Transcript Nervous System - Belle Vernon Area School District

Nervous System
Functions
1. Sensory input
2. Integration
3. Homeostasis
4. Mental activity
5. Control of
muscles & glands.
I. Division of the Nervous
System
A. Central Nervous System
(CNS)
1. Brain
2. Spinal cord
B. Peripheral Nervous
System( PNS)
1. Nervous that are
outside the CNS
a. Cranial nerves
b. Spinal nerves
2. Sub divisions of the PNS
a. Sensory (afferent)-conducts action potential from sensory
receptors to the CNS.
b. Motor (efferent) – conducts action potential from CNS to
PNS. (muscle or glands)
a. Somatic - serves sensory nerves,
receptors (skin) sensory organs (head) & motor
nerves that stimulate the skeletal muscle voluntary nervous system
b. Autonomic - automatic
1. Sympathetic - involving
stressful activities
2. Parasympathetic - normal
functioning
II. Nerve Tissue
A. Neuroglia - support & maintain
neurons
1. Schwann Cells - Provide
insulation covering around
large axons.
2. Astrocytes - Anchor neurons
to blood capillaries.
3. Ependymal cells - form &
circulate cerebrospinal fluid.
4. Microglia - phagocytize
invading microorganisms.
5. Oligodendrocytes - insulation
covering around the CNS.
B. Neurons - functional unit of the nervous system
1. Structure
a. Dendrites - receive
b. Cell body - typical to
impulses
other cells
1. Nissl bodies - similar to RER
2. Neurofibrils - network of fine
threads
c. Axon (nerve fiber) - carries impulse
away from the cell body.
1. One axon to every neuron
2. Collaterals – side branches
3. Axon hillock – site of the axon
missing Nissl bodies
d. Myelin sheath - insulating
barrier from a schwann cell
around a axon.
1. Nourishment
e. Neurilemma - cytoplasm &
nuclei of the schwann cell on
the outer covering.
f. Nodes of Ranvier - gaps
where myelin sheaths are
absent.
g. Unmyelinated fibers - gray
matter
h. Myelinated fibers - white
matter
2. Types of Neurons
a. Mutlipolar - many dendrites (signal to muscles).
b. Bipolar 1 dendrtie & axon (eyes, ears, & nose).
c. Unipolar
d. Sensory (afferent) to CNS.
e. Association (interneurons) with in the CNS.
f. Motor (efferent) from CNS.
3. Function
a. Resting potential Polarized -70 mv
-more sodium ions outside
the neuron than inside.
-more potassium ions inside
the neuron than outside.
-this is maintained by the
sodium potassium pump.
-but overall negative due to
the large negative chloride
ions stuck inside.
b. Action potential – (excitable) Nerve impulse + 30 mv
Depolarization – sodium moves into the cell
Repolarization – potassium moves outside the cell.

c. Refractory period - hyperpolarized
- 80 mv. Inside is more
negative .
4. All or None Response
a. Threshold Stimulus
- minimum strength
that can cause an
action potential.
b. Subthreshold cannot initiate a
response.
c. Summation - series
of subthreshold stimuli
can have a cumulative
effect.
5. Transmission of impulse
a. Synapse
b. Presynaptic
c. Postsynaptic
d. Synaptic end bulb
e. Synaptic vesicles
f. Neurotransmitters (50
different)
6. Excitatory vs. Inhibitory
transmissions
a. Excitatory causes a
action potential (more
Na allowed to enter the
postsynaptic)
b. Inhibitory
III. The Central Nervous
System
A. Spinal Cord - Conduction
pathway for impulses
between the brain & the
PNS, reflex center.
Protected by bone, fluid,
membrane.
Compose of gray & white
matter.
Conduction pathway
between the brain &
nerves.
Reflex center 42 cm long.
B. Protective coverings Meninges - membrane
layers.
1. Dura mater - outermost,
thick, & tough.
Epidural space - space
filled with fat between
the bone & dura
matter.
2. Arachnoid - middle layer
of collagen fibers.
Subarachnoid space
filled with
Cerebrospinal fluid
(CSF) - shocking
absorning &
transporting.
3. Pia mater - inner most,
attached to the spinal cord.
C. Structures
1. 31 segments each with a
pair of spinal nerves.
2. Gray Matter - center of the
cord (looks like an H).
a. Posterior Horns terminal endings of
sensory neurons.
b. Lateral Horns - motor
neurons of the
autonomic nervous
system.
c. Anterior Horns - motor
neurons to skeletal
muscle.
3. White Matter - Surrounds
the gray matter
a. Anterior Columns b. Lateral Columnsc. Posterior Columns -
D. Conduction Pathways
1. Ascending Tracts - sensory info to the brain.
2. Descending Tracts - motor info from the brain.
neurons to the effectors.
E. Spinal nerves
1. Mixed nerves because they contain both sensory
and motor neurons.
2. Organizied into regions that they emerge.
C – cervical
T – thoracic
L – Lumbar
S – Sacral
Co – Coccygeal
3. Plexus – nerves come together and separate.
a. three main ones
cervical c1-c4
brachial – c5-t1
lumbosacral – l1-s4
E. Reflex Center
1. Reflex is an extremely rapid
way of responding to an
emergency situation.
a. Receptor at the end of
the sensory neuron.
b. Sensory neuron to the
CNS Associated neuron in
the spinal cord (reflex
center).
c. Motor
2. Types of reflexes
a. Somatic - actions involve
skeletal muscles.
1. Withdrawal – protective
2. Pattellar - knee jerk (2
neurons, sensory to the
motor)
3. Stretch reflex
b. Visceral - smooth &
cardiac to maintain
homeostasis.
1. Breathing,
vomiting,
sneezing, &
coughing
IV Brain - integrative center of the
nervous system
100 billion neurons.
One of the largest internal organs.
A. Protective coverings - Meninges membrane layers.
1. Dura mater - outermost,
thick, & tough.
Epidural space - space filled
with fat between the bone &
dura matter.
2. Arachnoid - middle layer of
collagen fibers.
Subarachnoid space filled with
Cerebrospinal fluid (CSF) shocking absorbing &
transporting.
3. Pia mater - inner most,
attached to the spinal cord
B. Cerebrum “higher brain”- Largest
structure in the brain
1. Cerebral hemispheres
2. Convolutions
Gyri - upwards folds
Sulci - inward folds
3. Fissures
Longitudinal
Transverse
4. Four lobes
a. Frontal – smell,
motivation, aggression,
mood.
b. Parietal – touch, pain,
temperature, balance, taste
c. Occipital – sight
d. Temporal – smell,
hearing, memory
5. Sensory Functions
a. small portion of the sensory input
results in sensation.
b. ascending tracts – sends signals to
the brain.
-each tract is limited ex…
ex. Lateral spinothalamic tract
pain & temperature.
ex. Dorsal column
touch, position, pressure
-most tracts have 2 or 3
neurons to the brain.
-almost all end in the thalamus.
C. Diencephalon – between brain stem & cerebrum
1. Thalamus - relay station for sensory impulses (except smell)
entering the brain.
2. Epithalamus – pineal body (puberty)
2. Hypothalamus - Primary control for the autonomic
nervous system (homeostasis).
a. Thermostat control for body
temp
b. regulates food & water uptake
c. maintain walking & sleeping patterns.
d. associated with emotion (rage,
aggression, sex drives
1. Pituitary glands - endocrine glands
D. Midbrain - reflexes for rapid eye, head & trunk movements
E. Pons - Bridges the cerebrum & cerebellum
F. Medulla Oblongata - part of the brain stem & most inferior
brain structures
1. Cardiac & respiratory center
G. Cerebellum - sends signals to the skeletal muscles
Cranial Nerves
Cranial Nerves
V. Disorders
A. Encephalitis – inflammation of the brain
B. Meningitis – inflammation of the meninges.
C. Rabies – viral disease transmitted by saliva of a animal
bite.
D. Tetanus – bacterial disease that produces a neurotoxin
that affect lower motor neurons in the spinal cord & brain
stem.
E. MS – autoimmune disorder caused by a viral infection
F. Cerebral palsy – general, defects in motor functions from
several types of brain damage or birth related injury.
G. Parkinsons – muscular rigidity, lack of movement
H. Stroke
I. Alzheimer’s disease – mental deterioration (dementia).
J. Epilepsy – group of brain disorders that cause seizures
K. Herpes - shingles
VI. Effects of Aging
A. Natural decline in functioning neurons, including sensory neurons.
(balance loss, coordination, blood pressure, bladder)
B. By the age of 60 up to 50% loss of lower motor neurons in lumbar
region.
(loss of muscle mass & increase fatigue)
C. Size and weight of the brain decreases, but other neurons can
compensate for this loss.
D. Short term (problem solving, thinking) memory decreases slowly
until the age of 60. Afterwards increase rate of memory loss,
especially after 70.
E. Long term memory seems to be unaffected.
F. More time to fall asleep, more walking periods during the night,
and longer amount of time being awake at night.
G. Many older people shoe no change and some show a 10%
increase in thinking ability due to education, health, motivation.