Download ANATOMY LECTURE Unit 3

LECTURE 15 (Nervous System)
Today’s lecture is not on the exam. Last semester’s exam is at the library reserve desk.
NERVOUS SYSTEM (15 mins)
This is the most complex organ system in the body, but the function is straightforward.
1. Respond to changes in the internal and external environment (temperature, light,
pH, blood pressure, sugar). Changes in the environment are the stimulus, which
causes a response by the nervous system.
2. Coordinate body function: e.g. digestion: the stomach works with the intestine,
liver, pancreas, etc to digest foods. E.g. walking (complex movement): dozens of
muscles work together.
3. Higher Functions: memory, learning, thinking, behavior.
Three Parts of the Nervous System
1. Central Nervous System (CNS): brain and spinal cord.
2. Peripheral Nervous System (PNS): nerves of the body
3. Autonomic Nervous System (ANS): has parts of the CNS and PNS. Controls
autonomic function (blood pressure, digestion, etc).
a. Sympathetic division
b. Parasympathetic division
The nervous system is made up of more cell than any other system. For instance, the
brain has about a trillion cells. There are also a number of different cell types, the most
important is the neuron.
NEURON (main cell of the nervous system)
All neurons do three things:
1. Receive a signal. Can be any type of stimulus (change in environment, signal
from another neuron, etc).
2. Transmit a signal to another location. E.g. finger touching something 
signal to spinal cord or brain.
3. Stimulate another cell
a. Another neuron  transmit signal
b. Muscle  contraction
c. Gland  secretion
There are hundreds of different types of neurons, each one is specialized for a particular
task (e.g. sensory nerves receive and transmit sensory information, and there are several
different types of them, with receptors for touch, light, smell, etc). Motor neurons
transmit signals for muscle contraction, etc. They all share certain characteristics.
DENDRITES function to receive the signal
The CELL BODY is where the nucleus, ribosomes, and most organelles are located
AXON function is to transmit signals. Some cells have many axons, some have one,
some are short, and some are long.
SYNAPTIC KNOBS function to stimulate another cell.
Neurons may have a couple of synapses, or hundreds.
HOW NEURONS WORK (15 mins)
We’ll start with step 2: Transmitting a signal.
This takes place in the axon.
On the inside of an axon are lots of Potassium ions (+ charge)
On the outside of the axon are lots of Sodium ions (+ charge)
And the inside of the axon cell membrane is negatively charged.
In the axon membrane are two types of channels:
1. For Sodium (lets Na+ through)
2. For Potassium (lets K+ through)
When the Na+ channel open, what happens to the sodium? It diffuses into the cell. What
charge is sodium? Positive. Now the inside of the cell becomes positive.
Going form negative charge to positive charge = DEPOLARIZATION.
This causes the next sodium channel to open, then the next, etc  wave of
depolarization. Moves down length of the axon. Once this region has depolarized, the
sodium stops coming in, and the potassium leaves. What charge is potassium? Positive.
If the positive charge leaves, what happens to the cell? It becomes negative again. This
is REPOLARIZATION. A wave of repolarization follows a wave of depolarization.
These two events occur at the same time: ↑↓ ↑↓
↑↓
An ACTION POTENTIAL is a wave of depolarization followed by a wave of
repolarization. Action potentials move down the length of the axon.
An action potential is the signal transmitted.
No matter how long the axon is, the action potential is the same.
The action potential moves along until it reaches the synaptic knob.
PRESYNAPTIC NEURON  SYNAPTIC CLEFT  POST SYNAPTIC CELL
How does the signal go through the space? By a chemical transmission.
The synaptic knob has vesicles filled with a neurotransmitter that carries the signal.
Each type of neuron used particular types of neurotransmitters, so there are 100’s of types.
When the action potential reaches the synaptic knob, it causes exocytosis of the vesicle.
The vesicle fuses with the synaptic membrane, releases the neurotransmitter into the cleft.
The neurotransmitter binds to a sodium channel on the post synaptic membrane, opens it
up, sodium enters the cell, and triggers another action potential = stimulus.
In a gland cell, there is an exocytosis of whatever is in the gland. Lidocaine blocks the
sodium channels so it can’t get an action potential.
Neurons are only one type of cell; there are others; (25 mins)
GLIA (neuroglia) are supporting cells of the nervous system.
1. OLIGODENDROCYTES (“few branches”). They are found in the CNS, are very
large and complex cells. They form MYELIN SHEATHS. This sheath is a
covering around an axon to speed up the action potential.
A sheet of paper is like one of these cells, and it wraps itself around a pencil (axon), so
there are many layers. The myelin sheath is an electrical insulator. Between the
sheaths are nodes = NODES OF RANVIER.
The myelin sheaths prevent ions from flowing in or out, but they can do so at the Nodes
of Ranvier. The action potential jumps from node to node, speeding it up. An
unmyelinated axon can travel 1-20 meters per second. A myelinated axon can travel
20-100 meters per second. Why would you want any unmyelinated? They are not
necessary for things like digestion to start at 1/10 of a second rather than one second, or
start sweating in 1/20 of a second rather than 1 second. Walking and thinking are
things that need to be quick. An oligodendrocyte can wrap around one nerve cell in
many locations, and nerve cells can have many oligodendrocyes on their axons.
MULTIPLE SCLEROSIS is an autoimmune disease where the oligodendrocytes are
destroyed, interfering with the neuron functions in the CNS and brain. Starts to
manifest in late teens and early 20’s. It progresses to paralysis and sometimes death.
Maybe caused by a virus you were infected with in childhood. Not common in tropical
climates as it is in temperate climates. There are treatments, but no cure.
2. SCHWANN CELL is another cell that forms myelin sheaths, but in the PNS. Each
cell only forms one myelin sheath.
3. ASTROCYTE is another very large, complex cell, in the CNS. Its function is to
wrap around capillaries while it also is physically supporting and wrapping around
neurons.
a. Physically supports the neurons
b. Transmits materials from capillaries to neurons
c. Forms blood-brain barrier (BBB)
The BBB prevents a lot of certain types of materials from leaving the blood and
entering the brain (e.g. hormones, drugs). The continuous capillaries have leakage,
but are surrounded by astrocytes, so not everything can leak out. Certain antibiotics
can’t cross the BBB, so they can’t be used for brain infections.
4. MICROGLIA (one word, two errors!). These are not micro, nor are they glia.
They are macrophages, the same size as everywhere else in the body. They are
called micro because they are much smaller than real glia cells. They pick up
bacteria and dead cell, etc.
TERMINOLOGY (10 mins)
GREY MATTER: that portion of the CNS that is unmyelinated (cell bodies and dendrites)
WHITE MATTER: that portion of the CNS with myelin (axons)
NERVE: collection of axons in the PNS. No cell bodies, dendrites, or synapses; just axons.
TRACT: collection of axons in the CNS e.g. conveys information (axons) from the left to
the right side of the brain.
NUCLEUS IN CNS: a region of cell bodies within the CNS = grey matter (where synapses are)
SYNAPSES: Where information is processed
GANGLION: A collection of cell bodies in the PNS
NERVE PLEXUS: A network of nerves (nerves don’t run by themselves, they go in groups)
MOTOR NEURON: Nerves that leave the CNS to effect a muscle or gland
SENSORY NEURON: goes from body to CNS, carrying sensory information.
ASSOCIATION NEURON: One region of the CNS to another region of the CNS.
EXAM II
LECTURE 16 (Nervous System)
THE BRAIN (Use Model)
ANATOMICAL REGIONS (25 mins)
The brain is divided into parts, and is bilaterally symmetrical. In general, the left side
controls the right half of the body, and the right side of the brain controls the left half of
the body. The largest portion is the CEREBRUM, which makes up 80% of the brain.
It’s responsible for all the complex behaviors, conscious sensations, etc. The surface is
not smooth, it’s convoluted, called a GYRUS, and the indentations are a SULCUS. They
increase the surface area, and the surface is where the information processing is. The
cerebrum is made up of grey matter (cell bodies, dendrites, and axons). It is divided into
2 halves called CEREBRAL HEMISPHERES, which are separated by the
LONGITUDINAL FISSURE. Each hemisphere is divided into lobes, named for the
bones on top of them.
The FRONTAL LOBE and PARIETAL LOBE are separated by the CENTRAL
SULCUS. The TEMPORAL LOBE is between the parietal and temporal lobe,
separated by the LATERAL SULCUS. The OCCIPITAL LOBE does not have a real
border; it’s just a region. These are the anatomical areas, but the functional areas are
more important.
We know what the functions of the brain are by two ways. First, when there is a stroke
or injury, we see what area of the brain is damaged, and we can tell from the patient what
function has been affected. We also know by PET scans, which look at how much blood
flow there is to a particular region. For instance, they’ll tell to think about your
upcoming test so you feel anxious, and see where the blood flows in the brain. Move
your fingers, and see where the blood flow is in the brain. There’s a lot we don’t know.
FUNCTIONAL REGIONS: We already talked about the motor areas of the cerebral
cortex (the outer layer of cerebrum, has grey matter)
1. PRIMARY MOTOR CORTEX is in the frontal lobe (orange on model) in from
of the central sulcus, called the PRECENTRAL GYRUS. The primary motor
cortex contains primary motor neurons, called UPPER MOTOR NEURONS,
which extend down the spinal cord and synapse on LOWER MOTOR
NEURONS. Every muscle is controlled by motor neurons in this region. Some
muscles have more motor units than others (hands, eyes, etc). Look at this map
(overhead) of the precentral gyrus, and see that the large areas are the hand and
face, but the hips and back are small. Damage to the face area of the motor cortex
causes facial paralysis. There is a map of the body on both hemispheres.
2. PRE-MOTOR CORTEX is just anterior to the primary motor cortex.
a. Learned motor skills: these are preprogrammed skills, like when you know
how to type or swing a golf club. You practiced it so often, it’s now
automatic. When someone asks you how to spell a word, but you can’t do
it until you write it out, it’s because that memory is now a motor skill.
The same happens when you know how to tie your own shoelace or
necktie, but can’t tie another’s; it initially is learned by repetition. Then,
to do it later triggers a series of information which turns on those muscles
in the right order.
b. Motor association area (planning movement): This is when you plan to
reach for a new item. You have not rehearsed it, but you know to extend
your forearms, lift, etc. A signal is sent to the primary motor cortex to
turn on specific motor units to do that. Damage from a stroke= loose
function to that area, but you can compensate by using other muscles, and
re-learn that movement.
3. BASAL GANGLIA (actually basal nuclei) is a white, ball-shaped area deep in
the cerebrum. Its function is to coordinate movement, and it works closely with
the cerebellum, which is the second largest region of the brain, whose function is
to coordinate movement. When you plan a movement, like reaching for the milk
carton in the refrigerator, the primary motor cortex says for you to extend your
forearm, flex your fingers, and it calculates how much force you’ll need to lift that
weight. When it turns out the carton is much lighter than you figured, you
automatically jerk a little. That’s the cerebellum and the basal ganglia getting
signals to slow you down to lift more appropriately. Damage to the cerebellum
causes a tremor (intention tremor). When that person trys to reach for something,
they keep overshooting it. Damage to the basal ganglia is a resting tremor, seen
in Parkinson’s disease. When someone is drunk, they are uncoordinated because
alcohol affects the cerebellum. Having a dislocated jaw from yawning when
drunk is because the feedback is not getting to the cerebellum. The cerebellum is
not part of the cerebrum.
(15 mins)
SENSORY AREAS of the cerebral cortex. Somatic = touch (purple-grey area)
1. PRIMARY SOMATOSENSORY CORTEX is located in the postcentral gyrus,
in the parietal lobe. It receives signals for touch and pressure. In the sensory
map, you can see the face is the most sensitive, and the lips, teeth, and fingers.
The primary somatosensory cortex receives sensory neurons from the body,
synapses at the brainstem. Now the info has to be interpreted.
2. SOMATOSENSORY ASSOCIATION AREA is just posterior to the
postcentral gyrus. Its function is to interpret the signals. When I put my hand in
my pocket, I can find my keys by how they feel. This area interprets that.
3. PRIMARY VISUAL CORTEX is in the occipital lobe (green), receives signals
from the eye.
4. VISUAL ASSOCIATION AREA (yellow) interprets the signals. Damage here
causes a person to be able to see a chair in their way, move around it, but they can’t
identify the object as a chair. Some people with this damage can’t distinguish one
person from another because they can’t recognize their faces. For more information
on these types of brain damages, there’s a book called The Man Who Mistook his
Wife for a Hat. Alzheimer’s is not this; Alzheimer damage is everywhere.
5. PRIMARY AUDITORY CORTEX and the…
6. AUDITORY ASSOCIATION AREA (blue and red areas) are in the back of the
parietal lobe. They are also involved in language (blue area). This is where
language is formed. Language is hard-wired into humans. A group of deaf
children in South America were found to have created their own language, using
nouns, verbs, pronouns, adjectives, and everything, even though no one there
knew any sign language to teach them. There are certain strokes where the person
can’t use adjectives, but everything else is normal!
By the way, geniuses have the same size brain as everyone else; they are just more
efficient at forming synapses. We don’t use 10% of our brains, we use 100%.
We won’t discuss the taste region, there’s not much known about it, and we’ll talk about
smell in a few minutes.
HIGHER FUNCTIONS (control behavior and emotion) (15 mins)
PRE-FRONTAL LOBE involved in planning and judgment. How much time do you
need to be ready for the test? Damage here causes people to become docile and do what
they are told. 1930’s when people acted up, they did a pre-frontal lobotomy by going up
the eyelid, crack the cribiform plate, and stirring up the brain. Stopped in 1960’s; we do
it with drugs now (riddlin). There was a 16 year old rebel who shot himself in the head,
but went to far forward, and his personality improved! Riddlin suppresses CNS in
children, stimulates it in adults. In a criminal psych ward, an inmate with a lobotomy got
his hand caught in the electric door, and while his hand was dangling half off, a nurse
asked him if it hurt, and he just calmly said, “Yes, quite a lot.” No emotion.
Remember, when you kill a neuron, it does not regenerate; it’s gone forever.
MEMORY
We talked about motor memory. You can also have memory of events. This is
controlled by the HIPPOCAMPUS (“sea horse”). It’s located under the basal ganglia.
Function is to convert short term memory into long term memory.
When you have to look up a phone number, and then forget it 5 minutes later, that’s short
term memory, it’s the job of the hippocampus to convert it to long-term memory. This is
accomplished in two ways:
1. Repetition
2. Context
You can’t learn anything brand new; you have to add to what you already know, by
putting it into context. ANTEROGRADE AMNESIA is damage to the hippocampus;
they can’t remember anything new. Amnesia is not caused by a blow to the head; it has
to be damage deeper, like from a stroke. Also, a second blow doesn’t cure the first one!
Strokes and Alzheimer’s are most likely to cause amnesia. Nemo’s fish friend, Dorothy,
has this type of amnesia.
You can get around it by motor memory. Give an amnesiac a new puzzle; they’ll do it in
30 mins. The next day, they don’t recognize the puzzle, but they do it in 20 mins, the
next day in 10. Therefore, they are learning by motor memory. They can learn their
route from home to the market by repetition. But they can’t make a detour, and if
anything bumps them off track, they’ll be lost.
You can’t remember new things, so they need some context; they need to be associated
with something you are already familiar with. That’s why pneumonics are good. The
word “supinate” is a brand new word, but it sounds like “soup”, and its motion looks like
you’re holding a bowl of soup, so it’s easy now to remember.
All memories are created; there is no such thing as real memory. When the Challenger
shuttle exploded in the 1980’s, a freshman college professor told his students to write
down where they were and what they were doing when they heard about it. Four years
later, he asked them again. 65% answered the same way, but 35% remembered it
completely differently, but the students insisted they were right.
IMPLANTED MEMORY (15 mins)
Another college professor found all the freshmen students with older siblings at the
college, and he told the older siblings to tell this story to their younger siblings: “When
you were 5, we went to a fancy restaurant to celebrate mom’s birthday, and you spilled
something on her dress and you were really embarrassed.” A few weeks later, the
professor asked the freshmen to write down a story about anything embarrassing that
happened to them when they were five, and to include all the details they remembered.
The freshmen recounted the fake story as though it was real because they thought they
remembered it. They also included details that they were not told, such as the name of
the restaurant, the color of the dress, and what was spilled. The freshmen filled in the
story to make a complete memory.
The prefrontal lobe and the hippocampus are part of a system of structures in the brain
(overhead picture of limbic area in green). The LIMBIC SYSTEM also includes
olfactory lobes. Therefore, memory, emotion, and smell are linked. Crayolas are created
today with the same scent because it reminds people of their happy times in childhood.
Why is the brain formed so that smell and emotions are tied together? Because
pheromones are tied to emotions and behavior, so they need the link.
Another part of the limbic system is the HYPOTHALAMUS. This is the most
important region of the brain (small orange triangle deep in the brain). This small area
controls all of the autonomic functions like heart and breathing rate, glucose and hormone
levels, digestion, sweating. This area is part of the limbic system, so that’s why a painful
memory can increase blood pressure.
The THALAMUS (the rest of the orange area) functions to sort out all the sensory
information. It compares the input and determines what information is worth sending to
the cortex. Your body ignores most sensory information. Up until now, have you
noticed the sound of the air conditioner? It’s not important, so it goes unnoticed. This
area also compares information from the right and left eyes for stereoscopic vision, and
the right and left ear to determine direction of sound.
Above the thalamus is the EPITHALAMUS, called the PINEAL GLAND, which gets
the sensory information from the eyes and determines the circadian rhythm, or the
biological clock. It detects the number of hours of light and dark, and sets the 24 hour
clock. When you get jet lag, it’s because the information it gets doesn’t match with
where you are. You can help yourself get over jet lag by being outdoors in the daylight
and being indoors at night, and the pineal gland with reset the clock.
Farther down the brain stem is the MIDBRAIN. This is important for visual and audio
reflexes. Shine a light in the eye, and the pupil constricts = visual. Loud noise (BANG!)
causing a startle, is the audio reflex.
Farther down the brainstem, the motor nerves are for breathing regulation, and then there
is the MEDULLA. Within this area is control of consciousness. Damage here causes
coma. Swelling from an injury causes pressure, which can damage this area, which can
cause a coma.
Concussions cause a decrease in blood pressure and nausea; need an MRI
Boxers who are knocked out can recover, but repeated knock-outs can cause permanent
brain damage.
LECTURE 17 (Nervous System)
SPINAL CORD (10 mins)
Really, this is just a continuation of the brain. The definition of where it begins is the
FORAMEN MAGNUM. It goes to L1.
Try to find it on yourself. How do you find it? It’s right at the costal margin, which is
pretty high up. In infants, it ends at L4-5, because it doesn’t grow as fast as the rest of
the body. Beyond that are bundles of nerves called the CAUDA EQUINA (“Horse’s
tail”), which exit through the intervertebral foramina. Nerves are named L1, C5, S2, etc.
The cervical nerves are names for the vertebrae below them, and the other nerves are
named for the vertebra above them. Therefore, nerve C5 is between C4 and C5. The
nerve C10 is between T10 and T11. There is a nerve C8.
CROSS SECTION OF THE SPINAL CORD (20 mins)
With CENTRAL CANAL, GREY MATTER, WHITE MATTER, POSTERIOR
MEDIAN SULCUS, ANTERIOR MEDIAN FISSURE, POSTERIOR HORN,
ANTERIOR HORN, POSTERIOR ROOT, POSTERIOR ROOT GANGLION,
ANTERIOR ROOT, and SPINAL NERVE.
SENSORY NEURONS come in through the posterior root, their cell body is in the
posterior root ganglion (group of cell bodies in peripheral nervous system), and its axon
goes into the posterior horn and synapses in the grey matter. It also sends a branch to an
area of the white matter called the DORSAL COLUMN PATHWAY, which goes into
the brain (thalamus).
LOWER MOTOR NEURONS have their cell body in the anterior horn, their axon goes
out the anterior root, and synapses in a muscle.
ASSOCIATION NEURONS have their cell body in the grey matter (receives signal
from the sensory neuron) and it synapses on the cell body of the motor neuron.
These three nerves together for the SIMPLE REFLEX ARC. They process information
without the brain. So if you touch a hot stove, the sensory input comes into the spinal
cord, the association neurons send the information to the lower motor neurons, the
muscle contracts, and you take your hand off the stove before your brain even knows it.
So this is a simple reflex behavior, involving three nerves, and no brain involvement.
Reflexes are automatic events.
Now signal has to go to the brain via a TRACT (a bundle of axons). So the sensory axon
sends a branch to the brain via the thalamus. SENSORY TOUCH  SPINAL NERVE
 POSTERIOR ROOT GANGLION  POSTERIOR ROOT  POSTERIOR
HORN/DORSAL COLUMN PATHWAY  THALAMUS  POST CENTRAL
GYRUS in the primary somatosensory cortex.
Within the muscles are sensors that measure the amount of force and movement, called
PROPRIOCEPTION neurons (sensory). The cell body is in the posterior root ganglion,
and it enters the posterior root and synapses in an area of white matter called the
SPINOCEREBELLAR tract, since the cerebellum is responsible for balance and
position.
Muscles are under voluntary control also, so there are nerves that come from the
PRECENTRAL area of the brain to the CEREBROSPINAL TRACT (motor nerves).
Other things control movement:
VESTIBULOSPINAL TRACT (motor nerves) receives signal from LMN, cell body is
in anterior portion of white matter, and goes to the brain. It is for balance, especially the
legs. This is not voluntary control.
These are just two sensory and two motor tracts. There are many more that fill up this
area (overhead of tracts for temperature, touch, pain, etc).
(10 mins)
MENINGES (Singular = menes)
These are tissues that cover the entire CNS. They are three layers that serve to protect
and cushion the brain.
DURA MATER (“Tough mother”) is very dense regular connective tissue. It forms the
outer layer of the meninges, and consists of two layers. Under the skull is the first layer
of dura mater, called the PERIOSTEUM. Just under this is the second layer, called the
dura. There are these two layers everywhere except around the spinal cord, where it’s
just one layer, the dura; no periosteum. The dura mater follows the convolutions of the
brain. Between the dural and periosteal layers of the dura mater are DURAL SINUSES,
which are filled with venous blood which is drained from the brain.
ARACHNOID MATER is not nearly as dense. It is web-like, and extends into the
SUBARACHNOID SPACE, filled with CEREBRAL SPINAL FLUID (CSF).
In the spinal cord (overhead), between L3 and L4, a doctor can inject there and be above
the dura mater, so only the nerves are affected. What is that called? An epidural.
The dura and arachnoid mater both have lots of blood vessels, which might rupture in an
injury, called a SUBDURAL or SUBARACHNOID HEMORRHAGE, which is
potentially fatal. Blood accumulates and squeezes the brain. Tx = drill a hole.
VENTRICLES OF THE BRAIN (20 mins)
The brain and spinal cord are hollow, filled with CSF = ventricles (blue areas on
overhead anterior and lateral views). They are extensive. The names are simple.
1. LATERAL VENTRICLE is the larges, extends throughout the cerebrum.
2. THIRD VENTRICLE
3. INTERVENTRICULAR FORAMEN: connects the third and lateral ventricles.
4. FOURTH VENTRICLE: connecting the 3rd and 4th ventricles is a tube called the
CEREBRAL AQUEDUCT. The 4th ventricle is continuous with the central
canal of the spinal cord, and also with the subarachnoid space. The ventricles and
subarachnoid space are filled with CSF.
There is a total of 150ml of CSF.
The functions are as follows:
1. Allows the brain to float. The brain has the consistency of Jell-O, and weighs
three pounds. Its weight would crush the inferior structures if it didn’t float.
2. It cushions. In sudden movement, like riding a bike into a tree, and hitting the
head on the tree, the brain hits inside the skull in the front, and then in recoil it
hits the back of the skull = closed head injury, not necessarily with a fracture.
3. Acts as the lymphatic system of the brain (it doesn’t have one).
What is CSF?
It is similar to plasma because it is derived from plasma. It is made in the 3rd and 4th
ventricles by the CHOROID PLEXUS (overhead). There are fenestrated capillaries
there. The fluid spreads into the subarachnoid space. 800ml of CSF is made per day, but
there is actually only 150ml because the extra is absorbed in the dural sinus through the
arachnoid villa, which are valves that release the CSF back into the blood.
HYDROCEPHALUS
This is usually congenital, caused by a blockage of the cerebral aqueduct. So the CSF is
made but can’t leave, and the brain gets expanded. The skull bones in a newborn can
expand. Treatment is to put in a tube to drain it. Hydrocephaly in adults can be caused
by a tumor, and since the skull no longer expands, it’s very dangerous.
MENINGITIS
This is when the meninges become infected. Can be caused from virus (not that bad) or
bacteria (can be fatal). The main symptom is a headache, so when this occurs in an
infant, they can’t say where they hurt. So when an infant presents with a high fever of
104˚ with no other symptoms, they will usually test for meningitis, because if they miss
it, it’s fatal. The test is a SPINAL TAP, where a needle is inserted between L4 and L5
because that is below the level of the spinal cord. They draw the CSF to look at. It it’s
cloudy or bloody, it’s usually meningitis. Untreated meningitis can lead to this next one:
ENCEPHALITIS
This is infection of the brain. It can be caused by mosquito-borne illnesses, or bacteria.
Why is infection of the brain so dangerous? It’s very dangerous because the swelling
crushes the brain. Any injury may lead to brain swelling. Treatment is to remove a piece
of the skull bone to allow the swelling.
LECTURE 18 (Nervous System)
PERIPHERAL NERVOUS SYSTEM
Structure of a nerve (15 mins)
Nerves are surrounded by a dense fibrous connective tissue = EPINEURIUM, which
protects the nerve. It extends into the nerve and separates it into parts =
PERINEURIUM (modified dense fibrous connective tissue). Within here are individual
axons, some myelinated, others are not = FASCICLES. Surrounding the axons is the
ENDONEURIUM, which also contains blood vessels, etc.
Cut nerves
If a small nerve is cut, it will regenerate because where are the cell bodies? In the
posterior root ganglion (sensory) or anterior horn (motor). Since the cell body is about a
meter away, axons can regrow. Large nerves are harder to regrow, but you can still stitch
the ends together at the epineurium and perineurium, and you may get healing.
Pinched nerves
When a nerve gets pinched (e.g. herniated disc), it damages the nerve by interfering with
its action potential, causing weakness, pain, or paralysis.
Blood supply interfered with
When a body part “falls asleep”, the region has become ischemic, impairing the action
potential of the nerves. Unlike the CNS, when blood is restored, the nerves recover.
Damage to the CNS tends to be permanent, but damage to the PNS tends to heal.
SENSORY NERVES
These come out of the spinal cord and go to specific regions of the body. Each region is
innervated by spinal nerves (overhead). For example, nerve C6 innervates region C6 of
the DERMATOME. It’s important to know these dermatome regions (not for this
class), especially physical therapists and nurses. If a patient has a shooting pain down the
posterior thigh and leg, what nerve is pinched? S2. Numbness in pinky and ring finger is
what nerve? C8. If a workman’s comp patient comes in saying his whole hand is numb,
no other symptoms, you know he’s lying because the nerves don’t run that way. They
also don’t run transversely across the body; they are on one side or the other.
AUTONOMIC NERVOUS SYSTEM (35 mins)
We don’t have voluntary control over these. This involved digestion, blood flow,
urination, defecation, glandular secretion. This system differs from the rest of the
peripheral nervous system in that there are two motor neurons in the periphery. The
nerve comes from the spinal cord and synapses on the cell body of another neuron, which
then synapses on the target (gland, blood vessel, etc). The area where the two nerves
come together is the AUTONOMIC GANGLIA. The first nerve is the PREGANGLIONIC NEURON. The second nerve is the POST-GANGLIONIC
NEURON.
The autonomic nervous system has two divisions: sympathetic and parasympathetic.
SYMPATHETIC DIVISION
This is involved in ↑heart rate, ↑metabolic activity, dilation of bronchioles, control of
blood flow to the skin, and sweating. E.g. when running, ↑heart rate = sympathetic.
When hot  sweat = sympathetic. The term “Fight or Flight” is inaccurate; it refers to
the ↑ heart rate, etc, but the sympathetic division is also active when relaxing on a nice
beach with a cool drink on a hot day, because you’re sweating.
ANATOMY OF THE SYMPATHETIC DIVISION
This is also known as the THORACOLUMBAR DIVISION, meaning that the neurons
exit the spinal cord at the thorax and lumbar regions. Most pre-ganglionic neurons in the
sympathetic division are fairly short, and they synapse quickly on a ganglia. All these
ganglia together are the SYMPATHETIC TRUNK (CHAIN) GANGLIA. There are
about 22-24 on each side. There are also nerves that connect the ganglia to each other.
The POST-GANGLIONIC NERVE AXONS are very long, and go to the target organs.
Some pre-ganglionic ganglia bypass the chain ganglia and go directly to the abdomen.
These are called SPLANCHNIC NERVES (run from spinal cord to abdomen). They
create a group of ganglia in the abdomen called the SOLAR PLEXUS (“sun”).
PARASYMPATHETIC DIVISION
The function of this division is often antagonistic (opposite) of the sympathetic, but
actually, they work together. The parasympathetic ↓heart rate, constricts bronchioles,
activates digestive system, and causes salivation, urination, and defecation. When you
are lounging on the beach, the heart rate decreases (parasympathetic), but the sweat
increases (sympathetic). The parasympathetic system has no innervation to the skin;
therefore there are no effects to glands or skin blood flow.
Another name for the parasympathetic nervous system is the CRANIOSACRAL
DIVISION. Nerves come out of either the brain or the sacral region of the spinal cord.
The preganglionic axons are long, and the postganglionic axons are short. The ganglia
are either next to or inside of the target organs.
VISCERAL (“organ”) SENSES
Internal organs also have sensory nerves that tell you when you have eaten enough or
your bladder is full. Not all organs have sensory nerves, for instance, you can’t feel when
you have high blood pressure. You can also have visceral reflexes, which trigger the
parasympathetic system to contract the bladder when full, etc. Reflexes are hard to
localize. Pain in an organ may not be where the organ is. Heart pain usually manifests in
the left side of chest, the left shoulder, arm, but not the heart. This is REFERRED
PAIN. Pain in the lungs usually shows up as neck pain. These areas of referred pain are
important to know, but not for this class.
The autonomic nervous system is controlled by the hypothalamus in the limbic system.
CRANIAL NERVES (p. 47 in the manual)
This section is on every type of board exam.
These nerves come out of the brain directly. There are 12 pairs. You have to memorize
this whole sheet. They are numbered with Roman numerals and names, and functions.
I’ll skip over the obvious ones and cover just a few, but you need to know them all.
III Occulomotor Nerve: this controls the extrinsic muscles of the eye (that move the
eyeball). They also have parasympathetic innervation in the iris (pupil) and cilliary
(controls the lens).
V Trigeminal Nerve: This is the main sensory nerve of the face. It has three parts.
When a dentist numbs the lower teeth, he injects a branch of the mandibular nerve. For
the upper teeth, he injects the maxillary branch. Problems with CN-5 are called
TRIGEMINAL NEURALGIA, which is excruciating pain in the face from nerve
inflammation. These nerves all go through those tiny foramina you had to learn, and
swelling of the nerve causes pinching in the foramina.
VII Facial Nerve: This innervates the muscles of facial expression. It also supplies
parasympathetic innervation to the lacrimal, nasal, and most salivary glands. BELL’S
PALSY is damage of the facial nerve causing paralysis on one side. The nerves swell
from infection or something, but only the motor nerves are involved, not the sensory, so
it’s painless. Needs to be distinguished from a stroke.
X Vagus Nerve (vagrant = “wanders”). This is the most important cranial nerve because
it innervates all of the organs in the thoracic and abdominal cavities: heart, lungs, GI
tract, etc, with parasympathetic innervation.
Need to know all of the cranial nerves. Hint: use the first letter of each nerve to make a
sentence: “OOO To Touch and Feel a Virgin Girl’s Vagina, Ah, Heavenly”.
(25 mins)
SENSORY ORGANS are structures that convey senses
SOMATIC SENSES: Touch, heat, cold, pressure, pain.
You have special sensory neurons throughout the SKIN, the five types mentioned above.
They go to the postcentral gyrus via the thalamus.
Another set of sense organs:
PROPRIOCEPTORS are found in the muscles, joints, and tendons. They measure the
amount of movement, force, and position of the body. They send information to the
cerebellum. That’s how you know your legs are crossed before you stand up.
SPECIAL SENSES: Smell, taste, vision, hearing, balance.
OLFACTORY SENSE (smell)
Olfactory receptors are CHEMORECEPTORS; a special type of neuron which senses
particular chemicals and triggers an action potential. Chemoreceptors are at the roof of
the nasal cavity. There are hundreds of thousands of types, and they can smell a wide
variety of substances. They are extremely sensitive, and can detect parts per billion, as in
the scent of natural gas…just a few molecules! The olfactory nerve goes through the
cribiform plate to the OLFACTORY BULB (one of the shortest nerves in the body) and
into the limbic system.
GUSTATORY SENSE (taste)
Sensed on taste buds, which are located mostly on the tongue surface, but are also on the
palate, pharynx, and a few on the lips. Taste buds have specialized cells, which increase
surface area and have chemoreceptors. They are surrounded by support cells (like glia).
They synapse on sensory neurons, which go to the facial nerve. Taste buds are the only
parts of the nervous system that can regenerate completely.
How many different tastes are there? Dozens. Salt, sweet, bitter, and sour are only a
few. Where are they located on the tongue? All tastes are located all over the tongue.
The picture in the book was drawn 120 years ago by an anatomist that his drawing was
not right; he just wanted to use it as a starting point for further experimentation.
Taste appreciation is also involved in texture (a mealy apple is not as good), temperature
(cold pizza tastes different than warm), and smell (perfume or cigarette smoke clog the
senses and decrease taste). There are dozens of taste receptors, hundreds of thousands of
smell receptors, so the subtly of taste is from smell.
Foods people like are in opposite proportion to the numbers of taste receptors for that.
People that love sweets have FEWER taste receptors for sweets, so they crave more taste
of sweet things. If you dislike something, it’s because you have lots of receptors for it.
Also, as you get older, you become less tolerant of sweets and more tolerant of bitter
tastes (like beer and coffee).
LECTURE 19 (Nervous System)
THE EYE (15 mins)
Structures Surrounding the Eye
The eye is in the orbit of the skull for protection.
Within the orbit are 6 extrinsic eye muscles, which move the eye.
There are 3 cranial nerves: Ocular, Trochlear, and Abducens.
Eyelids are PALPEBRA, and eyelashes are CILIA.
People of Asian descent have an EPICANTHIC FOLD in the upper eyelid; no
functional difference.
Around the eyeball are glands,
GLANDS OF THE EYE
1. LACRIMAL GLANDS are the largest set. They are on the superior lateral eyelid
(overhead) and they produce tears, which go to the LACRIMAL DUCT. The function is
to moisten and lubricate the eye surface, and it has enzymes to kill bacteria (which thrive
in warm, moist conditions).
2. LACRIMAL CARUNCLE (“little meat”) is the spot on the medial corner of the eye.
It makes an oily secretion like a sebaceous gland. The function is to lubricate the eye for
the eyelids. When the secretion dries, it is called “sand” in the eyes.
3. TARSAL GLANDS are sebaceous glands on the inside of the eyelid, and produce sebum,
which is an oil to lubricate the eyeball. The tarsal glands and the lacrimal caruncle make a
waterproof surface so the eye won’t dry out. When clogged = CHALAZION
4. CILLIARY SEBACEOUS GLANDS go to only the cilia. When clogged = STY.
THE EYEBALL (20 mins)
1. CONJUNCTIVA is like a Saran Wrap covering around the eye and under the eyelids.
It’s made of stratified columnar epithelium (the first time in the body we’ve seen this
tissue). It also has lots of goblet cells to secrete moisture for those areas. Deep to the
epithelium is loose connective tissue with lost of small blood vessels, which are not seen
unless the conjunctiva becomes inflamed: Blood-shot eyes from being tired, or PINK
EYE, which is CONJUNCTIVITIS (from bacteria, very contagious).
2. FIBROUS TUNIC is the next layer, and has 2 parts:
A. SCLERA is the white of the eye, made of dense irregular connective tissue.
It is continuous with the dura mater of the brain. The eye is part of the brain. The
sclera protects the eye.
B. CORNEA is clear, and avascular. It has lots of pain receptors, so a scratched
cornea is very painful. Its function is to be the main focuser of light for the eye.
If damaged, need a corneal transplant, which is easy because it is avascular, so
there is no need to find a donor match.
3. VASCULAR TUNIC is deep to the fibrous tunic. It has several structures.
A. CHOROID has lots of blood vessels and pigment. The function of the
pigment is to make sure light does not enter from the sides. The blood vessels
provide blood supply to the other layers.
B. CILLIARY MUSCLES surround the lens.
C. SUSPENSORY LIGAMENTS hold the lens in place.
D. LENS functions to bind to the focuser. It changes shape to allow you to
distinguish close from far. The lens changes shape by the cilliary muscles pulling
on the suspensory ligaments.
When you are looking far away, the cilliary muscles are relaxed, the lens is
stretched into a wide circle, and the suspensory ligaments are tight. When you
look up close, the cilliary muscle contracts and gets smaller, to the ligaments
relax. Constantly looking close puts strain on the cilliary muscles = EYE
STRAIN.
PROBLEMS WITH THE LENS (20 Mins)
With age, the lens loses flexibility, and is less likely to round up. It stays in the position
for seeing far, so there is trouble focusing on things that are near = PRESBYOPIA (“old
eyes”). Occurs around age 45-50.
Dark spots in the lens which can completely cloud the eye = CATARACTS. Treatment
is to remove the lens and replace it with a plastic one (which is not flexible either). If the
lens yellows, you can’t see the color blue. After surgery, can see blue again.
IRIS (the colored part of the eye)
If there is lots of pigment, eye is brown; a medium amount = green, small amount = blue,
no pigment = pink (albino). The function is to constrict or dilate the pupil (opening) to
allow light in.
RETINA
On top of the CHOROID layer is the PIGMENT LAYER, which functions to absorb
stray light in the eyeball that comes through the pupil and the lens. You don’t want light
to bounce around inside there.
There are also PHOTORECEPTORS, which are sensors for light. Two types:
1. CONES (red, green, and blue) they have less light sensitivity (poor at night) but see
colors well.
2. RODS (chartreuse = yellowish green) have more light sensitivity (can see well at
night) but does not see colors well.
When you want details, focus the light on the macula, because there are a lot of cones
there. The other layers contain a mixture of both.
Above the photoreceptors are layers of neurons = NERVOUS LAYERS. They synapse
on cells, and send their axons through the optic nerve.
On top of the macula is a VASCULAR LAYER which also goes out to the optic nerves.
The region where the optic nerve and blood vessels goes in and out of the eye has no
photoreceptors = BLIND SPOT. Hold your hands out at 45° and that’s the size of the
blind spot. You can still see your hands because the other eye sees it. Close one eye and
you’ll find the blind spot.
The light takes a path through the blood vessels, through the photoreceptors, so this is the
only place in the body where you can see blood vessels directly. The doctor can diagnose
hypertension. On a clear, bright day, look at the blue sky and you can see the shadow of
your own blood vessels on the photoreceptors as criss-cross lines in field of vision. The
little moving dots are your blood cells.
PROBLEMS WITH VISION (20 mins)
FLOATERS are when a capillary breaks and cells break off. Floaters don’t actually
move, the eye just tries to track them.
MACULAR DEGENERATION
The size of the macula is the size of the printed letter “O” in 14 pt font. When the macula
degenerates, you lose a lot of sight. This is the most common cause of blindness. There
are two forms:
1. WET MACULAR DEGENERATION (15% of cases) due to bleeding from choroid,
and scar tissue forms. As it separates from the choroid, the retina does not get enough
oxygen, and the cells die.
2. DRY MACULAR DEGENERATION (85% of cases) pigment deposits come up
into the cone area, decreasing acuity. This is very common with age; usually just a small
amount. When a large amount deposits, causes blindness.
Macular degeneration allows vision in the periphery, but they can’t read or drive.
RETINAL DETACHMENT
The retina separates from the underlying choroid. Looses oxygen, cells die. Usually
caused by an injury like a baseball, punch, or airbag to the eye. Treatment is lasering to
spot-weld it back. Manifests as a shimmering light. Needs immediate treatment. Those
who are most vulnerable are those who are nearsighted.
HYPEROPIA (far-sighted) eyes are too short; MYOPIA (nearsighted)
Normal eyes are perfect spheres.
Myopic eyes are elongated (overhead projector is in focus, but move it backward, gets
fuzzy. Even badly nearsighted eyes are only 1mm from normal. Treatments are glasses
or Lasix, which is laser surgery on cornea, when it’s shaved so it focuses light farther
back to reach the retina.
ASTIGMATISM
Cornea has an irregular shape. Part of the field of view is out of focus.
They eyeball changes shape until age 24.
NOTES
If a child is blind until age 4-5, and then you restore the sight, he will still be blind
because the brain doesn’t form properly. With kids who have astigmatism or weak eye
muscles, one eye stops seeing (or sees double). The thalamus in the brain will shut off all
the signals from the bad eye.
AMBLYOPIA = Lazy Eye. In a child, one eye will tract and focus, the other won’t. If
untreated in children, eventual blindness in weak eye because the brain will shut down in
the occipital lobe. Treatment is to patch the good eye to force the bad eye to make the
connections, or a surgery to weaken the muscle to make the strong side just as weak.
INTERNAL STRUCTURES OF THE EYE (Overhead of sagittal section)
There are two cavities
ANTERIOR CAVITY is anterior to the lens, and is filled with AQUEOUS HUMOR,
similar to plasma, supplies nutrients to the cornea and lens. Secreted by Cilliary Body. It
is absorbed back into the venous system via the venous sinuses = SCLERAL VENOUS
SINUS. Too much aqueous humor  pressure on the anterior chamber and retina 
GLAUCOMA, the leading cause of blindness. There is a test for how much pressure
there is here by seeing how easily the cornea is deformed, either with air or direct
pressure. How many of you have had this test?
POSTERIOR CAVITY is filled with VITREOUS HUMOR, which is jelly-like, and
helps give shape to the eyeball. It leaks out from a cut, you’ll go blind because the body
can’t replace it.
LECTURE 20 (Nervous System: Ear, and Endocrine System)
Don’t forget your lecture exam is next week!
THE EAR (model) (25 mins)
OUTER EAR consists of the PINNA and the EXTERNAL AUDITORY CANAL.
The pinna funnels sound in. If you cup your hands to your ears (do it now), you’ll notice
the sound of my voice is louder.
MIDDLE EAR is an air filled space (overhead) with structures. The TYMPANIC
MEMBRANE (ear drum) vibrates in response to sound. Attached to it are 3 bones: The
MALLEUS (hammer), INCUS (anvil), and the STAPES (stirrup) are the smallest bones
in the body. Together, they are only one inch long. Their function is to amplify sound
vibrations. The malleus vibrates the incus, which vibrates the stapes. These are lever
systems. The middle ear is open to the nasopharynx by way of the AUDITORY TUBE,
which is only the thickness of a pencil lead. If this tube is closed, the ears feel plugged
up. It is needed to equalize the pressure of the middle ear and the outside air to get the
vibrations of the bones. Tubes are put in the tympanic membrane to drain fluids in kids.
INNER EAR exists within the temporal bone (petrious portion). It is a complex
structure. It is located in a bony cavity called the BONY LABYRINTH (“maze”). It is
filled with a fluid called PERILYMPH, which is similar to CSF.
Within the bony labyrinth is the MEMBRANOUS LABYRINTH, filled with
ENDOLYMPH. One of the membranous structures is the COCHLEA (“snail shell”).
Instead of drawing the cochlea curled up, I’m going to draw it laying out straight. There
Are HAIR CELLS which touch the TECTORAL MEMBRANE. The stapes is attached
to the OVAL WINDOW, and vibrations cause the perilymph to vibrate.
Low frequencies (like the longer strings of a piano) cause a response in the tip of the
cochlea, and high frequencies cause a response at the larger end. How do the hair cells
vibrate? The perilymph is vibrating, and the hair cells are inside of the endolymph.
Therefore, the vibration only affects one side of the hair cell, leaving the other free to
move with the vibration, like holding a piece of paper only on one edge. The hair cells
are connected to CN8, the VESTIBULAR COCHLEAR NERVE, which takes the
signals to the brain.
VESTIBULAR SYSTEM
This system regulates balance. Within the inner ear is the cochlea, and the rest of the
inner ear has more parts.
SEMI-CIRCULAR CANALS (3) determine movement in three planes. Within each
canal is endolymph and hair cells, which connect to nerves that go to the cerebellum.
When you move in one direction, like sliding across the room, the fluid sloshes like a cup
of coffee, and it makes the hair cells move. Attached to the semi-circular canals are to
joined structures called the UTRICLE and the SACCULE. These also contain hair cells
and endolymph. Within the endolymph here are OTOLITHS (“ear rocks”) which are
calcium deposits. When you stand perfectly upright, these otoliths fall directly down and
bend the hairs on the lower cells. When you tip your head to the side, they will stimulate
the hairs on the opposite side. These stimulate the nerves to tell you what position your
head is in.
Inflammation of the semi-circular canals give you a sense of motion when you’re not
moving = VERTIGO (dizziness) or LABYRINTHITIS. This can be debilitating.
Sometimes only one canal is affected, so you only get dizzy if you turn your head one
way.
ENDOCRINE SYSTEM (15 mins)
The endocrine system is all the organs of the body that are endocrine glands.
An endocrine gland secretes endocrine hormones.
Endocrine hormones are hormones that are secreted into the blood.
Hormones are substances that are secreted by one group of cells that affects the
physiology of another group of cells (organs). The endocrine system is controlled by the
pituitary gland and the hypothalamus.
HYPOTHALAMUS
This is located at the base of the brain (overhead). It is part of the limbic system, which
controls the autonomic nervous system and the endocrine systems. The hypothalamus
controls the endocrine system by controlling the pituitary gland.
PITUITARY GLAND
This is located in the cella tursica (totally encased in bone), which gives you a clue as to
how important this gland is. It has two parts.
ADENOHYPOPHYSIS is the anterior pituitary.
NEUROHYPOPHYSIS is the posterior pituitary.
ADENOHYPOPHYSIS
Secretes hormones which affect other glands. Some people say the pituitary gland is the
master gland because it controls the rest of the endocrine glands, but the hypothalamus
controls the pituitary gland, so really, the hypothalamus is the Master Gland.
The hypothalamus produces hormones which affect the pituitary, for example:
Thyroid Stimulating Hormone Releasing Hormone (TSH-RH).
This affects the adenohypophysis to secrete Thyroid Stimulating Hormone (TSH).
This affects the thyroid gland to secrete Thyroid hormone (TH)
There are many more hormones, all with the same pattern.
The Hypothalamus can also secrete inhibiting hormones:
TSH-Inhibiting Hormone prevents the adenohypophysis from secreting TSH.
The Adenohypophysis can also secrete hormones that affect the body directly, like
Growth hormone, unlike other exocrine glands.
The hypothalamus affects the adenohypophysis, and that’s about it.
Why dilute its hormones in the bloodstream? It can get there via a portal system.
A portal system goes from capillary bed  vein  capillary bed  vein  heart.
It has two capillary beds.
Hormones are produced in the hypothalamus, and enter the first capillary bed, go to a
vein directly into the pituitary gland, enter another capillary bed, and into the pituitary
tissues. Hormones secreted by the pituitary gland go right into a vein, into the blood
stream, and to the rest of the body.
NEUROHYPOPHYSIS
This is a continuation of the brain; cell bodies of special neurons in the hypothalamus
have axons which go to the neurohypophysis and synapse on capillaries there. Instead of
releasing neurotransmitter, they release hormones.
Examples are OXYTOCIN  small muscle contraction in childbirth (artificial = pertossin),
and ANTI-DIURETIC HORMONE  kidneys  urine output.
OTHER ENDOCRINE GLANDS (20 mins)
THYROID GLAND located inferior to thyroid cartilage.
Makes thyroid hormone = THYROXIN  metabolic rate, etc.
The thyroid gland has spheres of simple cuboidal epithelium which form THYROID
FOLLICLES, filled with THYROID HORMONE.
Thyroid hormone contains iodine. If a person doesn’t eat enough iodine, they can’t make
thyroid hormone. The hypothalamus responds by putting out more TSH-RH. The pituitary
will respond by releasing TSH. But the thyroid can’t respond, so it grows the size of the
follicles  gland grows  GOITER. This is usually caused by too little iodine in diet.
That’s why salt is iodized. Iodine is only found in seafood, so if salt wasn’t iodized, a lot of
people wouldn’t get enough iodine, and there would be a lot of goiters. There are more
problems with the thyroid gland than any other organ.
PARATHYROID GLANDS
These are four glands, embedded in the thyroid gland. They make PARATHYROID
HORMONE  controls calcium levels.
PANCREAS
This is an endocrine and an exocrine gland.
Exocrine glands secrete into a duct.
The pancreas has channels that end in exocrine glands, and interspersed among these are
PANCREATIC ISLETS, which are endocrine. For example, they make INSULIN, which
controls blood sugar levels. Type I diabetes is caused by destruction of pancreatic islets by
autoimmune disorders.
ADRENAL GLANDS (“On top of the kidney”; Latin)
Actually, there are two glands:
ADRENAL CORTEX produces steroid hormones like cortisone  reduces inflammation,
and sex hormones for the opposite sex: Males produce estrogen here, and females produce
testosterone.
ADRENAL MEDULLA is a separate gland, produces a separate hormone, for example
ADRENALIN (AKA epinephrine “above the kidney”; Greek). This is the neurotransmitter
for the sympathetic nervous system. The adrenal medulla also has sympathetic neurons
which synapse on it, so when you are spooked, the neurons fire, and also stimulate the
adrenal medulla to release more epinephrine to increase the effects of the sympathetic
nervous system.
MISCELLANEOUS ENDOCRINE GLANDS
The glands we talked about have no other function than to make hormones.
But almost all organs are endocrine glands in addition to their other functions.
OVARIES make eggs and secrete estrogen and other hormones.
TESTES make sperm and secrete testosterone.
HEART pumps blood and produces hormones
PANCREAS makes digestive enzymes and produces hormones.
STOMACH digests food and produces hormones.
LIVER makes enzymes and produces hormones.
LUNGS oxygenate and produces hormones.