Neuroscience

Dr. Irene Karayianni

The Neuron

Shapes of neurons

Multipolar neuron one axon and many dendritic branches

Bipolar neuron one axon and one dendritic branch

Usually sensory

Unipolar neuron one axon and one dendritic branch

Usually sensory

Pyramidal neuron shape of their cell body, looks like a pyramid. They

have one axon and two main dendrite branches

Purkinje neuron one axon and a very dense and complicated

dendrite arrangement Found in the cerebellum, the part of the brain that

controls balance, coordination, and timing of actions.

Specialized to be good at different things

Neuron structure

1 Cell body (soma) 2 Nucleus – incorporated hereditary material 3 Dendrites 4 Axon 5 Terminal buttons 6 Myelin sheath – protective coat of protein & fat; insulates, serves to increase

velocity 7 Schwann’s cells

1 2

3 4

5

6 7

(transmit messages)

(receive messages)

Glial cells support neural functioning

Hold neurons in place; nourishment; insulation; help repair damage

Types of neurons

• Sensory neuron: takes a message from a receptor in a sense organ to

the CNS. Long dendrite, short axon

• Motor neuron: takes message from CNS to a muscle or a gland. Short

dendrite, long axon.

• Interneuron: connector neuron, conveys messages between parts of the

CNS. Short dendrites, short/long axon.

Neural networks

Neurons are…

&

With built-in supplies of electrical power

Neuron communication

1 Neural transmission electrical

2 Synaptic transmission chemical

https://www.youtube.com/watch?v=-SHBnExxub8

How neurons fire

All-or-none law

Resting state Inside Negative charge -70 millivolts

Action potential Inside Positive charge

Communication within neuron electrical impulse

Communication within neuron electrical impulse

Polarity

(charge difference)

Before the neuron is triggered

Resting state

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Communication within neuron electrical impulse

Action potential

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++++++++++++++++

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- - - - - - - - - -

- - - - - - - - - - -

Gates open

Depolarization chain of events

Communication within neuron electrical impulse

Action potential

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++++++++++++++++

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- - - - - - -

- - - - - - - -

- - -

- - -

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the movement of ions causes a change in charge from negative

to positive in successive sections of the axon

Communication within neuron electrical impulse

Just after an AP has passed through a section of the axon

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++++++++++++++++

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- - - - -

- - - - - -

- - - - -

- - - - -

Reload

Gates closed

Communication within neuron electrical impulse

Differences in

SPEED (3-360 km/h) - determined by axon’s size and thickness of myelin sheath

STRENGTH - potential rate of firing (up to 1000 times/sec) – depends on intensity of stimulus

Mirror neurons .

understand others’ intentions

capacity of young children to imitate others

empathy— concern, compassion, sympathy

development of language

The synapse

The synapse

The synapse

The synapse

• several types of NTs, and not all neurons are capable of receiving

the chemical message carried by a particular NT

• each kind of neurotransmitter has a distinctive configuration that

allows it to fit into a specific type of receptor site on the receiving

neuron

Excitatory and inhibitory messages

Reuptake

If neurotransmitters remained at the site of the synapse, receiving neurons would be awash in

a continual chemical bath, producing constant stimulation or constant inhibition

Deactivation by enzymes

Or

Chemical recycling

Neurotransmitters >100

Serotonin and Endorphins

Technically, the only things you enjoy

NTs are a particularly important link between the nervous system and

behavior

Deficiency or excess

Neurotransmitters . .

• Acetylcholine: activates skeletal muscles (The paralytic arrow-poison curare

acts by blocking transmission at these synapses). Also involved in memory, and

diminished production may be related to Alzheimer’s

• Glutamate: memory, regulation of emotion

• GABA: the primary inhibitory neurotransmitter. It moderates a variety of

behaviors, ranging from eating to aggression. Several common substances, such

as the tranquilizer Valium and alcohol, permit GABA to operate more efficiently.

• Dopamine: movement, attention, focus, learning. Linked to pleasures related

to motivation and emotional arousal. Dopamine deficiency is linked to

Parkinson’s. Dopamine overproduction is linked to schizophrenia

• Serotonin: regulates sleep, eating, carbohydrate cravings, mood, temperature,

and pain. Linked to alcoholism, depression, suicide, impulsivity, aggression, and

coping with stress

• Endorphin: similar to painkiller morphine. Deals with pain, elevates mood.

• Norepinephrine: focus, alertness

• Epinephrine: fight or flight

https://www.youtube.com/watch?v=haNoq8UbSyc

Neural connections

Each neuron can be connected to 80.000 other neurons

MANY neural connections

Messages are also communicated by chemicals in the endocrine system

Nervous system

Central nervous system

Peripheral nervous system

Thickness of a pencil

Communication

Reflexes

Reflexes - Types of neurons

• Sensory neuron: takes a message from a receptor in a sense organ to

the CNS. Long dendrite, short axon

• Motor neuron: takes message from CNS to a muscle or a gland. Short

dendrite, long axon.

• Interneuron: connector neuron, conveys messages between parts of the

CNS. Short dendrites, short/long axon.

Quadriplegia

Paraplegia

Peripheral NS

Autonomic NS

The autonomic division plays a crucial role during emergencies

The sympathetic and parasympathetic divisions work together to

regulate many functions of the body

The endocrine system

• A chemical communication network that sends messages throughout the

body via the bloodstream.

• Secretes hormones, chemicals that circulate through the blood and

regulate the functioning or growth of the body.

– travel slower than neurotransmitters

– travel throughout the body, similar to the way radio waves are transmitted -

cells must be receptive

• Influences—and is influenced by—the functioning of the nervous system.

• Closely linked to the hypothalamus.

Pituitary (hypophysis): key component of ES

growth, blood pressure, certain functions of

the sex organs, thyroid glands and

metabolism, some aspects of pregnancy,

childbirth, nursing, water/salt concentration,

temperature regulation, pain relief.

Master gland, but servant of the brain

Endocrine system

and glucagon

cortisol

Hormones

Oxytocin:

• in new mothers, oxytocin produces an urge

to nurse newborn offspring.

• Stimulates cuddling

• in rats—it encourages males to seek out

females more passionately, and females to

be more receptive to males’ sexual

advances.

• Related to the development of trust in

others

The brain

3D BRAIN http://www.g2conline.org/

greatest natural marvel

1.5 kg

biocomputer

No straightforward one-to-one correspondence

exists between a distinct part of the brain and a

particular behavior

Studying the brain

Studying the brain

Electroencephalogram (EEG)

records electrical activity in the brain

Studying the brain

Functional magnetic resonance imaging (fMRI)

changes in blood oxygenation and flow

able to view features of less than a millimeter in size and view changes

occurring in intervals of 1∕10 of a second

shows operation of individual bundles of nerves

Improved diagnosis of diseases (chronic back pain – stroke – Alzheimer’s, MS)

Studying the brain

Positron emission tomography (PET)

biochemical activity within the brain at a given moment

injection of a radioactive liquid into the bloodstream, which makes its

way to the brain

Memory problems, brain tumors

Studying the brain . .

Transcranial magnetic stimulation (TMS)

exposes a region of the brain to a strong magnetic field momentary

interruption of electrical activity note the effects of this interruption

on normal brain functioning

Virtual lesion

Treat several disorders (depression, schizophrenia)

The old brain – the central core

• We share some basic functions with more

primitive animals

• directed by a relatively primitive part of

the brain

The old brain – the central core

reticular formation the brain’s guard. It arouses the

cerebral cortex to attend to new

stimulation and keeps the brain alert

even during sleep.

1. Hindbrain: Medulla, pons, cerebellum

The old brain – the central core

• Regulates unconscious function: breathing,

reflexes, heartbeat, blood pressure,

circulation, digestive system activity,

vomiting

• People who experience brain damage can

still have functioning bodies, as long as the

medulla oblongata is working.

• Damage: fatal / unable to breath, swallow

medulla

The old brain – the central core

• Contains large bundles of nerves

• Joins 2 halves of cerebellum

• Sleep regulation

• Transmits motor information

– Coordinates muscles, integrates movement

between right and left part of the body

• Involved in eye movements, facial

expressions, chewing, feeling the face,

biting, swallowing

– Important nerves originate in the pons

pons

The old brain – the central core

• Latin for ―little brain‖

• Contains half the brain's neurons

• Coordinates bodily movements, posture, and

body balance

– important for learning motor behaviors

– Damage to the cerebellum interrupts the flow

of smooth movement, causing it to appear

uncoordinated

• Involved in several intellectual functions,

ranging from analysis and coordination of

sensory information to problem solving

cerebellum

The old brain – the central core

2. Reticular formation

reticular formation Sleep, arousal, attention; the brain’s guard. It arouses

the cerebral cortex to attend to new stimulation. filters

out background stimuli to allow us to sleep undisturbed

necessary for maintenance of consciousness - coma

The old brain – the central core

3. Thalamus, hypothalamus

reticular formation the brain’s guard. It arouses the

cerebral cortex to attend to new

stimulation. filters out background

stimuli to allow us to sleep undisturbed

The old brain – the central core

• relay station for information about the

senses

– channels incoming stimuli from the sense

organs to the appropriate parts of the brain so

that it can be processed

– Messages from the eyes, ears, and skin

• integrates information from higher parts of

the brain, sorting it out so that it can be sent

to the cerebellum and medulla

thalamus

The old brain – the central core

• Link to the endocrine system

– Links the nervous system to the endocrine

system

– Governs release of other hormones in the body

– Homeostasis – internal balance - constant body

temperature and monitors the amount of

nutrients stored in the cells

• Important role in emotion, motivation and

stress

• Regulates hunger, thirst, self-protection, sex,

sleep and circadian rhythms

– Hypothalamic diseases can include appetite and

sleep disorders

hypothalamus

The old brain – the central core

thalamus hypothalamus

medulla pons cerebellum

Reticular formation

The limbic system self-preservation, eating, aggression, reproduction, learning, memory and

experience of pleasure, expression of emotions

reticular formation the brain’s guard. It arouses the

cerebral cortex to attend to new

stimulation and keeps the brain alert

even during sleep. https://www.youtube.com/watch?v=u76jBk59RFk

The limbic system self-preservation, eating, aggression, reproduction, learning, memory and

experience of pleasure, expression of emotions

The limbic system self-preservation, eating, aggression, reproduction, learning, memory and

experience of pleasure, expression of emotions

• Patients with epilepsy. In an attempt to stop their seizures

portions of the limbic system removed difficulty learning and

remembering new information.

• E.g. unable to remember where he lived, although he had resided at

the same address for eight years.

• E.g. even though the patient was able to carry on animated

conversations, he was unable, a few minutes later, to recall what

had been discussed.

• Forming new memories

• Brings cognitive elements to the processing

of emotional information

• Ties together sights, sounds and meaning

• Involved in spatial memory

• Alzheimers’ partially results from

hippocampus damage Hippocampus

The limbic system self-preservation, eating, aggression, reproduction, learning, memory and

experience of pleasure, expression of emotions

• Emotions, fear, aggression

• Emotional learning - Formation of memories

about emotionally charged events

– Injury from docile to beast and vice versa

• Feeding, drinking, sexual behavior

Amygdala

The limbic system self-preservation, eating, aggression, reproduction, learning, memory and

experience of pleasure, expression of emotions

Cerebral cortex – the new brain

sulci Thinking,

remembering, deciding Speaking

Sense of touch & senses

Cerebral cortex – the new brain

Motor, sensory, association areas

Cerebral cortex – motor area

Cerebral cortex – sensory area

3 regions • Body sensations (touch and pressure) • Sight • Sound

perceive touch & pressure in particular area of the body

Cerebral cortex – association areas

higher mental processes such as thinking, language, memory, and speech

make up a large portion of the cerebral cortex consist of the sections that are not directly involved in sensory processing or movement

control executive functions : planning, goal setting, judgment, and impulse control