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Nervous SystemBy: Ms. Wetherington
Review
• What is a neuron?• Synaps?• Synaptic cleft, pre and post synaptic cells• Myelin Cells– CNS: Oligodendrocyte cells– PNS: Schwann cells
Review
• Resting membrane potential = -70mv• Key Point?*– Sodium potassium pump (ATPase) purpose• Restores gradient after action potential
Signaling review
• Electrotonic potential causes cells to have a strong influx of sodium ions– Quickly diffuses to change membrane potential just
slightly– Changes membrane potential just enough to cause
action potential– Impulse propagation: movement of action potential– Refractory periods?– Salatory conduction?
Types of neurons
• Afferent neurons: carry information from PNS to brain or spinal cord (sensory information)
• Efferent neurons: Carry information from brain/spine to PNS
• Intraneurons: local circuits
Nerves
• Single axons only carry so much information– Nervous system bundles many axons together as
nerves• Can be sensory, motor or mixed
Ganglia and Nuclei
• Somas also cluster – PNS known as ganglia– CNS known as nuclei
Central Nervous System: Brain
Brain
• Consistancy similar to gelatin– Protected by???– Integrates sensory, coordination, motor,
movement, cognition
– Mylenation: white matter– Unmyelinated (somas, dendrites, unmyelinated
axons): Gray Matter
Layout
• Forebrain• Midbrain• Hindbrain
Forebrain
• Most recently acquired part of the CNS in terms of evolution
• Broken down into:– Telencephalon (Cerebrum)• Frontal lobe• Parietal lobe• Occipital lobe• Temporal lobe
– diencephalon
Cerebral Cortex
• Highly convoluted gray matter on brain surface (outermost cerebrum)– Deals with memory, attention, awareness,
thought, language, consciousness
– Each lobe is independent but communicate through corpus collosum (made of white matter)
Frontal lobe• Future consequences from current actions• Good and bad• Long term memory (non-task based) - often
emotions• Modifies for fitting into social norms
Parietal lobe
• Sensory information• Manipulation of objects• Reading• speech
Occipital lobe
• Visuals• dreams
Temporal lobe
• Long term memory• Verbal • language
Diencephalon
• Thalamus and hypothalamus– Thalamus: gateway to brain• Sensory information passed through thalamus before
relayed to cortex
Midbrain
• Relay point between more peripheral structures and forebrain
• Passes sensory information and visuals to forebrain from hindbrain
• Returns motor instructions to hindbrain
Hindbrain
• Structures are seen in many organisms • Responsible for involuntary functions
– Cerebellum– Medulla oblongata– pons
Cerebellum
• Quality control agent: error checking– Checks motor signal in agreement with sensory
information coming into the body– Prevents things like falling by adjusting to new
situations• Balance• Prevents you from looking like an idiot
Medulla oblongata
• Homeostasis– Breathing, heart-rate, blood vessel activity,
swallowing, vomiting, digestion
Pons
• Helps out the medulla oblongata by regulating breathing
Arousal and sleep
• Network called reticular formation regulates sleep and arousal– Pons and medulla contain centers that cause sleep
when stimulated– Milk has lots of tryptophan which can be used to
make serotonin….maybe why you get sleepy when you drink it?
Central Nervous System: Spinal Cord
Spinal cord
• Protected by vertebral column and broken into four parts– Cervical– Thoracic– Lumbar– Sacral
Spinal cord• Contains both gray and white matter like the brain• Axons are for both motor and sensory function– Sensory neurons bring information from PNS and enter the
dorsal (back) side of the spine– Motor neurons exit ventrally– Cell bodies (somas) found in dorsal root ganglia
Peripheral Nervous System
PNS
• 12 pairs of cranial nerves and 31 pairs of spinal nerves
• Made up of: – Somatic nervous system (SNS)– Autonomic nervous system (ANS)
Somatic Nervous System
• Voluntary movement– Release of acetylcholine
from nerve terminal onto muscle leads to contraction
– Binding of acetylcholine leads to muscle depolarizing
– SNS also deals with reflexes (doesn’t go to brain)• Monosynaptic and
polysynaptic
Monosynaptic
• Single synapse between sensory neuron and motor neuron (mono)– Knee jerk– Patellar tendon stretched
and sends information up the sensory neuron to the spine where it meets motor neuron to contract quadriceps• Responding to dangerous
situation
Polysynaptic
• At least one interneuron between sensory and motor neuron– Stepping on a tack– Foot jerks (monosynaptic) but you must balance
on the other leg– To stimulate other leg to have downward motion
internurons must provide connection from sensory information on the leg jerk to the opposite leg
Autonomic Nervous System
• Fight or flight response• Rest and digest response– Known as involuntary nervous system
ANS
• Uses cardiac and smooth muscle– Smooth: blood vessels, bronchi, bladder,
gastrointestinal– ANS also controls blood pressure, ventilation,
urination and digestion
ANS
• 2 neuron system (unlike SNS) which play telephone
• 1st neuron = preganglionic• 2nd neuron = postganglionic – Preganglionic soma is in CNS and the axon travels
to a ganglion in PNS– Synapses with post ganglionic neuron to affect
target tissue
Regulation of ANS
• Can regulate individually or coordinate with both parts:– Sympathetic– Parasypathetic
Sympathetic nervous system
• Stress– Fight or flight
BEAR ATTACK!!!!
BEAR ATTACK!!!
• Increase blood flow to heart and skeletal muscles
• Decrease blood flow to GI tract and kidneys• Ensure proper oxygen to muscles• Pupils dilate so you can keep an eye on the
bear as you run
BEAR ATTACK!!!
• Preganglionic neurons use acetylcholine or epinepherine
• Postganglionic neurons use norepinephrine
Parasympathetic nervous system
• Rest and digest
•
MMMMM PIZZA!!!
Pizza time!
• Increase blood flow to digestive and excretion organs
• Decrease blood flow to skeletal muscles and heart
• Heart rate and ventilation rate decrease– Vagus cranial nerve responsible for many
parasympathetic effects in thoracic and abdominal cavity
– Pre and postganglial neurons both use acetylcholine
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