Overview of NS

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BIO301 Intro to Neuroscience
Overview of the Structure &
Function of NS
Overview of NS
•The nervous system as coordinator of
responses
•Organization of NS
–Anatomical vs Functional (physiological)
•General Functions of NS
•Foreshadowing the semester:
–Gross anatomy
•B‘stem, midbrain, cerebrum, cerebellum, deep brain areas
–Other areas.
Overview of NS
•The general function of the nervous system is to coordinate
& control all body systems based on environmental cues.
food
predator
Overview of NS
•The nervous system as coordinator of
responses
–The brain uses electrical impulses to activate or
deactivate all the cells to help make a smooth and
coordinated response to environmental stimuli.
•What the nervous system does.
–Senses what is happening in the external and internal environment
–Determines if that stimulus is important. If it’s important then how
best to respond to it
–Coordinates appropriate body systems to cause the appropriate
response.
Nervous System Organization
• Anatomical Classification (two major groups):
– Central Nervous System (CNS) = brain & spinal cord
– Peripheral
Nervous System
(PNS) = nerves
that extend from
the brain (cranial
nerves) and spinal
cord (spinal
nerves).
– Somatic vs
autonomic
– FITB
Nervous System Organization
• Functional Classification (two major groups)…
1. Sensory (CNS & PNS)
2. Integrative (CNS)
3. Motor (CNS & PNS)
Nervous System Organization
• Functional Classification (two major groups):
1. Sensory
–Three Divisions:
• Visceral afferent
(usually
subconscious)
• Somatosensory
afferent
(conscious)
– =“body sense”:
pain, touch,
temperature,
proprioception
• Special senses
(vision, hearing,
taste, smell)
Nervous System Organization
•Functions of Neurons (two major):
1.Afferent division (much more info in sensory section!)
•Carries information to the CNS
–Sensory receptors
(located at the ends
of peripheral
neurons) detect
changes (i.e. are
stimulated)
occurring in their
surroundings;
–Sensory receptors
transmit a sensory
impulse to the CNS.
–A sensory impulse is
carried on a sensory
(afferent or
ascending) neuron.
Nervous System Organization
• Functional Classification (two major groups):
–Integrative (CNS)
– interpretation of an
incoming sensory
impulse (i.e. decision is
made concerning what's
going to happen next,
based on sensory
impulse).
– Integrating afferent
information and
formulating an efferent
response
– Higher mental functions
associated with the
“mind”
– A motor/effector impulse
begins...
Nervous System Organization
• Functional Classification (two major groups):
–Motor – Two Divisions
– Somatic NS –
voluntary control of
skeletal muscle
– Autonomic NS involuntary control
of organ systems.
• Sympathetic NS –
fight or flight
• Parasympathetic
NS – rest and
digest.
Nervous System Organization
•Functions of Neurons (two major):
1.Efferent division - Carries information from the CNS
–involves the
response of a body
part;
–Motor impulses are
carried from CNS to
responsive body
parts called effectors;
–Effectors = 2 types:
•muscles
•glands
–A motor impulse is
carried on a motor
(efferent or
descending) neuron
Nervous System Organization-Review
•Anatomy:
–Central nervous system (CNS)
–Peripheral nervous system (PNS)
• For more detailed information: HERE
•Function
And HERE
–Afferent division
•Key words: __________, ____________
–Efferent division
•Key words: ___________, _____________
Central
nervous
system
(CNS)
Brain
(Input to CNS
from periphery)
Somatic
sensory
(Output from CNS
to periphery)
Peripheral
nervous
system
(PNS)
Afferent
division
Sensory
stimuli
Spinal
cord
Visceral
stimuli
Efferent
division
Somatic
nervous system
Motor
neurons
Autonomic
nervous system
Sympathetic
nervous system
Parasympathetic
nervous system
special
sensory
Smooth muscle
Cardiac muscle
Glands
Effector organs
(made up of muscle
and gland tissue)
Skeletal
muscle
Fig. 5-1, p. 132
Functional Classes of Neurons – sequence of
transmission
Central Nervous System – in General
•Enables you to:
–Subconsciously regulate your internal
environment by neural means
–Experience emotions
–Voluntarily control your movements
–Be consciously aware of your own body
and your surroundings
–Engage in other higher cognitive processes
such as thought and memory
http://www.functionalmri.org
/
Central Nervous System –
Amazing Numbers
•~100-200 billion neurons in infancy.
–All neurons present at birth; but not all are mature and interconnected
–Myelination (process aiding nerve conduction) not complete until 10-12
years
•Each neuron can have up to 10,000 connections (synapse)
•Do the math…. 200 billion neurons x 10,000 connection
points per neuron = 2000000000000000 (215) connections.
–But those connections can be rearranged as we learn.
–That equates to 1024 possible connects (that’s 1 million, million, million, million).
Brain Anatomy
• Brain components
– Brain stem
– Forebrain
• Diencephalon
–Hypothalamus
–Thalamus
• Cerebrum
– Cerebral cortex
– Cerebellum
Brain Stem – overview
• Continuous with spinal cord
• Controls many basic, life-sustaining
processes, such as respiration, circulation,
and digestion
• Consists of
–Midbrain
–Pons
–Medulla
Brain Stem – overview
•Functions
–Most of cranial nerves arise from brain stem
–Neuronal clusters within brain stem control heart
and blood vessel function, respiration, and many
digestive functions
–Plays role in regulating muscle reflexes involved in
equilibrium and posture <covered later>
–Reticular activating system (formation) within brain
stem receives and integrates all incoming sensory
synaptic input <later>
–Centers that govern sleep are in brain stem <later>
Hypothalamus
•Brain area most involved in directly regulating
internal environment stability (another word for
this???)
•Functions (master gland)
–Controls body temperature
–Controls thirst and urine output
–Controls food intake
–Controls anterior pituitary hormone secretion
–Produces posterior pituitary hormones
–Controls uterine contractions and milk ejection
–Serves as a major ANS coordinating center
–Plays role in emotional and behavioral patterns
–Participates in sleep-wake cycle (promotes slow
Hypothalamus
wave sleep)
Thalamus
• Part of diencephalon
• Serves as “relay station” and synaptic integrating center
for processing sensory input on its way to cerebral cortex
–“gateway to the cortex”
• Helps in focusing on stimulation of interest
• Capable of crude awareness of various types of sensation
but cannot distinguish their location or intensity
Deep Brain Areas - Basal Nuclei
• Act by modifying ongoing activity in motor pathways
• Primary functions
–Inhibiting muscle tone throughout the body
– gatekeeper of motor output  later lectures (motor
output)
Limbic System
• Includes portions of the
hypothalamus and other forebrain
structures (frontal lobe,
hippocampus)
• Responsible for
– Emotion
– Basic, inborn behavioral
patterns related to survival
and perpetuation of the species
– Plays important role in
motivation and learning
• memory
Cerebrum
•Highly developed
•Makes up about 80% of total brain weight (largest
portion of brain)
•Outer surface is highly
convoluted cerebral
cortex
–Highest, most complex
integrating area of the brain
–Plays key role in most
sophisticated neural
functions
Cerebral Cortex
•Each half of cortex divided into four major
lobes
–Occipital
–Temporal
–Parietal
–Frontal
Cerebral cortex
• Occipital lobe
–Carries out initial processing of visual input (more details
later…)
• Temporal lobe
–Initial reception of sound sensation (more details later…)
• Parietal lobe
–Somatosensory processing
• Frontal lobe
–Responsible for
• Voluntary motor activity
• Speaking ability
• Elaboration of thought
• Personality/Mood/Emotion
Cerebral Cortex – language
• Primary areas of cortical
specialization for
language
–Broca’s area
•Left frontal lobe
•Governs speaking ability
–Wernicke’s area
•Left parietal, temporal,
occipital lobe junction
•Concerned with language
comprehension (spoken
and written)
Cerebellum
•Attached at top rear portion of brain stem
•Maintains proper position of the body in space
•Subconscious ___________ of motor activity
(movement)
•Important in balance and in planning and
executing voluntary movement
Spinal Cord
•Two vital functions
–Neuronal link between brain and PNS
–Integrating center for “spinal reflexes”
Major Functions Overview
1. Sensory perception
2. Voluntary control of movement
3. Language
4. Personality traits
5. Sophisticated mental events, such as thinking memory,
decision making, creativity, and self-consciousness
1. Inhibition of muscle tone
2. Coordination of slow, sustained movements
3. Suppression of useless patterns of movements
1. Relay station for almost all sensory input
2. Crude awareness of sensation
3. Some degree of consciousness
4. Role in motor control
1. Regulation of many homeostatic functions, such as temperature
control, thirst, urine output, and food intake
2. Important link between nervous and endocrine systems
3. Extensive involvement with emotion and basic behavioral patterns
1. Maintenance of balance
2. Enhancement of muscle tone
3. Coordination and planning of skilled voluntary muscle activity
1. Origin of majority of peripheral cranial nerves
2. Cardiovascular, respiratory, and digestive control centers
3. Regulation of muscle reflexes involved with equilibrium and posture
4. Reception and integration of all synaptic input from spinal cord;
arousal and activation of cerebral cortex
5. Role in sleep-wake cycle
Brain component
Cerebral cortex
Basal nuclei
Thalamus
Hypothalamus
Cerebellum
Brain stem
(midbrain, pons,
and medulla)
Table 5-2, p. 141
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