Transcript Peripheral Nervous System

NERVOUS SYSTEM
Which direction is the dancer
spinning?
NERVOUS SYSTEM
Functions:
• Coordinates body systems
• Communication system
• Reacts to the environment
(stimulusresponse)
Nervous System Organizational Chart
Human Nervous System
Central Nervous
System
Brain
Peripheral Nervous
System
Motor
Division
Spinal Cord
Somatic
Sensory
Division
Autonomic
Sympathetic
Parasympathetic
Brain
2 parts of the Central Nervous System:
– Brain and Spinal Cord
Brain• Made up of 100 billion neurons and 1 trillion
neuroglia
• Mass is approximately 3 lbs
• 4 parts- cerebrum, cerebellum, upper brain
stem and lower brain stem
Cerebrum
• Bulk of the brain
• Outer folded layer- called the cerebral cortex- is
made up of gray matter
– Where messages are received in the brain
– Peaks are called gyri
– Deep grooves are called fissures
– Shallow grooves are called sulci
• Layer below the cortex is white matter
• Divided into right and left sides called hemispheres
• The deep connection between the two
hemispheres is the corpus callosum
Lobes of the Cerebrum
• Each hemisphere is divided into 4 lobes:
– Frontal lobe- Speech, comprehension and muscle
control
– Occipital lobe- Vision
– Parietal lobe- Touch, pain, taste and temperature
– Temporal lobe- Hearing
• Frontal and parietal lobes are separated by the central
sulcus
• The precentral gyrus is anterior to the central sulcus
and the postcentral gyrus is posterior
• The lateral sulcus outlines the temporal lobe
• The parieto-occipital fissure separates the occipital and
parietal lobes
Cerebellum
• Second largest portion of the brain
• Inferior to the occipital lobes
• Surface is gray matter called cerebellar
cortex
• Below gray matter is white matter tractslook like tree branches. These tracts are
called arbor vitae (type of tree).
• Coordinates muscle contractions,
regulates posture and balance and makes
possible all skilled motor activities.
Upper Brain Stem
• Called the diencephalon
• Has 2 parts:
– Thalamus- oval mass- Acts as a relay station
for sensory impulses and also plays a role in
cognition (acquiring knowledge)
– Hypothalamus- below the thalamus- Has
many functions:
• Regulates hormones that control emotions,
behaviors, eating and drinking, body temperature,
circadian rhythms (sleep patterns), and heart rate
Lower Brain Stem
• Medulla oblongata (or medulla)- the most
inferior part of the lower brain stem and
attaches to the spinal cord. It controls the rate
and force of the heartbeat, diameter of the
blood vessels and the medullary rhythmicity
area which adjusts the rhythm of breathing.
• Pons- In between the medulla and midbraincontains the pneumotaxic and apneustic areas
for breathing
• Midbrain- Most superior part of lower brain
stem- Controls reflexes- swallowing
Reticular Formation
• Neurons scattered throughout the upper
and lower brain stem that alert the
cerebral cortex to incoming sensory
signals
• Separates important from unimportant
signals.
Protective Coverings of the Brain
• Cranium
• Meninges- 3 layers inside the cranium and
superficial to the brain. From outside to inside:
Dura mater Arachnoid layer  Pia mater
• Cerebrospinal Fluid (CSF)- circulates through
cavities in the brain- called ventricles. This
fluid “buoys” the brain so that it floats in the
cranial cavity for protection. Typically, it is
absorbed. If CSF accumulates, it builds up
pressure. This is called hydrocephalus (water
on the brain).
Hydrocephalussee Wendy’s story
Brain Protective Layers and Parts from the Outside to the Inside
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Sheep Brain Dissection
1. No food, drink or gum!
2. Wear gloves if handling the brain.
3. First, carefully remove the dura mater. Be especially
careful around the optic chiasma and pituitary gland.
4. Observe the external anatomy.
5. Cut along the longitudinal fissure to view internal
anatomy.
6. Use the packet as your guide. Complete the handout and turn it in.
External Sheep Brain
Brain-Blood Barrier
• More than 100 years ago it was discovered that
if blue dye was injected into the bloodstream of
an animal, the tissues of the whole body
EXCEPT the brain and spinal cord would turn
blue.
• The brain-blood barrier (BBB) exists because
the brain capillaries are lined with endothelial
cells that fit so tightly together that few
substances can pass out of the blood stream.
• It is permeable to water, oxygen, carbon dioxide,
glucose, alcohol, and general anesthetics.
The functions of the BBB are to:
• Protect the brain from "foreign substances" in the
blood that may injure the brain.
• Protect the brain from hormones and
neurotransmitters in the rest of the body.
• Maintain a constant environment for the brain.
• The BBB can be broken down by:
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High blood pressure
Microwaves
Radiation
Infection
Brain trauma
NERVE CELLS
1. Neuron = Information processing unit
2. Neuroglia= Support and protect
neurons; Do not conduct messages;
Smaller than neurons; 5-50 times more
numerous than neurons
Draw a neuron in your notes……
Parts of a neuron
• Cell body- Contains the nucleus
• Dendrites- Small extensions that receive
information
• Axon- Long extension that transmits
information toward another neuron.
• Axon terminal- End of an axon that stores
neurotransmitters (chemicals that continue
the message on to another neuron).
• Synapse- Space between the axon of 1
neuron and the dendrites of another. Here is
where neurotransmitters are dumped.
Parts of a neuron cont….
• Myelin sheath- Insulating fat around the
axon- increases the speed of an impulse
• Schwann cells or oligodendrocytesProduce the myelin
• Nodes of Ranvier- Gaps in the myelin
sheath along an axon
AXON TERMINAL AND SYNAPTIC
SPACE
Quick Review
• 1. What are the 2 parts to the CNS?
• 2. What is the bulk of the brain?
• 3. What are the 4 lobes of the cerebrum?
• 4. What connects the right and left halves of the
cerebrum?
• 5. What are the 2 parts to the diencephalon?
• 6. What are the 3 parts of the lower brain stem?
• 7. What are the 2 types of nerve cells?
• 8. What are the 3 meninge layers?
• 9. What part of a neuron receives messages?
• 10. What part of a neuron sends messages on to
another neuron (it is a long extension)?
SPINAL CORD
• Originates at the foramen magnum (opening at the
base of the skull)
• Protected by the vertebrae
• Covered with the same 3 meninge layers as the
brain- dura mater, arachnoid and pia mater
• Also protected by fat tissue located in the epidural
space- between the dura mater and the vertebral
column
• 16-18 inches
• Does not run the entire length of the vertebral
column. Where it ends it is called the conus
medullaris (between the L1 and L2 vertebrae)
Spinal Cord
• 31 pairs of spinal nerves coming off of the
spinal cord. Each pair originates at a
vertebra (8 cervical, 12 thoracic, 5 lumbar,
5 sacral, 1 coccyx). Spinal nerves
communicate between the spinal cord and
the rest of the body.
• Where the spinal cord ends there are
nerves that arise that angle down like
flowing hair. This is called cauda equina
(horse’s tail).
Cross Section of the Spinal Cord
• Deep anterior median fissure and the
shallow posterior median sulcus divide the
spinal cord into right and left halves.
• Center of the spinal cord is the central
canal which contains cerebrospinal fluid
surrounded by gray matter and then
surrounded by white matter.
• Each pair of spinal nerves is connected to
the cord at two points called a root.
Roots of a spinal nerve
• Posterior dorsal root- Contains sensory
neurons (afferent neurons) that carry
sensory information to the spinal cord.
• Anterior ventral root- Contains motor
neurons (efferent neurons) that carry
motor information away from the spinal
cord to the muscle.
Spinal Cord Video Clips
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Levels of spinal cord injury
Spinal cord injury
Stem cell therapy research
Stem cell therapy results
Embryonic stem cell controversy
Quiz Picture Review
A.
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E.
D.
C.
Nervous System Organizational Chart
Human Nervous System
Central Nervous
System
Brain
Peripheral Nervous
System
Motor
Division
Spinal Cord
Somatic
Sensory
Division
Autonomic
Sympathetic
Parasympathetic
Cranial Nerves
• There are 12 pairs of cranial nerves that
emanate from brain tissue or sensory
organs of the head and pass through
openings in the cranium to send
information to and from the brain.
• Cranial nerves are numbered using
Roman numerals.
Cranial Nerve
Function
I- Olfactory nerve
Sends smell information to the olfactory bulb.
II- Optic nerve
Carries sight information from the retina of the
eye and the optic chiasm is formed with the 2
optic nerves cross.
III- Oculomotor
nerve
Controls muscle movement of the eyelid and the
eyeball which allows the eye to turn, the pupil to
constrict and the lens to change its shape.
IV- Trochlear
nerve
Controls eye muscle movement.
V- Trigeminal
nerve
Allows feeling in the head region- nose, eyes,
tongue, teeth, skin, and sinuses. Also controls
muscles for chewing (mastication). Has 3
branches coming off of it.
VI- Abducent
nerve
Controls eye muscle movement.
Cranial Nerve
Function
VII- Facial nerve
Allows feeling of the face, tongue and mouth.
Also, controls muscles that cause facial
expressions, chewing and signals for salivation.
VIIIControls hearing and balance.
Vestibulocochlear
nerve
VIIIICarries temperature, pressure and taste
Glossopharyngeal information from the tongue, palate and pharynx
nerve
(throat). Signals for salivation
X- Vagus nerve
Constricts muscles of the pharynx, larynx (voice
box), esophagus, trachea (air pipe) and even
parts of the heart.
XI- Spinal
accesory nerve
Controls muscles of the shoulders and neck.
XII- Hypoglossal
nerve
Controls muscles of the tongue.
Peripheral Nervous
System (PNS)
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The PNS includes all nervous tissue except
the brain and spinal cord.
The 2 divisions of the PNS are the Sensory
Division and the Motor Divison
The Sensory Division involves sensory
neurons (afferent) detecting a stimulus and
sending the information to the brain or spinal
cord (dorsal root of spinal nerves).
Motor Division
• The Motor Division of the PNS involves
responses from the spinal cord and brain
to the muscles or glands to signal
contraction or release of fluids. This
division involves motor (efferent) neurons
(ventral root of spinal nerves).
• The 2 divisions of the Motor Division are
the Somatic Division and the Autonomic
Division.
Somatic Division
• The Somatic Division signals for the
contraction of skeletal muscles.
– What are skeletal muscles?
• This can be voluntary or involuntary.
• Involuntary skeletal muscle action involves
reflexes.
– Patellar reflex
– Withdrawal reflex
Patellar Relex
• A type of stretch reflex- Protects the muscle
against increases in length which may tear or
damage muscle fibers.
• This is also a spinal reflex where the spinal cord
is the only part of the CNS involved in the
reaction.
• The main components of a spinal reflex are:
1. Sensory receptor- Distal end of a sensory
neuron that responds to a stimulus.
2. Sensory neuron- Send messages via the
dorsal root of a spinal nerve (axon terminals are
in the gray matter).
3. Integrating center- Synapses between sensory
and motor neurons
4. Motor neuron- Sends messages via the ventral
root of a spinal nerve
5. Effector- Part of the body that responds to motor
nerve impulses (muscles and glands)
• The patellar tendon attaches the quadriceps muscle
to the tibia bone of the lower leg.
– Sensory receptor- Neuron in the quadriceps muscle that
responds to the stretching of the muscle when the patellar
tendon is stretched.
– Effector #1- Quadriceps muscle contracts, causing the
lower leg to lift.
– Effector #2- Hamstring muscle relaxes allowing the lower
leg to lift.
Autonomic Division
• The Autonomic Division signals for the
contraction of smooth and cardiac muscle.
• This is involuntary.
• The 2 divisions are the Sympathetic and
Parasympathetic Divisions
– Sympathetic- “Fight or Flight” activities
• Due to the neurotransmitter
Epinephrine/Norepinephrine (aka Adrenaline)
• Originates from the T1-L3 spinal nerves
– Parasympathetic- “Rest and Digest” activities
• Due to Acetylcholine
• Originates from the cranial and sacral nerves
Layers of the Eyeball
• The eye anatomy has 3 layers:
Fibrous tunic, vascular tunic and retina
Fibrous tunic
• This is the outer coat
• The parts include:
– Cornea- transparent covering that bends light
rays to produce a clear image. If not curved
properly, the image is blurred.
– Conjunctiva- Epithelial layer that covers the
outside edges of the cornea
– Sclera- The white of the eye composed of
dense connective tissue
• Covers all of the eyeball except the cornea
• Gives shape to the eyeball
Vascular tunic
• Middle layer
• The parts include:
– Choroid- lines the internal surface of the
sclera and provides nutrients to the eye
– Pupil- The hole in the center of the eyeball
– Iris- The colored circle around the pupil that is
composed of muscle fibers. These fibers
regulate the pupil opening- contract to reduce
pupil size (parasympathetic) and relax to
dilate (sympathetic)
– Lens- Disk that focuses light rays on the retina
Vascular tunic continued…
• Ciliary muscle (body)- Muscle that alters the shape
of the lens to focus light rays onto the retina
• Supensory Ligament (Ciliary zonule)- Attaches the
lens to the ciliary body
• Aqueous humor- Watery fluid that is found in a
chamber anterior to the lens. This fluid provides
nutrients to the lens and cornea and helps maintain
appropriate pressure of the anterior eye.
• Vitreous humor- Clear, jelly-like substance that
prevents the eyeball from collapsing. This is
posterior to the lens.
Retina
• Lines the inner ¾ of the eyeball
• Consists of a pigment epithelium and a
neural portion
• Pigment epithelium is a sheet of melanin
that absorbs stray light rays and prevents
scattering so that the image remains clear
• Neural portion contains 2 types of
photoreceptors that respond to light- rods
and cones
• Optic disk (blind spot)- Where the optic
nerve meets the retina
Rods and Cones
• Rods react to dim light (see at night)
• Cones react to bright/colored light.
– 3 types of cones that allow us to see all of the
colors
– Colorblindness is due to defective cones.
This is more common in males because it is
linked to the X sex chromosome and males
only have one.
– Fovea centralis (aka central fovea)- highest
area of visual acuity (sharpest vision)- This is
where cones are most densely concentrated.
Vision information transfer
• After the light is absorbed by the rods and
cones, the message is transferred to the
optic nerve via electric impulse. Then it
goes to the optic chiasm where the image
from the right eye crosses to the left side
of the brain and vice versa. The image
then goes to the thalamus and then the
appropriate occipital lobe (right or left).
EYE ANATOMY
Eye Activities
• Path of Light
Optic chiasma
(Occipital lobes)
Eye Activities
• Blind spot- When both eyes are open, you
don’t experience a blind spot because the
brain receives information from both eyes
at the same time and blends it. When one
eye is closed, a blind spot occurs in your
open eye when the light falls on the retina
where it connects with the optic nerve.
Here, the retina lacks photoreceptors (rods
and cones).
Eye Activities
• A Hole in Your Hand- It looks like there is
a hole through the left hand because of
the brain’s function as a processor of
information. Information from the right eye
is superimposed with information from the
left eye. The blended picture is a hole in
your hand.
Eye Activities
• After Images- Staring at an object allows
the light to burn the image onto the retina.
When you stop staring at the image, the
cells in the eye remain stimulated for a
short time, creating an after image. After
images always occur in opposite colors
because the stimulated rods and cones
are fatigued and need a chance to get
recalibrated.
PNS Review- Identify the lettered parts
Human Nervous System
Central Nervous
System
Brain
A.
B.
Spinal Cord
D.
C.
E.
F.
G.
PNS Review- Write the letter of the
division of the PNS being described
2. Controls skeletal muscles
3. Causes dilation of eyes
4. Sends messages via the dorsal root of a spinal
nerves
5. Controls smooth/cardiac muscle
6. Rest & Digest
7. Caused by adrenaline (epinephrine)
8. Can be involuntary or voluntary
9. Caused by acetylcholine
10. Relaxes the bladder
Eye Review- What part is being
described?
1.
2.
3.
4.
5.
6.
7.
8.
White of the eye
Contains the highest # of rods/cones
Controls pupil opening
Provides nutrients to the lens/cornea
Contains no rods/cones
Controls the bending of the lens
Provides nutrients to the eyeball
Opening that allows light to hit the lens