Nervous System - A&P 1

Neurology

Study of the Nervous System

Functions of the Nervous System

Senses environmental and internal changesIntegration of the informationResponds to the information

Central Nervous System

Brain & Spinal Cord(Basically 1 organ)

Peripheral Nervous System

Nerves that come off of the CNS into the periphery of our body

Afferent System

*Sensory* System - Takes information from receptors TO the control center

Efferent System

*Motor System* - Takes information AWAY from the control center TO an effector

Somatic Nervous System

Deals with efferent pathways that are ALWAYS going to voluntary skeletal muscle

Autonomic Nervous System

Primarily an efferent pathway, deals with anything that works on an involuntary basisHeart, smooth muscle, glandsCan be divided up into the *Sympathetic division and Parasympathetic* division

Sympathetic Nervous System

Fight or Flight"When there are some stressors, deviation from the set points, not maintaining homeostasis, need to be more active. Faster heartbeat, etc.Deals with the viscera

Parasympathetic Nervous System

Rest and Digest" " Idle mode"When at rest/asleep/in homeostasis there is a lot of parasympathetic activity. Slower heart rate, etc.A lot of parasympathetic activity during sleepDeals with the viscera

Neuroglia

...

Neuron

Functional unit of the nervous systemNeurons don't divide "The neuron that does the work, the circuitry, that evaluates the set points and stress, the neuron that conducts info from a control center to an effector or a receptor to a control center

Neuroglia

The "Support Tissue"Neuroglia DOES divide If someone has a brain tumor, it's not a neuron but the Neuroglia that's the problem - they have a "Glioma

How much Neuroglia is there per Neuron?

50-80 Neuroglia cells per 1 neuron

Astrocyte

FUNCTION: Conduct nutrients to the Neuron from a source(Can also conduct appropriate nutrients to an Axon)Has Cytoplasmic extensions coming off of it, and forming plate-like structures that envelop capillaries Makes contact with Neurons, and other cells

Blood-Brain Barrier

Blood-Brain Barrier = Endothelia + AstrocyteHighly selective fluid barrier that separates the blood from the nervous tissue; Astrocytes conduct appropriate nutrients to Neurons, while keeping the wrong ones out

Microglia

White blood cells - LeukocytesEliminates dead tissue, plays a role in the immune response to infection

Axon

Long appendage coming off of a Neuron

Schwann Cells

Special cells in the peripheral nervous system that wraps around the Axon nerve fibers. Forms a Myelin sheath of pure phospholipid bilayer around the axonSchwann cells are not in intimate contact with each other - part of the Axon is exposed, we call this a "Node"Not all Axons have Schwann cells

Function of Schwann Cells

1. Insulates & protects the Axon, keeps it from coming into contact with another Axon2. In conjunction with nodes, greatly increase the rate of impulse propagations (130 meters/second vs 3 meters/second)3. Healing response: if an Axon has been damaged, it will help guide the Axon where it needs to growSimilar to the rubber sheath surrounding a copper wire

Unmyelinated Axon can conduct an impulse how fast?

About 3 meters/second

Myelinated Axon can conduct an impulse how fast?

About 130 meters/second

Is impulse conduction faster in myelinated or unmyelinated neurons?

Myelinated

How to Schwann cells help neurons regrow?

Br creating a tube for where the axon needs to grow, which the axon will grow through

Neuron body has all organelles for a Eukaryotic except for which ones?

Except for the ones involved in cell division

Dendrite

Conducts an impulse to the cell body(the word "Dendrite" means "branch")

Axon

Conducts an impulse away from the cell body

A neuron has many _________, but only one ____

many dendrites; only one axon

Axon Hillock

Tapered, cone-shaped region of an axon where it joins the cell body.The "trigger" that determines whether the neuron is going to conduct an impulse down the axon or not. Neurons can only have 1 trigger, never 2

Axoplasm

Cytoplasm inside the Axon

Axolemma

Axon cell membrane

Axon collaterals

Branches coming off of the axon

Synaptic End Bulbs

The terminal end of an axon, has a "bulb" shape. same physiology (function) as Synaptic End Bulbs from Myology lecture

Synaptic Vesicles

Vesicles that contain neurotransmitters

Myelinated Neuron

Nerve fiber with Schwann Cells covering parts of the Axon leaving Nodes in between.

Unmyelinated Neuron

A nerve cell no Schwann Cells/Myelin

Neuralfibral Nodes

Narrow gaps between the ends of the segments of myelin that insulate single nerve axons.

Multipolar Neurons

A neuron that has many poles/extensions from the bodyOne is an axon, the others are all dendritesFound in control centers, creating complex circuitry evaluating information and comparing it to the set point. You want a lot of appendages for this.Also found in Efferent motor neurons

Bipolar Neurons

A neuron with two poles coming off of itThey act like "little wires" conducting specific information from one location to anotherLocation: Organs of special sense;> Retina (special cells picking up specific frequencies of light)> Hearing (Special cells picking up specific frequencies of sound)

Unipolar Neurons

Neurons with only 1 pole coming off of the cell body. Found in Afferent Sensory NeuronsAxons & dendrites are determined by presence and absence of Myelin sheath (everything covered in Myelin is Axon). If there's a synaptic end bulb, it's an Axon.Developmentally starts out as bipolar, then the two poles migrate towards each other.A

Afferent Neuron

Goes from Receptor to Control CenterALWAYS Unipolar

What type of neurons are in the control center?

Multipolar

Association Neurons

Interneurons make associations with the genetically predetermined Set PointsAlso neurons that store & access memories

Interneurons

Multipolar neurons within the "control centers" with complex circuitry that communicate internally and intervene between the sensory inputs and motor outputsCan be either Excitatory or Inhibitory

Which Neurons store & access memories?

Association Neurons

Efferent motor neurons are _______polar?

Multipolar

Nerve Processes

Bundles of Axons in cable-like structures

Fiber Tracks

Nerve process (axon bundle) in the Central Nervous System

Ascending (Sensory) Tracts

...

Descending (Motor) tracts

...

Nerve

Nerve process (axon bundle) in the Peripheral Nervous System

Nerves are in the _____ nervous system

Peripheral

Fiber Tracks are in the _____ nervous system

Central

Nerve cell arrangement is similar to the structure of a _____

muscle

Perineurium

Connective Tissue surrounding fascicles (bundles) of Axons

Endoneurium

Connective Tissue surrounding individual nerve fibers/axons

Epineurium

Connective tissue surrounding the entire nerve

The Spinal Cord is located in the _____ _____

Vertebral Canal

Which part of the brain enters the Vertebral Canal

Medulla Oblongata (part of the brain stem)

In adults, the spinal cord stops between ___ and ___.

T12 and L1(Conus Terminalis)

Spinal nerves form the ____ ____ ____

Peripheral Nervous System

Conus Terminalis

Region where the spinal cord stops, between T12 & L1

Spinal Nerves go through the

Intervertebral foramen

How many cervical spinal nerves are there?

8 (C1-C8)

Where is the "freebie"/extra cervical spinal nerve located?

Between the Brain and the Atlas

Why is there a Cervical Enlargement in the spinal cord?

Cell bodies of motor neurons for Upper Appendages are housed there

Why is there a Lumbar Enlargement in the spinal cord?

Cell bodies of motor neurons for Lower Appendages are housed there

Which spinal nerves "droop" through the vertebral canal until they reach their respective intervertebral foramen?

Lumbar nerves

Meninges

A set of 3 membranes covering the brain and spinal cord, that protect it:Dura MatterArachnoidPia Matter

Dura Matter

The outermost layer of the meninges surrounding the brain and spinal cordVery tough connective tissue sheath, adjacent to periosteum

Arachnoid

Middle layer of the meninges, attached to Dura Mater

Pia Matter

Very thin, highly vascular membrane in intimate contact with the brain itself

The Central Nervous System has a sort of ____ consistency

Gelatinous

The entire Central Nervous System (brain and spinal cord) is suspended in

Cerebrospinal Fluid

Cerebrospinal Fluid functions

Acts as a "shock absorber" the protect the CNS from physical traumaSupplies nutrients and removes waste from nervous tissue

Subarachnoid Space

A space in the Meninges beneath the Arachnoid Membrane and above the Pia Mater that contains the Cerebrospinal Fluid, as well as little ligament-like structures holding the brain in place

Subdural Space

...

Epidural Space

Space between Periosteum and Dura MaterA lot of adipose connective tissue for protection, and vasculature as well.

Innermost Meningeal Layer

pia mater

Outermost Meningeal Layer

Dura Mater

Middle Meningeal Later

Arachnoid

Two Lateral Ventricles of brain

Left & Right, CSF flows from this one into the third ventricle

How many ventricles are in the brain?

4

Cerebral Aquaduct

Little "tube" that connects the third and fourth ventricles

How much Cerebrospinal Fluid is produced per day?

500 mL

Choroid Plexus

Collection of blood vessels and Neuroglia that creates a highly selective fluid barrier that allows a very precise fluid to flow out of it from the blood into the lateral ventriclesThere are 4 of these, 3 laterally; one in the 3rd and 4th ventricle tooThey each produce a portion of the total 500ml of CSF produced every day

Median Aperture

An opening in the roof of the fourth ventricle that connects to the subarachnoid space, CSF can flow through here

Arachnoid villi

Allows CSF to flow into blood sinus and return to general blood circulation

Lateral Apertures

pair of openings from the fourth ventricle to the subarachnoid space on either side and between the medulla and cerebellum that CSF flows through

Superior Sagittal Sinus

Blood sinus where CSF is reabsorbed into general blood circulation

Myelin sheath is multiple layers of _____ _____

Phospholipid Bilayer

Are dendrites ever myelinated?

No

Central Canal

Spans length of spinal cord. Contains flowing CSF. Supplied nutrients and removes waste from surrounding neural tissue.

Anterior Median Fissure

Divides the spinal cord into left and right halves

Posterior Median Sulcus

Divides the spinal cord into left and right halves

Gray Matter (Spinal cord)

Has control centers("CPU")Consists of cell bodies, dendrites, axons

White Matter (Spinal cord)

Consists of Myelinated fiber tracts that communicate info.("Cables")No control centersGets it's white color from Phospholipid Bilayer of the Myelin

Dorsal Root Ganglion

Contains cell bodies of sensory neurons; thus increased size

The Dorsal root is ALWAYS _____

Sensory

The Ventral root is ALWAYS _____

Motor

EPSP

Excitatory Postsynaptic Potential; produced by excitatory interneurons

IPSP

Inhibitory Postsynaptic Potential; produced by inhibitory interneurons

Excitatory Interneurons

Produces Excitatory Postsynaptic Potentials

Inhibitory Interneurons

Produces Inhibitory Postsynaptic Potentials

Posterior (Dorsal) Horns

Has synapses with different sensory neurons.Comes in contact with interneurons, either excitatory or inhibitory

Anterior (Ventral) Horns

Somatic/VoluntaryVoluntary skeletal muscle motor neurons are always housed here

Lateral Horns

Automatic/InvoluntaryAny involuntary neurons are housed here

Ascending Tracts

ALWAYS carries sensory information from receptors to the brain

Descending Tracts

ALWAYS motor tracts, going from brain to motor neurons

Naming of tracks

Binomial nomenclature: two wordsFirst word is Origin, second is destination'Example: Corticospinal. Originates in the Cerebral Cortex, going to spinal ford. Therefore is descending, therefore a motor neuron.

Order of nerve impulses

1. Receptor picks up information2. Picked up by a unipolar afferent neuron3. Goes through the Dorsal route4. Enters Posterior Gray Horn5. Synapses with Interneurons ( the "circuitry", either excitatory or inhibitory)6. Goes through Efferent motor neuron to effector

Involuntary/Autonomic Motor neurons are housed in the

Lateral Gray Horn

Voluntary/Somatic Motor neurons are housed in the

Anterior Gray Horn

Efferent Motor neurons go through the

Ventral Route

Ventral Route is always _____

efferent/motor

Afferent Sensory Neurons are always _____

Excitatory

excitatory interneurons

Cause EPSPs in the motor neuron going to the flexor muscle (ex: the biceps - flexes to pull the hand away from the hot stove). (withdrawal reflex)

Stretch Reflex

Protects muscle from overstretching & being damaged when thing & thick filaments don't disengaged

Tendon Relfex

Protects from too much stress

Muscle Spindle

Special Receptor Muscle cell that has been modified to monitor the stretching that occurs in the muscle

Tendon Organ

Monitors the tension and stress on this

Dermatome

Area of skin supplied by a single spinal nerve

The Peripheral Nervous System can be divided up into the _____ System and the _____ System

Afferent & Efferent

The Efferent System can be divided up into the _____ Nervous System and the _____ Nervous System

Somatic & Autonomic

The Autonomic Nervous System can be divided up into the _____ Division and the _____ Division

Sympathetic & Parasympathetic

When we're at rest, the ____ system is dominant

Parasympathetic

Ganglion

A "knot" of nervous tissue that connects 2 motor neurons

In the Autonomic Nervous System, how many motor neurons are there?

2

Preganglionic Neuron

The neuron that's between the CNS and the Ganglion in the autonomic nervous system

Postganglionic Neuron

The neuron that's between the Ganglion and the Viscera in the autonomic nervous system

Anterior Gray Horn synapses with _____ _____ _____

Voluntary motor neurons

Unipolar afferent (sensory) neurons bring information into the _____ _____ _____

Posterior gray horn

Efferent (Motor) Neuron cell body is housed in the _____ _____ _____ only

Anterior Gray Horn

Preganglionic Neuron cell body is in the _____ _____ _____

Lateral Gray Horn

Autonomic Neurons service only the _____, _____, and _____ _____.

Heart, glands, and smooth muscle

In the Parasympathetic System, Preganglionic neurons are very _____, postganglionic neurons are very ___

Long, Short

In the Sympathetic System, Preganglionic neurons are very _____, postganglionic neurons are very ___

Short, Long

Neurotransmitter for Voluntary Skeletal muscle is always _____

Acetylcholine (Ach)

When there is a Ganglion - between pre and post ganglionic neurons, the Neurotransmitter is always _____

Acetylcholine (Ach)

Parasympathetic Neurotransmitter in Effectors is _______

Acetylcholine (Ach)

Sympathetic Neurotransmitter in Effectors is _______

Norepinephrine

In the heart, if Norepinephrine goes up, and Ach goes down, the heart rate will go _____

Up (sympathetic response)

In the heart, if Ach goes up, and Norepinephrine goes down, the heart rate will go _____

Slower (parasympathetic response)

Our body "Idling

Basal Metabolic Rate

Preganglionic Sympathetic Neurons come from

Thoracic and the first 2 Lumbar vertebrae only

Preganglionic Parasympathetic Neurons come from

Certain Cranial nerves, and 3 sacral nerve only

Synaptic Chain Ganglions

Facilitates an integrated Sympathetic nervous response

Blood vessels only have _____ stimulation

Sympathetic

Sweat glands and the Erector Pili muscle only have only have _____ stimulation

Sympathetic

Adrenal gland secretes

Adrenaline (Epinephrine)

Kidneys only have _____ stimulation

Sympathetic

Digestive System, Heart, and Lungs can be both _____ and _____

Sympathetic and Parasympathetic

Skeletal muscle is integrated by:SympatheticParasympatheticBothNeither

Neither (somatic/voluntary NOT autonomic)

The Heart is integrated by:SympatheticParasympatheticBothNeither

Both

Involves Thoracic and Lumbar Spinal segmentsSympatheticParasympatheticBothNeither

Sympathetic

Has long preganglionic Neurons:SympatheticParasympatheticBothNeither

Parasympathetic(Sympathetic has short)

Has short post ganglionic Neurons:SympatheticParasympatheticBothNeither

Parasympathetic

Digestive Tract innervated bySympatheticParasympatheticBothNeither

Both

Dominant when sleepingSympatheticParasympatheticBothNeither

Parasympathetic

Involves ONLY AcetylcholineSympatheticParasympatheticBothNeither

Parasympathetic

Break out into a cold sweatSympatheticParasympatheticBothNeither

Sympathetic (peripheral vasculature vasoconstricts); hot blood gets away from integument

Fight or flight response:SympatheticParasympatheticBothNeither

Sympathetic

Lateral Gray HornSympatheticParasympatheticBothNeither

...

Anterior Gray HornSympatheticParasympatheticBothNeither

...

Involuntary neurons are housed in the _____ _____ _____ of the spinal cord

Lateral Gray horn

Voluntary (Motor) neurons are housed in the _____ _____ _____ of the spinal cord

Anterior Gray Horn

Efferent Motor neurons always go through the _____ _____

Ventral Root