Discussion Notes (Anaphy)
Discussion Notes (Anaphy)
Discussion Notes (Anaphy)
The nervous system is the body’s control center and communication network -
provides higher mental function and emotional expression, maintains homeostasis,
and regulates the activities of muscles and glands
It shares in the maintenance of homeostasis with the endocrine system –
controlling the master gland (pituitary gland) through the hypothalamus of the
brain
FUNCTION
Communication by the nervous system
- Involves a combination of electrical and chemical signals
- Transmits and receive impulses – electrochemical signal
It uses its millions of sensory receptors to monitor changes occurring both
inside and outside the body.
Stimuli – changes in the internal and external environment
Sensory input – gathered information
It processes and interprets the sensory input and
decides what should be done at each moment—a
process called integration.
It then causes a response, or effect, by activating
muscles or glands (effectors) via motor output
ORGANIZATION
B. PERIPHERAL NERVOUS
SYSTEM OR PNS
All parts of the nervous system outside the CNS.
It consists mainly of the nerves that extend from the spinal cord and brain.
These nerves serve as communication lines. They link all parts of the body
by carrying impulses from the sensory receptors to the CNS and from the
CNS to the appropriate glands or muscles.
Spinal nerves – carry impulses to and from the spinal cord
Cranial nerves – carry impulses to and from the brain
DIVISION or FUNCTIONAL CLASSIFICATION
OF PNS
Sensory Division (Afferent Division)
Consist of sensory or afferent neurons
Convey information from receptors in the periphery of the body to the brain
and spinal cord
Sensory receptor CNS
Visceral sensory – afferent neuron that conduct sensory impulses (usually
pain or reflex sensations) from the internal organs, glands, and blood
vessels to the CNS. Part of the ANS
Motor Division (Efferent Division)
Consist of motor or efferent neurons
Convey information from brain and spinal cord to muscle and glands
CNS OMG (organ, muscle and glands)
NERVOUS TISSUE
Have 2 basic component: 1) Neuron or nerve cell and 2) Neuroglia
Nerve – a bundle of nerve cell or fibers
Nerve plexus – a branching network of intersecting nerves
NEUROGLIA
Also called glia or glial cells
They are not able to transmit nerve impulses, a function that is highly
developed in neurons.
Never lose their ability to divide contrary to neurons
FUNCTION > support, insulate, and protect the delicate neurons
CNS NEUROGLIA
Astrocytes
Star-shaped cells that wrap around neurons for support in the brain and
spinal cord and connect neurons to blood vessels
FUNCTION > Blood-brain barrier or BBB which prevent toxic substances
entering the brain
Oligodendroglia
look like small astrocytes.
They form connective-like tissue rows for support and form the fatty myelin
sheath on the neurons in the brain and spinal cord
FUNCTION > Provide support and connection
Myelin sheath – fatty insulating coverings that protect the axons in
transferring signals in a normal condition ( more info go to neurons –
structure )
Microglia
Are small cells that do phagocytosis of microbes and cellular debris
FUNCTION > Involved in the phagocytosis of unwanted substances
Ependymal cells
Line the fluid-filled ventricles of the brain
Some produce cerebrospinal fluid and others, with cilia, move it through the
CNS
FUNCTION > Form the lining of the cavities in the brain and spinal cord
PNS NEUROGLIA
Schwann cells
Form myelin sheaths around nerve fibers in the PNS
Located only in the PNS
Function > make up the neurilemma and myelin sheath
Satellite cells
Act as protective, cushioning cells for peripheral neuron cell bodies.
STRUCTURE
It consists of 3 main parts: 1) Dendrites, 2) Soma or body cell, and 3) Axon
Dendrites
Extensions of the cell body and are the receptive areas of the neuron
FUNCTION > Receives nerve impulse from another neuron which transmit it
to the cell body
Cell Body
Consists of a single nucleus – control center of the cell
The rough ER (Nissl bodies) and neurofibrils (intermediate filament
important for maintaining the cell shape) are abundant in the cell body
Axon
Single long extension of the cell body that begins as a slight enlargement
FUNCTION > Conduct nerve impulses away from the cell body and transfer it
to another neuron
Axon Hillock – Conelike region of the cell body where axon begins
Axon Terminal – Extensions in the end of the axon
Neurotransmitter – Tiny vesicles, or membranous sacs, that contain
chemicals found in axon terminal which then release in the extracellular
space bet. neurons
Myelin Sheath – Covering of the axons
Protects and insulates the fibers and increases the transmission rate of
nerve impulses (best example for this is electrical cord – it helps fasten the
flow of current)
CLASSIFICATION OF NEURON
BY STRUCTURE
Based on the no. of processes (dendrites and
axon)
Multipolar Neuron
Consists of many dendrites and one axon
EXAMPLE > Brain and spinal cord
Bipolar Neuron
Consists of one dendrite and one axon
EXAMPLE > Eyes and nose (special sense organs)
Unipolar Neuron
Appear to have one axon and no dendrite
Divided into two: 1) Peripheral process (function as a dendrite) and 2)
Central process (function as an axon)
EXAMPLE > Most sensory neurons
BY FUNCTION
Based on direction the nerve impulse travels relative to the CNS
Sensory or Afferent Neuron
Receive the impulse directly from the
receptor site to the CNS
Unipolar neurons
Cutaneous sense organ – a type of
sensory receptor that is found in the
skin
Proprioceptors – sensory receptor in
the muscle and tendon (detect the
amount of stretch or tension – to maintain balance)
Motor or Efferent Neuron
Carry impulses from the CNS towards to OMG
Multipolar neurons
Interneuron or Association Neuron
Transmit the impulse for interpretation and processing within the CNS
Connect the sensory and motor neuron in neural pathways
Multipolar Neurons
STEPS
Resting membrane is polarized
In the resting state, the external face of the membrane is slightly positive
and internal face is slightly negative.
Chief extracellular ion - Sodium (Na+)
Chief intracellular ion – Potassium (K+)
The membrane is relatively impermeable to both ions
Stimulus initiates local depolarization
A stimulus changes the permeability of a local "patch" of the membrane, and
sodium ions diffuse rapidly into the cell
This changes the polarity of the membrane (the insi de becomes more
positive; the outside becomes more negative) at that site.
Depolarization and generation of an action potential
If the stimulus is strong enough, depolarization causes membrane polarity to
be completely reversed, and an action potential is initiated.
Depolarization – The action potential when nerve impulse begins to change
the concentration of electrical charge inside and outside the axon terminal
(sodium ion rushes inside the neuron changing the electrical charge from
negative to positive)
Propagation of the action potential
Depolarization of the first membrane patch causes permeability changes in
the adjacent membrane, and the events described in step 2 are repeated
The action potential propagates rapidly along the entire length of the
membrane
Repolarization
Potassium ions (K1) move out to try to restore the resting membrane
potential and the sodium-potassium pump operates to restore the original
charge
Repolarization occurs in the same direction as depolarization
Initial ionic conditions restored
The ionic conditions of the resting state are restored later by the activity of
the sodium-potassium pump
Three sodium ions are ejected for every two potassium ions carried back into
to the cell
This restores the fiber’s membrane to the original resting or membrane
potential
All-or-none law – states that if a nerve fiber carries any impulse, it will
carry a full-strength impulse
TRANSMISSION OF THE
SIGNAL AT SYNAPSES
The change of the sodium-potassium pump
creates an imbalance hence conducts an
active potential
A neurotransmitter chemical crosses the
synapse to transmit the signal from one
neuron to the next, or to the target cell
Synapse – an area where the terminal
branches of an axon are close to but not
touching the dendrites of another neuron
When the action potential reaches an axon
terminal the electrical change opens calcium
channels
This calcium ions, in turn, cause the tiny
vesicles containing neurotransmitter to fuse
with the axonal membrane and pore like
openings form, releasing the neurotransmitter into the synaptic cleft
Neurotransmitter – molecules diffuse across the synaptic cleft and bind to
receptors on the membrane of the next neuron
- allows the impulse to travel across the synapse.
- Example are epinephrine or adrenaline, norepinephrine, serotonin, dopamine, and
the endorphins
Electrical signal – the transmission down the length of the neuron’s membrane
Chemical signal – signal stimulated by a neurotransmitter
Electrochemical event – the transmission of impulses bet. 2 neurons
- The term used to describe the signal when neuron impulse occurs
PHYSIOLOGY:
REFLEXS
REFLEX
Rapid, predictable, and
involuntary
responses to an
external stimulus
A reflex then is an involuntary reaction or response to a stimulus applied to
our periphery and transmitted to the CNS
Most reflex integration do not travel until the brain – being integrated in the
spinal cord only
One-Way Streets— once a reflex begins, it always goes in the same
direction
EXAMPLE > When we prick our finger on a rose thorn and immediately pull
away from the source of pain
TYPES OF REFLEXES
Somatic reflexes
Reflexes that stimulate the skeletal muscle (note: though skeletal muscle
are voluntary there are some instances involuntary reaction occur in our
body)
EXAMPLE > When we pull our hands away when an object is hot due to pain
Autonomic reflexes
It regulates the activity of smooth muscles, the heart, and glands
It regulates such body functions as digestion, elimination, blood pressure,
and sweating
EXAMPLE > Secretion of saliva (salivary reflexes)
REFLEX ARC
Neural pathway that causes a reflex
Gray matter
Consisting of nerve cell bodies and dendrites where there is little myelin
It also can consist of bundles of unmyelinated axons and their neuroglia
Cortex – gray matter on the surface of the brain
Horns – areas of gray matter in the spinal cord
Ganglia – Cluster of nerve cell bodies found outside the CNS that are primarily
made of masses of gray matter
Central Nervous System 19/08/2019 4:46 PM
Consists of the brain and spinal cord, which occupy the dorsal
body cavity
FUNCTION > Act as the integrating and command centers of the
nervous system
> They interpret incoming
sensory information and issue
instructions based on past
experience and current
conditions
BRAIN
The control center of the
nervous system in all animals
Consist of 4 major parts: (1)
cerebrum (2) Diencephalon (3)
Brainstem and (4) Cerebellum
CEREBRUM
Most superior part of the brain
Bulk of the brain
Enclose and obscure most of the brain stem and diencephalon – so
many brain stem and diencephalon structures cannot normally be
seen unless a sagittal section is
made
Gyri(p.) – folds on the cerebrum or
elevated ridges of tissue
- Gyrus – singular form
Sulci(p.) – intervening grooves
which separates the gyri
- Sulcus – singular form
Fissures – Deeper grooves which
separates larger region of the brain
Longitudinal fissure – a single fissure that separates into right
and left halve or cerebral hemisphere
LOBES
Are the division of the sulci and
fissures
Named after the cranial bones that
lie over them
Central sulcus - separates the
frontal and parietal lobes
Lateral sulcus - separates the
frontal, temporal, and parietal
lobes
Frontal Lobe
Anterior portion of each hemisphere
FUNCTION > controls voluntary muscular functions, moods,
aggression, smell reception, and motivation
Parietal Lobe
Behind the frontal lobe and is separated from it by the central
sulcus
FUNCTION > control center for evaluating sensory information of
touch, pain, balance, taste, and temperature
Temporal Lobe
Beneath the frontal and parietal lobes and is separated from them
by the lateral fissure
FUNCTION > evaluates hearing input and smell as well as being
involved with memory processes
> important center for abstract thoughts and judgment decision
Occipital Lobe
Forms the back portion of the hemisphere
FUNCTION > receiving and interpreting visual input
Insula
embedded deep in the lateral sulcus
CEREBRAL HEMISPHERE
The right and left halves of the brain
Singular form of the cerebrum
Composed of 3 basic regions: (1) cortex (2) White matter and (3)
Basal nuclei
CEREBRAL CORTEX
Gray matter of the hemisphere
FUNCTION > Localizes and interprets sensory inputs
> Controls voluntary and skilled skeletal muscle activity
> Acts in intellectual and emotional processing
> Speech, memory, logical and emotional responses, consciousness,
the interpretation of sensation, and voluntary movement
Postcentral gyrus – afferent or sensory neuron
- primary somatic sensory cortex which allows you to recognize
pain, differences in temperature, or a light touch
Precentral gyrus – efferent or motor neuron
- primary motor cortex which allows us to consciously
move our skeletal muscles
CEREBRAL WHITE MATTER
composed of fiber tracts
Internal area of the hemisphere
FUNCTION > carrying impulses to, from, or within the cortex
FIBER TRACTS
Corpus callosum
Known as commissures
A very large fiber tract that arches
above the structures of the brain stem
allows the cerebral hemispheres to
communicate with one another
Important for cortical functional areas
since they can be found in only one
hemisphere
Association Fiber Tracts
connect areas within a hemisphere
Projection Fiber Tracts
connect the cerebrum with lower CNS centers, such as the brain
stem
BASAL NUCLEI
“islands” of gray matter
situated deep within the white matter – considered as a region
next to the white matter
FUNCTION > Help regulate voluntary muscle activity by modifying
instruction sent to skeletal muscle (starting and stopping
movement)
DIENCEPHALON
Also known as interbrain
Sits atop the brain stem and is enclosed by the cerebral
hemispheres
MAJOR STRCUTURE
Thalamus
Superior part of the diencephalon
Encloses the shallow third ventricle of the brain
FUNCTION > Relays sensory impulses to cerebral cortex
> Relays impulses between cerebral motor cortex and lower motor
centers
> Involved in memory
EXAMPLE > As impulses surge through the thalamus, we have a crude
recognition of whether the sensation we are about to have is
pleasant or unpleasant
Hypothalamus
Makes up the floor of the diencephalon – inferior part
FUNCTION > Crucial for ANS regulation - it plays a role in
regulating body temperature, water balance, and metabolism
> Regulates hormonal output of anterior pituitary gland and
acts as an endocrine organ (producing ADH and oxytocin)
Important part of the limbic system (emotional-visceral brain)
Mammillary bodies – found on the undersurface of the diencephalon
- bulge from the floor of the hypothalamus posterior to the
pituitary gland
- reflex centers involved in olfaction (the sense of smell)
Epithalamus
Small area superior and posterior to the thalamus
Form the roof of the third ventricle
Important parts > pineal gland and choroid plexus of the third
ventricle
FUNCTION > It contains small nuclei that are concerned with
emotional and visceral responses to odor
BRAIN STEM
About the size of a thumb
Has many small gray matter areas
FUNCTION > provides a pathway for ascending and descending tracts
– connects the brain and spinal cord
> Controls vital activity (ex. Breathing and blood pressure)
Location of the cranial nerve nuclei – for controlling cranial
activities
MAIN STRUCTURE
Midbrain
Contains visual and auditory reflex centers
Contains subcortical motor centers
Contains nuclei for cranial nerves III and IV; contains
projection fibers (e.g., fibers of the pyramidal tracts)
Cerebral aqueduct - a tiny canal that travels through the
midbrain, connects the third ventricle of the diencephalon to the
fourth ventricle below
Pons
Rounded structure that protrudes just below the midbrain
Composed mainly fiber tracts
FUNCTION > Relays information from the cerebrum to the cerebellum
> Cooperates with the medullary centers to control respiratory
rate and depth
> Contains nuclei of cranial nerves V–VII; contains projection
fibers
Medulla Oblongata
the most inferior part of the brain stem
It merges into the spinal cord below without any obvious change
in structure
FUNCTION > Relays ascending sensory pathway impulses from skin
and proprioceptors
> Contains nuclei controlling heart rate, blood vessel diameter,
respiratory rate, vomiting, etc.
> Relays sensory information to the cerebellum
> Contains nuclei of cranial nerves VIII–XII; contains projection
fibers
> Site of crossover of pyramids
Fourth ventricle - lies posterior to the pons and medulla and
anterior to the cerebellum
Reticular Formation
diffuse mass of gray matter
The neurons of the reticular formation are involved in motor
control of the visceral organs (ex. controlling smooth muscle in
the digestive tract)
Reticular activating system (RAS) - A special group of reticular
formation neurons
- FUNCTION > plays a role in consciousness and the awake/sleep
cycle
> acts as a filter for the flood of sensory inputs that
streams up the spinal cord and brain stem daily
- Damage to this area can result in prolonged unconsciousness
(coma)
CEREBELLUM
Cauliflower shape
projects dorsally from under the occipital lobe of the cerebrum
Consists of: (1) two hemisphere same as cerebrum
(2) Convoluted surface
(3) Outer cortex made of gray matter
(4) Inner region of white matter
FUNCTION > Processes information from cerebral motor cortex,
proprioceptors, and visual and equilibrium pathways
> Provides “instructions” to cerebral motor cortex and
subcortical motor centers, resulting in smooth, coordinated
skeletal muscle movements
> Responsible for proper balance and posture
EXAMPLE > Drinking alcohol –making our movement clumsy
Ataxia – a condition when the cerebellum is damage thus making
movement clumsy and disorganized
MENINGES
connective tissue membranes covering and
protecting the CNS structures
Spinal meninges – minges that are found on
the spinal cord
Meningitis – disease due to the
inflammation of minges
LAYERS
Dura mater
Known as tough mother
Outermost layer
a double-layered membrane where it surrounds the brain and spinal
cord
One of the layers of the dura mater of the brain is – attached to
the periosteum (inner layer of the skull)
Meningeal layer – forms the outermost covering of the brain and
continues as the dura mater of the spinal cord
Epidural space – a space bet. The spinal meninges and vertebrae
- This space contains loose connective tissue and some adipose
tissue that acts as a protective cushion around the spinal cord
Subdural space – space bet. The dura mater and arachnoid mater
Arachnoid mater
Known as spider layer
middle meningeal layer
It forms a delicate connective membranous tube inside the dura
mater
Subarachnoid space – space bet the arachnoid mater and pia mater
- where CSF circulates
Pia mater
Known as delicate mother
A transparent fibrous membrane that forms a tube around and
adheres to the surface of the spinal cord (and brain)
It contains numerous blood vessels and nerves that nourish the
underlying cells
CERERBROSPINAL FLUID
watery “broth” with components similar to blood plasma, from
where it is derived from
clear, colorless body fluid found in the brain and spinal cord
Its difference to blood plasma > it contains less protein and
more vitamin C, and its ion composition is different
Produced by specialized ependymal cells in the choroid plexus of
the ventricles of the brain and absorbed by the arachnoid
granulations
Free of RBC and contain a few WBC
Choroid plexus - clusters of capillaries hanging from the “roof”
in each of the brain’s ventricles
FUNCTION > watery cushion that protects the fragile nervous
tissue from blows and other trauma
> helps the brain “float” so it is not damaged by the pressure of
its own weight
FORMATION OF CSF
Blood circulates up in the brain through the arteries carotid and
through the capillaries
Through filtration the blood is being filter by the tight
junction and the BBB as it enters the intercellular matrix of the
brain which is the choroid plexus
Monocytes – WBC that can only enter the brain
VENTRICLES
Where the CSF flows after it was modified in the choroid plexus
Where the choroid plexuses are found
Consists of 4 ventricles: (1) Lateral ventricle – 2 (left and
right ventricle)
(2) 3rd ventricle – 1
(3) 4th ventricle – 1
Intraventricular foramen – a narrow oval opening bet. the lateral
ventricle and third ventricle
Cerebral aqueduct – connects the third and fourth ventricle
Paired lateral apertures (up around
the brain) and median aperture
(central canal in spinal cord) - found
in the wall of the 4th ventricle that
serve as opening for CSF in order to
flow towards the subarachnoid spaces
CONDITIONS
What can easily pass through?
Water soluble substances
EXAMPLE > water, glucose and
essential amino acids
What substances that are prevented?
Metabolic waste
EXAMPLE > urea, toxins and most
drugs
What substances which are useless
for the BBB?
Fats, respiratory gases, and other
fat-soluble molecules
EXAMPLE > Alcohol, nicotine, anesthesia and drugs
SPINAL CORD
Continuation of the medulla oblongata
Enclosed within the vertebral column
Extends from the foramen magnum of the skull and first cervical
bone of the vertebral column (C1) to the first or second lumbar
vertebra (L2), where it ends just below the ribs
Made of 31 segments, each giving rise to a pair of spinal nerves
Protected by the spinal meninges (meninges of the spinal cord)
FUNCTION > A major reflex center (for fight-flight situation)
> two-way conduction pathway to and from the brain
STRUCTURES
Horns: Gray matter of SC
Shape like a butterfly or the letter H in cross section
Location of neurons w/ specific function
Dorsal or posterior horns – two posterior projection
- contain interneurons
Ventral or anterior horns – two anterior projection
- contain motor neurons
Roots
A segment where spinal nerve is attaches
Dorsal or posterior roots – contains sensory roots which conduct
impulse from the periphery to the SC
Ventral or anterior roots – contains motor roots which conduct
impulse from the SC to the periphery
Spinal nerve – fuse of dorsal and ventral roots
White matter of SC
composed of myelinated fiber tracts
running to higher centers, some traveling from the brain to the
cord, and some conducting impulses from one side of the spinal
cord to the other
3 REGIONS: (1) Posterior column (2) Lateral column and (3)
Anterior column
Posterior column – contain ascending tracts that carry sensory
input
Lateral column and anterior column - contain both ascending and
descending (motor) tracts
PERIPHERAL NERVOUS SYSTEM 19/08/2019 4:46 PM
All parts of the nervous system outside the CNS.
It consists mainly of the nerves and scattered ganglia
These nerves serve as communication lines. They link all parts of the body by carrying impulses
from the sensory receptors to the CNS and from the CNS to the appropriate glands or muscles
Spinal nerves – carry impulses to and from the spinal cord
Cranial nerves – carry impulses to and from the brain
CRANIAL NERVE
“Oh! Oh! Oh! To touch and feel very good velvet at home”
There 12 cranial nerve primarily serve the head and neck.
one pair (the vagus nerves) extends to the thoracic and abdominal cavities
12 CRANIAL NERVES
Olfactory
Sensory
Origin > Fibers arise from olfactory receptors in the nasal mucosa and synapse with the
olfactory bulbs (which, in turn, send fibers to the olfactory cortex) – Nose
Function > Carries impulses for the sense of smell
Optic
Sensory
Origin > Fibers arise from the retina of the eye and form the optic nerve – Eye
Function > Carries impulses for vision
Oculomotor
Motor
Origin > Fibers run from the midbrain to the eye – Muscles of the eye
Function > Supplies motor fibers to four of the six muscles (superior, inferior, and medial rectus,
and inferior oblique) that direct the eyeball
> Movement of the eyeball and regulates the size of the pupil
Trochlear
Motor
Origin > Fibers run from the midbrain to the eye – Muscles of the eye
Function > Supplies motor fibers for one external eye muscle (superior oblique)
> For eye movement
Trigeminal
Mixed
Origin > Fibers emerge from the pons and form three divisions that run to the face – Face
Function > Sensory - Conducts sensory impulses from the skin of the face and mucosa of the
nose and mouth
Motor - Contains motor fibers that activate the chewing muscles
Abducens
Motor
Origin > Fibers leave the pons and run to the eye – Muscles in the eye
Function > Supplies motor fibers to the lateral rectus muscle, which rolls the eye laterally
> Movement of the eyeball – particularly abduction
Facial
Mixed
Origin > Fibers leave the pons and run to the face – Muscles of the face
Function > Sensory - carries sensory impulses from the taste buds of anterior tongue (for taste)
Motor - Activates the muscles of facial expression and the lacrimal and salivary glands (Facial
expressions and secretion of saliva)
Vestibulocochlear
Sensory
Origin > Fibers run from the equilibrium and hearing receptors of the inner ear to the brain
stem – Inner ear
Function > Consist of 2 function
> Vestibular branch transmits impulses for the sense of balance
> Cochlear branch transmits impulses for the sense of hearing
Glossopharyngeal
Mixed
Origin > Fibers emerge from the medulla and run to the throat
Function > Motor - Supplies motor fibers to the pharynx (throat) that promote swallowing and
saliva production (swallowing and secretion of saliva)
> carries sensory impulses from taste buds of the posterior tongue and from pressure receptors
of the carotid artery (taste)
Vagus
Mixed
Origin > Fibers emerge from the medulla and descend into the thorax and abdominal cavity –
Internal organs
Function > Mixed - Fibers carry sensory impulses from and motor impulses to the pharynx,
larynx, and the abdominal and thoracic viscera
> most motor fibers are parasympathetic fibers that promote digestive activity and help
regulate heart activity
Accessory
Motor
Origin > Fibers arise from the superior spinal cord
(C1–C5)* and travel to muscles of the neck and back –
Sternocleidomastoid and trapezius muscle
Function > Mostly motor fibers that activate the
sternocleidomastoid and trapezius muscles (shoulder
movement, turning head and voice production)
Hypoglossal
Motor
Origin > Fibers run from the medulla to the tongue –
Muscles of the
tongue
Function > Motor
fibers control tongue
movements
SPINAL NERVE
There are 31 pairs of human spinal
nerves
Formed by the combination of ventral
and dorsal roots
DIVISION
Divided into 2 in each root: (1) Dorsal ramus and (2) Ventral ramus
Rami – like the spinal nerve which has both sensory and motor fibers
Dorsal rami
Smaller dorsal rami – serve the skin and muscles of the posterior body trunk
Ventral rami
ventral rami of spinal nerves T1 through T12 form the intercostal nerves – supply the muscles
between the ribs and the skin and muscles of the anterior and lateral trunk
NERVE PLEXUS
Complex network of ventral rami of all spinal nerve
Cervical
Origin > C1- C5
Important nerve > Phrenic - Diaphragm; skin and muscles of shoulder and neck
Brachial
Origin > C5–C8 and T1
Important Nerve > Axillary - Deltoid muscle and skin of shoulder; muscles and skin of superior
thorax
> Radial - Triceps and extensor muscles of the forearm; skin of posterior upper limb
> Median - Flexor muscles and skin of forearm and some muscles of hand
> Musculocutaneous - Flexor muscles of arm; skin of lateral forearm
> Ulnar - Some flexor muscles of forearm; wrist and many hand muscles; skin of hand
Lumbar
Origin > L1–L4
Important Nerve > Femoral - Lower abdomen, anterior and medial thigh muscles (hip flexors
and knee extensors), and skin of anteromedial leg and thigh
Sacral
Origin > L4–L5 and S1–S4
Important nerve > Sciatic - Largest nerve in body
- splits to common fibular and tibial nerves just above knee
- Lower trunk and posterior surface of thigh (hip extensors and knee flexors)
-Fibular: Lateral aspect of leg and foot
- Tibial: Posterior aspect of leg and foot
➔ Optic disk - the point where the optic nerve leaves the back
of the eyeball ; optic disk has no photoreceptors resulting in
the blind spot in our vision
➔ Lens - major light-bending (refractory) structure ; convexity
is increased by the ciliary body contraction for close focus;
divided into two segments filled with fluid that reinforce the
eye internally by maintaining intraocular pressure
○ Aqueous Humor - provides nutrients to the avascular lens and
the cornea; anterior to the lens; similar to blood plasma,
secreted by special area in choroid
○ Vitreous Humor - posterior to the lens
➔ Errors of refraction: myopia, hyperopia, astigmatism
➔ Pathway of Light:
○ Cornea ➠ Aqueous Humor ➠ (through pupil) ➠ Aqueous Humor ➠
Lens ➠ Vitreous Humor ➠ Retina
➔ Eye Reflexes:
○ Photopupillary Reflex - immediate constriction of pupils when
suddenly exposed to bright light ; prevents light from damaging
photoreceptors
○ Accommodation Pupillary Reflex - pupil constriction when
viewing close objects , providing more acute vision
○ Convergence Reflex - reflexive movement of the eyes medially
when viewing close objects ; during convergence both eyes are
aimed at the near object being viewed
Sound Pathway:
1.) Soundwaves start at the auricle or pinna where they are
caught to be passed along...
2.) Through the external auditory meatus , where they travel down
the auditory canal to
eventually collide with the tympanic membrane (or eardrum)
3.) The soundwaves’ collision with the eardrum causes it to
vibrate back and forth, pushing
it against the auditory ossicles (hammer, incus, and stapes) and
passing the vibration to
them
4.) The auditory ossicles amplify the vibrations so they can pass
it along through the oval
window …
5.) And to the cochlea
6.) The cochlea has the basilar membrane where fibers vibrate and
stimulate the hair cells
in the spiral organ of corti
7.) The organ of corti has hair cells that can generate action
potential allowing electrical
impulses to travel from the organ of corti and along…
8.) The cochlear nerve to the auditory pathway and finally to the
cerebral cortex where
electrical impulse is interpreted
Sense of Smell
➔ Olfactory receptors are located in the superior aspect of each
nasal cavity; in order to be excited, chemical substances must be
dissolved in aqueous solution (this also applies to gustatory
receptors) ; gustation and olfaction need chemoreceptors to
detect the molecules in our food and the air we breath
Odor Pathway
1) Odor must be volatile or in a gaseous state in order to be
smelled
2) Some of the molecules that are sniffed up the nasal cavity
reach the olfactory epithelium
(containing olfactory sensory neurons) where they are dissolved
by the mucus that coats
it
3) Once in the mucus, the molecules bind to the receptors on the
olfactory sensory neurons
which fire action potentials up to the olfactory bulb of the
brain
4) The olfactory bulb is where mitral cells pick up the
information from the olfactory
neuron
5) Mitral cells send information along the olfactory tract and to
the olfactory cortex
6) Information is sent to two avenues: the frontal lobe (where
smell is identified) and the
limbic system (where odor is associated and memories are aroused)
Sense of Taste
➔ Taste Buds - receptors for the sense of taste; each bud has
epithelial receptor cells: gustatory (for tasting) and basal
(stem cells for replacement) ; found on the tongue’s papillae;
scattered in the oral cavity; mostly found on the tongue, some
are on the soft palate, superior part of the pharynx, and inner
surface of cheeks
➔ Gustatory Cells - epithelial cells that respond to the
chemicals dissolved in the saliva
● Taste pores - where dissolved chemicals diffuse to bind to the
receptors on the gustatory cells
● Gustatory hairs - long microvilli that protrude through the
taste pores; when stimulated they depolarize (action potential)
and impulses are sent to the brain
➔ The vagus , glossopharyngeal , and facial nerve carry these
impulses to the gustatory cortex
Pathway of Taste
1.) Molecules are dissolved by saliva
2.) And come into contact with the gustatory hairs
3.) The now dissolved molecules can then diffuse into the taste
pores
4.) Where they can bind to the receptors on the gustatory cells ,
triggering an action potential
5.) Impulse is relayed via the cranial nerves (7, 9, 10) to the
gustatory cortex
6.) Brain then releases digestive enzymes to help digest food
The Endocrine System 19/08/2019 4:46 PM
-Second Control System of the body
-Produces hormones
-Hormones released by ES glands travel through the blood and alter the activity of target cells.
- Mobilizes body defenses against stressors, maintaining electrolyte, water, and nutrient balance
of blood
~ Exocrine
Has ducts that secrete; pathway
~ Endocrine
Supplied with good numbers of blood vessels
Ductless
Hormone
Prominent Hormones (came from the greek word “hormon” that means to arouse or to stimulate)
Male – Testosterone
Female – Estrogen
Prostaglandin
- if this is triggered, you will start feeling the pain (if you
have a wound)
Hormones are:
Amino acids based molecules
o Proteins, peptides, and amines
Affects target cells or target organs
Hormones can:
Change plasma membrane permeability or membrane potential
(electrical state) by opening or closing ion channels
Activate or inactivate enzymes
Stimulate or inhibit cell division
Promote or inhibit secretion of a product (end product of
enzymes)
Turn on or turn off transcription of certain genes (such
as those encoding proteins or regulatory molecules
(Transcription-nucleus Translate-cytoplasm((by
ribosomes)))
Increase or decrease the rate of our usual metabolic
processes
Second-Messenger System
o Steroid hormones can influence cell activity either
by direct gene activation or by the indirect pathway
of activating a second messenger. Protein andpeptide
hormones, however, are not water-soluble and are
unable to enter target cells directly. Instead, they
bind to hormone receptors situated on the target
cell’s plasma membrane and use a second-messenger
system.
1.
2.
3.
4.
Parathyroid Gland
o Found at the Posterior of the TG
2 per TG
reportedly as many as 8
o Secretes Parathyroid Hormone
Breakdowns bone matrix and releasing CA to
bloodstream (target: kidney & intestine –
absorbs more calcium)
Hypercalcemic
Released when low blood calcium
Thymus
o Upper thorax posterior to the sternum
o Large (infant & childhood)
o Decreases size (adults)
o Thymosin Hormone
Essential for the normal development of special
group of white blood cells
Tlymphocytes
Immune response
Adrenal Glands
o Adrenal Cortex (outer)
3 hormones (corcosteriods)
Mineralcorticoid (aldosterone) –
regulating; -Targets kidney tubules (More
Na reabsorb (w H2O), more k out in urine)
– Stimulated by Humoral Stimuli
Glucocorticoid (cortisone, cortisol)
Promotes normal cell development
Helps body resist long term stressors
by:
o Increasing blood glucose level
o Decreases edema and inhibits
prostaglandins during
inflammatory response
Triggered by rising blood (ACTH)
sex hormones [estrogen(female) & androgens
(male)]
o Adrenal Medulla (inner)
Stimulated by the Sympathetic Nervous System
Catecholamines (epinephrine – adrenaline,
norepinephrine – noradrenaline fight or
flight)
Increase heart rate, increase bp, increase
blood glucose, dilate airway increase
O2 and energy to deal short term stress
Brain, heart, & muscle
o Adrenal Cortex
Releases:
aldosterone
gluco
sex hormones Pancreas
Pancreas
o pancreatic islets
beta cells (insulin)
alpha cells (glucagon)
liver is the target organ.
glycogen to glucose
Ovary (female)
o Produces 2 steriod hormones:
estrogen & progesterone ( work together for
menstruation)
o APG FSH & LH (gonadrotropic)triggers the release
of these hormones (cyclic)
APG
Non ENDO
GH
Prolactin
Topic (turn on)
FSH
LH
Tyrotropic
Adrenocorticotropic (ACTH)
Testis (male)
o Androgens
Testosterone is the most important
Puberty reproduction & secondary sex characters
Adults continuous sperm production
Simulated by the LH
Additional Information:
*Thyroids secrete T3 & T4
*Cells are in the state of semi-permeability
*Membrane transport – the process of entering/exiting of
substances in/out of the cell membrane
*Enzymes are for speeding up chemical reaction (like the breaking
down of glycogen into glucose so the cells can accept them)
*Fibrous-structural protein || Function-functional protein
*During fight or flight, the body releases adrenaline/epinephrine
*Diuresis – to produce urine
*testosterone – hormone || sperm - cell
*Second hormone has the direct effect
*Hyperkalemia – reabsorb more K
*Hypokalemia – less K through urine
*glucagon – hormone
*glycogen - compound
*insulin doesn't have a target organ, it targets cells
*insulin is like a key, it lets the glucose out
*70% of glucose consumer are neurons
MIDTERM
- CNS ✓
- PNS
- SS
- ES
- CVS
Cardiovascular System 19/08/2019 4:46 PM