The Brain & Learning (CH 48)-Day 6
• Take notes on the following information!
• All animals except sponges have a nervous system.
• What distinguishes nervous systems of
different animal groups is how neurons are
organized into circuits.
Chordates
Echinoderms
Arthropods
Roundworms
Annelids
Mollusks
Flatworms
Radial
Symmetry
Cnidarians
Pseudocoelom
Radial
Symmetry
Sponges
Protostome Development
Three Germ Layers;
Bilateral Symmetry
Deuterostome
Development
Coelom
Tissues
Multicellularity
Single-celled
ancestor
The animal kingdom
Organization of Nervous Systems
• The simplest animals with nervous systems, the
cnidarians, have neurons arranged in nerve nets
The cnidarians, have neurons arranged in nerve nets
Radial
nerve
Nerve net
Hydra (cnidarian)
Nerve
ring
Sea star (echinoderm)
Sea stars have a nerve net in each arm connected by radial
nerves to a central nerve ring
•simple cephalized animals, such as flatworms,
•have a central nervous system (CNS)
Eyespot
Brain
Brain
Nerve
cord
Transverse
nerve
Planarian (flatworm)
Ventral
nerve cord
Segmental
ganglion
Leech (annelid)
Annelids and arthropods have segmentally arranged
clusters of neurons called ganglia.
These ganglia connect to the CNS and make up a
peripheral nervous system (PNS).
Ganglia
Brain
Ventral
nerve cord
Segmental
ganglia
Insect (arthropod)
Anterior
nerve ring
Longitudinal
nerve cords
Chiton (mollusc)
In vertebrates, the central nervous system consists of a
brain and dorsal spinal cord.
The PNS connects to the CNS.
Brain
Brain
Ganglia
Squid (mollusc)
Spinal
cord
(dorsal
nerve
cord)
Sensory
ganglion
Salamander (chordate)
Information Processing
Nervous systems process information in three stages:
sensory input, integration, and motor output
Integration
Sensory input
Sensor
Motor output
Effector
Peripheral nervous
system (PNS)
Central nervous
system (CNS)
• Sensory neurons transmit information from
sensors that detect external stimuli and internal
conditions
• Sensory information is sent to the CNS, where
interneurons integrate the information
• Motor output leaves the CNS via motor
neurons, which communicate with effector cells
• The three stages of information processing are
illustrated in the knee-jerk reflex
Quadriceps
muscle
Cell body of
sensory neuron in
dorsal root
ganglion
Gray
matter
White
matter
Hamstring
muscle
Spinal cord
(cross section)
Sensory neuron
Motor neuron
Interneuron
Neurons have a wide variety of shapes
that reflect input and output interactions
Dendrites
Axon
Cell
body
Sensory neuron
Interneurons
Motor neuron
Central nervous
system (CNS)
Brain
Spinal cord
Peripheral nervous
system (PNS)
Cranial
nerves
Ganglia
outside
CNS
Spinal
nerves
Brain Cells are Neurons...
Dendrites
Cell body
Nucleus
Axon hillock Axon
Presynaptic cell
Signal
direction
Synaptic
Myelin sheath terminals
Synapse
Postsynaptic cell
•
•
•
•
cell body: contains nucleus & organelles
dendrites: receive incoming messages
axons: transmit messages away to other cells
myelin sheath: fatty insulation covering axon,
speeds up nerve impulses
• synapse: junction between 2 neurons
• neurotransmitter: chemical messengers sent
across synapse
• Glia: cells that support neurons
– Eg. Schwann cells (forms myelin sheath)
Supporting Cells (Glia)
• Glia are essential for structural integrity of the
nervous system and for functioning of neurons
• Types of glia: astrocytes, radial glia,
oligodendrocytes, and Schwann cells
In the CNS, astrocytes provide
structural support for neurons and
regulate extracellular concentrations of
ions and neurotransmitters
Green cells are
the astrocytes.
Blue stains the nucleus.
Oligodendrocytes (in the CNS) and
Schwann cells (in the PNS)
form the myelin sheaths around
axons of many vertebrate neurons.
Nodes of Ranvier
Layers of myelin
Axon
Schwann
cell
Axon
Myelin sheath
Nodes of
Ranvier
Schwann
cell
Nucleus of
Schwann cell
0.1 µm
Synapse….
• SYNAPSE: where a nerve
cell touches another nerve
cell (or muscle cell, etc).
• Brain uses synapse to
send/receive signals
Central Nervous System
• Brain and spinal cord
• Cavities are filled with cerebrospinal fluid
– cushions and supplies nutrients and white blood cells.
– Meninges are layers of connective tissue surrounding
the brain and spinal cord
• White matter is myelinated; gray matter is not.
• Evolutionarily older structures in the brain regulate
essential functions.
Peripheral Nervous System
Cranial nerves originate in the
brain and terminate mostly in
organs of the head and upper
body.
Spinal nerves originate in the
spinal cord and extend to parts of
the body below the head
The PNS has two functional
components: the somatic and
autonomic nervous systems
Peripheral Nervous System
• Somatic nervous system (PNS):
– Voluntary (conscious control)
– Carries signals to skeletal muscles
• Autonomic nervous system (PNS)
– Involuntary
– Smooth and cardiac muscle, GI , cardio, excretory
and endocrine organs
MOTOR DIVISION
Peripheral
nervous system
Somatic
nervous
system
carries signals to
skeletal muscles
Sympathetic:
speeds up
everything
but digestion
“fight or flight”
adrenaline
Autonomic
nervous
system
Sympathetic
division
regulates the internal environment
in an involuntary manner
Parasympathetic
division
Enteric
division
Parasympathetic calms
everything but digestion
PNS Divided into 2 Parts
• Sympathetic division
– speeds up everything but digestion
– “fight or flight”
– adrenaline
• Parasympathetic division
– calms everything but digestion
Embryonic Development of the Brain
All vertebrate brains develop from three embryonic regions:
forebrain, midbrain, and hindbrain
Brain structures present in adult
Embryonic brain regions
Telencephalon
Cerebrum (cerebral hemispheres; includes cerebral
cortex, white matter, basal nuclei)
Diencephalon
Diencephalon (thalamus, hypothalamus, epithalamus)
Forebrain
Midbrain
Mesencephalon
Midbrain (part of brainstem)
Metencephalon
Pons (part of brainstem), cerebellum
Myelencephalon
Medulla oblongata (part of brainstem)
Hindbrain
Mesencephalon
Metencephalon
Cerebral hemisphere
Diencephalon:
Hypothalamus
Thalamus
Midbrain
Hindbrain
Diencephalon
Myelencephalon
Pineal gland
(part of epithalamus)
Brainstem:
Midbrain
Pons
Spinal cord
Forebrain
Telencephalon
Pituitary
gland
Medulla
oblongata
Spinal cord
Cerebellum
Central canal
Embryo at one month
Embryo at five weeks
Adult
BRAIN
This white matter is distinguishable from gray matter,
which consists mainly of dendrites, unmyelinated axons,
and neuron cell bodies
Gray matter
White
matter
Ventricles
BRAIN in the CNS has different parts.
Brainstem
Hindbrain
Pons
Medulla oblongata
HOMEOSTASIS……
breathing,
heart activity,
swallowing, vomiting,
digestion;
most ascending axons
cross over here
Cerebellum
coordination and motor learning
Cerebrum
• Right and left hemispheres connected by corpus
callosum
Cerebral cortex (gray matter) is the largest
and most complex part of the mammalian brain
Cerebrum
Cerebrum
Frontal lobe: speech, personality, motor cortex
Parietal lobe: somatosensory cortex, speech, taste,
reading
Temporal lobe: hearing, smell
Occipital lobe: vision
Language and Speech
• Brocca’s area
– Frontal lobe
– Patients with injury can understand language but
not speak
• Wernicke’s area
– Temporal lobe
– Patients with injury can speak but not
comprehend
Diencephalon
Hypothalamus
Thalamus
Pituitary gland
Hypothalamus: homeostasis by regulating
hunger, thirst, temp., circadian rhythms
Pineal gland
Thalamus: relay center
Circadian Rhythms
• The hypothalamus also regulates circadian
rhythms such as the sleep/wake cycle
• Animals usually have a biological clock, a pair
of suprachiasmatic nuclei (SCN) in the
hypothalamus
• Biological clocks usually require external cues
to remain synchronized with environmental
cycles
PET scan
Magnetic resonance images (MRI)
The limbic system: emotions and memory including olfaction
Memory and Learning
• The frontal lobes are a site of short-term
memory
• They interact with the hippocampus and
amygdala to consolidate long-term memory
• Many sensory and motor association areas of
the cerebral cortex are involved in storing and
retrieving words and images
Learning
• How does an organism learn about it’s
environment?
– Taxis: purposeful movement
• Toward stimulus = + taxis
• Away from stimulus = - taxis
– Kinesis: random movement
• Hoping for the best
Cognition
• Cognition means to know/learn and that you
are being aware.
– Environment + genes
• Metacognition = aware of how you learn
– Learning Styles
Diagram of Brain
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•
•
•
•
•
Tap into your creative side using pictures, sketches and words to form a collage in
each section of the brain to represent the functions of these lobes.
Frontal lobe -- Involved with planning, interpretation, emotions, personality,
deliberate movements, decision making, and turning thoughts into words.
Parietal lobe -- Perceives sensory inputs and and also associates these inputs with
past memories.
Temporal lobe -- Deals with the senses of smell and sound and also is responsible for
forming memories.
Occipital lobe -- Decodes images and objects that are seen in order to identify or
recognize them.
Cerebellum -- Regulates movement, balance and coordination.
– For example, in the frontal lobe section, drawings of people smiling, crying or
communicating can be utilized.
– In the parietal lobe section, images representing the five senses can be pasted.