout the body

What is special about neurons?

They do not undergo mitosis

What is the function of a neurons cell body?

Synthesizes all nerve cell products including neurotransmitters

What are dendrites and what is their function?

Branch-like extensions that receive information and conduct an electric impulse toward the cell body

What is the function of an axon?

conducts nerve impulses away from the cell body

What is the function of an axon terminal?

Contains vesicles that house neurotransmitters; sending end of a neuron

What are neurotransmitters?

Chemicals that carry messages from one neurons to the next

What is a synapse?

Gap between neurons

What is a node of Ranvier?

gaps in the myelin sheath/between Schwann cells

What is the myelin sheath?

covers the axon of some neurons and helps speed neural impulses

How are neurons classified based on structure?

Based on the number of extensions from their cell body: multipolar, bipolar, unipolar

What is a multipolar neuron?

a neuron with one axon and many dendrites attached to its soma

What is a bipolar neuron?

a neuron with only one axon and one dendrite

What is a unipolar/pseudopolar neuron?

A neuron that has one extension that branches into 2 parts: one going to the CNS, the other going to the PNS

How are neurons classified based of function?

Sensory, motor, or Interneurons

What type of neurons are afferent (sensory) neurons?

Unipolar; carry info from the PNS to the CNS

What type of neurons are efferent (motor) neurons?

Multipolar; carry Info from the CNS to the PNS

What type of neurons are Interneurons?

Usually multipolar; only in the CNS

What are neuroglial cells?

supporting cells

What are Schwann cells and what do they do?

Specialized cells found in the PNS that are composed of a white fatty layer which is rolled around the axon to provide insulation and increase the speed of impulse transmission

What is saltatory conduction?

The "jumping" of an action potential between the unmyelinated nodes of ranvier

What are satelite cells and what do they do?

Specialized cells in the PNS that help regulate cell body environment

What is axonal regeneration?

When PNS neurons regenerate the axon length with guidance from Schwann cells

What are ependymal cells and what do they do?

Specialized cells in the CNS that circulate the CSF and allow fluid exchange

What are oligodendrocytes and what do they do?

Specialized cells in the CNS that insulate the CNS axons

What are astrocytes and what do they do?

Specialized cells in the CNS that control the chemical environment by wrapping around blood capillaries; recycle neurotransmitters; form scar tissue

What are microglial cells and what do they do?

Specialized cells in the CNS that protect the CNS by scavenging dead or infectious cells or microorganisms

What are the 5 specialized cells of the CNS?

Ependymal, Astrocytes, oligodendrocytes, and microglial cells

What is an action potential?

an electrochemical impulse that travels the length of a neuron created by an unequal distribution of ions

What is resting state?

the state in which there is a negative electrical charge of about -70 millivolts within a neuron

How is resting state maintained?

Sodium-potassium pump that uses active transport to carry ions across the plasma membrane using an integral carrier protein; 3 sodium ions out, 2 potassium ions in

How are the sodium and potassium gates during resting state?

Both are closed

How are sodium and potassium gates during depolarization?

Sodium gates are open allowing sodium to rush into the membrane allowing it to become positive (40mV)

How are the sodium and potassium gates during repolarization?

Sodium gates are closed and potassium gates are open allowing potassium to rush in

How are the sodium and potassium gates during hyperpolarization/afterpolarozation?

Potassium gates are slow to close which causes an undershoot of polarization, dropping the voltage below -70mV before returning

How is the intensity of an action potential distinguished?

The number of neurons stimulated and the frequency they are stimulated

What is the function of neurotransmitters?

to transmit nerve impulses across synapses

Explain how neurotransmitters are released.

When an action potential reaches the axon terminal the change in voltage causes calcium ion channels to open allowing calcium ions to rush in triggering the vesicles to fuse with the plasma membrane. This fusion allows the neurotransmitters to diffuse across the synapse and bind with postsynaptic neuron receptors which triggers an action potential down the next neuron.

What happens if neurotransmitters remain in the synapse?

Overstimulation; avoided buying inhibition

What are the ways neurotransmitter inhibition happens?

Enzymes that breakdown the neurotransmitters, reuptake: neurotransmitters get reabsorbed and stored back in the vesicles

What are the 3 common neurotransmitters?

-Acetylcholine: found at neuromuscular junctions in the PNS

-Norepinephrine/Epinephrine: produces by the adrenal gland

-Dopamine: specialized in the brain to help regulate muscle tone and emotional responses

What are reflexes?

These are rapid and involuntary responses to stimuli

Where do reflex stimuli occur?

Both inside or outside the body

What are subconscious reflexes?

Occur within the body

What are 2 examples of subconscious reflexes?

Blood sugar regulation and shivering

What reflex involves the brain?

Blinking

What is a reflex arc?

A neural pathway that nerve impulses travel

Why are reflexes tested?

To examine the nervous system function

What does the spinal white matter contain?

Axons of neurons

What does the spinal gray matter contain?

Cell bodies of neurons

Where does sensory information enter the spinal cord?

The dorsal root

Where does motor information exit the spinal cord?

Ventral root

What does the dorsal root ganglion contain?

cell bodies of sensory neurons

Where do sensory neurons synapse?

Within the posterior horns

What are spinal reflexes?

Rapid, automatic nerve responses triggered by specific stimuli

What are examples of spinal reflexes?

Flexor reflex and stretch reflex

What are the 5 components of reflex arcs?

receptor, sensory neuron, integration center, motor neuron, effector

What are stretch receptors?

They protect against increases in length that may tear or damage muscle fibers and maintain upright posture

What are muscle spindles?

Sensory receptors in muscle that monitor the amount of stretch

What is the patellar reflex?

Tests the quadriceps femoris muscle. Prevents over stretching of the quads

Explain how a stretch reflex works?

When a muscle spindle detects the stretch, a signal is sent along the afferent neuron, through the dorsal root ganglion to the spinal cord via the dorsal root. The afferent neuron synapses with the efferent neuron in the anterior horn. The efferent neuron travels out the central root to the same muscle

What is the withdrawal reflex?

Pain receptors in the skin generate a nerve impulse that moves along an afferent neuron toward the CNS. The impulse synapses with many Interneurons within the spine

Septum Pellucidum

double membrane that acts as divind wall; separates left and right lateral ventricles; connects corpus callosum to fornix

Commissure

connect the 2 cerebral hemispheres

association fibers

connect areas within the same hemispheres to allow for communication

Corpus Callosum

commissure that connects the cerebral hemispheres (white nerve fibers)

hypothalumus

• forms the floor of the third ventricle

• maintains homeostasis, regulates hunger, sleep, thirst, body temp, water balance, and blood pressure

• control the pituitary gland

• produces hormones that are passes to the posterior pituitary gland for ADH and oxytocin release

Optic Chiasma

x-shaped, optic nerves from eyes meet and partially cross

pituitary gland

regulates body hormones of the endocrine system

mammillary bodies

contain fibers that projet into the thalamus and assist with memory of smell

Pons

• contains bundles of axons traveling between the cerebellum and the rest of the CNS

• works with medulla to regulate breathing rate

• contains sensory and motor nuclei of cranial nerves involved in innervating the jaw, face, and inner ear

Medulla oblongata

• continuous with the spinal cord

• contains several vital autonomic reflex centers for regulating heart rate and force of contractions

Fornix

bundle of nerve fibers that serves as a connection to the hippocampus

thalamus

• in the roof of the third ventricle (one in each hemisphere)

• last portion of the brain for sensory input

• central relay station for sensory impulses traveling upward from othe parts of the body and brain the the cerebrum

• receives all sensory impulses except smell & directs

Pineal gland (in the epthalamus)

secretes melatonin

Corpora Quadrigemina

2 superior + 2 inferior colliculi

arbor vitae

white matter in the cerebellum

Choroid Plexus

• adjusts CSF composition

• formed from a network of blood vessels within the ventricles