Lecture 3

Nervous System

What are the 2 divisions of the nervous system

1. peripheral

2. central

What are the two divisions of the CNS?

1. brain

2. spinal cord

Function of the brain?

-interprets sensory input, controls thoughts, emotions and memory

ex. hot stove

functions of the spinal cord

-transmits signals between brain and the rest of the body

-coordinates movements and reflexes

3 Parts of Brain

-cerebrum

-cerebellum

-brainstem

what is the outermost surface of the brain?

cerebral cortex

what is in the cerebral cortex?

cell bodies of neurons, so gray matter

what is the folding of cerebral cortex and why?

highly folded to increases surface area → a lot of processing power

What is the pointer pointing to? singular and plural?

Gyrus/Gyri

-groups of gyri form lobes

What are the spaces in between the gyri called? singular/ plural? fxn? (2nd arrow)

sulcus/sulci
-fxn: divides gyri

What is the 3rd pointer pointing to? and what is it?

Fissure

-deep large sulci

what does fissure separate?

fissure separates the lobes of the brain

What are the major fissures/sulci of the brain

1. Sylvia fissure

2. central sulcus

3. Pareto-occipital sulcus

Sylvian Fissure - another name? placement?

also known as lateral sulcus

-travels front to back, horizontally

What does Sylvian fissure divide?

divides temporal lobe from frontal and parietal lobe

Central Sulcus- fxn? location?

divides the frontal and the parietal lobes

-sits vertically coming down to Sylvian fissure

Pareto-occipital sulcus, fxn?

only a small portion seen on lateral hemisphere

-separates parietal and occipital lobes

what is a landmark to find the parieto-occipital sulcus?

-parietal -occipital notch

-indentation on the dorsal surface of the brain

What sits in Anterior cranial fossa?

Frontal lobe

What sits in the Middle cranial fossa?

Temporal Lobe

What sits in the Posterior cranial fossa?

Cerebellum

what is the brainstem?

transition from cerebrum to spinal cord

Cell bodies in Brian vs spinal cord?

-it is reversed

-in brain found on the outside (gray matter)

-in spinal cord found on the inside (gray)

Where does switching of cell body orientation occur?

in the brainstem

Can you tell where cell bodies and axons are in the brainstem?

cant tell a clear difference, everything is everywhere

What does brainstem determine?

level of consciousness

ex are you in a coma or not

What does the brainstem control?

Autonomic processes

-breathing

-heart rate

-digestion

Parts of brainstem int the order from superior to inferior?

1. Thalmus

2. midbrain

3. pons

4. medulla oblongata

Thalmus

-uppermost aspect of brainstem

describe pons

has a “belly”

-Mickey Mouse ears

Medulla characteristic

-looks more like spinal cord bc transitions to it

-more round in nature

what does the midbrain rest against?

occipital bone

-specifically the clivus

where does midbrain sit?

at the level of Dorsum Sellae ( back of sella tursica)

-immediately posterior to sella tursica

Where does Pons sit?

rests on upper clivus

Where does Medulla sit?

-sits lower on clivus

-extends into foramen magnum

Characteristics of Cerebellum

-hindbrain

-sits in poster cranial fossa

-coordination of major motor action

How many cranial nerves are there?

12 pairs

-come from head

How many spinal nerves are there?

31 pairs

-ceom from spinal cord

Function of cranial nerves

-responsible for innervation of sensory and motor functions of the head and neck

-part of PNS

-nerves coming from brainstem

What are the Cranial Nerve exceptions and why?

CN I and II → not part of the peripheral nervous system

1. develop form central nervous tissue

2. act like CNS

3. myelinated by CNS

What is CN I?

olfactory bulb - in cribriform plate

what is CN II

optic nerve

What are the 2 neurons of the peripheral nervous system ?

1. Motor

2. Sensory

What are motor nerves

carries instructions from the CNS to muscles and glands (cause effect)

→ think E-fferent with E-ffect

another name for motor nerves

efferent

Another name for sensory nerves

Afferent

What are the sensory nerves responsible for

-infromation that come into central nervous system from skin, joints, etc

What is the pathway that burning your hand would take?

1. burn your skin

2. information travels via afferent nerve

3. synapses in spinal chord

4. repose travels via efferent nerve

5. innervates effector organ (ex. muscle)

What are the divisions of sensory neurons

1. somatic

2. visceral

What do Visceral neurons affect?

-internal organs

-sensations subconscious

ex. eating →stomach stretching → information to brain→ tells you youre not hungry/ stop eating

describe how somatic neurons work?

-something your aware of

ex. pain and temperature

-innervation to joints, muscles, legs,

ex. soreness

What are motor neurons divided into?

1. somatic

2. autonomic

What do autonomic motor neurons do? what type of control?

-involuntary → you’re not in control of

send signals form the CNS to smooth, cardiac muscle, and glands

What do somatic neurons do? what type of control?

-send signal to skeletal muscles

-under voluntary control

What are the divisions of the Autonomic nervous system

1. sympathetic

2. parasympathetic

how does your body respond in a sympathetic response? another name?

-fight or flight

-inc heart rate, inc blood pressure, dilated pupils, reduced digestion

How does your body respond in a parasympathetic response? Another name?

-rest and digest

• lower heart rate, constricted pupils, stimulate digestion and gland secretion

What is the nerve pathway for the autonomic nervous system described as?

two neuron pathway

where is the first neuron found in the nerve pathway of the Auto NS?

1. starts in the CNS - cell body in nucleus

   1. can be brain or spinal cord

   2. efferent pathway

What is a nucleus?

collection of cell bodies in CNS

-locations differ between sympathetic and parasympathetic

where is sympathetic nucleus found

thoracolumbar origin

T1-T2 cord

where are parasympathetic nucleus found?

-craniosacral origin

(cranial nuclei+sacral spinal cord)

• either in the cranial

• or in the sacral region of spinal cord (end of it)

what is the second step of the 2 neuron pathway?

-synapses in ganglion

-impulse goes from the pre-ganglionic neuron to post ganglionic neuron

what is a ganglion

collection of cell bodies outside of the CNS

where does the post ganglion synapse?

Post ganglion synapses on the effector organ

-ex cardiac muscle, smooth muscle, glands

What are the neurotransmitters that are preganglionic?

acetylcholine

what are neurotransmitters in the post-ganglionic neuron?

parasympathetic- ACh

sympathetic - norepinephrine

what is an example of parasympathetic pathway?

• pupil (size of iris) constriction

• rest and digest

where is innervation to iris constrictor?

-parasympathetic pathway

-first axon in cranial region

-pre ganglionic → Edninger - Westphal nucleus (in brainstem, specifically midbrain)

Edinger westphal - part of CN III - oculo-motor nerve (subnuclues) in the midbrain

-when parasympathetic axon comes out→ it travel with CN III through superior orbital fissure

-synapse with ganglion inside orbit → ciliary ganglion (in between optic nerve and muscle cone around eye)

• post ganglionic neurons leave ciliary body (short ciliary nerves) to go to iris constriction

How does CN III travel?

travels to eyes

through cavernous sinus

goes into orbit through superior orbital tissue

medial lecture

iris

steps of the sympathetic pathway?

1. first cell body is in thoracic or lumbar region of spinal cord

   1. cell body is in the lateral horn of spinal cord (T1, T2) ciliospinal center of budge

2. axon travels up via sympathetic chain of ganglion

3. ends/synapse at the uppermost ganglion = superior cervical ganglion

4. post ganglionic from superior cervical ganglion goes to eye, travels with internal carotid artery

5. internal carotid artery branches into ophthalmic artery

6. take 2 paths:

   1. short ciliary

      1. have gone through ciliary ganglion, NO synapse, goes on to eye

   2. long ciliary

      1. skip ciliary ganglion and travel forward→ travel on to eye

      2. * travel with ophthalmic nerve (V1 - trigeminal division 1)

Where does the sympathetic nerve signal start?

in thoracic-lumbar preganglionic cell body

in iris dilation what pathway would it take?

sympathetic pathway

-occurs in fight or flight

similarities between iris constriction and dilation pathways?

• 2 neuron pathway

  • first cell body starts in CNS

what does parasympathetic pathway do to eyes?

constrict

what does the sympathetic pathway do to eyes?

dilate

What is the sympathetic chain of ganglion

chain of ganglia - each have specific functions

-chain that travels the length of spinal chord

what are the sympathetic paths after the superior cervical ganglion?

1. short ciliary

   1. have gone through ciliary ganglion, NO synapse, goes on

2. long ciliary

   1. skip ciliary ganglion and travel forward→ travel

where is the 2nd synapse in the sympathetic pathway?

in superior cervical ganglion

what do we innervate in a sympathetic pathway in the eye

• muscles of Mueller

  • elevates the eyelid a small bit

• innervate iris

what happens if the sympathetic pathway is damaged

1. pupil is always constricted - miosis

2. eyelids droopy - ptosis

   1. Horner syndrome

      1. for carotid artery dissection

      2. affects all on the same side → so same eye

What are the systems for the blood supply to the brain?

1. anterior system

2. posterior system

Where does the anterior system supply blood?

supplies to frontal and parietal lobe

Where does the posterior system supply blood?

back of the brain

occipital lobe

what is another name for the posterior system

vertebrobasilar system

-up the verterbrals

what is another name for the anterior system

internal carotid

Pathway of anterior system

1. arises from common carotid artery

2. common carotid splits to internal branch and external branch

   1. internal branch supplies brain and eye

   2. external branch supplies structures of the surface of face

what are the 2 parts of the common carotid? and their pathways

1. left common carotid

   1. comes from the aorta of the heart

2. right common carotid

   1. from arch known as brachiocephalic on right side

   2. right common carotid

   3. right external and internal

pathway of internal carotid artery

goes into skull through carotid foramen → entrance to carotid canal (labyrinth that travels through petrous portion of temporal bone and comes out to nose) → on lateral aspect of sella tursica → along carotid groove → travels on top of lacerum

where is the cavernous sinus located?

envelope of dura

-inside dura is venous blood

-inside venous blood is the carotid artery traveling through it

what nerve pathway do you find in the cavernous sinus?

sympathetic pathway

where do pathways pick which pathway of long and short ciliary?

at the orbit

what are the branches the internal carotid artery gives off after leaving the cavernous sinus?

1. ophthalmic artery

2. anterior cerebral artery (ACA)

3. middle cerebral artery (MCA)

What does the ophthalmic artery supply?

orbital contents

What does the ACA supply?

medial aspects of brain

think mid spatial cut - like mohawk

found under the bones of the head

what does the Middle cerebral artery supply?

supplies lateral aspects of the brain

-branch out to the side

found through the brain

what is the pathway of the posterior carotid pathway on the right

1. brachiocephalic

2. arches into subclavian

3. reached the right vertebral

what is pathway of the posterior carotid pathway on the left?

1. subclavian artery

2. vertebral artery

how to vertebral arteries travel

the 2 vertebral arteries travel up vertically, through cervical spin, through opening called foramen transversarium

what happens to arteries at the base of the skull?

left and right vertebral arteries enter cranial cavity through foremen magnum and combine to form the basilar artery (1 artery)