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{Chapter 48 and 49

Neurons and the vertebrate brain

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The Vertebrate Brain

Embryonic Brain Regions

Forebrain Midbrain Hindbrain

Fig. 49-9

Pons (part of brainstem), cerebellum

Forebrain

Midbrain

Hindbrain

Midbrain

Forebrain

Hindbrain

Telencephalon

Telencephalon

Diencephalon

Diencephalon

Mesencephalon

Mesencephalon

Metencephalon

Metencephalon

Myelencephalon

Myelencephalon

Spinal cord

Spinal cord

Cerebrum (includes cerebral cortex, white matter,basal nuclei)

Diencephalon (thalamus, hypothalamus, epithalamus)

Midbrain (part of brainstem)

Medulla oblongata (part of brainstem)

Pituitarygland

Cerebrum

Cerebellum

Central canal

Diencephalon:

Hypothalamus

Thalamus

Pineal gland(part of epithalamus)

Brainstem:

Midbrain

Pons

Medullaoblongata

(c) Adult(b) Embryo at 5 weeks(a) Embryo at 1 month

Human Brain is like 3 brains in one.

Oldest: brain stem

Middle: Cerebellum

Newest: Cerebral cortex/cerebrum

Cerebrospinal Fluid

Clear Colorless Surrounds CNS

Functions: Buffers brain from

skull Buoys brain on

spine Waste products Transport of

hormones

The Brainstem

Consists of: Midbrain Pons Medulla Oblongatta

Functions: Regulation of homeostasis –

breathing, heart rate Swallowing Startle response Autonomic nervous system Coordination of body

movement/balance

Develops from hindbrain Coordination of movement and balance Equilibrium Receives sensory signals – voluntary movement

Joints Muscle length, extension Auditory, visual

Cerebellum

Part of the forebrain Develops into:

Thalamus Hypothalamus (homeostasis, posterior

pituitary gland) Epithalamus (pineal gland, generates

cerebrospinal fluid)

Diencephalon

Develops from forebrain Information processing Olfaction, auditory, visual processing 2 hemispheres

Grey matter – cerebral cortex White matter – internal Basal nuclei – within white matter

Cerebrum

Large in mammals Controls:

Perception Voluntary movement Learning

Highly convoluted High surface area but can still fit in the

skull

Cerebral Cortex

Right and left sides control opposite side of the body

Connected by the corpus collosum Thick band of neurons

Cerebral Cortex

Frontal Lobe Parietal Lobe Occipital Lobe Temporal Lobe

Divisions of Human Cerebral Cortex

Fig. 49-15

Speech

Occipital lobe

Vision

Temporal lobe

Frontal lobeParietal lobe

Somatosensoryassociationarea

Frontalassociationarea

Visualassociationarea

Reading

Taste

Hearing

Auditoryassociationarea

Speech

Smell

Mo

tor

cort

exS

omat

osen

sory

cor

tex

Frontal Lobe

Consciousness Goal setting Inhibition Attention Time perception Judgment Control of emotional

response Internalization of language Memory for habits & motor

activities

Parietal Lobe

Visual attention Touch perception Goal oriented voluntary

movements Manipulation of objects Integration of different

senses to allow for understanding of a single concept.

Vision Visual perception Recognition of printed words

Occipital Lobe

Hearing ability Memory acquisition Some visual Categorization Emotion Language

Temporal Lobe

{

Chapter 48: Neuron Structure and Function

Nerve cells Brain: group of nerve cells

specialized for control of body systems Ganglia (simpler nerve clusters)

Neurons

Motor Neurons From brain to muscle cells

Sensory Neurons Transmit outside signals (from external

stimuli, senses, muscle tension, stimuli within the body ie. Blood pressure) to brain

Interneurons Short, carry signals very short distances Mostly within the brain

Types of Neurons

Fig. 48-3

Sensor

Sensory input

Integration

Effector

Motor output

Peripheral nervoussystem (PNS)

Central nervoussystem (CNS)

Central Nervous System Brain Spinal cord

Peripheral Nervous System Carry information to and from

the CNS

Divisions of the Nervous System

Cell body Dendrites Axon

Axon hillock

Neuron Structure

Fig. 48-4

Dendrites

Stimulus

Nucleus

Cellbody

Axonhillock

Presynapticcell

Axon

Synaptic terminalsSynapse

Postsynaptic cellNeurotransmitter

Junction between an axon and another cell Can be another nerve,

muscle cell Synaptic terminal Neurotransmitters

Synapse

Presynaptic cell Postsynaptic cell

Synapse

Support cells for neurons Nourish Insulate Regulate extracellular fluid

Glial Cells

Action potential Utilize ions, electrical signals to propagate signal down an axon

Neurons are semi-permeable

Neuron Signaling

Neurons are not sending a signal Inside is negatively charged Potassium can pass freely (K+) Sodium (Na+) and Chloride (Cl-) cannot

At rest

Pumps: Na+, K+ ions

Resting potential -70mV

Pumps within the Neuron Membrane

Action Potential Graph

Cell becomes depolarized “spike” in current

Causes resting potential to change from -70mV to closer to 0mV

MUST reach the critical threshold level to fire All or nothing

Creation of an Action Potential

Resting Depolarization Repolarization Hyperpolarization

Major Steps in Action Potentials

Na+ channels CLOSED K+ channels maintain resting potential

Passive

Resting

Na+ channels OPENed by stimulus If potential reaches threshold, will

trigger action potential K+ channels CLOSED Increases internal charge (causes spike)

Depolarization

Na+ channels CLOSE K+ channels OPEN to stabilize

membrane potential

Repolarization

Na+ become unblocked K+ remain open and return membrane to

resting potential

Hyperpolarization

Steps of polarization occur down the neuron

Propagation of the Action Potential

Fig. 48-11-3

Axon

Plasmamembrane

Cytosol

Actionpotential

Na+

Actionpotential

Na+

K+

K+

ActionpotentialK+

K+

Na+

Fig. 48-12a

Axon Myelin sheath

Schwanncell

Nodes ofRanvier

Schwanncell

Nucleus ofSchwann cell

Node of Ranvier

Layers of myelinAxon

Review of Chapter 48 and 49