SSYA1013 Chapter 3 biological

7/28/2019 SSYA1013 Chapter 3 biological

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Chapter 3: Biological Processes7th March 2013


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Objectives

Gain a general understanding of thenervous system

Gain knowledge of the structure andfunction of the neuron

Navigate your way around the major brain

areas and understand their function


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Nervous System Hierarchy


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Central nervous system

Brain ~2% of body weight, uses ~20% of resources Composed of bunches of neurons, which form

nerves Spinal cord

Complex tangle of nerves that stretch from

brain to tailbone Collects & transmits info between brain and

peripheral nervous system Also initiates reflexes: automatic responses to

an event


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Peripheral Nervous System

PNS links the CNS to the organs, muscles,and glands of the body

PNS has two parts Somatic (SNS): nerves controlling voluntary

muscle movements

Autonomic (ANS): controls glands, organs,

blood vessels ANS has two parts

Sympathetic: arouses body to prepare for action (fight orflight)

Parasympathetic: slows down body to reserve energy


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Sympathetic and Parasympathetic


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The Neuron

All brain activity originates with theneuron

The messengers of the brain-world These cells receive signals from neurons or

sense organs, process the signals, and sendthem to other neurons, muscles, or organs

Three types Sensory: respond to sensory organ input

Motor: send signals to muscles to controlmovement

Interneurons: the o-between of sensor and


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The Neuron


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The Neuron: Structure

Cell body: houses nucleus Cell Membrane: skin of the cell Axon: cable extending from the cell body

Impulse from cell body travels along axon to its end,where terminal buttons release neurotransmitters(chemical messengers), received by other neurons

Axon is covered by myelin sheath, which is composed

of a fatty substance that helps impulses travel thelength of the axon

Dendrite Branches extending from cell membrane that receive

neurotransmitters from other neurons


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The Dendrite

Increases receptive surface of the neuron

Contacts occur along surface of dendrite


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The Axon

Axon hillock Myelin sheath

Nodes of

Ranvier The pointsjust between

the myelinsheaths


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The Neuron in Action

When a neuron receives impulses fromother neurons, the cell membrane allowsopen exchange of positively and negativelycharged ions Action potential (change in electrical charge)

runs down axon to terminal buttons

This all starts with the axon hillock thegatekeeper of the neuron Terminal buttons release neurotransmitters Neurotransmitters cross the synaptic cleft to

the dendrite of the receiving neuron


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The Neuron in action


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Communication in the Neuron

All-or-nothing The action potential either happens or it doesnt

Non-decremental

Action potentials dont change in amount (voltage) asthey travel

Refractory period Neurons need 2ms to recover before they can

transmit again Threshold

The minimum level of stimulation required to trigger aneural impulse

Once you reach the threshold, the action potentialdoesnt get bigger


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Several Neurotransmitters

Acetylcholine (Ach) Slows down the body, memory, and attention (involved in

Alzheimers disease)

Dopamine (DA) Voluntary movement, attention, and learning; high levels areassociated w/ schizophrenia

Endorphin Reduce sensitivity to pain; linked with pleasure (opiate-like)

Serotonin Arousal, sleep; Prozac increases levels of serotonin

Norepinephrine Helps control alertness and arousal; low levels can depress

mood


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History of Studying the Brain

Franz Joseph Gall (1758 1828) Phrenology

The study of the structure of the skull to

determine a persons character and mental capacity 26 organs on the surface

of the brain


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Phrenological

Map of the Skull


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Flourens (1794 1867) Emphasized the importance of experimental

research of the brain

Carefully controlled experiments on animals todetermine localities of brain and theirfunctions

Moved the field of brain research into a morescientific arena


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The Brain

Three main parts Brain Stem

Limbic System Cerebral Cortex


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Areas of the Brain


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Brain Stem

Region of the brain where the spinal cordenters the skull and swells

Medulla Regulates heart-rate, breathing, blood

pressure, and motor movements

Cerebellum Controls skilled motor movements


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Brain Stem

Pons Connects the two hemispheres of the

cerebellum

Reticular formation Sleep (Moruzzi & Magoun, 1961)

Attention

Thalamus Relay center

Filters & organizes information from senses


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Limbic System

Hypothalamus Feeding Reproductive behavior Temperature (Barbour, 1912)

Hippocampus Memory

H.M. Amygdala

Feeding Memory Emotion


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Cerebral Cortex

Two halves, four lobes Frontal lobe

Motor cortex

Parietal lobe Sensory cortex

Prosopagnosia Unilateral neglect

Temporal lobe Auditory areas

Occipital lobe Visual areas


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Two Cerebral Hemispheres

Contralateral arrangement

Corpus callosum

Thick band of nerve fibers connecting thehemispheres

Its how the 2 hemispheres communicate

Right-brained vs. left-brained?

OR


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Left & Right Functions


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Preserve Your Brain

This is a normalbrain firing

This is a brainthat has done

too much ecstasy

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SSYA1013 Chapter 3 biological