Transcript File - Biology with Radjewski

Nervous System Notes
Part 2
AP Biology 2012
2 Parts to the Nervous System
1. Central Nervous System
– CNS
– Contains the brain and the spinal cord
– Information is transmitted from sensory cells to the
CNS, and from the CNS to effectors, via neurons
2. Peripheral Nervous System
– PNS
– Contains the neurons and their supporting cells
– 2 portions
1.
2.
Afferent – carries sensory information to CNS
Efferent – carries information from CNS to muscles/glands
–
2 divisions
1. Voluntary (conscious movements)
2. Involuntary (autonomic )
Autonomic Nervous System
• ANS
• Controls involuntary functions that are crucial to
homeostasis (heart rate, sweating, digestion)
• 2 divisions
1. Sympathetic – produces fight or flight response,
increased heart rate, bp etc., preparing body for
emergencies
2. Parasympathetic – opposite, slows heart, lowers bp,
increases digestion
Spinal Cord
• Has afferent and efferent tracts of axons
communicating between brain and organs
• Cross section reveals a central area of gray
matter in shape of a butterfly, surrounded by
area of white matter
– Gray matter – rich in cell bodies of spinal neurons
– White matter – rich in myelinated axons that
conduct information up and down spinal cord
• Extend from spinal cord
at regular intervals
• Each nerve has 2 roots
– One connecting with the
dorsal horn of the gray
matter
– One with the ventral
horn
• Afferent (sensory)
axons enter spinal cord
through dorsal root
• Efferent (motor) axons
leave through ventral
root
• Capable of simple
reactions that don’t
involve the brain called
spinal reflexes
Spinal Nerves
Spinal Reflex
• Simplest type has 2 neurons involves with 1
synapse between them – monosynaptic reflex
• Example if knee jerk reflex
Knee Jerk Reflex
•
•
•
•
Dr. taps knee with little hammer,
which stretches the patella
tendon connecting the quadriceps
to the femur in lower leg.
Stretching the muscle generates
action potentials in that sensory
neuron. The axon of the sensory
neuron travels to the spinal cord,
enters the dorsal horn, and
continues to ventral horn where it
synapses onto a motor neuron.
This synapse is excitatory and
causes the motor neuron to fire
action potentials that travel in the
axon of that motor neuron back
out to the quadriceps, causing it
to contract.
Result is that your lower leg kicks
forward
Basic Spinal Reflex
• Information enters the spinal cord from
sensory neurons
• Commands leave the spinal cord through
motor neurons
• All this happens without involving brain
• Spinal reflexes allow rapid responses to
certain simple stimuli and are important in
maintaining posture and balance.
Adult Brain
• 3 major divisions during development
1. Hindbrain
– Produces cerebellum
(controls motor control
and some cognitive
functions
Physiological functions such as
heart beat and breathing
2. Midbrain
3. Forebrain
– Develops into the cerebral hemispheres, thalamus,
hypothalamus and the pituitary
Cerebrum
• Has left and right cerebral hemispheres
• Outermost layer is the cerebral cortex
• Thin layer, but folded into ridges to
increase surface area
• Sensory perception, learning, memory,
and conscious behavior
• Different regions have specific functions
• Most of the cortex is involved in higherorder information processing and is
called the association cortex
Each cerebral hemisphere has 4 lobes
1.
2.
3.
4.
Temporal lobe
Frontal lobe
Parietal lobe
Occipital lobe
Temporal Lobe
• Upper region receives and
processes auditory
information
• Lower regions are involved
with visual processing
• Also involved in recognizing,
identifying, and naming
objects
• Damage to this lobe results in
disorders called agnosias, in
which the individual is aware
of an object but cannot
identify it
Frontal Lobe
• Largest lobe
• Feeling and planning and
contribute to
“personality”
• Damage causes drastic
alterations of personality
and difficulty planning
future events
• The strip of the frontal
lobe cortex that is just
anterior to the parietal
lobe is the primary motor
cortex – control muscles
in specific parts of the
body
Occipital Lobe
• Receives and
processes visual
information
• Essential for making
sense of the visual
world and translating
it into language
• Damage causes
people to not see
motion
Parietal Lobe
• Attends to complex
stimuli
• Helps translate visual
information into a
perception of objects
located in a 3D space
• Behind primary motor
cortex of the frontal
lobe is a strip called the
primary somatosensory
cortex.
– Receives touch and
pressure information
Concept 34.5 Specific Brain Areas
Lateralization
• Phenomenon that language ability resides in
one cerebral hemisphere, the left
• Individuals who suffer damage to the left
hemisphere have some form of aphasia
• Defect in the ability to use or
understand words
• Allowed the identification of two
language areas
• Broca’s area and Wernicke’s area
2 Language Areas
• Broca’s Area
– Located in the frontal
lobe
– Essential for production
of language
– Damage results in poorly
articulated speech or
complete loss of speech,
as well as loss of the
ability to write
– They can still read and
can understand speech
• Wernicke’s area
– Located in the temporal
area
– Essential for
understanding language
– Damage results in loss of
the ability both to read
and to understand
speech
– Patients can still produce
fluent, but nonsensical
speechlike sounds
Learning and Memory can be
localized to specific brain areas
Learning
• Modification of behavior by experience
• Learning that leads to long term memory must
involve long-lasting synaptic changes
– Long Term Potential
• High frequency electrical stimulation of certain
neuronal circuits makes these circuits more sensitive to
subsequent stimulation
• 2 types of learning
– Associative learning
– Observational learning
Associative Learning
• 2 unrelated stimuli become linked to the same
response
• Example is conditioned reflex (Pavlov –
Russian)
– Dog salivates at sight or smell of food (simple
autonomic reflex)
– If he rang a bell before food was presented, after a
few trials, the dog would salivate at the bell even
if no food followed
– Salivation reflex was conditioned
Observational Learning
• Foundation of human intelligence
• 3 elements
1. We pay attention to another person’s behavior
2. We retain a memory of what we have observed
3. We try to copy or use that information
• Creates memories
Optional topics in Ch 34
• Memory
• REM and nonREM sleep
• What is consciousness?