Introduction to Neuroanatomy and Regional Anatomy

Nervous system

CNS - brain and spinal cord

PNS - cranial nerves and spinal nerves

Neuroplasticity

brain’s ability to reorganize

although in most cases the CNS does not regenerate, it can find ways to relearn…

Examples of neuroplasticity

spinal cord

part of CNS

connects the body’s peripheral nerve with the brain

injury: sensory and motor loss

• upper motor neurons: motor neurons with cell bodies in the cerebral cortex, brainstem or cerebellum (stroke,

• lower motor neurons: motor neurons with cell bodies in the anterior horn (spinal nerve is damage) thoracic outlet syndrome, Parkinson’s

complications from spinal cord injuries

motor → lack of mobility

+ sensory loss → inability to feel breakdown of skin

= formation of decubitus ulcers (can be fatal!)

peripheral nerves

located throughout the body and head

send to/from skin, tissues, bones, joints, glands, and internal organ

three kind of nerve cells: sensory, motor, autonomic

can usually regenerate

efferent vs afferent

efferent: moves from spinal cord to periphery

afferent: conducts signals from the periphery to the CNS

cerebrum

largest part of the brain

2 hemispheres connected by a large band of nerves (corpus collosum)

composed of:

• white matter - formed by axon

• grey matter: contains neuron cell bodies and dendrites

4 lobes

tightly folded to enable large amount of tissue to fit inside

gyrus and sulcus/fissure

frontal lobe

separated by parietal lobe by the central sulcus and from temporal lobe by lateral fissures

contains primary motor cortex

cognitive functions (judgement, reason, attention, awareness, abstract thinking, mood and aggression)

last area to fully myelinate'

brocas area

parietal lobe

lies posterior to frontal lobe behind central sulcus

separated from occipital lobe by parieto-occipital sulcus

separated from temporal lobe by the lateral fissure

primary somatosensory cortex (sensation

occipital lobe

located in back of brain under occipital bone

smallest cortical lobe

visual cortex

temporal lobe

located under the parietal lobe and anterior to the occipital bone

located under temporal bone

primary auditory cortex → decodes pitch and volume of sounds

Wernicke’s area

declarative memory function (factual memories)

limbic system

lies in the center of the brain

responsible for memory and emotion

structures include amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus

insula

“baby brain”

hidden under the frontal, parietal, and temporal lobes

can be seen by looking in the lateral fissure

awareness of sensation and emotion

basal ganglia

(you have 2!)

large subcortical structures made of grey matter

include the caudate nucleus, putamen, and globus pallidus

generates movement, thought and emotions

part of limbic system

diencephalon

contains two parts

1. thalamus: processes signals before they are sent to the cerebral cortex

2. hypothalamus: involved in control of HR, BP, digestion, water balance and controls the endocrine system; includes the paired mammillary glands

hypophysis (pituitary gland): located under the hypothalamus, part of the endocrine system

brainstem

composed of the midbrain, pons, and medulla oblongata

contains centers that control many basic life functions such as breathing and heart rate

contains most of cranial nerves

grey matter

composed of neuron cell bodies and dendrites

divided into regions known as horns

• dorsal

• ventral - motor neuron cell bodies

• lateral - autonomic neuron cell bodies

white matter

consists of myelinated axons

organized in regions called columns

chiari malformation

condition in which the base of the brain (usually the brainstem and/or cerebellum) sags through the foramen magnum

this can compress the brain and kill nerve cells

in severe cases, can lead to death if left untreated

meninges

protect the CNS from infection and physical trauma

three layers:

1. dura mater

2. arachnoid mater

3. pia mater

pia mater

thin and delicate

attaches to the surface of the brain and spinal cord

arachnoid mater

slightly thicker than the pia mater

transparent

arachnoid trabeculae connect the arachnoid mater to the pia mater

dura mater

thick and tough layer

forms a strong covering around the CNS, pia mater and arachnoid

lends with the connective tissue surrounding the spinal nerves

has many nerve ending → very sensitive to pain

2 sublayers: outer periosteal and inner meningeal layer

MAKE SURE TO LOOK AT CLINICAL CONNECTIONS

what are the four major arteries that supply blood to the brain?

2 internal carotid arteries

2 vertebral arteries

vertebral arteries

run alongside medulla oblongata

give off small branches for the spinal arteries

posterior inferior cerebellar artery branches off to supply blood to the cerebellum

near the brainstem, vertebral arteries merge to form the basilar artery

basilar artery

supplies blood to the pons and cerebellum (via superior cerebellar arteries and the anterior inferior cerebellar arteries)

circle of willis

ring of blood vessels

sits at the base of the brain

receives blood from the internal carotid arteries and the basilar artery (which is from vertebral arteries)

gives off three pairs of arteries:

1. anterior cerebral arteries

2. middle cerebral

3. posterior cerebral

what are the major sources of blood to the cerebrum?

circle of willis and cerebral arteries

anterior cerebral artery

run anteriorly between the frontal lobes in the longitudinal fissure

supply the anterior and inferior parts of the frontal lobe and part of the parietal lobes

posterior cerebral arteries

supply blood to the occipital lobe, thalamus and midbrain

cerebrovascular stroke / accident

stroke

disruption of blood flow to the brain

typically caused by an occluded (blocked) artery

can also be caused by bleeding in the brain from an artery rupture

hemorrhagic stroke vs ischemic stroke

hemorrhagic stroke: hemorrhaging/ blood leaks into brain tissue

ischemic: clot stops blood supply to an area of brain

venous drainage of the brain

small veins in brain → larger cerebral veins → dural sinuses → internal jugular veins → heart

vasculature of the spinal cord

one anterior spinal artery supplies the anterior 2/3 of the spinal cord

two smaller posterior arteries provide blood to the posterior 1/3

segmental arteries supply individual spinal segments

ventricles

4 interconnected cavities in the center of the brain

contain CSF

CSF can also circulate in the subarachnoid space and the spinal cord

each cerebral hemisphere contains one lateral ventricle

3rd ventricle: located central and connects the centrally located 4th ventricle via the cerebral aqueduct

cerebral spinal fluid

produced in all 4 ventricles by the ependymal cells in the choroid plexus

total volume: 140 ml

• 23 ml in ventricles

• 115 ml in the subarachnoid space

• it is produced continuously approx. 3 complete volumes per day

what are the functions of the CSF?

transport ions, nutrients, and hormones to neurons; removes waste

regulates the composition of extracellular fluids surround neurons and glial cells

provides a watery, protective cushion around the brain and spinal cord

WATCH THE CLINICAL CONNECTION VIDEO