Module 2 (Prevet anatomy)

What two major systems make up the nervous system?

1. Central nervous system

2. Peripheral nervous system

The central nervous system consists of

The brain and spinal cord

The peripheral nervous system consists of

peripheral nerves and ganglia

What does the somatic nervous system refer to?

Part of nervous system that regulates muscular function

What does the autonomic nervous system refer to?

Part of nervous system that regulates visceral and special functions

What are the two divisions of the autonomic nervous system?

1. Sympathetic

2. Parasympathetic

What are the two types of cells the nervous system can be divided into?

1. Neurons

2. Glial cells

A neuron is

A basic functional unit of the nervous system

How do neurons communicate with each other?

Through synapses and action potentials

What does the neuron contain?

A cell body called a perikaryon

Dendrite function

Transport impulses towards cell body and there are multiple

Axon function

Transmit signals away from cell body

Axons always ___

Originate as a single process from cell body

3 types of neuron classification

1. Unipolar (pseudounipolar)

2. Bipolar

3. Multipolar

What does unipolar refer to?

The dendrite and axon come together to form a single process in the body

What does bipolar refer to?

The dendrites join together to find a common trunk before reaching a cell body that is at a different site than the original axon

What does multipolar refer to?

A single axon and multiple dendrites in a neuron

Most neurons are ___

multipolar

Types of connections (synapses)

1. Axosomatic

2. Axodendritic

3. Axoaxonic

Axosomatic

between an axon of one neuron and a cell body of another neuron

Axodendritic

between the axon of one neuron and a dendrite of another neuron

Axoaxonic

between an axon of one neuron and an axon of another neuron

Neuronal aggregations (aggregations of cell bodies) are called ___

nuclei

Aggregations of cell bodies in the peripheral nerves are called ___

ganglia

Supporting cells are called ___

glia

What are the function of glia?

provide nutrition to neurons and help with neurotransmission (they do not directly participate in neurotransmission)

Glial cells produce myelin which does what?

surround nerve fibers and provide insulation, protection and support

Three types of glial cells

1. Astrocytes

2. Oligodendrocytes

3. Microglia

Astrocytes

star-shaped and located in brain and spinal cord - support metabolic support for neurons, maintenance of blood brain barrier, repair injury to nervous system, regulate ion concentrations etc

Oligocenedrocytes

provide support to axons of the CNS by producing myelin sheath

Microglia

cells of immune origin and provide important immune functions of the CNS

Where the spinal cord run to?

the hindbrain to the lumbar veterbrae

What does the spinal cord contain?

1. fibre tracts (white matter)

2. cell bodies (gray matter)

Fibre tracts (white matter)

carry information from and to the brain

Cell bodies (gray matter)

interneurons or motor neurons that give rise to motor fibres

Sensory neurons are located in ___

dorsal root ganglion

Segments of the spinal cord are divided into

1. Cervical

2. Thoracic

3. Lumbar

4. Sacral

5. Caudal

Two enlargements along the length of the spinal cord

1. Cervicothoracic (between last three or four cervical spinal cord segments and the first two or three thoracic segments)

2. Lumbosacral area (between the three last lumbar spinal cord segments and the first two sacral segments)

The cervicothoracic and lumbosacral areas give rise to

brachial and lumbosacral plexus respectively

Three divisions of brain

1. Hindbrain

2. Midbrain

3. Forebrain

Hindbrain

rhombencephalon = Metencephalon + Myelencephalon

Midbrain

(Mesencephalon)

Forebrain

(Diencephalon+Telencephalon)

The Metencephalon is also

ventral (pons) and dorsal (cerebellum)

Cerebellum function

controls balance and is responsible for coordinating postural and locomotor activity

Thalamus function

relay and integration center of the brain

The telencephalon

formed by two cerebral hemispheres

The diencephalon

anterior-most portion of the brainstem

What are the three classifications of cranial nerves?

1. Nerves that are responsible for special senses

2. Nerves that provide innervation to head muscles

3. Nerves that provide innervation to structures to originate from the pharyngeal arch

Olfactory nerves (CN I)

responsible for olfaction (smell)

Optic nerves (CN II)

responsible for vision

Occulomotor nerves (CN III)

responsible for motor innervation to some of the muscles in the eyeball (contains both somatic and autonomic fibers)

Trochlear nerve (CN IV)

controls eye movement by supplying motor information to the superior oblique muscle

Trigeminal nerve (CN IV)

provides motor innervation to muscles of mandibular (lower jaw) origin

Abducent nerve (CN VI)

It innervates the lateral rectus and retractor bulbi (draws the eyeball into the socket) muscles of the eyeball

Facial nerve (CN VII)

provides innervation to muscles of facial expression

Vestibulocochlear nerve (CN VIII)

is responsible for the special senses related to vestibular (location and movement perception functions of the ear) and cochlear ( auditory part of the ear) function

Glossopharyngeal nerve (CN XI)

It provides sensory innervation to the mucosa of the tongue and the pharyngeal regions. It also provides some motor innervation to the pharyngeal region.

Vagus nerve (CN X)

It provides parasympathetic innervation to visceral organs in the thoracic and abdominal area. Most of the fibers in vagus provide afferent information from the viscera to the brain. The small motor component is responsible for providing innervation to the laryngeal muscle

Accessory nerve (CN XI)

The dorsal branch provides innervation to muscles in the neck (brachiocephalicus, omotransversarius, trapezius) and the ventral branch innervates sternocephalicus

Hypoglossal nerve (CN XII)

provides motor innervation to muscles of the tongue

Differences between somatic and autonomic nervous system

1. Somatic controls voluntary and involuntary functions while autonomic controls only involuntary functions

2. Somatic has only one neuron while autonomic has two

3. Somatic’s response by tissue is contraction while autonomic’s is excitation and inhibition

The cell bodies that regulate the autonomic nervous system are located in the ___

lateral horn of the spinal cord – an area called ‘autonomic nucleus’

Cell bodies located in the thoracolumbar segments of the spinal cord belong to the

sympathetic nervous system

Cell bodies associated with the parasympathetic nervous system are located in the

brain as well as the sacral segments of the spinal cord

Preganglionic fibers are

long

Postganglionic fibers are

short