Intro to CNS

What are the divisions of the Nervous System?

Central Nervous System

Peripheral Nervous System

CNS

Brain and spinal cord

PNS

cranial nerves, spinal nerves, and ganglia

What are the 3 functions of the Nervous System?

Sensation, Integration, and Motor function

Sensation

Sensory perception; continuously receives info from the surrounding environment, concerning physical and chemical stimuli

Integration

Process the information (encoded as electric signal) and transmits it to effectors

Motor Response

Effectors can now produce a response or an effect

Afferent

sensory

ARRIVING at CNS

Efferent

motor

EXITING CNS

Brain

-Receives sensory input from the spinal cord and from its own nerves.

-Processes sensory inputs and initiates appropriate motor outputs

Spinal Cord

-Conducts sensory info from the PNS to the brain

-Conducts motor info from our brain to our various effectors

Sensory Division

sensory info from PNS receptors to CNS

one neuron system

Motor Division

2 divisions

Somatic and Autonomic

Somatic Division

-Voluntary control over Skeletal Muscle

-One neuron system

Autonomic Division

-INVOLUNTARY regulation of SMOOTH MUSCLE, CARDIAC MUSCLE, and GLANDS

-Two neuron system

What type of system is GSE?

General Somatic Efferent

One neuron

What type of System is GVE?

- General Visceral Efferent (autonomic)

- Two neurons

- Preganglionic neuron axon synapses a second neuron in the chain called postganglionic neuron

What muscles does GSE control?

voluntary skeletal muscle

What muscles does GVE control?

cardiac muscle, smooth muscle, and glands

GSA

Somatic Sensory

body senses

GVA

visceral sensory

organ senses

CARDIAC, SMOOTH, GLANDS

GSE

somatic motor

body movement

GVE

visceral motor

organ movement

Involuntary movement

CARDIAC, SMOOTH, GLANDS

It's the first day class and a D1 student decides to show off and flex his biceps. What axon is directly innervating this muscle?

GSE

My favorite food just arrived and my mouth is salivating! What is the axon that is directly innervating my salivary glands?

GVE

A patient arrives to the ER feeling pain from her lower right abdomen. It is possible her appendix is about to burst! What axon is providing the patient with this discomfort?

GVA

Neurons

- Basic functional element of the nervous system

- Generate electrical signals, the action potential, and pass them on to other nerve or muscle cells

- Can be classified on their form or function

Glial Cells

- Support cells

- Do not carry nerve impulses

- Protection, myelin formation, metabolic exchange with the vascular system, capable of mitosis (unlike neurons).

What part of the neurons recieves?

dendrites and cell body

What part of the neuron inetgrates?

axon hillock

What part of the neuron transmits?

Axon

Synapse

- Unidirectional transmission of signals

- Specialized region between two cells

- No contact, but are separated by a narrow 20-micron wide gap

What happens when an impulse reaches the end of an axon?

Small vesicles containing a NT are released into the synaptic gap

What happens to NTs once released into synaptic gap?

- NTs bind to specific receptors on postsynaptic cell to initiate excitatory or inhibitory response.

- The NT is rapidly destroyed by local enzymes.

What are the three structural classifications of neurons?

Multipolar neuron, Bipolar neuron, Unipolar (pseudounipolar) neuron

Most common type of neuron

multipolar neuron, specifically interneurons (20 billion)

Multipolar Neuron

-one axon and multiple dendrites

-Found throughout NS and autonomic ganglia

Bipolar Neuron

-one axon and one dendrite attached to its soma

-retina, olfactory, auditory

Pseudounipolar Neuron

- Axon that splits into 2 branches. 1 branch that runs to the peripheral tissues, and a 2nd branch that leads to the spinal cord.

- Spinal ganglia (dorsal root ganglia) and in some cranial nerve ganglia

Sensory Neurons are what kind of neurons?

commonly pseudounipolar

Motor Neurons are what kind of neurons?

multipolar

Interneurons are what type of neuron?

- Multipolar

- Most common type of neuron (20 billion)

- Transmits information between neurons within the CNS

Myelin

- Spiral layer of closely apposed cell membranes

- Increase action potential conduction speed

- Produced by glial cells

Thicker myelin

faster conduction

Thicker diameter of axon

faster conduction

Purpose of nodes of ranvier

- Saltatory conduction

- Allows for energy efficiency

- Greater speed of conductance

White matter

- Myelinated axons

- Information transmission

- Makes up the outside of the spinal cord

- Makes up the inside of the brain

Grey Matter

- Unmyelinated axon

- Information processing

- Makes up the inside of the spinal cord

- Makes up the outside of the brain

Coronal Plane

divides brain into anterior and posterior parts

Sagittal Plane

divides brain into left and right

Horizontal/transverse plane

divides the brain into superior and inferior parts

ipsilateral

same side

contralateral

opposite side

Orientation at the brain

Superior/ dorsal= towards the top

Inferior/ ventral= towards the bottom

Anterior/ rostral= towards the front

Posterior/ caudal= towards the back

Orientation at the brainstem

Ventral (belly)/ Anterior

Dorsal (back)/ Posterior

What are the five major divisions of the brain

Forebrain - Telencephalon and Diencephalon

Midbrain - Mesencephalon

Hindbrain - Metencephalon and Myelencephalon

Forebrain yields

Structure on TOP

telencephelon

diencephelon

Midbrain Yields

Alphabetical order

Mesencephalon

Hindbrain yields

Alphabetical order

Metencephalon

Myelencephalon

Telencephalon

TELEPATHY/TOP

cerebrum/cerebral hemisphere

largest part of CNS-memory, speech, senses, emotion

Diencephalon

DIET

thalamus, hypothalamus, pineal gland

Thalamus

Forebrain-->diencephalon

relay station of incoming motor and sensory info

Hypothalamus

forebrain-->diencephalon

FOOD center

Pineal gland

Secretes melatonin for sleep cycle

Mesencephalon

midbrain of the brainstem

visual and auditory coordination

motor pathways

Metencephalon

MEeT me at the PONd BELLa

pons and cerebellum

Pons

hindbrain-->metencephalon

handles unconscious processes

Cerebellum

hind brain-->Metencephalon

fine movement and coordination

Myelencephalon

last one alphabetically

Medulla oblongota

Medulla Oblongata

Transmits signals between the spinal cord and higher parts of the brain and autonomic functions - heart beat and respiration

Where does the spinal cord lie

Within the vertebral (spinal) canal of the vertebral column. Continuous rostrally with the medulla oblongata of the brainstem.

Function of spinal cord

Recieves information from, and controls, the trunk and limbs.

How many pairs of spinal nerves are there?

31 pairs of spinal nerves

Dorsal rootlets

Carry sensory information TO spinal cord

SAME DAVE - Sensory, Afferent. Motor Efferent. Dorsal, Afferent. Ventral Efferent.

Ventral rootlets

Ventral is motor VROOOM

Carry motor info AWAY from spinal cord

SAME DAVE - Sensory, Afferent. Motor Efferent. Dorsal, Afferent. Ventral Efferent.

Spinal nerve

-Dorsal root + ventral root

-Mixed, containing both motor and sensory modalities

-Spinal nerve primarily divides into a posterior ramus (B) and an anterior ramus (D).

-Ramus/Rami are also mixed nerves.

Ganglion

group of neuronal bodies outside of the CNS

either sensory(dorsal) or autonomic

Sensory Ganglia

- Dorsal root ganglion

- Pseudounipolar

- All afferent neurons

- Nerve fibers pass through the ganglion without synapsing

Autonomic Ganglion

- Motor

- Multipolar

- GVE

- Preganglionic axon-->autonomic ganglion-->postganglionic axon

Where are the preganglionic cell bodies of the autonomic ganglion located?

Lateral horn of the spinal grey matter.

How does the preganglionic axon leave the lateral horn?

Through the ventral nerve root

Where are the cell bodies of general motor axons located?

The ventral horn of the spinal cord.

Outer surface of nerve

epineurium

connective tissue

What is the epineurium a continuation of in cranial and spinal nerves?

The dura mater.

Nerve is comprised of :

fascicles covered by the perineurium

Individual axons are covered by:

endoneurium

Autonomic Nervous System function

PNS

maintenance, or homeostasis, of internal environment

Where are the cell bodies of postganglionic neurons located?

Autonomic ganglion.

Where are preganglionic cell bodies located of the Autonomic Nervous System?

lateral horn of spinal cord or in a nucleus in the brain

What are the divisions of the Autonomic NS

Sympathetic and Parasympathetic

Preganglionic Neurons of sympathetic division are located exclusively where?

- Thoracolumbar region T1-->L2.

- Lateral horn of spinal grey matter.

Postganglionic Neurons of sympathetic division are located where?

- Sympathetic chain of ganglia that lies near the vertebral column

OR

- Plexus (network of ganglion:Celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion)

Neurotransmitter released by preganglionic sympathetic neurons

acetylcholine

Neurotransmitter released by postganglionic sympathetic neurons

norepinephrine

preganglionic parasympathetic neurons are located where

- Brain stem and Spinal cord (craniosacral region)

- In cranial nerve nuclei associated with cranial nerves 3, 7, 9, 10

postganglionic parasympathetic neurons are located where

close to where they innervate

Which neurotransmitter is released by both pre and postganglionic parasympathetic neurons

acetylcholine

Organization of the sympathetic division of the pre and postganglionic neurons

preganglionic-short

postganglionic-long

Ganglia (sympathetic chain) lies near the vertebral column.

Organization of the parasympathetic division of the pre and postganglionic neurons

preganglionic-long

postganglionic-short

Ganglia are closest to the target organ.

The _______________ __________________ is a special exception that is directly innervated by preganglionic sympathetic neurons

adrenal medulla