The Nervous system

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The Nervous system

• The nerve cell is the basic unit of communication
  in the vertebrate nervous system

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Components of the Nervous System
Figure 11.1
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Three Classes of neurons

• The Neural circuit consists of
• Sensory neurons
• receptor for stimulus
• Interneuron (CNS)
• integrate signals
• Motor neuron
• transfer signal to effector (muscle)

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Types of Neurons in the Nervous System
Figure 11.2
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Anatomy of a Neuron

• Cell body functional portion
• Dendrites short extensions that receive signals
• Axon long extension that transmits impulses

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How does a neuron hold and move info?

• A neuron at rest has a voltage difference across
  the plasma membrane called a resting voltage
  potential
• An action potential (AP) is when this charge
  across the membrane is briefly switched
• The action potential moves down the membrane at a
  rapid pace.
• Ap can move faster over mylenated portions is
  called saltatory conduction

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Myelinated Neuron
Figure 11.7a
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Maintenance of the Resting Membrane Potential
Figure 11.3
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Resting Membrane Potential, Graded Potentials,
and an Action Potential
Figure 11.4
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The Nerve Impulse Is a Bioelectrical Signal

• The sodium-potassium pump uses ATP to transport
  sodium ions out and potassium ions in
• The inside of a resting neuron has a negative
  charge relative to the outside
• An action potential is a reversal and restoration
  of the charge difference across the membrane
• The sodium-potassium pump restores the original
  distribution of ions
• Action potentials are all-or-none events
• A neuron cannot fire during the refractory period

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How does a signal move from one neuron to another?

• A synaptic cleft divides 2 neurons
• The AP will not move across the synaptic cleft
• Neuro transmitters are released by the signal
  cell to the receiver cell
• Move by diffusion

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Transfer of Information from Neuron to Target

• Synaptic transmission
• Release of neurotransmitter graded potential
  achieved
• Effects of neurotransmitter
• Excitatory depolarize postsynaptic cell
• Inhibitory hyperpolarize postsynaptic cell
• Role of postsynaptic neuron integrate and
  process information

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Types of chemical synapse

• Acetylcholine neuromuscular junctions, glands,
  brain and spinal cord
• Norepinepherine affects brain regions concerned
  with emotions, dreaming
• From table 11.1

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The nervous System
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Paths of information flow

• Signals between the brain and spinal cord move to
  the body regions by nerves

• Sensory nerves move a signal towards the brain
  and spinal cord
• Motor neurons move a signal from the brain or
  spinal cord to the body

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Divisions of the nervous System

• Central nervous system
• CNS
• Is the brain and spinal cord

• Peripheral nervous system
• PNS
• all nerves that carry signals to and from the CNS

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Parts of the PNS

• Sensory Division carries info to the brain and
  spinal cord.
• Motor Division carries info from the brain to
  the bodies effectors (things that do the work)

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The Motor division of the PNS has 2 divisions

• Somatic nerves relay commands to and from
  skeletal muscle
• Voluntary control

• Autonomic nerves send signals to and from smooth
  muscles
• Involuntary control
• Sympathetic
• Parasympathetic

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The autonomic divisions

• Parasympathetic
• slow down the body activity when the body is not
  under stress
• Rest and digest

• Sympathetic
• increase overall body activity during times of
  stress, excitement or danger
• fight or flight response
• hormone epinephrine

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Fig 11.12
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Sympathetic and Parasympathetic

• Are Antagonistic
• Work towards the automatic, subconscious
  maintenance of homeostasis.

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Parts of CNS
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Components of the CNS

• Spinal cord
• 31 pair of spinal nerves
• Grey matter
• White matter
• Controls some reflex actions like bladder emptying

• Brain parts
• Hindbrain
• medulla oblongata
• cerebellum
• pons
• Midbrain
• Forebrain
• cerebrum
• thalamus
• hypothalamus

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Ventricles of the Brain and Circulation of
Cerebrospinal Fluid
Figure 11.13
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Brain Major Divisions

• Hindbrain coordinates basic, automatic, vital
  functions
• Medulla oblongata controls automatic functions
  of internal organs
• Cerebellum coordinates basic movements
• Pons aids flow of information
• Midbrain coordinates muscles related to vision
  and hearing

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Brain Processes and Acts on Information

• Forebrain receives and integrates information
  concerning emotions and conscious thought
• Hypothalamus helps regulate homeostasis
• Thalamus receiving, processing, and transfer
  center
• Limbic system neuronal pathways involved in
  emotions and memory
• Cerebrum/cerebral cortex higher functions

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Sleep

• Sleep center reticular activating system (RAS)
• Stages based on electroencephalograms (EEGs)
• Stage 1 transitional, random small waves on EEG
• Stage 2 skeletal muscles relax, little eye or
  body movement, EEG shows sleep spindles

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Sleep (cont.)

• Stage 3 heart and respiration slower, EEG shows
  slow wave sleep
• Stage 4 difficult to awaken, heart and
  respiration slowest, body temperature decreased
• REM (rapid eye movement) sleep dreaming, EEG
  same as awake

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Limbic System Emotions of Fear, Anger, Sorrow,
Love
Figure 11.19
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Memory Storing and Retrieving Information

• Short term working memory, information from
  previous few hours
• Long term information from previous days to years

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Other parts of the CNS

• The two cerebral hemispheres communicate through
  the corpus collosum
• left verbal skills
• right nonverbal skills such as music math,
  abstract
• Brain cavities and Canals
• cerebrospinal fluid surrounds and fills in
  cavities in the brain
• Blood Brain barrier- controls what moves into the
  brain. Will prevent infections.

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Our state of consciousness

• The CNS governs sleeping, dozing, daydreaming and
  full alertness
• neurons of the reticular activating system RAS
  control the changing levels of consciousness by
  releasing serotonin.

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Memory

• Association is the linkage of information to
  structural and chemical changes
• short term- few bits lasts a couple of hours
• Long term- permanent and limitless

• The most important info goes rapidly into long
  term storage
• memory is stored in a form resistant to
  degradation
• Possibly caused by changes in synapses.

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Tips on studying

• Concentrate on what you study.
• Minimize interference.
• Study takes time.
• Break material into smaller portions.
• Rephrase materials in your own words.
• Test yourself to see what you know.

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Primary somatosensory and motor areas of cerebral
cortex
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Disorders of the nervous system

• Trauma
• Infections
• Transmission and synaptic defects.
• Abnormal growth
• Headache
• Tumors
• Stroke

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Psychoactive Drugs

• Action affects higher brain functions
• Psychological dependence user craves the feeling
  associated with the drug
• Tolerance takes more of the substance to achieve
  the same affect
• Addiction the need to continue obtaining and
  using a substance no free choice
• Withdrawal physical symptoms that occur upon
  stopping the drug

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Know what the parts of the brain do

• Brain parts
• medulla oblongata
• cerebellum
• pons
• cerebrum
• thalamus
• hypothalamus

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seratonin
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• Just a reminder to talk about drugs that interact
  with brain.