Psych3 The Biological Basis of Psychology

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Psych3 The Biological Basis of
Psychology Lecture 9Divisions of the Nervous
System
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Lecture 8 Objectives

• Describe the major divisions of the nervous
  system and describe the major distinctions
  between the CNS and the PNS
• Describe the 3 major divisions of the brain and
  provide the names of the subdivisions within each
  division
• Describe where the telencephalon is located
  relative to the diencephalon and describe their
  general roles in behavior
• Describe the two subdivisions of the
  mesencephalon and their general roles in behavior
  
• Describe the two subdivisions of the hindbrain
  and the functions of the medulla, pons and
  cerebellum in behavior
• Describe the three mechanisms in place to protect
  our central nervous system and describe disorders
  that can interfere with this protection
• Describe the function of the area postrema.
• Describe the structure and function of the spinal
  cord.
• Describe the path of travel of sensory and motor
  information in and out of the cord that you
  perceive.
• Describe a spinal reflex in terms of its actual
  definition and the path of travel of sensory and
  motor information.
• Describe the major divisions of the peripheral
  nervous system.
• Describe the general functions and locations of
  the cranial nerves.

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Lecture 8 Objectives

• Describe the somatic nervous system and indicate
  the neurotransmitters and types of receptors
  involved in neural communication
• Compare and contrast the sympathetic versus
  parasympathetic nervous systems in terms of 1)
  function 2) location 3) neuronal organization
  and 4) neurotransmitter/receptor content

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Overview

• Divisions of the nervous system
• The brain
• The spinal cord
• The peripheral nervous system

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Brain
Cranial Nerves
Spinal Cord
Nervous system runs throughout the body and can
be subdivided into a number of parts. There two
regions of high density of neurons brain and
spinal cord.
Spinal Nerves
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The Nervous System
Nervous System
Central Nervous System
Peripheral Nervous System
Definitions Nerves bands of axons in the
PNS Ganglia groups of cell bodies of neurons in
the PNS Tracts bands of axons in the
CNS Nuclei groups of cell bodies of neurons in
the CNS
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Central Nervous System

• Key feature high density of neurons that are
  encased in BONE (protection)

Vertebra encases the spinal cord.
Skull encases the brain.
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Overview

• Divisions of the nervous system
• The brain
• The spinal cord
• The peripheral nervous system

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3 Major Parts of the Brain
Brain
Midbrain Mesencephalon
Forebrain Telencephalon Diencephalon
Hindbrain Metencephalon Mylencephalon
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Forebrain

• Consists of the cerebral cortex (telencephalon)
  and the diencephalon

• Cerebral cortex (named after the bark on a
  tree-also called telencephalon) is the layers of
  cell bodies that lie on the outside most part of
  the brain send axons to other cortical areas and
  to lower brain regions

• is divided up into many regions that serve
  different function (Penfield experiments) and is
  the youngest part of the brain and
  functionally, the most complex

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Cortical Lobes

• The cortex is subdivided into 4 lobes
• Lobes are defined by major grooves or valleys
  called fissures or sulci.
• Lobes are functionally distinct (and will be
  covered later).

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Forebrain

• Consists of the cerebral cortex (telencephalon)
  and the diencephalon

• Diencephalon is a group of subcortical (under
  the cortex) brain regions, each with distinct
  functions.

• Diencephalon contains the forebrain parts of the
  basal ganglia (groups of brain regions involved
  in movement) and the limbic system (groups of
  brain regions involved in learning/memory,
  emotion and motivation-incl. thalamus and
  hypothalamus)

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Midbrain (mesencephalon)

• Consists of the tectum and tegmentum

• Tectum (roof-makes of roof over the brain stem)
• Contains parts of the brain that help guide
  orientation to sights and sounds (colliculus)

• Tegmentum contains the midbrain inputs of the
  basal ganglia and limbic system
• Important for initiation and control of movement
  and for goal-related behaviors
• Contains the cell bodies of the major dopamine,
  norepinephrine and serotonin systems in the brain
  which send axons to all of the forebrain.

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Hindbrain Oldest part of the brain

• Consists of the pons, medulla oblongata and
  cerebellum (mylencephalon and metencephalon)

• Metencephalon
• Pons is involved in sleep and arousal is part of
  the reticular formation (groups of cells that run
  in the midbrain and hindbrain that control
  consciousness)?damage to pons difficulty
  sleeping or waking

• Cerebellum (baby brain) is involved in motor
  coordination and balance?damage to cerebellum
  difficulty walking and loss of balance
  drunkenness

• Myelencephalon Medulla is involved in control of
  essential life processes (heart and respiratory
  function)?damage to medulla death

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Brain Protection Bones and more

• The brain is essential to life (e.g. medulla.)
  and so it is critical that it is protected from
  both the outside and the inside

• 3 major ways that the brain is protected from the
  inside
• Cerebrospinal fluid
• Meninges
• Blood-brain barrier

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Brain Protection CSF

• The brain is literally floating in Cerebrospinal
  Fluid (CSF)

• CSF protects the brain, makes the brain 10 times
  lighter, carries material from the blood to the
  nervous system AND transports wastes out of brain

• CSF travels around the brain just underneath the
  skull and also through the ventricular system
  (within the brain)

FYI stem cells reside in the wall of the
lateral ventricle

• When CSF flow is blocked?hydrocephalus (water on
  the brain)? swelling causes blood vessles to be
  pinched off?dead neurons

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Brain Protection Meninges

• Meninges are very tough membranes that line the
  outside of the brain and spinal cord like peel
  of an orange

• Act as a physical barrier but also produce,
  circulate and absorb cerebrospinal fluid

• Meningitis is an infection of the meninges that
  can lead to pressure on the brain and spinal
  cord?disruption of nervous system function.

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Brain Protection Blood-Brain Barrier

• Unlike other parts of our body, where substances
  (nutrients, drugs, toxins) just pass from the
  blood to the tissue, the brain is protected by
  the Blood-Brain Barrier (BBB) a dense layer of
  blood vessels and cells

• Most larger molecules require a transporter
  protein to cross the BBB (e.g., glucose) but
  fatty-molecules can pass easily (e.g., nicotine
  and heroin-REM the faster a drug can enter the
  brain, the more addictive it is!) acts as a sort
  of filter for the blood

• Not all brain regions are protected by the BBB!
  Regions under the ventricles do not have BBB
  protection.
• Area postrema part of your brain that detects
  toxins and causes you to vomit-wouldnt happen if
  the BBB was there

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Overview

• Divisions of the nervous system
• The brain
• The spinal cord
• The peripheral nervous system

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The Spinal Cord
information super highway of the body
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Spinal Cord

• Cables of neurons (tracts) carries 1. commands
  from the brain to the muscles and organs and
• 2. sensory information from the periphery to the
  brain.

Information (encoded in action potentials)
travels up and down the spinal cord

• Spinal cord string cheese

• Like the brain, the spinal cord is protected by
  bone, meninges and CSF (spinal tap)

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Spinal Cord flow of info

• Nerves are organized into pairs that enter/exit
  between vertebra.

• The axons of sensory neurons enter into the
  spinal cord at the back (dorsal root) and make
  contact with the cell bodies of neurons in the
  dorsal horn of the cord that will carry sensory
  information up to the brain

• Neurons carrying motor information travel down
  from the brain and make contact with the cell
  bodies of motor neurons in the ventral horn of
  the cord. The axons of these motor neurons exit
  out the front of the cord via the ventral root.

Dorsalback (think dolphins have a dorsal fin)
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OUCH!
Spinal Cord Reflexes
Sensory neuron To brain

• Most of the time, our motor neurons are under
  inhibitory control by the brain via our spinal
  cord

Sensory neuron from leg

• In some parts of the spinal cord, the sensory
  neurons connect to the motor neurons via an
  interneuron (in-between neuron)

Interneuron

• When sensory information immediately elicits a
  motor response without the involvement of the
  brainreflex

Motor neuron to leg
Move that leg!
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Lets think.Is it possible to lose sensory
information from your legs without losing the
ability to move your legs? What about vice
versa?
Tumors or injuries can be selective for dorsal or
ventral parts of the cord
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Overview

• Divisions of the nervous system
• The brain
• The spinal cord
• The peripheral nervous system

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Peripheral Nervous System
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Cranial Nerves
12 nerves Enter and leave under the brain (most
in brainstem) Carry sensory motor info Eye,
tongue and facial movements Vision, Hearing,
Taste Swallowing Vagus Nerve (X)control of
organs (calming effect) mixed somatic and
autonomic
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Somatic Nervous System
-sensory neurons carrying information to the
spinal cord -motor neurons carrying information
to muscles
muscle
Acetylcholine (ACh) neurotransmitter of the
somatic nervous system?moves skeletal muscles by
activating nicotinic ACh receptors on muscles
Curare blocks nACh receptors?paralysis
Glutamate neurotransmitter of the somatic
nervous system?conveys sensory information for
majority of modalities to the spinal cord
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Autonomic Nervous System-Function
Sympathetic Nervous System
Parasympathetic Nervous System
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Autonomic Nervous System-Function
Parasympathetic Nervous System
Decreases Pupil Diameter Heart Rate Blood
Pressure Adrenal activity Increases Digestion Sa
livation Tearing Bladder Control Erection (males)
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Autonomic Nervous System-Structure
Cell bodies located at top and very bottom of
spinal cord
Cell bodies located in middle areas of spinal cord
Most terminals in sympathetic ganglia (groups of
cell bodies) ?act as a unit
All terminate either on or near the organ they
control
1 NT system Spinal cord?ganglia
(ACh) Ganglia?organ (ACh) Muscarinic ACh receptors
2 NT system Spinal cord?ganglia
(ACh) Ganglia?organ (NE norepinephrine) ?-adrener
gic receptors
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Lets think.You are in a car accident and your
spinal cord is severed completely at the levels
indicated below. What functions will be lost at
each level?
A. Brain stem All functionsdeath
A
B. All somatic information below the injury
(quadraplegic-both arms and legs) sympathetic
control over breathing, heart rate and digestive
function
B
C
D
C. All somatic information below the injury
(paraplegic-both legs) sympathetic control over
digestive organs
D. All somatic information below the injury
(paraplegic-both legs) parasympathetic control
over bladder and intestines