Transcript The Nervous System

Divisions of the
Nervous System
• Central Nervous System
• brain
• spinal cord
• Peripheral Nervous System
• peripheral nerves
• cranial nerves
• spinal nerves
10-1
CNS
PNS
Divisions of Peripheral
Nervous System
Sensory Division
• picks up sensory information and delivers it to the CNS
Motor Division
• carries information to muscles and glands
Divisions of the Motor Division
• Somatic – carries information to skeletal muscle
• Autonomic – carries information to smooth muscle,
cardiac muscle, and glands
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Divisions Nervous System
10-5
Functions of Nervous System
Sensory Function
• sensory receptors gather
information
• information is carried to the
CNS
Integrative Function
• sensory information used to
create
• sensations
• memory
• thoughts
• decisions
Motor Function
• decisions are acted
upon
• impulses are
carried to effectors
10-6
sensory input
motor input
sensory receptor
effector
integration
Types of Neuroglial Cells
Schwann Cells
• peripheral nervous
system
• myelinating cell
Oligodendrocytes
• CNS
• myelinating cell
Microglia
• CNS
• phagocytic cell
Astrocytes
• CNS
• scar tissue
• mop up excess ions, etc
• induce synapse formation
• connect neurons to blood
vessels
Ependyma
• CNS
• ciliated
• line central canal of spinal cord
• line ventricles of brain 10-11
Types of Neuroglial Cells
10-12
Neuron Structure
10-7
Regeneration of A Nerve Axon
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dendrite
cell body
Myelin
sheath axon
Synapse
Na+
Outside cell
-70mV
K+
Inside cell
Myelination of Axons
White Matter
• contains myelinated
axons
Gray Matter
• contains
unmyelinated
structures
• cell bodies, dendrites
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Schwann Cells
Axon
Nodes of Ranvier
Classification of Neurons
Bipolar
• two processes
• eyes, ears, nose
Unipolar
• one process
• ganglia
Multipolar
• many processes
• most neurons of
CNS
Classification of Neurons
Sensory Neurons
• afferent
• carry impulse to CNS
• most are unipolar
• some are bipolar
Interneurons
• link neurons
• multipolar
• in CNS
Motor Neurons
• multipolar
• carry impulses away
from CNS
• carry impulses to
effectors
10-10
Resting Membrane Potential
• inside is negative
relative to the outside
• polarized membrane
• due to distribution of
ions
• Na+/K+ pump
10-14
Potential Changes
• at rest membrane is
polarized
• threshold stimulus
reached
• sodium channels
open and membrane
depolarizes
• potassium leaves
cytoplasm and
membrane repolarizes
10-15
Local Potential Changes
• occur on membranes of dendrites and cell bodies
• caused by various stimuli
• chemicals
• temperature changes
• mechanical forces
• if membrane potential becomes more negative, it has
hyperpolarized
• if membrane potential becomes more positive, it has
depolarized
• graded
• summation can lead to threshold stimulus that starts an action
potential
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Action Potentials
• nerve impulse
• occur on axons
• all-or-none
• refractory period
• absolute - time when threshold stimulus does not start another
action potential
• relative – time when stronger threshold stimulus can start
another action potential
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Action Potentials
10-18
Impulse Conduction
10-19
Ca2+
Presynaptic
neuron
Postsynaptic
membrane
Synaptic vesicles
containing
neurotransmitters
The Synapse
Nerve impulses pass
from neuron to
neuron at synapses
10-21
Synaptic Transmission
Neurotransmitters are
released when impulse
reaches synaptic knob
10-22
Synaptic Potentials
EPSP
• excitatory postsynaptic potential
• graded
• depolarizes membrane of postsynaptic neuron
• action potential of postsynaptic neuron becomes more
likely
IPSP
• inhibitory postsynaptic potential
• graded
• hyperpolarizes membrane of postsynaptic neuron
• action potential of postsynaptic neuron becomes less likely
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Summation of
EPSPs and IPSPs
• EPSPs and IPSPs are
added together in a
process called
summation
• More EPSPs lead to
greater probability of
action potential
10-24
Impulse Processing
Neuronal Pools
• groups of interneurons that make synaptic connections
with each other
• interneurons work together to perform a common
function
• each pool receives input from other neurons
• each pool generates output to other neurons
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Convergence
• neuron receives input from
several neurons
• incoming impulses represent
information from different
types of sensory receptors
• allows nervous system to
collect, process, and respond
to information
• makes it possible for a
neuron to sum impulses from
different sources
10-27
Divergence
• one neuron sends
impulses to several
neurons
• can amplify an
impulse
• impulse from a
single neuron in
CNS may be
amplified to
activate enough
motor units
needed for muscle
contraction
10-28
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Acetylcholine- slows heart rate; PNS
Glutamate- most prevalent neurotransmitter in the brain
Aspartate- in CNS
GABA- inhibitory neurotransmitter
Glycine- inhibitory neurotransmitter
Norepinephrine- awakening from deep sleep tyrosine
Epinephrine- increase heart rate
Dopamine- movement of skeletal muscles
Seratonin- sensory perception, temp regulation, mood,
sleep
Nitric oxide- may play a role in memory and learning
Enkephalin- inhibit pain impulses by suppressing release
of substance P
Substance P- enhances perception of pain
brain
Coverings of the BrainMeninges
skin
skull
dura mater
arachnoid layer
pia mater
cerebral cortex
Menenges:
1.Covers and protects CNS
2.Protects blood vessels and
encloses venus sinuses
3.Contains CSF
4.Forms partition within the skull
Cerebruspinal Fluid
Brain
Ventricles
CSF
Spinal Cord
Rt. Ventricle
Lf. Ventricle
Anterior View
Saggital View
CSF
• 150 ml in adult
• contains: glucose, proteins,lactic acid,
urea, cations, anions, WBC
Functions:
1.Reduces wt. of brain by 97%
2.Prevents head injury
3.Supplies brain with nutrition
4.Transports hormones along
ventricular channels
Cerebrum
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Involved with higher brain functions.
Processes sensory information.
Initiates motor functions.
Integrates information.
Brain has 2 Hemispheres
• Left & Right sides are separate
• Corpus Callosum : major
pathway between hemispheres
• Some functions are ‘lateralized’
– language on left
– math, music on right
• Lateralization is never 100%
Corpus Callosum
Right
Hemisphere
Left
Hemisphere
Right-Left Specialization of
the Cerebrum
left side
• language development
• mathematical & learning
capabilities
• sequential thought processes
right side
• visual spatial skills
• musical and artistic activities
• intuitive abilities
Corpus Callosum
• Major ( but not only) pathway
Medial surface of right hemisphere
between sides
• Connects comparable structures
on each side
• Permits data received on one side
to be processed in both
hemispheres
• Aids motor coordination of left
and right side
Corpus Callosum
Cerebrum Cross-Section
cerebral
cortex
white
matter
corpus
callosum
basal
ganglia
ventricles
Corpus Callosum
• What happens when the corpus callosum is
cut?
• Sensory inputs are still crossed
• Motor outputs are still crossed
• Hemispheres can’t exchange data
Each hemisphere is
divided into 4 lobes
Frontal
Parietal
Occipital
Temporal
Occipital Lobe
Frontal Lobe
Parietal Lobe
The Cerebrum
Temporal Lobe
Brainstem
The Brain
Cerebellum
cerebrum
corpus
callosum
thalamus
Pineal gland
hypothalamus
cerebellum
pituitary
pons
spinal cord
medulla
oblongata
Motor, Sensory & Association Cortex
Frontal Lobe
• Contains primary motor cortex
 No direct sensory input
 Important planning and
sequencing areas
 Broca’s area for speech
 Prefrontal area for
working memory
Frontal
Lobe
Working
Broca’s
Memory
Area
Motor
Cortex
Frontal Lobe Disorders
• Broca’s area
– productive aphasia
• Prefrontal area
– lose track of ongoing context
– fail to inhibit inappropriate responses
• Often measured with the Wisconsin Card
Sorting Task
Parietal Lobe
• Inputs from multiple senses
 contains primary
somatosensory cortex
 borders visual &
auditory cortex
 Outputs to Frontal lobe
 hand-eye coordination
 eye movements
 attention
Somatosensory
Parietal
Cortex
Lobe
Temporal Lobe
 Contains primary
auditory cortex
• Inputs are auditory, visual
patterns
– speech recognition
– face recognition
– word recognition
– memory formation
• Outputs to limbic System, basal
Ganglia, and brainstem
Auditory
Cortex
Temporal
Lobe
Occipital Lobe
• Input from Optic nerve
• Contains primary visual
cortex
– most is on surface
inside central fissure
• Outputs to parietal and
temporal lobes
Occipital
Lobe
Visual
Lobe
Stages of Sleep
The Limbic System
The Limbic System
Thalamus
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Relay center for sensory tracts
from the spinal cord to the
cerebrum.
Contains centers for sensation
of pain, temperature, and touch.
Involved with emotions and
alerting or arousal mechanisms.
Midbrain and Thalamus Function
Hypothalamus
Regulates:
• autonomic control center- blood pressure,
rate and force of heart contraction, center
for emotional response and behavior
• body temperature
• water balance and thirst
• sleep/wake cycles
• appetite
• sexual arousal
• control of endocrine functioning:
Acts on the pituitary gland through the
release of neurosecretions.
Sensory Information sent to
opposite hemisphere
• Principle is Contralateral
Organization
• Sensory data crosses over
in pathways leading to the
cortex
• Visual Crossover
Left visual Right visual
field
field
Optic
nerves
– left visual field to right hemisphere
– right field to left
• Other senses similar
Left Visual Corpus Right Visual
Cortex Callosum
Cortex
Midbrain
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Contains ascending and descending
tracts to the cerebrum and
thalamus.
Reflex center for eye muscles.
Also involved with processing visual
and auditory information (connects
head movements with visual and
auditory stimuli).
Pons
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Connects the two
halves of the
cerebellum.
Regulates breathing.
Medulla Oblongata
• Composed of nerve tracts to
and from the brain (these
tracts cross over left to right
and right to left)
• May be regarded as an
extension of the spinal cord
• Almost all of the cranial
nerves arise from this region
Medulla Oblongata
Contains control centers for
many subconscious activities
• Respiratory rate
• Heart rate
• Arteriole constriction
• Swallowing
• Hiccupping
• Coughing
• Sneezing
Contralateral Motor Control
• Movements controled
Motor Cortex
by motor area
• Right hemisphere
controls left side of
body
• Left hemisphere
controls right side
• Motor nerves cross
sides in spinal cord
Somatosensory Cortex
Cerebellum
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Controls and coordinates
muscular activity.
Important in equilibrium,
posture and movement.
Traumatic Brain Injuries
• Concussion
• Contusion
• Subdural or subarachnoid
hemorrhage
• Contrecoup injury
• Punch Drunk Syndrome
Cerebrovascular Accidents (CVAs)
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Ischemia
Thrombus
Embolism
Arteriosclerosis
Stroke
Stroke
Degenerative brain diseases
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Alzheimer’s
Down’s
Parkinson’s
Huntington’s Chorea
MS
Epilepsy
Schizophrenia
PET Scans
F-Dopa deficiency
Peripheral
Nervous
System
cranial
nerves
- 12 pr
spinal
nerves31 pr
Cranial Nerves
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Cranial Nerves
On Old Olympus Towering Tops A Fat Voracious German Viewed A Hop
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Olfactory- smell
Optic- vision
Oculomotor- 4 of the 6 extrinsic eye muscles
Trochlear- extrinsic eye muscles
Trigeminal- sensory fibers to the face and motor fibers to
the chewing muscles
6. Abducens- controls eye muscles that turn the eye
laterally
7. Facial- facial expression
8. Vestibulocochlear- hearing and balance
9. Glosopharyngeal- tongue and pharynx
10.Vagus- from medulla- acetylcholine slows heart &
breathing
11.Accessory- accessory part of vagus nerve
12.Hypoglossal- moves muscles under tongue
Peripheral Nervous System
Peripheral Nervous System
Skeletal
(Somatic)
Autonomic
Sympathetic
Parasympathetic
The Spinal Cord
The Spinal Cord
white
matter
dorsal root
ventral root
spinal
nerves
grey matter
pia mater
arachnoid
dura
mater
Nerve Pathways into the
Spinal Cord sensory
pathway
motor
pathway
The Spinal Cord
vertebra
spinal cord
spinal nerve
interneuron
motor
neuron
Spinal Reflex
Arc
sensory
neuron motor
neuron
stretch
receptor
patellar
ligament
Spinal Nerves
cervical
cervical
nerves
thoracic
thoracic
nerves
cauda
equina
lumbar nerves
sacral nerves
coccygeal
nerves
Peripheral Nervous System
• 3 kinds of neurons connect CNS
to the body
– sensory
– motor
– interneurons
• Motor - CNS to muscles and
organs
• Sensory - sensory receptors to
CNS
• Interneurons: Connections
Within CNS
Brain
Spinal
Cord
Nerves
Somatic System
• Nerves to/from spinal
cord
– control muscle
movements
– somatosensory inputs
Brain
Sensory
Neuron
• Both Voluntary and reflex
movements
• Skeletal Reflexes
Skin receptors
– simplest is spinal reflex
arc
Motor
Neuron
Interneuron
Muscle
Autonomic System
• Two divisions:
– sympathetic
– Parasympatheitic
• Control involuntary functions
–
–
–
–
–
heartbeat
blood pressure
respiration
perspiration
digestion
• Can be influenced by thought and emotion
Sympathetic Division
neurotransmitter is norepinephrine, fight
or flight
E = exercise, excitement, emergency, and
embarrassment
Parasympathetic Division
neurotransmitter is acetylcholine
D = digestion, deification, diuresis (urinating)
Summary of autonomic differences
Autonomic nervous system controls physiological arousal
Sympathetic
division (arousing)
Pupils dilate
Decreases
Parasympathetic
division (calming)
EYES
Pupils contract
SALVATION
Increases
Perspires
SKIN
Dries
Increases
RESPERATION
Decreases
Accelerates
HEART
Slows
Inhibits
DIGESTION
Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones
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9.
INQUIRY
What voltage is the threshold
potential?
Describe depolarization, repolarization
and hyperpolarization.
What layer of tissue adheres most
tightly to the brain?
CFS stands for-------.
What does it do?
What does the thalamus do?
Where is dark matter located in the
spinal cord?
What disease is characterized by
myelin sheath degeneration?
A thrombus that moves to a new site is
called ----.